python39/SOURCES/00415-cve-2023-27043-gh-102988-reject-malformed-addresses-in-email-parseaddr-111116.patch

From 4df4fad359c280f2328b98ea9b4414f244624a58 Mon Sep 17 00:00:00 2001
From: Lumir Balhar <lbalhar@redhat.com>
Date: Mon, 18 Dec 2023 20:15:33 +0100
Subject: [PATCH] Make it possible to disable strict parsing in email module

---
 Doc/library/email.utils.rst       | 26 +++++++++++
 Lib/email/utils.py                | 54 ++++++++++++++++++++++-
 Lib/test/test_email/test_email.py | 72 ++++++++++++++++++++++++++++++-
 3 files changed, 149 insertions(+), 3 deletions(-)

diff --git a/Doc/library/email.utils.rst b/Doc/library/email.utils.rst
index d1e1898591..7aef773b5f 100644
--- a/Doc/library/email.utils.rst
+++ b/Doc/library/email.utils.rst
@@ -69,6 +69,19 @@ of the new API.
 
    If *strict* is true, use a strict parser which rejects malformed inputs.
 
+   The default setting for *strict* is set to ``True``, but you can override
+   it by setting the environment variable ``PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING``
+   to non-empty string.
+
+   Additionally, you can permanently set the default value for *strict* to
+   ``False`` by creating the configuration file ``/etc/python/email.cfg``
+   with the following content:
+
+   .. code-block:: ini
+
+      [email_addr_parsing]
+      PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING = true
+
    .. versionchanged:: 3.9.20
       Add *strict* optional parameter and reject malformed inputs by default.
 
@@ -97,6 +110,19 @@ of the new API.
 
    If *strict* is true, use a strict parser which rejects malformed inputs.
 
+   The default setting for *strict* is set to ``True``, but you can override
+   it by setting the environment variable ``PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING``
+   to non-empty string.
+
+   Additionally, you can permanently set the default value for *strict* to
+   ``False`` by creating the configuration file ``/etc/python/email.cfg``
+   with the following content:
+
+   .. code-block:: ini
+
+      [email_addr_parsing]
+      PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING = true
+
    Here's a simple example that gets all the recipients of a message::
 
       from email.utils import getaddresses
diff --git a/Lib/email/utils.py b/Lib/email/utils.py
index f83b7e5d7e..b8e90ceb8e 100644
--- a/Lib/email/utils.py
+++ b/Lib/email/utils.py
@@ -48,6 +48,46 @@ TICK = "'"
 specialsre = re.compile(r'[][\\()<>@,:;".]')
 escapesre = re.compile(r'[\\"]')
 
+_EMAIL_CONFIG_FILE = "/etc/python/email.cfg"
+_cached_strict_addr_parsing = None
+
+
+def _use_strict_email_parsing():
+    """"Cache implementation for _cached_strict_addr_parsing"""
+    global _cached_strict_addr_parsing
+    if _cached_strict_addr_parsing is None:
+        _cached_strict_addr_parsing = _use_strict_email_parsing_impl()
+    return _cached_strict_addr_parsing
+
+
+def _use_strict_email_parsing_impl():
+    """Returns True if strict email parsing is not disabled by
+    config file or env variable.
+    """
+    disabled = bool(os.environ.get("PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING"))
+    if disabled:
+        return False
+
+    try:
+        file = open(_EMAIL_CONFIG_FILE)
+    except FileNotFoundError:
+        pass
+    else:
+        with file:
+            import configparser
+            config = configparser.ConfigParser(
+                interpolation=None,
+                comment_prefixes=('#', ),
+
+            )
+            config.read_file(file)
+            disabled = config.getboolean('email_addr_parsing', "PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING", fallback=None)
+
+    if disabled:
+        return False
+
+    return True
+
 
 def _has_surrogates(s):
     """Return True if s contains surrogate-escaped binary data."""
@@ -149,7 +189,7 @@ def _strip_quoted_realnames(addr):
 
 supports_strict_parsing = True
 
-def getaddresses(fieldvalues, *, strict=True):
+def getaddresses(fieldvalues, *, strict=None):
     """Return a list of (REALNAME, EMAIL) or ('','') for each fieldvalue.
 
