Added TOTP implementation and tests.

4 files changed, 115 insertions, 12 deletions

diff --git a/cryptography/hazmat/primitives/twofactor/hotp.py b/cryptography/hazmat/primitives/twofactor/hotp.py
index 80e28820..a6b01b5b 100644
--- a/cryptography/hazmat/primitives/twofactor/hotp.py
+++ b/cryptography/hazmat/primitives/twofactor/hotp.py
@@ -17,13 +17,13 @@ import struct
 
 import six
 
-from cryptography.exceptions import InvalidToken
+from cryptography.exceptions import InvalidToken, UnsupportedAlgorithm
 from cryptography.hazmat.primitives import constant_time, hmac
-from cryptography.hazmat.primitives.hashes import SHA1
+from cryptography.hazmat.primitives.hashes import SHA1, SHA256, SHA512
 
 
 class HOTP(object):
-    def __init__(self, key, length, backend):
+    def __init__(self, key, length, algorithm, backend):
 
         if len(key) < 16:
             raise ValueError("Key length has to be at least 128 bits.")
@@ -31,8 +31,13 @@ class HOTP(object):
         if length < 6 or length > 8:
             raise ValueError("Length of HOTP has to be between 6 to 8.")
 
+        if not isinstance(algorithm, (SHA1, SHA256, SHA512)):
+            raise UnsupportedAlgorithm(
+                "Algorithm must be SHA1, SHA256 or SHA512")
+
         self._key = key
         self._length = length
+        self._algorithm = algorithm
         self._backend = backend
 
     def generate(self, counter):
@@ -45,11 +50,11 @@ class HOTP(object):
             raise InvalidToken("Supplied HOTP value does not match")
 
     def _dynamic_truncate(self, counter):
-        ctx = hmac.HMAC(self._key, SHA1(), self._backend)
+        ctx = hmac.HMAC(self._key, self._algorithm, self._backend)
         ctx.update(struct.pack(">Q", counter))
         hmac_value = ctx.finalize()
 
-        offset_bits = six.indexbytes(hmac_value, 19) & 0b1111
+        offset_bits = six.indexbytes(hmac_value, len(hmac_value)-1) & 0b1111
 
         offset = int(offset_bits)
         p = hmac_value[offset:offset + 4]
diff --git a/cryptography/hazmat/primitives/twofactor/totp.py b/cryptography/hazmat/primitives/twofactor/totp.py
new file mode 100644
index 00000000..c9933d30
--- /dev/null
+++ b/cryptography/hazmat/primitives/twofactor/totp.py
@@ -0,0 +1,33 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import math
+
+from cryptography.exceptions import InvalidToken
+from cryptography.hazmat.primitives import constant_time
+from cryptography.hazmat.primitives.twofactor.hotp import HOTP
+
+
+class TOTP(object):
+    def __init__(self, key, length, algorithm, time_step, backend):
+
+        self._time_step = time_step
+        self.hotp = HOTP(key, length, algorithm, backend)
+
+    def generate(self, time):
+        counter = int(math.floor(time/self._time_step))
+        return self.hotp.generate(counter)
+
+    def verify(self, totp, time):
+        if not constant_time.bytes_eq(self.generate(time), totp):
+            raise InvalidToken("Supplied HOTP value does not match")
diff --git a/tests/hazmat/primitives/twofactor/test_hotp.py b/tests/hazmat/primitives/twofactor/test_hotp.py
index ec619b55..8f687ebb 100644
--- a/tests/hazmat/primitives/twofactor/test_hotp.py
+++ b/tests/hazmat/primitives/twofactor/test_hotp.py
@@ -15,10 +15,11 @@ import os
 
 import pytest
 
-from cryptography.exceptions import InvalidToken
+from cryptography.exceptions import InvalidToken, UnsupportedAlgorithm
 from cryptography.hazmat.primitives.twofactor.hotp import HOTP
 from cryptography.hazmat.primitives import hashes
 from tests.utils import load_vectors_from_file, load_nist_vectors
+from cryptography.hazmat.primitives.hashes import MD5, SHA1
 
