mirror of https://github.com/dirtbags/moth.git
Bring arc4 back in
This commit is contained in:
Neale Pickett
parent
63cad13c72
commit
a86f5a1bea
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@ -1,11 +1,14 @@
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CFLAGS = -Wall -Werror
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TARGETS = claim.cgi puzzler.cgi puzzles.cgi
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TARGETS += pointscli
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TARGETS += pointscli arc4
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all: build
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build: $(TARGETS)
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arc4: CFLAGS += -DARC4_MAIN
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arc4: arc4.o
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pointscli: pointscli.o common.o
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puzzles.cgi: puzzles.cgi.o common.o
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@ -0,0 +1,230 @@
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#include <stdint.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include "arc4.h"
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#define swap(a, b) do {uint8_t _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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/* Create a nonce as an arc4 stream with key=seed */
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void
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arc4_nonce(uint8_t *nonce, size_t noncelen,
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void *seed, size_t seedlen)
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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, seed, seedlen);
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for (i = 0; i < noncelen; i += 1) {
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nonce[i] = arc4_out(&ctx);
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}
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}
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/***************************************************
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*
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* Psuedo Random Number Generation
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*
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*/
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static struct arc4_ctx prng_ctx;
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static int prng_initialized = 0;
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void
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arc4_rand_seed(const uint8_t *seed, size_t seedlen)
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{
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arc4_init(&prng_ctx, seed, seedlen);
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prng_initialized = 1;
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}
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static void
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arc4_rand_autoseed()
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{
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if (! prng_initialized) {
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uint8_t key[ARC4_KEYLEN];
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FILE *urandom;
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/* Open /dev/urandom or die trying */
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urandom = fopen("/dev/urandom", "r");
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if (! urandom) {
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perror("Opening /dev/urandom");
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abort();
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}
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setbuf(urandom, NULL);
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fread(&key, sizeof(key), 1, urandom);
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fclose(urandom);
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arc4_rand_seed(key, sizeof(key));
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}
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}
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uint8_t
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arc4_rand8()
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{
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arc4_rand_autoseed();
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return arc4_out(&prng_ctx);
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}
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uint32_t
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arc4_rand32()
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{
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arc4_rand_autoseed();
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return ((arc4_out(&prng_ctx) << 0) |
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(arc4_out(&prng_ctx) << 8) |
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(arc4_out(&prng_ctx) << 16) |
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(arc4_out(&prng_ctx) << 24));
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}
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/*****************************************
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*
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* Stream operations
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*
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*/
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ssize_t
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arc4_encrypt_stream(FILE *out, FILE *in,
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const uint8_t *key, size_t keylen)
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{
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struct arc4_ctx ctx;
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uint32_t seed = arc4_rand32();
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uint8_t nonce[ARC4_KEYLEN];
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ssize_t written = 0;
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int i;
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fwrite("arc4", 4, 1, out);
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fwrite(&seed, sizeof(seed), 1, out);
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arc4_nonce(nonce, sizeof(nonce), &seed, sizeof(seed));
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for (i = 0; i < keylen; i += 1) {
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nonce[i] ^= key[i];
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}
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arc4_init(&ctx, nonce, sizeof(nonce));
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while (1) {
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int c = fgetc(in);
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if (EOF == c) break;
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fputc((uint8_t)c ^ arc4_out(&ctx), out);
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written += 1;
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}
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return written;
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}
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ssize_t
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arc4_decrypt_stream(FILE *out, FILE *in,
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const uint8_t *key, size_t keylen)
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{
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struct arc4_ctx ctx;
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uint32_t seed;
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uint8_t nonce[ARC4_KEYLEN];
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ssize_t written = 0;
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char sig[4];
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int i;
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fread(&sig, sizeof(sig), 1, in);
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if (memcmp(sig, "arc4", 4)) {
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return -1;
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}
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fread(&seed, sizeof(seed), 1, in);
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arc4_nonce(nonce, sizeof(nonce), &seed, sizeof(seed));
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for (i = 0; i < keylen; i += 1) {
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nonce[i] ^= key[i];
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}
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arc4_init(&ctx, nonce, sizeof(nonce));
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while (1) {
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int c = fgetc(in);
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if (EOF == c) break;
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fputc((uint8_t)c ^ arc4_out(&ctx), out);
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written += 1;
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}
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return written;
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}
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#ifdef ARC4_MAIN
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#include <sysexits.h>
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#include <unistd.h>
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int
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main(int argc, char *argv[])
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{
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uint8_t key[ARC4_KEYLEN] = {0};
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size_t keylen;
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/* Read key and initialize context */
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{
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char *ekey = getenv("KEY");
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if (ekey) {
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keylen = strlen(ekey);
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memcpy(key, ekey, keylen);
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} else {
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keylen = read(3, key, sizeof(key));
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if (-1 == keylen) {
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fprintf(stderr, "error: must specify key.\n");
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return 1;
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}
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}
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}
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if (! argv[1]) {
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if (-1 == arc4_decrypt_stream(stdout, stdin, key, keylen)) {
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fprintf(stderr, "error: not an arc4 stream.\n");
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return 1;
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}
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} else if (0 == strcmp(argv[1], "-e")) {
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arc4_encrypt_stream(stdout, stdin, key, keylen);
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} else {
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fprintf(stderr, "Usage: %s [-e] <PLAINTEXT\n", argv[0]);
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fprintf(stderr, "\n");
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fprintf(stderr, "You must pass in a key on fd 3 or in the environment variable KEY.\n");
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return EX_USAGE;
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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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@ -0,0 +1,40 @@
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#ifndef __ARC4_H__
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#define __ARC4_H__
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#define ARC4_KEYLEN 256
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struct arc4_ctx {
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uint8_t S[256];
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uint8_t i;
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uint8_t j;
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};
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/* Stream operations */
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ssize_t
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arc4_encrypt_stream(FILE *out, FILE *in,
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const uint8_t *key, size_t keylen);
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ssize_t
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arc4_decrypt_stream(FILE *out, FILE *in,
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const uint8_t *key, size_t keylen);
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/* Auto-seeding Psuedo Random Number Generator */
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void arc4_rand_seed(const uint8_t *seed, size_t seedlen);
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uint8_t arc4_rand8();
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uint32_t arc4_rand32();
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/* Low-level operations */
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void arc4_init(struct arc4_ctx *ctx, const uint8_t *key, size_t keylen);
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uint8_t arc4_out(struct arc4_ctx *ctx);
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void arc4_crypt(struct arc4_ctx *ctx,
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uint8_t *obuf, const uint8_t *ibuf, size_t buflen);
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void arc4_crypt_buffer(const uint8_t *key, size_t keylen,
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uint8_t *buf, size_t buflen);
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void arc4_nonce(uint8_t *nonce, size_t noncelen, void *seed, size_t seedlen);
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#endif
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