--- type: Article title: Security Analysis of eIDAS — The Cross-Country Authentication Scheme in Europe description: "A security analysis of eIDAS, the cross-border electronic identity scheme European member states must recognise. Testing national eIDAS-Connector and eIDAS-Service implementations found XML attacks reaching them through SAML: 7 of 15 services were open to denial of service or server-side request forgery, and 5 let local files be read and sent to the attacker via XML external entities." resource: "https://www.usenix.org/conference/woot18/workshop-program" tags: [article, webseclist-reference, en, usenix, xxe, ssrf, dos, saml, sso, info-leak, owasp-a03-2021, owasp-a07-2021, owasp-a10-2021] generated: by: webseclist-refs/1 at: "2026-08-17T10:10:34+00:00" status: stable stale_after: 2027-08-17 sources: - id: original resource: "https://www.usenix.org/conference/woot18/workshop-program" title: Security Analysis of eIDAS — The Cross-Country Authentication Scheme in Europe last_modified: 2018-07-02 also_at: - "https://www.usenix.org/system/files/conference/woot18/woot18-paper-engelbertz.pdf" authors: [] canonical_url: "" cited_by: - "2018.md:90" commit: "" content_sha256: 8bf0125f11cf8aae12a424e1ea45892e6db406096823e9fdbe96ed24d21f7e58 depth: full depth_reason: default kind: article language: en licence: unknown original_url: "https://www.usenix.org/conference/woot18/workshop-program" published: 2018-07-02 publisher: USENIX publisher_english: "" raw_sha256: d97e63bc33308ada81b3eabcaddac810fde05b1946e1cadbdcd93ca8c989faf7 retrieved_from: "https://www.usenix.org/system/files/conference/woot18/woot18-paper-engelbertz.pdf" retrieved_kind: live retrieved_utc: "2026-08-17T10:10:34+00:00" slug: 2018-usenix-woot-18-workshop-program snapshot: "" title_english: "" translation_file: "" translation_of: "" --- # Security Analysis of eIDAS — The Cross-Country Authentication Scheme in Europe **Security Analysis of eIDAS — The Cross-Country Authentication Scheme in Europe** - Author not stated, USENIX. - Published: 2018-07-02 - Original: - Also published at: - Preserved from: https://www.usenix.org/system/files/conference/woot18/woot18-paper-engelbertz.pdf (live) on 2026-08-17 - Licence: unknown Rights remain with the original author and publisher. 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Security Analysis of eIDAS – The Cross-Country Authentication Scheme in Europe Nils Engelbertz, Nurullah Erinola, David Herring, Juraj Somorovsky, Vladislav Mladenov, Jörg Schwenk Chair for Network and Data Security, Horst Görtz Institute for IT-Security, Ruhr University Bochum Abstract In 2014, the European Commission released the eIDAS regulation to target the compatibility of cross-country electronic services within the European Union. eIDAS (electronic IDentification, Authentication, and Trust Ser- vices) defines implementation standards and technolo- gies for electronic signatures, digital certificates, Single Sign-On (SSO), and trust services. It is based on well- established standards, such as SAML, to achieve high security and compatibility between EU countries. In this paper, we present the first security study of au- Figure 1: Overview of the eIDAS authentication scheme thentication schemes used in eID services. Our secu- depicting the End-User, Service Provider (SP), Identity rity analysis shows that 7 of the 15 European eID ser- Provider (IdP), and both eIDAS Nodes. vices were vulnerable to XML-based attacks which en- abled efficient Denial-of-Service (DoS) and Server Side Request Forgery (SSRF) attacks. On 5 of the 15 eID to meet national requirements and regulations, countries services, we were even able to exfiltrate locally stored chose differing technologies and implemented specific files and send these files to an arbitrary domain. To sup- extensions and functionalities. This caused incompatibil- port the developers and security teams of eID services, ities between eID services and European cross-country we implemented a Burp Suite extension to execute fully- authentication became impossible. automated or semi-automated tests. Additionally, we eIDAS. In 2014, the European Commission addressed summarize best practices related to eID-based authenti- these cross-country incompatibilities for eID authenti- cation and SSO in general. cation by releasing the eIDAS regulation and defining different communication profiles used for authentication 1 Introduction and trust establishment. Throughout this paper, we re- In the last few years, European countries have worked fer to this authentication scheme as eIDAS authentication on developing strong authentication schemes based on scheme. The scheme uses SAML [12] as an authentica- electronic identification (eID) cards. The main goal tion protocol. of these authentication schemes is to provide access to Figure 1 gives a high level overview of cross-country different services, called eID services. For these ser- eIDAS authentication. In our example, a German End- vices, access should be provided for citizens and orga- User wishes to use services provided by a French ser- nizations by using information already available on eID vice provider (SP). The End-User cannot simply use the cards, for example, on the personal ID card which was German IdP directly to authenticate at the French SP issued by a government institution. Many countries de- since the SP could not process the authentication token veloped their own authentication schemes based on well- issued by the IdP. Therefore, eIDAS Nodes are used to established technologies that provide functionalities for translate the tokens and make them compatible between secure browsing, login mechanisms, SSO, or exchang- eID schemes. The SP first forwards the request to the ing confidential data over untrusted networks. In order French eIDAS Node, which translates the request for the German eIDAS Node. The German eIDAS Node 2.1 Single Sign-On (SSO) then forwards the compatible request to the authoritative IdP, which can issue authentication tokens for the End- Single Sign-On (SSO) is a concept to log a user into a User. The authentication token is finally translated for Service Provider (SP) without storing any credentials on the French SP using eIDAS Nodes. that SP. For this purpose, SSO uses a trusted third party called Identity Provider (IdP). An abstract overview of Security of eIDAS. In recent years, it has been shown SSO is depicted in Figure 2. how to break SAML-based SSO systems and login as an arbitrary user [62, 64, 37], read arbitrary files from delegates authentication, requests tokens & claims SAML servers [37], or how to break XML Encryption Service Provider Identity Provider https://sp.com issues tokens & claims https://idp.com and decrypt the exchanged SAML assertions [29, 26, 27, 62]. Because eIDAS makes use of these technologies, such attacks present a serious threat to the eID users and accesses services authenticates, grants access their prevention is, therefore, of high importance. Automated Security Analysis. In order to support End-User UA eID developers in their development process, we ex- tended the tool EsPReSSO (Extension for Processing and Figure 2: An abstract overview of the entities in SSO and Recognition of Single Sign-On Protocols), which facili- their relation to each other. tates in analyzing different SSO protocols and their used information flow. We implemented a prototype of the at- The IdP manages user identities and provides at least tacks described in Section 3 into EsPReSSO so that eID one authentication mechanism, e.g., username/password. developers are able to search for known