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cURL > Docs > Security > libcurl re-use of wrong HTTP NTLM connection

libcurl re-use of wrong HTTP NTLM connection

                 libcurl re-use of wrong HTTP NTLM connection
                 ============================================
 
Project cURL Security Advisory, January 29th 2014
http://curl.haxx.se/docs/security.html
 
1. VULNERABILITY
 
  libcurl can in some circumstances re-use the wrong connection when asked to
  do an NTLM-authenticated HTTP or HTTPS request.
 
  libcurl features a pool of recent connections so that subsequent requests
  can re-use an existing connection to avoid overhead.
 
  When re-using a connection a range of criterion must first be met. Due to a
  logical error in the code, a request that was issued by an application could
  wrongfully re-use an existing connection to the same server that was
  authenticated using different credentials. One underlying reason being that
  NTLM authenticates connections and not requests, contrary to how HTTP is
  designed to work and how other authentication methods work.
 
  An application that allows NTLM and another auth method (the bug only
  triggers if more than one auth method is asked for) to a server (that
  responds wanting NTLM) with user1:password1 and then does another operation
  to the same server with user2:password2 (when the previous connection was
  left alive) - the second request will re-use the same connection and since
  it'll then see that the NTLM negotiation is already made, it will just send
  the request over that connection thinking it uses 'user2' credentials when
  it is in fact still using the connection authenticated for user1...
 
  The set of auth methods to use is set with CURLOPT_HTTPAUTH.
 
  Two common auth defines in libcurl are CURLAUTH_ANY and CURLAUTH_ANYSAFE.
  Both of them ask for NTLM and other methods and can therefore trigger this
  problem.
 
  Applications can disable libcurl's re-use of connections and thus mitigate
  this problem, by using one of the following libcurl options to alter how
  connections are or aren't re-used: CURLOPT_FRESH_CONNECT,
  CURLOPT_MAXCONNECTS and CURLMOPT_MAX_HOST_CONNECTIONS (if using curl_multi
  API).
 
  The Common Vulnerabilities and Exposures (CVE) project has assigned the name
  CVE-2014-0015 to this issue.
 
2. AFFECTED VERSIONS
 
  This flaw has existed ever since libcurl started to support NTLM, although
  the code has been restructured a few times over the years so the mistake has
  altered shape over the years.
 
  Affected versions: from libcurl 7.10.6 to and including 7.34.0
  Not affected versions: libcurl before 7.10.6 and >= 7.35.0
 
  libcurl is used by many applications, but not always advertised as such!
 
3. THE SOLUTION
 
  libcurl 7.35.0 makes sure that connections that may use NTLM cannot re-use
  another NTLM-using connection unless the credentials match.
 
  A patch for this problem (that applies to libcurl >= 7.28.0) is
  available at:
 
    https://github.com/bagder/curl/commit/8ae35102c43d8d
 
  A patch that applies for 7.27.0 is available at:
 
    http://curl.haxx.se/CVE-2014-0015-7-27.patch
 
  This fix is already committed to the public source code repository because
  the full security impact wasn't properly realized until after the fact.
 
4. RECOMMENDATIONS
 
  We suggest you take one of the following actions immediately, in order of
  preference:
 
  A - Upgrade to curl and libcurl 7.35.0
 
  B - Apply the patch and rebuild libcurl
 
  C - Avoid using HTTP NTLM in your application, or make sure to *only*
      specify NTLM as the requested authentication method.
 
5. TIME LINE
 
  It was reported to the curl project on January 7th 2014. We contacted
  distros@openwall on January 14th.
 
  libcurl 7.35.0 was released on January 29th 2014, coordinated with the
  publication of this advisory.
 
 
6. CREDITS
 
  Bug originally reported by Paras Sethia. The security impact of it was
  flagged by Yehezkel Horowitz.
 
  Thanks a lot!

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