Documentation/crypto/api-samples.rst

   1 Code Examples
   2 =============
   3
   4 Code Example For Symmetric Key Cipher Operation
   5 -----------------------------------------------
   6
   7 ::
   8
   9
  10     /* tie all data structures together */
  11     struct skcipher_def {
  12         struct scatterlist sg;
  13         struct crypto_skcipher *tfm;
  14         struct skcipher_request *req;
  15         struct crypto_wait wait;
  16     };
  17
  18     /* Perform cipher operation */
  19     static unsigned int test_skcipher_encdec(struct skcipher_def *sk,
  20                          int enc)
  21     {
  22         int rc;
  23
  24         if (enc)
  25             rc = crypto_wait_req(crypto_skcipher_encrypt(sk->req), &sk->wait);
  26         else
  27             rc = crypto_wait_req(crypto_skcipher_decrypt(sk->req), &sk->wait);
  28
  29         if (rc)
  30                 pr_info("skcipher encrypt returned with result %d\n", rc);
  31
  32         return rc;
  33     }
  34
  35     /* Initialize and trigger cipher operation */
  36     static int test_skcipher(void)
  37     {
  38         struct skcipher_def sk;
  39         struct crypto_skcipher *skcipher = NULL;
  40         struct skcipher_request *req = NULL;
  41         char *scratchpad = NULL;
  42         char *ivdata = NULL;
  43         unsigned char key[32];
  44         int ret = -EFAULT;
  45
  46         skcipher = crypto_alloc_skcipher("cbc-aes-aesni", 0, 0);
  47         if (IS_ERR(skcipher)) {
  48             pr_info("could not allocate skcipher handle\n");
  49             return PTR_ERR(skcipher);
  50         }
  51
  52         req = skcipher_request_alloc(skcipher, GFP_KERNEL);
  53         if (!req) {
  54             pr_info("could not allocate skcipher request\n");
  55             ret = -ENOMEM;
  56             goto out;
  57         }
  58
  59         skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
  60                           crypto_req_done,
  61                           &sk.wait);
  62
  63         /* AES 256 with random key */
  64         get_random_bytes(&key, 32);
  65         if (crypto_skcipher_setkey(skcipher, key, 32)) {
  66             pr_info("key could not be set\n");
  67             ret = -EAGAIN;
  68             goto out;
  69         }
  70
  71         /* IV will be random */
  72         ivdata = kmalloc(16, GFP_KERNEL);
  73         if (!ivdata) {
  74             pr_info("could not allocate ivdata\n");
  75             goto out;
  76         }
  77         get_random_bytes(ivdata, 16);
  78
  79         /* Input data will be random */
  80         scratchpad = kmalloc(16, GFP_KERNEL);
  81         if (!scratchpad) {
  82             pr_info("could not allocate scratchpad\n");
  83             goto out;
  84         }
  85         get_random_bytes(scratchpad, 16);
  86
  87         sk.tfm = skcipher;
  88         sk.req = req;
  89
  90         /* We encrypt one block */
  91         sg_init_one(&sk.sg, scratchpad, 16);
  92         skcipher_request_set_crypt(req, &sk.sg, &sk.sg, 16, ivdata);
  93         crypto_init_wait(&sk.wait);
  94
  95         /* encrypt data */
  96         ret = test_skcipher_encdec(&sk, 1);
  97         if (ret)
  98             goto out;
  99
 100         pr_info("Encryption triggered successfully\n");
 101
 102     out:
 103         if (skcipher)
 104             crypto_free_skcipher(skcipher);
 105         if (req)
 106             skcipher_request_free(req);
 107         if (ivdata)
 108             kfree(ivdata);
 109         if (scratchpad)
 110             kfree(scratchpad);
 111         return ret;
 112     }
 113
 114
 115 Code Example For Use of Operational State Memory With SHASH
 116 -----------------------------------------------------------
 117
 118 ::
 119
 120
 121     struct sdesc {
 122         struct shash_desc shash;
 123         char ctx[];
 124     };
 125
 126     static struct sdesc *init_sdesc(struct crypto_shash *alg)
 127     {
 128         struct sdesc *sdesc;
 129         int size;
 130
 131         size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
 132         sdesc = kmalloc(size, GFP_KERNEL);
 133         if (!sdesc)
 134             return ERR_PTR(-ENOMEM);
 135         sdesc->shash.tfm = alg;
 136         return sdesc;
 137     }
 138
 139     static int calc_hash(struct crypto_shash *alg,
 140                  const unsigned char *data, unsigned int datalen,
 141                  unsigned char *digest)
 142     {
 143         struct sdesc *sdesc;
 144         int ret;
 145
 146         sdesc = init_sdesc(alg);
 147         if (IS_ERR(sdesc)) {
 148             pr_info("can't alloc sdesc\n");
 149             return PTR_ERR(sdesc);
 150         }
 151
 152         ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);
 153         kfree(sdesc);
 154         return ret;
 155     }
 156
 157     static int test_hash(const unsigned char *data, unsigned int datalen,
 158                  unsigned char *digest)
 159     {
 160         struct crypto_shash *alg;
 161         char *hash_alg_name = "sha1-padlock-nano";
 162         int ret;
 163
 164         alg = crypto_alloc_shash(hash_alg_name, 0, 0);
 165         if (IS_ERR(alg)) {
 166                 pr_info("can't alloc alg %s\n", hash_alg_name);
 167                 return PTR_ERR(alg);
 168         }
 169         ret = calc_hash(alg, data, datalen, digest);
 170         crypto_free_shash(alg);
 171         return ret;
 172     }
 173
 174
 175 Code Example For Random Number Generator Usage
 176 ----------------------------------------------
 177
 178 ::
 179
 180
 181     static int get_random_numbers(u8 *buf, unsigned int len)
 182     {
 183         struct crypto_rng *rng = NULL;
 184         char *drbg = "drbg_nopr_sha256"; /* Hash DRBG with SHA-256, no PR */
 185         int ret;
 186
 187         if (!buf || !len) {
 188             pr_debug("No output buffer provided\n");
 189             return -EINVAL;
 190         }
 191
 192         rng = crypto_alloc_rng(drbg, 0, 0);
 193         if (IS_ERR(rng)) {
 194             pr_debug("could not allocate RNG handle for %s\n", drbg);
 195             return PTR_ERR(rng);
 196         }
 197
 198         ret = crypto_rng_get_bytes(rng, buf, len);
 199         if (ret < 0)
 200             pr_debug("generation of random numbers failed\n");
 201         else if (ret == 0)
 202             pr_debug("RNG returned no data");
 203         else
 204             pr_debug("RNG returned %d bytes of data\n", ret);
 205
 206     out:
 207         crypto_free_rng(rng);
 208         return ret;
 209     }