diff options
| -rw-r--r-- | youtube_dl/aes.py | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/youtube_dl/aes.py b/youtube_dl/aes.py new file mode 100644 index 000000000..2fa9238e3 --- /dev/null +++ b/youtube_dl/aes.py @@ -0,0 +1,200 @@ +__all__ = ['aes_encrypt', 'key_expansion', 'aes_ctr_decrypt', 'aes_decrypt_text'] + +import base64 +from math import ceil + +BLOCK_SIZE_BYTES = 16 + +def aes_ctr_decrypt(data, key, counter): + """ + 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) + returns the next counter block + @returns {int[]} decrypted data + """ + expanded_key = key_expansion(key) + block_count = int(ceil(float(len(data)) / BLOCK_SIZE_BYTES)) + + decrypted_data=[] + for i in range(block_count): + counter_block = counter.next_value() + 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) + decrypted_data = decrypted_data[:len(data)] + + return decrypted_data + +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 aes_encrypt(data, expanded_key): + """ + Encrypt one block with aes + + @param {int[]} data 16-Byte state + @param {int[]} expanded_key 176/208/240-Byte expanded key + @returns {int[]} 16-Byte cipher + """ + rounds = len(expanded_key) / BLOCK_SIZE_BYTES - 1 + + data = xor(data, expanded_key[:BLOCK_SIZE_BYTES]) + for i in range(1, rounds+1): + data = sub_bytes(data) + data = shift_rows(data) + if i != rounds: + data = mix_columns(data) + data = xor(data, expanded_key[i*BLOCK_SIZE_BYTES : (i+1)*BLOCK_SIZE_BYTES]) + + return data + +def aes_decrypt_text(data, password, key_size_bytes): + """ + Decrypt text + - The first 8 Bytes of decoded 'data' are the 8 high Bytes of the counter + - The cipher key is retrieved by encrypting the first 16 Byte of 'password' + with the first 'key_size_bytes' Bytes from 'password' (if necessary filled with 0's) + - Mode of operation is 'counter' + + @param {str} data Base64 encoded string + @param {str,unicode} password Password (will be encoded with utf-8) + @param {int} key_size_bytes Possible values: 16 for 128-Bit, 24 for 192-Bit or 32 for 256-Bit + @returns {str} Decrypted data + """ + NONCE_LENGTH_BYTES = 8 + + data = map(lambda c: ord(c), base64.b64decode(data)) + password = map(lambda c: ord(c), password.encode('utf-8')) + + key = password[:key_size_bytes] + [0]*(key_size_bytes - len(password)) + key = aes_encrypt(key[:BLOCK_SIZE_BYTES], key_expansion(key)) * (key_size_bytes / BLOCK_SIZE_BYTES) + + nonce = data[:NONCE_LENGTH_BYTES] + cipher = data[NONCE_LENGTH_BYTES:] + + class Counter: + __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 = ''.join(map(lambda x: chr(x), decrypted_data)) + + return plaintext + +RCON = (0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36) +SBOX = (0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76, + 0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0, + 0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15, + 0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75, + 0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84, + 0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF, + 0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8, + 0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2, + 0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73, + 0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB, + 0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79, + 0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08, + 0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A, + 0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E, + 0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF, + 0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16) +MIX_COLUMN_MATRIX = ((2,3,1,1), + (1,2,3,1), + (1,1,2,3), + (3,1,1,2)) + +def sub_bytes(data): + return map(lambda x: SBOX[x], data) + +def rotate(data): + return data[1:] + [data[0]] + +def key_schedule_core(data, rcon_iteration): + data = rotate(data) + data = sub_bytes(data) + data[0] = data[0] ^ RCON[rcon_iteration] + + return data + +def xor(data1, data2): + return map(lambda (x,y): x^y, zip(data1, data2)) + +def mix_column(data): + data_mixed = [] + for row in range(4): + mixed = 0 + for column in range(4): + addend = data[column] + if MIX_COLUMN_MATRIX[row][column] in (2,3): + addend <<= 1 + if addend > 0xff: + addend &= 0xff + addend ^= 0x1b + if MIX_COLUMN_MATRIX[row][column] == 3: + addend ^= data[column] + mixed ^= addend & 0xff + data_mixed.append(mixed) + return data_mixed + +def mix_columns(data): + data_mixed = [] + for i in range(4): + column = data[i*4 : (i+1)*4] + data_mixed += mix_column(column) + return data_mixed + +def shift_rows(data): + data_shifted = [] + for column in range(4): + for row in range(4): + data_shifted.append( data[((column + row) & 0b11) * 4 + row] ) + return data_shifted + +def inc(data): + data = data[:] # copy + for i in range(len(data)-1,-1,-1): + if data[i] == 255: + data[i] = 0 + else: + data[i] = data[i] + 1 + break + return data |