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Bug 1835169

Summary:	Python's _Py_KeyedHash() uses non-FIPS compliant MAC
Product:	Red Hat Enterprise Linux 9	Reporter:	Christian Heimes <cheimes>
Component:	python3.9	Assignee:	Python Maintainers <python-maint>
Status:	CLOSED ERRATA	QA Contact:	Lukáš Zachar <lzachar>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	9.0	CC:	cstratak, hhorak, pviktori, torsava, vstinner
Target Milestone:	pre-dev-freeze	Keywords:	Triaged
Target Release:	---	Flags:	pm-rhel: mirror+
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	python3.9-3.9.10-1.el9	Doc Type:	No Doc Update
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2022-05-17 15:36:22 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:	1942527
Bug Blocks:

Description Christian Heimes 2020-05-13 09:57:17 UTC

Description of problem:
Python 3.7 introduced a new way to validate .pyc bytecode files [1]. PYC files can either contain the last modification timestamp of their .py code or a keyed hash (MAC) of the .py file.

The hash and mac algorithm behind _imp.source_hash() and _Py_KeyedHash() is hard-coded to sip24, which is not FIPS compliant.

Version-Release number of selected component (if applicable):
3.7, 3.8, 3.9-alpha

How reproducible:
always

Additional info:
[1] https://docs.python.org/3.9/reference/import.html#pyc-invalidation
[2] https://github.com/python/cpython/blob/f453221c8b80e0570066a9375337f208d50e6406/Python/pyhash.c#L421-L425

Comment 1 Honza Horak 2020-08-07 13:41:04 UTC

Thanks for the report. I'm wondering whether having this reported for RHEL-9 only does not make it less visible or ignored.. FYI Tomas, do you think it needs to be cloned for Fedora or RHEL8 (for upcoming python39 module) or it is ok this way?

Comment 2 Tomas Orsava 2020-08-07 13:51:17 UTC

(In reply to Honza Horak from comment #1)
> Thanks for the report. I'm wondering whether having this reported for RHEL-9
> only does not make it less visible or ignored.. FYI Tomas, do you think it
> needs to be cloned for Fedora or RHEL8 (for upcoming python39 module) or it
> is ok this way?

I've already added this (and a query for RHEL9 bugs in general) to the agenda of our next RHEL bugs triage (the coming Wednesday) so we can assess the impact elsewhere as well.
Nevertheless, thanks for the ping, better be safe than sorry.

Comment 3 Petr Viktorin (pviktori) 2020-08-12 12:28:55 UTC

The simple, and IMO reasonable, fix is to disable that validation mode (under FIPS only).

Comment 4 Victor Stinner 2020-09-09 12:19:54 UTC

I understand that there are two choices to make Python FIPS compliant:

* Use the file modification rather than a hash of the content for pyc files, especially to *create* pyc files (PEP 552): see SourceLoader.get_code() in Lib/importlib/_bootstrap_external.py
* Use a different hash algorithm: see _imp.source_hash() and _Py_KeyedHash()

I'm not sure if it's possible to detect when Python is running in FIPS mode, and only change the behavior in this case.

Comment 6 Petr Viktorin (pviktori) 2020-10-07 13:29:05 UTC

Christian, we'll do a downstream patch, unless you put this into upstream -- you're probably the best person to push these changes in CPython.

Comment 7 Petr Viktorin (pviktori) 2021-08-25 12:07:50 UTC

FIPS support in OpenSSL 3.0 is blocking us; moving to RHEL 9 GA.

Comment 17 errata-xmlrpc 2022-05-17 15:36:22 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 (new packages: python3.9), 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-2022:3899