[aes] Add aes_gcm_decrypt_and_verify (#1020)

Authored by: sulyi, pukkandan

test/test_aes.py

@@ -7,7 +7,19 @@
 import unittest
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
-from yt_dlp.aes import aes_decrypt, aes_encrypt, aes_cbc_decrypt, aes_cbc_encrypt, aes_decrypt_text
+from yt_dlp.aes import (
+    aes_decrypt,
+    aes_encrypt,
+    aes_cbc_decrypt,
+    aes_cbc_decrypt_bytes,
+    aes_cbc_encrypt,
+    aes_ctr_decrypt,
+    aes_ctr_encrypt,
+    aes_gcm_decrypt_and_verify,
+    aes_gcm_decrypt_and_verify_bytes,
+    aes_decrypt_text
+)
+from yt_dlp.compat import compat_pycrypto_AES
 from yt_dlp.utils import bytes_to_intlist, intlist_to_bytes
 import base64
 
@@ -27,10 +39,11 @@ def test_encrypt(self):
         self.assertEqual(decrypted, msg)
 
     def test_cbc_decrypt(self):
-        data = bytes_to_intlist(
+        data = b'\x97\x92+\xe5\x0b\xc3\x18\x91ky9m&\xb3\xb5@\xe6\x27\xc2\x96.\xc8u\x88\xab9-[\x9e|\xf1\xcd'
-            b"\x97\x92+\xe5\x0b\xc3\x18\x91ky9m&\xb3\xb5@\xe6'\xc2\x96.\xc8u\x88\xab9-[\x9e|\xf1\xcd"
+        decrypted = intlist_to_bytes(aes_cbc_decrypt(bytes_to_intlist(data), self.key, self.iv))
-        )
+        self.assertEqual(decrypted.rstrip(b'\x08'), self.secret_msg)
-        decrypted = intlist_to_bytes(aes_cbc_decrypt(data, self.key, self.iv))
+        if compat_pycrypto_AES:
+            decrypted = aes_cbc_decrypt_bytes(data, intlist_to_bytes(self.key), intlist_to_bytes(self.iv))
             self.assertEqual(decrypted.rstrip(b'\x08'), self.secret_msg)
 
     def test_cbc_encrypt(self):
@@ -38,7 +51,31 @@ def test_cbc_encrypt(self):
         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")
+            b'\x97\x92+\xe5\x0b\xc3\x18\x91ky9m&\xb3\xb5@\xe6\'\xc2\x96.\xc8u\x88\xab9-[\x9e|\xf1\xcd')
+
+    def test_ctr_decrypt(self):
+        data = bytes_to_intlist(b'\x03\xc7\xdd\xd4\x8e\xb3\xbc\x1a*O\xdc1\x12+8Aio\xd1z\xb5#\xaf\x08')
+        decrypted = intlist_to_bytes(aes_ctr_decrypt(data, self.key, self.iv))
+        self.assertEqual(decrypted.rstrip(b'\x08'), self.secret_msg)
+
+    def test_ctr_encrypt(self):
+        data = bytes_to_intlist(self.secret_msg)
+        encrypted = intlist_to_bytes(aes_ctr_encrypt(data, self.key, self.iv))
+        self.assertEqual(
+            encrypted,
+            b'\x03\xc7\xdd\xd4\x8e\xb3\xbc\x1a*O\xdc1\x12+8Aio\xd1z\xb5#\xaf\x08')
+
+    def test_gcm_decrypt(self):
+        data = b'\x159Y\xcf5eud\x90\x9c\x85&]\x14\x1d\x0f.\x08\xb4T\xe4/\x17\xbd'
+        authentication_tag = b'\xe8&I\x80rI\x07\x9d}YWuU@:e'
+
+        decrypted = intlist_to_bytes(aes_gcm_decrypt_and_verify(
+            bytes_to_intlist(data), self.key, bytes_to_intlist(authentication_tag), self.iv[:12]))
+        self.assertEqual(decrypted.rstrip(b'\x08'), self.secret_msg)
+        if compat_pycrypto_AES:
+            decrypted = aes_gcm_decrypt_and_verify_bytes(
+                data, intlist_to_bytes(self.key), authentication_tag, intlist_to_bytes(self.iv[:12]))
+            self.assertEqual(decrypted.rstrip(b'\x08'), self.secret_msg)
 
