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title: Mining Node.js Vulnerabilities via Object Dependence Graph and Query
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    title: Mining Node.js Vulnerabilities via Object Dependence Graph and Query
    author: Song Li, Mingqing Kang, Jianwei Hou, Yinzhi Cao
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  - Mingqing Kang
  - Jianwei Hou
  - Yinzhi Cao
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# Mining Node.js Vulnerabilities via Object Dependence Graph and Query

**Mining Node.js Vulnerabilities via Object Dependence Graph and Query** - Song Li, Mingqing Kang, Jianwei Hou, Yinzhi Cao, usenix.org.

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Mining Node.js Vulnerabilities via
  Object Dependence Graph and Query
     Song Li and Mingqing Kang, Johns Hopkins University;
Jianwei Hou, Johns Hopkins University/Renmin University of China;
               Yinzhi Cao, Johns Hopkins University
https://www.usenix.org/conference/usenixsecurity22/presentation/li-song




 This paper is included in the Proceedings of the
        31st USENIX Security Symposium.
             August 10–12, 2022 • Boston, MA, USA
                          978-1-939133-31-1




                                  Open access to the Proceedings of the
                                   31st USENIX Security Symposium is
                                         sponsored by USENIX.
Mining Node.js Vulnerabilities via Object Dependence Graph and Query

                           Song Li, Mingqing Kang, Jianwei Hou†∗, and Yinzhi Cao
                Johns Hopkins University, † Johns Hopkins University/Renmin University of China



                              Abstract                                various program analysis-based approaches [1–3,8–14] target-
                                                                      ing individual vulnerability, such as command injection [1, 2]
   Node.js is a popular non-browser JavaScript platform that
                                                                      and prototype pollution [3]. However, despite their success,
provides useful but sometimes also vulnerable packages. On
                                                                      there is no general framework to detect all kinds of Node.js
one hand, prior works have proposed many program analysis-
                                                                      vulnerabilities.
based approaches to detect Node.js vulnerabilities, such as
command injection and prototype pollution, but they are spe-             One recent advance of vulnerability detection in languages
cific to individual vulnerability and do not generalize to a          other than JavaScript such as C/C++ and PHP is to build a
wide range of vulnerabilities on Node.js. On the other hand,          graph structure representing different properties of a target
prior works on C/C++ and PHP have proposed graph query-               program and perform graph queries to mine vulnerabilities.
based approaches, such as Code Property Graph (CPG), to               For example, researchers proposed a particular graph struc-
efficiently mine vulnerabilities, but they are not directly ap-       ture, called Code Property Graph (CPG), which combines
plicable to JavaScript due to the language’s extensive use of         Abstract Syntax Tree (AST), Control Flow Graph (CFG), and
dynamic features.                                                     Program Dependence Graph (PDG). CPG is demonstrated
                                                                      to be effective in mining many types of vulnerabilities in
   In the paper, we propose flow- and context-sensitive static
                                                                      C/C++ [15] and PHP [16]. However, CPG does not model
analysis with hybrid branch-sensitivity and points-to infor-
                                                                      object relations, such as object lookups based on prototype
mation to generate a novel graph structure, called Object De-
                                                                      chain and this object lookup especially with a bind call.
pendence Graph (ODG), using abstract interpretation. ODG
                                                                      Therefore, it cannot model and detect popular object-based
represents JavaScript objects as nodes and their relations
                                                                      JavaScript vulnerabilities, such as prototype pollution [3] and
with Abstract Syntax Tree (AST) as edges, and accepts graph
                                                                      internal property tampering [5–7].
queries—especially on object lookups and definitions—for
detecting Node.js vulnerabilities.                                       At the same time, prior static JavaScript analysis works [1,
                                                                      10–12, 17] model objects and their relations via abstract in-
   We implemented an open-source prototype system, called
                                                                      terpretation [18] together with an online data structure, such
ODG EN, to generate ODG for Node.js programs via abstract
                                                                      as a lattice. However, prior abstract interpretations face two
interpretation and detect vulnerabilities. Our evaluation of
                                                                      major challenges. First, previous data structures are unsuit-
recent Node.js vulnerabilities shows that ODG together with
                                                                      able for offline (i.e., post abstract interpretation) detections
AST and Control Flow Graph (CFG) is capable of modeling
                                                                      of a variety of vulnerabilities—in other words, their target
13 out of 16 vulnerability types. We applied ODG EN to de-
                                                                      is a specific type of vulnerability. The reason is that object
tect six types of vulnerabilities using graph queries: ODG EN
                                                                      information in these structures keeps changing during abstract
correctly reported 180 zero-day vulnerabilities, among which
                                                                      interpretation. Thus, vulnerability-related object information
we have received 70 Common Vulnerabilities and Exposures
                                                                      is likely overwritten and lost in the final state. Second, ex-
(CVE) identifiers so far.
                                                                      isting JavaScript analysis—in terms of branch sensitivity—
1    Introduction                                                     interprets all branches either in sequence, which compromises
                                                                      accuracy, or in parallel, which compromises scalability. Both
Node.js is a popular JavaScript runtime environment that exe-
                                                                      cases lead to many false negatives: the former due to reduced
cutes JavaScript code outside web browsers such as being a
                                                                      detection capability and the latter due to excessive number of
web server to serve the client. Node.js ecosystem including
                                                                      objects.
millions of NPM packages is known to be vulnerable to a
variety of vulnerabilities, such as command injection [1, 2],            In this paper, we propose flow- and context-sensitive static
prototype pollution [3], path traversal [4], and internal prop-       analysis with hybrid branch-sensitivity and points-to infor-
erty tampering [5–7]. In the past, researchers have proposed          mation to generate a novel graph structure, called Object De-
                                                                      pendence Graph (ODG), using abstract interpretation. ODG
    ∗ The author contributes to the paper when she is visiting JHU.   accepts graph queries for the offline detection of a wide range



USENIX Association                                                                        31st USENIX Security Symposium         143
of Node.js vulnerabilities. The key insight of ODG is to rep-        1 function Func () {};
resent JavaScript objects as nodes and the relations among           2 Func . prototype .x=" ab ";
                                                                     3 myFunc = new Func ;
objects and between objects and AST nodes as edges. Specif-          4 if ( source1 )
ically, ODG includes fine-grained data dependencies between          5   myFunc [ source2 ]= myFunc .x+ source1 ; // internal
                                                                               property tampering
objects, thus helping taint-style vulnerability detection such as    6 sink ( myFunc .x); // taint - style vulnerability like
command injection. At the same time, ODG is also integrated                 command injection

with CPG, or particularly Abstract Syntax Tree (AST) of CPG,                        Figure 1: An exemplary code.
to represent and preserve all object definitions and lookups
(e.g., these via the prototype chain) in abstract interpretation    2.1   A Motivating Example
for the offline detection of object-related vulnerabilities such
as internal property tampering and prototype pollution.             Figure 1 shows a simple exemplary code with only six lines
                                                                    in motivating the use of ODG in vulnerability detection. Both
   We build a prototype system, called ODG EN, to generate
                                                                    source1 and source2 are controllable by an adversary and
ODG during abstract interpretation. Specifically, ODG EN
                                                                    sink is a sink function, such as exec in command injection.
starts from entry points and follows AST node sequence to
                                                                    The code has two vulnerabilities:
define and lookup objects for each AST node under abstract
scopes. Then, ODG EN records object definitions and lookups         • Internal Property Tampering [5–7]. This vulnerability is
as part of ODG, which are also used to generates CFG (if an           triggered when source2 is "__proto__". Because the pro-
object lookup is related to functions) and object-level data de-      totype chain of myFunc is overwritten at Line 5, the inter-
pendencies (if an object definition is derived from another ob-       nal property x of myFunc is tampered. Specifically, when
ject). ODG EN is hybrid branch-sensitive because the default          the code tries to access myFunc.x at Line 6, the object
of ODG EN is to abstractly interpret all branches in parallel,        lookup in the property x fails as the prototype chain to
but ODG EN switches back to sequential branch interpreta-             Func.prototype is broken. This vulnerability may lead
tion for a function if the number of object nodes explodes.           to a consequence like Denial of Service (e.g., the execution
ODG EN has points-to information because different aliases            of Line 6 fails) or privilege escalation (e.g., if myFunc.x is
of an objects point to the same object node in ODG.                   used later as part of an authentication).
   To demonstrate the effectiveness of ODG EN, we studied all       • Taint-style Vulnerability (e.g., command injection [1, 2]).
recent Node.js vulnerabilities in the CVE database and mod-           This vulnerability is triggered when source2 is "x". The
eled them with graph queries to ODG together with existing            code will then create a new property x under myFunc di-
graph-based code representations. Our evaluation shows that           rectly with an adversary controllable value from source1.
13 out of 16 vulnerability categories can be successfully mod-        Next, when the code accesses myFunc.x at Line 6,
eled by graph queries to ODG+AST+CFG. We then evaluate                the object lookup goes to myFunc directly instead of
ODG EN on real-world Node.js packages. The results show               Func.prototype, leading to a possible injection.
that ODG EN is able to detect 43 application-level zero-day            What we learned from these two vulnerabilities is that the
vulnerabilities with 14 false positives and we also confirmed       key is the object lookup myFunc[source2] at Line 5. Differ-
137 package-level zero-day vulnerabilities with 84 false posi-      ent lookups lead to different vulnerabilities—which motivates
tive. We received 70 CVE identifiers for these vulnerabilities.     the design of ODG in modeling different object lookups in a
   We make the following contributions in the paper.                graph for vulnerability detection. Another interesting obser-
                                                                    vation worth noting is that the data dependencies are different
• We design a novel graph structure, called Object Depen-           for two vulnerability triggering conditions. In the case of in-
  dence Graph (ODG), to model JavaScript objects and their          ternal property tampering at Line 5, we do not have a dataflow
  relations to AST node in terms of definition and use.             dependency between Lines 2 and 6 and the lack of such a
• We design offline graph queries that match object-related         dependency leads to the vulnerability. By contrast, in the case
  patterns for a variety of Node.js vulnerabilities, particularly   of a taint-style vulnerability, we have a dataflow dependency
  internal property tampering and prototype pollution.              between Lines 5 and 6 (which does not exist before) and the
• We build a prototype, open-source system using abstract           existence of this dependency leads to the vulnerability.
  interpretation to generate ODG for Node.js packages.                 Figure 2 shows the object dependence graph (ODG) inte-
• Our evaluation of ODG EN on real-world NPM packages               grated with code property graph (CPG) of the code in Figure 1.
  reveals 43 application-level and 137 package-level zero-day       The top part of Figure 2 is CPG with AST, CFG and Program
  vulnerabilities (70 being assigned with CVE identifiers).         Dependence Graph (PDG) nodes and edges; the bottom part
                                                                    is ODG with object/name nodes, object lookup/definition
                                                                    edges to AST nodes (copied from top for clarity purpose),
2     Overview
                                                                    and property edges. Note that because ODG has object-level
In this section, we start from a motivating example and then        data dependencies, we do not need the statement-level data de-
describe the threat model in detecting Node.js vulnerabilities.     pendencies in PDG as part of CPG. We include these edges in



144    31st USENIX Security Symposium                                                                          USENIX Association
                                                                  Figure 4: Nodes and Edges related to Graph Query for Taint-
                                                                  style Vulnerability Detection.

