moth/include/arc4.c

128 lines
2.4 KiB
C

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