     def test_decrypt_text(self):
         password = intlist_to_bytes(self.key).decode('utf-8')

test/test_cookies.py

@@ -2,7 +2,6 @@
 from datetime import datetime, timezone
 
 from yt_dlp import cookies
-from yt_dlp.compat import compat_pycrypto_AES
 from yt_dlp.cookies import (
     LinuxChromeCookieDecryptor,
     MacChromeCookieDecryptor,
@@ -53,7 +52,6 @@ def test_chrome_cookie_decryptor_linux_v11(self):
             decryptor = LinuxChromeCookieDecryptor('Chrome', YDLLogger())
             self.assertEqual(decryptor.decrypt(encrypted_value), value)
 
-    @unittest.skipIf(not compat_pycrypto_AES, 'cryptography library not available')
     def test_chrome_cookie_decryptor_windows_v10(self):
         with MonkeyPatch(cookies, {
             '_get_windows_v10_key': lambda *args, **kwargs: b'Y\xef\xad\xad\xeerp\xf0Y\xe6\x9b\x12\xc2<z\x16]\n\xbb\xb8\xcb\xd7\x9bA\xc3\x14e\x99{\xd6\xf4&'

yt_dlp/aes.py

@@ -11,39 +11,59 @@ def aes_cbc_decrypt_bytes(data, key, iv):
         """ Decrypt bytes with AES-CBC using pycryptodome """
         return compat_pycrypto_AES.new(key, compat_pycrypto_AES.MODE_CBC, iv).decrypt(data)
 
+    def aes_gcm_decrypt_and_verify_bytes(data, key, tag, nonce):
+        """ Decrypt bytes with AES-GCM using pycryptodome """
+        return compat_pycrypto_AES.new(key, compat_pycrypto_AES.MODE_GCM, nonce).decrypt_and_verify(data, tag)
+
 else:
     def aes_cbc_decrypt_bytes(data, key, iv):
         """ Decrypt bytes with AES-CBC using native implementation since pycryptodome is unavailable """
         return intlist_to_bytes(aes_cbc_decrypt(*map(bytes_to_intlist, (data, key, iv))))
 
+    def aes_gcm_decrypt_and_verify_bytes(data, key, tag, nonce):
+        """ Decrypt bytes with AES-GCM using native implementation since pycryptodome is unavailable """
+        return intlist_to_bytes(aes_gcm_decrypt_and_verify(*map(bytes_to_intlist, (data, key, tag, nonce))))
+
 
 BLOCK_SIZE_BYTES = 16
 
 
-def aes_ctr_decrypt(data, key, counter):
+def aes_ctr_decrypt(data, key, iv):
     """
     Decrypt with aes in counter mode
 
     @param {int[]} data        cipher
     @param {int[]} key         16/24/32-Byte cipher key
-    @param {instance} counter  Instance whose next_value function (@returns {int[]}  16-Byte block)
+    @param {int[]} iv          16-Byte initialization vector
-                               returns the next counter block
     @returns {int[]}           decrypted data
     """
+    return aes_ctr_encrypt(data, key, iv)
+
+
+def aes_ctr_encrypt(data, key, iv):
+    """
+    Encrypt with aes in counter mode
+
+    @param {int[]} data        cleartext
+    @param {int[]} key         16/24/32-Byte cipher key
+    @param {int[]} iv          16-Byte initialization vector
+    @returns {int[]}           encrypted data
+    """
     expanded_key = key_expansion(key)
     block_count = int(ceil(float(len(data)) / BLOCK_SIZE_BYTES))
+    counter = iter_vector(iv)
 
