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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1 | pmbaty | 1 | #include <stdio.h> |
| 2 | #include <stdlib.h> |
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| 3 | #include <string.h> |
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| 4 | |||
| 5 | |||
| 6 | int main (int argc, char **argv) |
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| 7 | { |
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| 8 | // Carmageddon data file decryption utility |
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| 9 | |||
| 10 | #define DECODE_CHAR_WITH_KEY(c,key,should_bump_seed) do { \ |
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| 11 | if (c == '\t') \ |
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| 12 | c = 0x80; \ |
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| 13 | c -= 32; \ |
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| 14 | if ((c & 0x80) == 0) \ |
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| 15 | c ^= (key)[seed] & 0x7f; \ |
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| 16 | c += 32; \ |
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| 17 | if (c == 0x80) \ |
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| 18 | c = '\t'; \ |
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| 19 | if (should_bump_seed) \ |
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| 20 | seed = (seed + 7) % 16; \ |
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| 21 | } while (0) |
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| 22 | |||
| 23 | const char *key1 = "\x6c\x1b\x99\x5f\xb9\xcd\x5f\x13\xcb\x04\x20\x0e\x5e\x1c\xa1\x0e"; |
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| 24 | const char *key2 = "\x67\xa8\xd6\x26\xb6\xdd\x45\x1b\x32\x7e\x22\x13\x15\xc2\x94\x37"; |
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| 25 | const char *key_to_use; |
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| 26 | char line_buffer[1024]; |
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| 27 | char *file_pathname = NULL; |
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| 28 | int should_fix_b0rken_crypto = 1; |
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| 29 | unsigned char c; |
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| 30 | int seed; |
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| 31 | int len; |
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| 32 | int i; |
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| 33 | FILE *fp; |
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| 34 | |||
| 35 | // process command-line arguments |
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| 36 | for (i = 1; i < argc; i++) |
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| 37 | { |
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| 38 | if (strcmp (argv[i], "--dont-fix-b0rken-carmageddon-crypto") == 0) |
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| 39 | should_fix_b0rken_crypto = 0; |
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| 40 | else if (file_pathname == NULL) |
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| 41 | file_pathname = argv[i]; |
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| 42 | } |
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| 43 | |||
| 44 | // consistency check |
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| 45 | if (file_pathname == NULL) |
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| 46 | { |
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| 47 | fprintf (stderr, "usage: %s [--dont-fix-b0rken-carmageddon-crypto] <FILE.TXT>\n", argv[0]); |
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| 48 | exit (1); |
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| 49 | } |
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| 50 | |||
| 51 | // open the Carmageddon data file to decrypt |
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| 52 | fp = fopen (file_pathname, "rb"); |
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| 53 | if (fp == NULL) |
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| 54 | { |
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| 55 | fprintf (stderr, "error: couldn't open '%s'\n", argv[1]); |
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| 56 | exit (1); |
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| 57 | } |
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| 58 | |||
| 59 | // read it line per line |
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| 60 | while (fgets (line_buffer, sizeof (line_buffer), fp) != NULL) |
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| 61 | { |
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| 62 | len = (int) strlen (line_buffer); // measure line length |
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| 63 | |||
| 64 | // is this line encrypted ? |
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| 65 | if (line_buffer[0] == '@') |
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| 66 | { |
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| 67 | // chop off all trailing CR and LFs from the input data |
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| 68 | while ((len > 0) && ((line_buffer[len - 1] == '\r') || (line_buffer[len - 1] == '\n'))) |
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| 69 | line_buffer[--len] = 0; |
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| 70 | |||
| 71 | // start with the first key and initialize the algorithm seed to the remainder of the length of data / 16 |
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| 72 | key_to_use = key1; |
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| 73 | seed = (len - 1) % 16; |
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| 74 | |||
| 75 | // for each encrypted character... |
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| 76 | for (i = 1; i < len; i++) |
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| 77 | { |
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| 78 | c = line_buffer[i]; // quick access to character |
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| 79 | |||
| 80 | // when loading game data, Carmageddon does not switch the XOR cypher when the comments start |
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| 81 | if (should_fix_b0rken_crypto && (i >= 3) && (line_buffer[i - 2] == '/') && (line_buffer[i - 3] == '/')) |
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| 82 | { |
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| 83 | DECODE_CHAR_WITH_KEY (c, key2, 0); // decode character with the alternate key, but don't advance the seed |
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| 84 | if ((i > 4) || (c == ' ') || (c == '\t') || (c == '/')) |
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| 85 | key_to_use = key2; // if this character looks sensible enough, it's time to swap keys |
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| 86 | c = line_buffer[i]; // reload character after decryption attempt with alternate key |
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| 87 | } |
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| 88 | |||
| 89 | DECODE_CHAR_WITH_KEY (c, key_to_use, 1); // decode character and advance the seed |
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| 90 | line_buffer[i - 1] = c; // write decoded character one position backwards to erase the '@' prefix |
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| 91 | } |
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| 92 | |||
| 93 | line_buffer[i - 1] = 0; // terminate the decrypted string properly |
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| 94 | } |
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| 95 | |||
| 96 | // chop off all trailing CR and LFs from the decrypted data once again |
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| 97 | while ((len > 0) && ((line_buffer[len - 1] == '\r') || (line_buffer[len - 1] == '\n'))) |
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| 98 | line_buffer[--len] = 0; |
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| 99 | |||
| 100 | fprintf (stdout, "%s\n", line_buffer); // dump decrypted line to the standard output, with a proper newline at the end |
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| 101 | } |
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| 102 | |||
| 103 | fclose (fp); // close the input file |
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| 104 | exit (0); // and exit with a success code |
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| 105 | } |