                                                                  •  2 Property in 1 (prop) is controllable by an adversary.
                                                                    The query follows the object-level data dependencies to
Figure 2: Object Dependence Graph (ODG, Bottom) Inte-               determine whether source2 is controllable by an adversary.
grated with Code Property Graph (CPG, Top) of the Exem-             Therefore, the value of source2 can be __proto__.
plary Code in Figure 1. For readers’ convenience, we copied       • 3 Assigned value in 1 (value) is controllable by an
corresponding AST nodes from top to bottom and skipped              adversary. The query follows the object-level data depen-
several unimportant nodes and edges, such as __proto__ of           dencies to determine whether myFunc.x+source1 can be
many objects, the global object and many built-in objects.          controllable by an adversary.
                                                                  • 4 Object in 1 (obj) has a prototypical object and the
                                                                    prototypical object has a property. The query follows proto-
                                                                    type chain of the object myFunc to find the prototype object
                                                                    myFunc.__proto__, which has a property x.
                                                                  • 5 Property in 4 is used later in the control flow and
                                                                    has more than one possible lookup. The query follows
                                                                    the property x to find other uses of the object (myFunc.x
                                                                    at Line 6 of Figure 1) and ensures that it has a control
                                                                    dependency with the previous assignment.
                                                                  2.1.2   Query to Detect Taint-style Vulnerability
                                                                  The detection of a taint-style vulnerability using ODG can
Figure 3: Nodes and Edges related to Graph Query for Internal     be summarized as finding a data dependency between the
Property Tampering Detection.                                     source object and the argument object in the sink function.
                                                                  We extracted related edges from Figure 2 and show them in
the figure for the purpose of a comparison. We now describe       Figure 4.
how to detect these two vulnerabilities via graph queries and     •  1 AST Pattern matching for sink function (sink(arg)).
more importantly how ODG edges contribute to the detection.         The query finds a statement with a sink function invocation
2.1.1   Query to Detect Internal Property Tampering                 (i.e., sink(myFunc.x) at Line 6 of Figure 1).
We summarize the detection of this internal property tamper-      • 2 Object lookup for arg in 1 . The query finds the object
ing vulnerability using ODG as follows. From a high-level           node in ODG.
perspective, ODG EN finds an object assignment statement via      • 3 Data dependency for the object in 2 . The query follows
a property lookup, which is then followed by another property       object-level data dependency edges to determine whether
lookup statement. Both the lookup and the assigned values           the sink function argument can be influenced by a source.
in the first statement are controllable by an adversary so that   • 4 AST Node for the source in 3 . The query follows
the prototype chain of the object can be tampered. Then, the        object lookup edges to find the AST node for the source.
property lookup in the second statement needs to have the           Note that the handling of myFunc[source2] is implicit in
tampered prototype chain involved. We extract related edges       the detection of this taint-style vulnerability. During ODG
from Figure 2, show them in Figure 3 and describe below.          construction, ODG EN creates a so-called wildcard object
• 1       AST pattern matching (obj[prop]=value).                 with a property ∗ to represent myFunc[source2] for all kinds
   The query finds an assignment statement with                   of possibilities. Then, myFunc.x can be resolved via two
   a property lookup via AST edges, which is                      ways: one to Func.prototype.x and the other as myFunc.*.
   myFunc[source2]=myFunc.x+source1 at Line 5 of                  Therefore, our query can find an object-level data dependency
   Figure 1.                                                      between myFunc.* and source1.



USENIX Association                                                                    31st USENIX Security Symposium       145
2.2     Threat Model                                                      Table 1: Nodes, Edges, and Operations of ODG
                                                                   Name                       Description
In this subsection, we describe the threat model of vulnerabil-    Nodes (N)                  A set of ODG nodes
ities in scope of ODG EN. ODG EN considers all JavaScript-         Object node (o ∈ No )      An object created in the abstract interpretation.
                                                                   Scope node (s ∈ Ns )       An abstract interpretation scope.
level Node.js vulnerabilities but excludes low-level ones, such    Variable node (v ∈ Nv )    A variable under a scope or a property under an object.
as those related to the V8 engine. Specifically, such vulnera-     AST node (a ∈ Na )         An abstract syntax tree node.
                                                                   Edges (E)                  A set of ODG edges
bilities can be categorized as two types: (i) application-level    Object def. (o →
                                                                                     s
                                                                                    − a)      The AST node (a) defining the object o under scope s.
and (ii) package-level. We now describe these two in details.      AST-obj lookup (a →
                                                                                         s
                                                                                        − o)  The object (o) used by the AST node (a) under s.
                                                                   Scope hierarchy (s → s)    A parent-child scope relation.
2.2.1    Application-level Vulnerabilities                         Variable lookup (s → v)    A variable v is defined under a scope s.
                                                                                       Br
                                                                   Var-obj lookup (v −→ o)    An object o that v points to with branch tags Br.
An application-level vulnerability assumes that an adversary       Property lookup (o → v)    A property v of an object o.
has some controls over contents in network connection, e.g.,       Data dependency (o → o)    Data dependency between two objects.
                                                                   Control dependency (a → a) Control dependency between two AST nodes.
an HTTP request or a response, because the application is          Procedures (P)             All the ODG-related operations
communicating with a malicious party. The detailed capa-           ChildEdgeType
                                                                        parentNode            Getting the child node of parentNode with EdgeType
bility of the adversary also depends on the semantics of the       AddEdgeEdgeType
                                                                                 p            Adding an edge from src node to dst node with
                                                                              src→
                                                                                 − dst        EdgeType and a property being either branch tags (Br)
application. We now describe two concrete senarios:                                           or a scope (s)
• Adversary-controlled network request to a vulnerable             GetEdgeEdgeType
                                                                             src              Getting all the edges start from src node with
                                                                                              EdgeType
  server. Say the application is a web server serving web con-     AddNodea   NodeType
                                                                                              Adding a node from a with NodeType
  tents to clients. An adversary can send HTTP requests with       AddObjObjType
                                                                           a                  Adding an object node from a with ObjType in typeof
                                                                                              list and linking prototypical objects
  malicious contents to the server and trigger a vulnerability.    LkupVarsBr (n)             Looking up a variable node under the scope (s) with
  Consider rollup-plugin-serve, which has a path traver-                     s
                                                                                              branch tags (Br) and name n
                                                                   LkupObjBr (n)              Looking up object nodes under scope (s) with branch
  sal vulnerability (CVE-2020-7684) found by ODG EN. The                                                                             Br
                                                                                              tags (Br) and name (n), i.e., {Child v−→o s }
  vulnerable code reads a file using readFile via an arbi-                                                                        LkupVarBr (n)

  trary path provided by the client without sanitization, i.e.,
  the filePath value eventually comes from the request             as mqtt-growl a mqtt monitor based on growl, by making
  object controllable by a possible adversary.                     them vulnerable as well.
• Adversary-controlled network response to a vulnerable               Other than the aforementioned application- vs. package-
  client. Say the application is at client-side talking with       level, we further classify Node.js vulnerabilities into two cat-
  servers. An adversary, i.e., a malicious server, can send        egories based on the vulnerability location, i.e., directly vul-
  HTTP responses with malicious contents to the application        nerable where the package itself is vulnerable, and indirectly
  and trigger a vulnerability. Let us take a real-world, client-   vulnerable where an imported package is vulnerable.
  side github notification system, called github-growl, for
                                                                   3     Object Dependence Graph
  example. github-growl gives an alert at the client side if
  a github issue is posted to a subscribed github repository.      In this section, we describe the definition of Object Depen-
  An adversary can post an issue with a crafted title with OS      dence Graph (ODG) and the operational semantics of the ab-
  commands and trigger the command injection vulnerability         stract interpretation and the procedure of constructing ODG.
  in github-growl.                                                 3.1    Definitions
2.2.2    Package-level Vulnerabilities                             In this section, we define an Object Dependence Graph (ODG)
Packages in Node.js are libraries that are imported by other       as a representation, using graph notation, of all the JavaScript
packages or applications. Package-level vulnerabilities as-        objects, variables and scopes generated during abstract inter-
sume that an adversary can control inputs to a vulnerable          pretation as nodes and their relations as edges. These edges
package (i.e., those accessible via module.exports), thus          include object and AST relations (such as object definition
triggering the vulnerability. It is worth noting that package-     and object lookup) and object relations (such as object prop-
level vulnerabilities are not stand-alone and have to be com-      erty and object-level data dependency).
bined with applications for a possible exploitation.                  Table 1 summarizes different ODG nodes and edges. Ob-
   The reason that Node.js community considers package-            jects, variables, scopes and AST are all represented as nodes
level vulnerabilities—which are demonstrated in both aca-          and their relations as edges. We start from AST-related edges:
demic works [1, 2] and many prior CVEs [5, 19, 20]—are             object definition and AST-obj lookup. The former is used to
that one package-level vulnerability may affect many applica-      locate the AST node where the object is defined when the
tions if the inputs to the package are not correctly sanitized.    object is used later. These types of edges are unique to one
Take the previous github-growl for example. The applica-           object node because an object is only defined once. The latter
tion itself is not vulnerable, but the vulnerability lies in an    is used to reproduce object lookups in abstract interpretation.
imported package called growl (CVE-2017-16042). In fact,           One AST node may have multiple AST-obj lookup edges be-
the vulnerable package also affects other applications, such       cause the AST node can be abstractly interpreted for multiple



146     31st USENIX Security Symposium                                                                                   USENIX Association
times in a for loop or a recursive call.                            of a statement are abstractly interpreted, ODG EN merges all
   We then describe edges between objects, variables, and           the objects and nodes from different branches based on the
scopes. Note that we skipped branch tags (introduced later          tags for continued abstract interpretation. (ii) ODG EN sequen-
in Section 3.2) for a simple explanation. First, the combina-       tially performs abstract interpretation for all the branches in
tion of s → s, s → v, v → o, and o → v edges can be used to         the branch-insensitive mode, i.e., the objects and edges cre-
resolve a statement like obj.prop during abstract interpreta-       ated in later branches will overwrite those created in earlier
tion. ODG EN first looks up obj under current scope using           branches. The default mode is branch sensitive, but ODG EN
s → v and then follows the scope chain using s → v to find          will switch to branch insensitive if the number of objects ex-
obj if the lookup under current scope fails. Once the variable      plodes, i.e., exceeding a certain number (e.g., 10k), for a given
is found, ODG EN follows v → o to find the object node and          function.
then o → v to find the prop. Then, o → o indicates the latter          Third, we describe function definition in Figure 5. ODG EN
object has a data dependency on the former. For example,            adds a variable node if the function is not defined in an anony-
the object that myFunc[source2] points to at Line 5 of Fig-         mous closure, creates an object node and edges between the
ure 1 has an object-level data dependency on both objects that      object and the variable nodes, and then handles edges related
myFunc.x and source1 point to.                                      to prototypes.
   Next, we describe how ODG models points-to information              Fourth, we describe function calls in Figure 5, which has
via v → o edges. Say two variables a and b and an object            two phase: pre-call and call. In the pre-call phase, ODG EN
property obj.v point to the same object. There is only one          looks up the function object and creates corresponding ob-
object node in ODG representing this object and three v → o         ject and control-flow edges. Then, in the call phase, ODG EN
edges from a, b and obj.v to the object node. Therefore, all        handles all the parameters, changes the current scope and
three object lookups will resolve to the same object node           this point, and then jumps to the AST node following a
during abstract interpretation.                                     call edge. Finally, in the return statement, ODG EN handles
                                                                    return objects and creates corresponding dataflow edges. Be-
3.2   Operational Semantics                                         cause ODG EN handles function calls using the current scope
In this subsection, we describe our abstract interpretation and     and returns to the exact call site, ODG EN is considered as a
the construction of ODG using operational semantics shown           context-sensitive approach.
in Figure 5. From a high level, ODG EN abstractly interprets           Lastly, we describe loops in Figure 5. ODG EN abstractly
each AST node (a) based on the statement (e), generates nodes       interprets a loop (and a recursive call) extensively until no
(N) and edges (E) for ODG, and then follows control-flow            more new objects outside the loop (or recursive call) are being
edges (which are generated during abstract interpretation)          looked-up. ODG EN also sets up a minimum and a maximum
to the next AST node. During the abstract interpretation of         limit for loops (and recursive calls).
each AST node, the state of ODG EN is represented as a tuple        4     ODG Queries for Node.js Vulnerabilities
ρ = (N, E, s, Br), where N is all the ODG nodes, E is all the
ODG edges, s is the current scope node, and Br ⊆ Sbr is a set       In this section, we describe graph queries to ODG for all
of branch tags that represents the current conditional branch       kinds of Node.js vulnerabilities. We first present how to model
in the branch-sensitive mode. Each branch tag is a unique           queries as several types of graph traversals in Section 4.1 and
identifier representing the current conditional branch.             then describe how to represent all kinds of vulnerabilities via
   Now, we describe the operational semantics of the abstract       those graph traversals in Section 4.2.
interpretation of different statements in Figure 5. First, we       4.1   Graph Traversals
start from the definition of either a variable or an object prop-
                                                                    A graph traversal, as defined in the CPG paper [15], is a
erty in Figure 5. ODG EN attempts to look up the variable or
                                                                    function T : P(V ) → P(V ) that maps a set of nodes to another
the property from ODG. If the look-up fails, ODG EN creates
                                                                    set of nodes on top of ODG, where V is a set of ODG nodes
new variable and object nodes and links corresponding nodes
                                                                    and P is the power set of V . There are multiple operations
via edges; if the look-up succeeds, ODG EN reuses existing
                                                                    that can be performed on T :
variable nodes but creates new edges for these nodes.
   Second, we describe branching statements (i.e., IF and           • A function composition ◦. Two graph traversals T0 and T1
SWITCH in Figure 5). ODG EN first tries to determine the              on V can be chained together by T1 ◦ T0 (V ).
                                                                    • A function intersection . The results of two
                                                                                             T
value of the branching condition and chooses correspond-                                                          T
                                                                                                                    graph traver-
ing branch(es). If the branching condition value cannot be            sal T0 and T1 on V can be intersected by T0 T1 (V ).
                                                                    • A function union . The results of two graph traversal T0
                                                                                        S
determined, the operational semantics depends on branch                                                 S
sensitivity. (i) ODG EN creates a unique branching tag for            and T1 on V can be unioned by T0 T1 (V ).
each branch in the branch-sensitive mode and attaches the             By those three simple operations, we can break a
branching tag with all the nodes and edges created during the       complex graph traversal into multiple basic traversal
abstract interpretation of each branch. When all the branches       components shown in Table 2. These basic traversals



