OpenSSH 9.5/9.5p1 (2023-10-04)
OpenSSH 9.5 was released on 2023-10-04. 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
Changes since OpenSSH 9.4
=========================
This release fixes a number of bugs and adds some small features.
Potentially incompatible changes
--------------------------------
* ssh-keygen(1): generate Ed25519 keys by default. Ed25519 public keys
are very convenient due to their small size. Ed25519 keys are
specified in RFC 8709 and OpenSSH has supported them since version 6.5
(January 2014).
* sshd(8): the Subsystem directive now accurately preserves quoting of
subsystem commands and arguments. This may change behaviour for exotic
configurations, but the most common subsystem configuration
(sftp-server) is unlikely to be affected.
New features
------------
* ssh(1): add keystroke timing obfuscation to the client. This attempts
to hide inter-keystroke timings by sending interactive traffic at
fixed intervals (default: every 20ms) when there is only a small
amount of data being sent. It also sends fake "chaff" keystrokes for
a random interval after the last real keystroke. These are
controlled by a new ssh_config ObscureKeystrokeTiming keyword.
* ssh(1), sshd(8): Introduce a transport-level ping facility. This adds
a pair of SSH transport protocol messages SSH2_MSG_PING/PONG to
implement a ping capability. These messages use numbers in the "local
extensions" number space and are advertised using a "ping@openssh.com"
ext-info message with a string version number of "0".
* sshd(8): allow override of Subsystem directives in sshd Match blocks.
Bugfixes
--------
* scp(1): fix scp in SFTP mode recursive upload and download of
directories that contain symlinks to other directories. In scp mode,
the links would be followed, but in SFTP mode they were not. bz3611
* ssh-keygen(1): handle cr+lf (instead of just cr) line endings in
sshsig signature files.
* ssh(1): interactive mode for ControlPersist sessions if they
originally requested a tty.
* sshd(8): make PerSourceMaxStartups first-match-wins
* sshd(8): limit artificial login delay to a reasonable maximum (5s)
and don't delay at all for the "none" authentication mechanism.cw
bz3602
* sshd(8): Log errors in kex_exchange_identification() with level
verbose instead of error to reduce preauth log spam. All of those
get logged with a more generic error message by sshpkt_fatal().
* sshd(8): correct math for ClientAliveInterval that caused the probes
to be sent less frequently than configured.
* ssh(1): fix regression in OpenSSH 9.4 (mux.c r1.99) that caused
multiplexed sessions to ignore SIGINT under some circumstances.
Portability
-----------
* Avoid clang zero-call-used-regs=all bug on Apple compilers, which
for some reason have version numbers that do not match the upstream
clang version numbers. bz#3584
* Fix configure test for zlib 1.3 and later/development versions. bz3604
Checksums:
==========
- SHA1 (openssh-9.5.tar.gz) = 8a0bd3a91fac338d97d91817af58df731f6509a3
- SHA256 (openssh-9.5.tar.gz) = sVMxeM3d6g65qBMktJIofxmK4Ipg9dblKif0VnhPeO0=
- SHA1 (openssh-9.5p1.tar.gz) = 35c16dcc6e7d0a9465faa241476ef24f76b196cc
- SHA256 (openssh-9.5p1.tar.gz) = 8Cbnt5un+1QPdRgq+W3IqPHbOV+SK7yfbKYDZyaGCGs=
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@openssh.com
OpenSSH 9.4/9.4p1 (2023-08-10)
OpenSSH 9.4 was released on 2023-08-10. 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
Changes since OpenSSH 9.3p2
===========================
This release fixes a number of bugs and adds some small features.
Potentially incompatible changes
--------------------------------
* This release removes support for older versions of libcrypto.
OpenSSH now requires LibreSSL >= 3.1.0 or OpenSSL >= 1.1.1.
Note that these versions are already deprecated by their upstream
vendors.
* ssh-agent(1): PKCS#11 modules must now be specified by their full
paths. Previously dlopen(3) could search for them in system
library directories.
New features
------------
* ssh(1): allow forwarding Unix Domain sockets via ssh -W.
* ssh(1): add support for configuration tags to ssh(1).
This adds a ssh_config(5) "Tag" directive and corresponding
"Match tag" predicate that may be used to select blocks of
configuration similar to the pf.conf(5) keywords of the same
name.
* ssh(1): add a "match localnetwork" predicate. This allows matching
on the addresses of available network interfaces and may be used to
vary the effective client configuration based on network location.
* ssh(1), sshd(8), ssh-keygen(1): infrastructure support for KRL
extensions. This defines wire formats for optional KRL extensions
and implements parsing of the new submessages. No actual extensions
are supported at this point.
* sshd(8): AuthorizedPrincipalsCommand and AuthorizedKeysCommand now
accept two additional %-expansion sequences: %D which expands to
the routing domain of the connected session and %C which expands
to the addresses and port numbers for the source and destination
of the connection.
* ssh-keygen(1): increase the default work factor (rounds) for the
bcrypt KDF used to derive symmetric encryption keys for passphrase
protected key files by 50%.
Bugfixes
--------
* ssh-agent(1): improve isolation between loaded PKCS#11 modules
by running separate ssh-pkcs11-helpers for each loaded provider.
* ssh(1): make -f (fork after authentication) work correctly with
multiplexed connections, including ControlPersist. bz3589 bz3589
* ssh(1): make ConnectTimeout apply to multiplexing sockets and not
just to network connections.
* ssh-agent(1), ssh(1): improve defences against invalid PKCS#11
modules being loaded by checking that the requested module
contains the required symbol before loading it.
* sshd(8): fix AuthorizedPrincipalsCommand when AuthorizedKeysCommand
appears before it in sshd_config. Since OpenSSH 8.7 the
AuthorizedPrincipalsCommand directive was incorrectly ignored in
this situation. bz3574
* sshd(8), ssh(1), ssh-keygen(1): remove vestigal support for KRL
signatures When the KRL format was originally defined, it included
support for signing of KRL objects. However, the code to sign KRLs
and verify KRL signatues was never completed in OpenSSH. This
release removes the partially-implemented code to verify KRLs.
All OpenSSH tools now ignore KRL_SECTION_SIGNATURE sections in
KRL files.
* All: fix a number of memory leaks and unreachable/harmless integer
overflows.
* ssh-agent(1), ssh(1): don't truncate strings logged from PKCS#11
modules; GHPR406
* sshd(8), ssh(1): better validate CASignatureAlgorithms in
ssh_config and sshd_config. Previously this directive would accept
certificate algorithm names, but these were unusable in practice as
OpenSSH does not support CA chains. bz3577
* ssh(1): make `ssh -Q CASignatureAlgorithms` only list signature
algorithms that are valid for CA signing. Previous behaviour was
to list all signing algorithms, including certificate algorithms.
* ssh-keyscan(1): gracefully handle systems where rlimits or the
maximum number of open files is larger than INT_MAX; bz3581
* ssh-keygen(1): fix "no comment" not showing on when running
`ssh-keygen -l` on multiple keys where one has a comment and other
following keys do not. bz3580
* scp(1), sftp(1): adjust ftruncate() logic to handle servers that
reorder requests. Previously, if the server reordered requests then
the resultant file would be erroneously truncated.
