bpo-30681: Support invalid date format or value in email Date header (GH-22090)

I am re-submitting an older PR which was abandoned but is still relevant, #10783 by @timb07.

The issue being solved () is still relevant. The original PR #10783 was closed as
the final request changes were not applied and since abandoned.

In this new PR I have re-used the original patch plus applied both comments from the review, by @maxking and @pganssle.


For reference, here is the original PR description:
In email.utils.parsedate_to_datetime(), a failure to parse the date, or invalid date components (such as hour outside 0..23) raises an exception. Document this behaviour, and add tests to test_email/test_utils.py to confirm this behaviour.

In email.headerregistry.DateHeader.parse(), check when parsedate_to_datetime() raises an exception and add a new defect InvalidDateDefect; preserve the invalid value as the string value of the header, but set the datetime attribute to None.

Add tests to test_email/test_headerregistry.py to confirm this behaviour; also added test to test_email/test_inversion.py to confirm emails with such defective date headers round trip successfully.

This pull request incorporates feedback gratefully received from @bitdancer, @brettcannon, @Mariatta and @warsaw, and replaces the earlier PR #2254.

Automerge-Triggered-By: GH:warsaw

4 files changed, 16 insertions, 3 deletions

diff --git a/Lib/email/_parseaddr.py b/Lib/email/_parseaddr.py
index 41ff6f8..4d27f87 100644
--- a/Lib/email/_parseaddr.py
+++ b/Lib/email/_parseaddr.py
@@ -65,7 +65,7 @@ def _parsedate_tz(data):
 
     """
     if not data:
-        return
+        return None
     data = data.split()
     # The FWS after the comma after the day-of-week is optional, so search and
     # adjust for this.
diff --git a/Lib/email/errors.py b/Lib/email/errors.py
index d28a680..1d258c3 100644
--- a/Lib/email/errors.py
+++ b/Lib/email/errors.py
@@ -108,3 +108,6 @@ class NonASCIILocalPartDefect(HeaderDefect):
     """local_part contains non-ASCII characters"""
     # This defect only occurs during unicode parsing, not when
     # parsing messages decoded from binary.
+
+class InvalidDateDefect(HeaderDefect):
+    """Header has unparseable or invalid date"""
diff --git a/Lib/email/headerregistry.py b/Lib/email/headerregistry.py
index 5d84fc0..d8613eb 100644
--- a/Lib/email/headerregistry.py
+++ b/Lib/email/headerregistry.py
@@ -302,7 +302,14 @@ class DateHeader:
             kwds['parse_tree'] = parser.TokenList()
             return
         if isinstance(value, str):
-            value = utils.parsedate_to_datetime(value)
+            kwds['decoded'] = value
+            try:
+                value = utils.parsedate_to_datetime(value)
+            except ValueError:
+                kwds['defects'].append(errors.InvalidDateDefect('Invalid date value or format'))
+                kwds['datetime'] = None
+                kwds['parse_tree'] = parser.TokenList()
+                return
         kwds['datetime'] = value
         kwds['decoded'] = utils.format_datetime(kwds['datetime'])
         kwds['parse_tree'] = cls.value_parser(kwds['decoded'])
diff --git a/Lib/email/utils.py b/Lib/email/utils.py
index 1a7719d..a8e46a7 100644
--- a/Lib/email/utils.py
+++ b/Lib/email/utils.py
@@ -195,7 +195,10 @@ def make_msgid(idstring=None, domain=None):
 
 
 def parsedate_to_datetime(data):
-    *dtuple, tz = _parsedate_tz(data)
+    parsed_date_tz = _parsedate_tz(data)
+    if parsed_date_tz is None:
+        raise ValueError('Invalid date value or format "%s"' % str(data))
+    *dtuple, tz = parsed_date_tz
     if tz is None:
         return datetime.datetime(*dtuple[:6])
     return datetime.datetime(*dtuple[:6],