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/* This file is part of Nekopack.
Copyright (C) 2017 Jakob Tsar-Fox, All Rights Reserved.
Nekopack is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
Nekopack is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with Nekopack. If not, see <http://www.gnu.org/licenses/>. */
#include "cli.h"
#include "crypto.h"
/* Returns the encryption keys for a given game value. */
key get_encryption_key(game_type game) {
key encryption_key;
switch (game) {
case NEKOPARA_VOLUME_0:
encryption_key.master_key = 0x1548e29c;
encryption_key.initial_fallback_key = 0x9c;
encryption_key.primary_fallback_key = 0xd7;
encryption_key.uses_initial_key = 1;
break;
case NEKOPARA_VOLUME_0_STEAM:
encryption_key.master_key = 0x44528b87;
encryption_key.initial_fallback_key = 0x87;
encryption_key.primary_fallback_key = 0x23;
encryption_key.uses_initial_key = 1;
break;
case NEKOPARA_VOLUME_1:
encryption_key.master_key = 0x1548e29c;
encryption_key.initial_fallback_key = 0x00;
encryption_key.primary_fallback_key = 0xd7;
encryption_key.uses_initial_key = 0;
break;
case NEKOPARA_VOLUME_1_STEAM:
encryption_key.master_key = 0x44528b87;
encryption_key.initial_fallback_key = 0x00;
encryption_key.primary_fallback_key = 0x23;
encryption_key.uses_initial_key = 0;
break;
default:
encryption_key.master_key = 0x00000000;
encryption_key.initial_fallback_key = 0x00;
encryption_key.primary_fallback_key = 0x00;
encryption_key.uses_initial_key = 0;
}
return encryption_key;
}
/* Decrypts the contents of a buffer according to a file key. */
void decrypt_buffer(Bytef *encrypted_buffer, uint64_t buffer_length,
key encryption_key, uint32_t file_key) {
uint32_t xor_key = file_key ^ encryption_key.master_key;
uint8_t initial_key = xor_key & 0xff;
uint8_t primary_key = (xor_key >> 24 ^ xor_key >> 16 ^ \
xor_key >> 8 ^ xor_key) & 0xff;
if (xor_key == 1 && initial_key == 0)
initial_key = encryption_key.initial_fallback_key;
else if (primary_key == 0)
primary_key = encryption_key.primary_fallback_key;
if (encryption_key.uses_initial_key)
encrypted_buffer[0] ^= initial_key;
for (uint64_t i = 0; i < buffer_length; i++) {
encrypted_buffer[i] ^= primary_key;
}
}
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