[2.7] bpo-32981: Fix catastrophic backtracking vulns (GH-5955)
* 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 0e6c8ee2358a2e23117501826c008842acb835ac)
diff --git a/Lib/poplib.py b/Lib/poplib.py
index b91e5f7..a238510 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -274,7 +274,7 @@
return self._shortcmd('RPOP %s' % user)
- timestamp = re.compile(r'\+OK.*(<[^>]+>)')
+ timestamp = re.compile(br'\+OK.[^<]*(<.*>)')
def apop(self, user, secret):
"""Authorisation