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

Doc/library/email.utils.rst

@@ -65,6 +65,11 @@ of the new API.
  *email address* parts. Returns a tuple of that information, unless the parse
  fails, in which case a 2-tuple of ``('', '')`` is returned.
 
+ .. versionchanged:: 3.12
+ For security reasons, addresses that were ambiguous and could parse into
+ multiple different addresses now cause ``('', '')`` to be returned
+ instead of only one of the *potential* addresses.
+
 
 .. function:: formataddr(pair, charset='utf-8')
 
@@ -87,7 +92,7 @@ of the new API.
  This method returns a list of 2-tuples of the form returned by ``parseaddr()``.
  *fieldvalues* is a sequence of header field values as might be returned by
  :meth:`Message.get_all <email.message.Message.get_all>`. Here's a simple
- example that gets all the recipients of a message::
+ example that gets all the recipients of a message:
 
  from email.utils import getaddresses
 
@@ -97,6 +102,25 @@ of the new API.
  resent_ccs = msg.get_all('resent-cc', [])
  all_recipients = getaddresses(tos + ccs + resent_tos + resent_ccs)
 
+ When parsing fails for a single fieldvalue, a 2-tuple of ``('', '')``
+ is returned in its place. Other errors in parsing the list of
+ addresses such as a fieldvalue seemingly parsing into multiple
+ addresses may result in a list containing a single empty 2-tuple
+ ``[('', '')]`` being returned rather than returning potentially
+ invalid output.
+
+ Example malformed input parsing:
+
+ .. doctest::
+
+ >>> from email.utils import getaddresses
+ >>> getaddresses(['[email protected] <[email protected]>', '[email protected]'])
+ [('', '')]
+
+ .. versionchanged:: 3.12
+ The 2-tuple of ``('', '')`` in the returned values when parsing
+ fails were added as to address a security issue.
+
 
 .. function:: parsedate(date)
 

Doc/whatsnew/3.12.rst

@@ -564,6 +564,14 @@ dis
  :data:`~dis.hasarg` collection instead.
  (Contributed by Irit Katriel in :gh:`94216`.)
 
+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.)
+
 fractions
 ---------
 

Lib/email/utils.py

@@ -106,12 +106,54 @@ 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 not the same as the number of
+ fieldvalues in the input list a parsing error has occurred. A list
+ containing a single empty 2-tuple [('', '')] is returned in its place.
+ This is done to avoid invalid 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)
+
+ n = 0
+ for v in fieldvalues:
+ n += v.count(',') + 1
+
+ if len(result) != n:
+ return [('', '')]
+
+ return result
 
 
 def _format_timetuple_and_zone(timetuple, zone):
@@ -212,9 +254,18 @@ 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

@@ -3319,15 +3319,90 @@ def test_getaddresses(self):
  [('Al Person', '[email protected]'),
  ('Bud Person', '[email protected]')])
 
+ def test_getaddresses_parsing_errors(self):
+ """Test for parsing errors from CVE-2023-27043"""
+ 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]>']),
+ [('', '')])
+
+ def test_parseaddr_parsing_errors(self):
+ """Test for parsing errors from CVE-2023-27043"""
+ 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]>']),
+ ('', ''))
+
  def test_getaddresses_nasty(self):
  eq = self.assertEqual
  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"""

Misc/NEWS.d/next/Security/2023-06-13-20-52-24.gh-issue-102988.Kei7Vf.rst

@@ -0,0 +1,4 @@
+CVE-2023-27043: Prevent :func:`email.utils.parseaddr`
+and :func:`email.utils.getaddresses` from returning the realname portion of an
+invalid RFC2822 email header in the email address portion of the 2-tuple
+returned after being parsed by :class:`email._parseaddr.AddressList`.