vulnerabilities. The IdP issues authentication tokens containing informa- Discovered Vulnerabilities. The relevance of these vul- tion about the authenticated End-User. The End-User is nerabilities is proven in our evaluation, as we revealed a human being navigating a user agent (UA), e.g., a web security flaws in 7 of 15 eID services which enabled at- browser. The SP is a publicly available service offer- tacks such as DoS, SSRF, and on 5 of 15 systems, even ing access to resources for registered End-Users. If the unauthorized file exfiltration. We reported the discov- End-User visits the SP and requests access to restricted ered vulnerabilities to the affected providers and national resources, authentication is required. The SP delegates CERTs. We also cooperated with the system develop- authentication of End-Users by issuing an Authentica- ers on implementing the countermeasures and provided tion Request to an IdP. Afterwards, the SP verifies the a second test to verify the implemented fixes. authentication tokens generated by an IdP to authenticate Contributions. The contributions of this paper can be the End-User. summarized as follows: SAML. SAML is an XML [9] standard for exchanging I We present the first security evaluation of existing eID authentication and authorization statements about sub- services and reveal security gaps in 7 of the 15 eID jects [12],and uses XML-based assertions to transmit services. these statements. A SAML assertion contains several essential components: The Issuer element specifies the I We provide a comprehensive overview of the attacks SAML authority that is making the claim(s) in the asser- relevant to eID scenarios. These attacks target the tion – the IdP. The assertion’s Subject defines the prin- underlying TLS protocol [14], XML parser (XXE at- cipal about whom all statements within the assertion are tacks) [70], and cryptographic standards like XML made. Further elements are included to specify message Signature [25] and XML Encryption [15]. validity or user-defined statements relevant for the mes- I We provide a tool to facilitate the security analysis of sage context. eID services, supporting developers and security ex- To protect the integrity of the security claims made by perts to discover security flaws. the Issuer, the whole Assertion element must be pro- tected with a digital signature following the XML Signa- I We summarize the lessons learned in security guide- ture specification [16]. Usage of the SAML assertions in lines and a Best Current Practices section for the de- various XML messages is described in the SAML Bind- ployment of secure eID infrastructures. ings specification [60]. 2 Foundations 2.2 eIDAS Services This section summarizes relevant foundations regarding Many EU countries defined and implemented their own SSO, SAML, and the utilization of SAML in eIDAS. singular eID scheme. Differences between the schemes prevent member states from seamlessly exchanging elec- several gigabytes in size [69, 66]. An example is given tronic identification data and trust services. in Listing 1. First, an entity ent0 is declared, referencing In order to achieve compatibility in cross-boarder eID the string DoS. Next, an entity ent1 references a con- communication, eIDAS was defined [54]. eIDAS does catenation of several times ent0. This back-referencing not provide a standalone SSO solution, but rather speci- to multiple instances of entities, which is defined in the fies a SAML 2.0 based compatibility layer between dif- preceding step, is repeated and results in an exponential ferent eID implementations [19, 12]. The components expansion of the document size. facilitating this cross-border information exchange are 1 3 DAS Nodes “translate” incoming SAML requests from 4 the SP into authentication requests compliant with the 5 ... 6 eID scheme of the end user’s country of origin. On the 7 ]> other side of this process, the eIDAS-Nodes also convert 8 &ent13; the authentication tokens generated by one country into tokens which can be processed by the SP. Listing 1: The Billion Laughs Attack abuses limited recursion of General Entities to exponentially expand the document size. 3 XML Attacks on eIDAS Services DoS Using External Entities. If the XML parser re- eIDAS is based on SAML, which is, in turn, based on solves External Entities, a plethora of DoS attack-vectors eXtended Markup Language (XML). Consequentially, may be available. For example, an adversary might be eIDAS services may be susceptible to XML-based at- able to induce network requests for large remote files, tacks. In this section, we focus on Document Type Def- thereby exhausting network or memory capacity of the inition (DTD) attacks. After sketching out our attacker system under attack. By inducing a large number of model, we provide an overview of common goals for outgoing requests, resources of both the targeted XML DTD attacks and appropriate attack vectors. parser and the destination of the forged requests may quickly become exhausted [70]. An overview regarding how such requests can be forged is given in the next sec- 3.1 Attacker Model and Prerequisites tions. We consider a Web-Attacker that is capable of generating Other Techniques. Several variants of the above attacks XML messages, crafting and sending requests, and se- exist. The Quadratic Blowup attack declares a single lecting the appropriate encoding for each part of the sub- XML Entity that expands into a large string of several mitted request. Furthermore, the attacker controls a pub- megabytes, greatly exceeding the size of the document. licly available server (henceforth attacker-listener) and The Recursive Entity attack exploits XML parsers by re- can observe requests made to this server with arbitrary cursively resolving nested entities [66]. protocols. As we focus on DTD and XML External En- tity attacks, no third party is involved. The goals of the 3.3 SSRF attacker can roughly be categorized into DoS, SSRF, and File Exfiltration, and are further described in the follow- One considerable area of attack exposed by many XML ing sections. parsers is their capability to deal with various URL han- dlers. The following paragraphs explore some meth- ods on how this can be abused for Server Side Request 3.2 Denial-of-Service (DoS) Forgery (SSRF). DoS attacks aim at decreasing the availability of the ser- SSRF Using External DTD. A simple way to force a vice under attack. This is primarily achieved by mak- vulnerable XML parser to perform an outgoing request is ing the target consume large amounts of computational to reference an external DTD. The example in Listing 2 resources such as memory, bandwidth, or processing shows how the XML parser can be induced to query a power while only investing a fraction of the resources service in its local network, which would otherwise be by the attacker [69]. unreachable for an external adversary. Billion Laughs Attack. A well-known DTD-based DoS 1 2 arbitrary content attack is the so-called Billion Laughs Attack [32, 66]. This attack employs recursively defined Internal General Listing 2: Using external DTDs to induce server side Entities, forcing the XML parser to expand a relatively requests [66]. small input document into a document which can reach An alternative for the SYSTEM keyword is PUBLIC "id" as If the content of a referenced file is not well-formed ac- shown Listing 3. cording to the XML specification, well-behaved parsers 1 will abort entity expansion with an exception. Several 2 arbitrary content techniques are known to circumvent this restriction using Parameter Entities to wrap file contents in a block [70, 66]. DTD associated with an identifier id. File Exfiltration Using SSRF. Even if no direct feed- back channel is available, file contents can sometimes SSRF Using External (Parameter) Entities. In addi- still be extracted. If the parser can establish network tion to external DTDs, External Entities can be used to connections, an adversary can proceed as follows: an ex- cause server side requests, as shown in Listing 4. Be- ternal DTD can be used to declare Parameter Entities, cause some parsers are able to restrict the allowed proto- which can then be included in URLs of forged parser re- col handlers, it may be beneficial to try a number of dif- quests. An example is given below [66]. ferent protocols besides http. Examples include, but are 1 file://, and the short UNC path form //. 