gh-102988: Detect email address parsing errors and return empty tuple to indicate the parsing error (old API)

Doc/whatsnew/3.13.rst

@@ -122,6 +122,14 @@ dbm
  from the database.
  (Contributed by Dong-hee Na in :gh:`107122`.)
 
+email
+-----
+
+* :func:`email.utils.getaddresses` and :func:`email.utils.parseaddr` now return
+ ``('', '')`` 2-tuples in more situations where invalid email addresses are
+ encountered instead of potentially inaccurate values.
+ (Contributed by Thomas Dwyer for :gh:`102988` to ameliorate CVE-2023-27043.)
+
 io
 --
 

Lib/email/utils.py

@@ -106,12 +106,62 @@ def formataddr(pair, charset='utf-8'):
  return address
 
 
+def _pre_parse_validation(email_header_fields):
+ accepted_values = []
+ for v in email_header_fields:
+ s = v.replace('\\(', '').replace('\\)', '')
+ if s.count('(') != s.count(')'):
+ v = "('', '')"
+ accepted_values.append(v)
+
+ return accepted_values
+
+
+def _post_parse_validation(parsed_email_header_tuples):
+ accepted_values = []
+ # The parser would have parsed a correctly formatted domain-literal
+ # The existence of an [ after parsing indicates a parsing failure
+ for v in parsed_email_header_tuples:
+ if '[' in v[1]:
+ v = ('', '')
+ accepted_values.append(v)
+
+ return accepted_values
+
 
 def getaddresses(fieldvalues):
- """Return a list of (REALNAME, EMAIL) for each fieldvalue."""
- all = COMMASPACE.join(str(v) for v in fieldvalues)
+ """Return a list of (REALNAME, EMAIL) or ('','') for each fieldvalue.
+
+ When parsing fails for a fieldvalue, a 2-tuple of ('', '') is returned in
+ its place.
+
+ If the resulting list of parsed address is greater than number of
+ fieldvalues in the input list a parsing error has occurred, so a list
+ containing a single empty 2-tuple [('', '')] is returned in its place.
+ This is done to avoid invalid output.
+
+ Malformed input: getaddresses(['[email protected] <[email protected]>'])
+ Invalid output: [('', '[email protected]'), ('', '[email protected]')]
+ Safe output: [('', '')]
+ """
+ fieldvalues = [str(v) for v in fieldvalues]
+ fieldvalues = _pre_parse_validation(fieldvalues)
+ all = COMMASPACE.join(v for v in fieldvalues)
  a = _AddressList(all)
- return a.addresslist
+ result = _post_parse_validation(a.addresslist)
+
+ # When a comma is used in the Real Name part it is not a deliminator
+ # So strip those out before counting the commas
+ pattern = r'"[^"]*,[^"]*"'
+ n = 0
+ for v in fieldvalues:
+ v = re.sub(pattern, '', v)
+ n += v.count(',') + 1
+
+ if len(result) != n:
+ return [('', '')]
+
+ return result
 
 
 def _format_timetuple_and_zone(timetuple, zone):
@@ -212,9 +262,18 @@ def parseaddr(addr):
  Return a tuple of realname and email address, unless the parse fails, in
  which case return a 2-tuple of ('', '').
  """
- addrs = _AddressList(addr).addresslist
- if not addrs:
- return '', ''
+ if isinstance(addr, list):
+ addr = addr[0]
+
+ if not isinstance(addr, str):
+ return ('', '')
+
+ addr = _pre_parse_validation([addr])[0]
+ addrs = _post_parse_validation(_AddressList(addr).addresslist)
+
+ if not addrs or len(addrs) > 1:
+ return ('', '')
+
  return addrs[0]
 
 

Lib/test/test_email/test_email.py

@@ -3319,32 +3319,96 @@ def test_getaddresses(self):
  [('Al Person', '[email protected]'),
  ('Bud Person', '[email protected]')])
 
