OpenSSH 5.4Edit

From the official release announcement:

OpenSSH 5.4 has just been released. It will be available from the
mirrors listed at shortly.

OpenSSH is a 100% complete SSH protocol version 1.3, 1.5 and 2.0
implementation and includes sftp client and server support.

Once again, we would like to thank the OpenSSH community for their
continued support of the project, especially those who contributed code
or patches, reported bugs, tested snapshots or donated to the project.
More information on donations may be found at:

This is a major feature and bugfix 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.

* Remove the libsectok/OpenSC-based smartcard code and add support for
  PKCS#11 tokens. This 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) manpages.

* 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
  or via a TrustedUserCAKeys option in sshd_config(5) (for user
  authentication), or in 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 extensions 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

* Add the ability to revoke keys in sshd(8) and ssh(1). User keys may
  be revoked using a new sshd_config(5) option "RevokedKeys". Host keys
  are revoked through known_hosts (details in the sshd(8) man page).
  Revoked keys cannot be used for user or host authentication and will
  trigger a warning if used.

* 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 newly-generated keys
  as well as keys that are reencrypted (e.g. by changing their


* Hold authentication debug messages until after successful
  authentication. Fixes a minor information leak of environment
  variables specified in authorized_keys if an attacker happens to
  know the public key in use.
* 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 constraints (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#1470
* 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
* Unbreak builds on Redhat using the supplied openssh.spec; bz#1731
* Fix incorrect privilege dropping order on AIX that prevented
  chroot operation; bz#1567
* Call aix_setauthdb/aix_restoredb at the correct times on AIX to
  prevent authentication failure; bz#1710


- SHA1 (openssh-5.4.tar.gz) = 1776832d902f7b4c7863afd41a5ec7a14efe95d6
- SHA1 (openssh-5.4p1.tar.gz) = 2a3042372f08afb1415ceaec8178213276a36302

Reporting Bugs:

- Please read
 Security bugs should be reported directly to

OpenSSH is brought to you by Markus Friedl, Niels Provos, Theo de Raadt,
Kevin Steves, Damien Miller, Darren Tucker, Jason McIntyre, Tim Rice and
Ben Lindstrom.