[2.7] bpo-34155: Dont parse domains containing @ (GH-13079) (GH-16006)

This change skips parsing of email addresses where domains include a "@" character, which can be maliciously used since the local part is returned as a complete address. 

(cherry picked from commit 8cb65d1)

Excludes changes to Lib/email/_header_value_parser.py, which did not
exist in 2.7.

Co-authored-by: jpic <[email protected]>


https://bugs.python.org/issue34155

Author: rcsanchez97

Lib/email/_parseaddr.py

@@ -336,7 +336,12 @@ def getaddrspec(self):
         aslist.append('@')
         self.pos += 1
         self.gotonext()
-        return EMPTYSTRING.join(aslist) + self.getdomain()
+        domain = self.getdomain()
+        if not domain:
+            # Invalid domain, return an empty address instead of returning a
+            # local part to denote failed parsing.
+            return EMPTYSTRING
+        return EMPTYSTRING.join(aslist) + domain
 
     def getdomain(self):
         """Get the complete domain name from an address."""
@@ -351,6 +356,10 @@ def getdomain(self):
             elif self.field[self.pos] == '.':
                 self.pos += 1
                 sdlist.append('.')
+            elif self.field[self.pos] == '@':
+                # bpo-34155: Don't parse domains with two `@` like
+                # `[email protected]@important.com`.
+                return EMPTYSTRING
             elif self.field[self.pos] in self.atomends:
                 break
             else:

Lib/email/test/test_email.py

@@ -2306,6 +2306,20 @@ def test_parseaddr_empty(self):
         self.assertEqual(Utils.parseaddr('<>'), ('', ''))
         self.assertEqual(Utils.formataddr(Utils.parseaddr('<>')), '')
 
+    def test_parseaddr_multiple_domains(self):
+        self.assertEqual(
+            Utils.parseaddr('a@b@c'),
+            ('', '')
+        )
+        self.assertEqual(
+            Utils.parseaddr('[email protected]@c'),
+            ('', '')
+        )
+        self.assertEqual(
+            Utils.parseaddr('[email protected]@c'),
+            ('', '')
+        )
+
     def test_noquote_dump(self):
         self.assertEqual(
             Utils.formataddr(('A Silly Person', '[email protected]')),

Misc/NEWS.d/next/Security/2019-05-04-13-33-37.bpo-34155.MJll68.rst

@@ -0,0 +1 @@
+Fix parsing of invalid email addresses with more than one ``@`` (e.g. a@[email protected].) to not return the part before 2nd ``@`` as valid email address. Patch by maxking & jpic.