- def test_getaddresses_comma_in_name(self):
- """GH-106669 regression test."""
- self.assertEqual(
- utils.getaddresses(
- [
- '"Bud, Person" <[email protected]>',
- '[email protected] (Al Person)',
- '"Mariusz Felisiak" <[email protected]>',
- ]
- ),
- [
- ('Bud, Person', '[email protected]'),
- ('Al Person', '[email protected]'),
- ('Mariusz Felisiak', '[email protected]'),
- ],
- )
+ def test_getaddresses_parsing_errors(self):
+ """Test for parsing errors from CVE-2023-27043 and CVE-2019-16056"""
+ eq = self.assertEqual
+ eq(utils.getaddresses(['[email protected](<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected])<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected]<<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected]><[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected]@<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected],<[email protected]>']),
+ [('', '[email protected]'), ('', '[email protected]')])
+ eq(utils.getaddresses(['[email protected];<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected]:<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected].<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected]"<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected][<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['[email protected]]<[email protected]>']),
+ [('', '')])
+ eq(utils.getaddresses(['"Alice, [email protected]" <[email protected]>']),
+ [('Alice, [email protected]', '[email protected]')])
+
+ def test_parseaddr_parsing_errors(self):
+ """Test for parsing errors from CVE-2023-27043 and CVE-2019-16056"""
+ eq = self.assertEqual
+ eq(utils.parseaddr(['[email protected](<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected])<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected]<<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected]><[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected]@<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected],<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected];<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected]:<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected].<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected]"<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected][<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['[email protected]]<[email protected]>']),
+ ('', ''))
+ eq(utils.parseaddr(['"Alice, [email protected]" <[email protected]>']),
+ ('Alice, [email protected]', '[email protected]'))
 
  def test_getaddresses_nasty(self):
  eq = self.assertEqual
+ eq(utils.getaddresses(['"Sürname, Firstname" <[email protected]>']),
+ [('Sürname, Firstname', '[email protected]')])
  eq(utils.getaddresses(['foo: ;']), [('', '')])
- eq(utils.getaddresses(
- ['[]*-- =~$']),
- [('', ''), ('', ''), ('', '*--')])
+ eq(utils.getaddresses(['[]*-- =~$']), [('', '')])
  eq(utils.getaddresses(
  ['foo: ;', '"Jason R. Mastaler" <[email protected]>']),
  [('', ''), ('Jason R. Mastaler', '[email protected]')])
+ eq(utils.getaddresses(
+ [r'Pete(A nice \) chap) <pete(his account)@silly.test(his host)>']),
+ [('Pete (A nice ) chap his account his host)', '[email protected]')])
+ eq(utils.getaddresses(
+ ['(Empty list)(start)Undisclosed recipients :(nobody(I know))']),
+ [('', '')])
+ eq(utils.getaddresses(
+ ['Mary <@machine.tld:[email protected]>, , jdoe@test . example']),
+ [('Mary', '[email protected]'), ('', ''), ('', '[email protected]')])
+ eq(utils.getaddresses(
+ ['John Doe <jdoe@machine(comment). example>']),
+ [('John Doe (comment)', '[email protected]')])
+ eq(utils.getaddresses(
+ ['"Mary Smith: Personal Account" <[email protected]>']),
+ [('Mary Smith: Personal Account', '[email protected]')])
+ eq(utils.getaddresses(
+ ['Undisclosed recipients:;']),
+ [('', '')])
+ eq(utils.getaddresses(
+ [r'<[email protected]>, "Giant; \"Big\" Box" <[email protected]>']),
+ [('', '[email protected]'), ('Giant; "Big" Box', '[email protected]')])
 
  def test_getaddresses_embedded_comment(self):
  """Test proper handling of a nested comment"""
@@ -3712,16 +3776,6 @@ def test_bytes_header_parser(self):
  self.assertIsInstance(msg.get_payload(), str)
  self.assertIsInstance(msg.get_payload(decode=True), bytes)
 
- def test_header_parser_multipart_is_valid(self):
- # Don't flag valid multipart emails as having defects
- with openfile('msg_47.txt', encoding="utf-8") as fp:
- msgdata = fp.read()
-
- parser = email.parser.Parser(policy=email.policy.default)
- parsed_msg = parser.parsestr(msgdata, headersonly=True)
-
- self.assertEqual(parsed_msg.defects, [])
-
  def test_bytes_parser_does_not_close_file(self):
  with openfile('msg_02.txt', 'rb') as fp:
  email.parser.BytesParser().parse(fp)