faset over fra Z3950 til google books

python/gdata/tlslite/utils/OpenSSL_AES.py

@@ -0,0 +1,49 @@
+"""OpenSSL/M2Crypto AES implementation."""
+
+from cryptomath import *
+from AES import *
+
+if m2cryptoLoaded:
+
+    def new(key, mode, IV):
+        return OpenSSL_AES(key, mode, IV)
+
+    class OpenSSL_AES(AES):
+
+        def __init__(self, key, mode, IV):
+            AES.__init__(self, key, mode, IV, "openssl")
+            self.key = key
+            self.IV = IV
+
+        def _createContext(self, encrypt):
+            context = m2.cipher_ctx_new()
+            if len(self.key)==16:
+                cipherType = m2.aes_128_cbc()
+            if len(self.key)==24:
+                cipherType = m2.aes_192_cbc()
+            if len(self.key)==32:
+                cipherType = m2.aes_256_cbc()
+            m2.cipher_init(context, cipherType, self.key, self.IV, encrypt)
+            return context
+
+        def encrypt(self, plaintext):
+            AES.encrypt(self, plaintext)
+            context = self._createContext(1)
+            ciphertext = m2.cipher_update(context, plaintext)
+            m2.cipher_ctx_free(context)
+            self.IV = ciphertext[-self.block_size:]
+            return ciphertext
+
+        def decrypt(self, ciphertext):
+            AES.decrypt(self, ciphertext)
+            context = self._createContext(0)
+            #I think M2Crypto has a bug - it fails to decrypt and return the last block passed in.
+            #To work around this, we append sixteen zeros to the string, below:
+            plaintext = m2.cipher_update(context, ciphertext+('\0'*16))
+
+            #If this bug is ever fixed, then plaintext will end up having a garbage
+            #plaintext block on the end.  That's okay - the below code will discard it.
+            plaintext = plaintext[:len(ciphertext)]
+            m2.cipher_ctx_free(context)
+            self.IV = ciphertext[-self.block_size:]
+            return plaintext