Use unicode passwords when validating

Requiring that up front lets us properly validate length and such.

common/djangoapps/util/password_policy_validators.py

@@ -160,6 +160,12 @@ def validate_password(password, user=None, username=None):
         user: A User model object, if available. Required to check against security policy.
         username: The user-provided username, if available. Taken from 'user' if not provided.
     """
+    if not isinstance(password, text_type):
+        try:
+            password = text_type(password, encoding='utf8')  # some checks rely on unicode semantics (e.g. length)
+        except UnicodeDecodeError:
+            raise ValidationError(_('Invalid password.'))  # no reason to get into weeds
+
     username = username or (user and user.username)
 
     if user:
@@ -308,7 +314,7 @@ def _validate_password_dictionary(value):
 
     if password_max_edit_distance and password_dictionary:
         for word in password_dictionary:
-            edit_distance = distance(text_type(value), text_type(word))
+            edit_distance = distance(value, text_type(word))
             if edit_distance <= password_max_edit_distance:
                 raise ValidationError(_("Password is too similar to a dictionary word."),
                                       code="dictionary_word")

common/djangoapps/util/tests/test_password_policy_validators.py

@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 """Tests for util.password_policy_validators module."""
 
 import mock
@@ -8,7 +9,9 @@ from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.test.utils import override_settings
 
-from util.password_policy_validators import password_instructions, validate_password, _validate_password_dictionary
+from util.password_policy_validators import (
+    password_instructions, password_min_length, validate_password, _validate_password_dictionary
+)
 
 
 @ddt
@@ -22,18 +25,38 @@ class PasswordPolicyValidatorsTestCase(unittest.TestCase):
         """ Tests dictionary checks """
         # Direct match
         with self.assertRaises(ValidationError):
-            _validate_password_dictionary('testme')
+            _validate_password_dictionary(u'testme')
 
         # Off by one
         with self.assertRaises(ValidationError):
-            _validate_password_dictionary('estme')
+            _validate_password_dictionary(u'estme')
 
         # Off by two
         with self.assertRaises(ValidationError):
-            _validate_password_dictionary('bestmet')
+            _validate_password_dictionary(u'bestmet')
 
         # Off by three (should pass)
-        _validate_password_dictionary('bestem')
+        _validate_password_dictionary(u'bestem')
+
+    def test_unicode_password(self):
+        """ Tests that validate_password enforces unicode """
+        byte_str = b'𤭮'
+        unicode_str = u'𤭮'
+
+        # Sanity checks and demonstration of why this test is useful
+        self.assertEqual(len(byte_str), 4)
+        self.assertEqual(len(unicode_str), 1)
+        self.assertEqual(password_min_length(), 2)
+
+        # Test length check
+        with self.assertRaises(ValidationError):
+            validate_password(byte_str)
+        validate_password(byte_str + byte_str)
+
+        # Test badly encoded password
+        with self.assertRaises(ValidationError) as cm:
+            validate_password(b'\xff\xff')
+        self.assertEquals('Invalid password.', cm.exception.message)
 
     @data(
         (u'', 'at least 2 characters & 2 letters & 1 number.'),