OpenSSH 10.1 has just been released. It will be available from the
mirrors listed at https://www.openssh.com/ shortly.
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 warning
--------------------------
* A future release of OpenSSH will deprecate support for SHA1 SSHFP
records due to weaknesses in the SHA1 hash function. SHA1 SSHFP
DNS records will be ignored and ssh-keygen -r will generate only
SHA256 SSHFP records.
The SHA256 hash algorithm, which has no known weaknesses, has
been supported for SSHFP records since OpenSSH 6.1, released in
2012.
Potentially-incompatible changes
--------------------------------
* ssh(1): add a warning when the connection negotiates a non-post
quantum key agreement algorithm.
This warning has been added due to the risk of "store now, decrypt
later" attacks. More details at https://openssh.com/pq.html
This warning may be controlled via a new WarnWeakCrypto ssh_config
option, defaulting to on. This option is likely to control
additional weak crypto warnings in the future.
* ssh(1), sshd(8): major changes to handling of DSCP marking/IPQoS
In both client and server the default DSCP (a.k.a IPQoS) values
were revised and the way these values are used during runtime has
changed.
Interactive traffic is now assigned to the EF (Expedited
Forwarding) class by default. This provides more appropriate
packet prioritisation information for the intermediate network,
such as wireless media (cf. RFC 8325). Non-interactive traffic
will now use the operating system default DSCP marking. Both the
interactive and non-interactive DSCP values may be overridden via
the IPQoS keyword, described in ssh_config(5) and sshd_config(5).
The appropriate DSCP marking is now automatically selected and
updated as needed over the course of a connection's lifetime.
ssh(1) and sshd(8) will switch between the interactive and
non-interactive IPQoS values depending on the type of SSH
channels open at the time. For example, if an sftp session is
using the connection alongside a shell session, then the non-
interactive value will be used for the duration of the sftp. A
connection which contains only interactive sessions is marked EF.
* ssh(1), sshd(8): deprecate support for IPv4 type-of-service (ToS)
keywords in the IPQoS configuration directive.
Type of Service (ToS) was deprecated in the late nineties and
replaced with the Differentiated Services architecture, which
has significant advantages for operators because it offers more
granularity.
OpenSSH switched its default IPQoS from ToS to DSCP values in
2018 (openssh-7.7).
IPQoS configurations with 'lowdelay', 'reliability', or
'throughput' will be ignored and will instead use the system
default QoS settings. Additionally, a debug message will be logged
about the deprecation with a suggestion to use DSCP QoS instead.
* ssh-add(1): when adding certificates to an agent, set the expiry
to the certificate expiry time plus a short (5 min) grace period.
This will cause the agent to automatically remove certificates
shortly after they expire. A new ssh-add -N option disables this
behaviour.
* All: remove experimental support for XMSS keys. This was never
enabled by default. We expect to implement a new post-quantum
signature scheme in the near future.
* ssh-agent(1), sshd(8): move agent listener sockets from /tmp to
under ~/.ssh/agent for both ssh-agent(1) and forwarded sockets
in sshd(8).
This ensures processes that have restricted filesystem access
that includes /tmp do not ambiently have the ability to use keys
in an agent.
Moving the default directory has the consequence that the OS will
no longer clean up stale agent sockets, so ssh-agent now gains
this ability.
To support $HOME on NFS, the socket path includes a truncated
hash of the hostname. ssh-agent will, by default, only clean up
sockets from the same hostname.
ssh-agent(1) gains some new flags: -U suppresses the automatic
cleanup of stale sockets when it starts. -u forces a cleanup
without keeping a running agent, -uu forces a cleanup that ignores
the hostname. -T makes ssh-agent put the socket back in /tmp.
Changes since OpenSSH 10.0
=========================
This release contains a minor security fix as well as a number of
feature improvements and bugfixes.
Security
=======
* ssh(1): disallow control characters in usernames passed via the
commandline or expanded using %-sequences from the configuration
file, and disallow \0 characters in ssh:// URIs.
If an ssh(1) commandline was constructed using usernames or URIs
obtained from an untrusted source, and if a ProxyCommand that uses
the %u expansion was configured, then it may be possible for an
attacker to inject shell expressions that may be executed when the
proxy command is started.
We strongly recommend against using untrusted inputs to construct
ssh(1) commandlines.
This change also relaxes the validity checks in one small way:
usernames supplied via the configuration file as literals (i.e.
that have no % expansion characters) are not subject to these
validity checks. This allows usernames that contain arbitrary
characters to be used, but only via configuration files. This is
done on the basis that ssh's configuration is trusted.
This issue was reported by David Leadbeater.
New features
------------
* ssh(1), sshd(8): add SIGINFO handlers to log active channel and
session information.
* sshd(8): when refusing a certificate for user authentication, log
enough information to identify the certificate in addition to the
reason why it was being denied. Makes debugging certificate
authorisation problems a bit easier.
* ssh(1), ssh-agent(1): support ed25519 keys hosted on PKCS#11
tokens.
* ssh(1): add an ssh_config(5) RefuseConnection option that, when
encountered while processing an active section in a
configuration, terminates ssh(1) with an error message that
contains the argument to the option.
This may be useful for expressing reminders or warnings in config
files, for example:
Match host foo
RefuseConnection "foo is deprecated, use splork instead"
* sshd(8): make the X11 display number check relative to
X11DisplayOffset. This will allow people to use X11DisplayOffset
to configure much higher port ranges if they really want, while
not changing the default behaviour.
