Download OpenSSH 9.5

Version 9.5 of OpenSSH released. OpenSSH encrypts network traffic to prevent eavesdropping, connection hijacking and other network attacks. In addition, it includes the option to set up so-called secure tunnels and supports various authentication methods. OpenSSH was primarily developed for OpenBSD; users of other operating systems can here justifiably. The changelog for this release looks like this:

Potentially incompatible changes

• ssh-keygen(1): generate Ed25519 keys by default. Ed25519 public keys are very convenient due to their small size. Ed25519 keys are specified in RFC 8709 and OpenSSH has supported them since version 6.5 (January 2014).
• sshd(8): the Subsystem directive now accurately preserves quoting of subsystem commands and arguments. This may change behavior for exotic configurations, but the most common subsystem configuration (sftp-server) is unlikely to be affected.

New features

• ssh(1): add keystroke timing obfuscation to the client. This attempts to hide inter-keystroke timings by sending interactive traffic at fixed intervals (default: every 20ms) when there is only a small amount of data being sent. It also sends fake “chaff” keystrokes for a random interval after the last real keystroke. These are controlled by a new ssh_config ObscureKeystrokeTiming keyword.
• ssh(1), sshd(8): Introduce a transport-level ping facility. This adds a pair of SSH transport protocol messages SSH2_MSG_PING/PONG to implement a ping capability. These messages use numbers in the “local extensions” number space and are advertised using a “ping@openssh.com” ext-info message with a string version number of “0”.
• sshd(8): allow override of Sybsystem directives in sshd Match blocks.

Bug fixes

• scp(1): fix scp in SFTP mode recursive upload and download of directories that contain symlinks to other directories. In scp mode, the links would be followed, but in SFTP mode they were not. bz3611
• ssh-keygen(1): handle cr+lf (instead of just cr) line endings in sshsig signature files.
• ssh(1): interactive mode for ControlPersist sessions if they originally requested a tty.
• sshd(8): make PerSourceMaxStartups first-match-wins
• sshd(8): limit artificial login delay to a reasonable maximum (5s) and don't delay at all for the “none” authentication mechanism.cw bz3602
• sshd(8): Log errors in kex_exchange_identification() with level verbose instead of error to reduce preauth log spam. All of those get logged with a more generic error message by sshpkt_fatal().
• sshd(8): correct math for ClientAliveInterval that caused the probes to be sent less frequently than configured.
• ssh(1): fix regression in OpenSSH 9.4 (mux.c r1.99) that caused multiplexed sessions to ignore SIGINT under some circumstances.

Portability

• Avoid clang zero-call-used-regs=all bug on Apple compilers, which for some reason have version numbers that do not match the upstream clang version numbers. bz#3584
• Fix configure test for zlib 1.3 and later/development versions. bz3604