3 %ext; 4 ]> 1 &send; 2 3 ]> 4 &extEnt; Listing 6: An external document defines an additional XML Entity send which is used for request forgery (see Listing 4: Causing Server Side Requests using External Listing 7) Entities If the Parameter Entity reads a local file, as illustrated Another way to force the parser to perform outgoing re- in Listing 7, its content may then be sent to the attacker quests is to use Parameter Entities [66]. as a part of the URL’s path or query-string. Other Techniques. The XML specification provides 1 2 " > Side Requests from the XML parser. Most prominently, 4 %tmp; schemaLocation and noNamespaceSchemaLocation can cause insecurely configured parsers to issue network re- Listing 7: The file hosted at attacker.org/ext.dtd quests [66]. The xInclude extension [38] provides the concatenates the file content with a request URL using opportunity for an additional attack. Parameter Entities. The example above is a slight variation of a similar tech- 3.4 File Exfiltration nique presented by Morgan and Ibrahim in 2014 [70]. Exfiltration of file content from the parser’s local file sys- tem can be feasible if a direct feedback channel at the ap- 4 Automated Analysis plication level exists. Exfiltration is also possible if file content can be included in forged requests to a destina- The security evaluation of eID services shares many sim- tion under the adversary’s control. ilarities with the analysis of SSO services, since both technologies are based on the same authentication pro- File Exfiltration Using Direct Feedback. In contrast to tocols. This allows for already existing penetration test- the External Entity’s intended purpose of including ad- ing tools to be used in the security evaluation. We de- ditional DTDs from external sources, an adversary can cided to utilize Burp Suite (Burp),1 which is a widely abuse the functionality of External Entities to include used penetration testing tool for web applications. Burp files that are otherwise inaccessible. In Listing 5, we as- acts as an intercepting proxy and can be used to log, in- sume a direct feedback channel, e.g., the application re- tercept, display, and modify HTTP traffic. To facilitate turns the contents of the element in its response. more complex scenarios, Burp offers extension points 1 3 ]> ity. One relevant extension we utilized was the Extension 4 &extEnt; for Processing and Recognition of Single Sign-On Pro- tocols (EsPReSSO).2 This extension is open-source and Listing 5: Using a Direct Feedback channel of the 1 https://portswigger.net/ element to read out /etc/passwd 2 https://github.com/RUB-NDS/BurpSSOExtension is able to automatically identify and classify SSO mes- tificate Viewer greatly eases a quick quality inspection of sages, allowing penetration testers to easily analyze and the included certificates. manipulate SSO flows. DTD-Attacker. To facilitate penetration tests, we imple- In this section, we first describe the basic functional- mented a new feature in EsPReSSO – the DTD-Attacker. ities of EsPReSSO which were available at the start of Based on the attacks summarized in Section 3, we cre- our project. Subsequently, the extensions we added to ated a set of 18 attack vectors and implemented these the tool to improve its usability for eID analyses are pre- into the DTD-Attacker. During testing, the penetration sented. tester can tweak the selected attack vector within the DTD-Attacker. All modifications are automatically ap- 4.1 EsPReSSO – Basic Functionalities plied to the original message. An abstract overview of the DTD-Attackers UI is presented in Appendix C. EsPReSSO was designed and implemented to recognize The DTD-Attacker allows for easy, vector- and distinguish SSO protocols. It has an automatic scan- independent pre-configurations that are automatically ning function that passively inspects the browser’s traf- applied to the selected vectors. For example, the fic by scanning HTTP parameters and keywords. In complexity of the DoS attack vectors can be optimized the event that an SSO protocol is recognized, the re- by specifying a number of recursive entities and entity quest/response is highlighted and a note referencing to references. This allows testers to precisely measure the the protocol is shown. Furthermore, specifically for the impact of the DoS attack. SAML protocol, EsPReSSO provides a SAML-Editor Furthermore, for those attack vectors which cause and SAML-Attacker. URL invocation, the DTD-Attacker allows for the con- SAML-Editor. The SAML-Editor searches each inter- figuration of arbitrary URLs, which may be needed in cepted HTTP request/response for SAML relevant pa- order to evaluate the success of the attack. It is also pos- rameters and automatically decodes the SAML mes- sible to apply a specific encoding to the vector. This may sage before displaying the SAML AuthnReq or Authn- allow penetration testers to bypass simple filter mech- Response, respectively. Furthermore, the SAML-Editor anisms that only work when encountering the standard provides the means to carry out modifications of the in- XML character set, i.e., UTF-8. tercepted messages in a user-friendly way. For a comprehensive vulnerability analysis, a large SAML-Attacker. EsPReSSO also provided a user in- number of attack vectors must be tested. For this rea- terface with a small predefined set of attacks; for exam- son, the DTD-Attacker can be used in a fully automated ple, specific attacks targeting XML Signature processing. mode. Before starting the evaluation, the penetration However, not all known attack vectors were covered by tester only needs to configure a single parameter: the EsPReSSO. attacker-listener URL where the HTTP requests are sent. The provided URL is then automatically inserted into all attack vectors and sent to the target. If the target is vul- 4.2 Extending EsPReSSO nerable, the attacker-listener will receive a correspond- The shortcomings of the previous EsPReSSO version ing request from the target. This automated approach al- and the missing attacks were the motivating factors for lows penetration testers to quickly determine vulnerable the improvement of this extension. targets and what specific attack vectors the target may be vulnerable to. SAML-Editor. SAML messages are transmitted in an encoded form. To alter an intercepted SAML message, SAML-Attacker. We also extended the EsPReSSO a penetration tester needed to first decode the message, functionality for targeted SAML attacks. EsPReSSO then manipulate it, and finally re-encode it before relay- supported the execution of basic Certificate Faking ing the modified message. During security evaluations, (CF) [37] and XML Signature Wrapping (XSW) at- this process can be time consuming and bothersome. We tacks [64]; however, the