[SECURITY] [DLA 1560-1] gnutls28 security update

Package : gnutls28
Version : 3.3.30-0+deb8u1
CVE ID : CVE-2018-10844 CVE-2018-10845 CVE-2018-10846

A set of vulnerabilities was discovered in GnuTLS which allowed
attackers to do plain text recovery on TLS connections with certain
cipher types.

CVE-2018-10844

It was found that the GnuTLS implementation of HMAC-SHA-256 was
vulnerable to a Lucky thirteen style attack. Remote attackers
could use this flaw to conduct distinguishing attacks and
plaintext-recovery attacks via statistical analysis of timing data
using crafted packets.

CVE-2018-10845

It was found that the GnuTLS implementation of HMAC-SHA-384 was
vulnerable to a Lucky thirteen style attack. Remote attackers
could use this flaw to conduct distinguishing attacks and plain
text recovery attacks via statistical analysis of timing data
using crafted packets.

CVE-2018-10846

A cache-based side channel in GnuTLS implementation that leads to
plain text recovery in cross-VM attack setting was found. An
attacker could use a combination of "Just in Time" Prime+probe
attack in combination with Lucky-13 attack to recover plain text
using crafted packets.

For Debian 8 "Jessie", these problems have been fixed in version
3.3.30-0+deb8u1. It was found to be more practical to update to the
latest upstream version of the 3.3.x branch since upstream's fixes
were rather invasive and required cipher list changes anyways. This
will facilitate future LTS updates as well.

This change therefore also includes the following major policy
changes, as documented in the NEWS file:

• ARCFOUR (RC4) and SSL 3.0 are no longer included in the default
  priorities list. Those have to be explicitly enabled, e.g., with
  a string like "NORMAL:+ARCFOUR-128" or "NORMAL:+VERS-SSL3.0",
  respectively.

• The ciphers utilizing HMAC-SHA384 and SHA256 have been removed
  from the default priority strings. They are not necessary for
  compatibility or other purpose and provide no advantage over
  their SHA1 counter-parts, as they all depend on the legacy TLS
  CBC block mode.

• Follow closely RFC5280 recommendations and use UTCTime for dates
  prior to 2050.

• Require strict DER encoding for certificates, OCSP requests,
  private keys, CRLs and certificate requests, in order to reduce
  issues due to the complexity of BER rules.

• Refuse to import v1 or v2 certificates that contain extensions.

API and ABI compatibility is retained, however, although new symbols
have been added. Many bugfixes are also included in the upload. See
the provided upstream changelog for more details.

We recommend that you upgrade your gnutls28 packages and do not expect
significant breakage.

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
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