* unit tests: the unit test framework now includes some basic
benchmarking capabilities. Run with "make UNITTEST_BENCHMARK=yes"
on OpenBSD or "make unit-bench" on Portable OpenSSH.
Bugfixes
--------
* sshd(8): fix mistracking of MaxStartups process exits in some
situations. At worst, this could cause all MaxStartups slots to
fill and sshd to refuse new connections.
* ssh(1): fix delay on X client startup when ObscureKeystrokeTiming
is enabled. bz#3820
* sshd(8): increase the maximum size of the supported configuration
from 256KB to 4MB, which ought to be enough for anybody. Fail
early and visibly when this limit is breached. bz3808
* sftp(1): during sftp uploads, avoid a condition where a failed
write could be ignored if a subsequent write succeeded. This is
unlikely but technically possible because sftp servers are
allowed to reorder requests.
* sshd(8): avoid a race condition when the sshd-auth process exits
that could cause a spurious error message to be logged.
* sshd(8): log at level INFO when PerSourcePenalties actually
blocks access to a source address range. Previously this was
logged at level VERBOSE, which hid enforcement actions under
default config settings.
* sshd(8): GssStrictAcceptor was missing from sshd -T output; fix
* sshd(8): Make the MaxStartups and PerSourceNetBlockSize options
first-match-wins as advertised. bz3859
* ssh(1): fix an incorrect return value check in the local forward
cancellation path that would cause failed cancellations not to be
logged.
* sshd(8): make "Match !final" not trigger a second parsing pass
of ssh_config (unless hostname canonicalisation or a separate
"Match final" does). bz3843
* ssh(1): better debug diagnostics when loading keys. Will now list
key fingerprint and algorithm (not just algorithm number) as well
as making it explicit which keys didn't load.
* All: fix a number of memory leaks found by LeakSanitizer,
Coverity and manual inspection.
* sshd(8): Output the current name for PermitRootLogin's
"prohibit-password" in sshd -T instead of its deprecated alias
"without-password". bz#3788
* ssh(1): make writing known_hosts lines more atomic by writing
the entire line in one operation and using unbuffered stdio.
Usually writes to this file are serialised on the "Are you sure
you want to continue connecting?" prompt, but if host key
checking is disabled and connections were being made with high
concurrency then interleaved writes might have been possible.
Portability
-----------
* sshd(8): check the username didn't change during the PAM
transactions.
PAM modules can change the user during their execution, but
this is not supported by sshd(8). If such a case was incorrectly
configured by the system administrator, then sshd(8) could end up
using a different username to the one authorised by PAM.
* sshd(8): don't log audit messages with UNKNOWN hostname to avoid
slow DNS lookups in the audit subsystem.
* All: when making a copy of struct passwd, ensure struct fields are
non-NULL. Android libc can return NULL pw_gecos, for example.
* All: Remove status bits from OpenSSL >=3 version check.
* sshd(8), ssh(1): Use SSH_TUN_COMPAT_AF on FreeBSD. Otherwise tun
forwarding from other OSes fails as soon as the first IPv6 message
is sent by the other side (which is usually a Router Solicitation
ICMPv6 message which is sent as soon as the interface is up).
* ssh(1), ssh-agent(8): check for nlist function presence before
attempting to use it instead of relying on the presence of the
nlist.h header. Mac OS X, for example, has the header but not
the function in the 64bit libraries.
* All: fill in missing system header files.
Create replacement header files inside openbsd-compat for common
headers that are missing on a given platform. Usually these are
just empty, but in some cases they'll include the equivalent file.
This avoids having to wrap those includes in '#ifdef HAVE_FOO_H'
and reduces the diff between Portable OpenSSH and OpenBSD.
* sshd(8): handle futex_time64 properly in seccomp sandbox
Previously we only allowed __NR_futex, but some 32-bit systems
apparently support __NR_futex_time64. We had support for this
in the sandbox, but because of a macro error only __NR_futex was
allowlisted.
* Add contrib/gnome-ssh-askpass4 for GNOME 40+ using the GCR API.
* sshd(8): let ga_init() fail gracefully if getgrouplist does.
Apparently getgrouplist() can fail on OSX when passed a
non-existent group name. Other platforms seem to return a group
list consisting of the numeric gid passed to the function. bz3848
* ssh-agent(1): exit 0 from SIGTERM under systemd socket-activation,
preventing a graceful shutdown of an agent via systemd from
incorrectly marking the service as "failed".
* build: wrap some autoconf macros in AC_CACHE_CHECK.
This allows skipping/overriding the OSSH_CHECK_CFLAG_COMPILE and
OSSH_CHECK_CFLAG_LINK macros used to discover supported compiler
or linker flags. E.g.
$ ./configure ossh_cv_cflag__fzero_call_used_regs_used=no
[...]
checking if cc supports compile flag -fzero-call-used-regs=used
and linking succeeds... (cached) no
Checksums:
=========
SHA1 (openssh-10.1.tar.gz) = 8eef44a945a9a9a5a99213ab0d57e35b7ba60e75
SHA256 (openssh-10.1.tar.gz) = j9ymvhvdGMeAvh1oTI2YmOAwv7Ao70gbGPyPedgQsBU
SHA1 (openssh-10.1p1.tar.gz) = 7fd17b99d1beffb47cd380d64079e920bb0bd91f
SHA256 (openssh-10.1p1.tar.gz) = ufx6K4JXlGem8vQ+SoHI4d/aYU3bT5slWq/XAgu/B1g
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
Reporting Bugs:
==============
- Please read https://www.openssh.com/report.html
Security bugs should be reported directly to openssh at openssh.com