Call for testing: OpenSSH 8.0

[Damien Miller]

Hi,

OpenSSH 8.0p1 is almost ready for release, so we would appreciate testing
on as many platforms and systems as possible.

Snapshot releases for portable OpenSSH are available from
http://www.mindrot.org/openssh_snap/

The OpenBSD version is available in CVS HEAD:
http://www.openbsd.org/anoncvs.html

Portable OpenSSH is also available via git using the
instructions at http://www.openssh.com/portable.html#cvs
At https://anongit.mindrot.org/openssh.git/ or via a mirror at Github:
https://github.com/openssh/openssh-portable

Running the regression tests supplied with Portable OpenSSH does not
require installation and is a simply:

$ ./configure && make tests

Live testing on suitable non-production systems is also appreciated.
Please send reports of success or failure to
openssh-unix-dev at mindrot.org. Security bugs should be reported
directly to openssh at openssh.com.

Below is a summary of changes. More detail may be found in the ChangeLog
in the portable OpenSSH tarballs.

Thanks to the many people who contributed to this release.

Security
========

This release contains mitigation for a weakness in the scp(1) tool
and protocol (CVE-2019-6111): when copying files from a remote system
to a local directory, scp(1) did not verify that the filenames that
the server sent matched those requested by the client. This could
allow a hostile server to create or clobber unexpected local files
with attacker-controlled content.

This release adds client-side checking that the filenames sent from
the server match the command-line request,

The scp protocol is outdated, inflexible and not readily fixed. We
recommend the use of more modern protocols like sftp and rsync for
file transfer instead.

Potentially-incompatible changes
================================

This release includes a number of changes that may affect existing
configurations:

 * scp(1): Relating to the above changes to scp(1); the scp protocol
   relies on the remote shell for wildcard expansion, so there is no
   infallible way for the client's wildcard matching to perfectly
   reflect the server's. If there is a difference between client and
   server wildcard expansion, the client may refuse files from the
   server. For this reason, we have provided a new "-T" flag to scp
   that disables these client-side checks at the risk of
   reintroducing the attack described above.

 * 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 establised 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; bz#2335

Changes since OpenSSH 7.9
=========================

This release is focused on new features and internal refactoring.

New Features
------------

 * ssh(1), ssh-agent(1), ssh-add(1): Add support for ECDSA keys in
   PKCS#11 tokens.

 * ssh(1), sshd(8): Add experimental quantum-computing resistant
   key exchange method, based on a combination of Streamlined NTRU
   Prime 4591^761 and X25519.

 * ssh-keygen(1): Increase the default RSA key size to 3072 bits,
   following NIST Special Publication 800-57's guidance for a
   128-bit equivalent symmetric security level.

 * ssh(1): Allow "PKCS11Provide=none" to override later instances of
   the PKCS11Provide directive in ssh_config; bz#2974

 * sshd(8): Add a log message for situations where a connection is
   dropped for attempting to run a command but a sshd_config
   ForceCommand=internal-sftp restriction is in effect; bz#2960

 * ssh(1): When prompting whether to record a new host key, accept
   the key fingerprint as a synonym for "yes". This allows the user
   to paste a fingerprint obtained out of band at the prompt and
   have the client do the comparison for you.

 * ssh-keygen(1): When signing multiple certificates on a single
   command-line invocation, allow automatically incrementing the
   certificate serial number.

 * scp(1), sftp(1): Accept -J option as an alias to ProxyJump on
   the scp and sftp command-lines.

 * ssh-agent(1), ssh-pkcs11-helper(8), ssh-add(1): Accept "-v"
   command-line flags to increase the verbosity of output; pass
   verbose flags though to subprocesses, such as ssh-pkcs11-helper
   started from ssh-agent.

 * ssh-add(1): Add a "-T" option to allowing testing whether keys in
   an agent are usable by performing a signature and a verification.

 * sftp-server(8): Add a "lsetstat at openssh.com" protocol extension
   that replicates the functionality of the existing SSH2_FXP_SETSTAT
   operation but does not follow symlinks. bz#2067

 * sftp(1): Add "-h" flag to chown/chgrp/chmod commands to request
   they do not follow symlinks.

 * sshd(8): Expose $SSH_CONNECTION in the PAM environment. This makes
   the connection 4-tuple available to PAM modules that wish to use
   it in decision-making. bz#2741

 * sshd(8): Add a ssh_config "Match final" predicate Matches in same
   pass as "Match canonical" but doesn't require hostname
   canonicalisation be enabled. bz#2906

 * sftp(1): Support a prefix of '@' to suppress echo of sftp batch
   commands; bz#2926

 * ssh-keygen(1): When printing certificate contents using
   "ssh-keygen -Lf /path/certificate", include the algorithm that
   the CA used to sign the cert.

Bugfixes
--------

 * sshd(8): Fix authentication failures when sshd_config contains
   "AuthenticationMethods any" inside a Match block that overrides
   a more restrictive default.

