Log Message:
Update openssh to 7.4.1 (7.4p1), including security fixes.

For full changes, please refer ChangeLog file.

Future deprecation notice
=========================

We plan on retiring more legacy cryptography in future releases,
specifically:

 * In approximately August 2017, removing remaining support for the
   SSH v.1 protocol (client-only and currently compile-time disabled).

 * In the same release, removing support for Blowfish and RC4 ciphers
   and the RIPE-MD160 HMAC. (These are currently run-time disabled).

 * Refusing all RSA keys smaller than 1024 bits (the current minimum
   is 768 bits)

 * The next release of OpenSSH will remove support for running sshd(8)
   with privilege separation disabled.

 * The next release of portable OpenSSH will remove support for
   OpenSSL version prior to 1.0.1.

This list reflects our current intentions, but please check the final
release notes for future releases.

Potentially-incompatible changes
================================

This release includes a number of changes that may affect existing
configurations:

 * This release removes server support for the SSH v.1 protocol.

 * ssh(1): Remove 3des-cbc from the client's default proposal. 64-bit
   block ciphers are not safe in 2016 and we don't want to wait until
   attacks like SWEET32 are extended to SSH. As 3des-cbc was the
   only mandatory cipher in the SSH RFCs, this may cause problems
   connecting to older devices using the default configuration,
   but it's highly likely that such devices already need explicit
   configuration for key exchange and hostkey algorithms already
   anyway.

 * sshd(8): Remove support for pre-authentication compression.
   Doing compression early in the protocol probably seemed reasonable
   in the 1990s, but today it's clearly a bad idea in terms of both
   cryptography (cf. multiple compression oracle attacks in TLS) and
   attack surface. Pre-auth compression support has been disabled by
   default for >10 years. Support remains in the client.

 * ssh-agent will refuse to load PKCS#11 modules outside a whitelist
   of trusted paths by default. The path whitelist may be specified
   at run-time.

 * sshd(8): When a forced-command appears in both a certificate and
   an authorized keys/principals command= restriction, sshd will now
   refuse to accept the certificate unless they are identical.
   The previous (documented) behaviour of having the certificate
   forced-command override the other could be a bit confusing and
   error-prone.

 * sshd(8): Remove the UseLogin configuration directive and support
   for having /bin/login manage login sessions.

Changes since OpenSSH 7.3
=========================

This is primarily a bugfix release.

Security
--------

 * ssh-agent(1): Will now refuse to load PKCS#11 modules from paths
   outside a trusted whitelist (run-time configurable). Requests to
   load modules could be passed via agent forwarding and an attacker
   could attempt to load a hostile PKCS#11 module across the forwarded
   agent channel: PKCS#11 modules are shared libraries, so this would
   result in code execution on the system running the ssh-agent if the
   attacker has control of the forwarded agent-socket (on the host
   running the sshd server) and the ability to write to the filesystem
   of the host running ssh-agent (usually the host running the ssh
   client). Reported by Jann Horn of Project Zero.

 * sshd(8): When privilege separation is disabled, forwarded Unix-
   domain sockets would be created by sshd(8) with the privileges of
   'root' instead of the authenticated user. This release refuses
   Unix-domain socket forwarding when privilege separation is disabled
   (Privilege separation has been enabled by default for 14 years).
   Reported by Jann Horn of Project Zero.

 * sshd(8): Avoid theoretical leak of host private key material to
   privilege-separated child processes via realloc() when reading
   keys. No such leak was observed in practice for normal-sized keys,
   nor does a leak to the child processes directly expose key material
   to unprivileged users. Reported by Jann Horn of Project Zero.

 * sshd(8): The shared memory manager used by pre-authentication
   compression support had a bounds checks that could be elided by
   some optimising compilers. Additionally, this memory manager was
   incorrectly accessible when pre-authentication compression was
   disabled. This could potentially allow attacks against the
   privileged monitor process from the sandboxed privilege-separation
   process (a compromise of the latter would be required first).
   This release removes support for pre-authentication compression
   from sshd(8). Reported by Guido Vranken using the Stack unstable
   optimisation identification tool (http://css.csail.mit.edu/stack/)

 * sshd(8): Fix denial-of-service condition where an attacker who
   sends multiple KEXINIT messages may consume up to 128MB per
   connection. Reported by Shi Lei of Gear Team, Qihoo 360.

 * sshd(8): Validate address ranges for AllowUser and DenyUsers
   directives at configuration load time and refuse to accept invalid
   ones. It was previously possible to specify invalid CIDR address
   ranges (e.g. user@127.1.2.3/55) and these would always match,
   possibly resulting in granting access where it was not intended.
   Reported by Laurence Parry.