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#ifndef __GNUC__
#pragma code_seg( "RTV_TEXT" )
#pragma data_seg( "RTV_DATA" )
#pragma bss_seg( "RTV_BSS" )
#pragma const_seg( "RTV_RD" )
#endif
/*
* Copyright (C) 2002 John Todd Larason <jtl@molehill.org>
*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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.
*/
#include "crypt.h"
#include "md5.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
static void checksum(unsigned char * dest, unsigned const char * src, u32 len,
int checksum_num)
{
static unsigned char extradata[][64] = {{
0x41,0x47,0xc8,0x09, 0xba,0x3c,0x99,0x6a,
0xda,0x09,0x9a,0x0f, 0xc0,0xd3,0x47,0xca,
0xd1,0x95,0x81,0x19, 0xab,0x17,0xc6,0x5f,
0xad,0xea,0xe5,0x75, 0x9c,0x49,0x18,0xa5,
0xdf,0x35,0x46,0x5b, 0x78,0x0e,0xcb,0xc7,
0x8c,0x3e,0xf4,0x90, 0xa2,0xb7,0x8e,0x00,
0x53,0x8d,0x4c,0xab, 0x13,0xa5,0x16,0x00,
0xff,0xb8,0x4b,0x20, 0x29,0x22,0x9d,0xee,
}, {
0xda,0x76,0x5c,0xd4, 0x34,0xc3,0xd7,0x2c,
0xac,0x40,0xb8,0xd8, 0x59,0xbc,0x59,0x34,
0xaa,0xbf,0x89,0xbd, 0x85,0xe8,0x40,0x27,
0x78,0x2b,0x18,0x6e, 0xa6,0x6e,0x5a,0xc6,
0xda,0xe3,0x86,0x84, 0x40,0x14,0x2a,0x23,
0x4f,0x5d,0x38,0x5e, 0x7f,0xd9,0x73,0x7d,
0xe4,0x80,0x3d,0x21, 0x28,0x41,0xf1,0xb2,
0x96,0x43,0x2b,0xcc, 0x0c,0x9d,0x26,0xb9,
}};
rtv_md5_context c;
rtv_md5_starts(&c);
rtv_md5_update(&c, src, len);
rtv_md5_update(&c, extradata[checksum_num], sizeof extradata[checksum_num]);
rtv_md5_finish(&c, dest);
}
static u32 cryptblock(u32 k, char * buf, u32 size)
{
u32 i;
for (i = 0; i < size; i++) {
k = k * 0xb8f7 + 0x15bb9;
buf[i] ^= k;
}
return k;
}
/* cyphertext bytes:
*
* 2, 4, 1, 7 -- key material block 1
* 0, 3, 5, 6 -- unknown/unused
* 8..23 -- checksum(24..end)
* 24..27 -- crypt(0x42ffdfa9)
* 28..31 -- crypt(time_t)
* 32..end -- crypt(text)
*
* it looks like you should be able to decrypt 24..end in one step, after
* getting the key material, if you don't want to do the sanity check first
* and don't mind it all in one buffer
*/
int rtv_decrypt(const char * cyphertext, u32 cyphertext_len,
char * plainbuf, u32 plainbuf_len,
u32 * p_time, u32 * p_plain_len,
int checksum_num)
{
unsigned char key_buf[4];
unsigned char sanity_buf[4];
unsigned char time_buf[4];
unsigned char csum_buf[16];
unsigned char * p;
u32 key;
u32 sanity;
#if VERBOSE_OBFUSC
unsigned char obfusc_buf[4];
u32 obfusc;
#endif
if (plainbuf_len < cyphertext_len - 32)
return -1;
/* unshuffle the key and unxor it */
key_buf[0] = cyphertext[2];
key_buf[1] = cyphertext[4];
key_buf[2] = cyphertext[1];
key_buf[3] = cyphertext[7];
p = key_buf;
key = rtv_to_u32(&p) ^ 0xcb0baf47;
#if VERBOSE_OBFUSC
obfusc_buf[0] = cyphertext[0];
obfusc_buf[1] = cyphertext[3];
obfusc_buf[2] = cyphertext[5];
obfusc_buf[3] = cyphertext[6];
p = key_buf;
obfusc = rtv_to_u32(&p);
//fprintf(stderr, "Key: %ld (0x%lx)\n", (unsigned long)key, (unsigned long)key);
//fprintf(stderr, "Obfusc: %ld (0x%lx)\n", (unsigned long)obfusc, (unsigned long)obfusc);
#endif
/* check the sanity field */
memcpy(sanity_buf, cyphertext + 24, 4);
key = cryptblock(key, (char*)sanity_buf, 4);
p = sanity_buf;
sanity = rtv_to_u32(&p);
if (sanity != 0x42ffdfa9)
return -1;
/* decrypt the time field */
memcpy(time_buf, cyphertext + 28, 4);
key = cryptblock(key, (char*)time_buf, 4);
/* decrypt the actual text */
memcpy(plainbuf, cyphertext + 32, cyphertext_len - 32);
cryptblock(key, (char*)plainbuf, cyphertext_len - 32);
/* check the checksum */
checksum(csum_buf, (unsigned const char*)(cyphertext + 24), cyphertext_len - 24, checksum_num);
if (memcmp(csum_buf, cyphertext + 8, 16) != 0)
return -2;
if (p_plain_len) {
*p_plain_len = cyphertext_len - 32;
}
if (p_time) {
p = time_buf;
*p_time = rtv_to_u32(&p);
#if VERBOSE_OBFUSC
// fprintf(stderr, "Time: %ld (0x%lx)\n", (unsigned long)*p_time, (unsigned long)*p_time);
#endif
}
return 0;
}
int rtv_encrypt(const char * plaintext, u32 plaintext_len,
char * cyphertext, u32 buffer_len, u32 * cyphertext_len,
int checksum_num)
{
u32 key;
u32 t;
u32 obfusc;
unsigned char key_buf[4];
unsigned char obfusc_buf[4];
unsigned char * p;
if (buffer_len < plaintext_len + 32)
return -1;
/* make up a key and obfuscatory material; get the time */
key = rand();
obfusc = rand();
t = (u32)time(NULL);
p = NULL;//getenv("TIMEOFF");
if (p)
t += atoi((char*)p);
/* encrypt the key */
p = key_buf;
rtv_from_u32(&p, key ^ 0xcb0baf47);
p = obfusc_buf;
rtv_from_u32(&p, obfusc);
/* scramble the key and obfusc material */
cyphertext[0] = obfusc_buf[3];
cyphertext[1] = key_buf[2];
cyphertext[2] = key_buf[0];
cyphertext[3] = obfusc_buf[2];
cyphertext[4] = key_buf[1];
cyphertext[5] = obfusc_buf[1];
cyphertext[6] = obfusc_buf[0];
cyphertext[7] = key_buf[3];
/* store the sanity check & time */
p = (unsigned char*)(cyphertext + 24);
rtv_from_u32(&p, 0x42ffdfa9);
rtv_from_u32(&p, t);
/* copy the plaintext */
memcpy(p, plaintext, plaintext_len);
/* encrypt the whole thing */
cryptblock(key, cyphertext+24, plaintext_len+8);
/* fill in the checksum */
checksum((unsigned char*)(cyphertext + 8), (unsigned const char*)(cyphertext + 24), plaintext_len + 8, checksum_num);
/* and we're done */
*cyphertext_len = plaintext_len + 32;
return 0;
}
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