implementations of these attacks therefore addressed this issue by extending the SAML- contained several bugs. We resolved these bugs and ad- Editor in EsPReSSO to achieve more fine-grained con- ditionally implemented a new user interface for the Sig- trol over each aspect of the intercepted message. As an nature Exclusion (0Sig) / attack [37]. example, it is now possible to easily change the HTTP During execution of the 0Sig / or CF attack, the auditor method (HTTP-GET or HTTP-POST) with the message can now select the specific signature element on which being automatically re-encoded. the attack will be applied. During the CF attack, the We additionally implemented a Certificate Viewer to original certificate is copied, the key is replaced, and the make certificate properties and key material provided certificate is re-signed. Next, the original certificate is within the SAML messages easily accessible. The Cer- replaced and the target message is also re-signed. / s XIn ocation titie D Ent eter) Ent eter) l DT (Par ternal (Par ternal n e clud ve E ities ities am am L erna Ex Ex ema ursi Ex t Sch Rec eIDAS Provider DoS SSRF File Exfiltration eIDAS Pilot Sweden – 71 7 3 7 7 eIDAS Pilot Belgium – 3 3 3 3 3 eIDAS Pilot Czech Republic – 3 3 3 3 3 Provider 1 – 71 7 3 7 7 eIDAS Pilot Estonia – 3 3 3 3 3 eIDAS Pilot France – 3 3 3 3 3 eIDAS Pilot Norway – 3 3 3 3 3 ArubaPEC S.p.A – 3 3 3 3 3 Provider 2 – 71 72 3 72 3 InfoCert S.p.A. – 71 7 3 7 7 Provider 3 – 71 7 3 7 7 Provider 4 – 71 72 3 72 3 Register.it S.p.A – 71 7 3 7 7 Sielte S.p.A – 3 3 3 3 3 TI Trust Technologies srl (TIM) – 3 3 3 3 3 Vulnerable in Total – 7 7 0 7 5 1 To avoid harm, we did not test the full impact of the attacks. 2 Only DNS requests were observed. 3= Not vulnerable, 7= Vulnerable, – = Not evaluated Table 1: XML parsing vulnerabilities are still an effective attack technique to which 7 of the 15 tested SAML endpoints were found to be vulnerable. 5 Evaluation of XML Attacks cluded from the fact that DoS attacks based on Exter- nal (Parameter) Entities are always possible if the XML In our evaluation, we concentrated on the security anal- parser can be tricked into loading external files. We did ysis of general XML-based parsing attacks and their ap- not evaluate whether DoS attacks with nested or recur- plication to eIDAS services. This is because XML-based sive entities were applicable. When testing SAML end- attacks do not necessarily demand the usage of valid ac- points, there is usually no direct server feedback and counts since only XML parsers are targeted. For their one cannot observe whether nested entities are resolved. evaluation, only correct endpoint URLs of the analyzed Therefore, all test vectors with a real DoS potential were service are necessary in order to gain access to the SAML omitted to avoid damaging the tested service endpoints. parsing functionality. No valid eID cards, accounts, or SSRF Attacks. Of the tested servers, seven were vulner- configurations are necessary. This allowed us to test a able to SSRF attacks. These could be executed using large number of eIDAS services. External (Parameter) Entities and by loading external Table 1 shows the results of our evaluation for the 15 DTDs. None of the servers resolved SchemaLocation or tested eIDAS services. It confirms that XML parsing at- XInclude elements. tacks are still a prevalent attack technique. We cooper- ated with the affected providers who were able to suc- File Access. Of the fifteen eIDAS Nodes, five were vul- cessfully apply countermeasures to these attacks. Sev- nerable to attacks where the parsers were forced to read eral providers which have not yet rolled out fixes or have external or local files. Although two additional servers not responded to our emails have been anonymized in were vulnerable to SSRF attacks, we were only able to Table 1. In case of unresponsive providers, we contacted force these servers to issue DNS queries. Reading re- the responsible CERT team regarding the security issues mote external files was not possible. and are currently awaiting further information regarding Lessons Learned. Although DTD vulnerabilities have the status of the fixes. been known since 2005 and multiple security studies ex- DoS Attacks. We were able to confirm the existence of ist, it is surprising that such a large number of vulnera- DoS vulnerabilities in seven services. This can be con- bilities were found. The user agent identifiers included in forged server- I To avoid harm on the evaluated systems, we only veri- side requests indicate that all implementations vul- fied the possibility to carry out DoS attacks and we did nerable against SSRF and DoS are programmed in not actually carry out these attacks. Java. As found in a comprehensive evaluation of XML parsers [66] provided in 2016, all Java XML parsers I During the course of the project, some of the systems are vulnerable against XML External Entity Attacks were updated with newer versions of the applications. (XXEAs) in their default configuration. Consequently, Therefore, some previously discovered security issues services remain vulnerable if the responsible developers were fixed before reporting these to the developers. and administrators do not explicitly disable these inse- cure features. Selected Test Target. We were not able to perform com- We employed the blackbox approach for testing and prehensive penetration tests for all the eIDAS providers do not know whether the vulnerable services share the listed in Table 1. The reason is that we did not pos- same XML stack. Nevertheless, we believe that Java’s sess valid identity cards or other credentials for these insecure defaults are the underlying reason for the abun- providers which are necessary to gain authentication dance of similar vulnerability patterns. tokens for further SAML evaluations. Therefore, for our penetration test, we chose the eIDAS Pilot of the Swedish E-identification Board.3 It provides a demo SP 6 Comprehensive Evaluation of the eIDAS as well as a fictional sending member state Test Coun- Swedish Pilot try XX to simulate eIDAS authentication at a compliant IdP without requiring a valid eID card. This test environ- This section summarizes the security test suite that can ment, available from http://eidasweb.se, allowed us guide both developers and security auditors alike during to simulate an end-to-end eIDAS authentication involv- their work with SAML based SSO environments. A con- ing six SAML endpoints (see Appendix B), inspect all densed overview is given below and in Table 3. the messages exchanged through the user agent between participating services, and above all, to employ our test- 6.1 Testing Methodology suite in the field. We define a number of tests relevant for the eID ser- vices, summarize known attacks, and categorize these 6.2 eIDAS Test-Suite into three different classes. Since many of the targeted Our tests can be roughly divided into three categories: eID services are potentially closed-source web applica- (1) Transport Layer Security, (2) Web Application Secu- tions, the chosen testing methodology is a black-box ap- rity, and (3) Message-Level Security. We provide a digest proach. This allows us to define a generic test suite irre- of the main components that compose the test suite in the spective of a programming language, framework, or sim- following sections. ilar restrictions that might otherwise be imposed by the test-target. Limitations. During this survey we encountered the fol- 6.2.1 Transport Layer Security lowing problems: TLS [14] is a complex protocol used to protect message I National eID