Merge pull request #689 from dreid/twofactor-cleanup

Cleanup twofactor docs and code.

1 files changed, 35 insertions, 31 deletions

diff --git a/docs/hazmat/primitives/twofactor.rst b/docs/hazmat/primitives/twofactor.rst
index 06be151e..3df1a147 100644
--- a/docs/hazmat/primitives/twofactor.rst
+++ b/docs/hazmat/primitives/twofactor.rst
@@ -19,8 +19,8 @@ codes (HMAC).
 
     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.
+    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`.
 
@@ -45,44 +45,48 @@ codes (HMAC).
     :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()`.
+    :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)
 
-        :param int counter: The counter value used to generate the one time password.
+        :param int counter: The counter value used to generate the one time
+            password.
         :return bytes: A one time password value.
 
     .. method:: verify(hotp, counter)
 
         :param bytes hotp: The one time password value to validate.
         :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.
+        :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
-validates the token implement a throttling scheme that locks out the account for a period of
-time after a number of failed attempts. The number of allowed attempts should be as low as
-possible while still ensuring that usability is not significantly impacted.
+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 validates the token implement a throttling scheme that
+locks out the account for a period of time after a number of failed attempts.
+The number of allowed attempts should be as low as 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.
-This can lead to the counter value being out of synchronization between the client and server.
+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. This can lead to the counter value being out of
+synchronization between the client and server.
 
-Due to this, it is highly recommended that the server sets a look-ahead window that allows the
-server to calculate the next ``x`` HOTP values and check them against the supplied HOTP value.
-This can be accomplished with something similar to the following code.
+Due to this, it is highly recommended that the server sets a look-ahead window
+that allows the server to calculate the next ``x`` HOTP values and check them
+against the supplied HOTP value. This can be accomplished with something
+similar to the following code.
 
 .. code-block:: python
 
@@ -91,7 +95,7 @@ This can be accomplished with something similar to the following code.
         correct_counter = None
 
         otp = HOTP(key, 6, default_backend())
-        for count in range(counter, counter+look_ahead):
+        for count in range(counter, counter + look_ahead):
             try:
                 otp.verify(hotp, count)
                 correct_counter = count
@@ -136,12 +140,12 @@ This can be accomplished with something similar to the following code.
     :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()`.
+    :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)
 
@@ -152,5 +156,5 @@ This can be accomplished with something similar to the following code.
 
         :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.
+        :raises cryptography.exceptions.InvalidToken: This is raised when the
+            supplied TOTP does not match the expected TOTP.