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Bug 2219388

Summary: [RHEL8] pcs: Python tarfile extraction needs change to avoid a warning (CVE-2007-4559 mitigation)
Product: Red Hat Enterprise Linux 8 Reporter: Petr Viktorin (pviktori) <pviktori>
Component: pcsAssignee: Tomas Jelinek <tojeline>
Status: CLOSED ERRATA QA Contact: cluster-qe <cluster-qe>
Severity: high Docs Contact:
Priority: high    
Version: 8.9CC: cluster-maint, cstratak, idevat, mlisik, mmazoure, mpospisi, nhostako, omular, tojeline
Target Milestone: rcKeywords: Triaged
Target Release: 8.9Flags: pm-rhel: mirror+
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: pcs-0.10.17-2.el8 Doc Type: Bug Fix
Doc Text:
I suppose this is going to be documented together with bz263261
 Story Points: ---
Clone Of:
: 2219407 (view as bug list) Environment:
Last Closed: 2023-11-14 15:22:35 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: 263261, 2219407    

Description Petr Viktorin (pviktori) 2023-07-03 12:29:05 UTC 
Hello,
In RHEL 9.3 and 8.9, we're planning to fix the long-standing CVE-2007-4559: Python's `tarfile` module makes it too easy to extract tarballs in an unsafe way.
Unfortunately, for the CVE to be considered fixed, this needs a behavior change. (If you don't think this is the case, let's bring it up with the security team.)
Upstream, Python will emit deprecation warnings for 2 releases, but in RHEL we change the behavior now, emit warnings, and provide ways for customers to restore earlier behavior.
To avoid the warning, software shipped by Red Hat will need a change.

For more details see upstream PEP 706: https://peps.python.org/pep-0706
and the Red Hat knowledge base draft: https://access.redhat.com/articles/7004769

---

As reported on rhel devel (thanks!), pcs uses extractall in:

https://github.com/ClusterLabs/pcs/blob/main/pcs/config.py#L491
https://github.com/ClusterLabs/pcs/blob/main/pcs/config.py#L498


The call will emit a warning by default. To prevent that, add something like this before the call:

tarball.extraction_filter = getattr(tarfile, 'data_filter',
                                    (lambda member, path: member))

This is compatible with unpatched versions of Python. If you only build for RHEL8.9+, instead add an argument to the call:
`tarball.extractall(..., filter='data')`.

I don't know about the tarball you're extracting here.
If it's pure data (configuration files), use 'data_filter' (or filter='data') as above.
If it's a trusted system archive, use 'fully_trusted_filter' (or filter='fully_trusted').
There's also 'tar_filter', somewhere in between.

See the docs for details: https://docs.python.org/3/library/tarfile.html?default-named-filters

---

Let me know if you have any questions!
Comment 2 Tomas Jelinek 2023-07-12 14:16:24 UTC 
Upstream patch: https://github.com/ClusterLabs/pcs/commit/44301c7ba83c5efa9db1113bd9491de796ebded4

Test:

Make sure to install patched python packages - they make unpatched pcs print a warning.

[root@rh88-node1:~]# rpm -q platform-python
platform-python-3.6.8-52.el8.x86_64

Before fix:
[root@rh88-node1:~]# pcs config restore /root/backup.tar.bz2 --local
/usr/lib64/python3.6/tarfile.py:2214: RuntimeWarning: The default behavior of tarfile extraction has been changed to disallow common exploits (including CVE-2007-4559). By default, absolute/parent paths are disallowed and some mode bits are cleared. See https://access.redhat.com/articles/7004769 for more details.
  RuntimeWarning)
[root@rh88-node1:~]# echo $?
0

After fix:
[root@rh88-node1:~]# pcs/pcs config restore /root/backup.tar.bz2 --local
[root@rh88-node1:~]# echo $?
0

Verify, that 'pcs config restore' and 'pcs config restore --local' works - if in doubt, see bz1024492 for original tests.
Comment 3 Michal Pospisil 2023-07-14 08:41:28 UTC 
DevTestResults:

[root@r08-09-a ~]# pcs config backup /root/backup.tar.bz2

[root@r08-09-a ~]# pcs cluster destroy
Shutting down pacemaker/corosync services...
Killing any remaining services...
Removing all cluster configuration files...

[root@r08-09-a ~]# pcs config restore /root/backup.tar.bz2 --local

[root@r08-09-a ~]# echo $?
0
Comment 8 Michal Mazourek 2023-08-21 15:26:04 UTC 
The same test as in bz2219407 comment 8 was conducted to verify this bz.

Marking as VERIFIED for pcs-0.10.17-2.el8.
Comment 10 errata-xmlrpc 2023-11-14 15:22:35 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 (pcs 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-2023:6903