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Author SHA1 Message Date
christos 079fa786c5 OpenSSH 8.5/8.5p1 (2021-03-03)
OpenSSH 8.5 was released on 2021-03-03. 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.

In the SSH protocol, the "ssh-rsa" signature scheme uses the SHA-1
hash algorithm in conjunction with the RSA public key algorithm.
OpenSSH will disable this signature scheme by default in the near
future.

Note that the deactivation of "ssh-rsa" signatures does not necessarily
require cessation of use for RSA keys. In the SSH protocol, keys may be
capable of signing using multiple algorithms. In particular, "ssh-rsa"
keys are capable of signing using "rsa-sha2-256" (RSA/SHA256),
"rsa-sha2-512" (RSA/SHA512) and "ssh-rsa" (RSA/SHA1). Only the last of
these is being turned off by default.

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 that is still
enabled by default.

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 RFC8709 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.

This release enables the UpdateHostKeys option by default to assist
the client by automatically migrating to better algorithms.

[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): fixed a double-free memory corruption that was
   introduced in OpenSSH 8.2 . We treat all such memory faults as
   potentially exploitable. This bug could be reached by an attacker
   with access to the agent socket.

   On modern operating systems where the OS can provide information
   about the user identity connected to a socket, OpenSSH ssh-agent
   and sshd limit agent socket access only to the originating user
   and root. Additional mitigation may be afforded by the system's
   malloc(3)/free(3) implementation, if it detects double-free
   conditions.

   The most likely scenario for exploitation is a user forwarding an
   agent either to an account shared with a malicious user or to a
   host with an attacker holding root access.

 * Portable sshd(8): Prevent excessively long username going to PAM.
   This is a mitigation for a buffer overflow in Solaris' PAM username
   handling (CVE-2020-14871), and is only enabled for Sun-derived PAM
   implementations.  This is not a problem in sshd itself, it only
   prevents sshd from being used as a vector to attack Solaris' PAM.
   It does not prevent the bug in PAM from being exploited via some
   other PAM application. GHPR212


Potentially-incompatible changes
================================

This release includes a number of changes that may affect existing
configurations:

 * ssh(1), sshd(8): this release changes the first-preference signature
   algorithm from ECDSA to ED25519.

 * ssh(1), sshd(8): set the TOS/DSCP specified in the configuration
   for interactive use prior to TCP connect. The connection phase of
   the SSH session is time-sensitive and often explicitly interactive.
   The ultimate interactive/bulk TOS/DSCP will be set after
   authentication completes.

 * ssh(1), sshd(8): remove the pre-standardization cipher
   rijndael-cbc@lysator.liu.se. It is an alias for aes256-cbc before
   it was standardized in RFC4253 (2006), has been deprecated and
   disabled by default since OpenSSH 7.2 (2016) and was only briefly
   documented in ssh.1 in 2001.

 * ssh(1), sshd(8): update/replace the experimental post-quantum
   hybrid key exchange method based on Streamlined NTRU Prime coupled
   with X25519.

   The previous sntrup4591761x25519-sha512@tinyssh.org method is
   replaced with sntrup761x25519-sha512@openssh.com. Per its
   designers, the sntrup4591761 algorithm was superseded almost two
   years ago by sntrup761.

   (note this both the updated method and the one that it replaced are
   disabled by default)

 * ssh(1): disable CheckHostIP by default. It provides insignificant
   benefits while making key rotation significantly more difficult,
   especially for hosts behind IP-based load-balancers.

Changes since OpenSSH 8.4
=========================

New features
------------

 * ssh(1): this release enables UpdateHostkeys by default subject to
   some conservative preconditions:
    - The key was matched in the UserKnownHostsFile (and not in the
      GlobalKnownHostsFile).
    - The same key does not exist under another name.
    - A certificate host key is not in use.
    - known_hosts contains no matching wildcard hostname pattern.
    - VerifyHostKeyDNS is not enabled.
    - The default UserKnownHostsFile is in use.

   We expect some of these conditions will be modified or relaxed in
   future.

 * ssh(1), sshd(8): add a new LogVerbose configuration directive for
   that allows forcing maximum debug logging by file/function/line
   pattern-lists.

 * ssh(1): when prompting the user to accept a new hostkey, display
   any other host names/addresses already associated with the key.

 * ssh(1): allow UserKnownHostsFile=none to indicate that no
   known_hosts file should be used to identify host keys.

