Merge branch 'master' into urandom-engine

* master: (108 commits)
  PBKDF2HMAC requires a PBKDF2HMACBackend provider.
  one more replacement
  simplify hmac supported and hash supported calls for commoncrypto
  simplify check for algorithm
  a bit more language work + changelog changes for pbkdf2hmac
  one more style fix
  a few typo fixes, capitalization, etc
  switch to private attributes in pbkdf2hmac
  expand docs to talk more about the purposes of KDFs
  update docs re: PBKDF2HMAC iterations
  add test for null char replacement
  Added installation section to index.rst
  called -> used
  quotes inside, diff examples
  Expose this method because probably someone will need it eventually
  fix spacing, remove versionadded since HashAlgorithm was in 0.1
  document HashAlgorithm
  Added canonical installation document with details about various platforms, fixes #519
  update docs for pbkdf2
  Add bindings for X509_REQ_get_extensions.
  ...

Conflicts:
	cryptography/hazmat/bindings/openssl/binding.py
	docs/hazmat/backends/openssl.rst

1 files changed, 45 insertions, 4 deletions

diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index 11e2f2a2..49e4c88c 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -37,7 +37,7 @@ A specific ``backend`` may provide one or more of these interfaces.
     .. method:: create_symmetric_encryption_ctx(cipher, mode)
 
         Create a
-        :class:`~cryptogrpahy.hazmat.primitives.interfaces.CipherContext` that
+        :class:`~cryptography.hazmat.primitives.interfaces.CipherContext` that
         can be used for encrypting data with the symmetric ``cipher`` using
         the given ``mode``.
 
@@ -56,7 +56,7 @@ A specific ``backend`` may provide one or more of these interfaces.
     .. method:: create_symmetric_decryption_ctx(cipher, mode)
 
         Create a
-        :class:`~cryptogrpahy.hazmat.primitives.interfaces.CipherContext` that
+        :class:`~cryptography.hazmat.primitives.interfaces.CipherContext` that
         can be used for decrypting data with the symmetric ``cipher`` using
         the given ``mode``.
 
@@ -91,7 +91,7 @@ A specific ``backend`` may provide one or more of these interfaces.
     .. method:: create_hash_ctx(algorithm)
 
         Create a
-        :class:`~cryptogrpahy.hazmat.primitives.interfaces.HashContext` that
+        :class:`~cryptography.hazmat.primitives.interfaces.HashContext` that
         uses the specified ``algorithm`` to calculate a message digest.
 
         :param algorithm: An instance of a
@@ -121,7 +121,7 @@ A specific ``backend`` may provide one or more of these interfaces.
     .. method:: create_hmac_ctx(algorithm)
 
         Create a
-        :class:`~cryptogrpahy.hazmat.primitives.interfaces.HashContext` that
+        :class:`~cryptography.hazmat.primitives.interfaces.HashContext` that
         uses the specified ``algorithm`` to calculate a hash-based message
         authentication code.
 
@@ -131,3 +131,44 @@ A specific ``backend`` may provide one or more of these interfaces.
 
         :returns:
             :class:`~cryptography.hazmat.primitives.interfaces.HashContext`
+
+
+.. class:: PBKDF2HMACBackend
+
+    .. versionadded:: 0.2
+
+    A backend with methods for using PBKDF2 using HMAC as a PRF.
+
+    .. method:: pbkdf2_hmac_supported(algorithm)
+
+        Check if the specified ``algorithm`` is supported by this backend.
+
+        :param algorithm: An instance of a
+            :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`
+            provider.
+
+        :returns: ``True`` if the specified ``algorithm`` is supported for
+            PBKDF2 HMAC by this backend, otherwise ``False``.
+
+    .. method:: derive_pbkdf2_hmac(self, algorithm, length, salt, iterations,
+                                   key_material)
+
+        :param algorithm: An instance of a
+            :class:`~cryptography.hazmat.primitives.interfaces.HashAlgorithm`
+            provider.
+
+        :param int length: The desired length of the derived key. Maximum is
+            (2\ :sup:`32` - 1) * ``algorithm.digest_size``
+
+        :param bytes salt: A salt.
+
+        :param int iterations: The number of iterations to perform of the hash
+            function. This can be used to control the length of time the
+            operation takes. Higher numbers help mitigate brute force attacks
+            against derived keys.
+
+        :param bytes key_material: The key material to use as a basis for
+            the derived key. This is typically a password.
+
+        :return bytes: Derived key.
+