Bug 1326073

Summary: GnuTLS prefers SHA-1 signatures in TLSv1.2
Product: Red Hat Enterprise Linux 6 Reporter: Alicja Kario <hkario>
Component: gnutlsAssignee: Nikos Mavrogiannopoulos <nmavrogi>
Status: CLOSED ERRATA QA Contact: Alicja Kario <hkario>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.8CC: nmavrogi, szidek
Target Milestone: rcKeywords: Rebase
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: gnutls-2.12.23-12.el6 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2017-03-21 09:03:16 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1339222, 1343211    

Description Alicja Kario 2016-04-11 18:05:53 UTC 
Description of problem:
When a GnuTLS client uses TLSv1.2, servers which respect client preference for signature methods will select SHA-1 signature for Server Key Exchange message.

Version-Release number of selected component (if applicable):
gnutls-2.8.5-19.el6_7.x86_64

How reproducible:
Always

Steps to Reproduce:
1. tcpdump -i any -s 0 -w capture.pcap -u port 443
2. gnutls-cli --port 443 --priority NORMAL:+VERS-TLS1.2 bugzilla.redhat.com
3. open capture.pcap in wireshark

Actual results:
Client Hello message contains signautre_alorithms extension with following pairs:
SHA1-RSA
SHA1-DSA
SHA256-RSA
SHA384-RSA
SHA512-RSA

The Server Key Exchange message is signed with SHA1-RSA

Expected results:
Extension containing the signature algorithms in following order:
SHA256-RSA
SHA384-RSA
SHA512-RSA
SHA1-RSA
SHA1-DSA

Server Key Exchange signed with SHA256-RSA

Additional info:
This should also affect server side, at the very least when the %SERVER_PRECEDENCE setting is used.
Comment 2 Nikos Mavrogiannopoulos 2016-08-09 12:20:53 UTC 
Verified that this is addressed by the 2.12.x rebase.
Comment 13 errata-xmlrpc 2017-03-21 09:03:16 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHSA-2017-0574.html