1 files changed, 37 insertions, 0 deletions
diff --git a/crypto.py b/crypto.py
new file mode 100644
index 0000000..3f22ccc
--- /dev/null
+++ b/crypto.py
@@ -0,0 +1,37 @@
+# coding: utf-8
+
+
+class OATHValidator(object):
+    STATUS_OK = 'OK'
+    STATUS_BAD = 'BAD'
+    STATUS_NO_AUTH = 'NO_AUTH'
+    STATUS_NO_CLIENT = 'NO_CLIENT'
+
+    def __init__(self, dbread_callback, dbwrite_callback):
+        self.dbread_callback = dbread_callback
+        self.dbwrite_callback = dbwrite_callback
+
+    def test_HOTP(self, K, C, digits=6):
+        counter = ('%s' % C).rjust(16, '0').decode('hex')
+        HS = hmac.new(K, counter, hashlib.sha1).digest()
+        offset = ord(HS[19]) & 0xF
+        bin_code = int((chr(ord(HS[offset]) & 0x7F) + HS[offset+1:offset+4]).encode('hex'), 16)
+        return str(bin_code)[-digits:]
+
+    def validate_OATH(self, OATH, publicID):
+        if len(OATH) % 2 != 0:
+            return self.STATUS_BAD
+
+        token_data = self.dbread_callback(publicID=publicID)
+        if token_data.rowcount != 1:
+            return self.STATUS_BAD
+
+        (actualcounter, key) = token_data.fetchone()
+
+        K = key.decode('hex')
+        for C in range(actualcounter + 1, actualcounter + 256):
+            if OATH == self.test_HOTP(K, C, len(OATH)):
+                self.dbwrite_callback(counter=str(C), publicID=publicID)
+                return self.STATUS_OK
+
+        return self.STATUS_NO_AUTH