* ssh(1): don't incorrectly disable hostname canonicalization when
CanonicalizeHostname=yes and ProxyJump was expicitly set to
"none". bz3567
* scp(1): when copying local->remote, check that the source file
exists before opening an SFTP connection to the server. Based on
GHPR#370
Portability
-----------
* All: a number of build fixes for various platforms and
configuration combinations.
* sshd(8): provide a replacement for the SELinux matchpathcon()
function, which is deprecated.
* All: relax libcrypto version checks for OpenSSL >=3. Beyond
OpenSSL 3.0, the ABI compatibility guarantees are wider (only
the library major must match instead of major and minor in
earlier versions). bz#3548.
* Tests: fix build problems for the sk-dummy.so FIDO provider module
used in some tests.
Checksums:
==========
- SHA1 (openssh-9.4.tar.gz) = d88126d8d7b8e5bf4656587ac4a16055560641cc
- SHA256 (openssh-9.4.tar.gz) = 7eqFjx2hAunw+1Jy7f1JQXq//3AMr9B3dKtASDtq8go=
- SHA1 (openssh-9.4p1.tar.gz) = 5dea1f3c88f9cfe53a711a3c893ee8b7d3ffecff
- SHA256 (openssh-9.4p1.tar.gz) = Ngj9kIjbIWPOs+YAyFq3nQ3j0iHlkZLqGSPiMmOGaoU=
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@openssh.com
The previous version was OpenSSH 9.1
OpenSSH 9.3p2 (2023-07-19)
OpenSSH 9.3p2 was released on 2023-07-19. 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
Changes since OpenSSH 9.3
=========================
This release fixes a security bug.
Security
========
Fix CVE-2023-38408 - a condition where specific libaries loaded via
ssh-agent(1)'s PKCS#11 support could be abused to achieve remote
code execution via a forwarded agent socket if the following
conditions are met:
* Exploitation requires the presence of specific libraries on
the victim system.
* Remote exploitation requires that the agent was forwarded
to an attacker-controlled system.
Exploitation can also be prevented by starting ssh-agent(1) with an
empty PKCS#11/FIDO allowlist (ssh-agent -P '') or by configuring
an allowlist that contains only specific provider libraries.
This vulnerability was discovered and demonstrated to be exploitable
by the Qualys Security Advisory team.
In addition to removing the main precondition for exploitation,
this release removes the ability for remote ssh-agent(1) clients
to load PKCS#11 modules by default (see below).
Potentially-incompatible changes
--------------------------------
* ssh-agent(8): the agent will now refuse requests to load PKCS#11
modules issued by remote clients by default. A flag has been added
to restore the previous behaviour "-Oallow-remote-pkcs11".
Note that ssh-agent(8) depends on the SSH client to identify
requests that are remote. The OpenSSH >=8.9 ssh(1) client does
this, but forwarding access to an agent socket using other tools
may circumvent this restriction.
Checksums:
==========
- SHA1 (openssh-9.3p2.tar.gz) = 219cf700c317f400bb20b001c0406056f7188ea4
- SHA256 (openssh-9.3p2.tar.gz) = IA6+FH9ss/EB/QzfngJEKvfdyimN/9n0VoeOfMrGdug=
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@openssh.com
OpenSSH 9.3/9.3p1 (2023-03-15)
OpenSSH 9.3 was released on 2023-03-15. 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
Changes since OpenSSH 9.2
=========================
This release fixes a number of security bugs.
Security
========
This release contains fixes for a security problem and a memory
safety problem. The memory safety problem is not believed to be
exploitable, but we report most network-reachable memory faults as
security bugs.
* ssh-add(1): when adding smartcard keys to ssh-agent(1) with the
per-hop destination constraints (ssh-add -h ...) added in OpenSSH
8.9, a logic error prevented the constraints from being
communicated to the agent. This resulted in the keys being added
without constraints. The common cases of non-smartcard keys and
keys without destination constraints are unaffected. This problem
was reported by Luci Stanescu.
* ssh(1): Portable OpenSSH provides an implementation of the
getrrsetbyname(3) function if the standard library does not
provide it, for use by the VerifyHostKeyDNS feature. A
specifically crafted DNS response could cause this function to
perform an out-of-bounds read of adjacent stack data, but this
condition does not appear to be exploitable beyond denial-of-
service to the ssh(1) client.
The getrrsetbyname(3) replacement is only included if the system's
standard library lacks this function and portable OpenSSH was not
compiled with the ldns library (--with-ldns). getrrsetbyname(3) is
only invoked if using VerifyHostKeyDNS to fetch SSHFP records. This
problem was found by the Coverity static analyzer.
New features
------------
* ssh-keygen(1), ssh-keyscan(1): accept -Ohashalg=sha1|sha256 when
outputting SSHFP fingerprints to allow algorithm selection. bz3493
* sshd(8): add a `sshd -G` option that parses and prints the
effective configuration without attempting to load private keys
and perform other checks. This allows usage of the option before
keys have been generated and for configuration evaluation and
verification by unprivileged users.
Bugfixes
--------
* scp(1), sftp(1): fix progressmeter corruption on wide displays;
bz3534
* ssh-add(1), ssh-keygen(1): use RSA/SHA256 when testing usability
of private keys as some systems are starting to disable RSA/SHA1
in libcrypto.
* sftp-server(8): fix a memory leak. GHPR363
* ssh(1), sshd(8), ssh-keyscan(1): remove vestigal protocol
compatibility code and simplify what's left.
* Fix a number of low-impact Coverity static analysis findings.
These include several reported via bz2687
* ssh_config(5), sshd_config(5): mention that some options are not
first-match-wins.
* Rework logging for the regression tests. Regression tests will now
capture separate logs for each ssh and sshd invocation in a test.
* ssh(1): make `ssh -Q CASignatureAlgorithms` work as the manpage
says it should; bz3532.
* ssh(1): ensure that there is a terminating newline when adding a
new entry to known_hosts; bz3529
Portability
-----------
* sshd(8): harden Linux seccomp sandbox. Move to an allowlist of
mmap(2), madvise(2) and futex(2) flags, removing some concerning
kernel attack surface.
* sshd(8): improve Linux seccomp-bpf sandbox for older systems;
bz3537
Checksums:
==========
- SHA1 (openssh-9.3.tar.gz) = 5f9d2f73ddfe94f3f0a78bdf46704b6ad7b66ec7
- SHA256 (openssh-9.3.tar.gz) = eRcXkFZByz70DUBUcyIdvU0pVxP2X280FrmV8pyUdrk=
- SHA1 (openssh-9.3p1.tar.gz) = 610959871bf8d6baafc3525811948f85b5dd84ab
- SHA256 (openssh-9.3p1.tar.gz) = 6bq6dwGnalHz2Fpiw4OjydzZf6kAuFm8fbEUwYaK+Kg=
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@openssh.com
OpenSSH 9.2/9.2p1 (2023-02-02)
OpenSSH 9.2 was released on 2023-02-02. 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
Changes since OpenSSH 9.1
=========================
This release fixes a number of security bugs.
Security
========
This release contains fixes for two security problems and a memory
safety problem. The memory safety problem is not believed to be
exploitable, but we report most network-reachable memory faults as
security bugs.
* sshd(8): fix a pre-authentication double-free memory fault
introduced in OpenSSH 9.1. This is not believed to be exploitable,
and it occurs in the unprivileged pre-auth process that is
subject to chroot(2) and is further sandboxed on most major
platforms.
