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Bug 2143266 - In FIPS mode, gnutls should reject RSASSA-PSS salt lengths larger than the output size of the hash function used, or provide an indicator
Summary: In FIPS mode, gnutls should reject RSASSA-PSS salt lengths larger than the ou...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: gnutls
Version: 9.0
Hardware: Unspecified
OS: Unspecified
high
unspecified
Target Milestone: rc
: ---
Assignee: Daiki Ueno
QA Contact: Alexander Sosedkin
URL:
Whiteboard:
Depends On:
Blocks: 2144537 2144538 2153473
TreeView+ depends on / blocked
 
Reported: 2022-11-16 13:31 UTC by Daiki Ueno
Modified: 2023-05-09 10:30 UTC (History)
2 users (show)

Fixed In Version: gnutls-3.7.6-14.el9
Doc Type: No Doc Update
Doc Text:
Clone Of:
: 2144537 2144538 2153473 (view as bug list)
Environment:
Last Closed: 2023-05-09 08:20:29 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Gitlab gnutls gnutls merge_requests 1669 0 None opened nettle: mark non-compliant RSA-PSS salt length to be not-approved 2022-11-16 15:02:12 UTC
Red Hat Issue Tracker CRYPTO-8771 0 None None None 2022-11-16 15:37:34 UTC
Red Hat Issue Tracker RHELPLAN-139607 0 None None None 2022-11-16 14:31:41 UTC
Red Hat Product Errata RHBA-2023:2522 0 None None None 2023-05-09 08:20:50 UTC

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
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