Tor is released (security patches)

by erinn | January 17, 2011

Tor continues our recent code security audit work. The main
fix resolves a remote heap overflow vulnerability that can allow remote
code execution. Other fixes address a variety of assert and crash bugs,
most of which we think are hard to exploit remotely.

All Tor users should upgrade.

Changes in version - 2011-01-15
Major bugfixes (security):

  • Fix a heap overflow bug where an adversary could cause heap
    corruption. This bug probably allows remote code execution
    attacks. Reported by "debuger". Fixes CVE-2011-0427. Bugfix on
  • Prevent a denial-of-service attack by disallowing any
    zlib-compressed data whose compression factor is implausibly
    high. Fixes part of bug 2324; reported by "doorss".
  • Zero out a few more keys in memory before freeing them. Fixes
    bug 2384 and part of bug 2385. These key instances found by
    "cypherpunks", based on Andrew Case's report about being able
    to find sensitive data in Tor's memory space if you have enough
    permissions. Bugfix on 0.0.2pre9.

Major bugfixes (crashes):

  • Prevent calls to Libevent from inside Libevent log handlers.
    This had potential to cause a nasty set of crashes, especially
    if running Libevent with debug logging enabled, and running
    Tor with a controller watching for low-severity log messages.
    Bugfix on Fixes bug 2190.
  • Add a check for SIZE_T_MAX to tor_realloc() to try to avoid
    underflow errors there too. Fixes the other part of bug 2324.
  • Fix a bug where we would assert if we ever had a file (or another file read directly into
    memory) of exactly SIZE_T_CEILING bytes. Fixes bug 2326; bugfix
    on Found by doorss.
  • Fix some potential asserts and parsing issues with grossly
    malformed router caches. Fixes bug 2352; bugfix on Tor
    Found by doorss.

Minor bugfixes (other):

  • Fix a bug with handling misformed replies to reverse DNS lookup
    requests in DNSPort. Bugfix on Tor Related to a
    bug reported by doorss.
  • Fix compilation on mingw when a pthreads compatibility library
    has been installed. (We don't want to use it, so we shouldn't
    be including pthread.h.) Fixes bug 2313; bugfix on
  • Fix a bug where we would declare that we had run out of virtual
    addresses when the address space was only half-exhausted. Bugfix
  • Correctly handle the case where AutomapHostsOnResolve is set but
    no virtual addresses are available. Fixes bug 2328; bugfix on Bug found by doorss.
  • Correctly handle wrapping around when we run out of virtual
    address space. Found by cypherpunks, bugfix on

Minor features:

  • Update to the January 1 2011 Maxmind GeoLite Country database.
  • Introduce output size checks on all of our decryption functions.

Build changes:

  • Tor does not build packages correctly with Automake 1.6 and earlier;
    added a check to to make sure that we're building with
    Automake 1.7 or later.
  • The tarball was missing src/common/OpenBSD_malloc_Linux.c
    because we built it with a too-old version of automake. Thus that
    release broke ./configure --enable-openbsd-malloc, which is popular
    among really fast exit relays on Linux.


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