[SECURITY] [DLA 602-1] gnupg security and hardening update

Package : gnupg
Version : 1.4.12-7+deb7u8
CVE ID : CVE-2016-6313
Debian Bug : 834893

CVE-2016-6313

Felix Doerre and Vladimir Klebanov from the Karlsruhe Institute of
Technology discovered a flaw in the mixing functions of GnuPG's
random number generator. An attacker who obtains 4640 bits from the RNG
can trivially predict the next 160 bits of output.

A first analysis on the impact of this bug for GnuPG shows that
existing RSA keys are not weakened. For DSA and Elgamal keys it is also
unlikely that the private key can be predicted from other public
information.

Bypassing GnuPG key checking:

Weaknesses have been found in GnuPG signature validation that
attackers could exploit thanks to especially forged public keys and
under specific hardware-software conditions. While the underlying
problem cannot be solved only by software, GnuPG has been
strengthened, avoiding to rely on keyring signature caches when
verifying keys. Potential specific attacks are not valid any more
with the patch of GnuPG

Bypassing GnuPG key checking:

Vrije Universiteit Amsterdam and Katholieke Universteit Leuven
researchers discovered an attack method, known as Flip Feng Shui,
that concerns flaws in GnuPG. Researchers found that under specific
hardware-software conditions, attackers could bypass the GnuPG
signature validation by using forged public keys. While the
underlying problem cannot be solved only by software, GnuPG has been
made more robust to avoid relying on keyring signature caches when
verifying keys.

For Debian 7 "Wheezy", these issues have been addressed in version
1.4.12-7+deb7u8.

We recommend that you upgrade your gnupg packages.

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS