Changes since OpenSSH 8.9
=========================
This release is focused on bug fixing.
Potentially-incompatible changes
--------------------------------
This release switches scp(1) from using the legacy scp/rcp protocol
to using the SFTP protocol 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.
In case of incompatibility, the scp(1) client may be instructed to use
the legacy scp/rcp using the -O flag.
New features
------------
* ssh(1), sshd(8): use the hybrid Streamlined NTRU Prime + x25519 key
exchange method by default ("sntrup761x25519-sha512 () openssh com").
The NTRU algorithm is believed to resist attacks enabled by future
quantum computers and is paired with the X25519 ECDH key exchange
(the previous default) as a backstop against any weaknesses in
NTRU Prime that may be discovered in the future. The combination
ensures that the hybrid exchange offers at least as good security
as the status quo.
We are making this change now (i.e. ahead of cryptographically-
relevant quantum computers) to prevent "capture now, decrypt
later" attacks where an adversary who can record and store SSH
session ciphertext would be able to decrypt it once a sufficiently
advanced quantum computer is available.
* sftp-server(8): support the "copy-data" extension to allow server-
side copying of files/data, following the design in
draft-ietf-secsh-filexfer-extensions-00. bz2948
* sftp(1): add a "cp" command to allow the sftp client to perform
server-side file copies.
Bugfixes
--------
* ssh(1), sshd(8): upstream: fix poll(2) spin when a channel's output
fd closes without data in the channel buffer. bz3405 and bz3411
* sshd(8): pack pollfd array in server listen/accept loop. Could
cause the server to hang/spin when MaxStartups > RLIMIT_NOFILE
* ssh-keygen(1): avoid NULL deref via the find-principals and
check-novalidate operations. bz3409 and GHPR#307 respectively.
* scp(1): fix a memory leak in argument processing. bz3404
* sshd(8): don't try to resolve ListenAddress directives in the sshd
re-exec path. They are unused after re-exec and parsing errors
(possible for example if the host's network configuration changed)
could prevent connections from being accepted.
* sshd(8): when refusing a public key authentication request from a
client for using an unapproved or unsupported signature algorithm
include the algorithm name in the log message to make debugging
easier.
Portability
-----------
* sshd(8): refactor platform-specific locked account check, fixing
an incorrect free() on platforms with both libiaf and shadow
passwords (probably only Unixware) GHPR#284,
* ssh(1), sshd(8): Fix possible integer underflow in scan_scaled(3)
parsing of K/M/G/etc quantities. bz#3401.
* sshd(8): provide killpg implementation (mostly for Tandem NonStop)
GHPR#301.
* Check for missing ftruncate prototype. GHPR#301
* sshd(8): default to not using sandbox when cross compiling. On most
systems poll(2) does not work when the number of FDs is reduced
with setrlimit, so assume it doesn't when cross compiling and we
can't run the test. bz#3398.
* sshd(8): allow ppoll_time64 in seccomp sandbox. Should fix sandbox
violations on some (at least i386 and armhf) 32bit Linux platforms.
bz#3396.
* Improve detection of -fzero-call-used-regs=all support in
configure script.
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.
All checksums have been double-checked against existing RMD160 and
SHA512 hashes
Unfetchable distfiles (fetched conditionally?):
./security/cyrus-sasl/distinfo cyrus-sasl-dedad73e5e7a75d01a5f3d5a6702ab8ccd2ff40d.patch.v2
Changelog:
Future deprecation notice
=========================
It is now possible[1] to perform chosen-prefix attacks against the
SHA-1 algorithm for less than USD$50K. For this reason, we will be
disabling the "ssh-rsa" public key signature algorithm 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.
We intend to enable UpdateHostKeys by default in the next OpenSSH
release. This will assist the client by automatically migrating 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-agent(1): restrict ssh-agent from signing web challenges for
FIDO/U2F keys.
When signing messages in ssh-agent using a FIDO key that has an
application string that does not start with "ssh:", ensure that the
message being signed is one of the forms expected for the SSH protocol
(currently public key authentication and sshsig signatures).
This prevents ssh-agent forwarding on a host that has FIDO keys
attached granting the ability for the remote side to sign challenges
for web authentication using those keys too.
Note that the converse case of web browsers signing SSH challenges is
already precluded because no web RP can have the "ssh:" prefix in the
application string that we require.
* ssh-keygen(1): Enable FIDO 2.1 credProtect extension when generating
a FIDO resident key.
The recent FIDO 2.1 Client to Authenticator Protocol introduced a
"credProtect" feature to better protect resident keys. We use this
option to require a PIN prior to all operations that may retrieve
a resident key from a FIDO token.
Potentially-incompatible changes
================================
This release includes a number of changes that may affect existing
configurations:
* For FIDO/U2F support, OpenSSH recommends the use of libfido2 1.5.0
or greater. Older libraries have limited support at the expense of
disabling particular features. These include resident keys, PIN-
required keys and multiple attached tokens.
* ssh-keygen(1): the format of the attestation information optionally
recorded when a FIDO key is generated has changed. It now includes
the authenticator data needed to validate attestation signatures.
* The API between OpenSSH and the FIDO token middleware has changed
and the SSH_SK_VERSION_MAJOR version has been incremented as a
result. Third-party middleware libraries must support the current
API version (7) to work with OpenSSH 8.4.
* The portable OpenSSH distribution now requires automake to rebuild
the configure script and supporting files. This is not required when
simply building portable OpenSSH from a release tar file.
Changes since OpenSSH 8.3
=========================
New features
------------
* ssh(1), ssh-keygen(1): support for FIDO keys that require a PIN for
each use. These keys may be generated using ssh-keygen using a new
"verify-required" option. When a PIN-required key is used, the user
will be prompted for a PIN to complete the signature operation.
* sshd(8): authorized_keys now supports a new "verify-required"
option to require FIDO signatures assert that the token verified
that the user was present before making the signature. The FIDO
protocol supports multiple methods for user-verification, but
currently OpenSSH only supports PIN verification.
* sshd(8), ssh-keygen(1): add support for verifying FIDO webauthn
signatures. Webauthn is a standard for using FIDO keys in web
browsers. These signatures are a slightly different format to plain
FIDO signatures and thus require explicit support.
* ssh(1): allow some keywords to expand shell-style ${ENV}
environment variables. The supported keywords are CertificateFile,
ControlPath, IdentityAgent and IdentityFile, plus LocalForward and
RemoteForward when used for Unix domain socket paths. bz#3140
* ssh(1), ssh-agent(1): allow some additional control over the use of
ssh-askpass via a new $SSH_ASKPASS_REQUIRE environment variable,
including forcibly enabling and disabling its use. bz#69
* ssh(1): allow ssh_config(5)'s AddKeysToAgent keyword accept a time
limit for keys in addition to its current flag options. Time-
limited keys will automatically be removed from ssh-agent after
their expiry time has passed.
* scp(1), sftp(1): allow the -A flag to explicitly enable agent
forwarding in scp and sftp. The default remains to not forward an
agent, even when ssh_config enables it.