USENIX Association                                                                      31st USENIX Security Symposium          147
                                                     ρ ⇒ (N, E, s, Br)
                                                                             s                                      ( VARIABLE )
                         s (x), = ∅ then (N, E, s, Br) else (N, E ∪ {AddEdgea→
  (x, a, ρ) ⇒ i f LkupVar∅                                                   − o where ∀o0 ∈ LkupOb js (a)}, s, Br)
                                                                             s                       Br
                                                                            x→
                                                                             − o0
                                                                                                                      s0 := s (BLOCK_SCOPE)                                                                                                       let/const
                                                       ρ ⇒ (N, E, s, Br)                                             0
                (let/var/const/∅ x, a, ρ) ⇒ (N ∪ Na := {AddNodevar      }, E ∪ {AddEdges→v , ∀n ∈ N }, s, Br) where   s := GLOBAL_SCOPE                                                                                                           ∅         ( VARIABLE DEF )
                                                                 a.name                 0
                                                                                       s →na   a   a
                                                                                                                      s0 := upper FUNC/FILE_SCOPE                                                                                                 var
                                                                              ρ ⇒ (N, E, s, Br), (x, a.x, ρ) ⇒ (Nx , Ex , sx , Brx ), (p, a.p, ρ) ⇒ (N p , E p , s p , Br p )
                                                                                                                                       o→v
                                                                                (Nx ∪ {pov (0), ∀pov ∈ Pov }, Ex ∪ {AddEdge pov (0)→pov (1) , ∀pov ∈ Pov }, s, Br)                                                       i f on = 0/
                                                           (x[p]/x.const, ρ) ⇒                              s
                                                                                  (Nx , Ex ∪ {AddEdgea→    − o , ∀n ∈ N }, s, Br)
                                                                                                            s      o       o                                                                                              otherwise
                                                                                                          a→
                                                                                                           − no
                                                                                                       s                          s                                                                              s                     s
                                           ox
                           No := {LkupOb jBr                             a→
                                                                           − o , ∀o ∈ Child a→
                                                (o p .name), ∀o p ∈ Childa.p                 −o                                                    Pov := {(AddNodevar    0      0       a→
                                                                                                                                                                                          −o    0      a→
                                                                                                                                                                                                        −o
                                              x                                    x       a.x }                                                                   p0 , o ), ∀o ∈ Childa.x , ∀p ∈ Childa.p }                                        x[p]
                     where                                              s                                                                                                                    s                                                                  ( PROPERTY )
                                           ox
                            No := {LkupOb jBr            ∀o   ∈       a→
                                                                       − o}                                                                        Pov := {(AddNodevar      0      0      a→
                                                                                                                                                                                           −o
                                              x
                                                (const),    x   Childa.x                                                                                           const , o ), ∀o ∈ Childa.x }                                                     x.const
                                                                                                                                                                                                                      s                       s
                                                                                                                                                                               ∗                a→
                                                                                                                                                                                                 −o              a→
                                                                                                                                                                                                                  −o
                                                                                                                                                              Nnew := {AddOb ja , ∀o1 ∈ Childa.x1 , ∀o2 ∈ Childa.x2 }
           ρ ⇒ (N, E, s, Br), (x1 , a.x1 , ρ) ⇒ (Nx1 , Ex1 , sx1 , Brx1 ), (x2 , a.x2 , ρ) ⇒ (Nx2 , Ex2 , sx2 , Brx2 )                                                                      0           0        a→
                                                                                                                                                                                                                    s
                                                                                                                                                                                                                  − o ∪Child a→
                                                                                                                                                                                                                               s
                                                                                                                                                                                                                              −o
                                                                                                                       where                                   Edep := {AddEdgeo→o
                                                                                                                                                                                 u0 →o0 , ∀o ∈ Nnew , ∀u ∈ {Childa.x        a.x }}
                                                                                                                                                                                                                                   ( BINARY OP )
                    (x1 op x2 , a, ρ) ⇒ (Nx1 ∪ Nx2 ∪ Nnew , Ex1 ∪ Ex2 ∪ Edep ∪ Ede f , s, Br)                                                                                                                                                 1                 2

                                                                                                                                                                 Ede f := {AddEdgeo→a       0
                                                                                                                                                                                  o0 →a , ∀o ∈ Nnew }

                         ρ ⇒ (N, E, s, Br), (k1 , a.k1 , ρ) ⇒ (Nk1 , Ek1 , sk1 , Brk1 ), (v1 , a.v1 , ρ) ⇒ (Nv1 , Ev1 , sv1 , Brv1 ), . . . , (kn , a.kn , ρ) ⇒ (Nkn , Ekn , skn , Brkn ), (vn , a.vn , ρ) ⇒ (Nvn , Evn , svn , Brvn )
                                                                                                                                                           n                n                n               n                                             br
             ({k1 : v1 , . . . , kn : vn }, a, ρ) ⇒ (Oa := {AddOb ja∗ } ∪ {nvi := AddNodevar
                                                                                         a.ki , ∀i ∈ {i, . . . , n}} ∪ {                                       Nki } ∪ {          Nvi }, {       Eki } ∪ {        Evi } ∪ Eov ∪ Evo ∪ {AddEdgea−
                                                                                                                                                                                                                                               →o , ∀oa ∈ O }, s, Br)
                                                                                                                                                           S                S                S               S
                                                                                                                                                                                                                                               Br          a
                                                                                                                                                         i=1               i=1           i=1                i=1                               a−
                                                                                                                                                                                                                                               →oa
                                                                 br
                                Evo := {AddEdgev−  →o               , ∀i ∈ {1, . . . , n}}                                                                  ρ ⇒ (N, E, s, Br)
                      ,where                          Br
                                                  nvi −
                                                      →Childa.v −s o
                                                               a→                           (O BJECT L ITERAL )                                                  s                                                         ( THIS )
                                                                                                                  (this, a, ρ) ⇒ (N, E ∪ {AddEdgea→             − o where ∀o0 ∈ LkupOb js (”this”)}, s, Br)
                                                                 i
                                  Eov := {AddEdgeo→v
                                                  ao→vi  , ∀i ∈  {1, . . . , n}}                                                                                 s                                   Br
                                                                                                                                                               a→
                                                                                                                                                                − o0
                                             ρ ⇒ (N, E, s, Br)                                                                      (B pre , a, ρ) ⇒ ρB pre , (S1 , ρB pre ) ⇒ ρ1 , . . . , (Sn , ρn−1 ) ⇒ ρn
                                                       scope                                       ( PRE BLOCK )                                                                                                              ( BLOCK )
                (B pre , a, ρ) ⇒ (N ∪ {as := AddNodea }, E ∪ {AddEdges→s           s→as }, as, Br)               (S1 , . . . , Sn , ρ) ⇒ (Nρn , Eρn ∪ {AddEdgea→a        a.Si →a.Si+1 , ∀i ∈ {1, . . . , n − 1}}, sρ , Brρn )

                                                                      ρ ⇒ (N, E, s, Br), (let/var/const/∅ x, a.x, ρ) ⇒ (Nx , Ex , sx , Brx ), (e, a.e, ρ) ⇒ (Ne , Ee , se , Bre )
                                                                                                                                                                                 br                                            s
                                                                                                                                                                                                                                                  ( ASSIGN )
                                        (let/var/const/∅ x = e, ρ) ⇒ (Nx ∪ Ne , Ex ∪ Ee /{GetEdgev→o                      v−
                                                                                                                           →o                                                                                          a→
                                                                                                                                                                                                                        − o }, s, Br)
                                                                                                                                                                                                      where ∀o0 ∈ Childa.e
                                                                                                 LkupVars a.x } ∪ {AddEdge                                                         s a.x−    Br
                                                                                                                                                 ∅                          LkupVar∅    →o0
                                                                                               ρ ⇒ (N, E, s, Br), ( f , a. f , ρ) ⇒ (N f , E f , s f , Br f )
                                                                                                                                                 br                                                     s
                                                                                                                                                                                                                                                       ( FUNCTION DEF )
                       ( f unction f (p1 , . . . , pn ), a, ρ) ⇒ (N f ∪ {on := AddOb ja. f }, E f ∪ {AddEdgev−
                                                                                                             →o                                                                  } ∪ {AddEdgea→
                                                                                                                                                                                              − o } ∪ {AddEdgeo→a }, s , Br )
                                                                                                           f unc
                                                                                                                                                                    Br f                      s               on→a    f    f
                                                                                                                                                      s a. f .name−                          a→
                                                                                                                                                                                              − on
                                                                                                                                               LkupVar∅           −→on
                                                                                                                        ρ ⇒ (N, E, s, Br)
                                                                                                                                                       s                                        ( CLOSURE DEF )
                                                                                                                               }, E f ∪ {AddEdgea→    − o } ∪ {AddEdgeo→a }, s, Br)
                                                                                                                                         f unc
                                                     ( f unction (p1 , . . . , pn ), a, ρ) ⇒ (N f ∪ {on := AddOb j∅                                    s                          on→a
                                                                                                                                                     a→
                                                                                                                                                      − on
                                                     ρ ⇒ (N, E, s, Br), ( f , a. f , ρ) ⇒ (N f , E f , s f , Br f ), (a1 , a.a1 , ρ) ⇒ (Na1 , Ea1 , sa1 , Bra1 ), . . . , (an , a.an , ρ) ⇒ (Nan , Ean , san , Bran )
                                                                                                           n                  n                n                                 br
                                                                       ( f (a1 , . . . an ), a, ρ) ⇒ (           Nai ∪ Sc ∪                          Eai ∪ {AddEdges−
                                                                                                                                                                    →s , ∀s ∈ S } ∪ E ∪ E , S , Br)
                                                                                                           S                  S                S
                                                                                                                                      vnai ,                        br     c   c     call vo c
                                                                                                           i=1                i=1              i=1                 s−
                                                                                                                                                                    →sc
                                                                                                                                                                                                  s                                s
                       Psd := {(AddNodescope     , a0de f ), ∀a0de f ∈ ade f }, Sc := {psd [0], ∀psd ∈ Psd }, ade f := {Childoo→a              a→
                                                                                                                                                 − o }, E := {AddEdgea→
                                                                                                                                   , ∀o0 ∈ Childa.                                −a           , ∀psd ∈ Psd }
                                          a0de f                                                                                0                  f     call                      psd [0]
                                                                                                                                                                                 a−−−→ psd [1]
              where                                               sc                                                                                       br                                                  ( PRE CALL )
                        Pvo := {(sc , AddNodevar                a−→o                                                                                     v−→o              , ∀pvo ∈ Pvo , ∀p0vo [2] ∈ pvo [2]}
                                                 a.ai , Childa.ai ), ∀sc ∈ Sc , ∀i ∈ {1, . . . , n}}, vnai := {pvo [1], ∀pvo ∈ Pvo }, Evo := {AddEdge           Br
                                                                                                                                                         pvo [1]−
                                                                                                                                                                → p0vo [2]
                                                                                                                                                                                                                  B := {a0 .B, ∀a0 ∈ Childaa→a }
                                                                                                                                                                                                                                     s→v
                                                                                                                                                                                                                 Esv ; = {AddEdgesρ pc →ntv }
                                                     ρ ⇒ (N, E, s, Br), ( f (a1 , . . . an ), a pc , ρ) ⇒ ρ pc , (B, aB , ρ pc ) ⇒ ρB                                                                                                   br

