Move signature type checks

Move the point of checking signatures, as suggested by alex in PR 2262.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/cryptography/hazmat/backends/openssl/rsa.py b/src/cryptography/hazmat/backends/openssl/rsa.py
index 8e32eb02..7da42292 100644
--- a/src/cryptography/hazmat/backends/openssl/rsa.py
+++ b/src/cryptography/hazmat/backends/openssl/rsa.py
@@ -337,9 +337,6 @@ class _RSASignatureContext(object):
 @utils.register_interface(AsymmetricVerificationContext)
 class _RSAVerificationContext(object):
     def __init__(self, backend, public_key, signature, padding, algorithm):
-        if not isinstance(signature, bytes):
-            raise TypeError("signature must be bytes.")
-
         self._backend = backend
         self._public_key = public_key
         self._signature = signature
@@ -578,6 +575,9 @@ class _RSAPublicKey(object):
     key_size = utils.read_only_property("_key_size")
 
     def verifier(self, signature, padding, algorithm):
+        if not isinstance(signature, bytes):
+            raise TypeError("signature must be bytes.")
+
         return _RSAVerificationContext(
             self._backend, self, signature, padding, algorithm
         )