* ssh(1): add a '%k' TOKEN that expands to the effective HostKey of
the destination. This allows, e.g., keeping host keys in individual
files using "UserKnownHostsFile ~/.ssh/known_hosts.d/%k". bz#1654
* ssh(1): add %-TOKEN, environment variable and tilde expansion to
the UserKnownHostsFile directive, allowing the path to be
completed by the configuration (e.g. bz#1654)
* ssh-keygen(1): allow "ssh-add -d -" to read keys to be deleted
from stdin. bz#3180
* sshd(8): improve logging for MaxStartups connection throttling.
sshd will now log when it starts and stops throttling and periodically
while in this state. bz#3055
Bugfixes
--------
* ssh(1), ssh-keygen(1): better support for multiple attached FIDO
tokens. In cases where OpenSSH cannot unambiguously determine which
token to direct a request to, the user is now required to select a
token by touching it. In cases of operations that require a PIN to
be verified, this avoids sending the wrong PIN to the wrong token
and incrementing the token's PIN failure counter (tokens
effectively erase their keys after too many PIN failures).
* sshd(8): fix Include before Match in sshd_config; bz#3122
* ssh(1): close stdin/out/error when forking after authentication
completes ("ssh -f ...") bz#3137
* ssh(1), sshd(8): limit the amount of channel input data buffered,
avoiding peers that advertise large windows but are slow to read
from causing high memory consumption.
* ssh-agent(1): handle multiple requests sent in a single write() to
the agent.
* sshd(8): allow sshd_config longer than 256k
* sshd(8): avoid spurious "Unable to load host key" message when sshd
load a private key but no public counterpart
* ssh(1): prefer the default hostkey algorithm list whenever we have
a hostkey that matches its best-preference algorithm.
* sshd(1): when ordering the hostkey algorithms to request from a
server, prefer certificate types if the known_hosts files contain a key
marked as a @cert-authority; bz#3157
* ssh(1): perform host key fingerprint comparisons for the "Are you
sure you want to continue connecting (yes/no/[fingerprint])?"
prompt with case sensitivity.
* sshd(8): ensure that address/masklen mismatches in sshd_config
yield fatal errors at daemon start time rather than later when
they are evaluated.
* ssh-keygen(1): ensure that certificate extensions are lexically
sorted. Previously if the user specified a custom extension then
the everything would be in order except the custom ones. bz#3198
* ssh(1): also compare username when checking for JumpHost loops.
bz#3057
* ssh-keygen(1): preserve group/world read permission on known_hosts
files across runs of "ssh-keygen -Rf /path". The old behaviour was
to remove all rights for group/other. bz#3146
* ssh-keygen(1): Mention the [-a rounds] flag in the ssh-keygen
manual page and usage().
* sshd(8): explicitly construct path to ~/.ssh/rc rather than
relying on it being relative to the current directory, so that it
can still be found if the shell startup changes its directory.
bz#3185
* sshd(8): when redirecting sshd's log output to a file, undo this
redirection after the session child process is forked(). Fixes
missing log messages when using this feature under some
circumstances.
* sshd(8): start ClientAliveInterval bookkeeping before first pass
through select() loop; fixed theoretical case where busy sshd may
ignore timeouts from client.
* ssh(1): only reset the ServerAliveInterval check when we receive
traffic from the server and ignore traffic from a port forwarding
client, preventing a client from keeping a connection alive when
it should be terminated. bz#2265
* ssh-keygen(1): avoid spurious error message when ssh-keygen
creates files outside ~/.ssh
* sftp-client(1): fix off-by-one error that caused sftp downloads to
make one more concurrent request that desired. This prevented using
sftp(1) in unpipelined request/response mode, which is useful when
debugging. bz#3054
* ssh(1), sshd(8): handle EINTR in waitfd() and timeout_connect()
helpers. bz#3071
* ssh(1), ssh-keygen(1): defer creation of ~/.ssh until we attempt to
write to it so we don't leave an empty .ssh directory when it's not
needed. bz#3156
* ssh(1), sshd(8): fix multiplier when parsing time specifications
when handling seconds after other units. bz#3171
Portability
-----------
* sshd(8): always send any PAM account messages. If the PAM account
stack returns any messages, always send them to the user and not
just if the check succeeds. bz#2049
* Implement some backwards compatibility for libfido2 libraries
older than 1.5.0. Note that use of an older library will result
in the loss of certain features including resident key support,
PIN support and support for multiple attached tokens.
* configure fixes for XCode 12
* gnome-ssh-askpass3: ensure the "close" button is not focused by
default for SSH_ASKPASS_PROMPT=none prompts. Avoids space/enter
accidentally dismissing FIDO touch notifications.
* gnome-ssh-askpass3: allow some control over textarea colour via
$GNOME_SSH_ASKPASS_FG_COLOR and $GNOME_SSH_ASKPASS_BG_COLOR
environment variables.
* sshd(8): document another PAM spec problem in a frustrated comment
* sshd(8): support NetBSD's utmpx.ut_ss address field. bz#960
* Add the ssh-sk-helper binary and its manpage to the RPM spec file
* Detect the Frankenstein monster of Linux/X32 and allow the sandbox
to function there. bz#3085
This enables built-in U2F/FIDO security key support, without any
SSH_SK_PROVIDER middleware library needed. Works only on platforms
with working libfido2, so not enabled by default yet. We should
enable it by default in NetBSD>=10 and maybe some other platforms.
OpenSSH 8.3 was released on 2020-05-27. 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 algorithm for less than USD$50K. For this reason, we will be
disabling the "ssh-rsa" public key signature algorithm 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. Vendors of devices
that implement the SSH protocol should ensure that they support the
new signature algorithms for RSA keys.
[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
========
* scp(1): when receiving files, scp(1) could be become desynchronised
if a utimes(2) system call failed. This could allow file contents
to be interpreted as file metadata and thereby permit an adversary
to craft a file system that, when copied with scp(1) in a
configuration that caused utimes(2) to fail (e.g. under a SELinux
policy or syscall sandbox), transferred different file names and
contents to the actual file system layout.
Exploitation of this is not likely as utimes(2) does not fail under
normal circumstances. Successful exploitation is not silent - the
output of scp(1) would show transfer errors followed by the actual
file(s) that were received.
Finally, filenames returned from the peer are (since openssh-8.0)
matched against the user's requested destination, thereby
disallowing a successful exploit from writing files outside the
user's selected target glob (or directory, in the case of a
recursive transfer). This ensures that this attack can achieve no
more than a hostile peer is already able to achieve within the scp
protocol.
Potentially-incompatible changes
================================
This release includes a number of changes that may affect existing
configurations:
* sftp(1): reject an argument of "-1" in the same way as ssh(1) and
scp(1) do instead of accepting and silently ignoring it.
Changes since OpenSSH 8.2
=========================
The focus of this release is bug fixing.
New Features
------------
* sshd(8): make IgnoreRhosts a tri-state option: "yes" to ignore
rhosts/shosts, "no" allow rhosts/shosts or (new) "shosts-only"
to allow .shosts files but not .rhosts.
* sshd(8): allow the IgnoreRhosts directive to appear anywhere in a
sshd_config, not just before any Match blocks; bz3148
* ssh(1): add %TOKEN percent expansion for the LocalFoward and
RemoteForward keywords when used for Unix domain socket forwarding.
bz#3014
* all: allow loading public keys from the unencrypted envelope of a
private key file if no corresponding public key file is present.
* ssh(1), sshd(8): prefer to use chacha20 from libcrypto where
possible instead of the (slower) portable C implementation included
in OpenSSH.
* ssh-keygen(1): add ability to dump the contents of a binary key
revocation list via "ssh-keygen -lQf /path" bz#3132
Bugfixes
--------
* ssh(1): fix IdentitiesOnly=yes to also apply to keys loaded from
a PKCS11Provider; bz#3141
* ssh-keygen(1): avoid NULL dereference when trying to convert an
invalid RFC4716 private key.
* scp(1): when performing remote-to-remote copies using "scp -3",
start the second ssh(1) channel with BatchMode=yes enabled to
avoid confusing and non-deterministic ordering of prompts.
