Product Information - ------------------- Check Point Session Authentication agent is a service that is installed on endpoint system in order to communicate with security gateway and allow it to request and obtain user's credentials. Session Authentication is a part of Legacy Authentication suite which provides different authentication methods to allow or deny access to network resources. R76 Security Gateway Technical Administration Guide[1] defines typical Session Authentication operation in the following way: 1. The user initiates a connection directly to the server 2. The Security Gateway intercepts the connection 3. The Session Authentication agent challenges the user for authentication data and returns this information to the gateway 4. If the authentication is successful, the Security Gateway allows the connection to pass through the gateway and continue to the target server Issue description - ----------------- Check Point Session Authentication agent version 4.1 and higher contains a flaw which is caused by lack of peer authentication in SSL communication. Encrypted communication between agent and security gateway has been introduced due to several issues (e.g. [2], [3]) which were revealed in the previous versions (4.0 and lower) of the product. Research showed that it is still possible to exploit previously known vulnerabilities - gateway impersonation and credential stealing - even though communication between agent and security gateway is utilizing SSL. Communication between Session Authentication agent and security gateway is performed using proprietary protocol. Since version 4.1 this communication scheme uses SSL as an underlying protocol to enable encryption of both protocol commands and user provided data. When SSL communication is negotiated between gateway and agent following cipher suites are visible in SSL Client Hello message as supported by Session Authentication agent: TLS_DH_anon_EXPORT_WITH_RC4_40_MD5 TLS_DH_anon_WITH_RC4_128_MD5 TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA TLS_DH_anon_WITH_DES_CBC_SHA TLS_DH_anon_WITH_3DES_EDE_CBC_SHA RFC2246 refers to listed cipher suites: "The following cipher suites are used for completely anonymous Diffie-Hellman communications in which neither party is authenticated. Note that this mode is vulnerable to man-in-the-middle attacks and is therefore deprecated." Taking into account above information it's possible to connect to Session Authentication agent from attacker's machine, initiate SSL-based communication, pass SSL handshake without being authenticated and use encrypted channel to control agent (e.g. prompt user for login and password). For attack to be successful attacker's machine must be allowed to connect to machine on which agent is running. Newer versions of Session Authentication agent include option to define three IP addresses which are allowed to issue authentication requests to agent. When this option is used it limits possibility of exploitation. Agent software has also "Allow any IP" option - when enabled attacker doesn't need to take additional measures in order to be able to connect to agent. Proof of Concept - ---------------- Attached PoC script simulates security gateway and allows credential stealing to be performed over encrypted communication channel against Session Authentication agent version 4.1 or higher. Affected versions - ----------------- Check Point Session Authentication agent, version 4.1 and higher Vendor response - --------------- Vendor has been informed about the issue on 8/8/2013. On 14/8/2013 vendor informed about expected fix date: 15/10/2013. On 28/10/2013 vendor informed that due to small user base and introduction of the Identity Awareness Software Blade[4] legacy session authentication will be deprecated in the major release of 2014. Additionally vendor published SecureKnowledge article[5]. Credits - ------- It should be noted that this finding is partially based on work of individuals who reported issues in the previous versions of Session Authentication agent as referenced in [2] and [3]. References - ---------- [1] https://sc1.checkpoint.com/documents/R76/CP_R76_SGW_WebAdmin/6721.htm [2] http://www.securityfocus.com/bid/1661/info [3] http://osvdb.org/show/osvdb/84985 [4] https://www.checkpoint.com/products/identity-awareness-software-blade/ [5] https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk98263