 * ssh(1): add a ssh_config KnownHostsCommand option that allows the
   client to obtain known_hosts data from a command in addition to
   the usual files.

 * ssh(1): add a ssh_config PermitRemoteOpen option that allows the
   client to restrict the destination when RemoteForward is used
   with SOCKS.

 * ssh(1): for FIDO keys, if a signature operation fails with a
   "incorrect PIN" reason and no PIN was initially requested from the
   user, then request a PIN and retry the operation. This supports
   some biometric devices that fall back to requiring PIN when reading
   of the biometric failed, and devices that require PINs for all
   hosted credentials.

 * sshd(8): implement client address-based rate-limiting via new
   sshd_config(5) PerSourceMaxStartups and PerSourceNetBlockSize
   directives that provide more fine-grained control on a per-origin
   address basis than the global MaxStartups limit.

Bugfixes
--------

 * ssh(1): Prefix keyboard interactive prompts with "(user@host)" to
   make it easier to determine which connection they are associated
   with in cases like scp -3, ProxyJump, etc. bz#3224

 * sshd(8): fix sshd_config SetEnv directives located inside Match
   blocks. GHPR201

 * ssh(1): when requesting a FIDO token touch on stderr, inform the
   user once the touch has been recorded.

 * ssh(1): prevent integer overflow when ridiculously large
   ConnectTimeout values are specified, capping the effective value
   (for most platforms) at 24 days. bz#3229

 * ssh(1): consider the ECDSA key subtype when ordering host key
   algorithms in the client.

 * ssh(1), sshd(8): rename the PubkeyAcceptedKeyTypes keyword to
   PubkeyAcceptedAlgorithms. The previous name incorrectly suggested
   that it control allowed key algorithms, when this option actually
   specifies the signature algorithms that are accepted. The previous
   name remains available as an alias. bz#3253

 * ssh(1), sshd(8): similarly, rename HostbasedKeyTypes (ssh) and
   HostbasedAcceptedKeyTypes (sshd) to HostbasedAcceptedAlgorithms.

 * sftp-server(8): add missing lsetstat@openssh.com documentation
   and advertisement in the server's SSH2_FXP_VERSION hello packet.

 * ssh(1), sshd(8): more strictly enforce KEX state-machine by
   banning packet types once they are received. Fixes memleak caused
   by duplicate SSH2_MSG_KEX_DH_GEX_REQUEST (oss-fuzz #30078).

 * sftp(1): allow the full range of UIDs/GIDs for chown/chgrp on 32bit
   platforms instead of being limited by LONG_MAX. bz#3206

 * Minor man page fixes (capitalization, commas, etc.) bz#3223

 * sftp(1): when doing an sftp recursive upload or download of a
   read-only directory, ensure that the directory is created with
   write and execute permissions in the interim so that the transfer
   can actually complete, then set the directory permission as the
   final step. bz#3222

 * ssh-keygen(1): document the -Z, check the validity of its argument
   earlier and provide a better error message if it's not correct.
   bz#2879

 * ssh(1): ignore comments at the end of config lines in ssh_config,
   similar to what we already do for sshd_config. bz#2320

 * sshd_config(5): mention that DisableForwarding is valid in a
   sshd_config Match block. bz3239

 * sftp(1): fix incorrect sorting of "ls -ltr" under some
   circumstances. bz3248.

 * ssh(1), sshd(8): fix potential integer truncation of (unlikely)
   timeout values. bz#3250

 * ssh(1): make hostbased authentication send the signature algorithm
   in its SSH2_MSG_USERAUTH_REQUEST packets instead of the key type.
   This make HostbasedAcceptedAlgorithms do what it is supposed to -
   filter on signature algorithm and not key type.

Portability
-----------

 * sshd(8): add a number of platform-specific syscalls to the Linux
   seccomp-bpf sandbox. bz#3232 bz#3260

 * sshd(8): remove debug message from sigchld handler that could cause
   deadlock on some platforms. bz#3259

 * Sync contrib/ssh-copy-id with upstream.

 * unittests: add a hostname function for systems that don't have it.
   Some systems don't have a hostname command (it's not required by
   POSIX). The do have uname -n (which is), but not all of those have
   it report the FQDN.