                                                  (NρB , EρB , s, Br)                                                                                                                       Call
                                                                                                                                                                                                        , where   Evo := {AddEdgev−     →o } ( CALL , NEW )
                                                                                                                                                                                                                                            Br
                                                                                                                                                                                                                                      ntv − →nto
                 ( f (a1 , . . . an ), a, ρ) ⇒                               ob j                                                                                                                                                         s
                                                   (NρB ∪ {nto := AddOb ja } ∪ {ntv := AddNodevar               ”this” }, EρB ∪ Esv ∪ Evo ∪ Eres , s, Br)                                    New                  Eres := {AddEdgea→    −o }
                                                                                                                                                                                                                                          s
                                                                                                                                                                                                                                       a→
                                                                                                                                                                                                                                        − nto
                                                                            ρ0i f := (Ne , Ee , se , Bre ∪ new br(a.i f ))      (branch sensitive)
                   ρ ⇒ (N, E, s, Br), (e, a.e, ρ) ⇒ (Ne , Ee , se , Bre ), ρ0else := (Ne , Ee , se , Bre ∪ new br(a.else))      (branch sensitive)     , (Bi f , a.Bi f , ρ0i f ) ⇒ ρi f , (Belse , a.Belse , ρ0else ) ⇒ ρelse
                                                                              0          0
                                                                            ρelse := ρi f := (Ne , Ee , se , Bre )              (branch insensitive)
                                                                              a→a                                                                                                                                                    ( IF )
                                                 (Nρi f , Eρi f ∪ {AddEdgea→a.i f }, sρi f , Brρi f )                                      Ctrue = True                                             s                            s
          (i f (e){Bi f }else{Belse }, a, ρ) ⇒ (Nρelse , Eρelse ∪ {AddEdgea→a     a→a.else }, sρelse , Brρelse )                           C f alse = False where Ctrue = ∧{Childaaρ→              − o },C f alse = ∨{Child a→
                                                                                                                                                                                                    e
                                                                                                                                                                                                                                −o
                                                                                                                                                                                                                               aρe }
                                                 (Nρi f ∪ Nρelse , Eρi f ∪ Eρelse ∪ {AddEdgea→a                           a→a
                                                                                                   a→a.i f } ∪ {AddEdgea→a.else }, s, Br)  else
             (x = x + 1, a0 , ρ) ⇒ ρx+1 (x = x − 1, a0 , ρ) ⇒ ρx−1                             (x1 = x1 op x2 , a0 , ρ) ⇒ ρx1 op x2                                                 ρ ⇒ (N, E, s, Br)
                                                                                 ( INC / DEC )                                       ( ASSIGN OP )                                                                      s                ( CONST )
                 (x + +, a, ρ) ⇒ ρx+1               (x − −, a, ρ) ⇒ ρx−1                         (x1 aop x2 , a, ρ) ⇒ ρx1 op x2                       (c, a, ρ) ⇒ (N ∪ {ao := AddOb ja∗ }, E ∪ {AddEdgea→              − o }, s, Br)
                                                                                                                                                                                                                        s
                                                                                                                                                                                                                      a→
                                                                                                                                                                                                                       − ao
           (e1 , a.e1 , ρ) ⇒ (Ne1 , Ee1 , se1 , Bre1 ), . . . , (en , a.en , ρ) ⇒ (Nen , EEn , sen , Bren ),                        (Btry , a.Btry , ρ) ⇒ (Nt , Et , st , Brt ), (Bcatch , a.Bcatch , ρBtry ) ⇒ (Nc , Ec , sc , Brc )
                                                          n           n                                      ( EXPRESSION LIST )                                                                                                      ( TRY- CATCH )
                                                                                                                                                (try{Btry }catch{Bcatch }, a, ρ) ⇒ (Nt ∪ Nc , Et ∪ Ec , s, br)
                             (e1 , . . . , en , a, ρ) ⇒ ( Nei , Eei , sen , Bren )
                                                          S           S
                                                           i=1          i=1
                                                                                                                                                                           n (N , E , s , new br(e ) ∪ Br )                                (branch-sensitive)
                                                                                                                                                                                                           i
                (e1 , a.e1 , ρ) ⇒ ρe1 , (B1 , a.B1 , ρ0e1 ) ⇒ ρB1 , . . . , (en , a.en , ρ) ⇒ ρen , (Bn , a.Bn , ρ0en ) ⇒ ρBn where ρ0ei =
                                                                                                                                                                               ρe i   ρe i ρe i              ρe i
                                                                                                                                                                             (Nρei , Eρei , sρei , Brρei )                                 (branch-insensitive)
                                                                               n                  s                                                    n                    s
                                                                                                                                                                                                                                                                      ( SWITCH )
                          (switch e1 {B1 } . . . en {Bn }, a, ρ) ⇒ (                 {i f Childaaρ→
                                                                                                  − o = True then Nρ else ∅},                                {i f Childaaρ→
                                                                                                                                                                          − o = True then Eρ ∪ {AddEdgea→a } else ∅}, s, Br)
                                                                               S                                                                       S
                                                                                                  ei
                                                                                                                    Bi                                                    e  i
                                                                                                                                                                                            Bi         a→a.Bi
                                                                               i=1                                                                     i=1

                                            ρ ⇒ (N, E, s, Br), (e, a.e, ρ) ⇒ (Ne , Ee , se , Bre )                                              (e, a.e, ρ) ⇒ ρe , (B1 , a.B1 , ρe ) ⇒ ρB1 , (B2 , a.B2 , ρe ) ⇒ ρB2
                                                                s                                                s            ( RETURN )                                              s                                    (T ERNARY )
                   (return e, a, ρ) ⇒ (Ne , Ee ∪ {AddEdgea→    − o , where a0 = AST
                                                                  s
                                                                                                  0          a→−o
                                                                                        caller , o = Childa.e }, s, Br)                      (e : {B1 }?{B2 }, a, ρ) ⇒ i f Childa.ρ  a→
                                                                                                                                                                                      − o = True then ρB else ρB
                                                                                                                                                                                        e                     1          2
                                                             a0 →
                                                                − o0
                                                            ρ ⇒ (N, E, s, Br), (x1 , a.x1 , ρ) ⇒ (Nx1 , Ex1 , sx1 , Brx1 ), . . . , (xn , a.xn , ρ) ⇒ (Nxn , Exn , sxn , Brxn )
                                        n                                                                               n                                            br                             s
                                                                                                                                                                                                                                     ( ARRAY )
                                                               array
         ([x1 , . . . , xn ], a, ρ) ⇒ ( Nxi ∪ {ao := AddOb j∅ } ∪ {vi = AddNodevar                                         Exi ∪ {AddEdgeo→v                      v− →o , where ∀o ∈ Child a→      −o
                                                                                             i , ∀i ∈ {1, . . . , n}},                                                                           a.xi , ∀i ∈ {1, . . . , n}}, s, Br)
                                        S                                                                               S
                                                                                                                                                ao→vi , AddEdge Br                     i
                                       i=1                                                                             i=1                                        vi −→oi
                      ρ ⇒ (N, E, s, Br), (e, a.e, ρ) ⇒ ρe , (B, a.B, ρe ) ⇒ ρB           ρ ⇒ (N, E, s, Br), (e1 , a.e1 , ρ) ⇒ (ae1 , ρe1 ), (e2 , a.e2 , ρe1 ) ⇒ ρe2 , (B, a.e2 , ρe2 ) ⇒ ρB , (e3 , ρB ) ⇒ ρe3
                                                                               ( WHILE )                                                                                                                        ( FOR )
                           (while (e){B}, a, ρ) ⇒ (NρB , EρB , s, Br)                                                    ( f or(e1 ; e2 ; e3 ){B}, a, ρ) ⇒ (Nρe3 , Eρe3 , s, Br)
                                                                                   loop until ρB or ρe3 does not change or the number of looping reaches the threshold
                                                                           Figure 5: Operational Semantics for ODG Construction.
include object definition and use from AST (D EFob j and                                                                                                       AST pattern matching (M ATCH p , V UL A SGMTo1[o2]=o3 ,
U SEob j ), property lookups (P ROPname
                                   ob j and P ROTOTYPE x[y] ),                                                                                                 V UL A SGMTo1=o2[o3] , and A RGnf unc ) and control-flows
data-flows (U NSANITIZEDob j and U NSANITIZED S INKsink ),                                                                                                     (C TRnbe f ore/a f ter ).