* ssh(1), ssh-keygen(1): when signing a challenge using a FIDO token,
perform hashing of the message to be signed in the middleware layer
rather than in OpenSSH code. This permits the use of security key
middlewares that perform the hashing implicitly, such as Windows
Hello.
* ssh(1): fix incorrect error message for "too many known hosts
files." bz#3149
* ssh(1): make failures when establishing "Tunnel" forwarding
terminate the connection when ExitOnForwardFailure is enabled;
bz#3116
* ssh-keygen(1): fix printing of fingerprints on private keys and add
a regression test for same.
* sshd(8): document order of checking AuthorizedKeysFile (first) and
AuthorizedKeysCommand (subsequently, if the file doesn't match);
bz#3134
* sshd(8): document that /etc/hosts.equiv and /etc/shosts.equiv are
not considered for HostbasedAuthentication when the target user is
root; bz#3148
* ssh(1), ssh-keygen(1): fix NULL dereference in private certificate
key parsing (oss-fuzz #20074).
* ssh(1), sshd(8): more consistency between sets of %TOKENS are
accepted in various configuration options.
* ssh(1), ssh-keygen(1): improve error messages for some common
PKCS#11 C_Login failure cases; bz#3130
* ssh(1), sshd(8): make error messages for problems during SSH banner
exchange consistent with other SSH transport-layer error messages
and ensure they include the relevant IP addresses bz#3129
* various: fix a number of spelling errors in comments and debug/error
messages
* ssh-keygen(1), ssh-add(1): when downloading FIDO2 resident keys
from a token, don't prompt for a PIN until the token has told us
that it needs one. Avoids double-prompting on devices that
implement on-device authentication.
* sshd(8), ssh-keygen(1): no-touch-required FIDO certificate option
should be an extension, not a critical option.
* ssh(1), ssh-keygen(1), ssh-add(1): offer a better error message
when trying to use a FIDO key function and SecurityKeyProvider is
empty.
* ssh-add(1), ssh-agent(8): ensure that a key lifetime fits within
the values allowed by the wire format (u32). Prevents integer
wraparound of the timeout values. bz#3119
* ssh(1): detect and prevent trivial configuration loops when using
ProxyJump. bz#3057.
Portability
-----------
* Detect systems where signals flagged with SA_RESTART will interrupt
select(2). POSIX permits implementations to choose whether
select(2) will return when interrupted with a SA_RESTART-flagged
signal, but OpenSSH requires interrupting behaviour.
* Several compilation fixes for HP/UX and AIX.
* On platforms that do not support setting process-wide routing
domains (all excepting OpenBSD at present), fail to accept a
configuration attempts to set one at process start time rather than
fatally erroring at run time. bz#3126
* Improve detection of egrep (used in regression tests) on platforms
that offer a poor default one (e.g. Solaris).
* A number of shell portability fixes for the regression tests.
* Fix theoretical infinite loop in the glob(3) replacement
implementation.
* Fix seccomp sandbox compilation problems for some Linux
configurations bz#3085
* Improved detection of libfido2 and some compilation fixes for some
configurations when --with-security-key-builtin is selected.
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
Portability
-----------
* sshd(8): multiple adjustments to the Linux seccomp sandbox:
- Non-fatally deny IPC syscalls in sandbox
- Allow clock_gettime64() in sandbox (MIPS / glibc >= 2.31)
- Allow clock_nanosleep_time64 in sandbox (ARM) bz3100
- Allow clock_nanosleep() in sandbox (recent glibc) bz3093
* Explicit check for memmem declaration and fix up declaration if the
system headers lack it. bz3102
OpenSSH 8.1 was released on 2019-10-09. 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:
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 ...").
Changes since OpenSSH 8.0
=========================
This release is focused on bug-fixing.
New Features
------------
* ssh(1): Allow %n to be expanded in ProxyCommand strings
* ssh(1), sshd(8): Allow prepending a list of algorithms to the
default set by starting the list with the '^' character, E.g.
"HostKeyAlgorithms ^ssh-ed25519"
* ssh-keygen(1): add an experimental lightweight signature and
verification ability. Signatures may be made using regular ssh keys
held on disk or stored in a ssh-agent and verified against an
authorized_keys-like list of allowed keys. Signatures embed a
namespace that prevents confusion and attacks between different
usage domains (e.g. files vs email).
* ssh-keygen(1): print key comment when extracting public key from a
private key. bz#3052
* ssh-keygen(1): accept the verbose flag when searching for host keys
in known hosts (i.e. "ssh-keygen -vF host") to print the matching
host's random-art signature too. bz#3003
* All: support PKCS8 as an optional format for storage of private
keys to disk. The OpenSSH native key format remains the default,
but PKCS8 is a superior format to PEM if interoperability with
non-OpenSSH software is required, as it may use a less insecure
key derivation function than PEM's.
Bugfixes
--------
* ssh(1): if a PKCS#11 token returns no keys then try to login and
refetch them. Based on patch from Jakub Jelen; bz#2430
* ssh(1): produce a useful error message if the user's shell is set
incorrectly during "match exec" processing. bz#2791
* sftp(1): allow the maximum uint32 value for the argument passed
to -b which allows better error messages from later validation.
bz#3050
* ssh(1): avoid pledge sandbox violations in some combinations of
remote forwarding, connection multiplexing and ControlMaster.
* ssh-keyscan(1): include SHA2-variant RSA key algorithms in KEX
proposal; allows ssh-keyscan to harvest keys from servers that
disable old SHA1 ssh-rsa. bz#3029
* sftp(1): print explicit "not modified" message if a file was
requested for resumed download but was considered already complete.
bz#2978
* sftp(1): fix a typo and make <esc><right> move right to the
closest end of a word just like <esc><left> moves left to the
closest beginning of a word.
* sshd(8): cap the number of permitopen/permitlisten directives
allowed to appear on a single authorized_keys line.
* All: fix a number of memory leaks (one-off or on exit paths).
* Regression tests: a number of fixes and improvements, including
fixes to the interop tests, adding the ability to run most tests
on builds that disable OpenSSL support, better support for running
tests under Valgrind and a number of bug-fixes.
* ssh(1), sshd(8): check for convtime() refusing to accept times that
resolve to LONG_MAX Reported by Kirk Wolf bz2977
* ssh(1): slightly more instructive error message when the user
specifies multiple -J options on the command-line. bz3015
* ssh-agent(1): process agent requests for RSA certificate private
keys using correct signature algorithm when requested. bz3016
* sftp(1): check for user@host when parsing sftp target. This
allows user@[1.2.3.4] to work without a path. bz#2999
* sshd(8): enlarge format buffer size for certificate serial
number so the log message can record any 64-bit integer without
truncation. bz#3012
* sshd(8): for PermitOpen violations add the remote host and port to
be able to more easily ascertain the source of the request. Add the
same logging for PermitListen violations which where not previously
logged at all.
