SEC Consult SA-20140411-0 :: Multiple vulnerabilities in Plex Media Server


SEC Consult Vulnerability Lab Security Advisory < 20140411-0 > ======================================================================= title: Multiple vulnerabilities product: Plex Media Server vulnerable version: confirmed in fixed version: none impact: High homepage: http://www.plex.tv found: 2014-02-06 by: Stefan Viehbock SEC Consult Vulnerability Lab https://www.sec-consult.com ======================================================================= Vendor/product description: ----------------------------- "Plex is a media player system consisting of a player application with a 10-foot user interface and an associated media server. It is available for Mac OS X, Linux, and Microsoft Windows." URL: https://en.wikipedia.org/wiki/Plex_(software) Vulnerability overview/description: ----------------------------------- 1. Use of plain text protocols Plain text protocols are used in various places. The Plex App Store fetches App listings and App code via HTTP. This enables active attackers (MITM) to run code in the context of the Plex Media Server. The Plex "Remote" functionality uses HTTP as well. This enables passive attackers to gain access to the session token in order to access the Plex Media Server web interface. 2. Insecure use of SSL/TLS The Plex Media Server offers HTTPS access via TCP port 32443. The certificate that is used is issued by "DigiCert Secure Server CA" which is a commonly trusted certificate authority. The certificate is issued to "*.hub.plex.tv". The private key for this certificate is included in the Plex software and can be extracted easily. The DNS server behind "hub.plex.tv" is configured to resolve subdomains relative to the IP indicated in the name. Eg. 1-2-3-4.hub.plex.tv resolves to the IP This enables all Plex Media Servers to offer SSL/TLS services out of the box without prior configuration and using a valid certificate. For this to work the corresponding private key has to be included in the software. This enables active attackers to execute SSL MITM attacks as the private key is effectively public. This mechanism can be abused by malicious entities to provide services on arbitrary IPs via SSL/TLS as well. One example would be to run a watering-hole-style attack by abusing the reputation of the Plex domain as well as the valid certificate. As this mechanism requires the private key to be compromised it should not be used in the first place. The certificate should be revoked. Note: The Plex Media Server seems to offer DHE ciphers (DHE_RSA). The perfect forward secrecy (PFS) properties of these KEX ciphers would prevent passive attackers from decrypting communication. 3. Unauthenticated information disclosure through stack traces Python stack traces are included in the responses for some requests. This allows an attacker to gain information about the target operating system, local file paths etc. which can be used in further attacks. 4. Cross Site Request Forgery The application does not implement any kind of CSRF protection. Quite the contrary, security mechanisms that would minimize the extent of CSRF attacks are deliberately disabled. The Plex Media Server explicitly allows all sources (wildcard) in cross-server resource sharing (CORS) as well as in cross-domain policy restrictions (Flash and Silverlight). This enables attackers to retrieve arbitrary content (eg. the master token) from the server. Proof of concept: ----------------- 1. Use of plain text protocols No proof of concept needed. The Plex App store is located at: http://nine.plugins.plexapp.com 2. Insecure use of SSL/TLS The private key for the "*.hub.plex.tv" certificate: -----BEGIN RSA PRIVATE KEY----- MIIEowIBAAKCAQEAo0zj2qWd2JuWDSDmBWeDA0luMgPPPZeT8SLf5tzuK5lcvHYj WHnH4J3ElSTT/X2O+2rUfELZAnduCWOWHChuhXXUlRchfwjDn4WLXYYYnVh3Rdgj mwneL3jos/A2f+54gBRJSySa64FqeW/henh2fMpK+SA8yEqZR0UeVtm9tmQmte7D T+UZOndHT7GsE72eynJJGA43q6fuyJ5IpPDk0Xr0prvVyePmNvIwAEROd8sEqdgJ ZSczl2ANngHY4I7BYtrmrtT+1lch2FwJ5dcyGhXhX/+vVzGxYLaetoMmi4gNHKrU SeQ60X8xBBgPMcFvDpNkNS0/Kp7+XIff6ukC0wIDAQABAoIBAGG5vhI3UsMyORYa Pg216J2q8BtWVEuTzqFcMYpDZPUKjojqWjS0jH1LbT2kEIl+/nZPdGH4z02+k0dj JY4sVBficBnZAd64K/nnPYP2n/xp2Ncfhg9eVG0senZUpwjgeZSMj2A8w8l0ZXfP EKzuMlpz5XI5bKagniIcpw9qtzHSwOBgSedDkOxpiewFqwXdGptXU5xQGhcGEZbY YJI+8pL8l6wJ3iZ3djW2RosWioOf/9iKOU1G+ECb9GwTuY7HzXkQ5WSJRRAmdvep 4TLprE9RXo9oWiJZJUvNrCD5/Gw+D3pRlFoGsG/Txp7UySpAU2RNs9j5LrorTIww