148    31st USENIX Security Symposium                                                                                                                                                                                                                           USENIX Association
                                                                                               prototype chain. There are traditionally two pro-
Table 2: Basic Graph Traversals (edges are defined in Table 1)
 Traversal                    Description
                                                                                               totype pollution patterns: one through __proto__
 D EFob j                     Object Definition: (a1 = ob j) → o → a2 .                        (i.e., obj.__proto__.toString) and the other through
                                                           reverse
 U SEob j                     Object use: (a1 = ob j) → o −−−→ a2 .                            constructor (i.e., obj.constructor.prototype). We
 P ROPname                    Property Lookup: (a = ob j) → o1 → (v = name) → o2 .
      ob j
                              Prototype-related Property Lookup: (a0 = x) → o0 →
                                                                                               describe graph traversals for both patterns in Table 3: The
 P ROTOTYPEx[y]
                              {(vk = “__proto__”) −−→
                                                       Br k
                                                            ok }k>0,Brk+1 ⊂Brk → (v =
                                                                                               former has two vulnerable assignments before the target
                              y) → ok+1 , where {}k means repeating k times.                   and the latter has three.
 U NSANITIZEDob j             A Backward Unsanitized Dataflow traversal [15].
 U NSANITIZED S INKsink       A Forward Unsanitized Dataflow traversal, i.e., a re-        Injection Vulnerabilities Injection vulnerabilities allow
                              verse version of U NSANITIZEDob j .                          adversaries to execute arbitrary code via injections into a
 M ATCH p                     This Match Traversal finds an AST node p [15].
 V UL A SGMTo1[o2]=o3
                                                T
                              U NSANITIZEDo2 M ATCHo1[o2]=o3                               sink function via user inputs. Such vulnerabilities are de-
 V UL A SGMTo1=o2[o3]
                                                T
                              U NSANITIZEDo3 M ATCHo1=o2[o3]                               tected via finding a backward taint-flow from a sink to an
 A RGnf unc                   A traversal matches a function f unc and obtains its nth     adversary-controlled source and we model this taint-flow as
                              argument.
 C TRnbe f ore/a f ter        A traversal follows control flow edges either forward        U NSANITIZED ◦ A RG∗sink . The traversals for specific injection
                              (a f ter) or backward (be f ore).                            vulnerabilities are shown in Table 3.
   Table 3: Graph Traversals for Different Vulnerabilities                                 Improper File Access Improper file access allows an ad-
 Vulnerability             Graph Queries                                                   versary to either read or write files on the filesystem without
 Internal Property Tampering                                                               a proper permission. We model two example types of vulner-
                                               T o1[o5] ◦ (U SEo1 C TRa f ter ) ◦
                                                                     T
   Prototypical           P ROTOTYPE L OOKUP
                          (U NSANITIZEDo3 V UL A SGMTo1[o2]=o3 )                           abilities in Table 3.
                          V UL A SGMTo1=o4[o5]            ◦         D EFo1             ◦
   Direct                                      T
                          (U NSANITIZEDo3 V UL A SGMTo1[o2]=o3 )
                                                                                           • Path Traversal. Path (directory) traversal allows an adver-
 Prototype Pollution                                                                         sary to navigate through directories via ../ to access local
  __proto__               V UL A SGMTo1=o4[o5] T          ◦         D EFo1             ◦     files. We model it from a web server creation, to the call-
                          (U NSANITIZEDo3 V UL A SGMTo1[o2]=o3 )
                          V UL A SGMTo4=o6[o7] ◦ D EF                                        back of HTTP(s) request, then to a file read (ReadFile),
   constructor                                          To4 ◦ V UL A SGMTo1=o4[o5] ◦
                          D EFo1 ◦ (U NSANITIZEDo3 V UL A SGMTo1[o2]=o3 )                    and finally to the HTTP(s) response in Table 3.
 Injection-related Vulnerabilities
  Command injection                                1
                          U NSANITIZED ◦ A RGChild_process.exec
                                                                                           • Arbitrary File Write. Arbitrary file read allows an adversary
  Arbitrary code exe.     U NSANITIZED ◦ A RG1eval                                           to write to arbitrary files due to improper input validation.
  SQL injection           U NSANITIZED ◦ A RG1connection.query                               We model the vulnerability from a web server creation, to
  Reflected XSS           U NSANITIZED ◦ A RG1response.write
                                                                                             the callback, and then to the write to the file system in
                                                      ◦         (A RG1connection.query
                                                                                       S
                          U NSANITIZED
  Stored XSS                     1                                     1                     Table 3.
                          (A RGconnection.query ◦ U NSANITIZED ◦ A RGresponse.write ))
 Improper File Access
                          (U NSANITIZED S INK P ROPwrite
                                                                T
                                                                  C TRa f ter )        ◦   5     Implementation
                                                      A RG2callback
  Path traversal                                                                           We implemented an open-source prototype of ODG EN at this
                                                                                      ◦
                                                            T
                           (U NSANITIZED S INKReadFile C TRa f ter )
                           P ROP∗ ◦ ASRG1callback ◦ D EF A S callback                 ◦    repository (https://github.com/Song-Li/ODGen). The
                                1                2
                           (A RGCreateServer A RGCreateHtt pServer )
                                                              T
                           (U NSANITIZED S INK P ROPwriteFile C TRa f ter )           ◦
                                                                                           implementation has three major parts:
                                                       fs
  Arbitrary file write                                                                     • (i) ODG representation and query. The ODG together with
                           P ROP∗       ◦ S A RG1o1         ◦        D EF A S o1      ◦
                                1                2
                           (A RGCreateServer A RGCreateHtt pServer )                         AST and CFG is stored in memory and queried based on a
                                                                                             Python library, NetworkX (https://networkx.github.
4.2      Vulnerability Descriptions                                                          io/). We also store ODG with AST and CFG using pickle,
In this subsection, we describe how to use graph traversals to                               a Python object serialization method, to the harddisk for
represent four big categories of vulnerabilities in Table 3.                                 future queries. Note that we adopt NetworkX instead of
                                                                                             a graph database like Neo4j, because we find that an in-
Object-related Vulnerabilities We describe graph traver-
                                                                                             memory graph management is more efficient than a graph
sals of two object-related vulnerability:
                                                                                             database stored on the disk, especially during abstract in-
• Internal Property Tampering. Internal property tampering                                   terpretation.
  (IPT) [5–7] allows an adversary to alter an internal property,                           • (ii) JavaScript parser. The JavaScript parser is based on
  either under an object directly or a prototypical object, so                               Esprima (https://esprima.org) and we added imple-
  that future property lookups are affected. IPT has two                                     mentations to convert AST from Esprima to the standard
  main conditions: (i) a vulnerable assignment statement                                     format of CPG, i.e., those accepted by joern [15] and ph-
  controllable by an adversary, and (ii) a property lookup                                   pjoern [21]. Note that we adopt the standard format so that
  after (i). We list graph traversals of both prototypical and                               we can compare ODG with CPG in the evaluation.
  direct property tampering in Table 3 based on these two                                  • (iii) Abstract interpretation. We implemented a cus-
  conditions.                                                                                tomized abstract interpretation in Python and modeled pop-
• Prototype Pollution. Prototype pollution allows an                                         ular built-in functions via JavaScript. Our implementation
  adversary to alter a built-in function following the                                       includes popular AST features that are used by >5% of



USENIX Association                                                                                              31st USENIX Security Symposium        149
                                                                        the descriptions on CVE and snyk.io to understand the vulner-
Table 4: [RQ1] Vulnerability coverage of different code rep-
                                                                        ability category. Table 4 shows all 16 vulnerability categories
resentation for modeling vulnerability types in the CVE
                                                                        and corresponding # of CVEs in the database.
database between January 2019 and September 2020.
                                                 Code Representations
                                                                           Next, we follow the evaluation methodology adopted in
    Vulnerability type         # of CVE
                                            CPG∗ AST+ODG AST+CFG+ODG    the CPG paper [15] to manually analyze what code represen-
  Prototype pollution               71              (3)            3    tations are necessary in describing those vulnerability cate-
  Command injection                 67        3      3             3
  Cross Site Scripting (XSS)        60        3      3             3    gories in Node.js. In addition to the code presentations in
  Path (directory) traversal        32       (3)                   3    CPG, we add ODG and try to understand the capability of
  Arbitrary code execution          18        3      3             3
  Improper access control           14        3                    3    ODG in describing vulnerabilities. Note that the object-level
  Internal property tampering       11              (3)            3    data dependency is a more fine-grained version of statement-
  Denial of Service (DoS)           11
  Regex DoS (ReDoS)                  9                                  level data dependency in PDG, and thus we do not need to
  Design errors                      8                                  study PDG+ODG in the code representation.
  Information exposure               8        3         3     3
  Arbitrary file write               8       (3)              3            Table 4 shows the analysis results: ODG EN is able to
  SQL injection                      5        3         3     3         model 13 out of 16 vulnerability types, i.e., 302 out of 330
  SSRF                               4        3               3
  CSRF                               2        3               3         recent vulnerabilities. The rest vulnerability types are general
  Insecure HTTP                      2        3         3     3         Denial of Service, Regex Denial of Service (ReDoS), and bad
  Total                            330
 ∗
   : CPG = AST + CFG + PDG.                                             designs. ODG cannot model ReDoS because it is caused by a
 (3): It can be detected but with reduced capability.                   vulnerable regex rather than JavaScript; ODG cannot model
                                                                        many other DoS because some of them are caused by the event
    Node.js packages. Note that we set a timeout as 30 seconds          loop. Fortunately, Staicu et al. [22] and Davis et al. [23] either
    in practice of analyzing Node.js packages.                          detect or defend against DoS attacks. ODG cannot model
                                                                        vulnerabilities due to bad designs, e.g., incorrect validation
6      Evaluation                                                       of inputs—this is the same as the CPG paper, which leaves
In this section, we evaluate ODG EN by answering the follow-            design errors out of scope as well.
ing research questions.
                                                                        6.2   RQ2: Zero-day Node.js vulnerabilities
• RQ1: What are the recent Node.js vulnerability types and
   is ODG capable of modeling them?                                     In this research question, we evaluate the capability of
• RQ2: What is the capability of ODG EN in detecting zero-              ODG EN in detecting zero-day Node.js vulnerabilities both
   day vulnerabilities among a large number of real-world               at the application-level and the package-level as described in
   NPM packages?                                                        Section 2.2. Specifically, we crawled 300K NPM packages on
• RQ3: What are the False Positives (FPs) and False Nega-               February 25, 2020 and applied ODG EN with graph queries to
   tives (FNs) of ODG EN?                                               detect corresponding vulnerabilities. Our target vulnerability
                                                                        is selected from the top ones in Table 4; we also intentionally
• RQ4: What is the code coverage and performance overhead
                                                                        include those that are unique to JavaScript, such as prototype
   of the abstract interpretation?
                                                                        pollution and internal property tampering.
• RQ5: How will branch-sensitivity affect the vulnerability
   detection of ODG EN?                                                 Results. Table 5 (the “# reported” column) shows a list of
   We performed our experiments on a server with 192 GB                 vulnerabilities found by ODG EN. Due to time limit and the
= 6*32GB RDIMM 2666MT/s Dual Rank memory, Intel R                       extensive number of reported vulnerabilities, we manually
Xeon R E5-2690 v4 2.6GHz, 35M Cache, 9.60GT/s QPI,                      checked and exploited all the vulnerable applications and
Turbo, HT, 14C/28T (135W) Max Mem 2400MHz, and 4                        these vulnerable packages with >1,000 weekly downloads.
* 2TB 7.2K RPM SATA 6Gbps 3.5in Hot-plug Hard Drive.                    The “TP” column indicates that we can generate an exploit to
                                                                        compromise the package if deployed locally and the vulnera-
6.1      RQ1: Historical Node.js vulnerability coverage                 bility is not an intended functionality of the package, and the
In this subsection, we answer the research question on the              “FP” column that we fail to generate a working exploit or the
ODG’s capability in modeling real-world Node.js package                 vulnerability is an intended functionality of the package, e.g.,
vulnerabilities. We start from querying the central database            a package like shell-utils designed to execute arbitrary
maintained by the MITRE organization together with informa-             OS command. Lastly, the “# CVE” column is the total number
tion provided by the synk.io database for recent (i.e., January         of CVE identifiers that we obtained.
2019–September 2020) vulnerabilities of Node.js packages                   We first break down all the found vulnerabilities by
on NPM. In total, we retrieved 330 vulnerabilities of Node.js           application- vs. package-level in Table 5 . The number of
packages after excluding vulnerabilities of Node.js platforms           application-level vulnerabilities is relatively small compared
(e.g., those with underlying memory issues). We then manu-              with the one of package-level. This is because the total num-
ally go through the vulnerability by downloading the origi-             ber of Node.js standalone applications is also much smaller
nally vulnerable package and analyze the code together with             than the one of packages.