* scp(1), sftp(1): use the correct POSIX format style for left
justification for the transfer progress meter. bz#3002
* sshd(8) when examining a configuration using sshd -T, assume any
attribute not provided by -C does not match, which allows it to work
when sshd_config contains a Match directive with or without -C.
bz#2858
* ssh(1), ssh-keygen(1): downgrade PKCS#11 "provider returned no
slots" warning from log level error to debug. This is common when
attempting to enumerate keys on smartcard readers with no cards
plugged in. bz#3058
* ssh(1), ssh-keygen(1): do not unconditionally log in to PKCS#11
tokens. Avoids spurious PIN prompts for keys not selected for
authentication in ssh(1) and when listing public keys available in
a token using ssh-keygen(1). bz#3006
Portability
-----------
* ssh(1): fix SIGWINCH delivery of Solaris for multiplexed sessions
bz#3030
* ssh(1), sshd(8): fix typo that prevented detection of Linux VRF
* sshd(8): add no-op implementation of pam_putenv to avoid build
breakage on platforms where the PAM implementation lacks this
function (e.g. HP-UX). bz#3008
* sftp-server(8): fix Solaris privilege sandbox from preventing
the legacy sftp rename operation from working (was refusing to
allow hard links to files owned by other users). bz#3036
* All: add a proc_pidinfo()-based closefrom() for OS X to avoid
the need to brute-force close all high-numbered file descriptors.
bz#3049
* sshd(8): in the Linux seccomp-bpf sandbox, allow mprotect(2) with
PROT_(READ|WRITE|NONE) only. This syscall is used by some hardened
heap allocators. Github PR#142
* sshd(8): in the Linux seccomp-bpf sandbox, allow the s390-specific
ioctl for ECC hardware support.
* All: use "doc" man page format if the mandoc(1) tool is present on
the system. Previously configure would not select the "doc" man
page format if mandoc was present but nroff was not.
* sshd(8): don't install duplicate STREAMS modules on Solaris; check
if STREAMS modules are already installed on a pty before installing
since when compiling with XPG>=4 they will likely be installed
already. Prevents hangs and duplicate lines on the terminal.
bz#2945 and bz#2998,
pkglint -r --network --only "migrate"
As a side-effect of migrating the homepages, pkglint also fixed a few
indentations in unrelated lines. These and the new homepages have been
checked manually.
Update provided by Aleksej Lebedev in pkgsrc-wip.
I removed Interix support. We've been moving the patches for a
while, without a real test on Interix. the support for interix
is quite invasive and makes updating this package difficult.
Will reconsider re-adding if I knew we had actual users on
Interix (I strongly suspect we don't).
OpenSSH 8.0 was released on 2019-04-17. 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:
http://www.openssh.com/donations.html
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
Add new package option "editline" (enabled by default) which adds
command line editing and filename completion to the "sftp" client.
Bump the package revision because of this change.
Potentially-incompatible changes
================================
* ssh(1), sshd(8): the setting of the new CASignatureAlgorithms
option (see below) bans the use of DSA keys as certificate
authorities.
* sshd(8): the authentication success/failure log message has
changed format slightly. It now includes the certificate
fingerprint (previously it included only key ID and CA key
fingerprint).
New Features
------------
* ssh(1), sshd(8): allow most port numbers to be specified using
service names from getservbyname(3) (typically /etc/services).
* ssh(1): allow the IdentityAgent configuration directive to accept
environment variable names. This supports the use of multiple
agent sockets without needing to use fixed paths.
* sshd(8): support signalling sessions via the SSH protocol.
A limited subset of signals is supported and only for login or
command sessions (i.e. not subsystems) that were not subject to
a forced command via authorized_keys or sshd_config. bz#1424
* ssh(1): support "ssh -Q sig" to list supported signature options.
Also "ssh -Q help" to show the full set of supported queries.
* ssh(1), sshd(8): add a CASignatureAlgorithms option for the
client and server configs to allow control over which signature
formats are allowed for CAs to sign certificates. For example,
this allows banning CAs that sign certificates using the RSA-SHA1
signature algorithm.
* sshd(8), ssh-keygen(1): allow key revocation lists (KRLs) to
revoke keys specified by SHA256 hash.
* ssh-keygen(1): allow creation of key revocation lists directly
from base64-encoded SHA256 fingerprints. This supports revoking
keys using only the information contained in sshd(8)
authentication log messages.
Bugfixes
--------
* ssh(1), ssh-keygen(1): avoid spurious "invalid format" errors when
attempting to load PEM private keys while using an incorrect
passphrase. bz#2901
* sshd(8): when a channel closed message is received from a client,
close the stderr file descriptor at the same time stdout is
closed. This avoids stuck processes if they were waiting for
stderr to close and were insensitive to stdin/out closing. bz#2863
* ssh(1): allow ForwardX11Timeout=0 to disable the untrusted X11
forwarding timeout and support X11 forwarding indefinitely.
Previously the behaviour of ForwardX11Timeout=0 was undefined.
* sshd(8): when compiled with GSSAPI support, cache supported method
OIDs regardless of whether GSSAPI authentication is enabled in the
main section of sshd_config. This avoids sandbox violations if
GSSAPI authentication was later enabled in a Match block. bz#2107
* sshd(8): do not fail closed when configured with a text key
revocation list that contains a too-short key. bz#2897
* ssh(1): treat connections with ProxyJump specified the same as
ones with a ProxyCommand set with regards to hostname
canonicalisation (i.e. don't try to canonicalise the hostname
unless CanonicalizeHostname is set to 'always'). bz#2896
* ssh(1): fix regression in OpenSSH 7.8 that could prevent public-
key authentication using certificates hosted in a ssh-agent(1)
or against sshd(8) from OpenSSH <7.8.
Portability
-----------
* All: support building against the openssl-1.1 API (releases 1.1.0g
and later). The openssl-1.0 API will remain supported at least
until OpenSSL terminates security patch support for that API version.
* sshd(8): allow the futex(2) syscall in the Linux seccomp sandbox;
apparently required by some glibc/OpenSSL combinations.
* sshd(8): handle getgrouplist(3) returning more than
_SC_NGROUPS_MAX groups. Some platforms consider this limit more
as a guideline.
OpenSSH 7.8:
Potentially-incompatible changes
================================
* ssh-keygen(1): write OpenSSH format private keys by default
instead of using OpenSSL's PEM format. The OpenSSH format,
supported in OpenSSH releases since 2014 and described in the
PROTOCOL.key file in the source distribution, offers substantially
better protection against offline password guessing and supports
key comments in private keys. If necessary, it is possible to write
old PEM-style keys by adding "-m PEM" to ssh-keygen's arguments
when generating or updating a key.
* sshd(8): remove internal support for S/Key multiple factor
authentication. S/Key may still be used via PAM or BSD auth.
* ssh(1): remove vestigal support for running ssh(1) as setuid. This
used to be required for hostbased authentication and the (long
gone) rhosts-style authentication, but has not been necessary for
a long time. Attempting to execute ssh as a setuid binary, or with
uid != effective uid will now yield a fatal error at runtime.
* sshd(8): the semantics of PubkeyAcceptedKeyTypes and the similar
HostbasedAcceptedKeyTypes options have changed. These now specify
signature algorithms that are accepted for their respective
authentication mechanism, where previously they specified accepted
key types. This distinction matters when using the RSA/SHA2
signature algorithms "rsa-sha2-256", "rsa-sha2-512" and their
certificate counterparts. Configurations that override these
options but omit these algorithm names may cause unexpected
authentication failures (no action is required for configurations
that accept the default for these options).
* sshd(8): the precedence of session environment variables has
changed. ~/.ssh/environment and environment="..." options in
authorized_keys files can no longer override SSH_* variables set
implicitly by sshd.
* ssh(1)/sshd(8): the default IPQoS used by ssh/sshd has changed.
They will now use DSCP AF21 for interactive traffic and CS1 for
bulk. For a detailed rationale, please see the commit message:
https://cvsweb.openbsd.org/src/usr.bin/ssh/readconf.c#rev1.284
New Features
------------
* ssh(1)/sshd(8): add new signature algorithms "rsa-sha2-256-cert-
v01@openssh.com" and "rsa-sha2-512-cert-v01@openssh.com" to
explicitly force use of RSA/SHA2 signatures in authentication.
