libssh2 security update

CentOS Errata and Security Advisory CESA-2015:2140

The libssh2 packages provide a library that implements the SSH2 protocol.

A flaw was found in the way the kex_agree_methods() function of libssh2
performed a key exchange when negotiating a new SSH session. A
man-in-the-middle attacker could use a crafted SSH_MSG_KEXINIT packet to
crash a connecting libssh2 client. (CVE-2015-1782)

This update also fixes the following bugs:

• Previously, libssh2 did not correctly adjust the size of the receive
  window while reading from an SSH channel. This caused downloads over
  the secure copy (SCP) protocol to consume an excessive amount of memory.
  A series of upstream patches has been applied on the libssh2 source code to
  improve handling of the receive window size. Now, SCP downloads work as
  expected. (BZ#1080459)

• Prior to this update, libssh2 did not properly initialize an internal
  variable holding the SSH agent file descriptor, which caused the agent
  destructor to close the standard input file descriptor by mistake.
  An upstream patch has been applied on libssh2 sources to properly
  initialize the internal variable. Now, libssh2 closes only the file
  descriptors it owns. (BZ#1147717)

All libssh2 users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. After installing these
updated packages, all running applications using libssh2 must be restarted
for this update to take effect.

Merged security bulletin from advisories:
https://lists.centos.org/pipermail/centos-cr-announce/2015-November/028697.html

Affected packages:
libssh2
libssh2-devel
libssh2-docs

Upstream details at:
https://access.redhat.com/errata/RHSA-2015:2140