Bug 2217905 - oscap-anaconda-addon: Python tarfile extraction needs change to avoid a warning (CVE-2007-4559 mitigation)
Summary: oscap-anaconda-addon: Python tarfile extraction needs change to avoid a warni...
Keywords:
Status: CLOSED DUPLICATE of bug 2218875
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: oscap-anaconda-addon
Version: 9.3
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Matěj Týč
QA Contact: Release Test Team
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2023-06-27 12:36 UTC by Petr Viktorin
Modified: 2023-07-17 15:01 UTC (History)
2 users (show)

Fixed In Version:
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Last Closed: 2023-07-17 15:01:28 UTC
Type: Bug
Target Upstream Version:
Embargoed:


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Red Hat Issue Tracker RHELPLAN-160928 0 None None None 2023-06-27 12:36:47 UTC

Description Petr Viktorin 2023-06-27 12:36:08 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

---

In /usr/share/anaconda/addons/org_fedora_oscap/common.py, oscap-anaconda-addon calls `tfile.extractall(...)`. The call will emit a warning by default, and should be changed to something like:

if hasattr(tarfile, 'data_filter'):
    # Python with CVE-2007-4559 mitigation (PEP 706)
    tfile.extractall(..., filter='data')
else:
    # Fallback to a possibly dangerous extraction (before PEP 706)
    tfile.extractall(...)

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

If you trust that the archive is not malicious, you can use `filter='fully_trusted'` instead. That will preserve the existing behavior.

---

Let me know if you have any questions!

Comment 1 Matěj Týč 2023-07-17 15:01:28 UTC

*** This bug has been marked as a duplicate of bug 2218875 ***


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