* sshd(8): extend the PermitUserEnvironment option to accept a
whitelist of environment variable names in addition to global
"yes" or "no" settings.
* sshd(8): add a PermitListen directive to sshd_config(5) and a
corresponding permitlisten= authorized_keys option that control
which listen addresses and port numbers may be used by remote
forwarding (ssh -R ...).
* sshd(8): add some countermeasures against timing attacks used for
account validation/enumeration. sshd will enforce a minimum time
or each failed authentication attempt consisting of a global 5ms
minimum plus an additional per-user 0-4ms delay derived from a
host secret.
* sshd(8): add a SetEnv directive to allow an administrator to
explicitly specify environment variables in sshd_config.
Variables set by SetEnv override the default and client-specified
environment.
* ssh(1): add a SetEnv directive to request that the server sets
an environment variable in the session. Similar to the existing
SendEnv option, these variables are set subject to server
configuration.
* ssh(1): allow "SendEnv -PATTERN" to clear environment variables
previously marked for sending to the server. bz#1285
* ssh(1)/sshd(8): make UID available as a %-expansion everywhere
that the username is available currently. bz#2870
* ssh(1): allow setting ProxyJump=none to disable ProxyJump
functionality. bz#2869
Bugfixes
--------
* sshd(8): avoid observable differences in request parsing that could
be used to determine whether a target user is valid.
* all: substantial internal refactoring
* ssh(1)/sshd(8): fix some memory leaks; bz#2366
* ssh(1): fix a pwent clobber (introduced in openssh-7.7) that could
occur during key loading, manifesting as crash on some platforms.
* sshd_config(5): clarify documentation for AuthenticationMethods
option; bz#2663
* ssh(1): ensure that the public key algorithm sent in a
public key SSH_MSG_USERAUTH_REQUEST matches the content of the
signature blob. Previously, these could be inconsistent when a
legacy or non-OpenSSH ssh-agent returned a RSA/SHA1 signature
when asked to make a RSA/SHA2 signature.
* sshd(8): fix failures to read authorized_keys caused by faulty
supplemental group caching. bz#2873
* scp(1): apply umask to directories, fixing potential mkdir/chmod
race when copying directory trees bz#2839
* ssh-keygen(1): return correct exit code when searching for and
hashing known_hosts entries in a single operation; bz#2772
* ssh(1): prefer the ssh binary pointed to via argv[0] to $PATH when
re-executing ssh for ProxyJump. bz#2831
* sshd(8): do not ban PTY allocation when a sshd session is
restricted because the user password is expired as it breaks
password change dialog. (regression in openssh-7.7).
* ssh(1)/sshd(8): fix error reporting from select() failures.
* ssh(1): improve documentation for -w (tunnel) flag, emphasising
that -w implicitly sets Tunnel=point-to-point. bz#2365
* ssh-agent(1): implement EMFILE mitigation for ssh-agent. ssh-agent
will no longer spin when its file descriptor limit is exceeded.
bz#2576
* ssh(1)/sshd(8): disable SSH2_MSG_DEBUG messages for Twisted Conch
clients. Twisted Conch versions that lack a version number in
their identification strings will mishandle these messages when
running on Python 2.x (https://twistedmatrix.com/trac/ticket/9422)
* sftp(1): notify user immediately when underlying ssh process dies
expectedly. bz#2719
* ssh(1)/sshd(8): fix tunnel forwarding; regression in 7.7 release.
bz#2855
* ssh-agent(1): don't kill ssh-agent's listening socket entirely if
it fails to accept(2) a connection. bz#2837
* sshd(8): relax checking of authorized_keys environment="..."
options to allow underscores in variable names (regression
introduced in 7.7). bz#2851
* ssh(1): add some missing options in the configuration dump output
(ssh -G). bz#2835
Portability
-----------
* sshd(8): Expose details of completed authentication to PAM auth
modules via SSH_AUTH_INFO_0 in the PAM environment. bz#2408
* Fix compilation problems caused by fights between zlib and OpenSSL
colliding uses of "free_func"
* Improve detection of unsupported compiler options. Recently these
may have manifested as "unsupported -Wl,-z,retpoline" warnings
during linking.
* sshd(8): some sandbox support for Linux/s390 bz#2752.
* regress tests: unbreak key-options.sh test on platforms without
openpty(3). bz#2856
* use getrandom(2) for PRNG seeding when built without OpenSSL.
OpenSSH 7.7:
Potentially-incompatible changes
================================
* ssh(1)/sshd(8): Drop compatibility support for some very old SSH
implementations, including ssh.com <=2.* and OpenSSH <= 3.*. These
versions were all released in or before 2001 and predate the final
SSH RFCs. The support in question isn't necessary for RFC-compliant
SSH implementations.
New Features
------------
* All: Add experimental support for PQC XMSS keys (Extended Hash-
Based Signatures) based on the algorithm described in
https://tools.ietf.org/html/draft-irtf-cfrg-xmss-hash-based-signatures-12
The XMSS signature code is experimental and not compiled in by
default.
* sshd(8): Add a "rdomain" criteria for the sshd_config Match keyword
to allow conditional configuration that depends on which routing
domain a connection was received on (currently supported on OpenBSD
and Linux).
* sshd_config(5): Add an optional rdomain qualifier to the
ListenAddress directive to allow listening on different routing
domains. This is supported only on OpenBSD and Linux at present.
* sshd_config(5): Add RDomain directive to allow the authenticated
session to be placed in an explicit routing domain. This is only
supported on OpenBSD at present.
* sshd(8): Add "expiry-time" option for authorized_keys files to
allow for expiring keys.
* ssh(1): Add a BindInterface option to allow binding the outgoing
connection to an interface's address (basically a more usable
BindAddress)
* ssh(1): Expose device allocated for tun/tap forwarding via a new
%T expansion for LocalCommand. This allows LocalCommand to be used
to prepare the interface.
* sshd(8): Expose the device allocated for tun/tap forwarding via a
new SSH_TUNNEL environment variable. This allows automatic setup of
the interface and surrounding network configuration automatically on
the server.
* ssh(1)/scp(1)/sftp(1): Add URI support to ssh, sftp and scp, e.g.
ssh://user@host or sftp://user@host/path. Additional connection
parameters described in draft-ietf-secsh-scp-sftp-ssh-uri-04 are not
implemented since the ssh fingerprint format in the draft uses the
deprecated MD5 hash with no way to specify the any other algorithm.
* ssh-keygen(1): Allow certificate validity intervals that specify
only a start or stop time (instead of both or neither).
* sftp(1): Allow "cd" and "lcd" commands with no explicit path
argument. lcd will change to the local user's home directory as
usual. cd will change to the starting directory for session (because
the protocol offers no way to obtain the remote user's home
directory). bz#2760
* sshd(8): When doing a config test with sshd -T, only require the
attributes that are actually used in Match criteria rather than (an
incomplete list of) all criteria.
Bugfixes
--------
* ssh(1)/sshd(8): More strictly check signature types during key
exchange against what was negotiated. Prevents downgrade of RSA
signatures made with SHA-256/512 to SHA-1.
* sshd(8): Fix support for client that advertise a protocol version
of "1.99" (indicating that they are prepared to accept both SSHv1 and
SSHv2). This was broken in OpenSSH 7.6 during the removal of SSHv1
support. bz#2810
* ssh(1): Warn when the agent returns a ssh-rsa (SHA1) signature when
a rsa-sha2-256/512 signature was requested. This condition is possible
when an old or non-OpenSSH agent is in use. bz#2799
* ssh-agent(1): Fix regression introduced in 7.6 that caused ssh-agent
to fatally exit if presented an invalid signature request message.
