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Bug 1326389

Summary: GnuTLS server does not accept SHA-384 and SHA-512 Certificate Verify signatures despite advertising support for them
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: szidek
Target Milestone: rcKeywords: Rebase, Reopened
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: gnutls-2.12.23-1.el6 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2017-03-21 09:03:24 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    
Attachments:
Description Flags
packet capture for connections with different signatures none

Description Alicja Kario 2016-04-12 14:58:41 UTC 
Created attachment 1146506 [details]
packet capture for connections with different signatures

Description of problem:
When using GnuTLS server with client certificates and a client that prefers strong hashes like SHA-512 or SHA-384 will be rejected by server, even though the server advertises support for SHA-384 and SHA-512 in Certificate Request.

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

How reproducible:
always

Steps to Reproduce:
1. start gnutls server with client certificates
2. connect to it with restrictive client
3.

Actual results:
Alert(fatal, handshake_failure)

Expected results:
successful connection

Additional info:
Comment 1 Alicja Kario 2016-04-12 17:27:28 UTC 
Steps to Reproduce:
1. git clone https://github.com/tomato42/tlsfuzzer.git
2. pushd tlsfuzzer
3. git clone https://github.com/warner/python-ecdsa .python-ecdsa
4. ln -s .python-ecdsa/ecdsa ecdsa
5. git clone https://github.com/tomato42/tlslite-ng.git .tlslite-ng
6. ln -s .tlslite-ng/tlslite tlslite
7. popd
8. tar xzf certificates.tar.gz
9. gnutls-serv --priority NORMAL:+VERS-TLS1.2 --port 4433 --http --x509cafile ca/cert.pem --x509keyfile server/key.pem --x509certfile server/cert.pem
(in other console, same directory)
10. PYTHONPATH=tlsfuzzer python tlsfuzzer/scripts/test-rsa-sigs-on-certificate-verify.py -k client/key.pem -c client/cert.pem

certificates.tar.gz are attachment 1146558 [details]
Comment 2 Nikos Mavrogiannopoulos 2016-05-26 07:46:32 UTC 
This is a limitation of that code base; similarly with:
https://bugzilla.redhat.com/show_bug.cgi?id=1328205#c1

Will not be addressed.
Comment 3 RHEL Program Management 2016-05-26 08:25:58 UTC 
Development Management has reviewed and declined this request.
You may appeal this decision by reopening this request.
Comment 4 Alicja Kario 2016-05-26 10:22:36 UTC 
there are two solutions to the problem, either implementing support for other hashes or not advertising support for hashes that are not supported. Leaving code as is makes it RFC non compliant.
Comment 5 Nikos Mavrogiannopoulos 2016-05-26 11:27:01 UTC 
Of course there are solutions, but they have to be put in perspective. The plan is to address critical TLS 1.2 issues that will affect our use-case, rsyslog. Not to rewrite the best TLS 1.2 implementation out there based on legacy code.
Comment 6 Nikos Mavrogiannopoulos 2016-05-27 13:55:35 UTC 
Re-opening as this can be addressed by the server not advertising unsupported hashes on certificate request.
Comment 8 Nikos Mavrogiannopoulos 2016-08-09 12:17:25 UTC 
I'm unable to use the reproducer for testing this request. I've verified manually on the 2.12.x rebase, using tcpdump, that the only hashes advertised on a certificate request are the sha1 and sha256 hashes.
Comment 9 Alicja Kario 2016-08-22 14:11:11 UTC 
yes, I will need to write a new test to expect reply with just two hashes
Comment 13 errata-xmlrpc 2017-03-21 09:03:24 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