-    decrypted_data = []
+    encrypted_data = []
     for i in range(block_count):
-        counter_block = counter.next_value()
+        counter_block = next(counter)
         block = data[i * BLOCK_SIZE_BYTES: (i + 1) * BLOCK_SIZE_BYTES]
         block += [0] * (BLOCK_SIZE_BYTES - len(block))
 
         cipher_counter_block = aes_encrypt(counter_block, expanded_key)
-        decrypted_data += xor(block, cipher_counter_block)
+        encrypted_data += xor(block, cipher_counter_block)
-    decrypted_data = decrypted_data[:len(data)]
+    encrypted_data = encrypted_data[:len(data)]
 
-    return decrypted_data
+    return encrypted_data
 
 
 def aes_cbc_decrypt(data, key, iv):
@@ -100,39 +120,47 @@ def aes_cbc_encrypt(data, key, iv):
     return encrypted_data
 
 
-def key_expansion(data):
+def aes_gcm_decrypt_and_verify(data, key, tag, nonce):
     """
-    Generate key schedule
+    Decrypt with aes in GBM mode and checks authenticity using tag
 
-    @param {int[]} data  16/24/32-Byte cipher key
+    @param {int[]} data        cipher
-    @returns {int[]}     176/208/240-Byte expanded key
+    @param {int[]} key         16-Byte cipher key
+    @param {int[]} tag         authentication tag
+    @param {int[]} nonce       IV (recommended 12-Byte)
+    @returns {int[]}           decrypted data
     """
-    data = data[:]  # copy
-    rcon_iteration = 1
-    key_size_bytes = len(data)
-    expanded_key_size_bytes = (key_size_bytes // 4 + 7) * BLOCK_SIZE_BYTES
 
-    while len(data) < expanded_key_size_bytes:
+    # XXX: check aes, gcm param
-        temp = data[-4:]
-        temp = key_schedule_core(temp, rcon_iteration)
-        rcon_iteration += 1
-        data += xor(temp, data[-key_size_bytes: 4 - key_size_bytes])
 
-        for _ in range(3):
+    hash_subkey = aes_encrypt([0] * BLOCK_SIZE_BYTES, key_expansion(key))
-            temp = data[-4:]
-            data += xor(temp, data[-key_size_bytes: 4 - key_size_bytes])
 
-        if key_size_bytes == 32:
+    if len(nonce) == 12:
-            temp = data[-4:]
+        j0 = nonce + [0, 0, 0, 1]
-            temp = sub_bytes(temp)
+    else:
-            data += xor(temp, data[-key_size_bytes: 4 - key_size_bytes])
+        fill = (BLOCK_SIZE_BYTES - (len(nonce) % BLOCK_SIZE_BYTES)) % BLOCK_SIZE_BYTES + 8
+        ghash_in = nonce + [0] * fill + bytes_to_intlist((8 * len(nonce)).to_bytes(8, 'big'))
+        j0 = ghash(hash_subkey, ghash_in)
 
-        for _ in range(3 if key_size_bytes == 32 else 2 if key_size_bytes == 24 else 0):
+    # TODO: add nonce support to aes_ctr_decrypt
-            temp = data[-4:]
-            data += xor(temp, data[-key_size_bytes: 4 - key_size_bytes])
-    data = data[:expanded_key_size_bytes]
 
-    return data
+    # nonce_ctr = j0[:12]
+    iv_ctr = inc(j0)
+
+    decrypted_data = aes_ctr_decrypt(data, key, iv_ctr + [0] * (BLOCK_SIZE_BYTES - len(iv_ctr)))
+    pad_len = len(data) // 16 * 16
+    s_tag = ghash(
+        hash_subkey,
+        data
+        + [0] * (BLOCK_SIZE_BYTES - len(data) + pad_len)        # pad
+        + bytes_to_intlist((0 * 8).to_bytes(8, 'big')           # length of associated data
+                           + ((len(data) * 8).to_bytes(8, 'big')))  # length of data
+    )
+
+    if tag != aes_ctr_encrypt(s_tag, key, j0):
+        raise ValueError("Mismatching authentication tag")
+
+    return decrypted_data
 
 
 def aes_encrypt(data, expanded_key):
@@ -201,15 +229,7 @@ def aes_decrypt_text(data, password, key_size_bytes):
     nonce = data[:NONCE_LENGTH_BYTES]
     cipher = data[NONCE_LENGTH_BYTES:]
 