* ssh(8): in OpenSSH releases after 8.7, the PermitRemoteOpen option
would ignore its first argument unless it was one of the special
keywords "any" or "none", causing the permission list to fail open
if only one permission was specified. bz3515
* ssh(1): if the CanonicalizeHostname and CanonicalizePermittedCNAMEs
options were enabled, and the system/libc resolver did not check
that names in DNS responses were valid, then use of these options
could allow an attacker with control of DNS to include invalid
characters (possibly including wildcards) in names added to
known_hosts files when they were updated. These names would still
have to match the CanonicalizePermittedCNAMEs allow-list, so
practical exploitation appears unlikely.
Potentially-incompatible changes
--------------------------------
* ssh(1): add a new EnableEscapeCommandline ssh_config(5) option that
controls whether the client-side ~C escape sequence that provides a
command-line is available. Among other things, the ~C command-line
could be used to add additional port-forwards at runtime.
This option defaults to "no", disabling the ~C command-line that
was previously enabled by default. Turning off the command-line
allows platforms that support sandboxing of the ssh(1) client
(currently only OpenBSD) to use a stricter default sandbox policy.
New features
------------
* sshd(8): add support for channel inactivity timeouts via a new
sshd_config(5) ChannelTimeout directive. This allows channels that
have not seen traffic in a configurable interval to be
automatically closed. Different timeouts may be applied to session,
X11, agent and TCP forwarding channels.
* sshd(8): add a sshd_config UnusedConnectionTimeout option to
terminate client connections that have no open channels for a
length of time. This complements the ChannelTimeout option above.
* sshd(8): add a -V (version) option to sshd like the ssh client has.
* ssh(1): add a "Host" line to the output of ssh -G showing the
original hostname argument. bz3343
* scp(1), sftp(1): add a -X option to both scp(1) and sftp(1) to
allow control over some SFTP protocol parameters: the copy buffer
length and the number of in-flight requests, both of which are used
during upload/download. Previously these could be controlled in
sftp(1) only. This makes them available in both SFTP protocol
clients using the same option character sequence.
* ssh-keyscan(1): allow scanning of complete CIDR address ranges,
e.g. "ssh-keyscan 192.168.0.0/24". If a CIDR range is passed, then
it will be expanded to all possible addresses in the range
including the all-0s and all-1s addresses. bz#976
* ssh(1): support dynamic remote port forwarding in escape
command-line's -R processing. bz#3499
Bugfixes
--------
* ssh(1): when restoring non-blocking mode to stdio fds, restore
exactly the flags that ssh started with and don't just clobber them
with zero, as this could also remove the append flag from the set.
bz3523
* ssh(1): avoid printf("%s", NULL) if using UserKnownHostsFile=none
and a hostkey in one of the system known hosts file changes.
* scp(1): switch scp from using pipes to a socket-pair for
communication with its ssh sub-processes, matching how sftp(1)
operates.
* sshd(8): clear signal mask early in main(); sshd may have been
started with one or more signals masked (sigprocmask(2) is not
cleared on fork/exec) and this could interfere with various things,
e.g. the login grace timer. Execution environments that fail to
clear the signal mask before running sshd are clearly broken, but
apparently they do exist.
* ssh(1): warn if no host keys for hostbased auth can be loaded.
* sshd(8): Add server debugging for hostbased auth that is queued and
sent to the client after successful authentication, but also logged
to assist in diagnosis of HostbasedAuthentication problems. bz3507
* ssh(1): document use of the IdentityFile option as being usable to
list public keys as well as private keys. GHPR352
* sshd(8): check for and disallow MaxStartups values less than or
equal to zero during config parsing, rather than failing later at
runtime. bz3489
* ssh-keygen(1): fix parsing of hex cert expiry times specified on
the command-line when acting as a CA.
* scp(1): when scp(1) is using the SFTP protocol for transport (the
default), better match scp/rcp's handling of globs that don't match
the globbed characters but do match literally (e.g. trying to
transfer a file named "foo.[1]"). Previously scp(1) in SFTP mode
would not match these pathnames but legacy scp/rcp mode would.
bz3488
* ssh-agent(1): document the "-O no-restrict-websafe" command-line
option.
* ssh(1): honour user's umask(2) if it is more restrictive then the
ssh default (022).
Portability
-----------
* sshd(8): allow writev(2) in the Linux seccomp sandbox. This seems
to be used by recent glibcs at least in some configurations during
error conditions. bz3512.
* sshd(8): simply handling of SSH_CONNECTION PAM env var, removing
global variable and checking the return value from pam_putenv.
bz3508
* sshd(8): disable SANDBOX_SECCOMP_FILTER_DEBUG that was mistakenly
enabled during the OpenSSH 9.1 release cycle.
* misc: update autotools and regenerate the config files using the
latest autotools
* all: use -fzero-call-used-regs=used on clang 15 instead of
-fzero-call-used-reg=all, as some versions of clang 15 have
miscompile code when it was enabled. bz3475
* sshd(8): defer PRNG seeding until after the initial closefrom(2)
call. PRNG seeding will initialize OpenSSL, and some engine
providers (e.g. Intel's QAT) will open descriptors for their own
use that closefrom(2) could clobber. bz3483
* misc: in the poll(2)/ppoll(2) compatibility code, avoid assuming
the layout of fd_set.
* sftp-server(8), ssh-agent(1): fix ptrace(2) disabling on older
FreeBSD kernels. Some versions do not support using id 0 to refer
to the current PID for procctl, so try again with getpid()
explicitly before failing.
* configure.ac: fix -Wstrict-prototypes in configure test code.
Clang 16 now warns on this and legacy prototypes will be removed
in C23. GHPR355
* configure.ac: fix setres*id checks to work with clang-16. glibc
has the prototypes for setresuid behind _GNU_SOURCE, and clang 16
will error out on implicit function definitions. bz3497
Checksums:
==========
- SHA1 (openssh-9.2.tar.gz) = e4b806b7c81b87d6c90afe97b3d016ba6cf3ba1c
- SHA256 (openssh-9.2.tar.gz) = yYe9uaaWSeetXGXOxuaaEiIsLnvITmGW+l5dgMZb9QU=
- SHA1 (openssh-9.2p1.tar.gz) = 3b172b8e971773a7018bbf3231f6589ae539ca4b
- SHA256 (openssh-9.2p1.tar.gz) = P2bb8WVftF9Q4cVtpiqwEhjCKIB7ITONY068351xz0Y=
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@openssh.com
OpenSSH 8.2 was released on 2020-02-14. 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
=========================
It is now possible[1] to perform chosen-prefix attacks against the
SHA-1 hash algorithm for less than USD$50K. For this reason, we will
be disabling the "ssh-rsa" public key signature algorithm that depends
on SHA-1 by default in a near-future release.
This algorithm is unfortunately still used widely despite the
existence of better alternatives, being the only remaining public key
signature algorithm specified by the original SSH RFCs.
The better alternatives include:
* The RFC8332 RSA SHA-2 signature algorithms rsa-sha2-256/512. These
algorithms have the advantage of using the same key type as
"ssh-rsa" but use the safe SHA-2 hash algorithms. These have been
supported since OpenSSH 7.2 and are already used by default if the
client and server support them.
* The ssh-ed25519 signature algorithm. It has been supported in
OpenSSH since release 6.5.
* The RFC5656 ECDSA algorithms: ecdsa-sha2-nistp256/384/521. These
have been supported by OpenSSH since release 5.7.
