This release is focused on bug fixing.
Security
========
This release contains fixes for three minor memory safety problems.
None are believed to be exploitable, but we report most memory safety
problems as potential security vulnerabilities out of caution.
* ssh-keyscan(1): fix a one-byte overflow in SSH- banner processing.
Reported by Qualys
* ssh-keygen(1): double free() in error path of file hashing step in
signing/verify code; GHPR333
* ssh-keysign(8): double-free in error path introduced in openssh-8.9
Potentially-incompatible changes
--------------------------------
* The portable OpenSSH project now signs commits and release tags
using git's recent SSH signature support. The list of developer
signing keys is included in the repository as .git_allowed_signers
and is cross-signed using the PGP key that is still used to sign
release artifacts:
https://cdn.openbsd.org/pub/OpenBSD/OpenSSH/RELEASE_KEY.asc
* ssh(1), sshd(8): SetEnv directives in ssh_config and sshd_config
are now first-match-wins to match other directives. Previously
if an environment variable was multiply specified the last set
value would have been used. bz3438
* ssh-keygen(8): ssh-keygen -A (generate all default host key types)
will no longer generate DSA keys, as these are insecure and have
not been used by default for some years.
New features
------------
* ssh(1), sshd(8): add a RequiredRSASize directive to set a minimum
RSA key length. Keys below this length will be ignored for user
authentication and for host authentication in sshd(8).
ssh(1) will terminate a connection if the server offers an RSA key
that falls below this limit, as the SSH protocol does not include
the ability to retry a failed key exchange.
* sftp-server(8): add a "users-groups-by-id@openssh.com" extension
request that allows the client to obtain user/group names that
correspond to a set of uids/gids.
* sftp(1): use "users-groups-by-id@openssh.com" sftp-server
extension (when available) to fill in user/group names for
directory listings.
* sftp-server(8): support the "home-directory" extension request
defined in draft-ietf-secsh-filexfer-extensions-00. This overlaps
a bit with the existing "expand-path@openssh.com", but some other
clients support it.
* ssh-keygen(1), sshd(8): allow certificate validity intervals,
sshsig verification times and authorized_keys expiry-time options
to accept dates in the UTC time zone in addition to the default
of interpreting them in the system time zone. YYYYMMDD and
YYMMDDHHMM[SS] dates/times will be interpreted as UTC if suffixed
with a 'Z' character.
Also allow certificate validity intervals to be specified in raw
seconds-since-epoch as hex value, e.g. -V 0x1234:0x4567890. This
is intended for use by regress tests and other tools that call
ssh-keygen as part of a CA workflow. bz3468
* sftp(1): allow arguments to the sftp -D option, e.g. sftp -D
"/usr/libexec/sftp-server -el debug3"
* ssh-keygen(1): allow the existing -U (use agent) flag to work
with "-Y sign" operations, where it will be interpreted to require
that the private keys is hosted in an agent; bz3429
Bugfixes
--------
* ssh-keygen(1): implement the "verify-required" certificate option.
This was already documented when support for user-verified FIDO
keys was added, but the ssh-keygen(1) code was missing.
* ssh-agent(1): hook up the restrict_websafe command-line flag;
previously the flag was accepted but never actually used.
* sftp(1): improve filename tab completions: never try to complete
names to non-existent commands, and better match the completion
type (local or remote filename) against the argument position
being completed.
* ssh-keygen(1), ssh(1), ssh-agent(1): several fixes to FIDO key
handling, especially relating to keys that request
user-verification. These should reduce the number of unnecessary
PIN prompts for keys that support intrinsic user verification.
GHPR302, GHPR329
* ssh-keygen(1): when enrolling a FIDO resident key, check if a
credential with matching application and user ID strings already
exists and, if so, prompt the user for confirmation before
overwriting the credential. GHPR329
* sshd(8): improve logging of errors when opening authorized_keys
files. bz2042
* ssh(1): avoid multiplexing operations that could cause SIGPIPE from
causing the client to exit early. bz3454
* ssh_config(5), sshd_config(5): clarify that the RekeyLimit
directive applies to both transmitted and received data. GHPR328
* ssh-keygen(1): avoid double fclose() in error path.
* sshd(8): log an error if pipe() fails while accepting a
connection. bz3447
* ssh(1), ssh-keygen(1): fix possible NULL deref when built without
FIDO support. bz3443
* ssh-keyscan(1): add missing *-sk types to ssh-keyscan manpage.
GHPR294.