schemes generally require a valid eID integrity and confidentiality on the underlying transport card to complete the entire authentication process. protocol, and plays an important role in secure com- Due to the fact that no test eID card was available, we munications. Several critical vulnerabilities have been limited our targets to demo services which allowed au- found in Transport Layer Security (TLS) libraries in thentication without an eID card. For this reason, the the past, ranging from implementation faults to crypto- actual eID based End-User authentication is not part graphic weaknesses (cf. [61, 42, 3, 7, 8]). These prob- of our evaluation. Please note that communication be- lems can largely be mitigated by simply deploying the tween eIDAS compliant parties is not affected by this latest version of the used TLS libraries where the secu- limitation. rity updates have been applied. However, care must still be taken to securely configure the library’s properties. I We focused on SAML because it constructs the com- We evaluated the security of the TLS endpoints using patibility layer of eIDAS. National eID schemes may TLS-Attacker,4 which is currently the most advanced of course be based on different technologies which are and freely available tool to discover security issues in not considered in this work. TLS. We tested the deployed TLS protocol versions I There is no public list of existing eID services. Find- 3 https://www.elegnamnden.se ing such services can, therefore, be a challenging task. 4 https://github.com/RUB-NDS/TLS-Attacker and cipher suites, properties of the used certificates, XSLT Attack (XSLTA). XML Signatures rely on certain and specific TLS attacks. In particular, this included: preprocessing routines called transformations. These DROWN [3], POODLE [43], Heartbleed [57], Bleichen- are used to derive a canonical form of the XML docu- bacher’s attack [6, 7], the invalid curve attack [28], and ment before computing or verifying the associated signa- the padding oracle attack [71]. No host of the Swedish ture. Because the transformations are applied before the eIDAS test infrastructure was found to be vulnerable to document’s signature can be verified, an adversary can any of these attacks, nor did we detect insecure configu- alter the signature’s elements. The rations. XSLT Attack (XSLTA) makes use of this fact and, in the worst case, can lead to arbitrary code execution. The XML processor should, therefore, disable support 6.2.2 Message Level Security for the Extensible Stylesheet Language Transformation SSO protocols usually involve multi-party communica- (XSLT) and terminate validation upon receiving invalid tion. Therefore, it is not sufficient to simply secure the elements. underlying transport; the message itself must be pro- We examined all services of the Swedish eIDAS pilot tected against tampering and, if necessary, provide ap- for XSLTAs and none was found to be vulnerable. propriate guarantees for confidentiality of its contents. XML Encryption Attack (XEA). Several vulnerabil- SAML makes use of XML Signatures [25] and XML En- ities in XML Encryption implementations have been cryption [17] to fulfill these requirements. found in the past, such as attacks against CBC mode in Signature Exclusion (0Sig). / Each recipient of a mes- symmetric ciphers and attacks against asymmetric RSA- sage must only accept a message if a valid signature is PKCS1.5 encryption [29]. Backwards compatibility at- provided. If the application accepts messages which do tacks against secure algorithms must also be taken into not include a signature, the message could be altered and consideration. Successful attacks against XML Encryp- the authentication is broken. tion would undermine the confidentiality goals of eI- None of the six SAML services participating in the DAS’ encrypted SAML assertions [18]. Swedish eIDAS pilot accepted a SAML message without We could not successfully execute or even test the un- a signature. derlying XML Encryption implementation used by the Certificate Faking (CF). The process of replacing the Swedish eIDAS pilot. This is because we were unable element of an XML message with a self- to find a signature bypass against any of the participating generated signature and key is termed Certificate Fak- SAML services and, therefore, could not alter the cipher- ing [37]. Each recipient of a message, where the in- text of encrypted assertions. One endpoint was found to tegrity is protected by an XML signature, must ensure encrypt SAML Assertions using unauthenticated CBC to exclusively use trusted keys for signature verification. mode, potentially enabling attacks on encrypted XML In particular, keys included in the message must not be ciphertexts [29]. However, the enveloped XML signa- considered as trustworthy without further verification. If ture applied to the document’s root element mitigated a single SAML service is vulnerable to Signature Faking, any XML Encryption Attacks. the authentication scheme is broken because a malicious Replay Attack. In an SSO context, replay attacks tar- user is able to forge arbitrary messages and identities. get the multiple redemption of an authentication token, The Swedish eIDAS test environment was found to be regardless of any existing freshness and lifetime restric- resistant against Signature Faking; no involved entity ac- tions. SSO tokens contain at least one parameter guaran- cepted self-generated or faked signatures. teeing freshness and one defining the expiration time. It XML Signature Wrapping (XSW). The XSW attack is up to the SP to implement this verification correctly. against the XML Signature specification was first pub- A special case of Replay Attacks exists in SAML, where lished in 2005 [40]. The main idea behind this attack is the AuthnReq can contain parameters restricting the life- to change the structure of the XML element tree in such a time and guaranteeing freshness. The IdP should verify way that the application’s business logic processes a dif- all relevant parameters. ferent element than the signature verification logic. This Five out of the six tested SAML endpoints accepted allows an adversary to submit arbitrary content to the each token exactly once. Freshness of the token is en- vulnerable service. Several high-profile sites and SAML sured by the IssueInstant attribute and the unique token libraries have been found to be vulnerable to XSW in the ID. The demo SP allowed multiple successful redemp- past [64]. tions of the same AuthnResponse, as long as the token is We tested a number of XSW techniques against the ex- submitted within the correct valid session and within the amined SAML services and were not able to successfully assertion’s validity period. We were not able to circum- execute an XSW attack. vent the freshness or lifetime validation of any SAML endpoint participating in the authentication flow. the Swedish E-Legitimation Board and did not find a Token Recipient Confusion (TRC). As a multitude of XSS vulnerability on any of the sites involved in the sim- SPs may exist, an authentication token must clearly in- ulated eIDAS authentication. dicate its intended destination; a token should only be CSRF. In a Cross-Site Request Forgery (CSRF) attack valid for a single SP to ensure that a malicious SP can a victim is tricked into unknowingly performing state- not redeem captured user tokens at other benign SPs. changing actions on a vulnerable site. To this end, an ad- Our tests were restricted to a single SP and no signa- versary injects malicious requests into the victim’s UA ture bypasses were