To check whether a server is using the weak ssh-rsa public key
algorithm for host authentication, try to connect to it after
removing the ssh-rsa algorithm from ssh(1)'s allowed list:
ssh -oHostKeyAlgorithms=-ssh-rsa user@host
If the host key verification fails and no other supported host key
types are available, the server software on that host should be
upgraded.
A future release of OpenSSH will enable UpdateHostKeys by default
to allow the client to automatically migrate to better algorithms.
Users may consider enabling this option manually.
[1] "SHA-1 is a Shambles: First Chosen-Prefix Collision on SHA-1 and
Application to the PGP Web of Trust" Leurent, G and Peyrin, T
(2020) https://eprint.iacr.org/2020/014.pdf
Security
========
* 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 the aforementioned SHA1
collision vulnerability 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 futher 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.
Potentially-incompatible changes
================================
This release includes a number of changes that may affect existing
configurations:
* ssh(1), sshd(8): the above removal of "ssh-rsa" from the accepted
CASignatureAlgorithms list.
* ssh(1), sshd(8): this release removes 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.
* ssh-sk-helper(8): this is a new binary. It is used by the FIDO/U2F
support to provide address-space isolation for token middleware
libraries (including the internal one). It needs to be installed
in the expected path, typically under /usr/libexec or similar.
Changes since OpenSSH 8.1
=========================
This release contains some significant new features.
FIDO/U2F Support
----------------
This release adds support for FIDO/U2F hardware authenticators to
OpenSSH. U2F/FIDO are open standards for inexpensive two-factor
authentication hardware that are widely used for website
authentication. In OpenSSH FIDO devices are supported by new public
key types "ecdsa-sk" and "ed25519-sk", along with corresponding
certificate types.
ssh-keygen(1) may be used to generate a FIDO token-backed key, after
which they may be used much like any other key type supported by
OpenSSH, so long as the hardware token is attached when the keys are
used. FIDO tokens also generally require the user explicitly authorise
operations by touching or tapping them.
Generating a FIDO key requires the token be attached, and will usually
require the user tap the token to confirm the operation:
$ ssh-keygen -t ecdsa-sk -f ~/.ssh/id_ecdsa_sk
Generating public/private ecdsa-sk key pair.
You may need to touch your security key to authorize key generation.
Enter file in which to save the key (/home/djm/.ssh/id_ecdsa_sk):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/djm/.ssh/id_ecdsa_sk
Your public key has been saved in /home/djm/.ssh/id_ecdsa_sk.pub
This will yield a public and private key-pair. The private key file
should be useless to an attacker who does not have access to the
physical token. After generation, this key may be used like any other
supported key in OpenSSH and may be listed in authorized_keys, added
to ssh-agent(1), etc. The only additional stipulation is that the FIDO
token that the key belongs to must be attached when the key is used.
FIDO tokens are most commonly connected via USB but may be attached
via other means such as Bluetooth or NFC. In OpenSSH, communication
with the token is managed via a middleware library, specified by the
SecurityKeyProvider directive in ssh/sshd_config(5) or the
$SSH_SK_PROVIDER environment variable for ssh-keygen(1) and
ssh-add(1). The API for this middleware is documented in the sk-api.h
and PROTOCOL.u2f files in the source distribution.
OpenSSH includes a middleware ("SecurityKeyProvider=internal") with
support for USB tokens. It is automatically enabled in OpenBSD and may
be enabled in portable OpenSSH via the configure flag
--with-security-key-builtin. If the internal middleware is enabled
then it is automatically used by default. This internal middleware
requires that libfido2 (https://github.com/Yubico/libfido2) and its
dependencies be installed. We recommend that packagers of portable
OpenSSH enable the built-in middleware, as it provides the
lowest-friction experience for users.
Note: FIDO/U2F tokens are required to implement the ECDSA-P256
"ecdsa-sk" key type, but hardware support for Ed25519 "ed25519-sk" is
less common. Similarly, not all hardware tokens support some of the
optional features such as resident keys.
The protocol-level changes to support FIDO/U2F keys in SSH are
documented in the PROTOCOL.u2f file in the OpenSSH source
distribution.
There are a number of supporting changes to this feature:
* ssh-keygen(1): add a "no-touch-required" option when generating
FIDO-hosted keys, that disables their default behaviour of
requiring a physical touch/tap on the token during authentication.
Note: not all tokens support disabling the touch requirement.
* sshd(8): add a sshd_config PubkeyAuthOptions directive that
collects miscellaneous public key authentication-related options
for sshd(8). At present it supports only a single option
"no-touch-required". This causes sshd to skip its default check for
FIDO/U2F keys that the signature was authorised by a touch or press
event on the token hardware.
* ssh(1), sshd(8), ssh-keygen(1): add a "no-touch-required" option
for authorized_keys and a similar extension for certificates. This
option disables the default requirement that FIDO key signatures
attest that the user touched their key to authorize them, mirroring
the similar PubkeyAuthOptions sshd_config option.
* ssh-keygen(1): add support for the writing the FIDO attestation
information that is returned when new keys are generated via the
"-O write-attestation=/path" option. FIDO attestation certificates
may be used to verify that a FIDO key is hosted in trusted
hardware. OpenSSH does not currently make use of this information,
beyond optionally writing it to disk.
FIDO2 resident keys
-------------------
FIDO/U2F OpenSSH keys consist of two parts: a "key handle" part stored
in the private key file on disk, and a per-device private key that is
unique to each FIDO/U2F token and that cannot be exported from the
token hardware. These are combined by the hardware at authentication
time to derive the real key that is used to sign authentication
challenges.
For tokens that are required to move between computers, it can be
cumbersome to have to move the private key file first. To avoid this
requirement, tokens implementing the newer FIDO2 standard support
"resident keys", where it is possible to effectively retrieve the key
handle part of the key from the hardware.
OpenSSH supports this feature, allowing resident keys to be generated
using the ssh-keygen(1) "-O resident" flag. This will produce a
public/private key pair as usual, but it will be possible to retrieve
the private key part from the token later. This may be done using
"ssh-keygen -K", which will download all available resident keys from
the tokens attached to the host and write public/private key files
for them. It is also possible to download and add resident keys
directly to ssh-agent(1) without writing files to the file-system
using "ssh-add -K".
Resident keys are indexed on the token by the application string and
user ID. By default, OpenSSH uses an application string of "ssh:" and
an empty user ID. If multiple resident keys on a single token are
desired then it may be necessary to override one or both of these
defaults using the ssh-keygen(1) "-O application=" or "-O user="
options. Note: OpenSSH will only download and use resident keys whose
application string begins with "ssh:"
Storing both parts of a key on a FIDO token increases the likelihood
of an attacker being able to use a stolen token device. For this
reason, tokens should enforce PIN authentication before allowing
download of keys, and users should set a PIN on their tokens before
creating any resident keys.
Other New Features
------------------
* sshd(8): add an Include sshd_config keyword that allows including
additional configuration files via glob(3) patterns. bz2468
* ssh(1)/sshd(8): make the LE (low effort) DSCP code point available
via the IPQoS directive; bz2986,
* ssh(1): when AddKeysToAgent=yes is set and the key contains no
comment, add the key to the agent with the key's path as the
comment. bz2564
* ssh-keygen(1), ssh-agent(1): expose PKCS#11 key labels and X.509
subjects as key comments, rather than simply listing the PKCS#11
provider library path. PR138
* ssh-keygen(1): allow PEM export of DSA and ECDSA keys; bz3091
* ssh(1), sshd(8): make zlib compile-time optional, available via the
Makefile.inc ZLIB flag on OpenBSD or via the --with-zlib configure
option for OpenSSH portable.
