Bug 2143266

Summary:	In FIPS mode, gnutls should reject RSASSA-PSS salt lengths larger than the output size of the hash function used, or provide an indicator
Product:	Red Hat Enterprise Linux 9	Reporter:	Daiki Ueno <dueno>
Component:	gnutls	Assignee:	Daiki Ueno <dueno>
Status:	CLOSED ERRATA	QA Contact:	Alexander Sosedkin <asosedki>
Severity:	unspecified	Docs Contact:
Priority:	high
Version:	9.0	CC:	asosedki, ssorce
Target Milestone:	rc	Keywords:	Triaged, ZStream
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	gnutls-3.7.6-14.el9	Doc Type:	No Doc Update
Doc Text:		Story Points:	---
Clone Of:
Clones:	2144537 2144538 2153473 (view as bug list)		Environment:
Last Closed:	2023-05-09 08:20:29 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:	2144537, 2144538, 2153473

Description Daiki Ueno 2022-11-16 13:31:01 UTC

This bug was initially created as a copy of Bug #2142087.  I am copying this bug because this is also the case with GnuTLS.

Description of problem:
FIPS 186-4, section 5 "The RSA Digital Signature Algorithm", subsection 5.5 "PKCS #1" says:

For RSASSA-PSS […] the length (in bytes) of the salt (sLen) shall satisfy 0 ≤ sLen ≤ hLen, where hLen is the length of the hash function output block (in bytes).

Our current copy of GnuTLS does not enforce this nor report it through FIPS service indicator as an non-approved operation.

Version-Release number of selected component (if applicable):
gnutls-3.7.6-12.el9_0

How reproducible:
always

Steps to Reproduce:
1. generate RSA-PSS private key: certtool --generate-privkey --key-type=rsa-pss --bits=2048 --salt-size=33 --hash=sha256 --outfile key.pem
2. create self-signed certificate signed with the key generated at (1): GNUTLS_FORCE_FIPS_MODE=1 certtool --generate-self-signed --load-privkey key.pem --template=doc/credentials/server.tmpl --outfile cert.pem

Actual results:
Both commands succeed

Expected results:
(2) should fail or report that non-approved crypto operation has happened in the audit log message

Additional info:
GnuTLS by default use the salt length equal to the hash length (if it is truncated by RSA key size), while other standards, e.g., TPM, may impose the maximum possible salt length depending on RSA key size

Comment 8 errata-xmlrpc 2023-05-09 08:20:29 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 (gnutls bug fix and enhancement update), 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://access.redhat.com/errata/RHBA-2023:2522