DSA public key serialization

2 files changed, 40 insertions, 2 deletions

diff --git a/src/cryptography/hazmat/backends/openssl/dsa.py b/src/cryptography/hazmat/backends/openssl/dsa.py
index 8d02e492..0089f58c 100644
--- a/src/cryptography/hazmat/backends/openssl/dsa.py
+++ b/src/cryptography/hazmat/backends/openssl/dsa.py
@@ -7,7 +7,7 @@ from __future__ import absolute_import, division, print_function
 from cryptography import utils
 from cryptography.exceptions import InvalidSignature
 from cryptography.hazmat.backends.openssl.utils import _truncate_digest
-from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives import hashes, serialization
 from cryptography.hazmat.primitives.asymmetric import (
     AsymmetricSignatureContext, AsymmetricVerificationContext, dsa
 )
@@ -208,3 +208,24 @@ class _DSAPublicKey(object):
         dsa_cdata.q = self._backend._lib.BN_dup(self._dsa_cdata.q)
         dsa_cdata.g = self._backend._lib.BN_dup(self._dsa_cdata.g)
         return _DSAParameters(self._backend, dsa_cdata)
+
+    def public_bytes(self, encoding, format):
+        if format is serialization.PublicFormat.PKCS1:
+            raise ValueError(
+                "DSA public keys do not support PKCS1 serialization"
+            )
+
+        evp_pkey = self._backend._lib.EVP_PKEY_new()
+        assert evp_pkey != self._backend._ffi.NULL
+        evp_pkey = self._backend._ffi.gc(
+            evp_pkey, self._backend._lib.EVP_PKEY_free
+        )
+        res = self._backend._lib.EVP_PKEY_set1_DSA(evp_pkey, self._dsa_cdata)
+        assert res == 1
+        return self._backend._public_key_bytes(
+            encoding,
+            format,
+            None,
+            evp_pkey,
+            None
+        )
diff --git a/src/cryptography/hazmat/primitives/asymmetric/dsa.py b/src/cryptography/hazmat/primitives/asymmetric/dsa.py
index 084686e4..4d332f2a 100644
--- a/src/cryptography/hazmat/primitives/asymmetric/dsa.py
+++ b/src/cryptography/hazmat/primitives/asymmetric/dsa.py
@@ -104,13 +104,30 @@ class DSAPublicKey(object):
 
 
 @six.add_metaclass(abc.ABCMeta)
-class DSAPublicKeyWithNumbers(DSAPublicKey):
+class DSAPublicKeyWithSerialization(DSAPublicKey):
     @abc.abstractmethod
     def public_numbers(self):
         """
         Returns a DSAPublicNumbers.
         """
 
+    @abc.abstractmethod
+    def public_bytes(self, encoding, format):
+        """
+        Returns the key serialized as bytes.
+        """
+
+
+DSAPublicKeyWithNumbers = utils.deprecated(
+    DSAPublicKeyWithSerialization,
+    __name__,
+    (
+        "The DSAPublicKeyWithNumbers interface has been renamed to "
+        "DSAPublicKeyWithSerialization"
+    ),
+    utils.DeprecatedIn08
+)
+
 
 def generate_parameters(key_size, backend):
     return backend.generate_dsa_parameters(key_size)