* sshd(8): when clients get denied by MaxStartups, send a
notification prior to the SSH2 protocol banner according to
RFC4253 section 4.2.
* ssh(1), ssh-agent(1): when invoking the $SSH_ASKPASS prompt
program, pass a hint to the program to describe the type of
desired prompt. The possible values are "confirm" (indicating
that a yes/no confirmation dialog with no text entry should be
shown), "none" (to indicate an informational message only), or
blank for the original ssh-askpass behaviour of requesting a
password/phrase.
* ssh(1): allow forwarding a different agent socket to the path
specified by $SSH_AUTH_SOCK, by extending the existing ForwardAgent
option to accepting an explicit path or the name of an environment
variable in addition to yes/no.
* ssh-keygen(1): add a new signature operations "find-principals" to
look up the principal associated with a signature from an allowed-
signers file.
* sshd(8): expose the number of currently-authenticating connections
along with the MaxStartups limit in the process title visible to
"ps".
Bugfixes
--------
* sshd(8): make ClientAliveCountMax=0 have sensible semantics: it
will now disable connection killing entirely rather than the
current behaviour of instantly killing the connection after the
first liveness test regardless of success. bz2627
* sshd(8): clarify order of AllowUsers / DenyUsers vs AllowGroups /
DenyGroups in the sshd(8) manual page. bz1690
* sshd(8): better describe HashKnownHosts in the manual page. bz2560
* sshd(8): clarify that that permitopen=/PermitOpen do no name or
address translation in the manual page. bz3099
* sshd(8): allow the UpdateHostKeys feature to function when
multiple known_hosts files are in use. When updating host keys,
ssh will now search subsequent known_hosts files, but will add
updated host keys to the first specified file only. bz2738
* All: replace all calls to signal(2) with a wrapper around
sigaction(2). This wrapper blocks all other signals during the
handler preventing races between handlers, and sets SA_RESTART
which should reduce the potential for short read/write operations.
* sftp(1): fix a race condition in the SIGCHILD handler that could
turn in to a kill(-1); bz3084
* sshd(8): fix a case where valid (but extremely large) SSH channel
IDs were being incorrectly rejected. bz3098
* ssh(1): when checking host key fingerprints as answers to new
hostkey prompts, ignore whitespace surrounding the fingerprint
itself.
* All: wait for file descriptors to be readable or writeable during
non-blocking connect, not just readable. Prevents a timeout when
the server doesn't immediately send a banner (e.g. multiplexers
like sslh)
* sshd_config(5): document the sntrup4591761x25519-sha512@tinyssh.org
key exchange algorithm. PR#151
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:
http://www.openssh.com/donations.html
Security
========
* ssh(1), sshd(8), ssh-add(1), ssh-keygen(1): an exploitable integer
overflow bug was found in the private key parsing code for the XMSS
key type. This key type is still experimental and support for it is
not compiled by default. No user-facing autoconf option exists in
portable OpenSSH to enable it. This bug was found by Adam Zabrocki
and reported via SecuriTeam's SSD program.
* ssh(1), sshd(8), ssh-agent(1): add protection for private keys at
rest in RAM against speculation and memory side-channel attacks like
Spectre, Meltdown and Rambleed. This release encrypts private keys
when they are not in use with a symmetric key that is derived from a
relatively large "prekey" consisting of random data (currently 16KB).
Potentially-incompatible changes
================================
This release 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 ...").
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 "PKCS11Provider=none" to override later instances of
the PKCS11Provider 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@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
mirrors listed at http://www.openssh.com/ shortly.
OpenSSH is a 100% complete SSH protocol 2.0 implementation and
includes sftp client and server support. OpenSSH also includes
transitional support for the legacy SSH 1.3 and 1.5 protocols
that may be enabled at compile-time.
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:
http://www.openssh.com/donations.html
Future deprecation notice
=========================
We plan on retiring more legacy cryptography in a near-future
release, specifically:
* Refusing all RSA keys smaller than 1024 bits (the current minimum
is 768 bits)
* Removing server-side support for the SSH v.1 protocol (currently
compile-time disabled).
* In approximately 1 year, removing all support for the SSH v.1
protocol (currently compile-time disabled).
This list reflects our current intentions, but please check the final
release notes for future releases.
Changes since OpenSSH 7.2
=========================
This is primarily a bugfix release.
Security
--------
* sshd(8): Mitigate a potential denial-of-service attack against
the system's crypt(3) function via sshd(8). An attacker could
send very long passwords that would cause excessive CPU use in
crypt(3). sshd(8) now refuses to accept password authentication
requests of length greater than 1024 characters. Independently
reported by Tomas Kuthan (Oracle), Andres Rojas and Javier Nieto.
* sshd(8): Mitigate timing differences in password authentication
that could be used to discern valid from invalid account names
when long passwords were sent and particular password hashing
algorithms are in use on the server. CVE-2016-6210, reported by
EddieEzra.Harari at verint.com
* ssh(1), sshd(8): Fix observable timing weakness in the CBC padding
oracle countermeasures. Reported by Jean Paul Degabriele, Kenny
Paterson, Torben Hansen and Martin Albrecht. Note that CBC ciphers
are disabled by default and only included for legacy compatibility.
* ssh(1), sshd(8): Improve operation ordering of MAC verification for
Encrypt-then-MAC (EtM) mode transport MAC algorithms to verify the
MAC before decrypting any ciphertext. This removes the possibility
of timing differences leaking facts about the plaintext, though no
such leakage has been observed. Reported by Jean Paul Degabriele,
Kenny Paterson, Torben Hansen and Martin Albrecht.
* sshd(8): (portable only) Ignore PAM environment vars when
UseLogin=yes. If PAM is configured to read user-specified
environment variables and UseLogin=yes in sshd_config, then a
hostile local user may attack /bin/login via LD_PRELOAD or
similar environment variables set via PAM. CVE-2015-8325,
found by Shayan Sadigh.
New Features
------------
* ssh(1): Add a ProxyJump option and corresponding -J command-line
flag to allow simplified indirection through a one or more SSH
bastions or "jump hosts".
* ssh(1): Add an IdentityAgent option to allow specifying specific
agent sockets instead of accepting one from the environment.
* ssh(1): Allow ExitOnForwardFailure and ClearAllForwardings to be
optionally overridden when using ssh -W. bz#2577
* ssh(1), sshd(8): Implement support for the IUTF8 terminal mode as
per draft-sgtatham-secsh-iutf8-00.
* ssh(1), sshd(8): Add support for additional fixed Diffie-Hellman
2K, 4K and 8K groups from draft-ietf-curdle-ssh-kex-sha2-03.
* ssh-keygen(1), ssh(1), sshd(8): support SHA256 and SHA512 RSA
signatures in certificates;
* ssh(1): Add an Include directive for ssh_config(5) files.
