Changes since OpenSSH 6.9
=========================
This focus of this release is primarily to deprecate weak, legacy
and/or unsafe cryptography.
Security
--------
* sshd(8): OpenSSH 6.8 and 6.9 incorrectly set TTYs to be world-
writable. Local attackers may be able to write arbitrary messages
to logged-in users, including terminal escape sequences.
Reported by Nikolay Edigaryev.
* sshd(8): Portable OpenSSH only: Fixed a privilege separation
weakness related to PAM support. Attackers who could successfully
compromise the pre-authentication process for remote code
execution and who had valid credentials on the host could
impersonate other users. Reported by Moritz Jodeit.
* sshd(8): Portable OpenSSH only: Fixed a use-after-free bug
related to PAM support that was reachable by attackers who could
compromise the pre-authentication process for remote code
execution. Also reported by Moritz Jodeit.
* sshd(8): fix circumvention of MaxAuthTries using keyboard-
interactive authentication. By specifying a long, repeating
keyboard-interactive "devices" string, an attacker could request
the same authentication method be tried thousands of times in
a single pass. The LoginGraceTime timeout in sshd(8) and any
authentication failure delays implemented by the authentication
mechanism itself were still applied. Found by Kingcope.
Potentially-incompatible Changes
--------------------------------
* Support for the legacy SSH version 1 protocol is disabled by
default at compile time.
* Support for the 1024-bit diffie-hellman-group1-sha1 key exchange
is disabled by default at run-time. It may be re-enabled using
the instructions at http://www.openssh.com/legacy.html
* Support for ssh-dss, ssh-dss-cert-* host and user keys is disabled
by default at run-time. These may be re-enabled using the
instructions at http://www.openssh.com/legacy.html
* Support for the legacy v00 cert format has been removed.
* The default for the sshd_config(5) PermitRootLogin option has
changed from "yes" to "prohibit-password".
* PermitRootLogin=without-password/prohibit-password now bans all
interactive authentication methods, allowing only public-key,
hostbased and GSSAPI authentication (previously it permitted
keyboard-interactive and password-less authentication if those
were enabled).
New Features
------------
* ssh_config(5): add PubkeyAcceptedKeyTypes option to control which
public key types are available for user authentication.
* sshd_config(5): add HostKeyAlgorithms option to control which
public key types are offered for host authentications.
* ssh(1), sshd(8): extend Ciphers, MACs, KexAlgorithms,
HostKeyAlgorithms, PubkeyAcceptedKeyTypes and HostbasedKeyTypes
options to allow appending to the default set of algorithms
instead of replacing it. Options may now be prefixed with a '+'
to append to the default, e.g. "HostKeyAlgorithms=+ssh-dss".
* sshd_config(5): PermitRootLogin now accepts an argument of
'prohibit-password' as a less-ambiguous synonym of 'without-
password'.
Bugfixes
--------
* ssh(1), sshd(8): add compatability workarounds for Cisco and more
PuTTY versions. bz#2424
* Fix some omissions and errors in the PROTOCOL and PROTOCOL.mux
documentation relating to Unix domain socket forwarding;
bz#2421 bz#2422
* ssh(1): Improve the ssh(1) manual page to include a better
description of Unix domain socket forwarding; bz#2423
* ssh(1), ssh-agent(1): skip uninitialised PKCS#11 slots, fixing
failures to load keys when they are present. bz#2427
* ssh(1), ssh-agent(1): do not ignore PKCS#11 hosted keys that wth
empty CKA_ID; bz#2429
* sshd(8): clarify documentation for UseDNS option; bz#2045
the support in the rest of the source tree.
X11 sets could use some cleaning up perhaps (just deletion, as
we've never really marked the old X11R6 as obsolete for native
xorg using platforms so far either.)
*) Alternate chains certificate forgery
During certificate verfification, OpenSSL will attempt to find an
alternative certificate chain if the first attempt to build such a chain
fails. An error in the implementation of this logic can mean that an
attacker could cause certain checks on untrusted certificates to be
bypassed, such as the CA flag, enabling them to use a valid leaf
certificate to act as a CA and "issue" an invalid certificate.
