OpenSSH 5.7 released

OpenSSH is a 100% complete SSH protocol version 1.3, 1.5 and 2.0 implementation and includes sftp client and server support.

It encrypts all traffic (including passwords) to effectively eliminate eavesdropping, connection hijacking, and other attacks.

Features in OpenSSH 5.7:

  • 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” behavior 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.
  • 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).

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