CVE-2016-0755

The ConnectionExists function in lib/url.c in libcurl before 7.47.0 does not properly re-use NTLM-authenticated proxy connections, which might allow remote attackers to authenticate as other users via a request, a similar issue to CVE-2014-0015.

libcurl reuses NTLM-authenticated proxy connections without properly making sure that the connection was authenticated with the same credentials as set for this transfer.

libcurl maintains a pool of connections after a transfer has completed. The pool of connections is then gone through when a new transfer is requested and if there is a live connection available that can be reused, it is preferred instead of creating a new one.

Since NTLM-based authentication is connection oriented instead of request oriented as other HTTP based authentication, it is important that only connections that have been authenticated with the correct username + password are reused. This was done properly for server connections already, but libcurl failed to do it properly for proxy connections using NTLM.

A libcurl application can easily switch user credentials used for a proxy connection between two requests, and that subsequent transfer then MUST make libcurl use another connection. libcurl previously failed to do so.

The effects of this flaw, is that the application could be reusing a proxy connection using the previously used credentials and thus it could be given to or prevented access from resources that it was not intended to.

This problem is similar to CVE-2014-0015, which was for direct server connections while this is for proxy connections.

libcurl before 7.47.0 will reuse NTLM-authenticated proxy connections without properly making sure that the connection was authenticated with the same credentials as set for this transfer. The effect of this flaw is that the application could be reusing a proxy connection using the previously used credentials and thus it could be given to or prevented access from resources that it wasn't intended to (CVE-2016-0755).

These are all security issues fixed in the curl-7.51.0-1.1 package on the GA media of openSUSE Tumbleweed.

This update for curl fixes the following issues:

• CVE-2016-0755: libcurl would reuse NTLM-authenticated proxy connections without properly making sure that the connection was authenticated with the same credentials as set for this transfer (bsc#962983)

The following non-security bugs were fixed:

• bsc#936676: secure_getenv or __secure_getenv may not be detected correctly at build time

The following tracked bugs only affect the test suite:

• bsc#962996: Expired cookie in test 46 caused test failures
• bsc#934333: Curl test suite was not run, is now enabled during build

This update for curl fixes the following issues:

• CVE-2016-0755: libcurl would reuse NTLM-authenticated proxy connections without properly making sure that the connection was authenticated with the same credentials as set for this transfer (bsc#962983)

The following non-security bugs were fixed:

• bsc#926511: Check for errors on the control connection during FTP transfers

The following tracked bugs only affect the test suite:

• bsc#962996: Expired cookie in test 46 caused test failures

This rebuild for sles11sp4-docker-image fixes several important security issues done in libraries contained inside, for glibc, openssl, curl and openldap2.

glibc security fixes:

• CVE-2015-7547: A stack-based buffer overflow in getaddrinfo allowed remote attackers to cause a crash or execute arbitrary code via crafted and timed DNS responses (bsc#961721)
• CVE-2015-8777: Insufficient checking of LD_POINTER_GUARD environment variable allowed local attackers to bypass the pointer guarding protection of the dynamic loader on set-user-ID and set-group-ID programs (bsc#950944)
• CVE-2015-8776: Out-of-range time values passed to the strftime function may cause it to crash, leading to a denial of service, or potentially disclosure information (bsc#962736)
• CVE-2015-8778: Integer overflow in hcreate and hcreate_r could have caused an out-of-bound memory access. leading to application crashes or, potentially, arbitrary code execution (bsc#962737)
• CVE-2014-9761: A stack overflow (unbounded alloca) could have caused applications which process long strings with the nan function to crash or, potentially, execute arbitrary code. (bsc#962738)
• CVE-2015-8779: A stack overflow (unbounded alloca) in the catopen function could have caused applications which pass long strings to the catopen function to crash or, potentially execute arbitrary code. (bsc#962739)

glibc non-security bugfixes:

• bsc#930721: Accept leading and trailing spaces in getdate input string
• bsc#942317: Recognize power8 platform
• bsc#950944: Always enable pointer guard
• bsc#956988: Fix deadlock in __dl_iterate_phdr

openssl security issues fixed:

• CVE-2016-0800 aka the 'DROWN' attack (bsc#968046): OpenSSL was vulnerable to a cross-protocol attack that could lead to decryption of TLS sessions by using a server supporting SSLv2 and EXPORT cipher suites as a Bleichenbacher RSA padding oracle.

  This update changes the openssl library to:

  • Disable SSLv2 protocol support by default.

    This can be overridden by setting the environment variable 'OPENSSL_ALLOW_SSL2' or by using SSL_CTX_clear_options using the SSL_OP_NO_SSLv2 flag.

    Note that various services and clients had already disabled SSL protocol 2 by default previously.

  • Disable all weak EXPORT ciphers by default. These can be reenabled if required by old legacy software using the environment variable 'OPENSSL_ALLOW_EXPORT'.

• CVE-2016-0705 (bnc#968047): A double free() bug in the DSA ASN1 parser code was fixed that could be abused to facilitate a denial-of-service attack.

• CVE-2016-0797 (bnc#968048): The BN_hex2bn() and BN_dec2bn() functions had a bug that could result in an attempt to de-reference a NULL pointer leading to crashes. This could have security consequences if these functions were ever called by user applications with large untrusted hex/decimal data. Also, internal usage of these functions in OpenSSL uses data from config files or application command line arguments. If user developed applications generated config file data based on untrusted data, then this could have had security consequences as well.

• CVE-2016-0799 (bnc#968374) On many 64 bit systems, the internal fmtstr() and doapr_outch() functions could miscalculate the length of a string and attempt to access out-of-bounds memory locations. These problems could have enabled attacks where large amounts of untrusted data is passed to the BIO_*printf functions. If applications use these functions in this way then they could have been vulnerable. OpenSSL itself uses these functions when printing out human-readable dumps of ASN.1 data. Therefore applications that print this data could have been vulnerable if the data is from untrusted sources. OpenSSL command line applications could also have been vulnerable when they print out ASN.1 data, or if untrusted data is passed as command line arguments. Libssl is not considered directly vulnerable.

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Isaac Boukris discovered that curl could incorrectly re-use NTLM proxy credentials when subsequently connecting to the same host.