crypto_serpent.c

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// SPDX-FileCopyrightText: 2017 NicsTr <nicolas.bordes@grenoble-inp.org>
// SPDX-License-Identifier: LGPL-3.0-only
 
#include <rz_lib.h>
#include <rz_crypto.h>
#include "crypto_serpent_algo.h"
 
static bool serpent_set_key(RzCrypto *cry, const ut8 *key, int keylen, int mode, int direction) {
    rz_return_val_if_fail(cry->user && key, false);
    serpent_state_t *st = (serpent_state_t *)cry->user;
 
    if ((keylen != 128 / 8) && (keylen != 192 / 8) && (keylen != 256 / 8)) {
        return false;
    }
    st->key_size = keylen * 8;
    for (size_t i = 0; i < keylen / 4; i++) {
        st->key[i] = rz_read_at_le32(key, i * 4);
    }
    cry->dir = direction;
    return true;
}
 
static int serpent_get_key_size(RzCrypto *cry) {
    rz_return_val_if_fail(cry->user, 0);
    serpent_state_t *st = (serpent_state_t *)cry->user;
 
    return st->key_size;
}
 
static bool serpent_use(const char *algo) {
    return !strcmp(algo, "serpent-ecb");
}
 
#define BLOCK_SIZE 16
 
static bool update(RzCrypto *cry, const ut8 *buf, int len) {
    rz_return_val_if_fail(cry->user, 0);
    serpent_state_t *st = (serpent_state_t *)cry->user;
    if (len < 1) {
        return false;
    }
 
    // Pad to the block size, do not append dummy block
    const int diff = (BLOCK_SIZE - (len % BLOCK_SIZE)) % BLOCK_SIZE;
    const int size = len + diff;
    const int blocks = size / BLOCK_SIZE;
    int i, j;
 
    ut8 *const obuf = calloc(4, size / 4);
    if (!obuf) {
        return false;
    }
    ut32 *const ibuf = calloc(4, size / 4);
    if (!ibuf) {
        free(obuf);
        return false;
    }
    ut32 *const tmp = calloc(4, size / 4);
    if (!tmp) {
        free(obuf);
        free(ibuf);
        return false;
    }
 
    // Construct ut32 blocks from byte stream
    for (j = 0; j < len / 4; j++) {
        ibuf[j] = rz_read_le32(buf + 4 * j);
    }
    if (len & 0x3) {
        ut8 tail[4] = { 0 }; // Zero padding
        memcpy(tail, buf + (len & ~0x3), len & 0x3);
        ibuf[len / 4] = rz_read_le32(tail);
    }
 
    if (cry->dir == RZ_CRYPTO_DIR_ENCRYPT) {
        for (i = 0; i < blocks; i++) {
            // delta in number of ut32
            const int delta = (BLOCK_SIZE * i) / 4;
            serpent_encrypt(st, ibuf + delta, tmp + delta);
        }
    } else {
        for (i = 0; i < blocks; i++) {
            // delta in number of ut32
            const int delta = (BLOCK_SIZE * i) / 4;
            serpent_decrypt(st, ibuf + delta, tmp + delta);
        }
    }
 
    // Construct ut32 blocks from byte stream
    int k;
    for (j = 0; j < size / 4; j++) {
        k = 4 * j;
        obuf[k] = tmp[j] & 0xff;
        obuf[k + 1] = (tmp[j] >> 8) & 0xff;
        obuf[k + 2] = (tmp[j] >> 16) & 0xff;
        obuf[k + 3] = (tmp[j] >> 24) & 0xff;
    }
 
    rz_crypto_append(cry, obuf, size);
    free(obuf);
    free(ibuf);
    free(tmp);
    return true;
}
 
static bool final(RzCrypto *cry, const ut8 *buf, int len) {
    return update(cry, buf, len);
}
 
static bool serpent_init(RzCrypto *cry) {
    rz_return_val_if_fail(cry, false);
 
    cry->user = RZ_NEW0(serpent_state_t);
    return cry->user != NULL;
}
 
static bool serpent_fini(RzCrypto *cry) {
    rz_return_val_if_fail(cry, false);
 
    free(cry->user);
    return true;
}
 
RzCryptoPlugin rz_crypto_plugin_serpent = {
    .name = "serpent-ecb",
    .author = "NicsTr",
    .license = "LGPL-3",
    .set_key = serpent_set_key,
    .get_key_size = serpent_get_key_size,
    .use = serpent_use,
    .update = update,
    .final = final,
    .init = serpent_init,
    .fini = serpent_fini,
};
 
#ifndef RZ_PLUGIN_INCORE
RZ_API RzLibStruct rizin_plugin = {
    .type = RZ_LIB_TYPE_CRYPTO,
    .data = &rz_crypto_plugin_serpent,
    .version = RZ_VERSION
};
#endif