[SECURITY] [DLA 387-1] openssh security update

Package : openssh
Version : 5.5p1-6+squeeze8
CVE ID : CVE-2016-0777 CVE-2016-0778
Debian Bug : 810984

The Qualys Security team discovered two vulnerabilities in the roaming
code of the OpenSSH client (an implementation of the SSH protocol
suite).

SSH roaming enables a client, in case an SSH connection breaks
unexpectedly, to resume it at a later time, provided the server also
supports it.

The OpenSSH server doesn't support roaming, but the OpenSSH client
supports it (even though it's not documented) and it's enabled by
default.

CVE-2016-0777

An information leak (memory disclosure) can be exploited by a rogue
SSH server to trick a client into leaking sensitive data from the
client memory, including for example private keys.

CVE-2016-0778

A buffer overflow (leading to file descriptor leak), can also be
exploited by a rogue SSH server, but due to another bug in the code
is possibly not exploitable, and only under certain conditions (not
the default configuration), when using ProxyCommand, ForwardAgent or
ForwardX11.

This security update completely disables the roaming code in the OpenSSH
client.

It is also possible to disable roaming by adding the (undocumented)
option 'UseRoaming no' to the global /etc/ssh/ssh_config file, or to the
user configuration in ~/.ssh/config, or by passing -oUseRoaming=no on
the command line.

Users with passphrase-less privates keys, especially in non interactive
setups (automated jobs using ssh, scp, rsync+ssh etc.) are advised to
update their keys if they have connected to an SSH server they don't
trust.

More details about identifying an attack and mitigations can be found in
the Qualys Security Advisory.

Yves-Alexis Perez