[tor-announce] Tor is released (security patches)

Roger Dingledine arma at mit.edu
Fri Dec 16 18:19:10 UTC 2011

Tor fixes a critical heap-overflow security issue in Tor's
buffers code. Absolutely everybody should upgrade.

The bug relied on an incorrect calculation when making data continuous
in one of our IO buffers, if the first chunk of the buffer was
misaligned by just the wrong amount. The miscalculation would allow an
attacker to overflow a piece of heap-allocated memory. To mount this
attack, the attacker would need to either open a SOCKS connection to
Tor's SocksPort (usually restricted to localhost), or target a Tor
instance configured to make its connections through a SOCKS proxy
(which Tor does not do by default).

Good security practice requires that all heap-overflow bugs should be
presumed to be exploitable until proven otherwise, so we are treating
this as a potential code execution attack. Please upgrade immediately!
This bug does not affect bufferevents-based builds of Tor. Special
thanks to "Vektor" for reporting this issue to us!

Tor also fixes several bugs in previous versions, including
crash bugs for unusual configurations, and a long-term bug that
would prevent Tor from starting on Windows machines with draconian
AV software.

With this release, we remind everyone that 0.2.0.x has reached its
formal end-of-life. Those Tor versions have many known flaws, and
nobody should be using them. You should upgrade -- ideally to the
0.2.2.x series. If you're using a Linux or BSD and its packages are
obsolete, stop using those packages and upgrade anyway.

The Tor 0.2.1.x series is also approaching its end-of-life: it will no
longer receive support after some time in early 2012.


Note that the tarball and git tags are signed by Nick Mathewson (gpg
key 165733EA) this time around.

Changes in version - 2011-12-16
  o Major bugfixes:
    - Fix a heap overflow bug that could occur when trying to pull
      data into the first chunk of a buffer, when that chunk had
      already had some data drained from it. Fixes CVE-2011-2778;
      bugfix on Reported by "Vektor".
    - Initialize Libevent with the EVENT_BASE_FLAG_NOLOCK flag enabled, so
      that it doesn't attempt to allocate a socketpair. This could cause
      some problems on Windows systems with overzealous firewalls. Fix for
      bug 4457; workaround for Libevent versions 2.0.1-alpha through
    - If we mark an OR connection for close based on a cell we process,
      don't process any further cells on it. We already avoid further
      reads on marked-for-close connections, but now we also discard the
      cells we'd already read. Fixes bug 4299; bugfix on,
      which was the first version where we might mark a connection for
      close based on processing a cell on it.
    - Correctly sanity-check that we don't underflow on a memory
      allocation (and then assert) for hidden service introduction
      point decryption. Bug discovered by Dan Rosenberg. Fixes bug 4410;
      bugfix on
    - Fix a memory leak when we check whether a hidden service
      descriptor has any usable introduction points left. Fixes bug
      4424. Bugfix on
    - Don't crash when we're running as a relay and don't have a GeoIP
      file. Bugfix on; fixes bug 4340. This backports a fix
      we've had in the 0.2.3.x branch already.
    - When running as a client, do not print a misleading (and plain
      wrong) log message that we're collecting "directory request"
      statistics: clients don't collect statistics. Also don't create a
      useless (because empty) stats file in the stats/ directory. Fixes
      bug 4353; bugfix on

  o Minor bugfixes:
    - Detect failure to initialize Libevent. This fix provides better
      detection for future instances of bug 4457.
    - Avoid frequent calls to the fairly expensive cull_wedged_cpuworkers
      function. This was eating up hideously large amounts of time on some
      busy servers. Fixes bug 4518; bugfix on
    - Resolve an integer overflow bug in smartlist_ensure_capacity().
      Fixes bug 4230; bugfix on Tor Based on a patch by
      Mansour Moufid.
    - Don't warn about unused log_mutex in log.c when building with
      --disable-threads using a recent GCC. Fixes bug 4437; bugfix on which introduced --disable-threads.
    - When configuring, starting, or stopping an NT service, stop
      immediately after the service configuration attempt has succeeded
      or failed. Fixes bug 3963; bugfix on
    - When sending a NETINFO cell, include the original address
      received for the other side, not its canonical address. Found
      by "troll_un"; fixes bug 4349; bugfix on
    - Fix a typo in a hibernation-related log message. Fixes bug 4331;
      bugfix on; found by "tmpname0901".
    - Fix a memory leak in launch_direct_bridge_descriptor_fetch() that
      occurred when a client tried to fetch a descriptor for a bridge
      in ExcludeNodes. Fixes bug 4383; bugfix on
    - Backport fixes for a pair of compilation warnings on Windows.
      Fixes bug 4521; bugfix on and on
    - If we had ever tried to call tor_addr_to_str on an address of
      unknown type, we would have done a strdup on an uninitialized
      buffer. Now we won't. Fixes bug 4529; bugfix on
      Reported by "troll_un".
    - Correctly detect and handle transient lookup failures from
      tor_addr_lookup. Fixes bug 4530; bugfix on
      Reported by "troll_un".
    - Fix null-pointer access that could occur if TLS allocation failed.
      Fixes bug 4531; bugfix on Found by "troll_un".
    - Use tor_socket_t type for listener argument to accept(). Fixes bug
      4535; bugfix on Found by "troll_un".

  o Minor features:
    - Add two new config options for directory authorities:
      AuthDirFastGuarantee sets a bandwidth threshold for guaranteeing the
      Fast flag, and AuthDirGuardBWGuarantee sets a bandwidth threshold
      that is always sufficient to satisfy the bandwidth requirement for
      the Guard flag. Now it will be easier for researchers to simulate
      Tor networks with different values. Resolves ticket 4484.
    - When Tor ignores a hidden service specified in its configuration,
      include the hidden service's directory in the warning message.
      Previously, we would only tell the user that some hidden service
      was ignored. Bugfix on 0.0.6; fixes bug 4426.
    - Update to the December 6 2011 Maxmind GeoLite Country database.

  o Packaging changes:
    - Make it easier to automate expert package builds on Windows,
      by removing an absolute path from makensis.exe command.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 190 bytes
Desc: Digital signature
URL: <http://lists.torproject.org/pipermail/tor-announce/attachments/20111216/d59cd23a/attachment.pgp>

More information about the tor-announce mailing list