found; therefore, we could not evalu- which has an authenticated session with the vulnerable ate the TRC attack. application. A CSRF attack abuses the fact that the UA automatically includes session credentials, more particu- larly cookies, in each request [75, 4]. In the past, CSRF 6.2.3 Web Application Security was found to be exploitable in widely deployed SSO so- In SSO and eID authentication schemes, the SP, IdP, and lutions [34, 35]. eIDAS mandates manual user authenti- the eIDAS nodes are web applications. End-User authen- cation for each authentication request [20, Section 2.4.1]. tication involves loading multiple sites such as the SP, This constraint must be implemented by every IdP. If this several redirect pages, and sites specific to the eIDAS is not implemented, a victim can be unknowingly logged Nodes, e.g., the consent page. Thus, attacks which tar- in at arbitrary services or be tricked into authorizing ac- get the web application, such as Clickjacking, XSS, and cess to restricted resources. CSRF, must be considered for all sites loaded during the We did not find any exploitable CSRF vulnerabilities authentication. in the Swedish eIDAS pilot. All critical components appeared to follow best current practices and AuthnRe- Clickjacking. The goal of a Clickjacking or User- sponses were bound to session-specific random tokens. Interface Redressing attack is to trick the user into un- Covert Redirect (CR). Some web applications store the knowingly execute actions of the attacker’s choice. To URL navigated by the End-User before starting the SSO accomplish this, UA features like transparent iFrames authentication and include this parameter as part of the and Drag’n’Drop mechanisms are employed, and are AuthnReq, for example, as a GET parameter next_url often combined with some pretended incentive for the or RelayState. After receiving the authentication to- end-user to induce the intended action [67, 68]. Success- ken, the SP then forwards the user to the resources ini- ful Clickjacking attacks can bypass Same-Origin-Policy tially requested by the End-User. Unfortunately, during checks and circumvent CSRF protection mechanisms, this forwarding, sensitive information can be leaked. As resulting in data exposure or an account to become com- an example, in some SSO protocols, the Referer header promised. In SSO scenarios, Clickjacking vulnerabilities can contain the authentication token. This can potentially can be used to lure the victim into unknowingly authen- lead to information leakage and broken authentication. ticating at the IdP and authorizing the access to restrict- The Swedish eIDAS pilot and, in particular, the demo ed/sensitive resources. SP do not make use of parameter based redirects, and are On this note, an early version of the Swedish eIDAS not vulnerable to Covert Redirect attacks. pilot was vulnerable to Clickjacking attacks due to miss- ing HTTP Security-Headers. Any stage of the authenti- HTTP Security Headers. A number of security related cation process could be framed in a transparent iFrame. HTTP headers have been defined. These mechanisms al- This vulnerability was mitigated before we could reach low communicating entities to share security related in- out to the developers by adding the appropriate X-Frame formation and influence security related behavior or de- -Options header to relevant pages. cisions of each other. In this manner, HTTP security headers play an integral role in safeguarding today’s web XSS. As one of the most common attacks in the mod- application security. ern web, according to [75], XSS has been studied exten- In our tests, we ascertained the presence and sound sively and yet, XSS vulnerabilities and circumventions configuration of the HTTP headers listed below. of XSS protection mechanisms are still frequently found in complex web applications [41, 5, 23, 24, 33, 59]. A X-Frame-Options XSS vulnerability enables a malicious actor to inject ar- Content-Security-Policy bitrary script code into a website’s DOM. The script is Strict-Transport-Security Content-Type subsequently executed by the victim’s UA. Attacker con- X-Content-Type-Options trolled code running in the origin of the attacked page is X-Xss-Protection a critical vulnerability which can bypass the security of Public-Key-Pins the authentication scheme. We carefully inspected the eIDAS test deployment of Furthermore, the directives of the Set-Cookie header 8 Conclusion were checked. In particular, the httpOnly and the secure flags must be set if a cookie contains sensitive informa- To the best of our knowledge, we provided the first se- tion such as session IDs. To prevent CSRF attacks, the curity analysis of the eIDAS infrastructure and trust ser- SAMESITE directive may be added. vices. We find it impressive that many known attacks In Appendix A, we summarize best current practices from previous works were not applicable to the exam- regarding the security headers. ined eIDAS services. We consider this to be a positive result of applying proper countermeasures and following the current security best practices. Nevertheless, we were able to exploit XML parsing 7 Related Work vulnerabilities on about half of the tested services. The fact that most of the vulnerable services appear to be im- In 2003 and 2006 Gross et al. [21, 22], and in 2008 plemented in Java highlights the importance of secure and 2011 Armando et al. [2, 1], a formal model for defaults as well as the consequences this poses to pro- the SAML Browser/Artifact profile was analyzed which duction systems. identified several generic flaws allowing for connection Our survey reveals the complexity of current authen- hijacking/replay, Man-in-the-Middle (MitM), and HTTP tication systems, which is a natural consequence of referrer attacks. In 2012, Somorovsky et al. [64, 63] the complex technology stack in use. Peculiarities of investigated the XML Signature validation of several TLS, XML, SAML, and HTML/JavaScript/AJAX must SAML frameworks and web services, discovering crit- be considered, and each of these technologies must be ical flaws based on XSW. In 2014, Mainka et al. [37] strengthened against potential attacks. Additionally, in- analyzed 22 Cloud SPs and found vulnerabilities on 17 teractions of the various layers and potential security rel- of them. We used the described attack techniques in evant consequences must be taken into account. In our this survey as a basis to set up our catalog for the se- paper, we show again how the insecurity of one compo- curity tests. Mayer et al. [39] discovered, in 2014, criti- nent can bypass the security of the entire system, even if cal vulnerabilities in SAML IdPs by exploiting XSS vul- all other components are secure. nerabilities and flaws in the SAML implementation. In Furthermore, our study made clear that a demand still 2016, Späth et. al [66] provided a comprehensive se- exists for tools which facilitate automatic security analy- curity analysis of XML parsers regarding their security ses. Similarly, carefully compiled documents specifying against XML-based attacks such as XML External En- security best practices appear to be lacking. We hope that tity. This survey provides a comprehensive summary of our tool and the Best Current Practices document can be attack vectors which we used during our evaluation. In used as a foundation for future security researchers to fill 2016 and 2017, Kakavas et al. and Sanso et al. dis- this documentational gap. covered critical vulnerabilities in prominent web appli- Aside from the technical issues we resolved during cations like Office365 [30], GitHub [31], and Slack [58] this evaluation, one major obstacle was in obtaining valid by using already known attack vectors. In 2018, two credentials for testing purposes. We could apply the full novel attack vectors were discovered by RedTeam [56] test suite to only the Swedish eIDAS Pilot because it pro- and Duo [36]. Both vectors used a truncation technique vided a simulation of the eID based End-User authenti- to insert malicious identities within the authentication to- cation. In order to execute a more widespread evaluation, kens without invalidating the digital signature. However, obtaining valid credentials may be necessary. none of the previous security researches covered eID ser- We recognize and appreciate that an increasing num- vices and evaluated the security of the used authentica- ber of eIDAS related projects are publishing their work tion protocols and the web interfaces. as open-source. This openness enables future researchers to use techniques like white-box testing and static code The document published by the European Commis- analysis to complement our black-box approach and fur- sion on eIDAS-Node Security Considerations [13] de- ther increase the security of eID services. scribes the security best practices for eIDAS infrastruc- tures. However, this document mostly concentrates on best practices for typical web attacks, and summarizes Acknowledgements secure usage of HTTP headers and key storage. In our paper, we also provide an overview of SAML and XML- The research was supported by the European Com- relevant attacks, and summarize best practices for these mission through the FutureTrust project (grant 700542- technologies. Our study is based on many relevant rec- Future-Trust-H2020-DS-2015-1). The authors want to ommendations issued by OWASP [50, 49, 53, 45, 46] and thank the FutureTrust consortium for the valuable input the BSI [11, 10]. and helpful discussions provided. References [10] BSI. Technical guideline tr-03130 eid-server. part 1: Functional specification, Oct. 2017. [1] A RMANDO , A., C ARBONE , R., C OMPAGNA , L., C UELLAR , J., P ELLEGRINO , G., AND [11] BSI. Technische richtlinie tr-02102-1: Kryp- S ORNIOTTI , A. From multiple credentials to tographische verfahren: Empfehlungen und schlüs- browser-based single sign-on: Are we more secure? sellängen, Jan. 2018. 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RFC Conference on Computer and Communications Se- 7457 (Informational), Feb. 2015. curity (Vienna, Austria, 2016). [75] W ICHERS , D. Owasp top ten project. Tech. rep., X.509 Certificates. X.509 certificates are used in TLS as OWASP, Sept. 2015. well as in SAML. The best practices for processing and issuing X.509 certificates can be summarized as follows: [76] Z ALEWSKI , M. The tangled Web: A guide to se- I Trust establishment: X.509 certificates must be issued curing modern web applications. No Starch Press, by trusted authorities located in the truststore. Trust 2012. validation must be enforced. I Updating certificates: A process of updating certifi- cates before their expiration must be established. Appendices I Avoiding wildcard certificates: Certificates with wild- cards in the subject, common name or alternative A Best Current Practices names should be avoided. In this section, we give an overview of the best current practices which should be considered during the imple- A.2 Message Level Security mentation of SSO services. We provide existing BCP documents on this topic and an overview on existing pen- XML Parser. We strongly recommend disabling the fol- etration testing tools. lowing features within the parser: I DTD processing. This feature should be only acti- vated if it is needed. A.1 Transport Layer Security I Disabling the network access to the parser. Aside When enabling TLS, the following security checks need from processing DTDs, there are further possibilities to be considered: to call arbitrary URLs. By disabling network access, I Only secure TLS versions must be used – TLS 1.2 calling these URLs can no longer occur. and 1.3. TLS 1.0 and 1.1 may be used; however, they are not recommended. I If DTDs cannot be disabled, imposing restrictions on processing entities must be done by: (1.) Limiting the I Only secure cipher suites must be activated. Detailed memory capacity that a parser can allocate (2.) Dis- recommendations are provided by OWASP [52]. abling the SYSTEM and PUBLIC usage for all types of entities (internal and external parameter/general en- I Disabling TLS compression: Activating TLS com- tities). pression could make the running service implementa- tion vulnerable to the CRIME attack [52]. A comprehensive description of countermeasures and parser configurations is discussed by Späth et al. [65, 66]. There are different online services and tools for evalu- ating the security of TLS configurations, such as: SSL XML Signatures. The best practices for processing Labs,5 testssl.sh,6 or a TLS scanner based on TLS- XML Signatures in SAML messages can be depicted as Attacker.7 We recommend their usage after successful follows: TLS deployment. I Signature Exclusion Attacks: It must be ensured that the data is signed and that the signature has not been Cryptographic Key Lengths and Algorithms. The fol- removed. lowing cryptographic algorithms and key lengths are rel- evant for the deployment of SAML and TLS: I XML Signature Wrapping (XSW) Attack: During I Key lengths: RSA – 2048 bit; DH/DSS – 2048 bit; verification, it must be verified that the signature has ECDH/ECDSA – 256 bit been constructed over the processed data. More con- crete countermeasures are discussed by Somorovsky I Eliptic curves: secp256r1, secp384r1, secp521r1, et al. [62, 64, 46]. The XML Signature specification brainpoolP256r1, brainpoolP384r1, brainpoolP512r1 also provides additional recommended security con- I Hash algorithms: SHA-256, SHA-384, SHA-512, siderations [17]. SHA3-256, SHA3-384, SHA3-512 I Certificate Validation: The certificate used for signa- More details regarding the restrictions are published ture generation must be issued by a trusted IdP. in [11]. I XSLT: It is not allowed to trigger the XSLT processor 5 https://www.ssllabs.com/ssltest/ 6 https://testssl.sh/ during any XML Signature transformation. 7 https://github.com/RUB-NDS/TLS-Scanner XML Encryption. The newest XML Encryption stan- dard provides best practices for a secure standard deploy- Further security considerations can be found in [46]. ment. These can be summarized as follows [15]: I A SAML server implementing XML Encryption and A.3 Web Application Security XML Signature should use at least two distinct certifi- cates. It is good cryptographic practice to use different In this section, we provide a summary of the security keys for different purposes; in this case, for decryption relevant HTTP headers which should be configured to of encrypted XML contents and for signing SAML strengthen the communication between the provider and messages. If not implemented, backwards compati- the End-User’s UA. A comprehensive summary is pro- bility attacks could be executed [26]. vided by OWASP in [49]. I To protect against adaptive chosen-ciphertext attacks HTTP Session Cookies. The security of session cook- on symmetric encryption schemes [29], authenticated ies is essential for the correct End-User authentication. encryption schemes should be used. XML Encryp- In the event of misconfiguration, an attacker could hi- tion 1.1 provides the AES-GCM algorithms. Other jack the authenticated HTTP session of an End-User and algorithms should not be supported. If they are sup- impersonate them. We consider the