openssh/debian/NEWS

openssh (1:8.2p1-1) unstable; urgency=medium

  OpenSSH 8.2 includes a number of changes that may affect existing
  configurations:

   * ssh(1), sshd(8), ssh-keygen(1): This release removes the "ssh-rsa"
     (RSA/SHA1) algorithm from those accepted for certificate signatures
     (i.e.  the client and server CASignatureAlgorithms option) and will use
     the rsa-sha2-512 signature algorithm by default when the ssh-keygen(1)
     CA signs new certificates.

     Certificates are at special risk to SHA1 collision vulnerabilities as
     an attacker has effectively unlimited time in which to craft a
     collision that yields them a valid certificate, far more than the
     relatively brief LoginGraceTime window that they have to forge a host
     key signature.

     The OpenSSH certificate format includes a CA-specified (typically
     random) nonce value near the start of the certificate that should make
     exploitation of chosen-prefix collisions in this context challenging,
     as the attacker does not have full control over the prefix that
     actually gets signed. Nonetheless, SHA1 is now a demonstrably broken
     algorithm and further improvements in attacks are highly likely.

     OpenSSH releases prior to 7.2 do not support the newer RSA/SHA2
     algorithms and will refuse to accept certificates signed by an OpenSSH
     8.2+ CA using RSA keys unless the unsafe algorithm is explicitly
     selected during signing ("ssh-keygen -t ssh-rsa").  Older
     clients/servers may use another CA key type such as ssh-ed25519
     (supported since OpenSSH 6.5) or one of the ecdsa-sha2-nistp256/384/521
     types (supported since OpenSSH 5.7) instead if they cannot be upgraded.

   * ssh(1), sshd(8): Remove diffie-hellman-group14-sha1 from the default
     key exchange proposal for both the client and server.

   * ssh-keygen(1): The command-line options related to the generation and
     screening of safe prime numbers used by the
     diffie-hellman-group-exchange-* key exchange algorithms have changed.
     Most options have been folded under the -O flag.

   * sshd(8): The sshd listener process title visible to ps(1) has changed
     to include information about the number of connections that are
     currently attempting authentication and the limits configured by
     MaxStartups.

 -- Colin Watson <cjwatson@debian.org>  Fri, 21 Feb 2020 16:36:37 +0000

openssh (1:8.1p1-1) unstable; urgency=medium

  OpenSSH 8.1 includes a number of changes that may affect existing
  configurations:

   * ssh-keygen(1): when acting as a CA and signing certificates with an RSA
     key, default to using the rsa-sha2-512 signature algorithm.
     Certificates signed by RSA keys will therefore be incompatible with
     OpenSSH versions prior to 7.2 unless the default is overridden (using
     "ssh-keygen -t ssh-rsa -s ...").

 -- Colin Watson <cjwatson@debian.org>  Thu, 10 Oct 2019 10:23:19 +0100

openssh (1:8.0p1-1) experimental; urgency=medium

  OpenSSH 8.0 includes a number of changes that may affect existing
  configurations:

   * sshd(8): Remove support for obsolete "host/port" syntax.
     Slash-separated host/port was added in 2001 as an alternative to
     host:port syntax for the benefit of IPv6 users.  These days there are
     established standards for this like [::1]:22 and the slash syntax is
     easily mistaken for CIDR notation, which OpenSSH supports for some
     things.  Remove the slash notation from ListenAddress and PermitOpen.

 -- Colin Watson <cjwatson@debian.org>  Sun, 09 Jun 2019 22:47:27 +0100

openssh (1:7.9p1-1) unstable; urgency=medium

  OpenSSH 7.9 includes a number of changes that may affect existing
  configurations:

   * ssh(1), sshd(8): the setting of the new CASignatureAlgorithms option
     bans the use of DSA keys as certificate authorities.
   * sshd(8): the authentication success/failure log message has changed
     format slightly.  It now includes the certificate fingerprint
     (previously it included only key ID and CA key fingerprint).

 -- Colin Watson <cjwatson@debian.org>  Sun, 21 Oct 2018 10:39:24 +0100

openssh (1:7.8p1-1) unstable; urgency=medium

  OpenSSH 7.8 includes a number of changes that may affect existing
  configurations:

