Bug 2218870

Summary: redhat-support-tool: 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: redhat-support-toolAssignee: Pranita Ghole <pghole>
Status: CLOSED MIGRATED QA Contact: Supportability QE <supportability-qe>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 8.9CC: cww, pghole, pmoravec, torsava
Target Milestone: rcKeywords: MigratedToJIRA
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Last Closed: 2023-09-06 13:49:50 UTC Type: Bug
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Blocks: 263261    

Description Petr Viktorin (pviktori) 2023-06-30 11:06:48 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

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In /usr/lib/python3.6/site-packages/redhat_support_tool/helpers/soscleaner.py, redhat-support-tool calls `p.extractall()`. The call will emit a warning by default. Something like this should be added before the call:

p.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:
p.extractall(self.origin_path, filter='data')

The 'data_filter' above attempts a "safe" extraction, intended for pure data archives. For example:
- prevents extracting outside the target directory, and to absolute paths (by raising an exception)
- prevents symlinks pointing outside the target directory, and to absolute paths
- adjusts permissions (for the owner, only the executable bit is honored)
See PEP 706 for details: https://peps.python.org/pep-0706/#filters

You can additionally set `p.errorlevel = 0` to skip extracting "bad" files with a warning on stderr.

If you trust the tarball, use `'fully_trusted_filter'` (or `filter='fully_trusted'`) instead. That will preserve the existing behavior.

---

Let me know if you have any questions!

Comment 2 Pavel Moravec 2023-09-05 20:48:51 UTC
FYI I recommend using fully_trusted_filter like we did in sos (https://github.com/sosreport/sos/pull/3330#issuecomment-1673260445 and above discussion). It just encapsulates the problem, but Python 3.11 or lower does not implement the other filter well /o\

Comment 3 RHEL Program Management 2023-09-06 13:49:11 UTC
Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug.

Comment 4 RHEL Program Management 2023-09-06 13:49:50 UTC
This BZ has been automatically migrated to the issues.redhat.com Red Hat Issue Tracker. All future work related to this report will be managed there.

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Comment 5 Red Hat Bugzilla 2024-01-05 04:25:14 UTC
The needinfo request[s] on this closed bug have been removed as they have been unresolved for 120 days