This issue was reported to OpenSSL by Adam Langley/David Benjamin
(Google/BoringSSL).
[Matt Caswell]
=========================
This is primarily a bugfix release.
Security
--------
* ssh(1): when forwarding X11 connections with ForwardX11Trusted=no,
connections made after ForwardX11Timeout expired could be permitted
and no longer subject to XSECURITY restrictions because of an
ineffective timeout check in ssh(1) coupled with "fail open"
behaviour in the X11 server when clients attempted connections with
expired credentials. This problem was reported by Jann Horn.
* ssh-agent(1): fix weakness of agent locking (ssh-add -x) to
password guessing by implementing an increasing failure delay,
storing a salted hash of the password rather than the password
itself and using a timing-safe comparison function for verifying
unlock attempts. This problem was reported by Ryan Castellucci.
New Features
------------
* ssh(1), sshd(8): promote chacha20-poly1305@openssh.com to be the
default cipher
* sshd(8): support admin-specified arguments to AuthorizedKeysCommand;
bz#2081
* sshd(8): add AuthorizedPrincipalsCommand that allows retrieving
authorized principals information from a subprocess rather than
a file.
* ssh(1), ssh-add(1): support PKCS#11 devices with external PIN
entry devices bz#2240
* sshd(8): allow GSSAPI host credential check to be relaxed for
multihomed hosts via GSSAPIStrictAcceptorCheck option; bz#928
* ssh-keygen(1): support "ssh-keygen -lF hostname" to search
known_hosts and print key hashes rather than full keys.
* ssh-agent(1): add -D flag to leave ssh-agent in foreground without
enabling debug mode; bz#2381
Bugfixes
--------
* ssh(1), sshd(8): deprecate legacy SSH2_MSG_KEX_DH_GEX_REQUEST_OLD
message and do not try to use it against some 3rd-party SSH
implementations that use it (older PuTTY, WinSCP).
* Many fixes for problems caused by compile-time deactivation of
SSH1 support (including bz#2369)
* ssh(1), sshd(8): cap DH-GEX group size at 4Kbits for Cisco
implementations as some would fail when attempting to use group
sizes >4K; bz#2209
* ssh(1): fix out-of-bound read in EscapeChar configuration option
parsing; bz#2396
* sshd(8): fix application of PermitTunnel, LoginGraceTime,
AuthenticationMethods and StreamLocalBindMask options in Match
blocks
* ssh(1), sshd(8): improve disconnection message on TCP reset;
bz#2257
* ssh(1): remove failed remote forwards established by muliplexing
from the list of active forwards; bz#2363
* sshd(8): make parsing of authorized_keys "environment=" options
independent of PermitUserEnv being enabled; bz#2329
* sshd(8): fix post-auth crash with permitopen=none; bz#2355
* ssh(1), ssh-add(1), ssh-keygen(1): allow new-format private keys
to be encrypted with AEAD ciphers; bz#2366
* ssh(1): allow ListenAddress, Port and AddressFamily configuration
options to appear in any order; bz#86
* sshd(8): check for and reject missing arguments for VersionAddendum
and ForceCommand; bz#2281
* ssh(1), sshd(8): don't treat unknown certificate extensions as
fatal; bz#2387
* ssh-keygen(1): make stdout and stderr output consistent; bz#2325
* ssh(1): mention missing DISPLAY environment in debug log when X11
forwarding requested; bz#1682
* sshd(8): correctly record login when UseLogin is set; bz#378
* sshd(8): Add some missing options to sshd -T output and fix output
of VersionAddendum and HostCertificate. bz#2346
* Document and improve consistency of options that accept a "none"
argument" TrustedUserCAKeys, RevokedKeys (bz#2382),
AuthorizedPrincipalsFile (bz#2288)
* ssh(1): include remote username in debug output; bz#2368
* sshd(8): avoid compatibility problem with some versions of Tera
Term, which would crash when they received the hostkeys notification
message (hostkeys-00@openssh.com)
* sshd(8): mention ssh-keygen -E as useful when comparing legacy MD5
host key fingerprints; bz#2332
* ssh(1): clarify pseudo-terminal request behaviour and use make
manual language consistent; bz#1716
* ssh(1): document that the TERM environment variable is not subject
to SendEnv and AcceptEnv; bz#2386
*) Malformed ECParameters causes infinite loop
When processing an ECParameters structure OpenSSL enters an infinite loop
if the curve specified is over a specially malformed binary polynomial
field.
