From 239e41f7c551308cea64561eed43ef2e81b60370 Mon Sep 17 00:00:00 2001
From: Paul McMillan <Paul@McMillan.ws>
Date: Thu, 23 Feb 2012 21:39:12 +0000
Subject: [PATCH] Cleanup to use get_random_string consistently.

Removes several ad hoc implementations of get_random_string()
and removes an innapropriate use of settings.SECRET_KEY.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@17580 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/contrib/sessions/backends/base.py      | 29 +++++--------------
 .../core/management/commands/startproject.py  |  5 ++--
 django/utils/crypto.py                        | 14 +++++----
 3 files changed, 18 insertions(+), 30 deletions(-)

diff --git a/django/contrib/sessions/backends/base.py b/django/contrib/sessions/backends/base.py
index 2d45e71f1c..5a637e24d2 100644
--- a/django/contrib/sessions/backends/base.py
+++ b/django/contrib/sessions/backends/base.py
@@ -1,7 +1,4 @@
 import base64
-import hashlib
-import os
-import random
 import time
 from datetime import datetime, timedelta
 try:
@@ -11,16 +8,11 @@ except ImportError:
 
 from django.conf import settings
 from django.core.exceptions import SuspiciousOperation
-from django.utils.crypto import constant_time_compare, salted_hmac
+from django.utils.crypto import constant_time_compare
+from django.utils.crypto import get_random_string
+from django.utils.crypto import salted_hmac
 from django.utils import timezone
 
-# Use the system (hardware-based) random number generator if it exists.
-if hasattr(random, 'SystemRandom'):
-    randrange = random.SystemRandom().randrange
-else:
-    randrange = random.randrange
-MAX_SESSION_KEY = 18446744073709551616L     # 2 << 63
-
 class CreateError(Exception):
     """
     Used internally as a consistent exception type to catch from save (see the
@@ -138,17 +130,12 @@ class SessionBase(object):
 
     def _get_new_session_key(self):
         "Returns session key that isn't being used."
-        # The random module is seeded when this Apache child is created.
-        # Use settings.SECRET_KEY as added salt.
-        try:
-            pid = os.getpid()
-        except AttributeError:
-            # No getpid() in Jython, for example
-            pid = 1
+        # Todo: move to 0-9a-z charset in 1.5
+        hex_chars = '1234567890abcdef'
+        # session_key should not be case sensitive because some backends
+        # can store it on case insensitive file systems.
         while True:
-            session_key = hashlib.md5("%s%s%s%s"
-                    % (randrange(0, MAX_SESSION_KEY), pid, time.time(),
-                       settings.SECRET_KEY)).hexdigest()
+            session_key = get_random_string(32, hex_chars)
             if not self.exists(session_key):
                 break
         return session_key
diff --git a/django/core/management/commands/startproject.py b/django/core/management/commands/startproject.py
index c849ab69c3..a1a9b33a43 100644
--- a/django/core/management/commands/startproject.py
+++ b/django/core/management/commands/startproject.py
@@ -1,7 +1,6 @@
-from random import choice
-
 from django.core.management.base import CommandError
 from django.core.management.templates import TemplateCommand
+from django.utils.crypto import get_random_string
 from django.utils.importlib import import_module
 
 
@@ -27,6 +26,6 @@ class Command(TemplateCommand):
 
         # Create a random SECRET_KEY hash to put it in the main settings.
         chars = 'abcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*(-_=+)'
-        options['secret_key'] = ''.join([choice(chars) for i in range(50)])
+        options['secret_key'] = get_random_string(50, chars)
 
         super(Command, self).handle('project', project_name, target, **options)
diff --git a/django/utils/crypto.py b/django/utils/crypto.py
index 4fe11f428c..a54c455e1b 100644
--- a/django/utils/crypto.py
+++ b/django/utils/crypto.py
@@ -7,6 +7,13 @@ import struct
 import hashlib
 import binascii
 import operator
+
+import random
+try:
+    random = random.SystemRandom()
+except NotImplementedError:
+    pass
+
 from django.conf import settings
 
 
@@ -43,13 +50,8 @@ def get_random_string(length=12,
     Returns a random string of length characters from the set of a-z, A-Z, 0-9.
 
     The default length of 12 with the a-z, A-Z, 0-9 character set returns
-    a 71-bit salt. log_2((26+26+10)^12) =~ 71 bits
+    a 71-bit value. log_2((26+26+10)^12) =~ 71 bits
     """
-    import random
-    try:
-        random = random.SystemRandom()
-    except NotImplementedError:
-        pass
     return ''.join([random.choice(allowed_chars) for i in range(length)])