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/*
* xorimage.c - partially based on OpenWrt's addpattern.c
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/stat.h>
static char default_pattern[] = "12345678";
static int is_hex_pattern;
int xor_data(void *data, size_t len, const void *pattern, int p_len, int p_off)
{
const uint8_t *key = pattern;
uint8_t *d = data;
while (len--) {
*d ^= key[p_off];
d++;
p_off = (p_off + 1) % p_len;
}
return p_off;
}
void usage(void) __attribute__ (( __noreturn__ ));
void usage(void)
{
fprintf(stderr, "Usage: xorimage [-i infile] [-o outfile] [-p <pattern>] [-x]\n");
exit(EXIT_FAILURE);
}
int main(int argc, char **argv)
{
char buf[1024]; /* keep this at 1k or adjust garbage calc below */
FILE *in = stdin;
FILE *out = stdout;
char *ifn = NULL;
char *ofn = NULL;
const char *pattern = default_pattern;
char hex_pattern[128];
unsigned int hex_buf;
int c;
size_t n;
int p_len, p_off = 0;
while ((c = getopt(argc, argv, "i:o:p:xh")) != -1) {
switch (c) {
case 'i':
ifn = optarg;
break;
case 'o':
ofn = optarg;
break;
case 'p':
pattern = optarg;
break;
case 'x':
is_hex_pattern = true;
break;
case 'h':
default:
usage();
}
}
if (optind != argc || optind == 1) {
fprintf(stderr, "illegal arg \"%s\"\n", argv[optind]);
usage();
}
if (ifn && !(in = fopen(ifn, "r"))) {
fprintf(stderr, "can not open \"%s\" for reading\n", ifn);
usage();
}
if (ofn && !(out = fopen(ofn, "w"))) {
fprintf(stderr, "can not open \"%s\" for writing\n", ofn);
usage();
}
p_len = strlen(pattern);
if (p_len == 0) {
fprintf(stderr, "pattern cannot be empty\n");
usage();
}
if (is_hex_pattern) {
int i;
if ((p_len / 2) > sizeof(hex_pattern)) {
fprintf(stderr, "provided hex pattern is too long\n");
usage();
}
if (p_len % 2 != 0) {
fprintf(stderr, "the number of characters (hex) is incorrect\n");
usage();
}
for (i = 0; i < (p_len / 2); i++) {
if (sscanf(pattern + (i * 2), "%2x", &hex_buf) < 0) {
fprintf(stderr, "invalid hex digit around %d\n", i * 2);
usage();
}
hex_pattern[i] = (char)hex_buf;
}
}
while ((n = fread(buf, 1, sizeof(buf), in)) > 0) {
if (n < sizeof(buf)) {
if (ferror(in)) {
FREAD_ERROR:
fprintf(stderr, "fread error\n");
return EXIT_FAILURE;
}
}
if (is_hex_pattern) {
p_off = xor_data(buf, n, hex_pattern, (p_len / 2),
p_off);
} else {
p_off = xor_data(buf, n, pattern, p_len, p_off);
}
if (!fwrite(buf, n, 1, out)) {
FWRITE_ERROR:
fprintf(stderr, "fwrite error\n");
return EXIT_FAILURE;
}
}
if (ferror(in)) {
goto FREAD_ERROR;
}
if (fflush(out)) {
goto FWRITE_ERROR;
}
fclose(in);
fclose(out);
return EXIT_SUCCESS;
}
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