bultin constant time checking

- if hmac.compare_digest is there, we should use it instead of our own
fallback.
- jwt handler has been updated to use utils.compare (reported in
#web2py-users)
- includes the same mods as https://github.com/web2py/web2py/pull/1146

gluon/tools.py

@@ -34,13 +34,12 @@ import email.utils
 import random
 import hmac
 import hashlib
-import json
 from email import MIMEBase, MIMEMultipart, MIMEText, Encoders, Header, message_from_string, Charset
 
 from gluon.serializers import json_parser
 from gluon.contenttype import contenttype
 from gluon.storage import Storage, StorageList, Settings, Messages
-from gluon.utils import web2py_uuid
+from gluon.utils import web2py_uuid, compare
 from gluon.fileutils import read_file, check_credentials
 from gluon import *
 from gluon.contrib.autolinks import expand_one
@@ -53,17 +52,6 @@ import gluon.serializers as serializers
 Table = DAL.Table
 Field = DAL.Field
 
-try:
-    # try stdlib (Python 2.6)
-    import json as json_parser
-except ImportError:
-    try:
-        # try external module
-        import simplejson as json_parser
-    except:
-        # fallback to pure-Python module
-        import gluon.contrib.simplejson as json_parser
-
 __all__ = ['Mail', 'Auth', 'Recaptcha', 'Recaptcha2', 'Crud', 'Service', 'Wiki',
            'PluginManager', 'fetch', 'geocode', 'reverse_geocode', 'prettydate']
 
@@ -1143,8 +1131,7 @@ def addrow(form, a, b, c, style, _id, position=-1):
 class AuthJWT(object):
 
     """
-    If left externally, this needs the usual "singleton" approach.
-    Given I (we) don't know if to include in auth yet, let's stick to basics.
+    Experimental!
 
     Args:
      - secret_key: the secret. Without salting, an attacker knowing this can impersonate
@@ -1175,7 +1162,9 @@ class AuthJWT(object):
                                return payload
      - before_authorization: can be a callable that takes the deserialized token (a dict) as input.
                              Gets called right after signature verification but before the actual
-                             authorization takes place. You can raise with HTTP a proper error message
+                             authorization takes place. It may be use to cast
+                             the extra auth_user fields to their actual types.
+                             You can raise with HTTP a proper error message
                              Example:
                              def mybefore_authorization(tokend):
                                  if not tokend['my_name_is'] == 'bond,james bond':
@@ -1256,7 +1245,7 @@ class AuthJWT(object):
     @staticmethod
     def jwt_b64e(string):
         if isinstance(string, unicode):
-            string = string.encode('uft-8', 'strict')
+            string = string.encode('utf-8', 'strict')
         return base64.urlsafe_b64encode(string).strip(b'=')
 
     @staticmethod
@@ -1279,7 +1268,7 @@ class AuthJWT(object):
             if isinstance(secret, unicode):
                 secret = secret.encode('ascii', 'ignore')
         b64h = self.cached_b64h
-        b64p = self.jwt_b64e(json_parser.dumps(payload))
+        b64p = self.jwt_b64e(serializers.json(payload))
         jbody = b64h + '.' + b64p
         mauth = hmac.new(key=secret, msg=jbody, digestmod=self.digestmod)
         jsign = self.jwt_b64e(mauth.digest())
@@ -1287,7 +1276,7 @@ class AuthJWT(object):
 
     def verify_signature(self, body, signature, secret):
         mauth = hmac.new(key=secret, msg=body, digestmod=self.digestmod)
-        return hmac.compare_digest(self.jwt_b64e(mauth.digest()), signature)
+        return compare(self.jwt_b64e(mauth.digest()), signature)
 
     def load_token(self, token):
         if isinstance(token, unicode):
@@ -1298,7 +1287,7 @@ class AuthJWT(object):
             # header not the same
             raise HTTP(400, u'Invalid JWT Header')
         secret = self.secret_key
-        tokend = json_parser.loads(self.jwt_b64d(b64b))
+        tokend = serializers.loads_json(self.jwt_b64d(b64b))
         if self.salt:
             if callable(self.salt):
                 secret = "%s$%s" % (secret, self.salt(tokend))
@@ -1380,6 +1369,7 @@ class AuthJWT(object):
         response = current.response
         session = current.session
         # forget and unlock response
+        valid_user = None
         if request.vars.token:
             if not self.allow_refresh:
                 raise HTTP(403, u'Refreshing token is not allowed')
@@ -1387,24 +1377,24 @@ class AuthJWT(object):
             tokend = self.load_token(token)
             # verification can fail here
             refreshed = self.refresh_token(tokend)
-            ret = {'token':self.generate_token(refreshed)}
+            ret = {'token': self.generate_token(refreshed)}
         elif self.user_param in request.vars and self.pass_param in request.vars:
             session.forget(response)
             username = request.vars[self.user_param]
             password = request.vars[self.pass_param]
             valid_user = self.auth.login_bare(username, password)
-            if valid_user:
-                payload = self.serialize_auth_session(current.session.auth)
-                self.alter_payload(payload)
-                ret = {'token':self.generate_token(payload)}
-            else:
-                raise HTTP(
-                    401, u'Not Authorized', 
-                    **{'WWW-Authenticate': u'JWT realm="%s"' % self.realm})
         else:
-            raise HTTP(400, u'Must pass token for refresh or username and password for login')
+            valid_user = self.auth.user
+        if valid_user:
+            payload = self.serialize_auth_session(current.session.auth)
+            self.alter_payload(payload)
+            ret = {'token': self.generate_token(payload)}
+        else:
+            raise HTTP(
+                401, u'Not Authorized - need to be logged in, to pass a token for refresh or username and password for login',
+                **{'WWW-Authenticate': u'JWT realm="%s"' % self.realm})
         response.headers['content-type'] = 'application/json'
-        return json.dumps(ret)
+        return serializers.json(ret)
 
     def inject_token(self, tokend):
         """

gluon/utils.py

@@ -64,6 +64,10 @@ else:
         except (ImportError, ValueError):
             HAVE_PBKDF2 = False
 
+HAVE_COMPARE_DIGEST = False
+if hasattr(hmac, 'compare_digest'):
+    HAVE_COMPARE_DIGEST = True
+
 logger = logging.getLogger("web2py")
 
 
@@ -77,6 +81,8 @@ def AES_new(key, IV=None):
 
 def compare(a, b):
     """ Compares two strings and not vulnerable to timing attacks """
+    if HAVE_COMPARE_DIGEST:
+        return hmac.compare_digest(a, b)
     if len(a) != len(b):
         return False
     result = 0
@@ -143,6 +149,7 @@ DIGEST_ALG_BY_SIZE = {
     512 / 4: 'sha512',
 }
 
+
 def get_callable_argspec(fn):
     if inspect.isfunction(fn) or inspect.ismethod(fn):
         inspectable = fn
@@ -154,6 +161,7 @@ def get_callable_argspec(fn):
         inspectable = fn
     return inspect.getargspec(inspectable)
 
+
 def pad(s, n=32, padchar=' '):
     return s + (32 - len(s) % 32) * padchar
 
@@ -172,7 +180,7 @@ def secure_dumps(data, encryption_key, hash_key=None, compression_level=None):
 
 
 def secure_loads(data, encryption_key, hash_key=None, compression_level=None):
-    if not ':' in data:
+    if ':' not in data:
         return None
     if not hash_key:
         hash_key = sha1(encryption_key).hexdigest()