1 files changed, 108 insertions, 0 deletions
diff --git a/src/cryptography/hazmat/primitives/asymmetric/dsa.py b/src/cryptography/hazmat/primitives/asymmetric/dsa.py
new file mode 100644
index 00000000..83e01377
--- /dev/null
+++ b/src/cryptography/hazmat/primitives/asymmetric/dsa.py
@@ -0,0 +1,108 @@
+# 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
+
+import six
+
+from cryptography import utils
+
+
+def generate_parameters(key_size, backend):
+    return backend.generate_dsa_parameters(key_size)
+
+
+def generate_private_key(key_size, backend):
+    return backend.generate_dsa_private_key_and_parameters(key_size)
+
+
+def _check_dsa_parameters(parameters):
+    if utils.bit_length(parameters.p) not in [1024, 2048, 3072]:
+        raise ValueError("p must be exactly 1024, 2048, or 3072 bits long")
+    if utils.bit_length(parameters.q) not in [160, 256]:
+        raise ValueError("q must be exactly 160 or 256 bits long")
+
+    if not (1 < parameters.g < parameters.p):
+        raise ValueError("g, p don't satisfy 1 < g < p.")
+
+
+def _check_dsa_private_numbers(numbers):
+    parameters = numbers.public_numbers.parameter_numbers
+    _check_dsa_parameters(parameters)
+    if numbers.x <= 0 or numbers.x >= parameters.q:
+        raise ValueError("x must be > 0 and < q.")
+
+    if numbers.public_numbers.y != pow(parameters.g, numbers.x, parameters.p):
+        raise ValueError("y must be equal to (g ** x % p).")
+
+
+class DSAParameterNumbers(object):
+    def __init__(self, p, q, g):
+        if (
+            not isinstance(p, six.integer_types) or
+            not isinstance(q, six.integer_types) or
+            not isinstance(g, six.integer_types)
+        ):
+            raise TypeError(
+                "DSAParameterNumbers p, q, and g arguments must be integers."
+            )
+
+        self._p = p
+        self._q = q
+        self._g = g
+
+    p = utils.read_only_property("_p")
+    q = utils.read_only_property("_q")
+    g = utils.read_only_property("_g")
+
+    def parameters(self, backend):
+        return backend.load_dsa_parameter_numbers(self)
+
+
+class DSAPublicNumbers(object):
+    def __init__(self, y, parameter_numbers):
+        if not isinstance(y, six.integer_types):
+            raise TypeError("DSAPublicNumbers y argument must be an integer.")
+
+        if not isinstance(parameter_numbers, DSAParameterNumbers):
+            raise TypeError(
+                "parameter_numbers must be a DSAParameterNumbers instance."
+            )
+
+        self._y = y
+        self._parameter_numbers = parameter_numbers
+
+    y = utils.read_only_property("_y")
+    parameter_numbers = utils.read_only_property("_parameter_numbers")
+
+    def public_key(self, backend):
+        return backend.load_dsa_public_numbers(self)
+
+
+class DSAPrivateNumbers(object):
+    def __init__(self, x, public_numbers):
+        if not isinstance(x, six.integer_types):
+            raise TypeError("DSAPrivateNumbers x argument must be an integer.")
+
+        if not isinstance(public_numbers, DSAPublicNumbers):
+            raise TypeError(
+                "public_numbers must be a DSAPublicNumbers instance."
+            )
+        self._public_numbers = public_numbers
+        self._x = x
+
+    x = utils.read_only_property("_x")
+    public_numbers = utils.read_only_property("_public_numbers")
+
+    def private_key(self, backend):
+        return backend.load_dsa_private_numbers(self)