Bump the default iterations for PBKDF2.

The rate at which we've increased this has not been keeping up with hardware (and software) improvements, and we're now considerably behind where we should be. The delta between our performance and an optimized implementation's performance prevents us from improving that further, but hopefully once Python 2.7.8 and 3.4+ get into more hands we can more aggressively increase this number.

django/contrib/auth/hashers.py

@@ -222,12 +222,12 @@ class PBKDF2PasswordHasher(BasePasswordHasher):
     """
     Secure password hashing using the PBKDF2 algorithm (recommended)
 
-    Configured to use PBKDF2 + HMAC + SHA256 with 12000 iterations.
+    Configured to use PBKDF2 + HMAC + SHA256 with 20000 iterations.
     The result is a 64 byte binary string.  Iterations may be changed
     safely but you must rename the algorithm if you change SHA256.
     """
     algorithm = "pbkdf2_sha256"
-    iterations = 12000
+    iterations = 20000
     digest = hashlib.sha256
 
     def encode(self, password, salt, iterations=None):

django/contrib/auth/tests/test_hashers.py

@@ -47,7 +47,7 @@ class TestUtilsHashPass(SimpleTestCase):
     def test_pkbdf2(self):
         encoded = make_password('lètmein', 'seasalt', 'pbkdf2_sha256')
         self.assertEqual(encoded,
-            'pbkdf2_sha256$12000$seasalt$Ybw8zsFxqja97tY/o6G+Fy1ksY4U/Hw3DRrGED6Up4s=')
+            'pbkdf2_sha256$20000$seasalt$oBSd886ysm3AqYun62DOdin8YcfbU1z9cksZSuLP9r0=')
         self.assertTrue(is_password_usable(encoded))
         self.assertTrue(check_password('lètmein', encoded))
         self.assertFalse(check_password('lètmeinz', encoded))
@@ -211,14 +211,14 @@ class TestUtilsHashPass(SimpleTestCase):
         hasher = PBKDF2PasswordHasher()
         encoded = hasher.encode('lètmein', 'seasalt2')
         self.assertEqual(encoded,
-            'pbkdf2_sha256$12000$seasalt2$hlDLKsxgkgb1aeOppkM5atCYw5rPzAjCNQZ4NYyUROw=')
+            'pbkdf2_sha256$20000$seasalt2$Flpve/uAcyo6+IFI6YAhjeABGPVbRQjzHDxRhqxewgw=')
         self.assertTrue(hasher.verify('lètmein', encoded))
 
     def test_low_level_pbkdf2_sha1(self):
         hasher = PBKDF2SHA1PasswordHasher()
         encoded = hasher.encode('lètmein', 'seasalt2')
         self.assertEqual(encoded,
-            'pbkdf2_sha1$12000$seasalt2$JeMRVfjjgtWw3/HzlnlfqBnQ6CA=')
+            'pbkdf2_sha1$20000$seasalt2$pJt86NmjAweBY1StBvxCu7l1o9o=')
         self.assertTrue(hasher.verify('lètmein', encoded))
 
     def test_upgrade(self):

django/utils/crypto.py

@@ -145,12 +145,14 @@ else:
 
         HMAC+SHA256 is used as the default pseudo random function.
 
-        As of 2011, 10,000 iterations was the recommended default which
+        As of 2014, 100,000 iterations was the recommended default which took
-        took 100ms on a 2.2Ghz Core 2 Duo. This is probably the bare
+        100ms on a 2.7Ghz Intel i7 with an optimized implementation. This is
-        minimum for security given 1000 iterations was recommended in
+        probably the bare minimum for security given 1000 iterations was
-        2001. This code is very well optimized for CPython and is only
+        recommended in 2001. This code is very well optimized for CPython and
-        four times slower than openssl's implementation. Look in
+        is about five times slower than OpenSSL's implementation. Look in
-        django.contrib.auth.hashers for the present default.
+        django.contrib.auth.hashers for the present default, it is lower than
+        the recommended 100,000 because of the performance difference between
+        this and an optimized implementation.
         """
         assert iterations > 0
         if not digest:

docs/internals/howto-release-django.txt

@@ -91,7 +91,7 @@ any time leading up to the actual release:
 
 #. If this is a major release, make sure the tests pass, then increase
    the default PBKDF2 iterations in
-   ``django.contrib.auth.hashers.PBKDF2PasswordHasher`` by about 10%
+   ``django.contrib.auth.hashers.PBKDF2PasswordHasher`` by about 20%
    (pick a round number). Run the tests, and update the 3 failing
    hasher tests with the new values. Make sure this gets noted in the
    release notes (see release notes on 1.6 for an example).