 vectors = load_vectors_from_file(
     "twofactor/rfc-4226.txt", load_nist_vectors)
@@ -35,13 +36,19 @@ class TestHOTP(object):
         secret = os.urandom(10)
 
         with pytest.raises(ValueError):
-            HOTP(secret, 6, backend)
+            HOTP(secret, 6, SHA1(), backend)
 
     def test_invalid_hotp_length(self, backend):
         secret = os.urandom(16)
 
         with pytest.raises(ValueError):
-            HOTP(secret, 4, backend)
+            HOTP(secret, 4, SHA1(), backend)
+
+    def test_invalid_algorithm(self, backend):
+        secret = os.urandom(16)
+
+        with pytest.raises(UnsupportedAlgorithm):
+            HOTP(secret, 6, MD5(), backend)
 
     @pytest.mark.parametrize("params", vectors)
     def test_truncate(self, backend, params):
@@ -49,7 +56,7 @@ class TestHOTP(object):
         counter = int(params["counter"])
         truncated = params["truncated"]
 
-        hotp = HOTP(secret, 6, backend)
+        hotp = HOTP(secret, 6, SHA1(), backend)
 
         assert hotp._dynamic_truncate(counter) == int(truncated.decode(), 16)
 
@@ -59,7 +66,7 @@ class TestHOTP(object):
         counter = int(params["counter"])
         hotp_value = params["hotp"]
 
-        hotp = HOTP(secret, 6, backend)
+        hotp = HOTP(secret, 6, SHA1(), backend)
 
         assert hotp.generate(counter) == hotp_value
 
@@ -69,7 +76,7 @@ class TestHOTP(object):
         counter = int(params["counter"])
         hotp_value = params["hotp"]
 
-        hotp = HOTP(secret, 6, backend)
+        hotp = HOTP(secret, 6, SHA1(), backend)
 
         assert hotp.verify(hotp_value, counter) is None
 
@@ -77,7 +84,7 @@ class TestHOTP(object):
         secret = b"12345678901234567890"
         counter = 0
 
-        hotp = HOTP(secret, 6, backend)
+        hotp = HOTP(secret, 6, SHA1(), backend)
 
         with pytest.raises(InvalidToken):
             hotp.verify(b"123456", counter)
diff --git a/tests/hazmat/primitives/twofactor/test_totp.py b/tests/hazmat/primitives/twofactor/test_totp.py
new file mode 100644
index 00000000..0549fa59
--- /dev/null
+++ b/tests/hazmat/primitives/twofactor/test_totp.py
@@ -0,0 +1,58 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+from cryptography.exceptions import InvalidToken
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.hashes import SHA1
+from cryptography.hazmat.primitives.twofactor.totp import TOTP
+from tests.utils import load_vectors_from_file, load_nist_vectors
+
+vectors = load_vectors_from_file(
+    "twofactor/rfc-6238.txt", load_nist_vectors)
+
+@pytest.mark.hmac
+class TestTOTP(object):
+
+    @pytest.mark.parametrize("params", vectors)
+    def test_generate(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        mode = params["mode"]
+        totp_value = params["totp"]
+
+        algorithm = getattr(hashes, mode.decode())
+        totp = TOTP(secret, 8, algorithm(), 30, backend)
+        assert totp.generate(time) == totp_value
+
+    @pytest.mark.parametrize("params", vectors)
+    def test_verify(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        mode = params["mode"]
+        totp_value = params["totp"]
+
+        algorithm = getattr(hashes, mode.decode())
+        totp = TOTP(secret, 8, algorithm(), 30, backend)
+
+        assert totp.verify(totp_value, time) is None
+
+    def test_invalid_verify(self, backend):
+            secret = b"12345678901234567890"
+            time = 59
+
+            totp = TOTP(secret, 8, SHA1(), 30, backend)
+
+            with pytest.raises(InvalidToken):
+                totp.verify(b"12345678", time)