* sshd_config(5): Accept yes/no flag options case-insensitively, as
has been the case in ssh_config(5) for a long time. bz#2664
* ssh(1): Improve error reporting for failures during connection.
Under some circumstances misleading errors were being shown. bz#2814
* ssh-keyscan(1): Add -D option to allow printing of results directly
in SSHFP format. bz#2821
* regress tests: fix PuTTY interop test broken in last release's SSHv1
removal. bz#2823
* ssh(1): Compatibility fix for some servers that erroneously drop the
connection when the IUTF8 (RFC8160) option is sent.
* scp(1): Disable RemoteCommand and RequestTTY in the ssh session
started by scp (sftp was already doing this.)
* ssh-keygen(1): Refuse to create a certificate with an unusable
number of principals.
* ssh-keygen(1): Fatally exit if ssh-keygen is unable to write all the
public key during key generation. Previously it would silently
ignore errors writing the comment and terminating newline.
* ssh(1): Do not modify hostname arguments that are addresses by
automatically forcing them to lower-case. Instead canonicalise them
to resolve ambiguities (e.g. ::0001 => ::1) before they are matched
against known_hosts. bz#2763
* ssh(1): Don't accept junk after "yes" or "no" responses to hostkey
prompts. bz#2803
* sftp(1): Have sftp print a warning about shell cleanliness when
decoding the first packet fails, which is usually caused by shells
polluting stdout of non-interactive startups. bz#2800
* ssh(1)/sshd(8): Switch timers in packet code from using wall-clock
time to monotonic time, allowing the packet layer to better function
over a clock step and avoiding possible integer overflows during
steps.
* Numerous manual page fixes and improvements.
Portability
-----------
* sshd(8): Correctly detect MIPS ABI in use at configure time. Fixes
sandbox violations on some environments.
* sshd(8): Remove UNICOS support. The hardware and software are literal
museum pieces and support in sshd is too intrusive to justify
maintaining.
* All: Build and link with "retpoline" flags when available to mitigate
the "branch target injection" style (variant 2) of the Spectre
branch-prediction vulnerability.
* All: Add auto-generated dependency information to Makefile.
* Numerous fixed to the RPM spec files.
Potentially-incompatible changes
================================
This release includes a number of changes that may affect existing
configurations:
* ssh(1): delete SSH protocol version 1 support, associated
configuration options and documentation.
* ssh(1)/sshd(8): remove support for the hmac-ripemd160 MAC.
* ssh(1)/sshd(8): remove support for the arcfour, blowfish and CAST
ciphers.
* Refuse RSA keys <1024 bits in length and improve reporting for keys
that do not meet this requirement.
* ssh(1): do not offer CBC ciphers by default.
Changes since OpenSSH 7.5
=========================
This is primarily a bugfix release. It also contains substantial
internal refactoring.
Security
--------
* sftp-server(8): in read-only mode, sftp-server was incorrectly
permitting creation of zero-length files. Reported by Michal
Zalewski.
New Features
------------
* ssh(1): add RemoteCommand option to specify a command in the ssh
config file instead of giving it on the client's command line. This
allows the configuration file to specify the command that will be
executed on the remote host.
* sshd(8): add ExposeAuthInfo option that enables writing details of
the authentication methods used (including public keys where
applicable) to a file that is exposed via a $SSH_USER_AUTH
environment variable in the subsequent session.
* ssh(1): add support for reverse dynamic forwarding. In this mode,
ssh will act as a SOCKS4/5 proxy and forward connections
to destinations requested by the remote SOCKS client. This mode
is requested using extended syntax for the -R and RemoteForward
options and, because it is implemented solely at the client,
does not require the server be updated to be supported.
* sshd(8): allow LogLevel directive in sshd_config Match blocks;
bz#2717
* ssh-keygen(1): allow inclusion of arbitrary string or flag
certificate extensions and critical options.
* ssh-keygen(1): allow ssh-keygen to use a key held in ssh-agent as
a CA when signing certificates. bz#2377
* ssh(1)/sshd(8): allow IPQoS=none in ssh/sshd to not set an explicit
ToS/DSCP value and just use the operating system default.
* ssh-add(1): added -q option to make ssh-add quiet on success.
* ssh(1): expand the StrictHostKeyChecking option with two new
settings. The first "accept-new" will automatically accept
hitherto-unseen keys but will refuse connections for changed or
invalid hostkeys. This is a safer subset of the current behaviour
of StrictHostKeyChecking=no. The second setting "off", is a synonym
for the current behaviour of StrictHostKeyChecking=no: accept new
host keys, and continue connection for hosts with incorrect
hostkeys. A future release will change the meaning of
StrictHostKeyChecking=no to the behaviour of "accept-new". bz#2400
* ssh(1): add SyslogFacility option to ssh(1) matching the equivalent
option in sshd(8). bz#2705
Bugfixes
--------
* ssh(1): use HostKeyAlias if specified instead of hostname for
matching host certificate principal names; bz#2728
* sftp(1): implement sorting for globbed ls; bz#2649
* ssh(1): add a user@host prefix to client's "Permission denied"
messages, useful in particular when using "stacked" connections
(e.g. ssh -J) where it's not clear which host is denying. bz#2720
* ssh(1): accept unknown EXT_INFO extension values that contain \0
characters. These are legal, but would previously cause fatal
connection errors if received.
* ssh(1)/sshd(8): repair compression statistics printed at
connection exit
* sftp(1): print '?' instead of incorrect link count (that the
protocol doesn't provide) for remote listings. bz#2710
* ssh(1): return failure rather than fatal() for more cases during
session multiplexing negotiations. Causes the session to fall back
to a non-mux connection if they occur. bz#2707
* ssh(1): mention that the server may send debug messages to explain
public key authentication problems under some circumstances; bz#2709
* Translate OpenSSL error codes to better report incorrect passphrase
errors when loading private keys; bz#2699
* sshd(8): adjust compatibility patterns for WinSCP to correctly
identify versions that implement only the legacy DH group exchange
scheme. bz#2748
* ssh(1): print the "Killed by signal 1" message only at LogLevel
verbose so that it is not shown at the default level; prevents it
from appearing during ssh -J and equivalent ProxyCommand configs.
bz#1906, bz#2744
* ssh-keygen(1): when generating all hostkeys (ssh-keygen -A), clobber
existing keys if they exist but are zero length. zero-length keys
could previously be made if ssh-keygen failed or was interrupted part
way through generating them. bz#2561
* ssh(1): fix pledge(2) violation in the escape sequence "~&" used to
place the current session in the background.
* ssh-keyscan(1): avoid double-close() on file descriptors; bz#2734
* sshd(8): avoid reliance on shared use of pointers shared between
monitor and child sshd processes. bz#2704
* sshd_config(8): document available AuthenticationMethods; bz#2453
* ssh(1): avoid truncation in some login prompts; bz#2768
* sshd(8): Fix various compilations failures, inc bz#2767
* ssh(1): make "--" before the hostname terminate argument processing
after the hostname too.
