3 files changed, 46 insertions, 0 deletions
diff --git a/src/cryptography/hazmat/backends/openssl/x509.py b/src/cryptography/hazmat/backends/openssl/x509.py
index 76dcf32f..a3dddc49 100644
--- a/src/cryptography/hazmat/backends/openssl/x509.py
+++ b/src/cryptography/hazmat/backends/openssl/x509.py
@@ -136,3 +136,14 @@ class _Certificate(object):
             )
 
         return x509.Name(attributes)
+
+    @property
+    def signature_algorithm(self):
+        buf_len = 50
+        buf = self._backend._ffi.new("char[]", buf_len)
+        res = self._backend._lib.OBJ_obj2txt(
+            buf, buf_len, self._x509.sig_alg.algorithm, 1
+        )
+        assert res <= 50 and res > 0
+        oid = self._backend._ffi.buffer(buf, res)[:].decode()
+        return x509.ObjectIdentifier(oid)
diff --git a/src/cryptography/hazmat/bindings/openssl/x509.py b/src/cryptography/hazmat/bindings/openssl/x509.py
index e30d23b7..bf689e33 100644
--- a/src/cryptography/hazmat/bindings/openssl/x509.py
+++ b/src/cryptography/hazmat/bindings/openssl/x509.py
@@ -65,6 +65,7 @@ typedef struct {
 } X509_CRL;
 
 typedef struct {
+    X509_ALGOR *sig_alg;
     X509_CINF *cert_info;
     ...;
 } X509;
diff --git a/src/cryptography/x509.py b/src/cryptography/x509.py
index 8a888d2a..c4d87bb7 100644
--- a/src/cryptography/x509.py
+++ b/src/cryptography/x509.py
@@ -28,6 +28,19 @@ _OID_NAMES = {
     "2.5.4.65": "pseudonym",
     "0.9.2342.19200300.100.1.25": "domainComponent",
     "1.2.840.113549.1.9.1": "emailAddress",
+    "1.2.840.113549.1.1.4": "md5WithRSA",
+    "1.2.840.113549.1.1.5": "sha1WithRSA",
+    "1.2.840.113549.1.1.14": "sha224WithRSAEncryption",
+    "1.2.840.113549.1.1.11": "sha256WithRSAEncryption",
+    "1.2.840.113549.1.1.12": "sha384WithRSAEncryption",
+    "1.2.840.113549.1.1.13": "sha512WithRSAEncryption",
+    "1.2.840.10045.4.3.1": "ecdsa_with_SHA224",
+    "1.2.840.10045.4.3.2": "ecdsa_with_SHA256",
+    "1.2.840.10045.4.3.3": "ecdsa_with_SHA384",
+    "1.2.840.10045.4.3.4": "ecdsa_with_SHA512",
+    "1.2.840.10040.4.3": "dsaWithSHA1",
+    "2.16.840.1.101.3.4.3.1": "dsa_with_SHA224",
+    "2.16.840.1.101.3.4.3.2": "dsa_with_SHA256",
 }
 
 
@@ -143,6 +156,20 @@ OID_PSEUDONYM = ObjectIdentifier("2.5.4.65")
 OID_DOMAIN_COMPONENT = ObjectIdentifier("0.9.2342.19200300.100.1.25")
 OID_EMAIL_ADDRESS = ObjectIdentifier("1.2.840.113549.1.9.1")
 
+OID_MD5_WITH_RSA = ObjectIdentifier("1.2.840.113549.1.1.4")
+OID_SHA1_WITH_RSA = ObjectIdentifier("1.2.840.113549.1.1.5")
+OID_SHA224_WITH_RSA = ObjectIdentifier("1.2.840.113549.1.1.14")
+OID_SHA256_WITH_RSA = ObjectIdentifier("1.2.840.113549.1.1.11")
+OID_SHA384_WITH_RSA = ObjectIdentifier("1.2.840.113549.1.1.12")
+OID_SHA512_WITH_RSA = ObjectIdentifier("1.2.840.113549.1.1.13")
+OID_ECDSA_WITH_SHA224 = ObjectIdentifier("1.2.840.10045.4.3.1")
+OID_ECDSA_WITH_SHA256 = ObjectIdentifier("1.2.840.10045.4.3.2")
+OID_ECDSA_WITH_SHA384 = ObjectIdentifier("1.2.840.10045.4.3.3")
+OID_ECDSA_WITH_SHA512 = ObjectIdentifier("1.2.840.10045.4.3.4")
+OID_DSA_WITH_SHA1 = ObjectIdentifier("1.2.840.10040.4.3")
+OID_DSA_WITH_SHA224 = ObjectIdentifier("2.16.840.1.101.3.4.3.1")
+OID_DSA_WITH_SHA256 = ObjectIdentifier("2.16.840.1.101.3.4.3.2")
+
 
 @six.add_metaclass(abc.ABCMeta)
 class Certificate(object):
@@ -193,3 +220,10 @@ class Certificate(object):
         """
         Returns the subject name object.
         """
+
+    @abc.abstractproperty
+    def signature_algorithm(self):
+        """
+        Returns an ObjectIdentifier corresponding to the signature algorithm of
+        the certificate.
+        """