Call for testing: OpenSSH 8.9

Damien Miller
Thu, 10 Feb 2022 04:18:23 -0000

Hi,

OpenSSH 8.9p1 is almost ready for release, so we would appreciate testing
on as many platforms and systems as possible. This is a bugfix release.

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.

Future deprecation notice
========================
A near-future release of OpenSSH will switch scp(1) from using the
legacy scp/rcp protocol to using SFTP by default.

Legacy scp/rcp performs wildcard expansion of remote filenames (e.g.
"scp host:* .") through the remote shell. This has the side effect of
requiring double quoting of shell meta-characters in file names
included on scp(1) command-lines, otherwise they could be interpreted
as shell commands on the remote side.

This creates one area of potential incompatibility: scp(1) when using
the SFTP protocol no longer requires this finicky and brittle quoting,
and attempts to use it may cause transfers to fail. We consider the
removal of the need for double-quoting shell characters in file names
to be a benefit and do not intend to introduce bug-compatibility for
legacy scp/rcp in scp(1) when using the SFTP protocol.

Another area of potential incompatibility relates to the use of remote
paths relative to other user's home directories, for example -
"scp host:~user/file /tmp". The SFTP protocol has no native way to
expand a ~user path. However, sftp-server(8) in OpenSSH 8.7 and later
support a protocol extension "expand-path at openssh.com" to support
this.

Potentially-incompatible changes
===============================
 * sshd(8), portable OpenSSH only: this release removes in-built
   support for MD5-hashed passwords. If you require these on your
   system then we recommend linking against libxcrypt or similar.

 * This release modifies the FIDO security key middleware interface
   and increments SSH_SK_VERSION_MAJOR.

Changes since OpenSSH 8.8
========================
This release includes a number of new features.

New features
------------

 * ssh(1), sshd(8), ssh-add(1), ssh-agent(1): add a system for
   restricting forwarding and use of keys added to ssh-agent(1)
   A detailed description of the feature is available at
   https://www.openssh.com/agent-restrict.html and the protocol
   extensions are documented in the PROTOCOL and PROTOCOL.agent
   files in the source release.

 * ssh(1), sshd(8): add the sntrup761x25519-sha512 at openssh.com hybrid
   ECDH/x25519 + Streamlined NTRU Prime post-quantum KEX to the
   default KEXAlgorithms list (after the ECDH methods but before the
   prime-group DH ones).

 * ssh-keygen(1): when downloading resident keys from a FIDO token,
   pass back the user ID that was used when the key was created and
   append it to the filename the key is written to (if it is not the
   default). Avoids keys being clobbered if the user created multiple
   resident keys with the same application string but different user
   IDs.

 * ssh-keygen(1), ssh(1), ssh-agent(1): better handling for FIDO keys
   on tokens that provide user verification (UV) on the device itself,
   including biometric keys, avoiding unnecessary PIN prompts.

 * ssh-keygen(1): add "ssh-keygen -Y match-principals" operation to
   perform matching of principals names against an allowed signers
   file. To be used towards a TOFU model for SSH signatures in git.

 * ssh-add(1), ssh-agent(1): allow pin-required FIDO keys to be added
   to ssh-agent(1). $SSH_ASKPASS will be used to request the PIN at
   authentication time.

 * ssh-keygen(1): allow selection of hash at sshsig signing time
   (either sha512 (default) or sha256).

 * ssh(1), sshd(8): read network data directly to the packet input
   buffer instead indirectly via a small stack buffer. Provides a
   modest performance improvement.

 * ssh(1), sshd(8): read data directly to the channel input buffer,
   providing a similar modest performance improvement.

 * ssh(1): extend the PubkeyAuthentication configuration directive to
   accept yes|no|unbound|host-bound to allow control over one of the
   protocol extensions used to implement agent-restricted keys.

Bugfixes
--------

 * sshd(8): document that CASignatureAlgorithms, ExposeAuthInfo and
   PubkeyAuthOptions can be used in a Match block. PR#277.

 * ssh-keysign(1): unbreak for KEX algorithms that use SHA384/512
   exchange hashes

 * ssh(1): don't put the TTY into raw mode when SessionType=none,
   avoids ^C being unable to kill such a session. bz3360

 * scp(1): fix some corner-case bugs in SFTP-mode handling of
   ~-prefixed paths.

 * ssh(1): unbreak hostbased auth using RSA keys. Allow ssh(1) to
   select RSA keys when only RSA/SHA2 signature algorithms are
   configured (this is the default case). Previously RSA keys were
   not being considered in the default case.

