crypto_rc4.c

Go to the documentation of this file.

// SPDX-FileCopyrightText: 2016 pancake <pancake@nopcode.org>
// SPDX-License-Identifier: LGPL-3.0-only
 
#include <rz_lib.h>
#include <rz_crypto.h>
#include <rz_util.h>
 
struct rc4_state {
    ut8 perm[256];
    ut8 index1;
    ut8 index2;
    int key_size;
};
 
static __inline void swap_bytes(ut8 *a, ut8 *b) {
    if (a != b) {
        ut8 temp = *a;
        *a = *b;
        *b = temp;
    }
}
 
/*
 * Initialize an RC4 state buffer using the supplied key,
 * which can have arbitrary length.
 */
 
static bool rc4_init_state(struct rc4_state *const state, const ut8 *key, int keylen) {
    ut8 j;
    int i;
 
    if (!state || !key || keylen < 1) {
        return false;
    }
    state->key_size = keylen;
    /* Initialize state with identity permutation */
    for (i = 0; i < 256; i++) {
        state->perm[i] = (ut8)i;
    }
    state->index1 = 0;
    state->index2 = 0;
 
    /* Randomize the permutation using key data */
    for (j = i = 0; i < 256; i++) {
        j += state->perm[i] + key[i % keylen];
        swap_bytes(&state->perm[i], &state->perm[j]);
    }
    return true;
}
 
/*
 * Encrypt some data using the supplied RC4 state buffer.
 * The input and output buffers may be the same buffer.
 * Since RC4 is a stream cypher, this function is used
 * for both encryption and decryption.
 */
static void rc4_crypt(struct rc4_state *const state, const ut8 *inbuf, ut8 *outbuf, int buflen) {
    int i;
    ut8 j;
 
    for (i = 0; i < buflen; i++) {
        /* Update modification indices */
        state->index1++;
        state->index2 += state->perm[state->index1];
        /* Modify permutation */
        swap_bytes(&state->perm[state->index1],
            &state->perm[state->index2]);
        /* Encrypt/decrypt next byte */
        j = state->perm[state->index1] + state->perm[state->index2];
        outbuf[i] = inbuf[i] ^ state->perm[j];
    }
}
 
 
static bool rc4_set_key(RzCrypto *cry, const ut8 *key, int keylen, int mode, int direction) {
    rz_return_val_if_fail(cry->user && key, false);
    struct rc4_state *st = (struct rc4_state *)cry->user;
 
    return rc4_init_state(st, key, keylen);
}
 
static int rc4_get_key_size(RzCrypto *cry) {
    rz_return_val_if_fail(cry->user, 0);
    struct rc4_state *st = (struct rc4_state *)cry->user;
 
    return st->key_size;
}
 
static bool rc4_use(const char *algo) {
    return !strcmp(algo, "rc4");
}
 
static bool update(RzCrypto *cry, const ut8 *buf, int len) {
    rz_return_val_if_fail(cry->user, false);
    struct rc4_state *st = (struct rc4_state *)cry->user;
 
    ut8 *obuf = calloc(1, len);
    if (!obuf) {
        return false;
    }
    rc4_crypt(st, buf, obuf, len);
    rz_crypto_append(cry, obuf, len);
    free(obuf);
    return false;
}
 
static bool final(RzCrypto *cry, const ut8 *buf, int len) {
    return update(cry, buf, len);
}
 
static bool rc4_init(RzCrypto *cry) {
    rz_return_val_if_fail(cry, false);
 
    cry->user = RZ_NEW0(struct rc4_state);
    return cry->user != NULL;
}
 
static bool rc4_fini(RzCrypto *cry) {
    rz_return_val_if_fail(cry, false);
 
    free(cry->user);
    return true;
}
 
RzCryptoPlugin rz_crypto_plugin_rc4 = {
    .name = "rc4",
    .author = "pancake",
    .license = "LGPL-3",
    .set_key = rc4_set_key,
    .get_key_size = rc4_get_key_size,
    .use = rc4_use,
    .update = update,
    .final = final,
    .init = rc4_init,
    .fini = rc4_fini,
};
 
#ifndef RZ_PLUGIN_INCORE
RZ_API RzLibStruct rizin_plugin = {
    .type = RZ_LIB_TYPE_CRYPTO,
    .data = &rz_crypto_plugin_rc4,
    .version = RZ_VERSION
};
#endif