Checksums:
==========

 - SHA1 (openssh-8.5.tar.gz) = 04cae43c389fb411227c01219e4eb46e3113f34e
 - SHA256 (openssh-8.5.tar.gz) = 5qB2CgzNG4io4DmChTjHgCWqRWvEOvCKJskLdJCz+SU=

 - SHA1 (openssh-8.5p1.tar.gz) = 72eadcbe313b07b1dd3b693e41d3cd56d354e24e
 - SHA256 (openssh-8.5p1.tar.gz) = 9S8/QdQpqpkY44zyAK8iXM3Y5m8FLaVyhwyJc3ZG7CU=

Please note that the SHA256 signatures are base64 encoded and not
hexadecimal (which is the default for most checksum tools). The PGP
key used to sign the releases is available from the mirror sites:
https://cdn.openbsd.org/pub/OpenBSD/OpenSSH/RELEASE_KEY.asc

Please note that the OpenPGP key used to sign releases has been
rotated for this release. The new key has been signed by the previous
key to provide continuity.

Reporting Bugs:
===============

- Please read https://www.openssh.com/report.html
  Security bugs should be reported directly to openssh@openssh.com
2021-03-05 17:45:24 +00:00
christos 7808dbe183 OpenSSH 8.2/8.2p1 (2020-02-14)
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
2020-02-27 00:21:35 +00:00
christos c856f84425 Import 8.0:
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
2019-04-20 17:13:53 +00:00
christos 4b39feda77 Potentially-incompatible changes
================================

This release includes a number of changes that may affect existing
configurations:

 * 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
2018-08-26 07:39:56 +00:00
christos 078dfabc17 OpenSSH 7.7 was released on 2018-04-02. It is available from the
mirrors listed at http://www.openssh.com/ shortly.

OpenSSH is a 100% complete SSH protocol 2.0 implementation and
includes sftp client and server support.

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

Potentially-incompatible changes
================================

This release includes a number of changes that may affect existing
configurations:

 * 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.

Changes since OpenSSH 7.6
=========================

This is primarily a bugfix release.

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.

Checksums:
==========

- SHA1 (openssh-7.7.tar.gz) = 24812e05fa233014c847c7775748316e7f8a836c
- SHA256 (openssh-7.7.tar.gz) = T4ua1L/vgAYqwB0muRahvnm5ZUr3PLY9nPljaG8egvo=

- SHA1 (openssh-7.7p1.tar.gz) = 446fe9ed171f289f0d62197dffdbfdaaf21c49f2
- SHA256 (openssh-7.7p1.tar.gz) = 1zvn5oTpnvzQJL4Vowv/y+QbASsvezyQhK7WIXdea48=

Please note that the SHA256 signatures are base64 encoded and not
hexadecimal (which is the default for most checksum tools). The PGP
key used to sign the releases is available as RELEASE_KEY.asc from
the mirror sites.

Reporting Bugs:
===============

- Please read http://www.openssh.com/report.html
  Security bugs should be reported directly to openssh@openssh.com
2018-04-06 18:56:05 +00:00
christos 09444dc97b 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.
2017-10-07 19:36:11 +00:00
christos 6594a05c52 Future deprecation notice
=========================

We plan on retiring more legacy cryptography in a near-future
release, specifically:

 * Refusing all RSA keys smaller than 1024 bits (the current minimum
   is 768 bits)

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
2016-03-11 01:49:56 +00:00
christos d7010b65f1 Changes since OpenSSH 6.6
=========================

Potentially-incompatible changes

 * sshd(8): The default set of ciphers and MACs has been altered to
   remove unsafe algorithms. In particular, CBC ciphers and arcfour*
   are disabled by default.

   The full set of algorithms remains available if configured
   explicitly via the Ciphers and MACs sshd_config options.

 * sshd(8): Support for tcpwrappers/libwrap has been removed.

 * OpenSSH 6.5 and 6.6 have a bug that causes ~0.2% of connections
   using the curve25519-sha256@libssh.org KEX exchange method to fail
   when connecting with something that implements the specification
   correctly. OpenSSH 6.7 disables this KEX method when speaking to
   one of the affected versions.

New Features

 * Major internal refactoring to begin to make part of OpenSSH usable
   as a library. So far the wire parsing, key handling and KRL code
   has been refactored. Please note that we do not consider the API
   stable yet, nor do we offer the library in separable form.

 * ssh(1), sshd(8): Add support for Unix domain socket forwarding.
   A remote TCP port may be forwarded to a local Unix domain socket
   and vice versa or both ends may be a Unix domain socket.

 * ssh(1), ssh-keygen(1): Add support for SSHFP DNS records for
   ED25519 key types.