-    class Counter(object):
+    decrypted_data = aes_ctr_decrypt(cipher, key, nonce + [0] * (BLOCK_SIZE_BYTES - NONCE_LENGTH_BYTES))
-        __value = nonce + [0] * (BLOCK_SIZE_BYTES - NONCE_LENGTH_BYTES)
-
-        def next_value(self):
-            temp = self.__value
-            self.__value = inc(self.__value)
-            return temp
-
-    decrypted_data = aes_ctr_decrypt(cipher, key, Counter())
     plaintext = intlist_to_bytes(decrypted_data)
 
     return plaintext
@@ -290,6 +310,47 @@ def next_value(self):
                       0x67, 0x4a, 0xed, 0xde, 0xc5, 0x31, 0xfe, 0x18, 0x0d, 0x63, 0x8c, 0x80, 0xc0, 0xf7, 0x70, 0x07)
 
 
+def key_expansion(data):
+    """
+    Generate key schedule
+
+    @param {int[]} data  16/24/32-Byte cipher key
+    @returns {int[]}     176/208/240-Byte expanded key
+    """
+    data = data[:]  # copy
+    rcon_iteration = 1
+    key_size_bytes = len(data)
+    expanded_key_size_bytes = (key_size_bytes // 4 + 7) * BLOCK_SIZE_BYTES
+
+    while len(data) < expanded_key_size_bytes:
+        temp = data[-4:]
+        temp = key_schedule_core(temp, rcon_iteration)
+        rcon_iteration += 1
+        data += xor(temp, data[-key_size_bytes: 4 - key_size_bytes])
+
+        for _ in range(3):
+            temp = data[-4:]
+            data += xor(temp, data[-key_size_bytes: 4 - key_size_bytes])
+
+        if key_size_bytes == 32:
+            temp = data[-4:]
+            temp = sub_bytes(temp)
+            data += xor(temp, data[-key_size_bytes: 4 - key_size_bytes])
+
+        for _ in range(3 if key_size_bytes == 32 else 2 if key_size_bytes == 24 else 0):
+            temp = data[-4:]
+            data += xor(temp, data[-key_size_bytes: 4 - key_size_bytes])
+    data = data[:expanded_key_size_bytes]
+
+    return data
+
+
+def iter_vector(iv):
+    while True:
+        yield iv
+        iv = inc(iv)
+
+
 def sub_bytes(data):
     return [SBOX[x] for x in data]
 
@@ -315,7 +376,7 @@ def xor(data1, data2):
 
 
 def rijndael_mul(a, b):
-    if(a == 0 or b == 0):
+    if a == 0 or b == 0:
         return 0
     return RIJNDAEL_EXP_TABLE[(RIJNDAEL_LOG_TABLE[a] + RIJNDAEL_LOG_TABLE[b]) % 0xFF]
 
@@ -359,6 +420,20 @@ def shift_rows_inv(data):
     return data_shifted
 
 
+def shift_block(data):
+    data_shifted = []
+
+    bit = 0
+    for n in data:
+        if bit:
+            n |= 0x100
+        bit = n & 1
+        n >>= 1
+        data_shifted.append(n)
+
+    return data_shifted
+
+
 def inc(data):
     data = data[:]  # copy
     for i in range(len(data) - 1, -1, -1):
@@ -370,4 +445,50 @@ def inc(data):
     return data
 
