[3.0.x] Fixed #31784 -- Fixed crash when sending emails on Python 3.6.11+, 3.7.8+, and 3.8.4+.

Fixed sending emails crash on email addresses with display names longer
then 75 chars on Python 3.6.11+, 3.7.8+, and 3.8.4+.

Wrapped display names were passed to email.headerregistry.Address()
what caused raising an exception because address parts cannot contain
CR or LF.

See https://bugs.python.org/issue39073

Co-Authored-By: Mariusz Felisiak <felisiak.mariusz@gmail.com>

Backport of 96a3ea39ef0790dbc413dde0a3e19f6a769356a2 from master

4 files changed, 63 insertions, 11 deletions

diff --git a/django/core/mail/message.py b/django/core/mail/message.py
index 607eb4af0b..963542cd62 100644
--- a/django/core/mail/message.py
+++ b/django/core/mail/message.py
@@ -10,7 +10,7 @@ from email.mime.base import MIMEBase
 from email.mime.message import MIMEMessage
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
-from email.utils import formatdate, getaddresses, make_msgid
+from email.utils import formataddr, formatdate, getaddresses, make_msgid
 from io import BytesIO, StringIO
 from pathlib import Path
 
@@ -96,16 +96,24 @@ def sanitize_address(addr, encoding):
         nm, address = addr
         localpart, domain = address.rsplit('@', 1)
 
-    nm = Header(nm, encoding).encode()
+    address_parts = nm + localpart + domain
+    if '\n' in address_parts or '\r' in address_parts:
+        raise ValueError('Invalid address; address parts cannot contain newlines.')
+
     # Avoid UTF-8 encode, if it's possible.
     try:
+        nm.encode('ascii')
+        nm = Header(nm).encode()
+    except UnicodeEncodeError:
+        nm = Header(nm, encoding).encode()
+    try:
         localpart.encode('ascii')
     except UnicodeEncodeError:
         localpart = Header(localpart, encoding).encode()
     domain = punycode(domain)
 
-    parsed_address = Address(nm, username=localpart, domain=domain)
-    return str(parsed_address)
+    parsed_address = Address(username=localpart, domain=domain)
+    return formataddr((nm, parsed_address.addr_spec))
 
 
 class MIMEMixin:
diff --git a/docs/releases/2.2.15.txt b/docs/releases/2.2.15.txt
index df26962029..d8ed58b596 100644
--- a/docs/releases/2.2.15.txt
+++ b/docs/releases/2.2.15.txt
@@ -4,10 +4,13 @@ Django 2.2.15 release notes
 
 *Expected August 3, 2020*
 
-Django 2.2.15 fixes a bug in 2.2.14.
+Django 2.2.15 fixes two bugs in 2.2.14.
 
 Bugfixes
 ========
 
 * Allowed setting the ``SameSite`` cookie flag in
   :meth:`.HttpResponse.delete_cookie` (:ticket:`31790`).
+
+* Fixed crash when sending emails to addresses with display names longer than
+  75 chars on Python 3.6.11+, 3.7.8+, and 3.8.4+ (:ticket:`31784`).
diff --git a/docs/releases/3.0.9.txt b/docs/releases/3.0.9.txt
index 36bcf4546f..65310384ec 100644
--- a/docs/releases/3.0.9.txt
+++ b/docs/releases/3.0.9.txt
@@ -11,3 +11,6 @@ Bugfixes
 