 * sftp(1): Allow resumption of interrupted uploads.

 * ssh(1): When rekeying, skip file/DNS lookups of the hostkey if it
   is the same as the one sent during initial key exchange; bz#2154

 * sshd(8): Allow explicit ::1 and 127.0.0.1 forwarding bind
   addresses when GatewayPorts=no; allows client to choose address
   family; bz#2222

 * sshd(8): Add a sshd_config PermitUserRC option to control whether
   ~/.ssh/rc is executed, mirroring the no-user-rc authorized_keys
   option; bz#2160

 * ssh(1): Add a %C escape sequence for LocalCommand and ControlPath
   that expands to a unique identifer based on a hash of the tuple of
   (local host, remote user, hostname, port). Helps avoid exceeding
   miserly pathname limits for Unix domain sockets in multiplexing
   control paths; bz#2220

 * sshd(8): Make the "Too many authentication failures" message
   include the user, source address, port and protocol in a format
   similar to the authentication success / failure messages; bz#2199

 * Added unit and fuzz tests for refactored code. These are run
   automatically in portable OpenSSH via the "make tests" target.

Bugfixes

 * sshd(8): Fix remote forwarding with the same listen port but
   different listen address.

 * ssh(1): Fix inverted test that caused PKCS#11 keys that were
   explicitly listed in ssh_config or on the commandline not to be
   preferred.

 * ssh-keygen(1): Fix bug in KRL generation: multiple consecutive
   revoked certificate serial number ranges could be serialised to an
   invalid format. Readers of a broken KRL caused by this bug will
   fail closed, so no should-have-been-revoked key will be accepted.

 * ssh(1): Reflect stdio-forward ("ssh -W host:port ...") failures in
   exit status. Previously we were always returning 0; bz#2255

 * ssh(1), ssh-keygen(1): Make Ed25519 keys' title fit properly in the
   randomart border; bz#2247

 * ssh-agent(1): Only cleanup agent socket in the main agent process
   and not in any subprocesses it may have started (e.g. forked
   askpass). Fixes agent sockets being zapped when askpass processes
   fatal(); bz#2236

 * ssh-add(1): Make stdout line-buffered; saves partial output getting
   lost when ssh-add fatal()s part-way through (e.g. when listing keys
   from an agent that supports key types that ssh-add doesn't);
   bz#2234

 * ssh-keygen(1): When hashing or removing hosts, don't choke on
   @revoked markers and don't remove @cert-authority markers; bz#2241

 * ssh(1): Don't fatal when hostname canonicalisation fails and a
   ProxyCommand is in use; continue and allow the ProxyCommand to
   connect anyway (e.g. to a host with a name outside the DNS behind
   a bastion)

 * scp(1): When copying local->remote fails during read, don't send
   uninitialised heap to the remote end.

 * sftp(1): Fix fatal "el_insertstr failed" errors when tab-completing
   filenames with  a single quote char somewhere in the string;
   bz#2238

 * ssh-keyscan(1): Scan for Ed25519 keys by default.

 * ssh(1): When using VerifyHostKeyDNS with a DNSSEC resolver, down-
   convert any certificate keys to plain keys and attempt SSHFP
   resolution.  Prevents a server from skipping SSHFP lookup and
   forcing a new-hostkey dialog by offering only certificate keys.

 * sshd(8): Avoid crash at exit via NULL pointer reference; bz#2225

 * Fix some strict-alignment errors.

Portable OpenSSH

 * Portable OpenSSH now supports building against libressl-portable.

 * Portable OpenSSH now requires openssl 0.9.8f or greater. Older
   versions are no longer supported.

 * In the OpenSSL version check, allow fix version upgrades (but not
   downgrades. Debian bug #748150.

 * sshd(8): On Cygwin, determine privilege separation user at runtime,
   since it may need to be a domain account.

 * sshd(8): Don't attempt to use vhangup on Linux. It doesn't work for
   non-root users, and for them it just messes up the tty settings.

 * Use CLOCK_BOOTTIME in preference to CLOCK_MONOTONIC when it is
   available. It considers time spent suspended, thereby ensuring
   timeouts (e.g. for expiring agent keys) fire correctly.  bz#2228

 * Add support for ed25519 to opensshd.init init script.

 * sftp-server(8): On platforms that support it, use prctl() to
   prevent sftp-server from accessing /proc/self/{mem,maps}

Changes since OpenSSH 6.5
=========================

This is primarily a bugfix release.

