Reduce duplication. Also improve error message

1 files changed, 12 insertions, 25 deletions

diff --git a/cryptography/hazmat/primitives/ciphers/modes.py b/cryptography/hazmat/primitives/ciphers/modes.py
index 004a68bf..96b07ce1 100644
--- a/cryptography/hazmat/primitives/ciphers/modes.py
+++ b/cryptography/hazmat/primitives/ciphers/modes.py
@@ -17,6 +17,13 @@ from cryptography import utils
 from cryptography.hazmat.primitives import interfaces
 
 
+def _check_iv_length(mode, algorithm):
+    if len(mode.initialization_vector) * 8 != algorithm.block_size:
+        raise ValueError("Invalid IV size ({0}) for {1}".format(
+            len(mode.initialization_vector), mode.name
+        ))
+
+
 @utils.register_interface(interfaces.Mode)
 @utils.register_interface(interfaces.ModeWithInitializationVector)
 class CBC(object):
@@ -25,11 +32,7 @@ class CBC(object):
     def __init__(self, initialization_vector):
         self.initialization_vector = initialization_vector
 
-    def validate_for_algorithm(self, algorithm):
-        if len(self.initialization_vector) * 8 != algorithm.block_size:
-            raise ValueError("Invalid iv size ({0}) for {1}".format(
-                len(self.initialization_vector), self.name
-            ))
+    validate_for_algorithm = _check_iv_length
 
 
 @utils.register_interface(interfaces.Mode)
@@ -48,11 +51,7 @@ class OFB(object):
     def __init__(self, initialization_vector):
         self.initialization_vector = initialization_vector
 
-    def validate_for_algorithm(self, algorithm):
-        if len(self.initialization_vector) * 8 != algorithm.block_size:
-            raise ValueError("Invalid iv size ({0}) for {1}".format(
-                len(self.initialization_vector), self.name
-            ))
+    validate_for_algorithm = _check_iv_length
 
 
 @utils.register_interface(interfaces.Mode)
@@ -63,11 +62,7 @@ class CFB(object):
     def __init__(self, initialization_vector):
         self.initialization_vector = initialization_vector
 
-    def validate_for_algorithm(self, algorithm):
-        if len(self.initialization_vector) * 8 != algorithm.block_size:
-            raise ValueError("Invalid iv size ({0}) for {1}".format(
-                len(self.initialization_vector), self.name
-            ))
+    validate_for_algorithm = _check_iv_length
 
 
 @utils.register_interface(interfaces.Mode)
@@ -78,11 +73,7 @@ class CFB8(object):
     def __init__(self, initialization_vector):
         self.initialization_vector = initialization_vector
 
-    def validate_for_algorithm(self, algorithm):
-        if len(self.initialization_vector) * 8 != algorithm.block_size:
-            raise ValueError("Invalid iv size ({0}) for {1}".format(
-                len(self.initialization_vector), self.name
-            ))
+    validate_for_algorithm = _check_iv_length
 
 
 @utils.register_interface(interfaces.Mode)
@@ -93,11 +84,7 @@ class CTR(object):
     def __init__(self, nonce):
         self.nonce = nonce
 
-    def validate_for_algorithm(self, algorithm):
-        if len(self.nonce) * 8 != algorithm.block_size:
-            raise ValueError("Invalid nonce size ({0}) for {1}".format(
-                len(self.nonce), self.name
-            ))
+    validate_for_algorithm = _check_iv_length
 
 
 @utils.register_interface(interfaces.Mode)