* ssh(1): Permit UTF-8 characters in pre-authentication banners sent
from the server. bz#2058
Bugfixes
--------
* ssh(1), sshd(8): Reduce the syslog level of some relatively common
protocol events from LOG_CRIT. bz#2585
* sshd(8): Refuse AuthenticationMethods="" in configurations and
accept AuthenticationMethods=any for the default behaviour of not
requiring multiple authentication. bz#2398
* sshd(8): Remove obsolete and misleading "POSSIBLE BREAK-IN
ATTEMPT!" message when forward and reverse DNS don't match. bz#2585
* ssh(1): Close ControlPersist background process stderr except
in debug mode or when logging to syslog. bz#1988
* misc: Make PROTOCOL description for direct-streamlocal@openssh.com
channel open messages match deployed code. bz#2529
* ssh(1): Deduplicate LocalForward and RemoteForward entries to fix
failures when both ExitOnForwardFailure and hostname
canonicalisation are enabled. bz#2562
* sshd(8): Remove fallback from moduli to obsolete "primes" file
that was deprecated in 2001. bz#2559.
* sshd_config(5): Correct description of UseDNS: it affects ssh
hostname processing for authorized_keys, not known_hosts; bz#2554
* ssh(1): Fix authentication using lone certificate keys in an agent
without corresponding private keys on the filesystem. bz#2550
* sshd(8): Send ClientAliveInterval pings when a time-based
RekeyLimit is set; previously keepalive packets were not being
sent. bz#2252
Portability
-----------
* ssh(1), sshd(8): Fix compilation by automatically disabling ciphers
not supported by OpenSSL. bz#2466
* misc: Fix compilation failures on some versions of AIX's compiler
related to the definition of the VA_COPY macro. bz#2589
* sshd(8): Whitelist more architectures to enable the seccomp-bpf
sandbox. bz#2590
* ssh-agent(1), sftp-server(8): Disable process tracing on Solaris
using setpflags(__PROC_PROTECT, ...). bz#2584
* sshd(8): On Solaris, don't call Solaris setproject() with
UsePAM=yes it's PAM's responsibility. bz#2425
Checksums:
==========
- SHA1 (openssh-7.3.tar.gz) = b1641e5265d9ec68a9a19decc3a7edd1203cbd33
- SHA256 (openssh-7.3.tar.gz) = vS0X35qrX9OOPBkyDMYhOje/DBwHBVEV7nv5rkzw4vM=
- SHA1 (openssh-7.3p1.tar.gz) = bfade84283fcba885e2084343ab19a08c7d123a5
- SHA256 (openssh-7.3p1.tar.gz) = P/uYmm3KppWUw7VQ1IVaWi4XGMzd5/XjY4e0JCIPvsw=
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 as RELEASE_KEY.asc from
the mirror sites.
Reporting Bugs:
===============
- Please read http://www.openssh.com/report.html
Security bugs should be reported directly to openssh@openssh.com
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.
=========================
This is a major release, containing a number of new features as
well as a large internal re-factoring.
Potentially-incompatible changes
--------------------------------
* sshd(8): 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.
New Features
------------
* Much of OpenSSH's internal code has been re-factored to be more
library-like. These changes are mostly not user-visible, but
have greatly improved OpenSSH's testability and internal layout.
* Add FingerprintHash option to ssh(1) and sshd(8), and equivalent
command-line flags to the other tools to control algorithm used
for key fingerprints. The default changes from MD5 to SHA256 and
format from hex to base64.
Fingerprints now have the hash algorithm prepended. An example of
the new format: SHA256:mVPwvezndPv/ARoIadVY98vAC0g+P/5633yTC4d/wXE
Please note that visual host keys will also be different.
* ssh(1), sshd(8): Experimental host key rotation support. Add a
protocol extension for a server to inform a client of all its
available host keys after authentication has completed. The client
may record the keys in known_hosts, allowing it to upgrade to better
host key algorithms and a server to gracefully rotate its keys.
The client side of this is controlled by a UpdateHostkeys config
option (default off).
* ssh(1): Add a ssh_config HostbasedKeyType option to control which
host public key types are tried during host-based authentication.
* ssh(1), sshd(8): fix connection-killing host key mismatch errors
when sshd offers multiple ECDSA keys of different lengths.
* ssh(1): when host name canonicalisation is enabled, try to
parse host names as addresses before looking them up for
canonicalisation. fixes bz#2074 and avoiding needless DNS
lookups in some cases.
* ssh-keygen(1), sshd(8): Key Revocation Lists (KRLs) no longer
require OpenSSH to be compiled with OpenSSL support.
* ssh(1), ssh-keysign(8): Make ed25519 keys work for host based
authentication.
* sshd(8): SSH protocol v.1 workaround for the Meyer, et al,
Bleichenbacher Side Channel Attack. Fake up a bignum key before
RSA decryption.
* sshd(8): Remember which public keys have been used for
authentication and refuse to accept previously-used keys.
This allows AuthenticationMethods=publickey,publickey to require
that users authenticate using two _different_ public keys.
* sshd(8): add sshd_config HostbasedAcceptedKeyTypes and
PubkeyAcceptedKeyTypes options to allow sshd to control what
public key types will be accepted. Currently defaults to all.
* sshd(8): Don't count partial authentication success as a failure
against MaxAuthTries.
* ssh(1): Add RevokedHostKeys option for the client to allow
text-file or KRL-based revocation of host keys.
* ssh-keygen(1), sshd(8): Permit KRLs that revoke certificates by
serial number or key ID without scoping to a particular CA.
* ssh(1): Add a "Match canonical" criteria that allows ssh_config
Match blocks to trigger only in the second config pass.
* ssh(1): Add a -G option to ssh that causes it to parse its
configuration and dump the result to stdout, similar to "sshd -T".
* ssh(1): Allow Match criteria to be negated. E.g. "Match !host".
* The regression test suite has been extended to cover more OpenSSH
features. The unit tests have been expanded and now cover key
exchange.
Bugfixes
* ssh-keyscan(1): ssh-keyscan has been made much more robust again
servers that hang or violate the SSH protocol.
* ssh(1), ssh-keygen(1): Fix regression bz#2306: Key path names were
being lost as comment fields.
* ssh(1): Allow ssh_config Port options set in the second config
parse phase to be applied (they were being ignored). bz#2286
* ssh(1): Tweak config re-parsing with host canonicalisation - make
the second pass through the config files always run when host name
canonicalisation is enabled (and not whenever the host name
changes) bz#2267
* ssh(1): Fix passing of wildcard forward bind addresses when
connection multiplexing is in use; bz#2324;
* ssh-keygen(1): Fix broken private key conversion from non-OpenSSH
formats; bz#2345.
* ssh-keygen(1): Fix KRL generation bug when multiple CAs are in
use.
* Various fixes to manual pages: bz#2288, bz#2316, bz#2273
Portable OpenSSH
* Support --without-openssl at configure time
Disables and removes dependency on OpenSSL. Many features,
including SSH protocol 1 are not supported and the set of crypto
options is greatly restricted. This will only work on systems
with native arc4random or /dev/urandom.
Considered highly experimental for now.
* Support --without-ssh1 option at configure time
Allows disabling support for SSH protocol 1.
* sshd(8): Fix compilation on systems with IPv6 support in utmpx; bz#2296
* Allow custom service name for sshd on Cygwin. Permits the use of
multiple sshd running with different service names.
