Changes since OpenSSH 6.4
=========================

This is a feature-focused release.

New features:

 * ssh(1), sshd(8): Add support for key exchange using elliptic-curve
   Diffie Hellman in Daniel Bernstein's Curve25519. This key exchange
   method is the default when both the client and server support it.

 * ssh(1), sshd(8): Add support for Ed25519 as a public key type.
   Ed25519 is a elliptic curve signature scheme that offers
   better security than ECDSA and DSA and good performance. It may be
   used for both user and host keys.

 * Add a new private key format that uses a bcrypt KDF to better
   protect keys at rest. This format is used unconditionally for
   Ed25519 keys, but may be requested when generating or saving
   existing keys of other types via the -o ssh-keygen(1) option.
   We intend to make the new format the default in the near future.
   Details of the new format are in the PROTOCOL.key file.

 * ssh(1), sshd(8): Add a new transport cipher
   "[email protected]" that combines Daniel Bernstein's
   ChaCha20 stream cipher and Poly1305 MAC to build an authenticated
   encryption mode. Details are in the PROTOCOL.chacha20poly1305 file.

 * ssh(1), sshd(8): Refuse RSA keys from old proprietary clients and
   servers that use the obsolete RSA+MD5 signature scheme. It will
   still be possible to connect with these clients/servers but only
   DSA keys will be accepted, and OpenSSH will refuse connection
   entirely in a future release.

 * ssh(1), sshd(8): Refuse old proprietary clients and servers that
   use a weaker key exchange hash calculation.

 * ssh(1): Increase the size of the Diffie-Hellman groups requested
   for each symmetric key size. New values from NIST Special
   Publication 800-57 with the upper limit specified by RFC4419.

 * ssh(1), ssh-agent(1): Support PKCS#11 tokens that only provide
   X.509 certs instead of raw public keys (requested as bz#1908).

 * ssh(1): Add a ssh_config(5) "Match" keyword that allows
   conditional configuration to be applied by matching on hostname,
   user and result of arbitrary commands.

 * ssh(1): Add support for client-side hostname canonicalisation
   using a set of DNS suffixes and rules in ssh_config(5). This
   allows unqualified names to be canonicalised to fully-qualified
   domain names to eliminate ambiguity when looking up keys in
   known_hosts or checking host certificate names.

 * sftp-server(8): Add the ability to whitelist and/or blacklist sftp
   protocol requests by name.

 * sftp-server(8): Add a sftp "[email protected]" to support calling
   fsync(2) on an open file handle.

 * sshd(8): Add a ssh_config(5) PermitTTY to disallow TTY allocation,
   mirroring the longstanding no-pty authorized_keys option.

 * ssh(1): Add a ssh_config ProxyUseFDPass option that supports the
   use of ProxyCommands that establish a connection and then pass a
   connected file descriptor back to ssh(1). This allows the
   ProxyCommand to exit rather than staying around to transfer data.

Bugfixes:

 * ssh(1), sshd(8): Fix potential stack exhaustion caused by nested
   certificates.

 * ssh(1): bz#1211: make BindAddress work with UsePrivilegedPort.

 * sftp(1): bz#2137: fix the progress meter for resumed transfer.

 * ssh-add(1): bz#2187: do not request smartcard PIN when removing
   keys from ssh-agent.

 * sshd(8): bz#2139: fix re-exec fallback when original sshd binary
   cannot be executed.

 * ssh-keygen(1): Make relative-specified certificate expiry times
   relative to current time and not the validity start time.

 * sshd(8): bz#2161: fix AuthorizedKeysCommand inside a Match block.

 * sftp(1): bz#2129: symlinking a file would incorrectly canonicalise
   the target path.

 * ssh-agent(1): bz#2175: fix a use-after-free in the PKCS#11 agent
   helper executable.

 * sshd(8): Improve logging of sessions to include the user name,
   remote host and port, the session type (shell, command, etc.) and
   allocated TTY (if any).

 * sshd(8): bz#1297: tell the client (via a debug message) when
   their preferred listen address has been overridden by the
   server's GatewayPorts setting.

 * sshd(8): bz#2162: include report port in bad protocol banner
   message.

 * sftp(1): bz#2163: fix memory leak in error path in do_readdir().

 * sftp(1): bz#2171: don't leak file descriptor on error.

 * sshd(8): Include the local address and port in "Connection from
   ..." message (only shown at loglevel>=verbose).

Portable OpenSSH:

 * Please note that this is the last version of Portable OpenSSH that
   will support versions of OpenSSL prior to 0.9.6. Support (i.e.
   SSH_OLD_EVP) will be removed following the 6.5p1 release.

 * Portable OpenSSH will attempt compile and link as a Position
   Independent Executable on Linux, OS X and OpenBSD on recent gcc-
   like compilers. Other platforms and older/other compilers may
   request this using the --with-pie configure flag.

 * A number of other toolchain-related hardening options are used
   automatically if available, including -ftrapv to abort on signed
   integer overflow and options to write-protect dynamic linking
   information.  The use of these options may be disabled using the
   --without-hardening configure flag.

 * If the toolchain supports it, one of the -fstack-protector-strong,
   -fstack-protector-all or -fstack-protector compilation flag are
   used to add guards to mitigate attacks based on stack overflows.
   The use of these options may be disabled using the
   --without-stackprotect configure option.

 * sshd(8): Add support for pre-authentication sandboxing using the
   Capsicum API introduced in FreeBSD 10.

 * Switch to a ChaCha20-based arc4random() PRNG for platforms that do
   not provide their own.

 * sshd(8): bz#2156: restore Linux oom_adj setting when handling
   SIGHUP to maintain behaviour over retart.

 * sshd(8): bz#2032: use local username in krb5_kuserok check rather
   than full client name which may be of form user@REALM.

 * ssh(1), sshd(8): Test for both the presence of ECC NID numbers in
   OpenSSL and that they actually work. Fedora (at least) has
   NID_secp521r1 that doesn't work.

 * bz#2173: use pkg-config --libs to include correct -L location for
   libedit.