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By Date By Thread CVE-2015-5372 SAML SP Authentication Bypass in nevisAuth From: Antoine Neuenschwander <Antoine.Neuenschwander () csnc ch>

Date: Mon, 21 Sep 2015 12:02:27 +0000

############################################################# # # COMPASS SECURITY ADVISORY # http://www.csnc.ch/en/downloads/advisories.html # ############################################################# # # Product: nevisAuth [1] # Vendor: AdNovum [2] # CVD ID: CVE-2015-5372 # Subject: Authentication Bypass # Risk: Critical # Effect: Remotely exploitable # Authors: Antoine Neuenschwander (antoine.neuenschwander () csnc ch) # Roland Bischofberger (roland.bischofberger () csnc ch) # Date: 2015-09-21 # ############################################################# Introduction: ------------- nevisAuth implements strong user and system authentication for identity and access management solutions. It offers secure execution of multi-step authentication and is able to dynamically adjust authentication strengths. nevisAuth is highly flexible, easily integrated and supports plug-ins to various authentication methods. [1] Security Analysts of Compass Security Schweiz AG [3] discovered a security flaw in the SAML 2.0 implementation of nevisAuth, which allows an attacker to bypass the signature validation of security assertions, and therefore impersonate other users. Affected: --------- nevisAuth since v4.13.0.0 (2012-11-21) A security fix was released with version v4.18.3.1 (2015-07-02) Technical Description: ---------------------- When configured as a SAML 2.0 service provider (SP), nevisAuth authenticates users based on security assertions issued and signed by a trusted identity provider (IdP). An assertion contains various fields about the user or subject being authenticated, e.g. a name identifier (NameID), various attributes and timestamps. Trust is based on the IdP's certificate, which is used to validate the digital signature of security assertions. In a setup where security assertions are conveyed via User-Agent (i.e when using HTTP POST Binding), it is possible to forge and inject new assertions based on data intercepted during a valid past authentication process. To achieve this, the signing certificate is extracted from the assertion and then cloned to reflect all X.509 data fields. A new public/private key pair is generated. The public key is inserted into the certificate and the private key is used to sign it. The signing certificate in the security assertion is now replaced with its rogue copy. The attacker can then modify arbitrary values of the assertion, for example the NameID. Finally, the assertion is signed with the cloned certificate. Due to a flaw in affected versions of nevisAuth, it is possible to bypass validation of security assertions by presenting the system with forged assertions as described above. In consequence, an attacker can impersonate other users. More details on the attack can be found in [4]. Workaround / Fix: ----------------- AdNovum released a security fix in nevisAuth v4.18.3.1 (2015-07-02) to address this issue. Alternatively, when using HTTP POST Binding, use encrypted security assertions for transmission via the User-Agent. Or completely avoid transmitting security assertions over insecure channels by using HTTP Artifact Binding. Timeline: --------- 2015-06-26: Discovered vulnerability 2015-06-30: CVE ID requested 2015-07-01: Initial vendor notification 2015-07-02: Vendor confirmed security issue 2015-07-03: Vendor released security fix & guidance to its customers 2015-07-06: CVE ID assigned 2015-09-21: Public disclosure Acknowledgements: ----------------- This vulnerability was discovered using the SAMLRaider Plugin [5] for Burp Suite [6], developed by Roland Bischofberger (roland.bischofberger () csnc ch) and Emanuel Duss (emanuel.duss () gmail com). References: ----------- [1]: https://www.nevis.ch/en/products/nevisauth-authentication-service.html [2]: http://www.adnovum.ch/en/ [3]: http://www.csnc.ch/advisories [4]: http://blog.csnc.ch/2015/09/saml-sp-authentication-bypass-vulnerability-in-nevisauth [5]: https://github.com/SAMLRaider/SAMLRaider [6]: http://portswigger.net/burp/ _______________________________________________ Sent through the Full Disclosure mailing list https://nmap.org/mailman/listinfo/fulldisclosure Web Archives & RSS: http://seclists.org/fulldisclosure/ By Date By Thread Current thread: CVE-2015-5372 SAML SP Authentication Bypass in nevisAuth Antoine Neuenschwander (Sep 23)