* ssh-keygen(1): switch from aes256-cbc to aes256-ctr for encrypting
new-style private keys. Fixes problems related to private key
handling for no-OpenSSL builds. bz#2754
* ssh(1): warn and do not attempt to use keys when the public and
private halves do not match. bz#2737
* sftp(1): don't print verbose error message when ssh disconnects
from under sftp. bz#2750
* sshd(8): fix keepalive scheduling problem: activity on a forwarded
port from preventing the keepalive from being sent; bz#2756
* sshd(8): when started without root privileges, don't require the
privilege separation user or path to exist. Makes running the
regression tests easier without touching the filesystem.
* Make integrity.sh regression tests more robust against timeouts.
bz#2658
* ssh(1)/sshd(8): correctness fix for channels implementation: accept
channel IDs greater than 0x7FFFFFFF.
Portability
-----------
* sshd(9): drop two more privileges in the Solaris sandbox:
PRIV_DAX_ACCESS and PRIV_SYS_IB_INFO; bz#2723
* sshd(8): expose list of completed authentication methods to PAM
via the SSH_AUTH_INFO_0 PAM environment variable. bz#2408
* ssh(1)/sshd(8): fix several problems in the tun/tap forwarding code,
mostly to do with host/network byte order confusion. bz#2735
* Add --with-cflags-after and --with-ldflags-after configure flags to
allow setting CFLAGS/LDFLAGS after configure has completed. These
are useful for setting sanitiser/fuzzing options that may interfere
with configure's operation.
* sshd(8): avoid Linux seccomp violations on ppc64le over the
socketcall syscall.
* Fix use of ldns when using ldns-config; bz#2697
* configure: set cache variables when cross-compiling. The cross-
compiling fallback message was saying it assumed the test passed,
but it wasn't actually set the cache variables and this would
cause later tests to fail.
* Add clang libFuzzer harnesses for public key parsing and signature
verification.
Potentially-incompatible changes
================================
This release includes a number of changes that may affect existing
configurations:
* This release deprecates the sshd_config UsePrivilegeSeparation
option, thereby making privilege separation mandatory. Privilege
separation has been on by default for almost 15 years and
sandboxing has been on by default for almost the last five.
* The format of several log messages emitted by the packet code has
changed to include additional information about the user and
their authentication state. Software that monitors ssh/sshd logs
may need to account for these changes. For example:
Connection closed by user x 1.1.1.1 port 1234 [preauth]
Connection closed by authenticating user x 10.1.1.1 port 1234 [preauth]
Connection closed by invalid user x 1.1.1.1 port 1234 [preauth]
Affected messages include connection closure, timeout, remote
disconnection, negotiation failure and some other fatal messages
generated by the packet code.
* [Portable OpenSSH only] This version removes support for building
against OpenSSL versions prior to 1.0.1. OpenSSL stopped supporting
versions prior to 1.0.1 over 12 months ago (i.e. they no longer
receive fixes for security bugs).
Changes since OpenSSH 7.4
=========================
This is a bugfix release.
Security
--------
* ssh(1), sshd(8): Fix weakness in CBC padding oracle countermeasures
that allowed a variant of the attack fixed in OpenSSH 7.3 to proceed.
Note that the OpenSSH client disables CBC ciphers by default, sshd
offers them as lowest-preference options and will remove them by
default entriely in the next release. Reported by Jean Paul
Degabriele, Kenny Paterson, Martin Albrecht and Torben Hansen of
Royal Holloway, University of London.
* sftp-client(1): [portable OpenSSH only] On Cygwin, a client making
a recursive file transfer could be maniuplated by a hostile server to
perform a path-traversal attack. creating or modifying files outside
of the intended target directory. Reported by Jann Horn of Google
Project Zero.
New Features
------------
* ssh(1), sshd(8): Support "=-" syntax to easily remove methods from
algorithm lists, e.g. Ciphers=-*cbc. bz#2671
Bugfixes
--------
* sshd(1): Fix NULL dereference crash when key exchange start
messages are sent out of sequence.
* ssh(1), sshd(8): Allow form-feed characters to appear in
configuration files.
* sshd(8): Fix regression in OpenSSH 7.4 support for the
server-sig-algs extension, where SHA2 RSA signature methods were
not being correctly advertised. bz#2680
* ssh(1), ssh-keygen(1): Fix a number of case-sensitivity bugs in
known_hosts processing. bz#2591 bz#2685
* ssh(1): Allow ssh to use certificates accompanied by a private key
file but no corresponding plain *.pub public key. bz#2617
* ssh(1): When updating hostkeys using the UpdateHostKeys option,
accept RSA keys if HostkeyAlgorithms contains any RSA keytype.
Previously, ssh could ignore RSA keys when only the ssh-rsa-sha2-*
methods were enabled in HostkeyAlgorithms and not the old ssh-rsa
method. bz#2650
* ssh(1): Detect and report excessively long configuration file
lines. bz#2651
* Merge a number of fixes found by Coverity and reported via Redhat
and FreeBSD. Includes fixes for some memory and file descriptor
leaks in error paths. bz#2687
* ssh-keyscan(1): Correctly hash hosts with a port number. bz#2692
* ssh(1), sshd(8): When logging long messages to stderr, don't truncate
"\r\n" if the length of the message exceeds the buffer. bz#2688
* ssh(1): Fully quote [host]:port in generated ProxyJump/-J command-
line; avoid confusion over IPv6 addresses and shells that treat
square bracket characters specially.
* ssh-keygen(1): Fix corruption of known_hosts when running
"ssh-keygen -H" on a known_hosts containing already-hashed entries.
* Fix various fallout and sharp edges caused by removing SSH protocol
1 support from the server, including the server banner string being
incorrectly terminated with only \n (instead of \r\n), confusing
error messages from ssh-keyscan bz#2583 and a segfault in sshd
if protocol v.1 was enabled for the client and sshd_config
contained references to legacy keys bz#2686.
* ssh(1), sshd(8): Free fd_set on connection timeout. bz#2683
* sshd(8): Fix Unix domain socket forwarding for root (regression in
OpenSSH 7.4).
* sftp(1): Fix division by zero crash in "df" output when server
returns zero total filesystem blocks/inodes.
* ssh(1), ssh-add(1), ssh-keygen(1), sshd(8): Translate OpenSSL errors
encountered during key loading to more meaningful error codes.
bz#2522 bz#2523
* ssh-keygen(1): Sanitise escape sequences in key comments sent to
printf but preserve valid UTF-8 when the locale supports it;
bz#2520
* ssh(1), sshd(8): Return reason for port forwarding failures where
feasible rather than always "administratively prohibited". bz#2674
* sshd(8): Fix deadlock when AuthorizedKeysCommand or
AuthorizedPrincipalsCommand produces a lot of output and a key is
matched early. bz#2655
* Regression tests: several reliability fixes. bz#2654 bz#2658 bz#2659
* ssh(1): Fix typo in ~C error message for bad port forward
cancellation. bz#2672
* ssh(1): Show a useful error message when included config files
can't be opened; bz#2653
* sshd(8): Make sshd set GSSAPIStrictAcceptorCheck=yes as the manual page
(previously incorrectly) advertised. bz#2637
* sshd_config(5): Repair accidentally-deleted mention of %k token
in AuthorizedKeysCommand; bz#2656
* sshd(8): Remove vestiges of previously removed LOGIN_PROGRAM; bz#2665
* ssh-agent(1): Relax PKCS#11 whitelist to include libexec and
common 32-bit compatibility library directories.
* sftp-client(1): Fix non-exploitable integer overflow in SSH2_FXP_NAME
response handling.
* ssh-agent(1): Fix regression in 7.4 of deleting PKCS#11-hosted
keys. It was not possible to delete them except by specifying
their full physical path. bz#2682
Portability
-----------
* sshd(8): Avoid sandbox errors for Linux S390 systems using an ICA
crypto coprocessor.
