OpenSSH 5.7 released

Valic —  January 24, 2011 — Leave a comment

OpenSSH 5.7 has just been released. It will be available from the mirrors listed at shortly.

OpenSSH is a 100% complete SSH protocol version 1.3, 1.5 and 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.

Changes since OpenSSH 5.6


* Implement Elliptic Curve Cryptography modes for key exchange (ECDH) and host/user keys (ECDSA) as specified by RFC5656. ECDH and ECDSA
offer better performance than plain DH and DSA at the same equivalent symmetric key length, as well as much shorter keys.

Only the mandatory sections of RFC5656 are implemented, specifically the three REQUIRED curves nistp256, nistp384 and nistp521 and only ECDH and ECDSA. Point compression (optional in RFC5656) is NOT implemented.

Certificate host and user keys using the new ECDSA key types are supported – an ECDSA key may be certified, and an ECDSA key may act as a CA to sign certificates.

ECDH in a 256 bit curve field is the preferred key agreement algorithm when both the client and server support it. ECDSA host keys are preferred when learning a host’s keys for the first time, or can be learned using ssh-keyscan(1).

* sftp(1)/sftp-server(8): add a protocol extension to support a hard link operation. It is available through the “ln” command in the client. The old “ln” behaviour of creating a symlink is available using its “-s” option or through the preexisting “symlink” command

* scp(1): Add a new -3 option to scp: Copies between two remote hosts are transferred through the local host. Without this option the data is copied directly between the two remote hosts.

* ssh(1): automatically order the hostkeys requested by the client based on which hostkeys are already recorded in known_hosts. This
avoids hostkey warnings when connecting to servers with new ECDSA keys, since these are now preferred when learning hostkeys for the
first time.

* ssh(1)/sshd(8): add a new IPQoS option to specify arbitrary TOS/DSCP/QoS values instead of hardcoding lowdelay/throughput. bz#1733

* sftp(1): the sftp client is now significantly faster at performing directory listings, using OpenBSD glob(3) extensions to preserve the results of stat(3) operations performed in the course of its execution rather than performing expensive round trips to fetch them again afterwards.

* ssh(1): “atomically” create the listening mux socket by binding it on a temporary name and then linking it into position after listen() has succeeded. This allows the mux clients to determine that the server socket is either ready or stale without races. stale server sockets are now automatically removed.

* ssh(1)/sshd(8): add a KexAlgorithms knob to the client and server configuration to allow selection of which key exchange methods are used by ssh(1) and sshd(8) and their order of preference.

* sftp(1)/scp(1): factor out bandwidth limiting code from scp(1) into a generic bandwidth limiter that can be attached using the atomicio
callback mechanism and use it to add a bandwidth limit option to sftp(1).


* ssh(1)/ssh-agent(1): honour $TMPDIR for client xauth and ssh-agent temporary directories.

* ssh(1): avoid NULL deref on receiving a channel request on an unknown or invalid channel;

* sshd(8): remove a debug() that pollutes stderr on client connecting to a server in debug mode;

* scp(1): pass through ssh command-line flags and options when doing remote-remote transfers, e.g. to enable agent forwarding which is particularly useful in this case;

* sftp-server(8): umask should be parsed as octal

* sftp(1): escape ‘[‘ in filename tab-completion

* ssh(1): Typo in confirmation message.

* sshd(8): prevent free() of string in .rodata when overriding AuthorizedKeys in a Match block

* sshd(8): Use default shell /bin/sh if $SHELL is “”

* ssh(1): kill proxy command on fatal() (we already killed it on clean exit);

* ssh(1): install a SIGCHLD handler to reap expiried child process;

* Support building against openssl-1.0.0a

Portable OpenSSH Bugfixes:

* Use mandoc as preferred manpage formatter if it is present, followed by nroff and groff respectively.

* sshd(8): Relax permission requirement on btmp logs to allow group read/write

* bz#1840: fix warning when configuring –with-ssl-engine

* sshd(8): Use correct uid_t/pid_t types instead of int. bz#1817

* sshd(8): bz#1824: Add Solaris Project support.

* sshd(8): Check is_selinux_enabled for exact return code since it can apparently return -1 under some conditions.


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Editor in Chief at Debian-Tutorials, Linux enthusiast.

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