Checksums:
==========
- SHA1 (openssh-6.8.tar.gz) = 99903c6ca76e0a2c044711017f81127e12459d37
- SHA256 (openssh-6.8.tar.gz) = N1uzVarFbrm2CzAwuDu3sRoszmqpK+5phAChP/QNyuw=
- SHA1 (openssh-6.8p1.tar.gz) = cdbc51e46a902b30d263b05fdc71340920e91c92
- SHA256 (openssh-6.8p1.tar.gz) = P/ZM5z7hJEgLW/dnuYMNfTwDu8tqvnFrePAZLDfOFg4=
Please note that the PGP key used to sign releases was recently rotated.
The new key has been signed by the old key to provide continuity. It is
available from the mirror sites as RELEASE_KEY.asc.
Reporting Bugs:
===============
- Please read http://www.openssh.com/report.html
Security bugs should be reported directly to openssh@openssh.com
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.
=========================
Potentially-incompatible changes
* sshd(8): The default set of ciphers and MACs has been altered to
remove unsafe algorithms. In particular, CBC ciphers and arcfour*
are disabled by default.
The full set of algorithms remains available if configured
explicitly via the Ciphers and MACs sshd_config options.
* sshd(8): Support for tcpwrappers/libwrap has been removed.
* OpenSSH 6.5 and 6.6 have a bug that causes ~0.2% of connections
using the curve25519-sha256@libssh.org KEX exchange method to fail
when connecting with something that implements the specification
correctly. OpenSSH 6.7 disables this KEX method when speaking to
one of the affected versions.
New Features
* Major internal refactoring to begin to make part of OpenSSH usable
as a library. So far the wire parsing, key handling and KRL code
has been refactored. Please note that we do not consider the API
stable yet, nor do we offer the library in separable form.
* ssh(1), sshd(8): Add support for Unix domain socket forwarding.
A remote TCP port may be forwarded to a local Unix domain socket
and vice versa or both ends may be a Unix domain socket.
* ssh(1), ssh-keygen(1): Add support for SSHFP DNS records for
ED25519 key types.
* sftp(1): Allow resumption of interrupted uploads.
* ssh(1): When rekeying, skip file/DNS lookups of the hostkey if it
is the same as the one sent during initial key exchange; bz#2154
* sshd(8): Allow explicit ::1 and 127.0.0.1 forwarding bind
addresses when GatewayPorts=no; allows client to choose address
family; bz#2222
* sshd(8): Add a sshd_config PermitUserRC option to control whether
~/.ssh/rc is executed, mirroring the no-user-rc authorized_keys
option; bz#2160
* ssh(1): Add a %C escape sequence for LocalCommand and ControlPath
that expands to a unique identifer based on a hash of the tuple of
(local host, remote user, hostname, port). Helps avoid exceeding
miserly pathname limits for Unix domain sockets in multiplexing
control paths; bz#2220
* sshd(8): Make the "Too many authentication failures" message
include the user, source address, port and protocol in a format
similar to the authentication success / failure messages; bz#2199
* Added unit and fuzz tests for refactored code. These are run
automatically in portable OpenSSH via the "make tests" target.
Bugfixes
* sshd(8): Fix remote forwarding with the same listen port but
different listen address.
* ssh(1): Fix inverted test that caused PKCS#11 keys that were
explicitly listed in ssh_config or on the commandline not to be
preferred.
* ssh-keygen(1): Fix bug in KRL generation: multiple consecutive
revoked certificate serial number ranges could be serialised to an
invalid format. Readers of a broken KRL caused by this bug will
fail closed, so no should-have-been-revoked key will be accepted.
* ssh(1): Reflect stdio-forward ("ssh -W host:port ...") failures in
exit status. Previously we were always returning 0; bz#2255
* ssh(1), ssh-keygen(1): Make Ed25519 keys' title fit properly in the
randomart border; bz#2247
* ssh-agent(1): Only cleanup agent socket in the main agent process
and not in any subprocesses it may have started (e.g. forked
askpass). Fixes agent sockets being zapped when askpass processes
fatal(); bz#2236
* ssh-add(1): Make stdout line-buffered; saves partial output getting
lost when ssh-add fatal()s part-way through (e.g. when listing keys
from an agent that supports key types that ssh-add doesn't);
bz#2234
* ssh-keygen(1): When hashing or removing hosts, don't choke on
@revoked markers and don't remove @cert-authority markers; bz#2241
* ssh(1): Don't fatal when hostname canonicalisation fails and a
ProxyCommand is in use; continue and allow the ProxyCommand to
connect anyway (e.g. to a host with a name outside the DNS behind
a bastion)
* scp(1): When copying local->remote fails during read, don't send
uninitialised heap to the remote end.
* sftp(1): Fix fatal "el_insertstr failed" errors when tab-completing
filenames with a single quote char somewhere in the string;
bz#2238
* ssh-keyscan(1): Scan for Ed25519 keys by default.
* ssh(1): When using VerifyHostKeyDNS with a DNSSEC resolver, down-
convert any certificate keys to plain keys and attempt SSHFP
resolution. Prevents a server from skipping SSHFP lookup and
forcing a new-hostkey dialog by offering only certificate keys.
* sshd(8): Avoid crash at exit via NULL pointer reference; bz#2225
* Fix some strict-alignment errors.
Portable OpenSSH
* Portable OpenSSH now supports building against libressl-portable.
* Portable OpenSSH now requires openssl 0.9.8f or greater. Older
versions are no longer supported.
* In the OpenSSL version check, allow fix version upgrades (but not
downgrades. Debian bug #748150.
* sshd(8): On Cygwin, determine privilege separation user at runtime,
since it may need to be a domain account.
* sshd(8): Don't attempt to use vhangup on Linux. It doesn't work for
non-root users, and for them it just messes up the tty settings.
* Use CLOCK_BOOTTIME in preference to CLOCK_MONOTONIC when it is
available. It considers time spent suspended, thereby ensuring
timeouts (e.g. for expiring agent keys) fire correctly. bz#2228
* Add support for ed25519 to opensshd.init init script.
* sftp-server(8): On platforms that support it, use prctl() to
prevent sftp-server from accessing /proc/self/{mem,maps}
Changes since OpenSSH 6.5
=========================
This is primarily a bugfix release.
Security:
* sshd(8): when using environment passing with a sshd_config(5)
AcceptEnv pattern with a wildcard. OpenSSH prior to 6.6 could be
tricked into accepting any enviornment variable that contains the
characters before the wildcard character.
New / changed features:
* ssh(1), sshd(8): this release removes the J-PAKE authentication code.
This code was experimental, never enabled and had been unmaintained
for some time.
* ssh(1): when processing Match blocks, skip 'exec' clauses other clauses
predicates failed to match.
* ssh(1): if hostname canonicalisation is enabled and results in the
destination hostname being changed, then re-parse ssh_config(5) files
using the new destination hostname. This gives 'Host' and 'Match'
directives that use the expanded hostname a chance to be applied.
Bugfixes:
* ssh(1): avoid spurious "getsockname failed: Bad file descriptor" in
ssh -W. bz#2200, debian#738692
* sshd(8): allow the shutdown(2) syscall in seccomp-bpf and systrace
sandbox modes, as it is reachable if the connection is terminated
during the pre-auth phase.
* ssh(1), sshd(8): fix unsigned overflow that in SSH protocol 1 bignum
parsing. Minimum key length checks render this bug unexploitable to
compromise SSH 1 sessions.