P8guE4ECgYEA0PhaYCs82bN95FksOzZyJqSp5MpFfUrb3+DQnEgIK12WMwY7Mbhl TyhT4KNgKkVKGjKtF6AZKwnmMMuoVhsxwoepct/qrNL7rT79m4JMfEH2HWmDbi1G yYQmOqvbr8WXlDQvraiSYDpYhXkHwvBJ5ssTxRW6VG0p6VZKilJfHjECgYEAyA1P LubY6hJ8OvQfNCnsnJ5/r0qnItIBV8vT5B1qMbmO5GZzrS2hLiSZX6wStanHn3NQ 8oEJ7J5eBgWMdxV1Clasg8cXX9DJdX/AEt8E7qa284CiyBP9mieVEJRdslBGgPKA BBBySpu4AO3dToiUFb6zSmGaSp303lrusaCy3EMCgYBx4ic+qdGrwwok3AQi8PUc 4jhEm4drVNSnGdoWkZsCJyqn/Alee2Oa1BuCHQdXghN0W5HBglq0/dwZU6QV6RQh M9XA6Q73yLOoIuALU+NjBH+gX9RkwwAE6qP67ZX4IPMOrbIeLfQ3xRRhCSiVsGZW BO5tRf4Z7LQemgxdfa6gwQKBgQC3Cx6Bnq2o9wL+ejI264lZANl5zYfCH38lExYs 6hEpsEwjhe6f7VlGPCyt0mdIGzHRHpVZXmJzQ7BqOBd/On3d2NJ+vOMRQ5uhzCM1 4SPFLXvGr9PB2DC6JS+KfQaCSltITxp9HYNF6tdg2kQdQHCmuNeZ3lZrob3U2kT+ +DfPuwKBgBMAgkJiPx+4kuzdMR2+GWQhttLEB64w05pcR4LeXjeO8r7tICo6RZGU WPd9o65yFJtVUEipVWHaPWe/86Y4YhlZbPKAdEwSSdalagEHC9YUnfsB4TOZUb7m HAM4+jeGlbIaKvPkeXYbAOJS46yogiFUAYZTdpJ6/viS8UyiJPLx -----END RSA PRIVATE KEY----- 3. Unauthenticated information disclosure through stack traces The following request causes an exception in the application logic. GET /system/proxy HTTP/1.1 Host: <HOST> X-Plex-Url: http://my.plexapp.com/NONEXISTANT A stack trace is included in the server's response: HTTP/1.0 500 Internal Server Error Content-Length: 3437 Content-Type: application/xml Cache-Control: no-cache X-Plex-Protocol: 1.0 <?xml version='1.0' encoding='utf-8'?> <Response code="2000" status="HTTPError: "> <Traceback>Traceback (most recent call last): File "C:\Users\user\AppData\Local\Plex Media Server\Plug-ins\Framework.bundle\Contents\Resources\Versions\2\Python\Framework\components\runtime.py", line 845, in handle_request result = f(**d) [...] File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 629, in http_error_302 return self.parent.open(new, timeout=req.timeout) File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 410, in open response = meth(req, response) File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 523, in http_response 'http', request, response, code, msg, hdrs) File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 448, in error return self._call_chain(*args) File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 382, in _call_chain result = func(*args) File "C:\Program Files (x86)\Plex\Plex Media Server\python27.zip\urllib2.py", line 531, in http_error_default raise HTTPError(req.get_full_url(), code, msg, hdrs, fp) HTTPError: HTTP Error 404: Not Found </Traceback> </Response> 4. Cross Site Request Forgery No CSRF tokens are implemented. The files crossdomain.xml and clientaccesspolicy.xml in the webroot allow both Silverlight and Flash to send arbitrary requests to the server and receive responses. Some pages respond with the "Access-Control-Allow-Origin: *" headers. Vulnerable / tested versions: ----------------------------- The vulnerabilities have been verified to exist in Plex Media Server version Vendor contact timeline: ------------------------ 2014-02-09: Contacting vendor through elan@plexapp.com and requesting encryption keys. 2014-02-10: Vendor provides encryption keys. 2014-02-10: Sending advisory and proof of concept exploit. 2014-02-10: Vendor acknowledges receipt of advisory. 2014-02-17: Requesting status update. 2014-02-21: Requesting clarification regarding fixed version. 2014-02-21: Vendors provides further information about reported vulnerabilities. 2014-02-24: Requesting clarification regarding patching status and setting deadline (2014-03-24). 2014-02-25: Vendor announces that the certificate will be revoked soon. 2014-04-04: Requesting status update. 2014-04-05: Vendor confirms that certificate has been revoked. No other fixes have been implemented. 2014-04-11: SEC Consult releases security advisory. Solution: --------- No solution is available. Workaround: ----------- No workaround available. Advisory URL: ------------- https://www.sec-consult.com/en/Vulnerability-Lab/Advisories.htm ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SEC Consult Vulnerability Lab SEC Consult Vienna - Bangkok - Frankfurt/Main - Montreal - Singapore - Vilnius Headquarter: Mooslackengasse 17, 1190 Vienna, Austria Phone: +43 1 8903043 0 Fax: +43 1 8903043 15 Mail: research at sec-consult dot com Web: https://www.sec-consult.com Blog: http://blog.sec-consult.com Twitter: https://twitter.com/sec_consult Interested in working with the experts of SEC Consult? Write to career@sec-consult.com EOF Stefan Viehbock / @2014