add new DSABackend interface methods for loading numbers

2 files changed, 52 insertions, 0 deletions

diff --git a/cryptography/hazmat/backends/interfaces.py b/cryptography/hazmat/backends/interfaces.py
index 524e0a5b..e4faf32c 100644
--- a/cryptography/hazmat/backends/interfaces.py
+++ b/cryptography/hazmat/backends/interfaces.py
@@ -196,6 +196,24 @@ class DSABackend(object):
         Return True if the parameters are supported by the backend for DSA.
         """
 
+    @abc.abstractmethod
+    def load_dsa_private_numbers(self, numbers):
+        """
+        Returns a DSAPrivateKey provider.
+        """
+
+    @abc.abstractmethod
+    def load_dsa_public_numbers(self, numbers):
+        """
+        Returns a DSAPublicKey provider.
+        """
+
+    @abc.abstractmethod
+    def load_dsa_parameter_numbers(self, numbers):
+        """
+        Returns a DSAParameters provider.
+        """
+
 
 @six.add_metaclass(abc.ABCMeta)
 class TraditionalOpenSSLSerializationBackend(object):
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index 9e476f72..5cbd47d1 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -470,6 +470,40 @@ A specific ``backend`` may provide one or more of these interfaces.
         :returns: ``True`` if the given values of ``p``, ``q``, and ``g`` are
             supported by this backend, otherwise ``False``.
 
+    .. method:: load_dsa_parameter_numbers(numbers):
+
+        :param numbers: An instance of
+            :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAParameterNumbers`.
+
+        :returns: A provider of
+            :class:`~cryptography.hazmat.primitives.interfaces.DSAParameters`.
+
+        :raises cryptography.exceptions.UnsupportedAlgorithm: This raised when
+            any backend specific criteria are not met.
+
+    .. method:: load_dsa_private_numbers(numbers):
+
+        :param numbers: An instance of
+            :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPrivateNumbers`.
+
+        :returns: A provider of
+            :class:`~cryptography.hazmat.primitives.interfaces.DSAPrivateKey`.
+
+        :raises cryptography.exceptions.UnsupportedAlgorithm: This raised when
+            any backend specific criteria are not met.
+
+    .. method:: load_dsa_public_numbers(numbers):
+
+        :param numbers: An instance of
+            :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicNumbers`.
+
+        :returns: A provider of
+            :class:`~cryptography.hazmat.primitives.interfaces.DSAPublicKey`.
+
+        :raises cryptography.exceptions.UnsupportedAlgorithm: This raised when
+            any backend specific criteria are not met.
+
+
 
 .. class:: CMACBackend