Merge pull request #637 from Ayrx/totp-impl

TOTP Implementation

5 files changed, 268 insertions, 33 deletions

diff --git a/cryptography/hazmat/primitives/twofactor/hotp.py b/cryptography/hazmat/primitives/twofactor/hotp.py
index 80e28820..e806c7ef 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..be84b477
--- /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.
+
+from __future__ import absolute_import, division, print_function
+
+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(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 TOTP value does not match")
diff --git a/docs/hazmat/primitives/twofactor.rst b/docs/hazmat/primitives/twofactor.rst
index 9d661612..06be151e 100644
--- a/docs/hazmat/primitives/twofactor.rst
+++ b/docs/hazmat/primitives/twofactor.rst
@@ -13,13 +13,13 @@ codes (HMAC).
 
 .. currentmodule:: cryptography.hazmat.primitives.twofactor.hotp
 
-.. class:: HOTP(key, length, backend)
+.. class:: HOTP(key, length, algorithm, backend)
 
     .. versionadded:: 0.3
 
-    HOTP objects take a ``key`` and ``length`` parameter. The ``key``
-    should be randomly generated bytes and is recommended to be 160 bits in
-    length. The ``length`` parameter controls the length of the generated
+    HOTP objects take a ``key``, ``length`` and ``algorithm`` parameter. The
+    ``key`` should be randomly generated bytes and is recommended to be 160
+    bits in length. The ``length`` parameter controls the length of the generated
     one time password and must be >= 6 and <= 8.
 
     This is an implementation of :rfc:`4226`.
@@ -29,23 +29,28 @@ codes (HMAC).
         >>> import os
         >>> from cryptography.hazmat.backends import default_backend
         >>> from cryptography.hazmat.primitives.twofactor.hotp import HOTP
-
-        >>> key = b"12345678901234567890"
-        >>> hotp = HOTP(key, 6, backend=default_backend())
-        >>> hotp.generate(0)
-        '755224'
-        >>> hotp.verify(b"755224", 0)
-
-    :param bytes key: Secret key as ``bytes``. This value must be generated in a
-                      cryptographically secure fashion and be at least 128 bits.
-                      It is recommended that the key be 160 bits.
+        >>> from cryptography.hazmat.primitives.hashes import SHA1
+        >>> key = os.urandom(16)
+        >>> hotp = HOTP(key, 6, SHA1(), backend=default_backend())
+        >>> hotp_value = hotp.generate(0)
+        >>> hotp.verify(hotp_value, 0)
+
+    :param bytes key: Per-user secret key. This value must be kept secret
+                      and be at least 128 bits. It is recommended that the
+                      key be 160 bits.
     :param int length: Length of generated one time password as ``int``.
+    :param HashAlgorithm algorithm: A
+        :class:`~cryptography.hazmat.primitives.hashes`
+        provider.
     :param backend: A
         :class:`~cryptography.hazmat.backends.interfaces.HMACBackend`
         provider.
-    :raises ValueError: This is raised if the provided ``key`` is shorter 128 bits
-                        or if the ``length`` parameter is not between 6 to 8.
-
+    :raises ValueError: This is raised if the provided ``key`` is shorter than 128 bits
+                        or if the ``length`` parameter is not 6, 7 or 8.
+    :raises UnsupportedAlgorithm: This is raised if the provided ``algorithm`` is not
+                                  :class:`~cryptography.hazmat.primitives.hashes.SHA1()`,
+                                  :class:`~cryptography.hazmat.primitives.hashes.SHA256()`
+                                  or :class:`~cryptography.hazmat.primitives.hashes.SHA512()`.
 
     .. method:: generate(counter)
 
@@ -55,12 +60,12 @@ codes (HMAC).
     .. method:: verify(hotp, counter)
 
         :param bytes hotp: The one time password value to validate.
-        :param bytes counter: The counter value to validate against.
+        :param int counter: The counter value to validate against.
         :raises cryptography.exceptions.InvalidToken: This is raised when the supplied HOTP
                                                       does not match the expected HOTP.
 
 Throttling
-----------
+~~~~~~~~~~
 
 Due to the fact that the HOTP algorithm generates rather short tokens that are 6 - 8 digits
 long, brute force attacks are possible. It is highly recommended that the server that
@@ -69,7 +74,7 @@ time after a number of failed attempts. The number of allowed attempts should be
 possible while still ensuring that usability is not significantly impacted.
 
