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ESB-2016.0605 - [Win][UNIX/Linux] OpenSSH: Access privileged data - Remote/unauthenticated

Date: 08 March 2016

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Click here for PGP verifiable version
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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                               ESB-2016.0605
    Multiple vulnerabilities identified in OpenSSH prior to version 7.2
                               8 March 2016

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           OpenSSH
Publisher:         OpenSSH
Operating System:  Windows
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Access Privileged Data         -- Remote/Unauthenticated
                   Provide Misleading Information -- Remote/Unauthenticated
                   Unauthorised Access            -- Remote/Unauthenticated
                   Reduced Security               -- Remote/Unauthenticated
Resolution:        Patch/Upgrade

Original Bulletin: 
   http://www.openssh.com/txt/release-7.2

- --------------------------BEGIN INCLUDED TEXT--------------------

OpenSSH 7.2 has just been released. It will be available from the
mirrors listed at http://www.openssh.com/ shortly.

OpenSSH is a 100% complete SSH protocol 2.0 implementation and
includes sftp client and server support. OpenSSH also includes
transitional support for the legacy SSH 1.3 and 1.5 protocols
that may be enabled at compile-time.

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:
http://www.openssh.com/donations.html

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

We plan on retiring more legacy cryptography in a near-future
release, specifically:

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

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

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

This release disables a number of legacy cryptographic algorithms
by default in ssh:

 * Several ciphers blowfish-cbc, cast128-cbc, all arcfour variants
   and the rijndael-cbc aliases for AES.

 * MD5-based and truncated HMAC algorithms.

These algorithms are already disabled by default in sshd.

Changes since OpenSSH 7.1p2
===========================

This is primarily a bugfix release.

Security
- --------

 * ssh(1), sshd(8): remove unfinished and unused roaming code (was
   already forcibly disabled in OpenSSH 7.1p2).
 
 * ssh(1): eliminate fallback from untrusted X11 forwarding to
   trusted forwarding when the X server disables the SECURITY
   extension.

 * ssh(1), sshd(8): increase the minimum modulus size supported for
   diffie-hellman-group-exchange to 2048 bits.

 * sshd(8): pre-auth sandboxing is now enabled by default (previous
   releases enabled it for new installations via sshd_config).

New Features
- ------------

 * all: add support for RSA signatures using SHA-256/512 hash
   algorithms based on draft-rsa-dsa-sha2-256-03.txt and
   draft-ssh-ext-info-04.txt.

 * ssh(1): Add an AddKeysToAgent client option which can be set to
   'yes', 'no', 'ask', or 'confirm', and defaults to 'no'.  When
   enabled, a private key that is used during authentication will be
   added to ssh-agent if it is running (with confirmation enabled if
   set to 'confirm').
 
 * sshd(8): add a new authorized_keys option "restrict" that includes
   all current and future key restrictions (no-*-forwarding, etc.).
   Also add permissive versions of the existing restrictions, e.g.
   "no-pty" -> "pty". This simplifies the task of setting up
   restricted keys and ensures they are maximally-restricted,
   regardless of any permissions we might implement in the future.
    
 * ssh(1): add ssh_config CertificateFile option to explicitly list
   certificates. bz#2436
 
 * ssh-keygen(1): allow ssh-keygen to change the key comment for all
   supported formats.

 * ssh-keygen(1): allow fingerprinting from standard input, e.g.
   "ssh-keygen -lf -"

 * ssh-keygen(1): allow fingerprinting multiple public keys in a
   file, e.g. "ssh-keygen -lf ~/.ssh/authorized_keys" bz#1319

 * sshd(8): support "none" as an argument for sshd_config
   Foreground and ChrootDirectory. Useful inside Match blocks to
   override a global default. bz#2486

 * ssh-keygen(1): support multiple certificates (one per line) and
   reading from standard input (using "-f -") for "ssh-keygen -L"
    
 * ssh-keyscan(1): add "ssh-keyscan -c ..." flag to allow fetching
   certificates instead of plain keys.
 
 * ssh(1): better handle anchored FQDNs (e.g. 'cvs.openbsd.org.') in
   hostname canonicalisation - treat them as already canonical and
   remove the trailing '.' before matching ssh_config.

Bugfixes
- --------

 * sftp(1): existing destination directories should not terminate
   recursive uploads (regression in openssh 6.8) bz#2528

 * ssh(1), sshd(8): correctly send back SSH2_MSG_UNIMPLEMENTED
   replies to unexpected messages during key exchange. bz#2949

 * ssh(1): refuse attempts to set ConnectionAttempts=0, which does
   not make sense and would cause ssh to print an uninitialised stack
   variable. bz#2500

 * ssh(1): fix errors when attempting to connect to scoped IPv6
   addresses with hostname canonicalisation enabled.

 * sshd_config(5): list a couple more options usable in Match blocks.
   bz#2489

 * sshd(8): fix "PubkeyAcceptedKeyTypes +..." inside a Match block.
    
