[aes] Add aes_cbc_encrypt

Used in daisuki.net (#4738)

test/test_aes.py

@@ -8,7 +8,7 @@
 import unittest
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
-from youtube_dl.aes import aes_decrypt, aes_encrypt, aes_cbc_decrypt, aes_decrypt_text
+from youtube_dl.aes import aes_decrypt, aes_encrypt, aes_cbc_decrypt, aes_cbc_encrypt, aes_decrypt_text
 from youtube_dl.utils import bytes_to_intlist, intlist_to_bytes
 import base64
 
@@ -34,6 +34,13 @@ def test_cbc_decrypt(self):
         decrypted = intlist_to_bytes(aes_cbc_decrypt(data, self.key, self.iv))
         self.assertEqual(decrypted.rstrip(b'\x08'), self.secret_msg)
 
+    def test_cbc_encrypt(self):
+        data = bytes_to_intlist(self.secret_msg)
+        encrypted = intlist_to_bytes(aes_cbc_encrypt(data, self.key, self.iv))
+        self.assertEqual(
+            encrypted,
+            b"\x97\x92+\xe5\x0b\xc3\x18\x91ky9m&\xb3\xb5@\xe6'\xc2\x96.\xc8u\x88\xab9-[\x9e|\xf1\xcd")
+
     def test_decrypt_text(self):
         password = intlist_to_bytes(self.key).decode('utf-8')
         encrypted = base64.b64encode(

youtube_dl/aes.py

@@ -60,6 +60,34 @@ def aes_cbc_decrypt(data, key, iv):
     return decrypted_data
 
 
+def aes_cbc_encrypt(data, key, iv):
+    """
+    Encrypt with aes in CBC mode. Using PKCS#7 padding
+
+    @param {int[]} data        cleartext
+    @param {int[]} key         16/24/32-Byte cipher key
+    @param {int[]} iv          16-Byte IV
+    @returns {int[]}           encrypted data
+    """
+    expanded_key = key_expansion(key)
+    block_count = int(ceil(float(len(data)) / BLOCK_SIZE_BYTES))
+
+    encrypted_data = []
+    previous_cipher_block = iv
+    for i in range(block_count):
+        block = data[i * BLOCK_SIZE_BYTES: (i + 1) * BLOCK_SIZE_BYTES]
+        remaining_length = BLOCK_SIZE_BYTES - len(block)
+        block += [remaining_length] * remaining_length
+        mixed_block = xor(block, previous_cipher_block)
+
+        encrypted_block = aes_encrypt(mixed_block, expanded_key)
+        encrypted_data += encrypted_block
+
+        previous_cipher_block = encrypted_block
+
+    return encrypted_data
+
+
 def key_expansion(data):
     """
     Generate key schedule