add MGF1 class, docs, tests

1 files changed, 21 insertions, 0 deletions

diff --git a/cryptography/hazmat/primitives/asymmetric/padding.py b/cryptography/hazmat/primitives/asymmetric/padding.py
index 6bafe314..df960b0f 100644
--- a/cryptography/hazmat/primitives/asymmetric/padding.py
+++ b/cryptography/hazmat/primitives/asymmetric/padding.py
@@ -13,6 +13,8 @@
 
 from __future__ import absolute_import, division, print_function
 
+import six
+
 from cryptography import utils
 from cryptography.hazmat.primitives import interfaces
 
@@ -20,3 +22,22 @@ from cryptography.hazmat.primitives import interfaces
 @utils.register_interface(interfaces.AsymmetricPadding)
 class PKCS1v15(object):
     name = "EMSA-PKCS1-v1_5"
+
+
+class MGF1(object):
+    MAX_LENGTH = b"MAX_LENGTH"
+
+    def __init__(self, algorithm, salt_length):
+        if not isinstance(algorithm, interfaces.HashAlgorithm):
+            raise TypeError("Expected instance of interfaces.HashAlgorithm.")
+
+        self.algorithm = algorithm
+
+        if (not isinstance(salt_length, six.integer_types) and
+                salt_length != b"MAX_LENGTH"):
+            raise TypeError("salt_length must be an integer")
+
+        if salt_length != b"MAX_LENGTH" and salt_length < 0:
+            raise ValueError("salt_length must be zero or greater")
+
+        self.salt_length = salt_length