 * ssh(1): expand tilde characters in filenames passed to -i options
   before checking whether or not the identity file exists. Avoids
   confusion for cases where shell doesn't expand (e.g. "-i ~/file"
   vs. "-i~/file"). bz#2481

 * ssh(1): do not prepend "exec" to the shell command run by "Match
   exec" in a config file, which could cause some commands to fail
   in certain environments. bz#2471

 * ssh-keyscan(1): fix output for multiple hosts/addrs on one line
   when host hashing or a non standard port is in use bz#2479
 
 * sshd(8): skip "Could not chdir to home directory" message when
   ChrootDirectory is active. bz#2485

 * ssh(1): include PubkeyAcceptedKeyTypes in ssh -G config dump.
    
 * sshd(8): avoid changing TunnelForwarding device flags if they are
   already what is needed; makes it possible to use tun/tap
   networking as non-root user if device permissions and interface
   flags are pre-established

 * ssh(1), sshd(8): RekeyLimits could be exceeded by one packet.
   bz#2521

 * ssh(1): fix multiplexing master failure to notice client exit.

 * ssh(1), ssh-agent(1): avoid fatal() for PKCS11 tokens that present
   empty key IDs. bz#1773

 * sshd(8): avoid printf of NULL argument. bz#2535  

 * ssh(1), sshd(8): allow RekeyLimits larger than 4GB. bz#2521
 
 * ssh-keygen(1): sshd(8): fix several bugs in (unused) KRL signature
   support.

 * ssh(1), sshd(8): fix connections with peers that use the key
   exchange guess feature of the protocol. bz#2515

 * sshd(8): include remote port number in log messages. bz#2503

 * ssh(1): don't try to load SSHv1 private key when compiled without
   SSHv1 support. bz#2505

 * ssh-agent(1), ssh(1): fix incorrect error messages during key
   loading and signing errors. bz#2507

 * ssh-keygen(1): don't leave empty temporary files when performing
   known_hosts file edits when known_hosts doesn't exist.

 * sshd(8): correct packet format for tcpip-forward replies for
   requests that don't allocate a port bz#2509

 * ssh(1), sshd(8): fix possible hang on closed output. bz#2469
    
 * ssh(1): expand %i in ControlPath to UID. bz#2449

 * ssh(1), sshd(8): fix return type of openssh_RSA_verify. bz#2460
 
 * ssh(1), sshd(8): fix some option parsing memory leaks. bz#2182

 * ssh(1): add a some debug output before DNS resolution; it's a
   place where ssh could previously silently stall in cases of
   unresponsive DNS servers. bz#2433
    
 * ssh(1): remove spurious newline in visual hostkey. bz#2686
 
 * ssh(1): fix printing (ssh -G ...) of HostKeyAlgorithms=+...
 
 * ssh(1): fix expansion of HostkeyAlgorithms=+...

Documentation
- -------------

 * ssh_config(5), sshd_config(5): update default algorithm lists to
   match current reality. bz#2527

 * ssh(1): mention -Q key-plain and -Q key-cert query options.
   bz#2455

 * sshd_config(8): more clearly describe what AuthorizedKeysFile=none
   does.

 * ssh_config(5): better document ExitOnForwardFailure. bz#2444  

 * sshd(5): mention internal DH-GEX fallback groups in manual.
   bz#2302

 * sshd_config(5): better description for MaxSessions option.
   bz#2531

Portability
- -----------

 * ssh(1), sftp-server(8), ssh-agent(1), sshd(8): Support Illumos/
   Solaris fine-grained privileges. Including a pre-auth privsep
   sandbox and several pledge() emulations. bz#2511

 * Renovate redhat/openssh.spec, removing deprecated options and
   syntax.

 * configure: allow --without-ssl-engine with --without-openssl
 
 * sshd(8): fix multiple authentication using S/Key. bz#2502

 * sshd(8): read back from libcrypto RAND_* before dropping
   privileges.  Avoids sandboxing violations with BoringSSL.

 * Fix name collision with system-provided glob(3) functions.
   bz#2463

 * Adapt Makefile to use ssh-keygen -A when generating host keys.
   bz#2459
 
 * configure: correct default value for --with-ssh1 bz#2457

 * configure: better detection of _res symbol bz#2259

 * support getrandom() syscall on Linux

Checksums:
==========

 - SHA1 (openssh-7.2.tar.gz) = 9567d00fffe655010c087aeb80c830cecbbecca6
 - SHA256 (openssh-7.2.tar.gz) = 99GsHA8NwSGuEJhMc7hAOQ510y1xfGx27uJqyw73sCI=

 - SHA1 (openssh-7.2p1.tar.gz) = d30a6fd472199ab5838a7668c0c5fd885fb8d371
 - SHA256 (openssh-7.2p1.tar.gz) = lzzDey81l+TPWZsJ5gTnnA/l2bb1laJOke0GYoYLSsM=

Please note that the SHA256 signatures are base64 encoded and not
hexadecimal (which is the default for most checksum tools). The PGP
key used to sign the releases is available as RELEASE_KEY.asc from
the mirror sites.

Reporting Bugs:
===============

- - Please read http://www.openssh.com/report.html
  Security bugs should be reported directly to openssh@openssh.com

OpenSSH is brought to you by Markus Friedl, Niels Provos, Theo de
Raadt, Kevin Steves, Damien Miller, Darren Tucker, Jason McIntyre,
Tim Rice and Ben Lindstrom.

- --------------------------END INCLUDED TEXT--------------------

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===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
===========================================================================
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