OpenBSD Journal

OpenSSH 6.8 Released

Contributed by pitrh on from the yes, toys inside dept.

This week has been full of other exciting news, so it may have been easy to miss that the OpenSSH team has released OpenSSH 6.8. The new release is billed as

This is a major release, containing a number of new features as well as a large internal re-factoring.

This is the OpenSSH version that will be in OpenBSD 5.7, with lots of goodies as well as some potentially backward-incompatible features. The full announcement is at, or look after the fold.

OpenSSH 6.8 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:

Changes since OpenSSH 6.7

This is a major release, containing a number of new features as
well as a large internal re-factoring.

Potentially-incompatible changes

 * sshd(8): UseDNS now defaults to 'no'. Configurations that match
   against the client host name (via sshd_config or authorized_keys)
   may need to re-enable it or convert to matching against addresses.

New Features

 * Much of OpenSSH's internal code has been re-factored to be more
   library-like. These changes are mostly not user-visible, but
   have greatly improved OpenSSH's testability and internal layout.

 * Add FingerprintHash option to ssh(1) and sshd(8), and equivalent
   command-line flags to the other tools to control algorithm used
   for key fingerprints. The default changes from MD5 to SHA256 and
   format from hex to base64.

   Fingerprints now have the hash algorithm prepended. An example of
   the new format: SHA256:mVPwvezndPv/ARoIadVY98vAC0g+P/5633yTC4d/wXE
   Please note that visual host keys will also be different.

 * ssh(1), sshd(8): Experimental host key rotation support. Add a
   protocol extension for a server to inform a client of all its
   available host keys after authentication has completed. The client
   may record the keys in known_hosts, allowing it to upgrade to better
   host key algorithms and a server to gracefully rotate its keys.

   The client side of this is controlled by a UpdateHostkeys config
   option (default off).

 * ssh(1): Add a ssh_config HostbasedKeyType option to control which
   host public key types are tried during host-based authentication.

 * ssh(1), sshd(8): fix connection-killing host key mismatch errors
   when sshd offers multiple ECDSA keys of different lengths.

 * ssh(1): when host name canonicalisation is enabled, try to
   parse host names as addresses before looking them up for
   canonicalisation. fixes bz#2074 and avoiding needless DNS
   lookups in some cases.

 * ssh-keygen(1), sshd(8): Key Revocation Lists (KRLs) no longer
   require OpenSSH to be compiled with OpenSSL support.

 * ssh(1), ssh-keysign(8): Make ed25519 keys work for host based

 * sshd(8): SSH protocol v.1 workaround for the Meyer, et al,
   Bleichenbacher Side Channel Attack. Fake up a bignum key before
   RSA decryption.

 * sshd(8): Remember which public keys have been used for
   authentication and refuse to accept previously-used keys.
   This allows AuthenticationMethods=publickey,publickey to require
   that users authenticate using two _different_ public keys.

 * sshd(8): add sshd_config HostbasedAcceptedKeyTypes and
   PubkeyAcceptedKeyTypes options to allow sshd to control what
   public key types will be accepted. Currently defaults to all.

 * sshd(8): Don't count partial authentication success as a failure
   against MaxAuthTries.

 * ssh(1): Add RevokedHostKeys option for the client to allow
   text-file or KRL-based revocation of host keys.

 * ssh-keygen(1), sshd(8): Permit KRLs that revoke certificates by
   serial number or key ID without scoping to a particular CA.

 * ssh(1): Add a "Match canonical" criteria that allows ssh_config
   Match blocks to trigger only in the second config pass.

 * ssh(1): Add a -G option to ssh that causes it to parse its
   configuration and dump the result to stdout, similar to "sshd -T".

 * ssh(1): Allow Match criteria to be negated. E.g. "Match !host".

 * The regression test suite has been extended to cover more OpenSSH
   features. The unit tests have been expanded and now cover key


 * ssh-keyscan(1): ssh-keyscan has been made much more robust again
   servers that hang or violate the SSH protocol.

 * ssh(1), ssh-keygen(1): Fix regression bz#2306: Key path names were
   being lost as comment fields.

 * ssh(1): Allow ssh_config Port options set in the second config
   parse phase to be applied (they were being ignored). bz#2286

 * ssh(1): Tweak config re-parsing with host canonicalisation - make
   the second pass through the config files always run when host name
   canonicalisation is enabled (and not whenever the host name
   changes) bz#2267

 * ssh(1): Fix passing of wildcard forward bind addresses when
   connection multiplexing is in use; bz#2324;

 * ssh-keygen(1): Fix broken private key conversion from non-OpenSSH
   formats; bz#2345.

 * ssh-keygen(1): Fix KRL generation bug when multiple CAs are in

 * Various fixes to manual pages: bz#2288, bz#2316, bz#2273

Portable OpenSSH

 * Support --without-openssl at configure time

   Disables and removes dependency on OpenSSL. Many features,
   including SSH protocol 1 are not supported and the set of crypto
   options is greatly restricted. This will only work on systems
   with native arc4random or /dev/urandom.

   Considered highly experimental for now.

 * Support --without-ssh1 option at configure time

   Allows disabling support for SSH protocol 1.

 * sshd(8): Fix compilation on systems with IPv6 support in utmpx; bz#2296

 * Allow custom service name for sshd on Cygwin. Permits the use of
   multiple sshd running with different service names.


 - SHA1 (openssh-6.8.tar.gz) = 99903c6ca76e0a2c044711017f81127e12459d37
 - SHA256 (openssh-6.8.tar.gz) = N1uzVarFbrm2CzAwuDu3sRoszmqpK+5phAChP/QNyuw=

 - SHA1 (openssh-6.8p1.tar.gz) = cdbc51e46a902b30d263b05fdc71340920e91c92
 - SHA256 (openssh-6.8p1.tar.gz) = P/ZM5z7hJEgLW/dnuYMNfTwDu8tqvnFrePAZLDfOFg4=

Please note that the PGP key used to sign releases was recently rotated.
The new key has been signed by the old key to provide continuity. It is
available from the mirror sites as RELEASE_KEY.asc.

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.

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