mirror of https://github.com/dirtbags/moth.git
128 lines
2.4 KiB
C
128 lines
2.4 KiB
C
#include <stdint.h>
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#include <stdlib.h>
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#include "arc4.h"
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#define swap(a, b) do {int _swap=a; a=b, b=_swap;} while (0)
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void
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arc4_init(struct arc4_ctx *ctx, uint8_t const *key, size_t keylen)
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{
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int i;
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int j = 0;
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for (i = 0; i < 256; i += 1) {
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ctx->S[i] = i;
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}
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for (i = 0; i < 256; i += 1) {
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j = (j + ctx->S[i] + key[i % keylen]) % 256;
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swap(ctx->S[i], ctx->S[j]);
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}
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ctx->i = 0;
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ctx->j = 0;
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}
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uint8_t
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arc4_out(struct arc4_ctx *ctx)
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{
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ctx->i = (ctx->i + 1) % 256;
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ctx->j = (ctx->j + ctx->S[ctx->i]) % 256;
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swap(ctx->S[ctx->i], ctx->S[ctx->j]);
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return ctx->S[(ctx->S[ctx->i] + ctx->S[ctx->j]) % 256];
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}
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void
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arc4_crypt(struct arc4_ctx *ctx,
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uint8_t *obuf, const uint8_t *ibuf, size_t buflen)
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{
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size_t k;
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for (k = 0; k < buflen; k += 1) {
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obuf[k] = ibuf[k] ^ arc4_out(ctx);
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}
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}
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void
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arc4_crypt_buffer(const uint8_t *key, size_t keylen,
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uint8_t *buf, size_t buflen)
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{
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struct arc4_ctx ctx;
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arc4_init(&ctx, key, keylen);
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arc4_crypt(&ctx, buf, buf, buflen);
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}
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void
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arc4_hash(uint8_t const *buf, size_t buflen,
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uint8_t *hash)
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{
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struct arc4_ctx ctx;
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int i;
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arc4_init(&ctx, buf, buflen);
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for (i = 0; i < ARC4_HASHLEN; i += 1) {
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hash[i] = arc4_out(&ctx);
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}
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}
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#ifdef ARC4_MAIN
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#include <stdio.h>
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#include <sysexits.h>
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#include <string.h>
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int
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main(int argc, char *argv[])
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{
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struct arc4_ctx ctx;
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/* Read key and initialize context */
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{
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uint8_t key[256];
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size_t keylen = 0;
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char *ekey = getenv("KEY");
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FILE *f;
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if (argc == 2) {
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if (! (f = fopen(argv[1], "r"))) {
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perror(argv[0]);
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}
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} else {
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f = fdopen(3, "r");
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}
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if (f) {
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keylen = fread(key, 1, sizeof(key), f);
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fclose(f);
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} else if (ekey) {
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keylen = strlen(ekey);
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if (keylen > sizeof(key)) {
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keylen = sizeof(key);
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}
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memcpy(key, ekey, keylen);
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}
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if (0 == keylen) {
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fprintf(stderr, "Usage: %s [KEYFILE] <PLAINTEXT\n", argv[0]);
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fprintf(stderr, "\n");
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fprintf(stderr, "You can also pass in the key on fd 3 or in\n");
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fprintf(stderr, "$KEY; omit KEYFILE in this case.\n");
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return EX_IOERR;
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}
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arc4_init(&ctx, key, (size_t)keylen);
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}
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/* Encrypt */
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while (1) {
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int c = getchar();
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if (EOF == c) break;
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putchar(c ^ arc4_out(&ctx));
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}
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return 0;
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}
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#endif /* ARC4_MAIN */
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