Security:

 * sshd(8): when using environment passing with a sshd_config(5)
   AcceptEnv pattern with a wildcard. OpenSSH prior to 6.6 could be
   tricked into accepting any enviornment variable that contains the
   characters before the wildcard character.

New / changed features:

 * ssh(1), sshd(8): this release removes the J-PAKE authentication code.
   This code was experimental, never enabled and had been unmaintained
   for some time.

 * ssh(1): when processing Match blocks, skip 'exec' clauses other clauses
   predicates failed to match.

 * ssh(1): if hostname canonicalisation is enabled and results in the
   destination hostname being changed, then re-parse ssh_config(5) files
   using the new destination hostname. This gives 'Host' and 'Match'
   directives that use the expanded hostname a chance to be applied.

Bugfixes:

 * ssh(1): avoid spurious "getsockname failed: Bad file descriptor" in
   ssh -W. bz#2200, debian#738692

 * sshd(8): allow the shutdown(2) syscall in seccomp-bpf and systrace
   sandbox modes, as it is reachable if the connection is terminated
   during the pre-auth phase.

 * ssh(1), sshd(8): fix unsigned overflow that in SSH protocol 1 bignum
   parsing. Minimum key length checks render this bug unexploitable to
   compromise SSH 1 sessions.

 * sshd_config(5): clarify behaviour of a keyword that appears in
   multiple matching Match blocks. bz#2184

 * ssh(1): avoid unnecessary hostname lookups when canonicalisation is
   disabled. bz#2205

 * sshd(8): avoid sandbox violation crashes in GSSAPI code by caching
   the supported list of GSSAPI mechanism OIDs before entering the
   sandbox. bz#2107

 * ssh(1): fix possible crashes in SOCKS4 parsing caused by assumption
   that the SOCKS username is nul-terminated.

 * ssh(1): fix regression for UsePrivilegedPort=yes when BindAddress is
   not specified.

 * ssh(1), sshd(8): fix memory leak in ECDSA signature verification.

 * ssh(1): fix matching of 'Host' directives in ssh_config(5) files
   to be case-insensitive again (regression in 6.5).

Portable OpenSSH:

 * sshd(8): don't fatal if the FreeBSD Capsicum is offered by the
   system headers and libc but is not supported by the kernel.
 * Fix build using the HP-UX compiler.

Changes since OpenSSH 6.4
=========================

This is a feature-focused release.

New features:

 * ssh(1), sshd(8): Add support for key exchange using elliptic-curve
   Diffie Hellman in Daniel Bernstein's Curve25519. This key exchange
   method is the default when both the client and server support it.

 * ssh(1), sshd(8): Add support for Ed25519 as a public key type.
   Ed25519 is a elliptic curve signature scheme that offers
   better security than ECDSA and DSA and good performance. It may be
   used for both user and host keys.

 * Add a new private key format that uses a bcrypt KDF to better
   protect keys at rest. This format is used unconditionally for
   Ed25519 keys, but may be requested when generating or saving
   existing keys of other types via the -o ssh-keygen(1) option.
   We intend to make the new format the default in the near future.
   Details of the new format are in the PROTOCOL.key file.

 * ssh(1), sshd(8): Add a new transport cipher
   "chacha20-poly1305@openssh.com" that combines Daniel Bernstein's
   ChaCha20 stream cipher and Poly1305 MAC to build an authenticated
   encryption mode. Details are in the PROTOCOL.chacha20poly1305 file.

 * ssh(1), sshd(8): Refuse RSA keys from old proprietary clients and
   servers that use the obsolete RSA+MD5 signature scheme. It will
   still be possible to connect with these clients/servers but only
   DSA keys will be accepted, and OpenSSH will refuse connection
   entirely in a future release.

 * ssh(1), sshd(8): Refuse old proprietary clients and servers that
   use a weaker key exchange hash calculation.

 * ssh(1): Increase the size of the Diffie-Hellman groups requested
   for each symmetric key size. New values from NIST Special
   Publication 800-57 with the upper limit specified by RFC4419.

 * ssh(1), ssh-agent(1): Support PKCS#11 tokens that only provide
   X.509 certs instead of raw public keys (requested as bz#1908).

 * ssh(1): Add a ssh_config(5) "Match" keyword that allows
   conditional configuration to be applied by matching on hostname,
   user and result of arbitrary commands.