* sshd(8): Fix non-exploitable weakness in seccomp-bpf sandbox arg
inspection.
* ssh(1): Fix X11 forwarding on OSX where X11 was being started by
launchd. bz#2341
* ssh-keygen(1), ssh(1), sftp(1): Fix output truncation for various that
contain non-printable characters where the codeset in use is ASCII.
* build: Fix builds that attempt to link a kerberised libldns. bz#2603
* build: Fix compilation problems caused by unconditionally defining
_XOPEN_SOURCE in wide character detection.
* sshd(8): Fix sandbox violations for clock_gettime VSDO syscall
fallback on some Linux/X32 kernels. bz#2142
For full changes, please refer ChangeLog file.
Future deprecation notice
=========================
We plan on retiring more legacy cryptography in future releases,
specifically:
* In approximately August 2017, removing remaining support for the
SSH v.1 protocol (client-only and currently compile-time disabled).
* In the same release, removing support for Blowfish and RC4 ciphers
and the RIPE-MD160 HMAC. (These are currently run-time disabled).
* Refusing all RSA keys smaller than 1024 bits (the current minimum
is 768 bits)
* The next release of OpenSSH will remove support for running sshd(8)
with privilege separation disabled.
* The next release of portable OpenSSH will remove support for
OpenSSL version prior to 1.0.1.
This list reflects our current intentions, but please check the final
release notes for future releases.
Potentially-incompatible changes
================================
This release includes a number of changes that may affect existing
configurations:
* This release removes server support for the SSH v.1 protocol.
* ssh(1): Remove 3des-cbc from the client's default proposal. 64-bit
block ciphers are not safe in 2016 and we don't want to wait until
attacks like SWEET32 are extended to SSH. As 3des-cbc was the
only mandatory cipher in the SSH RFCs, this may cause problems
connecting to older devices using the default configuration,
but it's highly likely that such devices already need explicit
configuration for key exchange and hostkey algorithms already
anyway.
* sshd(8): Remove support for pre-authentication compression.
Doing compression early in the protocol probably seemed reasonable
in the 1990s, but today it's clearly a bad idea in terms of both
cryptography (cf. multiple compression oracle attacks in TLS) and
attack surface. Pre-auth compression support has been disabled by
default for >10 years. Support remains in the client.
* ssh-agent will refuse to load PKCS#11 modules outside a whitelist
of trusted paths by default. The path whitelist may be specified
at run-time.
* sshd(8): When a forced-command appears in both a certificate and
an authorized keys/principals command= restriction, sshd will now
refuse to accept the certificate unless they are identical.
The previous (documented) behaviour of having the certificate
forced-command override the other could be a bit confusing and
error-prone.
* sshd(8): Remove the UseLogin configuration directive and support
for having /bin/login manage login sessions.
Changes since OpenSSH 7.3
=========================
This is primarily a bugfix release.
Security
--------
* ssh-agent(1): Will now refuse to load PKCS#11 modules from paths
outside a trusted whitelist (run-time configurable). Requests to
load modules could be passed via agent forwarding and an attacker
could attempt to load a hostile PKCS#11 module across the forwarded
agent channel: PKCS#11 modules are shared libraries, so this would
result in code execution on the system running the ssh-agent if the
attacker has control of the forwarded agent-socket (on the host
running the sshd server) and the ability to write to the filesystem
of the host running ssh-agent (usually the host running the ssh
client). Reported by Jann Horn of Project Zero.
* sshd(8): When privilege separation is disabled, forwarded Unix-
domain sockets would be created by sshd(8) with the privileges of
'root' instead of the authenticated user. This release refuses
Unix-domain socket forwarding when privilege separation is disabled
(Privilege separation has been enabled by default for 14 years).
Reported by Jann Horn of Project Zero.
* sshd(8): Avoid theoretical leak of host private key material to
privilege-separated child processes via realloc() when reading
keys. No such leak was observed in practice for normal-sized keys,
nor does a leak to the child processes directly expose key material
to unprivileged users. Reported by Jann Horn of Project Zero.
* sshd(8): The shared memory manager used by pre-authentication
compression support had a bounds checks that could be elided by
some optimising compilers. Additionally, this memory manager was
incorrectly accessible when pre-authentication compression was
disabled. This could potentially allow attacks against the
privileged monitor process from the sandboxed privilege-separation
process (a compromise of the latter would be required first).
This release removes support for pre-authentication compression
from sshd(8). Reported by Guido Vranken using the Stack unstable
optimisation identification tool (http://css.csail.mit.edu/stack/)
* sshd(8): Fix denial-of-service condition where an attacker who
sends multiple KEXINIT messages may consume up to 128MB per
connection. Reported by Shi Lei of Gear Team, Qihoo 360.
* sshd(8): Validate address ranges for AllowUser and DenyUsers
directives at configuration load time and refuse to accept invalid
ones. It was previously possible to specify invalid CIDR address
ranges (e.g. user@127.1.2.3/55) and these would always match,
possibly resulting in granting access where it was not intended.
Reported by Laurence Parry.
OpenSSH 7.3p1 is primarily a bugfix release and here is summary.
Changes since OpenSSH 7.2
=========================
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
Changes since OpenSSH 7.2p1
===========================
This release fixes a security bug:
* sshd(8): sanitise X11 authentication credentials to avoid xauth
command injection when X11Forwarding is enabled.
Full details of the vulnerability are available at:
http://www.openssh.com/txt/x11fwd.adv
if ssh_host_key doesn't exist.
RSA1 support is dead and doesn't exist in the package we generate, hence,
regeneration of the key is executed everytime sshd is started/restarted.
Bump PKGREVISION
Reviewed by wiz@
Changes since OpenSSH 7.0
=========================
This is a bugfix release.
Security
--------
* sshd(8): OpenSSH 7.0 contained a logic error in PermitRootLogin=
prohibit-password/without-password that could, depending on
compile-time configuration, permit password authentication to
root while preventing other forms of authentication. This problem
was reported by Mantas Mikulenas.
Bugfixes
--------
* ssh(1), sshd(8): add compatability workarounds for FuTTY
* ssh(1), sshd(8): refine compatability workarounds for WinSCP
* Fix a number of memory faults (double-free, free of uninitialised
memory, etc) in ssh(1) and ssh-keygen(1). Reported by Mateusz
Kocielski.
privilege separation has been disabled all that time. The logic was changed
such that it was only enabled on Interix, instead of only being disabled on
Interix as originally intended.
While here, pull in patches from MacPorts to enable privsep on Darwin.
Bump PKGREVISION.
pkgsrc change:
* tcp_wrappers support was removed from release 6.7, but add it refering
FreeBSD's ports.
* hpn-patch is also based on FreeBSD's ports.
Security
--------
* ssh(1): when forwarding X11 connections with ForwardX11Trusted=no,
connections made after ForwardX11Timeout expired could be permitted
and no longer subject to XSECURITY restrictions because of an
ineffective timeout check in ssh(1) coupled with "fail open"
behaviour in the X11 server when clients attempted connections with
expired credentials. This problem was reported by Jann Horn.
* ssh-agent(1): fix weakness of agent locking (ssh-add -x) to
password guessing by implementing an increasing failure delay,
storing a salted hash of the password rather than the password
itself and using a timing-safe comparison function for verifying
unlock attempts. This problem was reported by Ryan Castellucci.
For more information, please refer release announce.
http://www.openssh.com/txt/release-6.9http://www.openssh.com/txt/release-6.8http://www.openssh.com/txt/release-6.7
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