* sshd(8): ensure that authentication passwords are cleared from
memory in error paths. GHPR286
* ssh(1), ssh-agent(1): avoid possibility of notifier code executing
kill(-1). GHPR286
* ssh_config(5): note that the ProxyJump directive also accepts the
same tokens as ProxyCommand. GHPR305.
* scp(1): do not not ftruncate(3) files early when in sftp mode. The
previous behaviour of unconditionally truncating the destination
file would cause "scp ~/foo localhost:foo" and the reverse
"scp localhost:foo ~/foo" to delete all the contents of their
destination. bz3431
* ssh-keygen(1): improve error message when 'ssh-keygen -Y sign' is
unable to load a private key; bz3429
* sftp(1), scp(1): when performing operations that glob(3) a remote
path, ensure that the implicit working directory used to construct
that path escapes glob(3) characters. This prevents glob characters
from being processed in places they shouldn't, e.g. "cd /tmp/a*/",
"get *.txt" should have the get operation treat the path "/tmp/a*"
literally and not attempt to expand it.
* ssh(1), sshd(8): be stricter in which characters will be accepted
in specifying a mask length; allow only 0-9. GHPR278
* ssh-keygen(1): avoid printing hash algorithm twice when dumping a
KRL
* ssh(1), sshd(8): continue running local I/O for open channels
during SSH transport rekeying. This should make ~-escapes work in
the client (e.g. to exit) if the connection happened to have
stalled during a rekey event.
* ssh(1), sshd(8): avoid potential poll() spin during rekeying
* Further hardening for sshbuf internals: disallow "reparenting" a
hierarchical sshbuf and zero the entire buffer if reallocation
fails. GHPR287
Portability
-----------
* ssh(1), ssh-keygen(1), sshd(8): automatically enable the built-in
FIDO security key support if libfido2 is found and usable, unless
--without-security-key-builtin was requested.
* ssh(1), ssh-keygen(1), sshd(8): many fixes to make the WinHello
FIDO device usable on Cygwin. The windows://hello FIDO device will
be automatically used by default on this platform unless requested
otherwise, or when probing resident FIDO credentials (an operation
not currently supported by WinHello).
* Portable OpenSSH: remove workarounds for obsolete and unsupported
versions of OpenSSL libcrypto. In particular, this release removes
fallback support for OpenSSL that lacks AES-CTR or AES-GCM.
Those AES cipher modes were added to OpenSSL prior to the minimum
version currently supported by OpenSSH, so this is not expected to
impact any currently supported configurations.
* sshd(8): fix SANDBOX_SECCOMP_FILTER_DEBUG on current Linux/glibc
* All: resync and clean up internal CSPRNG code.
* scp(1), sftp(1), sftp-server(8): avoid linking these programs with
unnecessary libraries. They are no longer linked against libz and
libcrypto. This may be of benefit to space constrained systems
using any of those components in isolation.
* sshd(8): add AUDIT_ARCH_PPC to supported seccomp sandbox
architectures.
* configure: remove special casing of crypt(). configure will no
longer search for crypt() in libcrypto, as it was removed from
there years ago. configure will now only search libc and libcrypt.
* configure: refuse to use OpenSSL 3.0.4 due to potential RCE in its
RSA implementation (CVE-2022-2274) on x86_64.
* All: request 1.1x API compatibility for OpenSSL >=3.x; GHPR322
* ssh(1), ssh-keygen(1), sshd(8): fix a number of missing includes
required by the XMSS code on some platforms.
* sshd(8): cache timezone data in capsicum sandbox.
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
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
Changes since OpenSSH 6.3
=========================
This release fixes a security bug:
* sshd(8): fix a memory corruption problem triggered during rekeying
when an AES-GCM cipher is selected. Full details of the vulnerability
are available at: http://www.openssh.com/txt/gcmrekey.adv
Checksums:
==========
- SHA1 (openssh-6.4.tar.gz) = 4caf1a50eb3a3da821c16298c4aaa576fe24210c
- SHA1 (openssh-6.4p1.tar.gz) = cf5fe0eb118d7e4f9296fbc5d6884965885fc55d
Reporting Bugs:
===============
- Please read http://www.openssh.com/report.html
Security bugs should be reported directly to openssh@openssh.com
OpenSSH is brought to you by Markus Friedl, Niels Provos, Theo de Raadt,
Kevin Steves, Damien Miller, Darren Tucker, Jason McIntyre, Tim Rice and
Ben Lindstrom.
christos