rzhxeo
12 years ago
1 changed files with 200 additions and 0 deletions
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youtube_dl/aes.py
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| @ -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 | |||