 * sshd(8): Avoid sending duplicate keepalives when ClientAliveCount
   is enabled.

 * sshd(8): Fix two race conditions related to SIGHUP daemon restart.
   Remnant file descriptors in recently-forked child processes could
   block the parent sshd's attempt to listen(2) to the configured
   addresses. Also, the restarting parent sshd could exit before any
   child processes that were awaiting their re-execution state had
   completed reading it, leaving them in a fallback path.

 * ssh(1): Fix stdout potentially being redirected to /dev/null when
   ProxyCommand=- was in use.

 * sshd(8): Avoid sending SIGPIPE to child processes if they attempt
   to write to stderr after their parent processes have exited;
   bz#2071

 * ssh(1): Fix bad interaction between the ssh_config ConnectTimeout
   and ConnectionAttempts directives - connection attempts after the
   first were ignoring the requested timeout; bz#2918

 * ssh-keyscan(1): Return a non-zero exit status if no keys were
   found; bz#2903

 * scp(1): Sanitize scp filenames to allow UTF-8 characters without
   terminal control sequences;  bz#2434

 * sshd(8): Fix confusion between ClientAliveInterval and time-based
   RekeyLimit that could cause connections to be incorrectly closed.
   bz#2757

 * ssh(1), ssh-add(1): Correct some bugs in PKCS#11 token PIN
   handling at initial token login. The attempt to read the PIN
   could be skipped in some cases, particularly on devices with
   integrated PIN readers. This would lead to an inability to
   retrieve keys from these tokens. bz#2652

 * ssh(1), ssh-add(1): Support keys on PKCS#11 tokens that set the
   CKA_ALWAYS_AUTHENTICATE flag by requring a fresh login after the
   C_SignInit operation. bz#2638

 * ssh(1): Improve documentation for ProxyJump/-J, clarifying that
   local configuration does not apply to jump hosts.

 * ssh-keygen(1): Clarify manual - ssh-keygen -e only writes
   public keys, not private.

 * ssh(1), sshd(8): be more strict in processing protocol banners,
   allowing \r characters only immediately before \n.

 * Various: fix a number of memory leaks, including bz#2942 and
   bz#2938

 * scp(1), sftp(1): fix calculation of initial bandwidth limits.
   Account for bytes written before the timer starts and adjust the
   schedule on which recalculations are performed. Avoids an initial
   burst of traffic and yields more accurate bandwidth limits;
   bz#2927

 * sshd(8): Only consider the ext-info-c extension during the initial
   key eschange. It shouldn't be sent in subsequent ones, but if it
   is present we should ignore it. This prevents sshd from sending a
   SSH_MSG_EXT_INFO for REKEX for buggy these clients. bz#2929

 * ssh-keygen(1): Clarify manual that ssh-keygen -F (find host in 
   authorized_keys) and -R (remove host from authorized_keys) options
   may accept either a bare hostname or a [hostname]:port combo.
   bz#2935

 * ssh(1): Don't attempt to connect to empty SSH_AUTH_SOCK; bz#2936

 * sshd(8): Silence error messages when sshd fails to load some of
   the default host keys. Failure to load an explicitly-configured
   hostkey is still an error, and failure to load any host key is
   still fatal. pr/103

 * ssh(1): Redirect stderr of ProxyCommands to /dev/null when ssh is
   started with ControlPersist; prevents random ProxyCommand output
   from interfering with session output.

 * ssh(1): The ssh client was keeping a redundant ssh-agent socket
   (leftover from authentication) around for the life of the
   connection; bz#2912

 * sshd(8): Fix bug in HostbasedAcceptedKeyTypes and
   PubkeyAcceptedKeyTypes options. If only RSA-SHA2 siganture types
   were specified, then authentication would always fail for RSA keys
   as the monitor checks only the base key (not the signature
   algorithm) type against *AcceptedKeyTypes. bz#2746

 * ssh(1): Request correct signature types from ssh-agent when
   certificate keys and RSA-SHA2 signatures are in use.

Portability
-----------

 * sshd(8): On Cygwin, run as SYSTEM where possible, using S4U for
   token creation if it supports MsV1_0 S4U Logon.

 * sshd(8): On Cygwin, use custom user/group matching code that
   respects the OS' behaviour of case-insensitive matching.

 * sshd(8): Don't set $MAIL if UsePAM=yes as PAM typically specifies
   the user environment if it's enabled; bz#2937

 * sshd(8) Cygwin: Change service name to cygsshd to avoid collision
   with Microsoft's OpenSSH port.

 * Allow building against OpenSSL -dev (3.x)

 * Fix a number of build problems against version configurations and
   versions of OpenSSL. Including bz#2931 and bz#2921

 * Improve warnings in cygwin service setup. bz#2922

 * Remove hardcoded service name in cygwin setup. bz#2922

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.