OpenSSH 8.9

22

OpenSSH 8.9 was released on 2022-02-23. It is available from the
mirrors listed at https://www.openssh.com/.

OpenSSH is a 100% complete SSH protocol 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:
https://www.openssh.com/donations.html

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@openssh.com” to support
this.

Security Near Miss
==================

sshd(8): fix an integer overflow in the user authentication path
that, in conjunction with other logic errors, could have yielded
unauthenticated access under difficult to exploit conditions.

This situation is not exploitable because of independent checks in
the privilege separation monitor. Privilege separation has been
enabled by default in since openssh-3.2.2 (released in 2002) and
has been mandatory since openssh-7.5 (released in 2017). Moreover,
portable OpenSSH has used toolchain features available in most
modern compilers to abort on signed integer overflow since
openssh-6.5 (released in 2014).

Thanks to Malcolm Stagg for finding and reporting this bug.

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@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). The next release of OpenSSH is likely to
make this key exchange the default method.

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 of 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.

sshd(8): fix possible string truncation when constructing paths to
.rhosts/.shosts files with very long user home directory names.

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 a 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

sshd(8): fix truncation in rhosts/shosts path construction.

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.

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

– SHA1 (openssh-8.9.tar.gz)=653310ba1a63959fe2df503fe7ad556445180127
– SHA256 (openssh-8.9.tar.gz)=mJigktP+Bk0sB7uRPuWgjcCOYZ+mIMdvRlZe66irtQA=

– SHA1 (openssh-8.9p1.tar.gz)=205cdf0040a238047e2c49f43460e03d76e5d650
– SHA256 (openssh-8.9p1.tar.gz)=/Ul2VLerFobaxnL7g9+0ukCW6LX/zazNJiOArli+xec=

Please note that the SHA256 signatures are base64 encoded and not
hexadecimal (which is the default for most checksum tools). The PGP
key used to sign the releases is available from the mirror sites:
https://cdn.openbsd.org/pub/OpenBSD/OpenSSH/RELEASE_KEY.asc

Please note that the OpenPGP key used to sign releases has been
rotated for this release. The new key has been signed by the previous
key to provide continuity.

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

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

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Ava Chan
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Ava Chan

I'm a researcher at Utokyo :) and a big fan of Ava Max