Adds certificate encoding to PEM and DER.

5 files changed, 111 insertions, 0 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 4d7a9a82..07d903c1 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -9,6 +9,8 @@ Changelog
 * Support serialization of certificate signing requests using the
   ``public_bytes`` method of
   :class:`~cryptography.x509.CertificateSigningRequest`.
+* Support serialization of certificates using the ``public_bytes`` method of
+  :class:`~cryptography.x509.Certificate`.
 
 0.9 - 2015-05-13
 ~~~~~~~~~~~~~~~~
diff --git a/docs/x509.rst b/docs/x509.rst
index c570f196..5e4d9bfa 100644
--- a/docs/x509.rst
+++ b/docs/x509.rst
@@ -326,6 +326,15 @@ X.509 Certificate Object
             <Extension(oid=<ObjectIdentifier(oid=2.5.29.32, name=certificatePolicies)>, critical=False, value=<CertificatePolicies([<PolicyInformation(policy_identifier=<ObjectIdentifier(oid=2.16.840.1.101.3.2.1.48.1, name=Unknown OID)>, policy_qualifiers=None)>])>)>
             <Extension(oid=<ObjectIdentifier(oid=2.5.29.19, name=basicConstraints)>, critical=True, value=<BasicConstraints(ca=True, path_length=None)>)>
 
+    .. method:: public_bytes(encoding)
+
+        :param encoding: The
+            :class:`~cryptography.hazmat.primitives.serialization.Encoding`
+            that will be used to serialize the certificate.
+
+        :return bytes: The data that can be written to a file or sent
+            over the network to be verified by clients.
+
 X.509 CSR (Certificate Signing Request) Object
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/src/cryptography/hazmat/backends/openssl/x509.py b/src/cryptography/hazmat/backends/openssl/x509.py
index 72041366..c7d2d154 100644
--- a/src/cryptography/hazmat/backends/openssl/x509.py
+++ b/src/cryptography/hazmat/backends/openssl/x509.py
@@ -311,6 +311,18 @@ class _Certificate(object):
 
         return x509.Extensions(extensions)
 
+    def public_bytes(self, encoding):
+        if not isinstance(encoding, serialization.Encoding):
+            raise TypeError("encoding must be an item from the Encoding enum")
+
+        bio = self._backend._create_mem_bio()
+        if encoding is serialization.Encoding.PEM:
+            res = self._backend._lib.PEM_write_bio_X509(bio, self._x509)
+        elif encoding is serialization.Encoding.DER:
+            res = self._backend._lib.i2d_X509_bio(bio, self._x509)
+        assert res == 1
+        return self._backend._read_mem_bio(bio)
+
 
 def _decode_certificate_policies(backend, ext):
     cp = backend._ffi.cast(
diff --git a/src/cryptography/x509.py b/src/cryptography/x509.py
index 9a3295ce..a786c705 100644
--- a/src/cryptography/x509.py
+++ b/src/cryptography/x509.py
@@ -1167,6 +1167,10 @@ class Certificate(object):
         Checks not equal.
         """
 
+    @abc.abstractmethod
+    def public_bytes(self, encoding):
+        pass
+
 
 @six.add_metaclass(abc.ABCMeta)
 class CertificateSigningRequest(object):
diff --git a/tests/test_x509.py b/tests/test_x509.py
index 72fc9d40..a3bed85f 100644
--- a/tests/test_x509.py
+++ b/tests/test_x509.py
@@ -368,6 +368,90 @@ class TestRSACertificate(object):
         with pytest.raises(UnsupportedAlgorithm):
             cert.signature_hash_algorithm
 
+    def test_public_bytes_pem(self, backend):
+        # Load an existing certificate.
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        # Encode it to PEM and load it back.
+        cert = x509.load_pem_x509_certificate(cert.public_bytes(
+            encoding=serialization.Encoding.PEM,
+        ), backend)
+
+        # We should recover what we had to start with.
+        assert cert.not_valid_before == datetime.datetime(2010, 1, 1, 8, 30)
+        assert cert.not_valid_after == datetime.datetime(2030, 12, 31, 8, 30)
+        assert cert.serial == 2
+        public_key = cert.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        assert cert.version is x509.Version.v3
+        fingerprint = binascii.hexlify(cert.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"6f49779533d565e8b7c1062503eab41492c38e4d"
+
+    def test_public_bytes_der(self, backend):
+        # Load an existing certificate.
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        # Encode it to DER and load it back.
+        cert = x509.load_der_x509_certificate(cert.public_bytes(
+            encoding=serialization.Encoding.DER,
+        ), backend)
+
+        # We should recover what we had to start with.
+        assert cert.not_valid_before == datetime.datetime(2010, 1, 1, 8, 30)
+        assert cert.not_valid_after == datetime.datetime(2030, 12, 31, 8, 30)
+        assert cert.serial == 2
+        public_key = cert.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        assert cert.version is x509.Version.v3
+        fingerprint = binascii.hexlify(cert.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"6f49779533d565e8b7c1062503eab41492c38e4d"
+
+    def test_public_bytes_invalid_encoding(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        with pytest.raises(TypeError):
+            cert.public_bytes('NotAnEncoding')
+
+    @pytest.mark.parametrize(
+        ("cert_path", "loader_func", "encoding"),
+        [
+            (
+                os.path.join("x509", "v1_cert.pem"),
+                x509.load_pem_x509_certificate,
+                serialization.Encoding.PEM,
+            ),
+            (
+                os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+                x509.load_der_x509_certificate,
+                serialization.Encoding.DER,
+            ),
+        ]
+    )
+    def test_public_bytes_match(self, cert_path, loader_func, encoding,
+                                backend):
+        cert_bytes = load_vectors_from_file(
+            cert_path, lambda pemfile: pemfile.read(), mode="rb"
+        )
+        cert = loader_func(cert_bytes, backend)
+        serialized = cert.public_bytes(encoding)
+        assert serialized == cert_bytes
+
+
+@pytest.mark.requires_backend_interface(interface=RSABackend)
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestRSACertificateRequest(object):
     @pytest.mark.parametrize(
         ("path", "loader_func"),
         [