Improve crypto ordering for Encrypt-then-MAC (EtM) mode
MAC algorithms.
Previously we were computing the MAC, decrypting the packet and then
checking the MAC. This gave rise to the possibility of creating a
side-channel oracle in the decryption step, though no such oracle has
been identified.
This adds a mac_check() function that computes and checks the MAC in
one pass, and uses it to advance MAC checking for EtM algorithms to
before payload decryption.
Reported by Jean Paul Degabriele, Kenny Paterson, Torben Hansen and
Martin Albrecht. feedback and ok markus@
Upstream-ID: 1999bb67cab47dda5b10b80d8155fe83d4a1867b
[cipher.c cipher.h kex.c kex.h mac.c mac.h servconf.c ssh.c]
Output the effective values of Ciphers, MACs and KexAlgorithms when
the default has not been overridden. ok markus@
[authfile.c cipher.c cipher.h kex.c kex.h kexecdh.c kexecdhc.c kexecdhs.c]
[key.c key.h mac.c mac.h packet.c ssh.1 ssh.c]
add the ability to query supported ciphers, MACs, key type and KEX
algorithms to ssh. Includes some refactoring of KEX and key type handling
to be table-driven; ok markus@
[kex.h mac.c mac.h monitor_wrap.c myproposal.h packet.c ssh.1]
[ssh_config.5 sshd.8 sshd_config.5]
Add a new MAC algorithm for data integrity, UMAC-64 (not default yet,
must specify umac-64@openssh.com). Provides about 20% end-to-end speedup
compared to hmac-md5. Represents a different approach to message
authentication to that of HMAC that may be beneficial if HMAC based on
one of its underlying hash algorithms is found to be vulnerable to a
new attack. http://www.ietf.org/rfc/rfc4418.txt
in conjunction with and OK djm@
[kex.c monitor_wrap.c packet.c mac.h kex.h mac.c]
Preserve MAC ctx between packets, saving 2xhash calls per-packet.
Yields around a 12-16% end-to-end speedup for arcfour256/hmac-md5
patch from markus@ tested dtucker@ and myself, ok markus@ and me (I'm
committing at his request)
[Makefile.in sshd.8 sshconnect2.c readconf.h readconf.c packet.c
sshd.c ssh.c ssh.1 servconf.h servconf.c myproposal.h kex.h kex.c]
1) clean up the MAC support for SSH-2
2) allow you to specify the MAC with 'ssh -m'
3) or the 'MACs' keyword in ssh(d)_config
4) add hmac-{md5,sha1}-96
ok stevesk@, provos@