 * ssh(1): Add support for client-side hostname canonicalisation
   using a set of DNS suffixes and rules in ssh_config(5). This
   allows unqualified names to be canonicalised to fully-qualified
   domain names to eliminate ambiguity when looking up keys in
   known_hosts or checking host certificate names.

 * sftp-server(8): Add the ability to whitelist and/or blacklist sftp
   protocol requests by name.

 * sftp-server(8): Add a sftp "fsync@openssh.com" to support calling
   fsync(2) on an open file handle.

 * sshd(8): Add a ssh_config(5) PermitTTY to disallow TTY allocation,
   mirroring the longstanding no-pty authorized_keys option.

 * ssh(1): Add a ssh_config ProxyUseFDPass option that supports the
   use of ProxyCommands that establish a connection and then pass a
   connected file descriptor back to ssh(1). This allows the
   ProxyCommand to exit rather than staying around to transfer data.

Bugfixes:

 * ssh(1), sshd(8): Fix potential stack exhaustion caused by nested
   certificates.

 * ssh(1): bz#1211: make BindAddress work with UsePrivilegedPort.

 * sftp(1): bz#2137: fix the progress meter for resumed transfer.

 * ssh-add(1): bz#2187: do not request smartcard PIN when removing
   keys from ssh-agent.

 * sshd(8): bz#2139: fix re-exec fallback when original sshd binary
   cannot be executed.

 * ssh-keygen(1): Make relative-specified certificate expiry times
   relative to current time and not the validity start time.

 * sshd(8): bz#2161: fix AuthorizedKeysCommand inside a Match block.

 * sftp(1): bz#2129: symlinking a file would incorrectly canonicalise
   the target path.

 * ssh-agent(1): bz#2175: fix a use-after-free in the PKCS#11 agent
   helper executable.

 * sshd(8): Improve logging of sessions to include the user name,
   remote host and port, the session type (shell, command, etc.) and
   allocated TTY (if any).

 * sshd(8): bz#1297: tell the client (via a debug message) when
   their preferred listen address has been overridden by the
   server's GatewayPorts setting.

 * sshd(8): bz#2162: include report port in bad protocol banner
   message.

 * sftp(1): bz#2163: fix memory leak in error path in do_readdir().

 * sftp(1): bz#2171: don't leak file descriptor on error.

 * sshd(8): Include the local address and port in "Connection from
   ..." message (only shown at loglevel>=verbose).

Portable OpenSSH:

 * Please note that this is the last version of Portable OpenSSH that
   will support versions of OpenSSL prior to 0.9.6. Support (i.e.
   SSH_OLD_EVP) will be removed following the 6.5p1 release.

 * Portable OpenSSH will attempt compile and link as a Position
   Independent Executable on Linux, OS X and OpenBSD on recent gcc-
   like compilers. Other platforms and older/other compilers may
   request this using the --with-pie configure flag.

 * A number of other toolchain-related hardening options are used
   automatically if available, including -ftrapv to abort on signed
   integer overflow and options to write-protect dynamic linking
   information.  The use of these options may be disabled using the
   --without-hardening configure flag.

 * If the toolchain supports it, one of the -fstack-protector-strong,
   -fstack-protector-all or -fstack-protector compilation flag are
   used to add guards to mitigate attacks based on stack overflows.
   The use of these options may be disabled using the
   --without-stackprotect configure option.

 * sshd(8): Add support for pre-authentication sandboxing using the
   Capsicum API introduced in FreeBSD 10.

 * Switch to a ChaCha20-based arc4random() PRNG for platforms that do
   not provide their own.

 * sshd(8): bz#2156: restore Linux oom_adj setting when handling
   SIGHUP to maintain behaviour over retart.

 * sshd(8): bz#2032: use local username in krb5_kuserok check rather
   than full client name which may be of form user@REALM.

 * ssh(1), sshd(8): Test for both the presence of ECC NID numbers in
   OpenSSL and that they actually work. Fedora (at least) has
   NID_secp521r1 that doesn't work.

 * bz#2173: use pkg-config --libs to include correct -L location for
   libedit.
2014-10-19 16:28:33 +00:00
christos f123b0a5e8 Import new openssh to address
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.
2013-11-08 17:58:08 +00:00
christos ddfd2449b0 from ftp.openbsd.org 2012-05-02 02:13:04 +00:00
christos 7d50d346f3 from ftp.openbsd.org 2011-07-24 15:08:11 +00:00
adam f6a8b914ed Imported openssh-5.6 2010-11-21 17:05:36 +00:00