89 lines
2.1 KiB
C++
89 lines
2.1 KiB
C++
/*
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** Command & Conquer Renegade(tm)
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** Copyright 2025 Electronic Arts Inc.
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**
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** This program is free software: you can redistribute it and/or modify
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** it under the terms of the GNU General Public License as published by
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** the Free Software Foundation, either version 3 of the License, or
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** (at your option) any later version.
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**
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** This program is distributed in the hope that it will be useful,
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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** GNU General Public License for more details.
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**
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** You should have received a copy of the GNU General Public License
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** along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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//
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// rc4.cpp
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// RC4 encryption / decryption
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//
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#include "rc4.h"
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#include <memory.h>
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static unsigned char RC4_Temp_Byte;
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#define RC4_SWAP_BYTE(a,b) RC4_Temp_Byte=a; a=b; b=RC4_Temp_Byte
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//
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// Don't rely on this to zero the key
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//
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RC4Class::RC4Class()
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{
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memset(Key.State, 0, 256);
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Key.X=0;
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Key.Y=0;
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}
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//
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// Setup the encryption key. This must be called before you encrypt/decrypt!
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//
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void RC4Class::Prepare_Key(const unsigned char *key_data_ptr, int key_data_len)
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{
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unsigned char index1;
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unsigned char index2;
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unsigned char *state;
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int counter;
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state = &Key.State[0];
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for (counter = 0; counter < 256; counter++)
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state[counter] = (unsigned char)counter;
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Key.X = 0;
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Key.Y = 0;
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index1 = 0;
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index2 = 0;
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for (counter = 0; counter < 256; counter++) {
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index2 = (unsigned char)(key_data_ptr[index1] + state[counter] + index2);
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RC4_SWAP_BYTE(state[counter], state[index2]);
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index1 = (unsigned char)((index1 + 1) % key_data_len);
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}
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}
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//
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// RC4 in standard mode.
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//
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// This will XOR the buffer with the RC4 stream (like a one time pad).
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//
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void RC4Class::RC4(unsigned char *buffer_ptr, int buffer_len)
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{
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unsigned char x;
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unsigned char y;
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unsigned char *state;
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int counter;
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x = Key.X;
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y = Key.Y;
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state = &Key.State[0];
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for (counter = 0; counter < buffer_len; counter++) {
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x++;
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y = (unsigned char)(y + state[x]);
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RC4_SWAP_BYTE(state[x], state[y]);
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buffer_ptr[counter] ^= state[(state[x] + state[y]) & 255];
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}
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Key.X = x;
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Key.Y = y;
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}
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