150       31st USENIX Security Symposium                                                                           USENIX Association
Table 5: [RQ2] A breakdown of zero-day vulnerabilities found             Table 6: Baseline Detectors (CI: Command Injection, ACE:
by ODG EN.                                                               Arbitrary Code Execution, PT: Path Traversal, PP: Prototype
                                #Reported #Checked TP FP #CVE            Pollution)
 Total                            2,964     264    180 84 70              Name           Type In-scope vuln. Original tool                  Our impl.∗ (LoC)
 App. vs. package breakdown                                               JSJoern        static     CI, ACE, PT       phpjoern [21]      260 (Java)+415 (Python)
 Application-level                57         57      43 14      6         NodeJsScan regex          CI, ACE, PT NodeJsScan [24]                    N/A
                                                                          JSTap-vul      static     CI, ACE, PT         JSTap [8]              134 (Python)
 Indirect Package-level            34         34      15 19      0        Synode-det     static     CI, ACE, PT        Synode [2]                74 (Java)
 Direct Package-level            2,873       173     122 51     64        PPFuzzer      dynamic          PP             Arteau [3]                 N/A
 Vulnerability type breakdown                                             Nodest         static       CI, ACE           Nodest [1]      288 (Java)+27 (Javascript)
 Path traversal                   109         40      30   10    6        Ensemble                     The combination of the above six detectors.
                                                                         ∗
 Command injection               1,253       108      80   28   52         : Because some tools are not for vulnerability detection, target another language or are
                                                                         close-sourced, we have to retrofit them for evaluation of vulnerability detection. Note
 Arbitrary code execution         183         17      14    3    8       that we keep their static analysis part integral.
 Internal property tampering      910         46      24   22    0
 Prototype pollution              492         36      19   17    4       Table 7: [RQ3-FP] FP/(FP+TP) of general-purpose static de-
 Cross Site Scripting (XSS)        17         17      13    4   0
                                                                         tectors.
(a) Vulnerable code:                                                            JSJoern                     JSTap-vul                   ODGen
 1 module . exports = function deparam ( params ) {                             15/(15+5) = 75%          16/(16+4) = 80%          84/(84+180) = 32%
 2 var obj = {};
 3 params . replace (/\+/ g , ’ ’). split ( ’& ’). forEach (             deparam takes a parameterized query string and converts the
              function(v){
 4         var param = v. split ( ’= ’) , key = decodeURIComponent (     string back into an object.
                param [0]) , cur = obj , i = 0;
 5         ... // convert string " key " to array " keys ",
                                                                            deparam is vulnerable to prototype pollution as shown in
                e.g., ’a[b ][ c]’ -> [’a ’, ’b ’, ’c ’]                  the simplified code of Figure 6 (a) and the exploit in Fig-
 6         var keys_last = keys . length - 1;
 7         if ( param . length === 2 ) {
                                                                         ure 6 (b). Specifically, when deparam constructs an object, it
 8           val = decodeURIComponent ( param [1] );                     does not check whether a property lookup follows the proto-
 9           for ( ; i <= keys_last ; i ++ ) {
10             key = keys [i ];
                                                                         type chain (Line 14 of Figure 6 (a)). Therefore, an adversary
11             if (i < keys_last ) {                                     can pollute Object.prototype.toString using the code at
12               cur = cur [ key ] || ( keys [i +1] && isNaN ( keys [i
                       +1] ) ? {} : []) ;
                                                                         Line 2 of Figure 6 (b): When the for-loop at Line 9 is executed
13             } else {                                                  for the second time, toString is polluted at Line 14.
14               cur = cur [ key ] = val ; // vulnerable location
15             }                                                            Since one popular use of deparam is to parse the query
16           }                                                           string of an URL, it will lead to application-level vulnerabili-
17         }
18      }) ;                                                             ties. We search the use of deparam on github and find a real-
19      return obj ;                                                     world vulnerable web application, called PDX-Parks (https:
20 };
                                                                         //github.com/meandavejustice/pdx-parks), which al-
(b) Exploit:                                                             lows a user to search for nearby parks with given latitude
 1      var deparam = require (" deparam ");
                                                                         and longitude. PDX-Parks adopts deparam to decompose a
 2      var payload = "a[ __proto__ ][ toString ]=123 ";                 query string into an object, thus being vulnerable. Specifi-
 3      deparam ( payload );
                                                                         cally, we deployed the website locally and exploited the site
 4      console . log ({}. toString )
                                                                         via http://localhost/parks?[__proto__][toString]
Figure 6: [RQ2] A package-level prototype pollution in de-               =123, which leads to a Denial-of-Service (DoS) for all legiti-
param and the exploit code (It leads to an application-level             mate requests. The reason is that PDX-Parks adopts express,
vulnerability in PDX-Parks, a park search application).                  which needs a correct toString function.
   We then break down these vulnerabilities by their types in            6.3     RQ3: FP and FN
Table 5. The number of command injection vulnerabilities is
the most among all the vulnerability types as Node.js is com-            In this subsection, we answer the research question of the
monly used as a client- or server-side utility application to            false positives (FPs) and false negatives (FNs) of ODG EN.
start OS applications. We also find many prototype pollution             Baseline Detectors. We now introduce several baseline
vulnerabilities as this is a relatively new type. The number             vulnerability detectors for the purpose of comparing with
of XSS vulnerabilties is small because our prototype imple-              ODG EN in Table 6 including the technique type (static vs.
mentation only models the simple web server provided by the              dynamic vs. regex) and their in-scope vulnerabilities. Because
Node.js framework but not those advanced web frameworks.                 we modified several existing JavaScript static analysis tools,
                                                                         such as phpjoern, Synode, and JSTap, to detect Node.js vul-
Case Study. In this part, we describe a popular Node.js
                                                                         nerabilities, we also make our modification open-source in
package, called deparam, which has two other variations
                                                                         the same URL as ODG EN.
on NPM, node-jquery-deparam and jquery-deparam. All
three packages provide reverse functions for the famous                  False Positives. In this part, we evaluate the false positives
jquery function $.param(), called deparam. The function                  (FPs) of ODG EN and compare it with two other general-



USENIX Association                                                                                    31st USENIX Security Symposium                         151
                                                                      1     // pixi -gl - core@1 .1.4
      Table 8: [RQ3-FP] A breakdown of FPs of ODG EN.                 2     function getUniformGroup ( nameTokens , uniform )
   Vulnerability               Unmodeled Unsolvable Intended          3     {
                                                                      4         var cur = uniform ;
                               function  constraints functionality    5         for (var i = 0; i < nameTokens . length - 1; i ++)
   Command injection                7         9            12         6         {
   Arbitrary code execution         1         1             1         7             var o = cur [ nameTokens [i ]] || { data :{}};
   Prototype pollution              7         8             2         8             cur [ nameTokens [i ]] = o;
   Path traversal                   0        10             0         9             cur = o;
                                                                     10         }
   Internal property tampering      0        21             1        11         return cur ;
                                                                     12     }
purpose, static detectors, i.e., JSJoern and JSTap-vul. We ap-
                                                                     Figure 7: [RQ3-FP] A false positive example of prototype
ply both tools on 300K Node.js packages and then select the
                                                                     pollution reported by ODG EN.
detected packages with Top 20 weekly downloads for manual
verification. Table 7 shows the comparison results. JSJoern
and JSTap have very high FPs because they do not have points-         1   // curlrequest@1 .0.1
to information. Due to the lack of points-to information, they        2     exports . request = function( options , callback ){
                                                                      3        if ( arguments . length === 1) {
have to make many over-approximations, which lead to wrong            4          exports . request . call (this, options , callback );
call edges. Note that we did not compare with either dynamic          5        ... } // request calls itself .
                                                                      6        if ( options . retries ) {
or regex based detectors on FPs, because they are using dif-          7          exports . request ( options , function ( err ) {}
ferent techniques, which tend to have low FPs. We also did            8        ... } // request calls itself .
                                                                      9          exports . copy ( options ); // request calls copy .
not compare with Synode-det or Nodest due to scalability             10     }
issues: Nodest needs installations of all dependencies and           11     exports . copy = function ( obj ) {
                                                                     12        for (var i in obj ) {
Synode-det does not support many ES6 features.                       13          if ( Array . isArray ( obj [i ]) ) {...}
                                                                     14          else if (typeof obj [i] === ’ object ’) {
   We also manually inspect all the FPs for ODG EN and               15             copy [i] = obj [i] ? exports . copy ( obj [i ]) :
break down the FPs by vulnerability types and reasons in                                  null; // copy calls itself .
                                                                     16             } else {...}
Table 8. There are three main reasons: (i) unmodeled built-          17          }
in functions, (ii) unsolvable constraints, and (iii) intended        18        return copy ;
                                                                     19     };
functionalities. First, our prototype of ODG EN only models
popular Node.js built-in functions, i.e., those used by more         Figure 8: [RQ3-FN] A false negative example in detecting
than 5% packages. If ODG EN does not model a unpopular               a legacy path traversal vulnerability (multiple recursive calls
function especially when it is used for sanitization, ODG EN         lead to object explosion and time-out).
may report a false positive. Second, ODG EN does not solve
all the control- and data-flow constraints, but only calculates
all possible constant values if they are available. Therefore,       they involve many different web frameworks, many of which
it is possible that ODG EN finds a path, but the constraints         have not been modeled in our prototype implementation.
along the path cannot be satisfied. Third, some packages may
                                                                        Table 9 shows the false negatives of ODG EN and exist-
be designed for a certain functionality, e.g., executing an OS
                                                                     ing analysis tools in detecting CVE vulnerabilities. Clearly,
command. ODG EN will detect them as command injection,
                                                                     ODG EN’s true positives are the highest and false negatives
but this is not a vulnerability.
                                                                     are the lowest, i.e., outperforming all existing works in detect-
   Figure 7 shows an FP example of unsolvable constraints            ing legacy CVE vulnerabilities because of the modeling of
for prototype pollution. ODG EN reports it as prototype pol-         object-level data dependencies. We breakdown all the FNs
lution because ODG EN finds two vulnerable assignments at            of ODG EN into two reasons in Table 10 and describe them
Lines 7 (in the first loop run) and 8 (in the second loop run).      below. First, we only modeled a limited number of built-in
Then, the assigned value at Line 8 is also controllable by the       functions, i.e., those that are adopted by more than 5% of
adversary. However, although the assigned value o at Line 8          Node.js packages. Therefore, ODG EN may miss some data
is controllable by the adversary, it happens to be the same as       dependencies due to lack of modeling. Second, the abstract
the assignee cur[nameTokens[i]]. ODG EN needs to add                 interpretation of ODG EN may time out and leave a partial
additional constraints for the assigned value so that it can         ODG without finishing interpreting all Node.js functions.
remove such an FP.
                                                                        We also show a specific FN example in Figure 8. This
False Negatives. In this part, we evaluate the false negatives       example has a path traversal vulnerability, but the abstract
(FNs) of ODG EN by using a benchmark of legacy CVE vul-              interpretation cannot reach the vulnerable code because of
nerabilities. Specifically, we downloaded historical packages        multiple recursive calls for both request() and copy() func-
(until February 2020) with five categories of vulnerabilities        tions. The number of object nodes for each functions is over
from CVE as a benchmark. It is worth noting that we exclude          15k and multiple recursive calls lead to an object explosion
some vulnerabilities, such as XSS in this benchmark, because         even with our hybrid branch sensitivity.



152     31st USENIX Security Symposium                                                                          USENIX Association
        Table 9: [RQ3-FN] Comparison of ODG EN with prior program analysis in detecting legacy CVE vulnerabilities.
                    Total                    Command injection     Prototype pollution   Arbitrary code execution                                      Path traversal Internal property tampering
      Detector
                 TP FN                       TP     FN             TP        FN          TP           FN                                               TP      FN     TP             FN
      NodeJsScan 5 251                        2      73             -         -           2           29                                                1      86      -              -
      JSJoern     39 217                     22      53             -         -           5           26                                               12      75      -              -
      JSTap-vul   52 204                     27      48             -         -           5           26                                               12      75      -              -
      Synode-det   7 249                      6      69             -         -           1           30                                                0      87      -              -
      Nodest       7 249                      7      68             -         -           0           31                                                -       -      -              -
      PPFuzzer    29 23                       -       -            29        23           -            -                                                -       -      -              -
      Ensemble   115 141                     46      29            29        23          13           18                                               27      60      0             11
      ODG EN     189 67                      67       8            40        12          20           11                                               55      32      7              4




                                                                                                       Percentage of finished packages [%]
                                                                                                                                                                      Branch-sensitive
                                                                                                                                                                     Branch-insensitive
Table 10: [RQ3-FN] A breakdown of reasons of FNs of                                                                                          100
ODG EN.                                                                                                                                       90
                                                                                                                                              80
  Vulnerability name                            # Timeout      # Unmodeled function
                                                                                                                                              70
  Command injection                                  4                  4                                                                     60
  Prototype pollution                               9                  3                                                                      50
  Arbitrary code execution                           5                  6                                                                     40
  Path traversal                                    22                 10                                                                     30
  Internal property tampering                        2                  2                                                                     20
                                                                                                                                              10
                                      60
                                                            Statement                                                                          0
         Percentage of Packages [%]




                                                             Function                                                                              0     5     10      15      20         25   30
                                      50
                                                                                                                                                                    Time [s]
                                      40                                                      Figure 10: [RQ4-Performance] CDF graph of total execution
                                      30                                                      time to finish analysis.
                                      20
                                                                                              are as follows. First, there are some dead code that are copied
                                      10                                                      from another package or online that is not invoked from the
                                      0
                                                                                              exported function. Second, some packages may dynamically
                                                                                              include a file depending on the inputs, which cannot be stati-
                                       0
                                                10

                                                  0

                                                  0

                                                  0

                                                  0

                                                  0

                                                  0

                                                  0

                                           90 0
                                                00
                                               -2

