Add convenience methods to sign and verify w/ RSA (#2945)

This patch adds wrapper methods to allow the user to sign and verify a
single message block without having to go through the multi-step
process of creating a signer or verifier, updating it with the one
message, and finalizing the result. This will make signing and
verifying data more user-friendly when only using small messages.

Partial bug #1529

2 files changed, 23 insertions, 0 deletions

diff --git a/src/cryptography/hazmat/backends/openssl/rsa.py b/src/cryptography/hazmat/backends/openssl/rsa.py
index fa23bf89..10c51fee 100644
--- a/src/cryptography/hazmat/backends/openssl/rsa.py
+++ b/src/cryptography/hazmat/backends/openssl/rsa.py
@@ -611,6 +611,12 @@ class _RSAPrivateKey(object):
             self._rsa_cdata
         )
 
+    def sign(self, data, padding, algorithm):
+        signer = self.signer(padding, algorithm)
+        signer.update(data)
+        signature = signer.finalize()
+        return signature
+
 
 @utils.register_interface(RSAPublicKeyWithSerialization)
 class _RSAPublicKey(object):
@@ -661,3 +667,8 @@ class _RSAPublicKey(object):
             self._evp_pkey,
             self._rsa_cdata
         )
+
+    def verify(self, signature, data, padding, algorithm):
+        verifier = self.verifier(signature, padding, algorithm)
+        verifier.update(data)
+        verifier.verify()
diff --git a/src/cryptography/hazmat/primitives/asymmetric/rsa.py b/src/cryptography/hazmat/primitives/asymmetric/rsa.py
index 41b0089e..2cb89515 100644
--- a/src/cryptography/hazmat/primitives/asymmetric/rsa.py
+++ b/src/cryptography/hazmat/primitives/asymmetric/rsa.py
@@ -40,6 +40,12 @@ class RSAPrivateKey(object):
         The RSAPublicKey associated with this private key.
         """
 
+    @abc.abstractmethod
+    def sign(self, data, padding, algorithm):
+        """
+        Signs the data.
+        """
+
 
 @six.add_metaclass(abc.ABCMeta)
 class RSAPrivateKeyWithSerialization(RSAPrivateKey):
@@ -88,6 +94,12 @@ class RSAPublicKey(object):
         Returns the key serialized as bytes.
         """
 
+    @abc.abstractmethod
+    def verify(self, signature, data, padding, algorithm):
+        """
+        Verifies the signature of the data.
+        """
+
 
 RSAPublicKeyWithSerialization = RSAPublicKey