Custom password hasher for SSHA

re2o/login.py

@@ -2,29 +2,89 @@
 # Module d'authentification
 # David Sinquin, Gabriel Détraz, Goulven Kermarec
 
-import hashlib, binascii
+
+import hashlib
+import binascii
 import os
-from base64 import urlsafe_b64encode as encode
-from base64 import urlsafe_b64decode as decode
+from base64 import encodestring
+from base64 import decodestring
+from collections import OrderedDict
+
+from django.contrib.auth import hashers
+
+
+ALGO_NAME = "{SSHA}"
+ALGO_LEN = len(ALGO_NAME + "$")
+DIGEST_LEN = 20
+
 
 def makeSecret(password):
     salt = os.urandom(4)
     h = hashlib.sha1(password.encode())
     h.update(salt)
-    return "{SSHA}" + encode(h.digest() + salt).decode()
+    return ALGO_NAME + "$" + encodestring(h.digest() + salt).decode()[:-1]
+
 
 def hashNT(password):
     hash = hashlib.new('md4', password.encode()).digest()
     return binascii.hexlify(hash)
 
+
 def checkPassword(challenge_password, password):
-    challenge_bytes = decode(challenge_password[6:])
-    digest = challenge_bytes[:20]
-    salt = challenge_bytes[20:]
+    challenge_bytes = decodestring(challenge_password[ALGO_LEN:].encode())
+    digest = challenge_bytes[:DIGEST_LEN]
+    salt = challenge_bytes[DIGEST_LEN:]
     hr = hashlib.sha1(password.encode())
     hr.update(salt)
     valid_password = True
-    # La comparaison est volontairement en temps constant (pour éviter les timing-attacks)
+    # La comparaison est volontairement en temps constant
+    # (pour éviter les timing-attacks)
     for i, j in zip(digest, hr.digest()):
         valid_password &= i == j
     return valid_password
+
+
+class SSHAPasswordHasher(hashers.BasePasswordHasher):
+    """
+    SSHA password hashing to allow for LDAP auth compatibility
+    """
+
+    algorithm = ALGO_NAME
+
+    def encode(self, password, salt, iterations=None):
+        """
+        Hash and salt the given password using SSHA algorithm
+
+        salt is overridden
+        """
+        assert password is not None
+        return makeSecret(password)
+
+    def verify(self, password, encoded):
+        """
+        Check password against encoded using SSHA algorithm
+        """
+        assert encoded.startswith(self.algorithm)
+        return checkPassword(encoded, password)
+
+    def safe_summary(self, encoded):
+        """
+        Provides a safe summary ofthe password
+        """
+        assert encoded.startswith(self.algorithm)
+        hash = encoded[ALGO_LEN:]
+        hash = binascii.hexlify(decodestring(hash.encode())).decode()
+        return OrderedDict([
+            ('algorithm', self.algorithm),
+            ('iterations', 0),
+            ('salt', hashers.mask_hash(hash[2*DIGEST_LEN:], show=2)),
+            ('hash', hashers.mask_hash(hash[:2*DIGEST_LEN])),
+        ])
+
+    def harden_runtime(self, password, encoded):
+        """
+        Method implemented to shut up BasePasswordHasher warning
+
+        As we are not using multiple iterations the method is pretty useless
+        """
+        pass