OpenSSH v5.6 Released

    Date23 Aug 2010
    Posted ByAlex
    OpenSSH 5.6 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 5.5
     * Added a ControlPersist option to ssh_config(5) that automatically
       starts a background ssh(1) multiplex master when connecting. This
       connection can stay alive indefinitely, or can be set to
       automatically close after a user-specified duration of inactivity.
     * Hostbased authentication may now use certificate host keys. CA keys
       must be specified in a known_hosts file using the @cert-authority
       marker as described in sshd(8).
     * ssh-keygen(1) now supports signing certificate using a CA key that
       has been stored in a PKCS#11 token.
     * ssh(1) will now log the hostname and address that we connected to at
       LogLevel=verbose after authentication is successful to mitigate
       "phishing" attacks by servers with trusted keys that accept
       authentication silently and automatically before presenting fake
       password/passphrase prompts.
       Note that, for such an attack to be successful, the user must have
       disabled StrictHostKeyChecking (enabled by default) or an attacker
       must have access to a trusted host key for the destination server.
     * Expand %h to the hostname in ssh_config Hostname options. While this
       sounds useless, it is actually handy for working with unqualified
         Host *.*
            Hostname %h
         Host *
     * Allow ssh-keygen(1) to import (-i) and export (-e) of PEM and PKCS#8
       keys in addition to RFC4716 (SSH.COM) encodings via a new -m option 
     * sshd(8) will now queue debug messages for bad ownership or
       permissions on the user's keyfiles encountered during authentication
       and will send them after authentication has successfully completed.
       These messages may be viewed in ssh(1) at LogLevel=debug or higher.
     * ssh(1) connection multiplexing now supports remote forwarding with
       dynamic port allocation and can report the allocated port back to
       the user:
         LPORT=`ssh -S muxsocket -R0:localhost:25 -O forward somehost`
     * sshd(8) now supports indirection in matching of principal names
       listed in certificates. By default, if a certificate has an
       embedded principals list then the username on the server must match
       one of the names in the list for it to be accepted for
       sshd(8) now has a new AuthorizedPrincipalsFile option to specify a
       file containing a list of names that may be accepted in place of the
       username when authorizing a certificate trusted via the
       sshd_config(5) TrustedCAKeys option. Similarly, authentication
       using a CA trusted in ~/.ssh/authorized_keys now accepts a
       principals="name1[,name2,...]" to specify a list of permitted names.
       If either option is absent, the current behaviour of requiring the
       username to appear in principals continues to apply. These options
       are useful for role accounts, disjoint account namespaces and
       "user@realm"-style naming policies in certificates.
     * Additional sshd_config(5) options are now valid inside Match blocks:
     * Revised the format of certificate keys. The new format, identified as
       ssh-{dss,rsa}This email address is being protected from spambots. You need JavaScript enabled to view it. includes the following changes:
         - Adding a serial number field. This may be specified by the CA at
           the time of certificate signing.
         - Moving the nonce field to the beginning of the certificate where
           it can better protect against chosen-prefix attacks on the
           signature hash (currently infeasible against the SHA1 hash used)
         - Renaming the "constraints" field to "critical options"
         - Addng a new non-critical "extensions" field. The "permit-*"
           options are now extensions, rather than critical options to
           permit non-OpenSSH implementation of this key format to degrade
           gracefully when encountering keys with options they do not
       The older format is still supported for authentication and may still
       be used when signing certificates (use "ssh-keygen -t v00 ...").
       The v00 format, introduced in OpenSSH 5.4, will be supported for at
       least one year from this release, after which it will be deprecated
       and removed.
     * The PKCS#11 code now retries a lookup for a private key if there is
       no matching key with CKA_SIGN attribute enabled; this fixes fixes
       MuscleCard support (bz#1736)
     * Unbreak strdelim() skipping past quoted strings (bz#1757). For
       example, the following directive was not parsed correctly:
           AllowUsers "blah blah" blah
     * sftp(1): fix swapped args in upload_dir_internal(), breaking
       recursive upload depth checks and causing verbose printing of
       transfers to always be turned on (bz#1797)
     * Fix a longstanding problem where if you suspend scp(1) at the
       password/passphrase prompt the terminal mode is not restored.
     * Fix a PKCS#11 crash on some smartcards by validating the length
       returned for C_GetAttributValue (bz#1773)
     * sftp(1): fix ls in working directories that contain globbing
       characters in their pathnames (bz#1655)
     * Print warning for missing home directory when ChrootDirectory=none
     * sftp(1): fix a memory leak in do_realpath() error path (bz#1771)
     * ssk-keygen(1): Standardise error messages when attempting to open
       private key files to include "progname: filename: error reason"
     * Replace verbose and overflow-prone Linebuf code with
       read_keyfile_line() (bz#1565)
     * Include the user name on "subsystem request for ..." log messages
     * ssh(1) and sshd(8): remove hardcoded limit of 100 permitopen clauses
       and port forwards per direction (bz#1327)
     * sshd(8): ignore stderr output from subsystems to avoid hangs if a
       subsystem or shell initialisation writes to stderr (bz#1750)
     * Skip the initial check for access with an empty password when
       PermitEmptyPasswords=no (bz#1638)
     * sshd(8): fix logspam when key options (from="..." especially) deny
       non-matching keys (bz#1765)
     * ssh-keygen(1): display a more helpful error message when $HOME is
       inaccessible while trying to create .ssh directory (bz#1740)
     * ssh(1): fix hang when terminating a mux slave using ~. (bz#1758)
     * ssh-keygen(1): refuse to generate keys longer than
       OPENSSL_[RD]SA_MAX_MODULUS_BITS, since we would refuse to use
       them anyway (bz#1516)
     * Suppress spurious tty warning when using -O and stdin is not a tty
     * Kill channel when pty allocation requests fail. Fixed stuck client
       if the server refuses pty allocation (bz#1698)
    Portable OpenSSH Bugfixes:
     * sshd(8): increase the maximum username length for login recording
       to 512 characters (bz#1579)
     * Initialize the values to be returned from PAM to sane values in
       case the PAM method doesn't write to them. (bz#1795) 
     * Let configure find OpenSSL libraries in a lib64 subdirectory.
     - SHA1 (openssh-5.6.tar.gz) = fa5ac394b874d6709031306b6ac5c48399697f7f
     - SHA1 (openssh-5.6p1.tar.gz) = 347dd39c91c3529f41dae63714d452fb95efea1e
    Reporting Bugs:
    - Please read
      Security bugs should be reported directly to This email address is being protected from spambots. You need JavaScript enabled to view it.
    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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