 
-__all__ = ['aes_encrypt', 'key_expansion', 'aes_ctr_decrypt', 'aes_cbc_decrypt', 'aes_decrypt_text']
+def block_product(block_x, block_y):
+    # NIST SP 800-38D, Algorithm 1
+
+    if len(block_x) != BLOCK_SIZE_BYTES or len(block_y) != BLOCK_SIZE_BYTES:
+        raise ValueError("Length of blocks need to be %d bytes" % BLOCK_SIZE_BYTES)
+
+    block_r = [0xE1] + [0] * (BLOCK_SIZE_BYTES - 1)
+    block_v = block_y[:]
+    block_z = [0] * BLOCK_SIZE_BYTES
+
+    for i in block_x:
+        for bit in range(7, -1, -1):
+            if i & (1 << bit):
+                block_z = xor(block_z, block_v)
+
+            do_xor = block_v[-1] & 1
+            block_v = shift_block(block_v)
+            if do_xor:
+                block_v = xor(block_v, block_r)
+
+    return block_z
+
+
+def ghash(subkey, data):
+    # NIST SP 800-38D, Algorithm 2
+
+    if len(data) % BLOCK_SIZE_BYTES:
+        raise ValueError("Length of data should be %d bytes" % BLOCK_SIZE_BYTES)
+
+    last_y = [0] * BLOCK_SIZE_BYTES
+    for i in range(0, len(data), BLOCK_SIZE_BYTES):
+        block = data[i : i + BLOCK_SIZE_BYTES]  # noqa: E203
+        last_y = block_product(xor(last_y, block), subkey)
+
+    return last_y
+
+
+__all__ = [
+    'aes_ctr_decrypt',
+    'aes_cbc_decrypt',
+    'aes_cbc_decrypt_bytes',
+    'aes_decrypt_text',
+    'aes_encrypt',
+    'aes_gcm_decrypt_and_verify',
+    'aes_gcm_decrypt_and_verify_bytes',
+    'key_expansion'
+]

yt_dlp/cookies.py

@@ -9,17 +9,14 @@
 from datetime import datetime, timedelta, timezone
 from hashlib import pbkdf2_hmac
 
-from yt_dlp.aes import aes_cbc_decrypt
+from .aes import aes_cbc_decrypt_bytes, aes_gcm_decrypt_and_verify_bytes
-from yt_dlp.compat import (
+from .compat import (
     compat_b64decode,
     compat_cookiejar_Cookie,
-    compat_pycrypto_AES
 )
-from yt_dlp.utils import (
+from .utils import (
     bug_reports_message,
-    bytes_to_intlist,
     expand_path,
-    intlist_to_bytes,
     process_communicate_or_kill,
     YoutubeDLCookieJar,
 )
@@ -395,11 +392,6 @@ def decrypt(self, encrypted_value):
             if self._v10_key is None:
                 self._logger.warning('cannot decrypt v10 cookies: no key found', only_once=True)
                 return None
-            elif not compat_pycrypto_AES:
-                self._logger.warning('cannot decrypt cookie as the `pycryptodome` module is not installed. '
-                                     'Please install by running `python3 -m pip install pycryptodome`',
-                                     only_once=True)
-                return None
 
             # https://chromium.googlesource.com/chromium/src/+/refs/heads/main/components/os_crypt/os_crypt_win.cc
             #   kNonceLength
@@ -643,21 +635,18 @@ def pbkdf2_sha1(password, salt, iterations, key_length):
 
 
 def _decrypt_aes_cbc(ciphertext, key, logger, initialization_vector=b' ' * 16):
-    plaintext = aes_cbc_decrypt(bytes_to_intlist(ciphertext),
+    plaintext = aes_cbc_decrypt_bytes(ciphertext, key, initialization_vector)
-                                bytes_to_intlist(key),
-                                bytes_to_intlist(initialization_vector))
     padding_length = plaintext[-1]
     try:
-        return intlist_to_bytes(plaintext[:-padding_length]).decode('utf-8')
+        return plaintext[:-padding_length].decode('utf-8')
     except UnicodeDecodeError:
         logger.warning('failed to decrypt cookie because UTF-8 decoding failed. Possibly the key is wrong?', only_once=True)
         return None
 
 
 def _decrypt_aes_gcm(ciphertext, key, nonce, authentication_tag, logger):
-    cipher = compat_pycrypto_AES.new(key, compat_pycrypto_AES.MODE_GCM, nonce)
     try:
-        plaintext = cipher.decrypt_and_verify(ciphertext, authentication_tag)
+        plaintext = aes_gcm_decrypt_and_verify_bytes(ciphertext, key, authentication_tag, nonce)
     except ValueError:
         logger.warning('failed to decrypt cookie because the MAC check failed. Possibly the key is wrong?', only_once=True)
         return None