Call for testing: OpenSSH-5.4

Damien Miller djm at
Sat Feb 27 18:25:38 EST 2010


OpenSSH 5.4 is almost ready for release, so we would appreciate testing
on as many platforms and systems as possible. This is a big release,
with a number of major new features and many bug fixes.

Snapshot releases for portable OpenSSH are available from

The OpenBSD version is available in CVS HEAD:

Portable OpenSSH is also available via anonymous CVS using the
instructions at

Running the regression tests supplied with Portable OpenSSH does not
require installation and is a simply:

$ ./configure && make tests

Live testing on suitable non-production systems is also
appreciated. Please send reports of success or failure to
openssh-unix-dev at

Below is a summary of changes. More detail may be found in the ChangeLog
in the portable OpenSSH tarballs.

Thanks to the many people who contributed to this release.


Changes since OpenSSH 5.3


 * After a transition period of about 10 years, this release disables
   SSH protocol 1 by default. Clients and servers that need to use the
   legacy protocol must explicitly enable it in ssh_config / sshd_config
   or on the command-line.

 * Deprecate the libsectok/OpenSC-based smartcard code and add
   support for PKCS#11 tokens. PKCS#11 support is automatically enabled
   on all platforms that support dlopen(3) and was inspired by patches
   written by Alon Bar-Lev. Details in the ssh(1) and ssh-add(1)

 * Add support for certificate authentication of users and hosts using a
   new, minimal OpenSSH certificate format (not X.509). Certificates
   contain a public key, identity information and some validity
   constraints and are signed with a standard SSH public key using
   ssh-keygen(1). CA keys may be marked as trusted in authorized_keys
   (for user authentication) or known_hosts (for host authentication).

   Documentation for certificate support may be found in ssh-keygen(1),
   sshd(8) and ssh(1) and a description of the protocol changes in

 * Added a 'netcat mode' to ssh(1): "ssh -W host:port ..." This connects
   stdio on the client to a single port forward on the server. This
   allows, for example, using ssh as a ProxyCommand to route connections
   via intermediate servers. bz#1618

 * Rewrite the ssh(1) multiplexing support to support non-blocking
   operation of the mux master, improve the resilience of the master to
   malformed messages sent to it by the slave and add support for
   requesting port- forwardings via the multiplex protocol. The new
   stdio-to-local forward mode ("ssh -W host:port ...") is also
   supported. The revised multiplexing protocol is documented in the
   file PROTOCOL.mux in the source distribution.

 * Add a 'read-only' mode to sftp-server(8) that disables open in write
   mode and all other fs-modifying protocol methods. bz#430

 * Allow setting an explicit umask on the sftp-server(8) commandline to
   override whatever default the user has. bz#1229

 * Many improvements to the sftp(1) client, many of which were
   implemented by Carlos Silva through the Google Summer of Code
   - Support the "-h" (human-readable units) flag for ls
   - Implement tab-completion of commands, local and remote filenames
   - Support most of scp(1)'s commandline arguments in sftp(1), as a
     first step towards making sftp(1) a drop-in replacement for scp(1).
     Note that the rarely-used "-P sftp_server_path" option has been
     moved to "-D sftp_server_path" to make way for "-P port" to match
   - Add recursive transfer support for get/put and on the commandline

 * New RSA keys will be generated with a public exponent of RSA_F4 ==
   (2**16)+1 == 65537 instead of the previous value 35.

 * Passphrase-protected SSH protocol 2 private keys are now protected
   with AES-128 instead of 3DES. This applied to freshly-generated keys
   as well as keys that are reencrypted (e.g. by changing their


