Add a bytes method to get the DER ASN.1 encoding of an X509 name. (#3236)

* Add a bytes method to get the DER ASN.1 encoding of an X509 name.

This is useful for creating an OpenSSL style subject_name_hash (#3011)

* add to backend interface and update multibackend

* bytes -> public_bytes

2 files changed, 17 insertions, 0 deletions

diff --git a/tests/hazmat/backends/test_multibackend.py b/tests/hazmat/backends/test_multibackend.py
index 319edf7d..7ffc4236 100644
--- a/tests/hazmat/backends/test_multibackend.py
+++ b/tests/hazmat/backends/test_multibackend.py
@@ -240,6 +240,9 @@ class DummyX509Backend(object):
     def create_x509_revoked_certificate(self, builder):
         pass
 
+    def x509_name_bytes(self, name):
+        pass
+
 
 @utils.register_interface(ScryptBackend)
 class DummyScryptBackend(object):
@@ -554,6 +557,7 @@ class TestMultiBackend(object):
         backend.create_x509_certificate(object(), b"privatekey", hashes.SHA1())
         backend.create_x509_crl(object(), b"privatekey", hashes.SHA1())
         backend.create_x509_revoked_certificate(object())
+        backend.x509_name_bytes(object())
 
         backend = MultiBackend([DummyBackend()])
         with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_X509):
@@ -580,6 +584,8 @@ class TestMultiBackend(object):
             )
         with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_X509):
             backend.create_x509_revoked_certificate(object())
+        with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_X509):
+            backend.x509_name_bytes(object())
 
     def test_scrypt(self):
         backend = MultiBackend([DummyScryptBackend()])
diff --git a/tests/test_x509.py b/tests/test_x509.py
index f375ac55..5d334242 100644
--- a/tests/test_x509.py
+++ b/tests/test_x509.py
@@ -3842,6 +3842,17 @@ class TestName(object):
         with pytest.raises(TypeError):
             x509.Name(["not-a-NameAttribute"])
 
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_bytes(self, backend):
+        name = x509.Name([
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+        ])
+        assert name.public_bytes(backend) == binascii.unhexlify(
+            b"30293118301606035504030c0f63727970746f6772617068792e696f310d300"
+            b"b060355040a0c0450794341"
+        )
+
 
 def test_random_serial_number(monkeypatch):
     sample_data = os.urandom(20)