** Description changed: [Impact] When connecting to a server using SASL, memcached_sasl_authenticate_connection() reads the list of supported mechanisms [1] from the server via the command PROTOCOL_BINARY_CMD_SASL_LIST_MECHS. The server's response is a string containing supported authentication mechanisms, which gets stored into the (uninitialized) destination buffer without null termination [2]. The buffer then gets passed to sasl_client_start [3] which treats it as a null-terminated string [4], reading uninitialised bytes in the buffer. As the buffer lives on the stack, an attacker that can put strings on the stack before the connection gets made, might be able to tamper with the authentication. [1] libmemcached/sasl.cc:174 [2] libmemcached/response.cc:619 [1] libmemcached/sasl.cc:231 [3] http://linux.die.net/man/3/sasl_client_start + [Test Case] - There is no known reliable reproducer. + This bug is difficult to reproduce since it depends on the contents of the stack. + However, here is a test case using the fix on Bionic that shows that this fix does not cause any problems. + + For testing you need + + 1) A memcached server. + You can setup one by following the instructions in [1], + or (what I did) create one in the cloud [2]. + + 2) A client test program to connect to the memcached server. + One can be found in [3]. + This simple test connects to a memcache server and test basic get/set operations. + Copy paste the C code into a file (sals_test.c) and compile with : + gcc -o sasl_test -O2 sasl_test.c -lmemcached -pthread + + 3) On a machine with the updated version of libmemcached in which the fix is applied : + jo@bionic-vm:~$ dpkg -l | grep libmemcached + ii libhashkit-dev:amd64 1.0.18-4.2ubuntu0.18.04.1 amd64 libmemcached hashing functions and algorithms (development files) + ii libhashkit2:amd64 1.0.18-4.2ubuntu0.18.04.1 amd64 libmemcached hashing functions and algorithms + ii libmemcached-dbg:amd64 1.0.18-4.2ubuntu0.18.04.1 amd64 Debug Symbols for libmemcached + ii libmemcached-dev:amd64 1.0.18-4.2ubuntu0.18.04.1 amd64 C and C++ client library to the memcached server (development files) + ii libmemcached-tools 1.0.18-4.2ubuntu0.18.04.1 amd64 Commandline tools for talking to memcached via libmemcached + ii libmemcached11:amd64 1.0.18-4.2ubuntu0.18.04.1 amd64 C and C++ client library to the memcached server + ii libmemcachedutil2:amd64 1.0.18-4.2ubuntu0.18.04.1 amd64 library implementing connection pooling for libmemcached + + Run the sals_test binary : + #./sasl_test [username] [password] [server] + + In my case using the credentials and the server created in step 1 : + jo@bionic-vm:~$ ./sasl_test 88BAB0 1A99094B77C8935ED9F1461C767DB1F9 mc2.dev.eu.ec2.memcachier.com + Get/Set success! + + [1] https://blog.couchbase.com/sasl-memcached-now-available/ + [2] https://www.memcachier.com/ + [3] https://blog.memcachier.com/2014/11/05/ubuntu-libmemcached-and-sasl-support/ [Regression Potential] This fix initialises the buffer to 0. Any potential regression may include failure of the authentication when using SASL. [Other Info] This bug affects trusty and later. * rmadison: - libmemcached | 1.0.8-1ubuntu2 | trusty | source - libmemcached | 1.0.18-4.1 | xenial | source - libmemcached | 1.0.18-4.2 | bionic | source - libmemcached | 1.0.18-4.2 | cosmic | source - libmemcached | 1.0.18-4.2 | disco | source + libmemcached | 1.0.8-1ubuntu2 | trusty | source + libmemcached | 1.0.18-4.1 | xenial | source + libmemcached | 1.0.18-4.2 | bionic | source + libmemcached | 1.0.18-4.2 | cosmic | source + libmemcached | 1.0.18-4.2 | disco | source * Debian bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=919696 * Upstream seems pretty quiet since 2014 Unfortunately, because the project seems more or less dead ... it seems like we won't be able submit anything upstream and go straight to fixing Debian and Ubuntu. - - Repo: + - Repo: bzr branch lp:libmemcached - Last commit: revno: 1113 [merge] committer: Continuous Integration <c...@tangent.org> branch nick: workspace timestamp: Sun 2014-02-16 03:31:37 -0800 message: Merge bzr://soup.haus/ Build: jenkins-Libmemcached-473
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1573594 Title: Missing null termination in PROTOCOL_BINARY_CMD_SASL_LIST_MECHS response handling To manage notifications about this bug go to: https://bugs.launchpad.net/libmemcached/+bug/1573594/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
