Index: Doc/library/base64.rst
===================================================================
--- Doc/library/base64.rst	(revision 74261)
+++ Doc/library/base64.rst	(working copy)
@@ -35,7 +35,7 @@
    The encoded string is returned.
 
 
-.. function:: b64decode(s, altchars=None)
+.. function:: b64decode(s, altchars=None, validate=False)
 
    Decode a Base64 encoded string.
 
@@ -43,11 +43,14 @@
    length 2 (additional characters are ignored) which specifies the alternative
    alphabet used instead of the ``+`` and ``/`` characters.
 
-   The decoded string is returned.  A :exc:`TypeError` is raised if *s* were
-   incorrectly padded or if there are non-alphabet characters present in the
-   string.
+   The decoded string is returned.  A `binascii.Error` is raised if *s* is
+   incorrectly padded.
 
+   If *validate* is not set to True, non-base64-alphabet characters are
+   discarded prior to the padding check, rather than rejected with a
+   :exc:`TypeError`.
 
+
 .. function:: standard_b64encode(s)
 
    Encode string *s* using the standard Base64 alphabet.
Index: Lib/base64.py
===================================================================
--- Lib/base64.py	(revision 74261)
+++ Lib/base64.py	(working copy)
@@ -5,6 +5,7 @@
 # Modified 04-Oct-1995 by Jack Jansen to use binascii module
 # Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support
 # Modified 22-May-2007 by Guido van Rossum to use bytes everywhere
+# Modified 29-Jul-2009 by Neil Tallim to support base64 validation
 
 import re
 import struct
@@ -65,16 +66,19 @@
     return encoded
 
 
-def b64decode(s, altchars=None):
+def b64decode(s, altchars=None, validate=False):
     """Decode a Base64 encoded byte string.
 
     s is the byte string to decode.  Optional altchars must be a
     string of length 2 which specifies the alternative alphabet used
     instead of the '+' and '/' characters.
-
-    The decoded byte string is returned.  binascii.Error is raised if
-    s were incorrectly padded or if there are non-alphabet characters
-    present in the string.
+    
+    The decoded string is returned.  A binascii.Error is raised if s is
+    incorrectly padded.
+    
+    If validate is not set to True, non-base64-alphabet characters are
+    discarded prior to the padding check, rather than rejected with a
+    TypeError.
     """
     if not isinstance(s, bytes_types):
         raise TypeError("expected bytes, not %s" % s.__class__.__name__)
@@ -84,6 +88,8 @@
                             % altchars.__class__.__name__)
         assert len(altchars) == 2, repr(altchars)
         s = _translate(s, {chr(altchars[0]): b'+', chr(altchars[1]): b'/'})
+    if validate and not re.match(b'^[A-Za-z0-9+/\r\n]*={0,2}$', s):
+        raise TypeError('Non-base64 digit found')
     return binascii.a2b_base64(s)
 
 
Index: Lib/test/test_base64.py
===================================================================
--- Lib/test/test_base64.py	(revision 74261)
+++ Lib/test/test_base64.py	(working copy)
@@ -137,7 +137,18 @@
         self.assertRaises(TypeError, base64.urlsafe_b64decode, "")
 
     def test_b64decode_error(self):
+        # Test padding errors.
         self.assertRaises(binascii.Error, base64.b64decode, b'abc')
+        # Test some invalid characters; addresses [1466065].
+        arr = self.assertRaisesRegexp
+        arr(TypeError, 'Non-base64 digit found', base64.b64decode, b'%3d=', None, True)
+        arr(TypeError, 'Non-base64 digit found', base64.b64decode, b'$3=', None, True)
+        arr(TypeError, 'Non-base64 digit found', base64.b64decode, b'[==', None, True)
+        arr(TypeError, 'Non-base64 digit found', base64.b64decode, b']3==', None, True)
+        arr(TypeError, 'Non-base64 digit found', base64.b64decode, b'3{=', None, True)
+        arr(TypeError, 'Non-base64 digit found', base64.b64decode, b'3d}=', None, True)
+        arr(TypeError, 'Non-base64 digit found', base64.b64decode, b'@@', None, True)
+        arr(TypeError, 'Non-base64 digit found', base64.b64decode, b'!', None, True)
 
     def test_b32encode(self):
         eq = self.assertEqual