OpenSSH 5.6 Edit

Created 8/23/2010, updated 3/12/2020
From the official release announcement:
OpenSSH 5.6 has just been released. It will be available from the
mirrors listed at http://www.openssh.com/ 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:
http://www.openssh.com/donations.html

Changes since OpenSSH 5.5
=========================

Features:

* 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
  hostnames:

    Host *.*
       Hostname %h
    Host *
       Hostname %h.example.org

* 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
  (bz#1749)

* 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
  authentication.

  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:

    AuthorizedKeysFile
    AuthorizedPrincipalsFile
    HostbasedUsesNameFromPacketOnly
    PermitTunnel

* Revised the format of certificate keys. The new format, identified as
  ssh-{dss,rsa}-cert-v01@openssh.com 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
      recognize.

  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.

BugFixes:

* 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
  (bz#1564)

* 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"
  (bz#1783)

* 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
  (bz#1746)

* 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.
  (bz#1756)

Checksums:
==========

- SHA1 (openssh-5.6.tar.gz) = fa5ac394b874d6709031306b6ac5c48399697f7f
- SHA1 (openssh-5.6p1.tar.gz) = 347dd39c91c3529f41dae63714d452fb95efea1e

Reporting Bugs:
===============

- Please read http://www.openssh.com/report.html
 Security bugs should be reported directly to openssh@openssh.com

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.
OpenSSH 5.6Edit

OpenSSH 5.6 Edit
