OpenSSH 7.7 released, add new features & fix bugs

OpenSSH is the premier connectivity tool for remote login with the SSH protocol. It encrypts all traffic to eliminate eavesdropping, connection hijacking, and other attacks. In addition, OpenSSH provides a large suite of secure tunneling capabilities, several authentication methods, and sophisticated configuration options.

OpenSSH 7.7 has been released.

Changelog

New Features
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* 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
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* 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.