================================
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.
=========================
We plan on retiring more legacy cryptography in a near-future
release, specifically:
* Refusing all RSA keys smaller than 1024 bits (the current minimum
is 768 bits)
This list reflects our current intentions, but please check the final
release notes for future releases.
Potentially-incompatible changes
================================
This release disables a number of legacy cryptographic algorithms
by default in ssh:
* Several ciphers blowfish-cbc, cast128-cbc, all arcfour variants
and the rijndael-cbc aliases for AES.
* MD5-based and truncated HMAC algorithms.
These algorithms are already disabled by default in sshd.
Changes since OpenSSH 7.1p2
===========================
This is primarily a bugfix release.
Security
--------
* ssh(1), sshd(8): remove unfinished and unused roaming code (was
already forcibly disabled in OpenSSH 7.1p2).
* ssh(1): eliminate fallback from untrusted X11 forwarding to
trusted forwarding when the X server disables the SECURITY
extension.
* ssh(1), sshd(8): increase the minimum modulus size supported for
diffie-hellman-group-exchange to 2048 bits.
* sshd(8): pre-auth sandboxing is now enabled by default (previous
releases enabled it for new installations via sshd_config).
New Features
------------
* all: add support for RSA signatures using SHA-256/512 hash
algorithms based on draft-rsa-dsa-sha2-256-03.txt and
draft-ssh-ext-info-04.txt.
* ssh(1): Add an AddKeysToAgent client option which can be set to
'yes', 'no', 'ask', or 'confirm', and defaults to 'no'. When
enabled, a private key that is used during authentication will be
added to ssh-agent if it is running (with confirmation enabled if
set to 'confirm').
* sshd(8): add a new authorized_keys option "restrict" that includes
all current and future key restrictions (no-*-forwarding, etc.).
Also add permissive versions of the existing restrictions, e.g.
"no-pty" -> "pty". This simplifies the task of setting up
restricted keys and ensures they are maximally-restricted,
regardless of any permissions we might implement in the future.
* ssh(1): add ssh_config CertificateFile option to explicitly list
certificates. bz#2436
* ssh-keygen(1): allow ssh-keygen to change the key comment for all
supported formats.
* ssh-keygen(1): allow fingerprinting from standard input, e.g.
"ssh-keygen -lf -"
* ssh-keygen(1): allow fingerprinting multiple public keys in a
file, e.g. "ssh-keygen -lf ~/.ssh/authorized_keys" bz#1319
* sshd(8): support "none" as an argument for sshd_config
Foreground and ChrootDirectory. Useful inside Match blocks to
override a global default. bz#2486
* ssh-keygen(1): support multiple certificates (one per line) and
reading from standard input (using "-f -") for "ssh-keygen -L"
* ssh-keyscan(1): add "ssh-keyscan -c ..." flag to allow fetching
certificates instead of plain keys.
* ssh(1): better handle anchored FQDNs (e.g. 'cvs.openbsd.org.') in
hostname canonicalisation - treat them as already canonical and
remove the trailing '.' before matching ssh_config.
Bugfixes
--------
* sftp(1): existing destination directories should not terminate
recursive uploads (regression in openssh 6.8) bz#2528
* ssh(1), sshd(8): correctly send back SSH2_MSG_UNIMPLEMENTED
replies to unexpected messages during key exchange. bz#2949
* ssh(1): refuse attempts to set ConnectionAttempts=0, which does
not make sense and would cause ssh to print an uninitialised stack
variable. bz#2500
* ssh(1): fix errors when attempting to connect to scoped IPv6
addresses with hostname canonicalisation enabled.
* sshd_config(5): list a couple more options usable in Match blocks.
bz#2489
* sshd(8): fix "PubkeyAcceptedKeyTypes +..." inside a Match block.
* ssh(1): expand tilde characters in filenames passed to -i options
before checking whether or not the identity file exists. Avoids
confusion for cases where shell doesn't expand (e.g. "-i ~/file"
vs. "-i~/file"). bz#2481
* ssh(1): do not prepend "exec" to the shell command run by "Match
exec" in a config file, which could cause some commands to fail
in certain environments. bz#2471
* ssh-keyscan(1): fix output for multiple hosts/addrs on one line
when host hashing or a non standard port is in use bz#2479
* sshd(8): skip "Could not chdir to home directory" message when
ChrootDirectory is active. bz#2485
* ssh(1): include PubkeyAcceptedKeyTypes in ssh -G config dump.
* sshd(8): avoid changing TunnelForwarding device flags if they are
already what is needed; makes it possible to use tun/tap
networking as non-root user if device permissions and interface
flags are pre-established
* ssh(1), sshd(8): RekeyLimits could be exceeded by one packet.
bz#2521
* ssh(1): fix multiplexing master failure to notice client exit.
* ssh(1), ssh-agent(1): avoid fatal() for PKCS11 tokens that present
empty key IDs. bz#1773
* sshd(8): avoid printf of NULL argument. bz#2535
* ssh(1), sshd(8): allow RekeyLimits larger than 4GB. bz#2521
* ssh-keygen(1): sshd(8): fix several bugs in (unused) KRL signature
support.
* ssh(1), sshd(8): fix connections with peers that use the key
exchange guess feature of the protocol. bz#2515
* sshd(8): include remote port number in log messages. bz#2503
* ssh(1): don't try to load SSHv1 private key when compiled without
SSHv1 support. bz#2505
* ssh-agent(1), ssh(1): fix incorrect error messages during key
loading and signing errors. bz#2507
* ssh-keygen(1): don't leave empty temporary files when performing
known_hosts file edits when known_hosts doesn't exist.