 * ssh-keysign(1): make ssh-keysign use the requested signature
   algorithm and not the default for the key type. Part of unbreaking
   hostbased auth for RSA/SHA2 keys.

 * ssh(1): stricter UpdateHostkey signature verification logic on
   the client- side. Require RSA/SHA2 signatures for RSA hostkeys
   except when RSA/SHA1 was explicitly negotiated during initial
   KEX; bz3375

 * ssh(1), sshd(8): fix signature algorithm selection logic for
   UpdateHostkeys on the server side. The previous code tried to
   prefer RSA/SHA2 for hostkey proofs of RSA keys, but missed some
   cases. This will use RSA/SHA2 signatures for RSA keys if the
   client proposed these algorithms in initial KEX. bz3375

 * All: convert all uses of select(2)/pselect(2) to poll(2)/ppoll(2).
   This includes the mainloops in ssh(1), ssh-agent(1), ssh-agent(1)
   and sftp-server(8), as well as the sshd(8) listen loop and all
   other FD read/writability checks. On platforms with missing or
   broken poll(2)/ppoll(2) syscalls as select(2)-based compat shim is
   available.

 * ssh-keygen(1): the "-Y find-principals" command was verifying key
   validity when using ca certs but not with simple key lifetimes
   within the allowed signers file.

 * ssh-keygen(1): make sshsig verify-time argument parsing optional

 * ssh(1), ssh-agent(1): avoid xmalloc(0) for PKCS#11 keyid for ECDSA
   keys (we already did this for RSA keys). Avoids fatal errors for
   PKCS#11 libraries that return empty keyid, e.g. Microchip ATECC608B
   "cryptoauthlib"; bz#3364

 * ssh(1), ssh-agent(1): improve the testing of credentials against
    inserted FIDO: ask the token whether a particular key belongs to
    it in cases where the token supports on-token user-verification
    (e.g. biometrics) rather than just assuming that it will accept it.

    Will reduce spurious "Confirm user presence" notifications for key
    handles that relate to FIDO keys that are not currently inserted in at
    least some cases. bz3366

 * ssh(1), sshd(8): correct value for IPTOS_DSCP_LE. It needs to
   allow for the preceding two ECN bits. bz#3373

 * ssh-keygen(1): add missing -O option to usage() for the "-Y sign"
   option.

 * ssh-keygen(1): fix a NULL deref when using the find-principals
   function, when matching an allowed_signers line that contains a
   namespace restriction, but no restriction specified on the
   command-line

 * ssh-agent(1): fix memleak in process_extension(); oss-fuzz
   issue #42719

 * ssh(1): suppress "Connection to xxx closed" messages when LogLevel
   is set to "error" or above. bz3378

 * ssh(1), sshd(8): use correct zlib flags when inflate(3)-ing
   compressed packet data. bz3372

 * scp(1): when recursively transferring files in SFTP mode, create the
   destination directory if it doesn't already exist to match scp(1) in
   legacy RCP mode behaviour.

 * scp(1): many improvements in error message consistency between scp(1)
   in SFTP mode vs legacy RCP mode.

 * sshd(8): fix potential race in SIGTERM handling PR#289

 * ssh(1), ssh(8): since DSA keys are deprecated, move them to the
   end of the default list of public keys so that they will be tried
   last. PR#295

 * ssh-keygen(1): allow 'ssh-keygen -Y find-principals' to match
   wildcard principals in allowed_signers files

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

 * ssh(1), sshd(8): don't trust closefrom(2) on Linux. glibc's
   implementation does not work in a chroot when the kernel does not
   have close_range(2). It tries to read from /proc/self/fd and when
   that fails dies with an assertion of sorts. Instead, call
   close_range(2) directly from our compat code and fall back if
   that fails.  bz#3349,

 * OS X poll(2) is broken; use compat replacement. For character-
   special devices like /dev/null, Darwin's poll(2) returns POLLNVAL
   when polled with POLLIN. Apparently this is Apple bug 3710161 -
   not public but a websearch will find other OSS projects
   rediscovering it periodically since it was first identified in
   2005.

 * Correct handling of exceptfds/POLLPRI in our select(2)-based
   poll(2)/ppoll(2) compat implementation.

 * Cygwin: correct checking of mbstowcs() return value.

 * Add a basic SECURITY.md that refers people to the openssh.com
   website.

 * Enable additional compiler warnings and toolchain hardening flags,
   including -Wbitwise-instead-of-logical, -Wmisleading-indentation,
   -fzero-call-used-regs and -ftrivial-auto-var-init.

 * HP/UX. Use compat getline(3) on HP-UX 10.x, where the libc version
   is not reliable.