     When parsing fails for a fieldvalue, a 2-tuple of ('', '') is returned in
@@ -158,6 +198,11 @@ def getaddresses(fieldvalues, *, strict=True):
     If strict is true, use a strict parser which rejects malformed inputs.
     """
 
+    # If default is used, it's True unless disabled
+    # by env variable or config file.
+    if strict == None:
+        strict = _use_strict_email_parsing()
+
     # If strict is true, if the resulting list of parsed addresses is greater
     # than the number of fieldvalues in the input list, a parsing error has
     # occurred and consequently a list containing a single empty 2-tuple [('',
@@ -330,7 +375,7 @@ def parsedate_to_datetime(data):
             tzinfo=datetime.timezone(datetime.timedelta(seconds=tz)))
 
 
-def parseaddr(addr, *, strict=True):
+def parseaddr(addr, *, strict=None):
     """
     Parse addr into its constituent realname and email address parts.
 
@@ -339,6 +384,11 @@ def parseaddr(addr, *, strict=True):
 
     If strict is True, use a strict parser which rejects malformed inputs.
     """
+    # If default is used, it's True unless disabled
+    # by env variable or config file.
+    if strict == None:
+        strict = _use_strict_email_parsing()
+
     if not strict:
         addrs = _AddressList(addr).addresslist
         if not addrs:
diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py
index ce36efc1b1..05ea201b68 100644
--- a/Lib/test/test_email/test_email.py
+++ b/Lib/test/test_email/test_email.py
@@ -7,6 +7,9 @@ import time
 import base64
 import unittest
 import textwrap
+import contextlib
+import tempfile
+import os
 
 from io import StringIO, BytesIO
 from itertools import chain
@@ -41,7 +44,7 @@ from email import iterators
 from email import base64mime
 from email import quoprimime
 
-from test.support import unlink, start_threads
+from test.support import unlink, start_threads, EnvironmentVarGuard, swap_attr
 from test.test_email import openfile, TestEmailBase
 
 # These imports are documented to work, but we are testing them using a
@@ -3313,6 +3316,73 @@ Foo
         # Test email.utils.supports_strict_parsing attribute
         self.assertEqual(email.utils.supports_strict_parsing, True)
 
+    def test_parsing_errors_strict_set_via_env_var(self):
+        address = 'alice@example.org )Alice('
+        empty = ('', '')
+
+        # Reset cached default value to make the function
+        # reload the config file provided below.
+        utils._cached_strict_addr_parsing = None
+
+        # Strict disabled via env variable, old behavior expected
+        with EnvironmentVarGuard() as environ:
+            environ["PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING"] = "1"
+
+            self.assertEqual(utils.getaddresses([address]),
+                             [('', 'alice@example.org'), ('', ''), ('', 'Alice')])
+            self.assertEqual(utils.parseaddr([address]), ('', address))
+
+        # Clear cache again
+        utils._cached_strict_addr_parsing = None
+
+        # Default strict=True, empty result expected
+        self.assertEqual(utils.getaddresses([address]), [empty])
+        self.assertEqual(utils.parseaddr([address]), empty)
+
+        # Clear cache again
+        utils._cached_strict_addr_parsing = None
+
+        # Empty string in env variable = strict parsing enabled (default)
+        with EnvironmentVarGuard() as environ:
+            environ["PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING"] = ""
+
+            # Default strict=True, empty result expected
+            self.assertEqual(utils.getaddresses([address]), [empty])
+            self.assertEqual(utils.parseaddr([address]), empty)
+
+    @contextlib.contextmanager
+    def _email_strict_parsing_conf(self):
+        """Context for the given email strict parsing configured in config file"""
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            filename = os.path.join(tmpdirname, 'conf.cfg')
+            with swap_attr(utils, "_EMAIL_CONFIG_FILE", filename):
+                with open(filename, 'w') as file:
+                    file.write('[email_addr_parsing]\n')
+                    file.write('PYTHON_EMAIL_DISABLE_STRICT_ADDR_PARSING = true')
+                utils._EMAIL_CONFIG_FILE = filename
+                yield
+
+    def test_parsing_errors_strict_disabled_via_config_file(self):
+        address = 'alice@example.org )Alice('
+        empty = ('', '')
+
+        # Reset cached default value to make the function
+        # reload the config file provided below.
+        utils._cached_strict_addr_parsing = None
+
+        # Strict disabled via config file, old results expected
+        with self._email_strict_parsing_conf():
+            self.assertEqual(utils.getaddresses([address]),
+                             [('', 'alice@example.org'), ('', ''), ('', 'Alice')])
+            self.assertEqual(utils.parseaddr([address]), ('', address))
+
+        # Clear cache again
+        utils._cached_strict_addr_parsing = None
+
+        # Default strict=True, empty result expected
+        self.assertEqual(utils.getaddresses([address]), [empty])
+        self.assertEqual(utils.parseaddr([address]), empty)
+
     def test_getaddresses_nasty(self):
         for addresses, expected in (
             (['"Sürname, Firstname" <to@example.com>'],
-- 
2.43.0