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94 lines
3.8 KiB
C
94 lines
3.8 KiB
C
#ifndef _FSB_ENCRYPTED_STREAMFILE_H_
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#define _FSB_ENCRYPTED_STREAMFILE_H_
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#define FSB_KEY_MAX 0x80 /* known max ~0x33 */
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typedef struct {
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uint8_t key[FSB_KEY_MAX];
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size_t key_size;
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int is_alt;
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} fsb_decryption_data;
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/* Encrypted FSB info from guessfsb and fsbext */
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static size_t fsb_decryption_read(STREAMFILE* sf, uint8_t *dest, off_t offset, size_t length, fsb_decryption_data* data) {
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static const unsigned char reverse_bits_table[] = { /* LUT to simplify, could use some bitswap function */
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//00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
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0x00,0x80,0x40,0xC0,0x20,0xA0,0x60,0xE0,0x10,0x90,0x50,0xD0,0x30,0xB0,0x70,0xF0, //00
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0x08,0x88,0x48,0xC8,0x28,0xA8,0x68,0xE8,0x18,0x98,0x58,0xD8,0x38,0xB8,0x78,0xF8, //10
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0x04,0x84,0x44,0xC4,0x24,0xA4,0x64,0xE4,0x14,0x94,0x54,0xD4,0x34,0xB4,0x74,0xF4, //20
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0x0C,0x8C,0x4C,0xCC,0x2C,0xAC,0x6C,0xEC,0x1C,0x9C,0x5C,0xDC,0x3C,0xBC,0x7C,0xFC, //30
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0x02,0x82,0x42,0xC2,0x22,0xA2,0x62,0xE2,0x12,0x92,0x52,0xD2,0x32,0xB2,0x72,0xF2, //40
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0x0A,0x8A,0x4A,0xCA,0x2A,0xAA,0x6A,0xEA,0x1A,0x9A,0x5A,0xDA,0x3A,0xBA,0x7A,0xFA, //50
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0x06,0x86,0x46,0xC6,0x26,0xA6,0x66,0xE6,0x16,0x96,0x56,0xD6,0x36,0xB6,0x76,0xF6, //60
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0x0E,0x8E,0x4E,0xCE,0x2E,0xAE,0x6E,0xEE,0x1E,0x9E,0x5E,0xDE,0x3E,0xBE,0x7E,0xFE, //70
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0x01,0x81,0x41,0xC1,0x21,0xA1,0x61,0xE1,0x11,0x91,0x51,0xD1,0x31,0xB1,0x71,0xF1, //80
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0x09,0x89,0x49,0xC9,0x29,0xA9,0x69,0xE9,0x19,0x99,0x59,0xD9,0x39,0xB9,0x79,0xF9, //90
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0x05,0x85,0x45,0xC5,0x25,0xA5,0x65,0xE5,0x15,0x95,0x55,0xD5,0x35,0xB5,0x75,0xF5, //A0
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0x0D,0x8D,0x4D,0xCD,0x2D,0xAD,0x6D,0xED,0x1D,0x9D,0x5D,0xDD,0x3D,0xBD,0x7D,0xFD, //B0
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0x03,0x83,0x43,0xC3,0x23,0xA3,0x63,0xE3,0x13,0x93,0x53,0xD3,0x33,0xB3,0x73,0xF3, //C0
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0x0B,0x8B,0x4B,0xCB,0x2B,0xAB,0x6B,0xEB,0x1B,0x9B,0x5B,0xDB,0x3B,0xBB,0x7B,0xFB, //D0
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0x07,0x87,0x47,0xC7,0x27,0xA7,0x67,0xE7,0x17,0x97,0x57,0xD7,0x37,0xB7,0x77,0xF7, //E0
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0x0F,0x8F,0x4F,0xCF,0x2F,0xAF,0x6F,0xEF,0x1F,0x9F,0x5F,0xDF,0x3F,0xBF,0x7F,0xFF //F0
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};
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size_t bytes_read;
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int i;
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bytes_read = read_streamfile(dest, offset, length, sf);
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/* decrypt data (inverted bits and xor) */
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for (i = 0; i < bytes_read; i++) {
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uint8_t xor = data->key[(offset + i) % data->key_size];
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uint8_t val = dest[i];
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if (data->is_alt) {
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dest[i] = reverse_bits_table[val ^ xor];
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}
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else {
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dest[i] = reverse_bits_table[val] ^ xor;
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}
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}
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return bytes_read;
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}
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static STREAMFILE* setup_fsb_streamfile(STREAMFILE* sf, const uint8_t* key, size_t key_size, int is_alt) {
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STREAMFILE* new_sf = NULL;
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fsb_decryption_data io_data = {0};
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size_t io_data_size = sizeof(fsb_decryption_data);
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/* setup decryption with key (external) */
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if (!key_size || key_size >= FSB_KEY_MAX)
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return NULL;
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memcpy(io_data.key, key, key_size);
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io_data.key_size = key_size;
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io_data.is_alt = is_alt;
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/* setup subfile */
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new_sf = open_wrap_streamfile(sf);
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new_sf = open_io_streamfile_f(new_sf, &io_data,io_data_size, fsb_decryption_read,NULL);
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new_sf = open_fakename_streamfile(new_sf, NULL,"fsb");
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return new_sf;
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}
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/* same as above but doesn't open streamfile, so it's a tiny bit faster */
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static bool test_fsb_streamfile(STREAMFILE* sf, const uint8_t* key, size_t key_size, int is_alt) {
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fsb_decryption_data io_data = {0};
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if (!key_size || key_size >= FSB_KEY_MAX)
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return false;
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memcpy(io_data.key, key, key_size);
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io_data.key_size = key_size;
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io_data.is_alt = is_alt;
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/* setup subfile */
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uint8_t tmp[0x04];
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int bytes = fsb_decryption_read(sf, tmp, 0x00, 0x04, &io_data);
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if (bytes != 0x04)
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return false;
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return (get_u32be(tmp) & 0xFFFFFF00) == get_id32be("FSB\0");
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}
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#endif /* _FSB_ENCRYPTED_STREAMFILE_H_ */
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