following cookie ported, it must be ensured the attacker cannot enforce flags as required: secure and HttpOnly [51]. In addi- processing of unauthenticated XML ciphertexts by the tion, samesite cookies can be applied to reduce the risk server [62]. against CSRF attacks. A common pitfall lies within the header’s domain di- I To protect against adaptive chosen-ciphertext attacks rective, which broadens the cookie’s scope to include the on asymmetric encryption schemes [27], secure en- originating host’s sub-domains and may lead to unin- cryption schemes must be used: RSA-OAEP and ellip- tended data exposure. The other cookie-scoping direc- tic curve Diffie-Hellman. Other algorithms should not tive, path, should not be used for security relevant scop- be supported. If they are supported, specific counter- ing [76]. measures must be applied, most importantly, against Clickjacking/UI-Redressing. The main goal of the pro- Bleichenbacher’s attack [62]. posed countermeasures is to prevent framing a website Further security best practices are located in the XML within another one. By this means, attacks such as Click- Encryption specification [15]. jacking and UI-redressing can be mitigated. They can SAML Validation. The following aspects must be con- be prevented by using one of the following techniques: sidered by validating the SAMLRequest: X-Frame-Options HTTP header, the Content-Security- Policy, or JavaScript code [47]. I AssertionConsumerServiceURL: The URL must be checked against a whitelist with pre-defined URLs. HTTP Strict Transport Security. Securing the com- Usually, this whitelist is provided by the metadata of munication between the UA and the server is essential the provider. with respect to eavesdropping attacks. For this purpose, the use of TLS is imperative. By using the Strict- I Freshness validation: All timestamps located in the Transport-Security header the server can force the UA message must be valid. to always use TLS. In this way, the risk against man-in- The following security aspects are relevant to the middle attacks can be reduced. SAMLResponse: Content Security Policy (CSP). The Content Security I Issuer validation: The SAML issuer (IdP) must be Policy is a powerful construct. The specified directives validated against a whitelist of trusted IdPs allowed and configuration possibilities provide the means to mit- to authenticate the users. igate XSS vulnerabilities, protect against Clickjacking, Mixed-Content inclusion, and generally restrict client- I Recipient validation: The SAML recipient must be side resource inclusion [45, 44, 74]. However, the CSP is validated by comparing the value with the expected a defense-in-depth approach that requires additional ef- recipient of this message. In case of deviations, the fort from web-developers. As an example, neither in-line message must be rejected. scripts nor event handlers can be used without additional I Freshness validation: To prevent replay attacks, the measures. signed timestamps must be validated. Specific configuration of a web application’s CSP de- pends on multiple factors. These factors include: the I InResponseTo validation: It must be checked whether current version of the CSP, design and architecture of the content of the InResponseTo element is identical to the website, required external resources from different the content of the ID sent in the AuthnReq. Otherwise, domains, and the general complexity of the web appli- CSRF attacks can be applied. cation. Therefore, it is not possible to give a general- Figure 4: DTD-Attacker is a novel enhancement of the Burp plugin EsPReSSO. The manual mode provides predefined attack vectors which can easily be configured in every detail. purpose recommendation of a good policy. SAML Endpoints URL Tag Tool Support. Several software products can support de- velopers in evaluating their applications. The ZAP Con- eunode.qa.sveidas.se/idp/profile/SAML2/POST/SSO H1 nonode.eidastest.se/EidasNode/ColleagueRequest H2 tent Security Policy Scanner extension is able to provide nonode.eidastest.se/PS-IdP/AuthenticateCitizen H3 an automated analysis of the security headers, evaluate nonode.eidastest.se/EidasNode/IdpResponse H4 the applied Content Security Policy [48], and find poten- eunode.qa.sveidas.se/idp/extauth/saml2/post H5 tial XSS, CSRF, and Clickjacking attacks. Similar ex- eunode.eidastest.se/con-sp/assertionconsumer H6 tensions exist for Burp-Suite and w3af [55] [72]. The authors of [74] provide an online tool for CSP evaluation Table 2: Mapping of SAML endpoint URLs to tags used [73]. in Table 3. B Swedish eIDAS Pilot - Message Flow attack vectors and easily modify the provided templates as required. The authentication scenario depicted in Figure 3 assumes that a Swedish SP eunode.eidastes.se/con-sp requests D Security Evaluation - Summary authentication from a user in Test Country XX by reach- ing out to the eIDAS Connector (eunode.qa.sveidas.se A summary of our results is given in Table 3 and Table 2 ). The AuthnReq is relayed to the eIDAS Proxy-Service for the security analysis performed on the Swedish eI- at nonode.eidastest.se/EidasNode and eventually for- DAS demo service. warded to Test Country XX’s IdP. After successful user authentication, as simulated in the test-pilot, the Authn- Response is delivered backwards through the same chan- nel. Explicit user consent is required before the Authn- Response is released by the Proxy-Service. C DTD-Attacker in EsPReSSO Figure 4 presents the manual interface to the novel DTD- Attacker. The user can choose from a variety of different Transport Layer Security Message Level Security Web Application Security k Attac s r ct k ntity racle rves ites on ache e E edire E l Attac cking leed a rs ja e ing O id C u DL tb rt R WN Versi er Su henb ay F ificat rn SAML TLS Ciph Cert DRO POO Bleic Padd Inval Hear 0/ Sig CF XSW XEA Repl TRC XSLT Exte XSS CSR Click Cove Head Endpoint H1 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 H2 * 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 71 3 32 H3 * 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 71 3 32 H4 * 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 71 3 32 H5 3 3 3 3 3 3 3 3 3 3 3 3 34 3 3 3 3 3 3 3 3 3 H6 * 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 7 3 33 3 3 3 * Shared TLS Endpoint of eunode.eidastest.se and nonode.eidastest.se (virtual hosting with shared certificate) 1 Attack mitigated in newer versions 2 Missing X-Frame-Options header and frame-ancestor directive in CSP 3 RelayState parameter not properly bound to session 4 Encrypts Assertion using AES128-CBC (no ciphertext authentication) 3= Not vulnerable, 7= Vulnerable, 3= Weak configuration, 7= Vulnerability mitigated H1-H6: See Table 2 for specific SAML endpoint URLs. Table 3: Results of the security evaluation of the Swedish eIDAS pilot. User authentication was simulated using the provided IdP of fictitious Test Country XX. SP eIDAS Connector eIDAS Proxy & IdP User UA eunode.eidastest.se eunode.qa.sveidas.se nonode.eidastest.se /con-sp/login (1.) Login request (2.) AuthnRequest (i) /idp/profile/SAML2/POST/SSO (3.) AuthnReq (ii) /EidasNode/ColleagueRequest (4.) AuthnReq (iii) /PS-IdP/AuthenticateCitizen (5.) Authentication (6.) SAMLResponse (i) /EidasNode/IdPResponse (7.) Consent (8.) SAMLResponse (ii) /idp/extauth/saml2/post (9.) SAMLResponse (iii) /con-sp/assertionconsumer Figure 3: Message flow of an authentication process at the Swedish eIDAS pilot. The eIDAS connector represents the receiving member-state (Sweden) while the Proxy-Service and IdP represent the sending member-state (Test Country XX).