                                               -3

                                               -4

                                               -5

                                               -6

                                               -7

                                               -8

                                               -9
                                             0-




                                             -1
                                            10

                                            20

                                            30

                                            40

                                            50

                                            60

                                            70

                                            80




                                                                                              cally resolved. Third, some functions, particularly exported
                                               Coverage [%]
                                                                                              ones, will return another function as a return value—such
Figure 9: [RQ4-Coverage] Distribution of statement and func-                                  returned functions will only be called if another package in-
tion coverage (timeout: 30 seconds). One major reason of                                      vokes them.
uncovered code is the runtime inclusion of JavaScript files
depending on inputs.                                                                          Performance Overhead. In this subsection, we answer the
                                                                                              research question of the performance overhead of ODG EN
6.4    RQ4: Abstract Interpretation Performance                                               in generating ODG for real-world Node.js packages. Our
                                                                                              methodology is as follows. We randomly select 500 Node.js
We answer the research question on the code coverage and                                      packages and run ODG EN against all the packages until the
performance overhead of abstract interpretation implemented                                   analysis finishes or time out. Figure 10 shows a CDF graph
in ODG EN.                                                                                    with 30 seconds as the time-out threshold: ODG EN finishes
Code Coverage. In this subsection, we answer the research                                     analyzing 85% of packages within 30 seconds when being
question on the code coverage of ODG EN’s abstract interpre-                                  branch sensitive and 93% when being branch insensitive. This
tation in terms of two specific metrics: statement coverage                                   evaluation shows that ODG EN is efficient in generating ODG
and function coverage. Statement coverage defines the per-                                    for most of Node.js packages.
centage of statements that are executed and function coverage
                                                                                              6.5    RQ5: Branch-sensitivity
the percentage of functions that are analyzed by ODG EN.
Both metrics show how complete ODG EN is in analyzing                                         In this subsection, we answer the research question on
Node.js packages. Figure 9 shows a distribution graph of state-                               how branch-sensitivity affects the vulnerability detection of
ment and function coverages when analyzing 500 randomly-                                      ODG EN. Table 11 shows the number of detected vulnerabil-
selected Node.js packages with a timeout as 30 seconds. The                                   ities under different branch sensitivities. Clearly, the hybrid
figure is almost an even distribution graph from 0 to 90% and                                 branch sensitivity adopted by ODG EN detects the largest
then shows a sudden jump in 90–100%. Actually, about 40%                                      number of vulnerabilities: It combines both advantages, i.e.,
of packages have 100% code coverage.                                                          accuracy and scalability, with and without branch sensitivity.
   The reasons of a relatively low coverage of some packages                                     Figure 11 shows why the hybrid branch sensitivity will help



USENIX Association                                                                                                                                      31st USENIX Security Symposium              153
                                                                            and leave the modeling of an event-based call graph like
Table 11: [RQ5] the number of detected legacy CVE vulnera-
                                                                            Madsen et al. [25] as a future work.
bilities with branch sensitivity enabled and disabled.
                                                                          • For-loop and Recursive Call in Abstract Interpretation. As
 Vulnerability name          Hybrid Branch-sensitive Branch-insensitive
                                                                            discussed in Section 3.2, ODG EN extensively executes a
 Command injection             67         64                66
 Prototype pollution           40         36                29              for-loop until no more new objects outside the loop are
 Arbitrary code execution      20         18                17              being looked-up. ODG EN also adopts a minimum time as
 Path traversal                55         55                51              three and a maximum as ten in abstractly interpreting for
 Internal property tampering    7          6                 7
                                                                            loops and recursive calls. The minimum value is designed
 Total                        189        179               170
                                                                            in case some external objects are not modeled in depth; the
 1 // limdu@0 .9.4                                                          maximum value is designed to avoid dead loop and reduce
 2 exports . toSvmLight =                                                   performance overhead.
 3     function( dataset , bias , binarize ,
            firstFeatureNumber ) {                                        • Dynamically-included Files. As a general limitation of
 4       var lines = "";
 5       for (var i =0; i < dataset . length ; ++ i) {                      static analysis, ODG EN cannot analyze any files that are
 6         var line = (i >0? "\n": "") + // 2 objects                       dynamically included depending on user inputs. This can
 7         ( binarize ? ( dataset [i ]. output >0? "1": " -1"):
                 dataset [i ]. output ) + // 2+1 objects                    only be analyzed with user inputs and dynamic analysis.
 8         featureArrayToFeatureString ( dataset [i ]. input ,
                 bias , firstFeatureNumber ); // 54 objects
                                                                          • Sanitization Functions. The prototype implementation
 9         // 2*3*54 objects                                                of ODG EN adopts a list of sanitization functions, e.g.,
10         lines += line ;
11       }; // (2*3*54) ^3=34 ,012 ,224 objects
                                                                            parseInt, in analyzing dataflow. Currently, the list is gen-
12     ...                                                                  erated manually and we leave it for the future work for
13     }
                                                                            automatic generation.
Figure 11: [RQ5] A false negative in detecting a legacy                   Path-sensitivity. ODG EN is partially path-sensitive, i.e.,
command injection vulnerability with branch-sensitive mode                ODG EN will calculate boolean, string and integer values if
(The number of objects explodes and ODG EN times out).                    they are either constant or enumerable. For an if statement, if
the detection of more vulnerabilities. We annotate the source             the value can be determined, ODG EN will abstractly interpret
code with the number of object nodes in branch sensitivity                only one branch; otherwise, ODG EN will abstractly interpret
enabled. Because the source code has multiple conditional ex-             both branches in parallel.
pressions and a for loop, the number of object nodes quickly              8   Related Work
increases to over 34 million. ODG EN will reduce to branch in-
sensitive mode in abstractly interpreting the code when object            Node.js Vulnerability Detection and Defense. In the past,
explosion is detected.                                                    researchers have studied Node.js vulnerabilities and we dis-
                                                                          cuss them based on their vulnerability types. Arteau [3] pro-
7     Discussion and Limitation                                           poses a fuzzer to explore Node.js packages for prototype
Ethics: Responsible Disclosure. We have disclosed all 180                 pollution. DAPP [13] uses AST and control-flow patterns to
zero-day vulnerabilities to their developers together with                detect prototype pollution vulnerabilities with very high false
Proof of Vulnerability (PoV) under the help of snyk.io. All               positive and negative rates (50.6% and 84.6% respectively).
the details of these vulnerabilities can be found in the ap-              ObjLupAnsys [12] detects prototype pollution by expanding
pendix. If we do not hear from the developer, we will publicly            object lookups and propagating taints during abstract interpre-
release the vulnerability after a 60-day disclosure window. So            tation. Nodest [1] proposed a closed-source detection frame-
far, 12 vulnerable packages have already been fixed.                      work to detect command injection vulnerabilities following
Prototype Implementation and Limitation. We now discuss                   the risks as mentioned by Ojamaa et al. [26]. Then, SYN-
several implementation choice and limitation.                             ODE [2] adopts a rewriting technique to enforce a template
                                                                          before executing a possible injection API like eval. Many
• Supported JavaScript Features. Our prototype implementa-                prior works [22, 27, 28] propose to detect or defend against
  tion follows the popularity of AST features among Node.js               regular expression DoS (ReDoS); Davis et al. [23] propose to
  packages, i.e., we implemented those that are used by more              defend against Event Handler Poisoning (EHP) DoS attack.
  than 5% of packages. Note that ODG EN can still analyze                    Other than specific vulnerabilities, ConflictJS [29] studied
  packages with unimplemented features but just skip the                  and analyzed conflicts among different JavaScript libraries;
  unimplemented part.                                                     Zimmermann et al. [30] studied the robustness of third-party
• Asynchronous Callbacks and Events. The prototype im-                    Node.js packages and their influence on other packages’ secu-
  plementation of ODG EN adopts a queue structure to store                rity. Researchers [31] have also proposed to study the binding
  asynchronous callbacks during registration and invokes                  layers of the Node.js for all kinds of vulnerabilities. Minin-
  them one by one. We acknowledge that this is just one of                ode [32] proposes to reduce the attack surface of Node.js and
  many possibilities that could happen in a real execution                improve the overall security. As a comparison, ODG EN is the