 * Allowed setting the ``SameSite`` cookie flag in
   :meth:`.HttpResponse.delete_cookie` (:ticket:`31790`).
+
+* Fixed crash when sending emails to addresses with display names longer than
+  75 chars on Python 3.6.11+, 3.7.8+, and 3.8.4+ (:ticket:`31784`).
diff --git a/tests/mail/tests.py b/tests/mail/tests.py
index 6de819965a..accdba5e4a 100644
--- a/tests/mail/tests.py
+++ b/tests/mail/tests.py
@@ -722,14 +722,14 @@ class MailTests(HeadersCheckMixin, SimpleTestCase):
             (
                 ('A name', 'to@example.com'),
                 'utf-8',
-                '=?utf-8?q?A_name?= <to@example.com>',
+                'A name <to@example.com>',
             ),
             ('localpartonly', 'ascii', 'localpartonly'),
             # ASCII addresses with display names.
             ('A name <to@example.com>', 'ascii', 'A name <to@example.com>'),
-            ('A name <to@example.com>', 'utf-8', '=?utf-8?q?A_name?= <to@example.com>'),
+            ('A name <to@example.com>', 'utf-8', 'A name <to@example.com>'),
             ('"A name" <to@example.com>', 'ascii', 'A name <to@example.com>'),
-            ('"A name" <to@example.com>', 'utf-8', '=?utf-8?q?A_name?= <to@example.com>'),
+            ('"A name" <to@example.com>', 'utf-8', 'A name <to@example.com>'),
             # Unicode addresses (supported per RFC-6532).
             ('tó@example.com', 'utf-8', '=?utf-8?b?dMOz?=@example.com'),
             ('to@éxample.com', 'utf-8', 'to@xn--xample-9ua.com'),
@@ -748,20 +748,45 @@ class MailTests(HeadersCheckMixin, SimpleTestCase):
             (
                 'To Example <to@éxample.com>',
                 'utf-8',
-                '=?utf-8?q?To_Example?= <to@xn--xample-9ua.com>',
+                'To Example <to@xn--xample-9ua.com>',
             ),
             # Addresses with two @ signs.
             ('"to@other.com"@example.com', 'utf-8', r'"to@other.com"@example.com'),
             (
                 '"to@other.com" <to@example.com>',
                 'utf-8',
-                '=?utf-8?q?to=40other=2Ecom?= <to@example.com>',
+                '"to@other.com" <to@example.com>',
             ),
             (
                 ('To Example', 'to@other.com@example.com'),
                 'utf-8',
-                '=?utf-8?q?To_Example?= <"to@other.com"@example.com>',
+                'To Example <"to@other.com"@example.com>',
+            ),
+            # Addresses with long unicode display names.
+            (
+                'Tó Example very long' * 4 + ' <to@example.com>',
+                'utf-8',
+                '=?utf-8?q?T=C3=B3_Example_very_longT=C3=B3_Example_very_longT'
+                '=C3=B3_Example_?=\n'
+                ' =?utf-8?q?very_longT=C3=B3_Example_very_long?= '
+                '<to@example.com>',
+            ),
+            (
+                ('Tó Example very long' * 4, 'to@example.com'),
+                'utf-8',
+                '=?utf-8?q?T=C3=B3_Example_very_longT=C3=B3_Example_very_longT'
+                '=C3=B3_Example_?=\n'
+                ' =?utf-8?q?very_longT=C3=B3_Example_very_long?= '
+                '<to@example.com>',
             ),
+            # Address with long display name and unicode domain.
+            (
+                ('To Example very long' * 4, 'to@exampl€.com'),
+                'utf-8',
+                'To Example very longTo Example very longTo Example very longT'
+                'o Example very\n'
+                ' long <to@xn--exampl-nc1c.com>'
+            )
         ):
             with self.subTest(email_address=email_address, encoding=encoding):
                 self.assertEqual(sanitize_address(email_address, encoding), expected_result)
@@ -781,6 +806,19 @@ class MailTests(HeadersCheckMixin, SimpleTestCase):
                 with self.assertRaises(ValueError):
                     sanitize_address(email_address, encoding='utf-8')
 
+    def test_sanitize_address_header_injection(self):
+        msg = 'Invalid address; address parts cannot contain newlines.'
+        tests = [
+            'Name\nInjection <to@example.com>',
+            ('Name\nInjection', 'to@xample.com'),
+            'Name <to\ninjection@example.com>',
+            ('Name', 'to\ninjection@example.com'),
+        ]
+        for email_address in tests:
+            with self.subTest(email_address=email_address):
+                with self.assertRaisesMessage(ValueError, msg):
+                    sanitize_address(email_address, encoding='utf-8')
+
 
 @requires_tz_support
 class MailTimeZoneTests(SimpleTestCase):