Fixed #18182 -- Made is_usable_password check if hashing algorithm is correct

The display of the ReadOnlyPasswordHashWidget has also been improved to
distinguish empty/unusable password from erroneous password.
Fixed #18453 also.
Thanks danielr and Leo for the reports and Moritz Sichert for the
initial patch.

django/contrib/auth/forms.py

@@ -11,7 +11,7 @@ from django.utils.translation import ugettext, ugettext_lazy as _
 
 from django.contrib.auth import authenticate
 from django.contrib.auth.models import User
-from django.contrib.auth.hashers import UNUSABLE_PASSWORD, is_password_usable, identify_hasher
+from django.contrib.auth.hashers import UNUSABLE_PASSWORD, identify_hasher
 from django.contrib.auth.tokens import default_token_generator
 from django.contrib.sites.models import get_current_site
 
@@ -24,16 +24,16 @@ mask_password = lambda p: "%s%s" % (p[:UNMASKED_DIGITS_TO_SHOW], "*" * max(len(p
 class ReadOnlyPasswordHashWidget(forms.Widget):
     def render(self, name, value, attrs):
         encoded = value
-
-        if not is_password_usable(encoded):
-            return "None"
-
         final_attrs = self.build_attrs(attrs)
 
+        if encoded == '' or encoded == UNUSABLE_PASSWORD:
+            summary = mark_safe("<strong>%s</strong>" % ugettext("No password set."))
+        else:
             try:
                 hasher = identify_hasher(encoded)
             except ValueError:
-            summary = mark_safe("<strong>Invalid password format or unknown hashing algorithm.</strong>")
+                summary = mark_safe("<strong>%s</strong>" % ugettext(
+                    "Invalid password format or unknown hashing algorithm."))
             else:
                 summary = format_html_join('',
                                            "<strong>{0}</strong>: {1} ",

django/contrib/auth/hashers.py

@@ -28,7 +28,13 @@ def reset_hashers(**kwargs):
 
 
 def is_password_usable(encoded):
-    return (encoded is not None and encoded != UNUSABLE_PASSWORD)
+    if encoded is None or encoded == UNUSABLE_PASSWORD:
+        return False
+    try:
+        hasher = identify_hasher(encoded)
+    except ValueError:
+        return False
+    return True
 
 
 def check_password(password, encoded, setter=None, preferred='default'):

django/contrib/auth/tests/forms.py

@@ -236,23 +236,30 @@ class UserChangeFormTest(TestCase):
         # Just check we can create it
         form = MyUserForm({})
 
+    def test_unsuable_password(self):
+        user = User.objects.get(username='empty_password')
+        user.set_unusable_password()
+        user.save()
+        form = UserChangeForm(instance=user)
+        self.assertIn(_("No password set."), form.as_table())
+
     def test_bug_17944_empty_password(self):
         user = User.objects.get(username='empty_password')
         form = UserChangeForm(instance=user)
-        # Just check that no error is raised.
-        form.as_table()
+        self.assertIn(_("Invalid password format or unknown hashing algorithm."),
+            form.as_table())
 
     def test_bug_17944_unmanageable_password(self):
         user = User.objects.get(username='unmanageable_password')
         form = UserChangeForm(instance=user)
-        # Just check that no error is raised.
-        form.as_table()
+        self.assertIn(_("Invalid password format or unknown hashing algorithm."),
+            form.as_table())
 
     def test_bug_17944_unknown_password_algorithm(self):
         user = User.objects.get(username='unknown_password')
         form = UserChangeForm(instance=user)
-        # Just check that no error is raised.
-        form.as_table()
+        self.assertIn(_("Invalid password format or unknown hashing algorithm."),
+            form.as_table())
 
 
 @override_settings(USE_TZ=False, PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))

django/contrib/auth/tests/hashers.py

@@ -100,6 +100,10 @@ class TestUtilsHashPass(unittest.TestCase):
         self.assertRaises(ValueError, doit)
         self.assertRaises(ValueError, identify_hasher, "lolcat$salt$hash")
 
+    def test_bad_encoded(self):
+        self.assertFalse(is_password_usable('letmein_badencoded'))
+        self.assertFalse(is_password_usable(''))
+
     def test_low_level_pkbdf2(self):
         hasher = PBKDF2PasswordHasher()
         encoded = hasher.encode('letmein', 'seasalt')