154    31st USENIX Security Symposium                                                                              USENIX Association
first general graph query-based framework of JavaScript for          is proposed by Yamaguchi et al. [15] as a general frame work
efficient detection of a variety types of Node.js vulnerabilities.   combining CFG, DFG, and AST to detect C/C++ vulnerabil-
Client-side JavaScript Security. JavaScript is traditionally         ities. Later on, CPG is ported to PHP by Backes et al. [16]
used at client-side as the scripting language and has been           as an open-source tool called phpjoern [21]. As a compar-
studied [33–36] long before the appearance of Node.js. Cross-        ison, ODG EN models object dependencies, such as object
site scripting (XSS) [37–41] and Cross-Site Script Inclusion         lookup/definition, which are unavailable in any of existing
attack (XSSI) [42] attacks are well studied on the client            graph structures.
side. Malicious JavaScript has been studied by many prior               Other than graph-based frameworks, in the past, code anal-
works, such as HideNoSeek [43], JShield [44] and JSTap [8],          ysis [64–68] has been also widely used to detect various vul-
for detection and defense. Researchers proposed to secure            nerabilities on different platforms. The concept of objects
JavaScript via security policies, such as content security pol-      and relations between objects are also adopted in traditional
icy. Examples are like GateKeeper [45] and CSPAutoGen [46].          program analysis and defenses [69, 70], such as Object Flow
Program analysis [47, 48] have also been adopted at the client       Integrity [70]. The concepts of objects in JavaScript are differ-
side for security analysis. Many prior works [49–52] have            ent from those on C/C++ due to the existence of prototype and
been proposed to restrict JavaScript, especially those from          runtime resolution, which makes traditional object analysis
third-party, in a subset for security. We believe that ODG is        not applicable on JavaScript.
able to analyze client-side JavaScript as well and leave those
as our future work. In the evaluation, we compared ODG EN            9   Conclusion
with JSTap, a client-side JavaScript analysis tool that can gen-     In this paper, we propose to generate a novel graph struc-
erate program dependency graph (PDG). The results show               ture, called Object Dependence Graph (ODG), via abstract
that ODG EN can detect more vulnerability than JSTap.                interpretation. ODG accepts graph queries to mine a vari-
Static Analysis of JavaScript. TAJS [10] and JSAI [11]               ety of Node.js vulnerabilities, especially those related to ob-
adopt abstract interpretation to analyze JavaScript programs         jects such as prototype pollution and internal property tamper-
for more accurate call graph generation and then detect type-        ing. We implement a prototype, open-source system, called
related errors. Madsen et al. [25] propose event-based call          ODG EN, to construct ODG via context- and flow-sensitive
graph to detect problems reported on StackOverflow. Brave’s          static analysis with hybrid branch sensitivity and points-to
PageGraph [53] and its predecessor AdGraph [54] model the            information. Our evaluation reveals 180 zero-day vulnerabil-
relations between different browser objects like scripts, DOM        ities and 70 of them have already been assigned with CVE
and AJAX during runtime with concrete inputs. JAW [55]               identifiers.
models browser objects in a Hybrid Property Graph, which
contains Event Registration, Dispatch and Dependency Graph,          Acknowledgement
Inter-Procedural Call Graph, AST, PDG, and CFG. Guarnieri            We would like to thank our shepherd, Alexandros Kapravelos,
et al. [9] propose to adopt heap graph to model local object re-     and anonymous reviewers for their helpful comments and
lations. SAFE [56] and follow-ups [17, 57] convert JavaScript        feedback. This work was supported in part by National Sci-
to an IR form and adopt an internal structure for abstract in-       ence Foundation (NSF) under grants CNS-20-46361 and CNS-
terpretation. As a comparison, the lattice structure in TAJS         18-54001 and Defense Advanced Research Projects Agency
and JSAI, the heap graph by Guarnieri et al., the Object Prop-       (DARPA) under AFRL Definitive Contract FA875019C0006.
erty Graph in the aforementioned ObjLupAnsys [12], and               The views and conclusions contained herein are those of the
the data structure in SAFE change during abstract interpreta-        authors and should not be interpreted as necessarily represent-
tion, which cannot be used offline for graph query, because          ing the official policies or endorsements, either expressed or
many object-related information gets lost as the interpretation.     implied, of NSF or DARPA.
PageGraph, AdsGraph and Hybrid Property Graph are offline
structure, but they are designed to include browser objects          References
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158   31st USENIX Security Symposium                                                                       USENIX Association
                  Table 12: A List of command injection zero-day vulnerabilities found by ODG EN (80 in total).
   Package Name                  Version       Status           CVE #                         Package Name               Version     Status       CVE #
   adb-driver                      0.1.8     confirmed       CVE-2020-7636                   pomelo-monitor                0.3.7   confirmed         -
   apiconnect-cli-plugins          6.0.2     confirmed       CVE-2020-7633                    promise-probe                0.1.8      fixed    CVE-2019-10791
   aws-lambda                      1.0.4        fixed       CVE-2019-10777                         pulverizr               0.7.0   confirmed   CVE-2020-7603
   blamer                         0.1.13        fixed       CVE-2019-10807                         push-dir                0.4.1   confirmed   CVE-2019-10803
   clamscan                        1.1.0     confirmed       CVE-2020-7613                 pygmentize-bundled             2.3.0    confirmed         -
   closure-compiler-stream        0.1.15     confirmed       CVE-2020-7604                             rpi                 0.0.3   confirmed   CVE-2019-10796
   codecov                         3.6.1        fixed      CVE-2020-7596/7597                  serial-number               1.3.0   confirmed   CVE-2019-10804
   compass-compile                 0.0.1     confirmed       CVE-2020-7635              strong-nginx-controller           1.0.2    confirmed   CVE-2020-7621
   compile-sass                    1.0.3        fixed       CVE-2019-10799                truffle-compile-vyper           1.0.27   submitted         -
   curling                         0.3.0     confirmed      CVE-2019-10789                          umount                 1.1.6   confirmed   CVE-2020-7628
   devcert-sanscache               0.4.6        fixed       CVE-2019-10778                            vsce                1.71.0   confirmed         -
   diskusage-ng                    0.2.4     confirmed       CVE-2020-7631                   connection-tester            0.2.0    confirmed   CVE-2020-7781
   docker-compose-remote-api       0.1.4     confirmed       CVE-2020-7606                            buns                 1.1.6   confirmed   CVE-2020-7794
   effect                          1.0.4     confirmed       CVE-2020-7624                    monorepo-build              0.1.9    confirmed   CVE-2020-28423
   enpeem                          2.2.0     confirmed      CVE-2019-10801                    s3-kilatstorage             0.5.6    confirmed   CVE-2020-28424
   fsa                             0.5.1     confirmed       CVE-2020-7615                     geojson2kml                0.1.1    confirmed   CVE-2020-28429
   fsh                             0.0.2     confirmed             -                             image-tiler              2.0.1    confirmed   CVE-2020-28451
   get-git-data                    1.3.1     confirmed       CVE-2020-7619                           curljs                0.1.2   confirmed   CVE-2020-28425
   git-add-remote                  1.0.0     confirmed       CVE-2020-7630            nuance-gulp-build-common            0.0.1    confirmed   CVE-2020-28430
   git-diff-apply                 0.19.7        fixed       CVE-2019-10776                       ffmpeg-sdk                0.0.5   confirmed   CVE-2020-28435
   git-revision-webpack-plugin     3.0.4     confirmed       CVE-2020-7612                 lycwed-spritesheetjs           1.2.2    confirmed         -
   git-tag                         0.2.0     confirmed             -                               wangzhe                 1.0.0   confirmed         -
   giting                          0.0.7        fixed       CVE-2019-10802                  karma-ckb-reporter             0.0.3   confirmed         -
   gulp-anybar                     1.0.1     confirmed             -                              surfboard                0.1.0   confirmed         -
   gulp-scss-lint                  1.0.0     confirmed       CVE-2020-7601                ensure-module-latest            1.0.9    confirmed         -
   gulp-styledocco                 0.0.3     confirmed       CVE-2020-7607                         geojson2                0.1.8   confirmed         -
   gulp-tape                       1.0.0     confirmed       CVE-2020-7605            kill-process-occupying-port         0.0.1    confirmed         -
   heroku-addonpool               0.1.15     confirmed       CVE-2020-7634                       shelljs.exec             1.1.8    confirmed         -
   im-resize                       2.3.2        fixed       CVE-2019-10787                 lycwed-spritesheetjs           1.2.2    confirmed         -
   install-package                 0.4.0     confirmed       CVE-2020-7629                       theme-core                0.2.5   confirmed         -
   jscover                         1.0.0     confirmed       CVE-2020-7623                         wc-cmd                  1.0.9   confirmed         -
   karma-mojo                      1.0.1     confirmed       CVE-2020-7626                      gulp-tvm-tsc               0.3.4   confirmed         -
   lsof                            0.1.0     confirmed      CVE-2019-10783          nuance-gulp-build-packers-dotnet      0.0.0    confirmed         -
   mysql-dumper                    6.3.0     confirmed             -                            stream-jspm                0.0.1   confirmed         -
   network-manager                 1.0.2     confirmed      CVE-2019-10786                  hot-update-package            1.0.6    confirmed         -
   node-key-sender                1.0.11     confirmed       CVE-2020-7627                        pstracker                0.0.4   confirmed         -
   node-mpv                        1.4.3     confirmed       CVE-2020-7632                         tile-web                3.0.0   confirmed         -
   node-prompt-here                1.0.1     confirmed       CVE-2020-7602                            tvm                 0.8.14   confirmed         -
   npm-programmatic               0.0.12     confirmed       CVE-2020-7614                    nmcli-wrapper                0.7.0   confirmed         -
   op-browser                      1.0.6     confirmed       CVE-2020-7625                    gulp-shellexec              0.4.4    confirmed         -




                  Table 13: A List of prototype pollution zero-day vulnerabilities found by ODG EN (19 in total).
                  Package Name          Version       Status         CVE #           Package Name         Version        Status       CVE #
                  asciitable.js          1.0.2      confirmed     CVE-2020-7771          fun-map           3.3.1       confirmed   CVE-2020-7644
                  bayrell-nodejs         0.8.0      submitted           -           grunt-util-property    0.0.2       confirmed   CVE-2020-7641
                  blindfold              1.0.1      submitted           -            lodash._baseset       4.3.0       submitted         -
                  class-transformer      0.2.3         fixed      CVE-2020-7637      jquery-deparam        0.5.3       submitted         -
                  debt                   0.0.4      submitted           -                 magico           1.1.1       submitted         -
                  dnspod-client          0.1.3      submitted           -             node-file-cache      1.0.2       submitted         -
                  draft                  0.2.3      submitted           -             object-helpers       0.0.4       submitted         -
                  extend2                1.0.1      submitted           -             parse-mockdb         0.4.0       submitted         -
                  fetch-wrap             0.1.2      submitted           -                propper           1.3.0       submitted         -
                  field                  1.0.1      submitted           -




             Table 14: A List of Arbitrary Code Execution zero-day vulnerabilities found by ODG EN (14 in total).
                 Package Name             Version       Status         CVE #           Package Name       Version        Status       CVE #
                 @flammae/helpers           0.0.3     submitted           -             lisp-json-to-js    0.4.1       submitted         -
                 access-policy              3.1.0     comfirmed     CVE-2020-7674            mosc          1.0.0       confirmed   CVE-2020-7672
                 alt-class                  0.0.3     comfirmed           -              node-extend       0.2.0       comfirmed   CVE-2020-7673
                 cd-messenger              2.7.26     comfirmed     CVE-2020-7675        node-import       0.9.2       confirmed   CVE-2020-7678
                 couchdb-ddoc-test          1.0.0     comfirmed           -               node-rules       4.0.2          fixed    CVE-2020-7609
                 inline-ng2-resources      1.1.0      submitted           -                pixl-class      1.0.2          fixed    CVE-2020-7640
                 json-log-filter            0.1.2     submitted           -                 thenify        3.3.0       comfirmed   CVE-2020-7677




USENIX Association                                                                                              31st USENIX Security Symposium                  159
                 Table 15: A List of Path Traversal zero-day vulnerabilities found by ODG EN (30 in total).
           Package Name      Version       Status        CVE #                    Package Name           Version     Status       CVE #
           11xiaoli           1.1.0      submitted          -                rollup-plugin-dev-server     0.4.3    submitted         -
           123qwe             1.0.0      submitted          -              rollup-plugin-serve-favicon    0.4.7    confirmed   CVE-2020-7684
           1997server         1.3.0      submitted          -                   rollup-plugin-serve       1.0.1    confirmed   CVE-2020-7683
           allserverming      1.0.0      submitted          -                  rollup-plugin-server       0.7.0    confirmed   CVE-2020-7686
           entryhttp          1.0.0      submitted          -                      static-server-g        1.0.0    submitted         -
           fanwen             1.0.0      submitted          -                        thy_server           1.6.0    submitted         -
           fast-http          0.1.3      confirmed    CVE-2020-7687                   uekserver           1.0.0    submitted         -
           jbbmyplay          1.0.1      submitted          -                      w1703_server           1.2.0    submitted         -
           lddll              1.0.0      submitted          -                       waterfallhzw          1.0.0    submitted         -
           lhm-ssi            1.0.1      submitted          -                           wu456             1.0.0    submitted         -
           lserver            1.0.9      submitted          -                          xuewarp            1.0.0    submitted         -
           marked-tree        0.8.1      confirmed    CVE-2020-7682               xxx-server-yyy          1.0.1    submitted         -
           marscode          1.0.1-0     confirmed    CVE-2020-7681                    zlymain            1.0.0    submitted         -
           musciplayer-szj    2.0.0      submitted          -                         zzl-server          1.0.5    submitted         -
           myserver123        1.0.0      submitted          -                        xhttpserver          0.0.6    submitted         -




                       Table 16: A List of XSS zero-day vulnerabilities found by ODG EN (13 in total).
                         Package Name      Version       Status     CVE #        Package Name       Version      Status    CVE #
                         buildseverlzz      1.0.0      submitted      -              sheepy          0.1.1     submitted     -
                         hxsstatic          1.0.8      submitted      -           simple_server      0.1.0     submitted     -
                         lserver            1.0.9      submitted      -         simplewebserver      1.2.0     submitted     -
                         lymph-server       1.2.0      submitted      -          xxx-server-yyy      1.0.1     submitted     -
                         lyss               0.0.1      submitted      -             zzl-selver       1.0.3     submitted     -
                         min-http           1.0.6      submitted      -             zzl-server       1.0.5     submitted     -
                         node-servers       1.0.3      submitted      -




          Table 17: A List of internal property tampering zero-day vulnerabilities found by ODG EN (24 in total).
                     Package Name        Version       Status      CVE #         Package Name            Version     Status    CVE #
                     anyargs              1.0.5      submitted       -               leFunc                1.2.5   submitted     -
                     citeproc-js-node     0.0.3      submitted       -             lethexa-adt            0.0.13   submitted     -
                     diso.router          6.0.3      submitted       -             optometrist             1.0.1   submitted     -
                     domlib               1.0.7      submitted       -            resorting-key            1.0.0   submitted     -
                     hyperdrive-ui        4.0.2      submitted       -                solar                0.1.6   submitted     -
                     x-validator          0.1.0      submitted       -       immutable-record-class        3.8.1   submitted     -
                     ini                  2.0.0      submitted       -             lazy-cache              2.0.2   submitted     -
                     acos-kelmu           0.1.1      submitted       -                 bare                0.0.2   submitted     -
                     charity-base-form    1.9.0      submitted       -       common-codegen-tests         2.2.3    submitted     -
                     cookiemonster        1.1.0      submitted       -        deherd-scraper-engine       1.2.11   submitted     -
                     ikagaka.nar.js       3.0.3      submitted       -           jquery-register           1.1.1   submitted     -
                     ndx-modified         0.1.2      submitted       -               ng-pipe              1.4.10   submitted     -




160   31st USENIX Security Symposium                                                                                                   USENIX Association
