hmac-sha2-512 - Corrupted MAC on input with OpenSSH

[twisted-trac]

	@adiroiban reported
Trac ID	trac#8258
Type	defect
Created	2016-03-28 01:20:40Z

I have

$ ssh -V
OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.6, OpenSSL 1.0.1f 6 Jan 2014

Against the ./docs/conch/examples/sshsimpleserver.py example from trunk I run

$ sftp -P 5022 -vv -oKexAlgorithms=diffie-hellman-group14-sha1 -oMACs=hmac-sha2-512 user@localhost

debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
Corrupted MAC on input.
Disconnecting: Packet corrupt
Couldn't read packet: Connection reset by peer

Searchable metadata

trac-id__8258 8258
type__defect defect
reporter__adiroiban adiroiban
priority__normal normal
milestone__None None
branch__ 
branch_author__ 
status__closed closed
resolution__fixed fixed
component__conch conch
keywords__None None
time__1459128040926555 1459128040926555
changetime__1563643964847258 1563643964847258
version__None None
owner__hawkowl hawkowl
cc__z3p cc__twm

[twisted-trac]

	@adiroiban commented

I have tried with paramiko 1.16.0 and I got the same issue.

The initial key exchange part went fine, but it fails once I try to request a service.

[twisted-trac]

	@ryban set owner to @ryban @ryban set status to assigned

I've confirmed that adding more rounds to the hasher as described in the email thread (https://twistedmatrix.com/pipermail/twisted-python/2017-March/031336.html) and RFC4253 fixes the issue. Adding more bytes to the generated output won't affect existing algorithms since they consume as many bytes as they need from the beginning of the digest.

[twisted-trac]

	@ryban commented

PR: #1163

[twisted-trac]

	@hawkowl set owner to @hawkowl @hawkowl set status to new

LGTM!

[twisted-trac]

	Ryan Van Gilder set status to closed

In changeset 5b203b2

#!CommitTicketReference repository="" revision="5b203b267f9869f2bd6e3ed17dcdaafa1fa227d3"
Merge ryban:8258-ryban-hmac-sha2-512-fix: Fix SSH not generating correct keys when using hmac-sha2-512 with SHA1 based KEX algorithms

Author: ryban, jamohamm
Reviewer: hawkowl
Fixes: ticket:8258