* sshd_config(5): clarify behaviour of a keyword that appears in
multiple matching Match blocks. bz#2184
* ssh(1): avoid unnecessary hostname lookups when canonicalisation is
disabled. bz#2205
* sshd(8): avoid sandbox violation crashes in GSSAPI code by caching
the supported list of GSSAPI mechanism OIDs before entering the
sandbox. bz#2107
* ssh(1): fix possible crashes in SOCKS4 parsing caused by assumption
that the SOCKS username is nul-terminated.
* ssh(1): fix regression for UsePrivilegedPort=yes when BindAddress is
not specified.
* ssh(1), sshd(8): fix memory leak in ECDSA signature verification.
* ssh(1): fix matching of 'Host' directives in ssh_config(5) files
to be case-insensitive again (regression in 6.5).
Portable OpenSSH:
* sshd(8): don't fatal if the FreeBSD Capsicum is offered by the
system headers and libc but is not supported by the kernel.
* Fix build using the HP-UX compiler.
Changes since OpenSSH 6.4
=========================
This is a feature-focused release.
New features:
* ssh(1), sshd(8): Add support for key exchange using elliptic-curve
Diffie Hellman in Daniel Bernstein's Curve25519. This key exchange
method is the default when both the client and server support it.
* ssh(1), sshd(8): Add support for Ed25519 as a public key type.
Ed25519 is a elliptic curve signature scheme that offers
better security than ECDSA and DSA and good performance. It may be
used for both user and host keys.
* Add a new private key format that uses a bcrypt KDF to better
protect keys at rest. This format is used unconditionally for
Ed25519 keys, but may be requested when generating or saving
existing keys of other types via the -o ssh-keygen(1) option.
We intend to make the new format the default in the near future.
Details of the new format are in the PROTOCOL.key file.
* ssh(1), sshd(8): Add a new transport cipher
"chacha20-poly1305@openssh.com" that combines Daniel Bernstein's
ChaCha20 stream cipher and Poly1305 MAC to build an authenticated
encryption mode. Details are in the PROTOCOL.chacha20poly1305 file.
* ssh(1), sshd(8): Refuse RSA keys from old proprietary clients and
servers that use the obsolete RSA+MD5 signature scheme. It will
still be possible to connect with these clients/servers but only
DSA keys will be accepted, and OpenSSH will refuse connection
entirely in a future release.
* ssh(1), sshd(8): Refuse old proprietary clients and servers that
use a weaker key exchange hash calculation.
* ssh(1): Increase the size of the Diffie-Hellman groups requested
for each symmetric key size. New values from NIST Special
Publication 800-57 with the upper limit specified by RFC4419.
* ssh(1), ssh-agent(1): Support PKCS#11 tokens that only provide
X.509 certs instead of raw public keys (requested as bz#1908).
* ssh(1): Add a ssh_config(5) "Match" keyword that allows
conditional configuration to be applied by matching on hostname,
user and result of arbitrary commands.
* ssh(1): Add support for client-side hostname canonicalisation
using a set of DNS suffixes and rules in ssh_config(5). This
allows unqualified names to be canonicalised to fully-qualified
domain names to eliminate ambiguity when looking up keys in
known_hosts or checking host certificate names.
* sftp-server(8): Add the ability to whitelist and/or blacklist sftp
protocol requests by name.
* sftp-server(8): Add a sftp "fsync@openssh.com" to support calling
fsync(2) on an open file handle.
* sshd(8): Add a ssh_config(5) PermitTTY to disallow TTY allocation,
mirroring the longstanding no-pty authorized_keys option.
* ssh(1): Add a ssh_config ProxyUseFDPass option that supports the
use of ProxyCommands that establish a connection and then pass a
connected file descriptor back to ssh(1). This allows the
ProxyCommand to exit rather than staying around to transfer data.
Bugfixes:
* ssh(1), sshd(8): Fix potential stack exhaustion caused by nested
certificates.
* ssh(1): bz#1211: make BindAddress work with UsePrivilegedPort.
* sftp(1): bz#2137: fix the progress meter for resumed transfer.
* ssh-add(1): bz#2187: do not request smartcard PIN when removing
keys from ssh-agent.
* sshd(8): bz#2139: fix re-exec fallback when original sshd binary
cannot be executed.
* ssh-keygen(1): Make relative-specified certificate expiry times
relative to current time and not the validity start time.
* sshd(8): bz#2161: fix AuthorizedKeysCommand inside a Match block.
* sftp(1): bz#2129: symlinking a file would incorrectly canonicalise
the target path.
* ssh-agent(1): bz#2175: fix a use-after-free in the PKCS#11 agent
helper executable.
* sshd(8): Improve logging of sessions to include the user name,
remote host and port, the session type (shell, command, etc.) and
allocated TTY (if any).
* sshd(8): bz#1297: tell the client (via a debug message) when
their preferred listen address has been overridden by the
server's GatewayPorts setting.
* sshd(8): bz#2162: include report port in bad protocol banner
message.
* sftp(1): bz#2163: fix memory leak in error path in do_readdir().
* sftp(1): bz#2171: don't leak file descriptor on error.
* sshd(8): Include the local address and port in "Connection from
..." message (only shown at loglevel>=verbose).
Portable OpenSSH:
* Please note that this is the last version of Portable OpenSSH that
will support versions of OpenSSL prior to 0.9.6. Support (i.e.
SSH_OLD_EVP) will be removed following the 6.5p1 release.
* Portable OpenSSH will attempt compile and link as a Position
Independent Executable on Linux, OS X and OpenBSD on recent gcc-
like compilers. Other platforms and older/other compilers may
request this using the --with-pie configure flag.
* A number of other toolchain-related hardening options are used
automatically if available, including -ftrapv to abort on signed
integer overflow and options to write-protect dynamic linking
information. The use of these options may be disabled using the
--without-hardening configure flag.
* If the toolchain supports it, one of the -fstack-protector-strong,
-fstack-protector-all or -fstack-protector compilation flag are
used to add guards to mitigate attacks based on stack overflows.
The use of these options may be disabled using the
--without-stackprotect configure option.
* sshd(8): Add support for pre-authentication sandboxing using the
Capsicum API introduced in FreeBSD 10.
* Switch to a ChaCha20-based arc4random() PRNG for platforms that do
not provide their own.
* sshd(8): bz#2156: restore Linux oom_adj setting when handling
SIGHUP to maintain behaviour over retart.
* sshd(8): bz#2032: use local username in krb5_kuserok check rather
than full client name which may be of form user@REALM.
* ssh(1), sshd(8): Test for both the presence of ECC NID numbers in
OpenSSL and that they actually work. Fedora (at least) has
NID_secp521r1 that doesn't work.
* bz#2173: use pkg-config --libs to include correct -L location for
libedit.
Changes since OpenSSH 6.3
=========================
This release fixes a security bug:
* sshd(8): fix a memory corruption problem triggered during rekeying
when an AES-GCM cipher is selected. Full details of the vulnerability
are available at: http://www.openssh.com/txt/gcmrekey.adv
Checksums:
==========
- SHA1 (openssh-6.4.tar.gz) = 4caf1a50eb3a3da821c16298c4aaa576fe24210c
- SHA1 (openssh-6.4p1.tar.gz) = cf5fe0eb118d7e4f9296fbc5d6884965885fc55d
Reporting Bugs:
===============
- Please read http://www.openssh.com/report.html
Security bugs should be reported directly to openssh@openssh.com
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.