* sshd(8): correct packet format for tcpip-forward replies for
requests that don't allocate a port bz#2509
* ssh(1), sshd(8): fix possible hang on closed output. bz#2469
* ssh(1): expand %i in ControlPath to UID. bz#2449
* ssh(1), sshd(8): fix return type of openssh_RSA_verify. bz#2460
* ssh(1), sshd(8): fix some option parsing memory leaks. bz#2182
* ssh(1): add a some debug output before DNS resolution; it's a
place where ssh could previously silently stall in cases of
unresponsive DNS servers. bz#2433
* ssh(1): remove spurious newline in visual hostkey. bz#2686
* ssh(1): fix printing (ssh -G ...) of HostKeyAlgorithms=+...
* ssh(1): fix expansion of HostkeyAlgorithms=+...
Documentation
-------------
* ssh_config(5), sshd_config(5): update default algorithm lists to
match current reality. bz#2527
* ssh(1): mention -Q key-plain and -Q key-cert query options.
bz#2455
* sshd_config(8): more clearly describe what AuthorizedKeysFile=none
does.
* ssh_config(5): better document ExitOnForwardFailure. bz#2444
* sshd(5): mention internal DH-GEX fallback groups in manual.
bz#2302
* sshd_config(5): better description for MaxSessions option.
bz#2531
Portability
-----------
* ssh(1), sftp-server(8), ssh-agent(1), sshd(8): Support Illumos/
Solaris fine-grained privileges. Including a pre-auth privsep
sandbox and several pledge() emulations. bz#2511
* Renovate redhat/openssh.spec, removing deprecated options and
syntax.
* configure: allow --without-ssl-engine with --without-openssl
* sshd(8): fix multiple authentication using S/Key. bz#2502
* sshd(8): read back from libcrypto RAND_* before dropping
privileges. Avoids sandboxing violations with BoringSSL.
* Fix name collision with system-provided glob(3) functions.
bz#2463
* Adapt Makefile to use ssh-keygen -A when generating host keys.
bz#2459
* configure: correct default value for --with-ssh1 bz#2457
* configure: better detection of _res symbol bz#2259
* support getrandom() syscall on Linux
Changes since OpenSSH 6.9
=========================
This focus of this release is primarily to deprecate weak, legacy
and/or unsafe cryptography.
Security
--------
* sshd(8): OpenSSH 6.8 and 6.9 incorrectly set TTYs to be world-
writable. Local attackers may be able to write arbitrary messages
to logged-in users, including terminal escape sequences.
Reported by Nikolay Edigaryev.
* sshd(8): Portable OpenSSH only: Fixed a privilege separation
weakness related to PAM support. Attackers who could successfully
compromise the pre-authentication process for remote code
execution and who had valid credentials on the host could
impersonate other users. Reported by Moritz Jodeit.
* sshd(8): Portable OpenSSH only: Fixed a use-after-free bug
related to PAM support that was reachable by attackers who could
compromise the pre-authentication process for remote code
execution. Also reported by Moritz Jodeit.
* sshd(8): fix circumvention of MaxAuthTries using keyboard-
interactive authentication. By specifying a long, repeating
keyboard-interactive "devices" string, an attacker could request
the same authentication method be tried thousands of times in
a single pass. The LoginGraceTime timeout in sshd(8) and any
authentication failure delays implemented by the authentication
mechanism itself were still applied. Found by Kingcope.
Potentially-incompatible Changes
--------------------------------
* Support for the legacy SSH version 1 protocol is disabled by
default at compile time.
* Support for the 1024-bit diffie-hellman-group1-sha1 key exchange
is disabled by default at run-time. It may be re-enabled using
the instructions at http://www.openssh.com/legacy.html
* Support for ssh-dss, ssh-dss-cert-* host and user keys is disabled
by default at run-time. These may be re-enabled using the
instructions at http://www.openssh.com/legacy.html
* Support for the legacy v00 cert format has been removed.
* The default for the sshd_config(5) PermitRootLogin option has
changed from "yes" to "prohibit-password".
* PermitRootLogin=without-password/prohibit-password now bans all
interactive authentication methods, allowing only public-key,
hostbased and GSSAPI authentication (previously it permitted
keyboard-interactive and password-less authentication if those
were enabled).
New Features
------------
* ssh_config(5): add PubkeyAcceptedKeyTypes option to control which
public key types are available for user authentication.
* sshd_config(5): add HostKeyAlgorithms option to control which
public key types are offered for host authentications.
* ssh(1), sshd(8): extend Ciphers, MACs, KexAlgorithms,
HostKeyAlgorithms, PubkeyAcceptedKeyTypes and HostbasedKeyTypes
options to allow appending to the default set of algorithms
instead of replacing it. Options may now be prefixed with a '+'
to append to the default, e.g. "HostKeyAlgorithms=+ssh-dss".
* sshd_config(5): PermitRootLogin now accepts an argument of
'prohibit-password' as a less-ambiguous synonym of 'without-
password'.
Bugfixes
--------
* ssh(1), sshd(8): add compatability workarounds for Cisco and more
PuTTY versions. bz#2424
* Fix some omissions and errors in the PROTOCOL and PROTOCOL.mux
documentation relating to Unix domain socket forwarding;
bz#2421 bz#2422
* ssh(1): Improve the ssh(1) manual page to include a better
description of Unix domain socket forwarding; bz#2423
* ssh(1), ssh-agent(1): skip uninitialised PKCS#11 slots, fixing
failures to load keys when they are present. bz#2427
* ssh(1), ssh-agent(1): do not ignore PKCS#11 hosted keys that wth
empty CKA_ID; bz#2429
* sshd(8): clarify documentation for UseDNS option; bz#2045
christos