RHBA-2013:0329 - Bug Fix Advisory

Topic

Updated libssh2 packages that fix several bugs and add various enhancements are
now available for Red Hat Enterprise Linux 6.

Description

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

The libssh2 packages have been upgraded to upstream version 1.4.2, which
provides a number of bug fixes and enhancements over the previous version,
including fixes for memory leaks, missing error handling, and incompatibilities
in the SSH2 protocol implementation. (BZ#749873)

This update fixes the following bugs:

• With this update, several stability patches have been added to libssh2. As a

result, memory leaks, buffer overruns, and null pointer problems are avoided
when managing a large number of nodes. (BZ#741919)

• Previously, an insufficient data type was used for certain bit shift

operations in the libssh2 code. This behavior caused the curl utility to
terminate unexpectedly when downloading files larger than 2 GB over the SSH File
Transfer Protocol (SFTP). With this update, the underlying code has been
modified to use the correct data type and curl now works as expected in the
described scenario. (BZ#801428)

• Under certain circumstances, libssh2 failed to resume an interrupted key

exchange when sending a large amount of data over SSH. Moreover, further data
was erroneously sent, which caused the remote site to close the connection
immediately. With this update, libssh2 has been modified to properly resume the
interrupted key exchange before sending any further data. As a result, the
connection remains open and the data transfer proceeds as expected. (BZ#804145)

• Previously, the function for writing to a channel in libssh2 incorrectly

handled error states, which, under certain circumstances, resulted in an
infinite loop. The function has been fixed and the error handling now works
properly. (BZ#804150)

• Previously, the window size adjustment in libssh2 did not work properly, which

resulted in unclosed connections when transferring huge files over SCP or SFTP,
extensive memory consumption or both. The window-adjusting code has been fixed
and works now properly for blocks of arbitrary size. (BZ#806862, BZ#873785)

• Previously, libssh2 incorrectly returned the LIBSSH2_ERROR_EAGAIN error code

when operating in blocking mode. The error code is used by libssh2 internally to
initiate a blocking operation on a socket. The error code was, however, not
properly cleared on success and leaked through the public API of libssh2. An
upstream patch has been applied to clear the error code prior to initiating the
blocking operation, and libssh2 no longer returns LIBSSH2_ERROR_EAGAIN when
operating in blocking mode. (BZ#826511)

All users of libssh2 are advised to upgrade to these updated packages, which fix
these bugs and add these enhancements. After installing these updated packages,
all running applications using libssh2 have to be restarted for this update to
take effect.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension (for IBM z Systems) 6 s390x

Fixes

• BZ - 745420 - libssh2 sftp_RW_nonblock upstream example test fail
• BZ - 804145 - libssh2 fails key re-exchange when write channel is saturated
• BZ - 804150 - Unchecked error in _libssh2_channel_write results in infinite loop
• BZ - 806862 - connection not closed when really large file is transferred with curl scp protocol
• BZ - 826511 - libssh2 returns LIBSSH2_ERROR_EAGAIN in blocking mode
• BZ - 873785 - curl consumes too much memory during scp download

CVEs

(none)

References

(none)