[3.7] bpo-32981: Fix catastrophic backtracking vulns (GH-5955) #5969
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* Prevent low-grade poplib REDOS (CVE-2018-1060) The regex to test a mail server's timestamp is susceptible to catastrophic backtracking on long evil responses from the server. Happily, the maximum length of malicious inputs is 2K thanks to a limit introduced in the fix for CVE-2013-1752. A 2KB evil response from the mail server would result in small slowdowns (milliseconds vs. microseconds) accumulated over many apop calls. This is a potential DOS vector via accumulated slowdowns. Replace it with a similar non-vulnerable regex. The new regex is RFC compliant. The old regex was non-compliant in edge cases. * Prevent difflib REDOS (CVE-2018-1061) The default regex for IS_LINE_JUNK is susceptible to catastrophic backtracking. This is a potential DOS vector. Replace it with an equivalent non-vulnerable regex. Also introduce unit and REDOS tests for difflib. Co-authored-by: Tim Peters <tim.peters@gmail.com> Co-authored-by: Christian Heimes <christian@python.org> (cherry picked from commit 0e6c8ee) Co-authored-by: Jamie Davis <davisjam@vt.edu>
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@davisjam and @benjaminp: Backport status check is done, and it's a success ✅ . |
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Thanks, @benjaminp! |
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The regex to test a mail server's timestamp is susceptible to
catastrophic backtracking on long evil responses from the server.
Happily, the maximum length of malicious inputs is 2K thanks
to a limit introduced in the fix for CVE-2013-1752.
A 2KB evil response from the mail server would result in small slowdowns
(milliseconds vs. microseconds) accumulated over many apop calls.
This is a potential DOS vector via accumulated slowdowns.
Replace it with a similar non-vulnerable regex.
The new regex is RFC compliant.
The old regex was non-compliant in edge cases.
The default regex for IS_LINE_JUNK is susceptible to
catastrophic backtracking.
This is a potential DOS vector.
Replace it with an equivalent non-vulnerable regex.
Also introduce unit and REDOS tests for difflib.
Co-authored-by: Tim Peters tim.peters@gmail.com
Co-authored-by: Christian Heimes christian@python.org
(cherry picked from commit 0e6c8ee)
Co-authored-by: Jamie Davis davisjam@vt.edu
https://bugs.python.org/issue32981