| 1 | /* |
| 2 | * xorimage.c - partially based on OpenWrt's addpattern.c |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License as published by |
| 6 | * the Free Software Foundation; either version 2 of the License, or |
| 7 | * (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 12 | * General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, write to the Free Software |
| 16 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 17 | */ |
| 18 | |
| 19 | |
| 20 | #include <stdio.h> |
| 21 | #include <stdlib.h> |
| 22 | #include <string.h> |
| 23 | #include <stdint.h> |
| 24 | #include <time.h> |
| 25 | #include <unistd.h> |
| 26 | #include <sys/stat.h> |
| 27 | |
| 28 | static char default_pattern[] = "12345678"; |
| 29 | |
| 30 | |
| 31 | int xor_data(uint8_t *data, size_t len, const uint8_t *pattern, int p_len, int p_off) |
| 32 | { |
| 33 | int offset = p_off; |
| 34 | while (len--) { |
| 35 | *data ^= pattern[offset]; |
| 36 | data++; |
| 37 | offset = (offset + 1) % p_len; |
| 38 | } |
| 39 | return offset; |
| 40 | } |
| 41 | |
| 42 | |
| 43 | void usage(void) __attribute__ (( __noreturn__ )); |
| 44 | |
| 45 | void usage(void) |
| 46 | { |
| 47 | fprintf(stderr, "Usage: xorimage [-i infile] [-o outfile] [-p <pattern>]\n"); |
| 48 | exit(EXIT_FAILURE); |
| 49 | } |
| 50 | |
| 51 | |
| 52 | int main(int argc, char **argv) |
| 53 | { |
| 54 | char buf[1024]; /* keep this at 1k or adjust garbage calc below */ |
| 55 | FILE *in = stdin; |
| 56 | FILE *out = stdout; |
| 57 | char *ifn = NULL; |
| 58 | char *ofn = NULL; |
| 59 | const char *pattern = default_pattern; |
| 60 | int c; |
| 61 | int v0, v1, v2; |
| 62 | size_t n; |
| 63 | int p_len, p_off = 0; |
| 64 | |
| 65 | while ((c = getopt(argc, argv, "i:o:p:h")) != -1) { |
| 66 | switch (c) { |
| 67 | case 'i': |
| 68 | ifn = optarg; |
| 69 | break; |
| 70 | case 'o': |
| 71 | ofn = optarg; |
| 72 | break; |
| 73 | case 'p': |
| 74 | pattern = optarg; |
| 75 | break; |
| 76 | case 'h': |
| 77 | default: |
| 78 | usage(); |
| 79 | } |
| 80 | } |
| 81 | |
| 82 | if (optind != argc || optind == 1) { |
| 83 | fprintf(stderr, "illegal arg \"%s\"\n", argv[optind]); |
| 84 | usage(); |
| 85 | } |
| 86 | |
| 87 | if (ifn && !(in = fopen(ifn, "r"))) { |
| 88 | fprintf(stderr, "can not open \"%s\" for reading\n", ifn); |
| 89 | usage(); |
| 90 | } |
| 91 | |
| 92 | if (ofn && !(out = fopen(ofn, "w"))) { |
| 93 | fprintf(stderr, "can not open \"%s\" for writing\n", ofn); |
| 94 | usage(); |
| 95 | } |
| 96 | |
| 97 | p_len = strlen(pattern); |
| 98 | |
| 99 | if (p_len == 0) { |
| 100 | fprintf(stderr, "pattern cannot be empty\n"); |
| 101 | usage(); |
| 102 | } |
| 103 | |
| 104 | |
| 105 | while ((n = fread(buf, 1, sizeof(buf), in)) > 0) { |
| 106 | if (n < sizeof(buf)) { |
| 107 | if (ferror(in)) { |
| 108 | FREAD_ERROR: |
| 109 | fprintf(stderr, "fread error\n"); |
| 110 | return EXIT_FAILURE; |
| 111 | } |
| 112 | } |
| 113 | |
| 114 | p_off = xor_data(buf, n, pattern, p_len, p_off); |
| 115 | |
| 116 | if (!fwrite(buf, n, 1, out)) { |
| 117 | FWRITE_ERROR: |
| 118 | fprintf(stderr, "fwrite error\n"); |
| 119 | return EXIT_FAILURE; |
| 120 | } |
| 121 | } |
| 122 | |
| 123 | if (ferror(in)) { |
| 124 | goto FREAD_ERROR; |
| 125 | } |
| 126 | |
| 127 | if (fflush(out)) { |
| 128 | goto FWRITE_ERROR; |
| 129 | } |
| 130 | |
| 131 | fclose(in); |
| 132 | fclose(out); |
| 133 | |
| 134 | return EXIT_SUCCESS; |
| 135 | } |
| 136 | |