This can be used to perform denial of service against any
system which processes public keys, certificate requests or
certificates. This includes TLS clients and TLS servers with
client authentication enabled.
This issue was reported to OpenSSL by Joseph Barr-Pixton.
(CVE-2015-1788)
[Andy Polyakov]
*) Exploitable out-of-bounds read in X509_cmp_time
X509_cmp_time does not properly check the length of the ASN1_TIME
string and can read a few bytes out of bounds. In addition,
X509_cmp_time accepts an arbitrary number of fractional seconds in the
time string.
An attacker can use this to craft malformed certificates and CRLs of
various sizes and potentially cause a segmentation fault, resulting in
a DoS on applications that verify certificates or CRLs. TLS clients
that verify CRLs are affected. TLS clients and servers with client
authentication enabled may be affected if they use custom verification
callbacks.
This issue was reported to OpenSSL by Robert Swiecki (Google), and
independently by Hanno Böck.
(CVE-2015-1789)
[Emilia Käsper]
*) PKCS7 crash with missing EnvelopedContent
The PKCS#7 parsing code does not handle missing inner EncryptedContent
correctly. An attacker can craft malformed ASN.1-encoded PKCS#7 blobs
with missing content and trigger a NULL pointer dereference on parsing.
Applications that decrypt PKCS#7 data or otherwise parse PKCS#7
structures from untrusted sources are affected. OpenSSL clients and
servers are not affected.
This issue was reported to OpenSSL by Michal Zalewski (Google).
(CVE-2015-1790)
[Emilia Käsper]
*) CMS verify infinite loop with unknown hash function
When verifying a signedData message the CMS code can enter an infinite loop
if presented with an unknown hash function OID. This can be used to perform
denial of service against any system which verifies signedData messages using
the CMS code.
This issue was reported to OpenSSL by Johannes Bauer.
(CVE-2015-1792)
[Stephen Henson]
*) Race condition handling NewSessionTicket
If a NewSessionTicket is received by a multi-threaded client when attempting to
reuse a previous ticket then a race condition can occur potentially leading to
a double free of the ticket data.
(CVE-2015-1791)
[Matt Caswell]
*) Reject DH handshakes with parameters shorter than 768 bits.
[Kurt Roeckx and Emilia Kasper]
=========================
This is a major release, containing a number of new features as
well as a large internal re-factoring.
Potentially-incompatible changes
--------------------------------
* sshd(8): UseDNS now defaults to 'no'. Configurations that match
against the client host name (via sshd_config or authorized_keys)
may need to re-enable it or convert to matching against addresses.
New Features
------------
* Much of OpenSSH's internal code has been re-factored to be more
library-like. These changes are mostly not user-visible, but
have greatly improved OpenSSH's testability and internal layout.
* Add FingerprintHash option to ssh(1) and sshd(8), and equivalent
command-line flags to the other tools to control algorithm used
for key fingerprints. The default changes from MD5 to SHA256 and
format from hex to base64.
Fingerprints now have the hash algorithm prepended. An example of
the new format: SHA256:mVPwvezndPv/ARoIadVY98vAC0g+P/5633yTC4d/wXE
Please note that visual host keys will also be different.
* ssh(1), sshd(8): Experimental host key rotation support. Add a
protocol extension for a server to inform a client of all its
available host keys after authentication has completed. The client
may record the keys in known_hosts, allowing it to upgrade to better
host key algorithms and a server to gracefully rotate its keys.
The client side of this is controlled by a UpdateHostkeys config
option (default off).
* ssh(1): Add a ssh_config HostbasedKeyType option to control which
host public key types are tried during host-based authentication.
