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Code Examples
=============
Code Example For Symmetric Key Cipher Operation
-----------------------------------------------
::
struct tcrypt_result {
struct completion completion;
int err;
};
/* tie all data structures together */
struct skcipher_def {
struct scatterlist sg;
struct crypto_skcipher *tfm;
struct skcipher_request *req;
struct tcrypt_result result;
};
/* Callback function */
static void test_skcipher_cb(struct crypto_async_request *req, int error)
{
struct tcrypt_result *result = req->data;
if (error == -EINPROGRESS)
return;
result->err = error;
complete(&result->completion);
pr_info("Encryption finished successfully\n");
}
/* Perform cipher operation */
static unsigned int test_skcipher_encdec(struct skcipher_def *sk,
int enc)
{
int rc = 0;
if (enc)
rc = crypto_skcipher_encrypt(sk->req);
else
rc = crypto_skcipher_decrypt(sk->req);
switch (rc) {
case 0:
break;
case -EINPROGRESS:
case -EBUSY:
rc = wait_for_completion_interruptible(
&sk->result.completion);
if (!rc && !sk->result.err) {
reinit_completion(&sk->result.completion);
break;
}
default:
pr_info("skcipher encrypt returned with %d result %d\n",
rc, sk->result.err);
break;
}
init_completion(&sk->result.completion);
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,
test_skcipher_cb,
&sk.result);
/* 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);
init_completion(&sk.result.completion);
/* 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_shashalg,
const unsigned chardata, unsigned int datalen,
unsigned chardigest) {
struct sdesc sdesc;
int ret;
sdesc = init_sdesc(alg);
if (IS_ERR(sdesc)) {
pr_info("trusted_key: can't alloc %s\n", hash_alg);
return PTR_ERR(sdesc);
}
ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);
kfree(sdesc);
return ret;
}
Code Example For Random Number Generator Usage
----------------------------------------------
::
static int get_random_numbers(u8 *buf, unsigned int len)
{
struct crypto_rngrng = NULL;
chardrbg = "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;
}
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