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Code Example For Symmetric Key Cipher Operation

/* tie all data structures together */
struct skcipher_def {
    struct scatterlist sg;
    struct crypto_skcipher *tfm;
    struct skcipher_request *req;
    struct crypto_wait wait;
};

/* Perform cipher operation */
static unsigned int test_skcipher_encdec(struct skcipher_def *sk,
                     int enc)
{
    int rc;

    if (enc)
        rc = crypto_wait_req(crypto_skcipher_encrypt(sk->req), &sk->wait);
    else
        rc = crypto_wait_req(crypto_skcipher_decrypt(sk->req), &sk->wait);

    if (rc)
            pr_info("skcipher encrypt returned with result %d\n", rc);

    return rc;
}

/* Initialize and trigger cipher operation */
static int test_skcipher(void)
{
    struct skcipher_def sk;
    struct crypto_skcipher *skcipher = NULL;
    struct skcipher_request *req = NULL;
    char *scratchpad = NULL;
    char *ivdata = NULL;
    unsigned char key[32];
    int ret = -EFAULT;

    skcipher = crypto_alloc_skcipher("cbc-aes-aesni", 0, 0);
    if (IS_ERR(skcipher)) {
        pr_info("could not allocate skcipher handle\n");
        return PTR_ERR(skcipher);
    }

    req = skcipher_request_alloc(skcipher, GFP_KERNEL);
    if (!req) {
        pr_info("could not allocate skcipher request\n");
        ret = -ENOMEM;
        goto out;
    }

    skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
                      crypto_req_done,
                      &sk.wait);

    /* AES 256 with random key */
    get_random_bytes(&key, 32);
    if (crypto_skcipher_setkey(skcipher, key, 32)) {
        pr_info("key could not be set\n");
        ret = -EAGAIN;
        goto out;
    }

    /* IV will be random */
    ivdata = kmalloc(16, GFP_KERNEL);
    if (!ivdata) {
        pr_info("could not allocate ivdata\n");
        goto out;
    }
    get_random_bytes(ivdata, 16);

    /* Input data will be random */
    scratchpad = kmalloc(16, GFP_KERNEL);
    if (!scratchpad) {
        pr_info("could not allocate scratchpad\n");
        goto out;
    }
    get_random_bytes(scratchpad, 16);

    sk.tfm = skcipher;
    sk.req = req;

    /* We encrypt one block */
    sg_init_one(&sk.sg, scratchpad, 16);
    skcipher_request_set_crypt(req, &sk.sg, &sk.sg, 16, ivdata);
    crypto_init_wait(&sk.wait);

    /* encrypt data */
    ret = test_skcipher_encdec(&sk, 1);
    if (ret)
        goto out;

    pr_info("Encryption triggered successfully\n");

out:
    if (skcipher)
        crypto_free_skcipher(skcipher);
    if (req)
        skcipher_request_free(req);
    if (ivdata)
        kfree(ivdata);
    if (scratchpad)
        kfree(scratchpad);
    return ret;
}

Code Example For Use of Operational State Memory With SHASH

struct sdesc {
    struct shash_desc shash;
    char ctx[];
};

static struct sdesc *init_sdesc(struct crypto_shash *alg)
{
    struct sdesc *sdesc;
    int size;

    size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
    sdesc = kmalloc(size, GFP_KERNEL);
    if (!sdesc)
        return ERR_PTR(-ENOMEM);
    sdesc->shash.tfm = alg;
    sdesc->shash.flags = 0x0;
    return sdesc;
}

static int calc_hash(struct crypto_shash *alg,
             const unsigned char *data, unsigned int datalen,
             unsigned char *digest)
{
    struct sdesc *sdesc;
    int ret;

    sdesc = init_sdesc(alg);
    if (IS_ERR(sdesc)) {
        pr_info("can't alloc sdesc\n");
        return PTR_ERR(sdesc);
    }

    ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);
    kfree(sdesc);
    return ret;
}

static int test_hash(const unsigned char *data, unsigned int datalen,
             unsigned char *digest)
{
    struct crypto_shash *alg;
    char *hash_alg_name = "sha1-padlock-nano";
    int ret;

    alg = crypto_alloc_shash(hash_alg_name, 0, 0);
    if (IS_ERR(alg)) {
            pr_info("can't alloc alg %s\n", hash_alg_name);
            return PTR_ERR(alg);
    }
    ret = calc_hash(alg, data, datalen, digest);
    crypto_free_shash(alg);
    return ret;
}

Code Example For Random Number Generator Usage

static int get_random_numbers(u8 *buf, unsigned int len)
{
    struct crypto_rng *rng = NULL;
    char *drbg = "drbg_nopr_sha256"; /* Hash DRBG with SHA-256, no PR */
    int ret;

    if (!buf || !len) {
        pr_debug("No output buffer provided\n");
        return -EINVAL;
    }

    rng = crypto_alloc_rng(drbg, 0, 0);
    if (IS_ERR(rng)) {
        pr_debug("could not allocate RNG handle for %s\n", drbg);
        return PTR_ERR(rng);
    }

    ret = crypto_rng_get_bytes(rng, buf, len);
    if (ret < 0)
        pr_debug("generation of random numbers failed\n");
    else if (ret == 0)
        pr_debug("RNG returned no data");
    else
        pr_debug("RNG returned %d bytes of data\n", ret);

out:
    crypto_free_rng(rng);
    return ret;
}