From 9a79242567d79f42ad1a953cce2b1c4a94df23ea Mon Sep 17 00:00:00 2001 From: "Miss Islington (bot)" <31488909+miss-islington@users.noreply.github.com> Date: Thu, 26 Aug 2021 08:47:27 -0700 Subject: bpo-45001: Make email date parsing more robust against malformed input (GH-27946) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Various date parsing utilities in the email module, such as email.utils.parsedate(), are supposed to gracefully handle invalid input, typically by raising an appropriate exception or by returning None. The internal email._parseaddr._parsedate_tz() helper used by some of these date parsing routines tries to be robust against malformed input, but unfortunately it can still crash ungracefully when a non-empty but whitespace-only input is passed. This manifests as an unexpected IndexError. In practice, this can happen when parsing an email with only a newline inside a ‘Date:’ header, which unfortunately happens occasionally in the real world. Here's a minimal example: $ python Python 3.9.6 (default, Jun 30 2021, 10:22:16) [GCC 11.1.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import email.utils >>> email.utils.parsedate('foo') >>> email.utils.parsedate(' ') Traceback (most recent call last): File "", line 1, in File "/usr/lib/python3.9/email/_parseaddr.py", line 176, in parsedate t = parsedate_tz(data) File "/usr/lib/python3.9/email/_parseaddr.py", line 50, in parsedate_tz res = _parsedate_tz(data) File "/usr/lib/python3.9/email/_parseaddr.py", line 72, in _parsedate_tz if data[0].endswith(',') or data[0].lower() in _daynames: IndexError: list index out of range The fix is rather straight-forward: guard against empty lists, after splitting on whitespace, but before accessing the first element. (cherry picked from commit 989f6a3800f06b2bd31cfef7c3269a443ad94fac) Co-authored-by: wouter bolsterlee --- Lib/email/_parseaddr.py | 2 ++ Lib/test/test_email/test_email.py | 2 ++ Misc/NEWS.d/next/Library/2021-08-26-16-25-48.bpo-45001.tn_dKp.rst | 2 ++ 3 files changed, 6 insertions(+) create mode 100644 Misc/NEWS.d/next/Library/2021-08-26-16-25-48.bpo-45001.tn_dKp.rst diff --git a/Lib/email/_parseaddr.py b/Lib/email/_parseaddr.py index 4d27f87..977fedf 100644 --- a/Lib/email/_parseaddr.py +++ b/Lib/email/_parseaddr.py @@ -67,6 +67,8 @@ def _parsedate_tz(data): if not data: return None data = data.split() + if not data: # This happens for whitespace-only input. + return None # The FWS after the comma after the day-of-week is optional, so search and # adjust for this. if data[0].endswith(',') or data[0].lower() in _daynames: diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py index 0154bba..4001f71 100644 --- a/Lib/test/test_email/test_email.py +++ b/Lib/test/test_email/test_email.py @@ -3003,6 +3003,8 @@ class TestMiscellaneous(TestEmailBase): def test_parsedate_returns_None_for_invalid_strings(self): self.assertIsNone(utils.parsedate('')) self.assertIsNone(utils.parsedate_tz('')) + self.assertIsNone(utils.parsedate(' ')) + self.assertIsNone(utils.parsedate_tz(' ')) self.assertIsNone(utils.parsedate('0')) self.assertIsNone(utils.parsedate_tz('0')) self.assertIsNone(utils.parsedate('A Complete Waste of Time')) diff --git a/Misc/NEWS.d/next/Library/2021-08-26-16-25-48.bpo-45001.tn_dKp.rst b/Misc/NEWS.d/next/Library/2021-08-26-16-25-48.bpo-45001.tn_dKp.rst new file mode 100644 index 0000000..55cc409 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2021-08-26-16-25-48.bpo-45001.tn_dKp.rst @@ -0,0 +1,2 @@ +Made email date parsing more robust against malformed input, namely a +whitespace-only ``Date:`` header. Patch by Wouter Bolsterlee. -- cgit v0.12