tor - security update

Several issues have been discovered in Tor, a connection-based
low-latency anonymous communication system, resulting in information
leaks.

• Relay-early cells could be used by colluding relays on the network to
  tag user circuits and so deploy traffic confirmation attacks
  [CVE-2014-5117]. The updated version emits a warning and drops the
  circuit upon receiving inbound relay-early cells, preventing this
  specific kind of attack. Please consult the following advisory for
  more details about this issue:

https://blog.torproject.org/blog/tor-security-advisory-relay-early-traffic-confirmation-attack

• A bug in the bounds-checking in the 32-bit curve25519-donna
  implementation could cause incorrect results on 32-bit
  implementations when certain malformed inputs were used along with a
  small class of private ntor keys. This flaw does not currently
  appear to allow an attacker to learn private keys or impersonate a
  Tor server, but it could provide a means to distinguish 32-bit Tor
  implementations from 64-bit Tor implementations.

The following additional security-related improvements have been
implemented:

• As a client, the new version will effectively stop using CREATE_FAST
  cells. While this adds computational load on the network, this
  approach can improve security on connections where Tor’s circuit
  handshake is stronger than the available TLS connection security
  levels.
• Prepare clients to use fewer entry guards by honoring the consensus
  parameters. The following article provides some background:

https://blog.torproject.org/blog/improving-tors-anonymity-changing-guard-parameters

For the stable distribution (wheezy), these problems have been fixed in
version 0.2.4.23-1~deb7u1.

For the testing distribution (jessie) and the unstable distribution
(sid), these problems have been fixed in version 0.2.4.23-1.

For the experimental distribution, these problems have been fixed in
version 0.2.5.6-alpha-1.

We recommend that you upgrade your tor packages.