Merge pull request #876 from public/unsupported-algorithm-asym-tags

Extra UnsupportedAlgorithm reason tags

3 files changed, 12 insertions, 5 deletions

diff --git a/cryptography/exceptions.py b/cryptography/exceptions.py
index 4b4d4c37..b4ee8feb 100644
--- a/cryptography/exceptions.py
+++ b/cryptography/exceptions.py
@@ -19,6 +19,8 @@ class _Reasons(object):
     UNSUPPORTED_HASH = object()
     UNSUPPORTED_CIPHER = object()
     UNSUPPORTED_PADDING = object()
+    UNSUPPORTED_MGF = object()
+    UNSUPPORTED_PUBLIC_KEY_ALGORITHM = object()
 
 
 class UnsupportedAlgorithm(Exception):
diff --git a/cryptography/hazmat/backends/multibackend.py b/cryptography/hazmat/backends/multibackend.py
index 2a1ec439..aa649dd3 100644
--- a/cryptography/hazmat/backends/multibackend.py
+++ b/cryptography/hazmat/backends/multibackend.py
@@ -126,16 +126,19 @@ class MultiBackend(object):
     def generate_rsa_private_key(self, public_exponent, key_size):
         for b in self._filtered_backends(RSABackend):
             return b.generate_rsa_private_key(public_exponent, key_size)
-        raise UnsupportedAlgorithm("RSA is not supported by the backend")
+        raise UnsupportedAlgorithm("RSA is not supported by the backend",
+                                   _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM)
 
     def create_rsa_signature_ctx(self, private_key, padding, algorithm):
         for b in self._filtered_backends(RSABackend):
             return b.create_rsa_signature_ctx(private_key, padding, algorithm)
-        raise UnsupportedAlgorithm("RSA is not supported by the backend")
+        raise UnsupportedAlgorithm("RSA is not supported by the backend",
+                                   _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM)
 
     def create_rsa_verification_ctx(self, public_key, signature, padding,
                                     algorithm):
         for b in self._filtered_backends(RSABackend):
             return b.create_rsa_verification_ctx(public_key, signature,
                                                  padding, algorithm)
-        raise UnsupportedAlgorithm("RSA is not supported by the backend")
+        raise UnsupportedAlgorithm("RSA is not supported by the backend",
+                                   _Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM)
diff --git a/cryptography/hazmat/backends/openssl/backend.py b/cryptography/hazmat/backends/openssl/backend.py
index 753717d4..3293741c 100644
--- a/cryptography/hazmat/backends/openssl/backend.py
+++ b/cryptography/hazmat/backends/openssl/backend.py
@@ -731,7 +731,8 @@ class _RSASignatureContext(object):
         elif isinstance(padding, PSS):
             if not isinstance(padding._mgf, MGF1):
                 raise UnsupportedAlgorithm(
-                    "Only MGF1 is supported by this backend"
+                    "Only MGF1 is supported by this backend",
+                    _Reasons.UNSUPPORTED_MGF
                 )
 
             # Size of key in bytes - 2 is the maximum
@@ -915,7 +916,8 @@ class _RSAVerificationContext(object):
         elif isinstance(padding, PSS):
             if not isinstance(padding._mgf, MGF1):
                 raise UnsupportedAlgorithm(
-                    "Only MGF1 is supported by this backend"
+                    "Only MGF1 is supported by this backend",
+                    _Reasons.UNSUPPORTED_MGF
                 )
 
             # Size of key in bytes - 2 is the maximum