 Re-synchronization of the Counter
----------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 The server's counter value should only be incremented on a successful HOTP authentication.
 However, the counter on the client is incremented every time a new HOTP value is requested.
@@ -93,4 +98,59 @@ This can be accomplished with something similar to the following code.
             except InvalidToken:
                 pass
 
-        return correct_counter
\ No newline at end of file
+        return correct_counter
+
+.. currentmodule:: cryptography.hazmat.primitives.twofactor.totp
+
+.. class:: TOTP(key, length, algorithm, time_step, backend)
+
+    TOTP objects take a ``key``, ``length``, ``algorithm`` and ``time_step``
+    parameter. The ``key`` should be randomly generated bytes and is recommended
+    to be as long as your hash function's output (e.g 256-bit for SHA256).
+    The ``length`` parameter controls the length of the generated one time
+    password and must be >= 6 and <= 8.
+
+    This is an implementation of :rfc:`6238`.
+
+    .. doctest::
+
+        >>> import os
+        >>> import time
+        >>> from cryptography.hazmat.backends import default_backend
+        >>> from cryptography.hazmat.primitives.twofactor.totp import TOTP
+        >>> from cryptography.hazmat.primitives.hashes import SHA1
+        >>> key = os.urandom(16)
+        >>> totp = TOTP(key, 8, SHA1(), 30, backend=default_backend())
+        >>> time_value = time.time()
+        >>> totp_value = totp.generate(time_value)
+        >>> totp.verify(totp_value, time_value)
+
+    :param bytes key: Per-user secret key. This value must be kept secret
+                      and be at least 128 bits. It is recommended that the
+                      key be 160 bits.
+    :param int length: Length of generated one time password as ``int``.
+    :param HashAlgorithm algorithm: A
+        :class:`~cryptography.hazmat.primitives.hashes`
+        provider.
+    :param int time_step: The time step size. The recommended size is 30.
+    :param backend: A
+        :class:`~cryptography.hazmat.backends.interfaces.HMACBackend`
+        provider.
+    :raises ValueError: This is raised if the provided ``key`` is shorter than 128 bits
+                        or if the ``length`` parameter is not 6, 7 or 8.
+    :raises UnsupportedAlgorithm: This is raised if the provided ``algorithm`` is not
+                                  :class:`~cryptography.hazmat.primitives.hashes.SHA1()`,
+                                  :class:`~cryptography.hazmat.primitives.hashes.SHA256()`
+                                  or :class:`~cryptography.hazmat.primitives.hashes.SHA512()`.
+
+    .. method:: generate(time)
+
+        :param int time: The time value used to generate the one time password.
+        :return bytes: A one time password value.
+
+    .. method:: verify(totp, time)
+
+        :param bytes totp: The one time password value to validate.
+        :param int time: The time value to validate against.
+        :raises cryptography.exceptions.InvalidToken: This is raised when the supplied TOTP
+                                                      does not match the expected TOTP.
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..8877a70a
--- /dev/null
+++ b/tests/hazmat/primitives/twofactor/test_totp.py
@@ -0,0 +1,130 @@
+# 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.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.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA1()),
+        skip_message="Does not support HMAC-SHA1."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA1"])
+    def test_generate_sha1(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA1(), 30, backend)
+        assert totp.generate(time) == totp_value
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA256()),
+        skip_message="Does not support HMAC-SHA256."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA256"])
+    def test_generate_sha256(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA256(), 30, backend)
+        assert totp.generate(time) == totp_value
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA512()),
+        skip_message="Does not support HMAC-SHA512."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA512"])
+    def test_generate_sha512(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA512(), 30, backend)
+        assert totp.generate(time) == totp_value
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA1()),
+        skip_message="Does not support HMAC-SHA1."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA1"])
+    def test_verify_sha1(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA1(), 30, backend)
+
+        assert totp.verify(totp_value, time) is None
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA256()),
+        skip_message="Does not support HMAC-SHA256."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA256"])
+    def test_verify_sha256(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA256(), 30, backend)
+
+        assert totp.verify(totp_value, time) is None
+
+    @pytest.mark.supported(
+        only_if=lambda backend: backend.hmac_supported(hashes.SHA512()),
+        skip_message="Does not support HMAC-SHA512."
+    )
+    @pytest.mark.parametrize(
+        "params", [i for i in vectors if i["mode"] == b"SHA512"])
+    def test_verify_sha512(self, backend, params):
+        secret = params["secret"]
+        time = int(params["time"])
+        totp_value = params["totp"]
+
+        totp = TOTP(secret, 8, hashes.SHA512(), 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, hashes.SHA1(), 30, backend)
+
+        with pytest.raises(InvalidToken):
+            totp.verify(b"12345678", time)
+
+    def test_floating_point_time_generate(self, backend):
+        secret = b"12345678901234567890"
+        time = 59.1
+
+        totp = TOTP(secret, 8, hashes.SHA1(), 30, backend)
+
+        assert totp.generate(time) == b"94287082"