Download OpenSSH 9.0

OpenSSH encrypts network traffic to prevent eavesdropping, connection hijacking, and other network attacks. In addition, it includes the ability to set up so-called secure tunnels and supports various authentication methods. OpenSSH was developed primarily for OpenBSD; users of other operating systems can here justly. The developers released version 9.0 of OpenSSH a while ago which we still thought worth mentioning. The corresponding announcement looks like this:

Announce: OpenSSH 9.0 released

OpenSSH 9.0 has just been released. It will be available from the mirrors listed at 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: donations.html

Changes since OpenSSH 8.9

This release is focused on bug fixing.

Potentially incompatible changes

• This release switches scp(1) from using the legacy scp/rcp protocol to using the SFTP protocol by default.
• Legacy scp/rcp performs wildcard expansion of remote filenames (eg “scp host:* .”) through the remote shell. This has the side effect of requiring double quoting of shell meta-characters in file names included on scp(1) command-lines, otherwise they could be interpreted as shell commands on the remote side.
• This creates one area of ​​potential incompatibility: scp(1) when using the SFTP protocol no longer requires this finicky and brittle quoting, and attempts to use it may cause transfers to fail. We consider the removal of the need for double-quoting shell characters in file names to be a benefit and do not intend to introduce bug-compatibility for legacy scp/rcp in scp(1) when using the SFTP protocol.
• Another area of ​​potential incompatibility relates to the use of remote paths relative to other user’s home directories, for example – “scp host:~user/file /tmp”. The SFTP protocol has no native way to expand a ~user path. However, sftp-server(8) in OpenSSH 8.7 and later support a protocol extension “expand-path at openssh.com” to support this.
• In case of incompatibility, the scp(1) client may be instructed to use the legacy scp/rcp using the -O flag.

New features

• ssh(1), sshd(8): use the hybrid Streamlined NTRU Prime + x25519 key exchange method by default (“sntrup761x25519-sha512 at openssh.com”). The NTRU algorithm is believed to resist attacks enabled by future quantum computers and is paired with the X25519 ECDH key exchange (the previous default) as a backstop against any weaknesses in NTRU Prime that may be discovered in the future. The combination ensures that the hybrid exchange offers at least as good security as the status quo. We are making this change now (ie ahead of cryptographically-relevant quantum computers) to prevent “capture now, decrypt later” attacks where an adversary who can record and store SSH session ciphertext would be able to decrypt it once a sufficiently advanced quantum computer is available.
• sftp-server(8): support the “copy-data” extension to allow server-side copying of files/data, following the design in draft-ietf-secsh-filexfer-extensions-00. bz2948
• sftp(1): add a “cp” command to allow the sftp client to perform server-side file copies.

Bug fixes

• ssh(1), sshd(8): upstream: fix poll(2) spin when a channel’s output fd closes without data in the channel buffer. bz3405 and bz3411
• sshd(8): pack pollfd array into server listen/accept loop. Could cause the server to hang/spin when MaxStartups > RLIMIT_NOFILE
• ssh-keygen(1): avoid NULL deref via the find-principals and check-novalidate operations. bz3409 and GHPR#307 respectively.
• scp(1): fix a memory leak in argument processing. bz3404
• sshd(8): don’t try to resolve ListenAddress directives in the sshd re-exec path. They are unused after re-exec and parsing errors (possible for example if the host’s network configuration changed) could prevent connections from being accepted.
• sshd(8): when refusing a public key authentication request from a client for using an unapproved or unsupported signature algorithm include the algorithm name in the log message to make debugging easier.

portability

• sshd(8): refactor platform-specific locked account check, fixing an incorrect free() on platforms with both libiaf and shadow passwords (probably only Unixware) GHPR#284,
• ssh(1), sshd(8): Fix possible integer underflow in scan_scaled(3) parsing of K/M/G/etc quantities. bz#3401.
• sshd(8): provide killpg implementation (mostly for Tandem NonStop) GHPR#301.
• Check for missing ftruncate prototype. GHPR#301
• sshd(8): default to not using sandbox when cross compiling. On most systems poll(2) does not work when the number of FDs is reduced with setrlimit, so assume it doesn’t when cross compiling and we can’t run the test. bz#3398.
• sshd(8): allow ppoll_time64 in seccomp sandbox. Should fix sandbox violations on some (at least i386 and armhf) 32bit Linux platforms. bz#3396.
• Improve detection of -fzero-call-used-regs=all support in configure script.