simplify test

tests/test_rsa_keys.py

@@ -160,38 +160,25 @@ def test_verify_rsa_signature(self):
 
   def test_verify_rsa_pss_sha256(self):
     rsa_scheme = 'rsassa-pss-sha256'
-    data = 'Some say the bigger the salt, the more provable the security'.encode('utf-8')
+    data = 'The ancients say the longer the salt, the more provable the security'.encode('utf-8')
 
-    private_key_object = load_pem_private_key(private_rsa.encode('utf-8'),
+    private_key = load_pem_private_key(private_rsa.encode('utf-8'),
         password=None, backend=default_backend())
-    public_key_object = load_pem_public_key(public_rsa.encode('utf-8'),
-        backend=default_backend())
-    digest_obj = securesystemslib.hash.digest_from_rsa_scheme(rsa_scheme,
-        'pyca_crypto')
-    max_salt_length = padding.calculate_max_pss_salt_length(private_key_object, digest_obj)
-
-    # Check that every valid salt length value can be automatically verified.
-    for salt_length in range(max_salt_length+1):
-      signature = private_key_object.sign(
-          data, padding.PSS(mgf=padding.MGF1(digest_obj.algorithm),
-          salt_length=salt_length), digest_obj.algorithm)
-
-      # Current behaviour: automatic inferring of salt length.
-      self.assertTrue(securesystemslib.rsa_keys.verify_rsa_signature(signature,
-          rsa_scheme, public_rsa, data))
-
-      # Previous behaviour: generally wrong assumption about salt length.
-      if salt_length == digest_obj.digest_size:
-        self.assertIsNone(public_key_object.verify(signature, data,
-                padding.PSS(mgf=padding.MGF1(digest_obj.algorithm),
-                salt_length=padding.PSS.DIGEST_LENGTH),
-                digest_obj.algorithm))
-      else:
-        with self.assertRaises(InvalidSignature):
-          public_key_object.verify(signature, data,
-                padding.PSS(mgf=padding.MGF1(digest_obj.algorithm),
-                salt_length=padding.PSS.DIGEST_LENGTH),
-                digest_obj.algorithm)
+    digest = securesystemslib.hash.digest_from_rsa_scheme(rsa_scheme, 'pyca_crypto')
+
+    # Old-style signature: use the hash length as the salt length.
+    old_signature = private_key.sign(data,
+      padding.PSS(mgf=padding.MGF1(digest.algorithm), salt_length=padding.PSS.DIGEST_LENGTH),
+      digest.algorithm)
+
+    # New-style signature: use the automatic salt length.
+    new_signature, _ = securesystemslib.rsa_keys.create_rsa_signature(private_rsa, data)
+
+    # Verify both old-style and new-style signatures.
+    for signature in (old_signature, new_signature):
+      verified = securesystemslib.rsa_keys.verify_rsa_signature(signature, rsa_scheme,
+                                                                public_rsa, data)
+      self.assertTrue(verified)
 
 
   def test_create_rsa_encrypted_pem(self):