Bug 2064790

Summary:	SHA384 in gnutls works only once
Product:	Red Hat Enterprise Linux 8	Reporter:	Miroslav Lichvar <mlichvar>
Component:	gnutls	Assignee:	Daiki Ueno <dueno>
Status:	CLOSED WONTFIX	QA Contact:	BaseOS QE Security Team <qe-baseos-security>
Severity:	unspecified	Docs Contact:
Priority:	medium
Version:	8.5	Keywords:	Triaged
Target Milestone:	rc	Flags:	pm-rhel: mirror+
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Last Closed:	2023-03-22 07:58:27 UTC	Type:	Bug
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Bug Blocks:	2062356

Description Miroslav Lichvar 2022-03-16 14:49:12 UTC

Description of problem:
Some HW-accelerated versions of SHA384 work only once. This was fixed upstream in the following commits:
https://gitlab.com/gnutls/gnutls/-/commit/acdfeb4b3f0c64ad20f28513618e9903bfb81426
https://gitlab.com/gnutls/gnutls/-/commit/66cf3d31b44e5b9300c6fce475f9284caa4cca4d

This bug prevents chrony from switching to gnutls as the hashing library in order to support AES-CMAC keys which are now recommended for NTP authentication in RFC 8573. (AES-CMAC is not supported in the Nettle version present in RHEL8.)

Version-Release number of selected component (if applicable):
gnutls-3.6.16-4.el8.x86_64

How reproducible:
always

Steps to Reproduce:
1. build chrony-4.2 configured with option "--without-nettle"
2. make check

Actual results:
...
Testing hash                           FAIL (on line 119)

Expected results:

All tests passed

Comment 1 Daiki Ueno 2022-03-17 10:24:46 UTC

I guess this could be worked around by not using gnutls_hash_copy but always create a new context, but it's not acceptable because of performance, right?

Comment 2 Miroslav Lichvar 2022-03-17 10:35:01 UTC

Yes, in the chrony case the hash context is reused for performance reasons and to avoid unnecessary memory allocations. It does not call gnutls_hash_copy(), it relies on gnutls_hash_output() resetting the state.