   * ssh-keygen(1): Write OpenSSH format private keys by default instead of
     using OpenSSL's PEM format.  The OpenSSH format, supported in OpenSSH
     releases since 2014 and described in the PROTOCOL.key file in the
     source distribution, offers substantially better protection against
     offline password guessing and supports key comments in private keys.
     If necessary, it is possible to write old PEM-style keys by adding "-m
     PEM" to ssh-keygen's arguments when generating or updating a key.
   * sshd(8): Remove internal support for S/Key multiple factor
     authentication.  S/Key may still be used via PAM or BSD auth.
   * ssh(1): Remove vestigial support for running ssh(1) as setuid.  This
     used to be required for hostbased authentication and the (long gone)
     rhosts-style authentication, but has not been necessary for a long
     time.  Attempting to execute ssh as a setuid binary, or with uid !=
     effective uid will now yield a fatal error at runtime.
   * sshd(8): The semantics of PubkeyAcceptedKeyTypes and the similar
     HostbasedAcceptedKeyTypes options have changed.  These now specify
     signature algorithms that are accepted for their respective
     authentication mechanism, where previously they specified accepted key
     types.  This distinction matters when using the RSA/SHA2 signature
     algorithms "rsa-sha2-256", "rsa-sha2-512" and their certificate
     counterparts.  Configurations that override these options but omit
     these algorithm names may cause unexpected authentication failures (no
     action is required for configurations that accept the default for these
     options).
   * sshd(8): The precedence of session environment variables has changed.
     ~/.ssh/environment and environment="..." options in authorized_keys
     files can no longer override SSH_* variables set implicitly by sshd.
   * ssh(1)/sshd(8): The default IPQoS used by ssh/sshd has changed.  They
     will now use DSCP AF21 for interactive traffic and CS1 for bulk.  For a
     detailed rationale, please see the commit message:
     https://cvsweb.openbsd.org/src/usr.bin/ssh/readconf.c#rev1.284

 -- Colin Watson <cjwatson@debian.org>  Thu, 30 Aug 2018 15:35:27 +0100

openssh (1:7.6p1-1) unstable; urgency=medium

  OpenSSH 7.6 includes a number of changes that may affect existing
  configurations:

   * ssh(1): Delete SSH protocol version 1 support, associated configuration
     options and documentation.
   * ssh(1)/sshd(8): Remove support for the hmac-ripemd160 MAC.
   * ssh(1)/sshd(8): Remove support for the arcfour, blowfish and CAST
     ciphers.
   * Refuse RSA keys <1024 bits in length and improve reporting for keys
     that do not meet this requirement.
   * ssh(1): Do not offer CBC ciphers by default.

 -- Colin Watson <cjwatson@debian.org>  Fri, 06 Oct 2017 12:36:48 +0100

openssh (1:7.5p1-1) experimental; urgency=medium

  OpenSSH 7.5 includes a number of changes that may affect existing
  configurations:

   * This release deprecates the sshd_config UsePrivilegeSeparation option,
     thereby making privilege separation mandatory.

   * The format of several log messages emitted by the packet code has
     changed to include additional information about the user and their
     authentication state. Software that monitors ssh/sshd logs may need to
     account for these changes. For example:

       Connection closed by user x 1.1.1.1 port 1234 [preauth]
       Connection closed by authenticating user x 10.1.1.1 port 1234 [preauth]
       Connection closed by invalid user x 1.1.1.1 port 1234 [preauth]

     Affected messages include connection closure, timeout, remote
     disconnection, negotiation failure and some other fatal messages
     generated by the packet code.

 -- Colin Watson <cjwatson@debian.org>  Sun, 02 Apr 2017 02:58:01 +0100

openssh (1:7.4p1-7) unstable; urgency=medium

  This version restores the default for AuthorizedKeysFile to search both
  ~/.ssh/authorized_keys and ~/.ssh/authorized_keys2, as was the case in
  Debian configurations before 1:7.4p1-1.  Upstream intends to phase out
  searching ~/.ssh/authorized_keys2 by default, so you should ensure that
  you are only using ~/.ssh/authorized_keys, at least for critical
  administrative access; do not assume that the current default will remain
  in place forever.

 -- Colin Watson <cjwatson@debian.org>  Sun, 05 Mar 2017 02:12:42 +0000

openssh (1:7.4p1-1) unstable; urgency=medium

  OpenSSH 7.4 includes a number of changes that may affect existing
  configurations:

   * ssh(1): Remove 3des-cbc from the client's default proposal.  64-bit
     block ciphers are not safe in 2016 and we don't want to wait until
     attacks like SWEET32 are extended to SSH.  As 3des-cbc was the only
     mandatory cipher in the SSH RFCs, this may cause problems connecting to
     older devices using the default configuration, but it's highly likely
     that such devices already need explicit configuration for key exchange
     and hostkey algorithms already anyway.
   * sshd(8): Remove support for pre-authentication compression.  Doing
     compression early in the protocol probably seemed reasonable in the
     1990s, but today it's clearly a bad idea in terms of both cryptography
     (cf. multiple compression oracle attacks in TLS) and attack surface.
     Pre-auth compression support has been disabled by default for >10
     years.  Support remains in the client.
   * ssh-agent will refuse to load PKCS#11 modules outside a whitelist of
     trusted paths by default.  The path whitelist may be specified at
     run-time.
   * sshd(8): When a forced-command appears in both a certificate and an
     authorized keys/principals command= restriction, sshd will now refuse
     to accept the certificate unless they are identical.  The previous
     (documented) behaviour of having the certificate forced-command
     override the other could be a bit confusing and error-prone.
   * sshd(8): Remove the UseLogin configuration directive and support for
     having /bin/login manage login sessions.

  The unprivileged sshd process that deals with pre-authentication network
  traffic is now subject to additional sandboxing restrictions by default:
  that is, the default sshd_config now sets UsePrivilegeSeparation to
  "sandbox" rather than "yes".  This has been the case upstream for a while,
  but until now the Debian configuration diverged unnecessarily.

