1 files changed, 24 insertions, 10 deletions
diff --git a/utils.py b/utils.py
index b749444..49a69d3 100644
--- a/utils.py
+++ b/utils.py
@@ -3,12 +3,16 @@ import hmac
 import ldap
 import pickle
 import re
+import struct
+import subprocess
+from base64 import urlsafe_b64encode, urlsafe_b64decode
 from Crypto.Cipher import AES
 from email.mime.text import MIMEText
 from functools import wraps
 from flask import current_app, flash, g, redirect, render_template, request, session, url_for
 from hashlib import sha1
 from random import randint
+from time import time
 from werkzeug.exceptions import Forbidden
 
 
@@ -86,7 +90,7 @@ def decrypt_password(ciphertext):
     return encryptor.decrypt(ciphertext[16:]).rstrip('\0')
 
 
-def create_confirmation(realm, data):
+def make_confirmation(realm, data):
     """
     Create a confirmation token e.g. for confirmation mails.
 
@@ -94,26 +98,36 @@ def create_confirmation(realm, data):
     some data (pickle-able).
     """
     key = '\0'.join((current_app.config['SECRET_KEY'], realm))
-    payload = pickle.dumps(data)
+    payload = ''.join((struct.pack('>i', time()), pickle.dumps(data)))
     mac = hmac.new(key, payload, sha1)
-    return ''.join((mac.digest(), payload)).encode('base64').strip()
+    return urlsafe_b64encode(''.join((mac.digest(), payload))).rstrip('=')
 
-class InvalidConfirmation(ValueError):
+class ConfirmationInvalid(ValueError):
     """Raised by `verify_confirmation` on invalid input data"""
 
-def verify_confirmation(realm, token):
+class ConfirmationTimeout(ValueError):
+    """Raised by `verify_confirmation` when the input data is too old"""
+
+def verify_confirmation(realm, token, timeout=None):
     """
-    Verify a confirmation created by `create_confirmation` and, if it is
+    Verify a confirmation token created by `make_confirmation` and, if it is
     valid, return the original data.
+    If `timeout` is given, only accept the token if it is less than `timeout`
+    seconds old.
     """
     key = '\0'.join((current_app.config['SECRET_KEY'], realm))
 
-    token = token.decode('base64')
+    token = urlsafe_b64decode(token + '=' * (4 - len(token) % 4))
     mac = token[:20]
-    payload = token[20:]
+    tokentime = struct.unpack('>i', token[20:24])[0]
+    payload = token[24:]
+
+    if mac != hmac.new(key, token[20:], sha1).digest():
+        raise ConfirmationInvalid('MAC does not match')
 
-    if mac != hmac.new(key, payload, sha1).digest():
-        raise InvalidConfirmation('MAC does not match')
+    print '%d+%d=%d <> %d' % (tokentime, timeout, tokentime+timeout, time())
+    if timeout is not None and time() > tokentime + timeout:
+        raise ConfirmationTimeout('Token is too old')
 
     return pickle.loads(payload)