* ssh(1), sshd(8): fix connection-killing host key mismatch errors
when sshd offers multiple ECDSA keys of different lengths.
* ssh(1): when host name canonicalisation is enabled, try to
parse host names as addresses before looking them up for
canonicalisation. fixes bz#2074 and avoiding needless DNS
lookups in some cases.
* ssh-keygen(1), sshd(8): Key Revocation Lists (KRLs) no longer
require OpenSSH to be compiled with OpenSSL support.
* ssh(1), ssh-keysign(8): Make ed25519 keys work for host based
authentication.
* sshd(8): SSH protocol v.1 workaround for the Meyer, et al,
Bleichenbacher Side Channel Attack. Fake up a bignum key before
RSA decryption.
* sshd(8): Remember which public keys have been used for
authentication and refuse to accept previously-used keys.
This allows AuthenticationMethods=publickey,publickey to require
that users authenticate using two _different_ public keys.
* sshd(8): add sshd_config HostbasedAcceptedKeyTypes and
PubkeyAcceptedKeyTypes options to allow sshd to control what
public key types will be accepted. Currently defaults to all.
* sshd(8): Don't count partial authentication success as a failure
against MaxAuthTries.
* ssh(1): Add RevokedHostKeys option for the client to allow
text-file or KRL-based revocation of host keys.
* ssh-keygen(1), sshd(8): Permit KRLs that revoke certificates by
serial number or key ID without scoping to a particular CA.
* ssh(1): Add a "Match canonical" criteria that allows ssh_config
Match blocks to trigger only in the second config pass.
* ssh(1): Add a -G option to ssh that causes it to parse its
configuration and dump the result to stdout, similar to "sshd -T".
* ssh(1): Allow Match criteria to be negated. E.g. "Match !host".
* The regression test suite has been extended to cover more OpenSSH
features. The unit tests have been expanded and now cover key
exchange.
Bugfixes
* ssh-keyscan(1): ssh-keyscan has been made much more robust again
servers that hang or violate the SSH protocol.
* ssh(1), ssh-keygen(1): Fix regression bz#2306: Key path names were
being lost as comment fields.
* ssh(1): Allow ssh_config Port options set in the second config
parse phase to be applied (they were being ignored). bz#2286
* ssh(1): Tweak config re-parsing with host canonicalisation - make
the second pass through the config files always run when host name
canonicalisation is enabled (and not whenever the host name
changes) bz#2267
* ssh(1): Fix passing of wildcard forward bind addresses when
connection multiplexing is in use; bz#2324;
* ssh-keygen(1): Fix broken private key conversion from non-OpenSSH
formats; bz#2345.
* ssh-keygen(1): Fix KRL generation bug when multiple CAs are in
use.
* Various fixes to manual pages: bz#2288, bz#2316, bz#2273
Portable OpenSSH
* Support --without-openssl at configure time
Disables and removes dependency on OpenSSL. Many features,
including SSH protocol 1 are not supported and the set of crypto
options is greatly restricted. This will only work on systems
with native arc4random or /dev/urandom.
Considered highly experimental for now.
* Support --without-ssh1 option at configure time
Allows disabling support for SSH protocol 1.
* sshd(8): Fix compilation on systems with IPv6 support in utmpx; bz#2296
* Allow custom service name for sshd on Cygwin. Permits the use of
multiple sshd running with different service names.
Checksums:
==========
- SHA1 (openssh-6.8.tar.gz) = 99903c6ca76e0a2c044711017f81127e12459d37
- SHA256 (openssh-6.8.tar.gz) = N1uzVarFbrm2CzAwuDu3sRoszmqpK+5phAChP/QNyuw=
- SHA1 (openssh-6.8p1.tar.gz) = cdbc51e46a902b30d263b05fdc71340920e91c92
- SHA256 (openssh-6.8p1.tar.gz) = P/ZM5z7hJEgLW/dnuYMNfTwDu8tqvnFrePAZLDfOFg4=
Please note that the PGP key used to sign releases was recently rotated.
The new key has been signed by the old key to provide continuity. It is
available from the mirror sites as RELEASE_KEY.asc.
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
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