 -- Colin Watson <cjwatson@debian.org>  Tue, 27 Dec 2016 18:01:46 +0000

openssh (1:7.2p1-1) unstable; urgency=medium

  OpenSSH 7.2 disables a number of legacy cryptographic algorithms by
  default in ssh:

   * Several ciphers blowfish-cbc, cast128-cbc, all arcfour variants and the
     rijndael-cbc aliases for AES.
   * MD5-based and truncated HMAC algorithms.

  These algorithms are already disabled by default in sshd.

 -- Colin Watson <cjwatson@debian.org>  Tue, 08 Mar 2016 11:47:20 +0000

openssh (1:7.1p1-2) unstable; urgency=medium

  OpenSSH 7.0 disables several pieces of weak, legacy, and/or unsafe
  cryptography.

   * Support for the legacy SSH version 1 protocol is disabled by default at
     compile time.  Note that this also means that the Cipher keyword in
     ssh_config(5) is effectively no longer usable; use Ciphers instead for
     protocol 2.  The openssh-client-ssh1 package includes "ssh1", "scp1",
     and "ssh-keygen1" binaries which you can use if you have no alternative
     way to connect to an outdated SSH1-only server; please contact the
     server administrator or system vendor in such cases and ask them to
     upgrade.
   * Support for the 1024-bit diffie-hellman-group1-sha1 key exchange is
     disabled by default at run-time.  It may be re-enabled using the
     instructions at http://www.openssh.com/legacy.html
   * Support for ssh-dss, ssh-dss-cert-* host and user keys is disabled by
     default at run-time.  These may be re-enabled using the instructions at
     http://www.openssh.com/legacy.html
   * Support for the legacy v00 cert format has been removed.

  Future releases will retire more legacy cryptography, including:

   * Refusing all RSA keys smaller than 1024 bits (the current minimum is
     768 bits).
   * Several ciphers will be disabled by default: blowfish-cbc, cast128-cbc,
     all arcfour variants, and the rijndael-cbc aliases for AES.
   * MD5-based HMAC algorithms will be disabled by default.

 -- Colin Watson <cjwatson@debian.org>  Tue, 08 Dec 2015 15:33:08 +0000

openssh (1:6.9p1-1) unstable; urgency=medium

  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.

 -- Colin Watson <cjwatson@debian.org>  Thu, 20 Aug 2015 10:38:58 +0100

openssh (1:6.7p1-5) unstable; urgency=medium

  openssh-server 1:6.7p1-4 changed the default setting of AcceptEnv to list
  a number of specific LC_FOO variables rather than the wildcard LC_*.  I
  have since been persuaded that this was a bad idea and have reverted it,
  but it is difficult to automatically undo the change to
  /etc/ssh/sshd_config without compounding the problem (that of modifying
  configuration that some users did not want to be modified) further.  Most
  users who upgraded via version 1:6.7p1-4 should restore the previous value
  of "AcceptEnv LANG LC_*" in /etc/ssh/sshd_config.

 -- Colin Watson <cjwatson@debian.org>  Sun, 22 Mar 2015 23:09:32 +0000

openssh (1:5.4p1-2) unstable; urgency=low

  Smartcard support is now available using PKCS#11 tokens.  If you were
  previously using an unofficial build of Debian's OpenSSH package with
  OpenSC-based smartcard support added, then note that commands like
  'ssh-add -s 0' will no longer work; you need to use 'ssh-add -s
  /usr/lib/opensc-pkcs11.so' instead.

 -- Colin Watson <cjwatson@debian.org>  Sat, 10 Apr 2010 01:08:59 +0100

openssh (1:3.8.1p1-9) experimental; urgency=low

  The ssh package has been split into openssh-client and openssh-server. If
  you had previously requested that the sshd server should not be run, then
  that request will still be honoured. However, the recommended approach is
  now to remove the openssh-server package if you do not want to run sshd.
  You can remove the old /etc/ssh/sshd_not_to_be_run marker file after doing
  that.

 -- Colin Watson <cjwatson@debian.org>  Mon,  2 Aug 2004 20:48:54 +0100

openssh (1:3.5p1-1) unstable; urgency=low

  This version of OpenSSH disables the environment option for public keys by
  default, in order to avoid certain attacks (for example, LD_PRELOAD). If
  you are using this option in an authorized_keys file, beware that the keys
  in question will no longer work until the option is removed.

  To re-enable this option, set "PermitUserEnvironment yes" in
  /etc/ssh/sshd_config after the upgrade is complete, taking note of the
  warning in the sshd_config(5) manual page.

 -- Colin Watson <cjwatson@debian.org>  Sat, 26 Oct 2002 19:41:51 +0100

openssh (1:3.0.1p1-1) unstable; urgency=high

  As of version 3, OpenSSH no longer uses separate files for ssh1 and ssh2
  keys. This means the authorized_keys2 and known_hosts2 files are no longer
  needed. They will still be read in order to maintain backward
  compatibility.

 -- Matthew Vernon <matthew@debian.org>  Thu, 28 Nov 2001 17:43:01 +0000