 * When using ChrootDirectory, make sure we test for the existence of
   the user's shell inside the chroot and not outside (bz#1679)
 * Cache user and group name lookups in sftp-server using
   user_from_[ug]id(3) to improve performance on hosts where these
   operations are slow (e.g. NIS or LDAP). bz#1495
 * Fix problem that prevented passphrase reading from being interrupted
   in some circumstances; bz#1590
 * Ignore and log any Protocol 1 keys where the claimed size is not
   equal to the actual size.
 * Make HostBased authentication work with a ProxyCommand. bz#1569
 * Avoid run-time failures when specifying hostkeys via a relative
   path by prepending the current working directory in these cases.
 * Do not prompt for a passphrase if we fail to open a keyfile, and log
   the reason why the open failed to debug. bz#1693
 * Document that the PubkeyAuthentication directive is allowed in a
   sshd_config(5) Match block. bz#1577
 * When converting keys, truncate key comments at 72 chars as per
   RFC4716. bz#1630
 * Do not allow logins if /etc/nologin exists but is not readable by the
   user logging in.
 * Output a debug log if sshd(8) can't open an existing authorized_keys.
 * Quell tc[gs]etattr warnings when forcing a tty (ssh -tt), since we
   usually don't actually have a tty to read/set; bz#1686
 * Prevent sftp from crashing when given a "-" without a command.
   Also, allow whitespace to follow a "-". bz#1691
 * After sshd receives a SIGHUP, ignore subsequent HUPs while sshd
   re-execs itself. Prevents two HUPs in quick succession from resulting
   in sshd dying. bz#1692
 * Clarify in sshd_config(5) that StrictModes does not apply to
   ChrootDirectory. Permissions and ownership are always checked when
   chrooting. bz#1532
 * Set close-on-exec on various descriptors so they don't get leaked to
   child processes. bz#1643
 * Fix very rare race condition in x11/agent channel allocation: don't
   read after the end of the select read/write fdset and make sure a
   reused FD is not touched before the pre-handlers are called.
 * Fix incorrect exit status when multiplexing and channel ID 0 is
   recycled. bz#1570
 * Fail with an error when an attempt is made to connect to a server
   with ForceCommand=internal-sftp with a shell session (i.e. not a
   subsystem session). Avoids stuck client when attempting to ssh to
   such a service. bz#1606:
 * Warn but do not fail if stat()ing the subsystem binary fails. This
   helps with chrootdirectory+forcecommand=sftp-server and restricted
   shells. bz #1599
 * Change "Connecting to host..." message to "Connected to host."
   and delay it until after the sftp protocol connection has been
   established. Avoids confusing sequence of messages when the
   underlying ssh connection experiences problems. bz#1588
 * Use the HostKeyAlias rather than the hostname specified on the
   commandline when prompting for passwords. bz#1039
 * Correct off-by-one in percent_expand(): we would fatal() when trying
   to expand EXPAND_MAX_KEYS, allowing only EXPAND_MAX_KEYS-1 to
   actually work. Note that nothing in OpenSSH actually uses close to
   this limit at present. bz#1607
 * Fix passing of empty options from scp(1) and sftp(1) to the
   underlying ssh(1). Also add support for the stop option "--".
 * Fix an incorrect magic number and typo in PROTOCOL; bz#1688
 * Don't escape backslashes when displaying the SSH2 banner. bz#1533
 * Don't unnecessarily dup() the in and out fds for sftp-server. bz#1566
 * Force use of the correct hash function for random-art signature
   display as it was inheriting the wrong one when bubblebabble
   signatures were activated. bz#1611
 * Do not fall back to adding keys without contraints (ssh-add -c /
   -t ...) when the agent refuses the constrained add request. bz#1612
 * Fix a race condition in ssh-agent that could result in a wedged or
   spinning agent. bz#1633
 * Flush stdio before exec() to ensure that everying (motd
   in particular) has made it out before the streams go away. bz#1596
 * Set FD_CLOEXEC on in/out sockets in sshd(8). bz#1706

Portable OpenSSH Bugfixes:

 * Use system's kerberos principal name on AIX if it's available.
 * Disable OOM-killing of the listening sshd on Linux. bz#1740
 * Use pkg-config for opensc config if it's available. bz#1160
 * Unbreak Redhat spec to allow building without askpass. bz#1677
 * If PidFile is set in sshd_config, use it in SMF init file. bz#1628
 * Print error and usage() when ssh-rand-helper is passed command-
   line arguments as none are supported. bz#1568
 * Add missing setsockopt() to set IPV6_V6ONLY for local forwarding
   with GatwayPorts=yes. bz#1648
 * Make GNOME 2 askpass dialog desktop-modal. bz#1645
 * If SELinux is enabled set the security context to "sftpd_t" before
   running the internal sftp server. bz#1637
 * Correctly check libselinux for necessary SELinux functions; bz#1713

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