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1Code Examples2=============3 4Code Example For Symmetric Key Cipher Operation5-----------------------------------------------6 7This code encrypts some data with AES-256-XTS. For sake of example,8all inputs are random bytes, the encryption is done in-place, and it's9assumed the code is running in a context where it can sleep.10 11::12 13 static int test_skcipher(void)14 {15 struct crypto_skcipher *tfm = NULL;16 struct skcipher_request *req = NULL;17 u8 *data = NULL;18 const size_t datasize = 512; /* data size in bytes */19 struct scatterlist sg;20 DECLARE_CRYPTO_WAIT(wait);21 u8 iv[16]; /* AES-256-XTS takes a 16-byte IV */22 u8 key[64]; /* AES-256-XTS takes a 64-byte key */23 int err;24 25 /*26 * Allocate a tfm (a transformation object) and set the key.27 *28 * In real-world use, a tfm and key are typically used for many29 * encryption/decryption operations. But in this example, we'll just do a30 * single encryption operation with it (which is not very efficient).31 */32 33 tfm = crypto_alloc_skcipher("xts(aes)", 0, 0);34 if (IS_ERR(tfm)) {35 pr_err("Error allocating xts(aes) handle: %ld\n", PTR_ERR(tfm));36 return PTR_ERR(tfm);37 }38 39 get_random_bytes(key, sizeof(key));40 err = crypto_skcipher_setkey(tfm, key, sizeof(key));41 if (err) {42 pr_err("Error setting key: %d\n", err);43 goto out;44 }45 46 /* Allocate a request object */47 req = skcipher_request_alloc(tfm, GFP_KERNEL);48 if (!req) {49 err = -ENOMEM;50 goto out;51 }52 53 /* Prepare the input data */54 data = kmalloc(datasize, GFP_KERNEL);55 if (!data) {56 err = -ENOMEM;57 goto out;58 }59 get_random_bytes(data, datasize);60 61 /* Initialize the IV */62 get_random_bytes(iv, sizeof(iv));63 64 /*65 * Encrypt the data in-place.66 *67 * For simplicity, in this example we wait for the request to complete68 * before proceeding, even if the underlying implementation is asynchronous.69 *70 * To decrypt instead of encrypt, just change crypto_skcipher_encrypt() to71 * crypto_skcipher_decrypt().72 */73 sg_init_one(&sg, data, datasize);74 skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |75 CRYPTO_TFM_REQ_MAY_SLEEP,76 crypto_req_done, &wait);77 skcipher_request_set_crypt(req, &sg, &sg, datasize, iv);78 err = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);79 if (err) {80 pr_err("Error encrypting data: %d\n", err);81 goto out;82 }83 84 pr_debug("Encryption was successful\n");85 out:86 crypto_free_skcipher(tfm);87 skcipher_request_free(req);88 kfree(data);89 return err;90 }91 92 93Code Example For Use of Operational State Memory With SHASH94-----------------------------------------------------------95 96::97 98 99 struct sdesc {100 struct shash_desc shash;101 char ctx[];102 };103 104 static struct sdesc *init_sdesc(struct crypto_shash *alg)105 {106 struct sdesc *sdesc;107 int size;108 109 size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);110 sdesc = kmalloc(size, GFP_KERNEL);111 if (!sdesc)112 return ERR_PTR(-ENOMEM);113 sdesc->shash.tfm = alg;114 return sdesc;115 }116 117 static int calc_hash(struct crypto_shash *alg,118 const unsigned char *data, unsigned int datalen,119 unsigned char *digest)120 {121 struct sdesc *sdesc;122 int ret;123 124 sdesc = init_sdesc(alg);125 if (IS_ERR(sdesc)) {126 pr_info("can't alloc sdesc\n");127 return PTR_ERR(sdesc);128 }129 130 ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);131 kfree(sdesc);132 return ret;133 }134 135 static int test_hash(const unsigned char *data, unsigned int datalen,136 unsigned char *digest)137 {138 struct crypto_shash *alg;139 char *hash_alg_name = "sha1-padlock-nano";140 int ret;141 142 alg = crypto_alloc_shash(hash_alg_name, 0, 0);143 if (IS_ERR(alg)) {144 pr_info("can't alloc alg %s\n", hash_alg_name);145 return PTR_ERR(alg);146 }147 ret = calc_hash(alg, data, datalen, digest);148 crypto_free_shash(alg);149 return ret;150 }151 152 153Code Example For Random Number Generator Usage154----------------------------------------------155 156::157 158 159 static int get_random_numbers(u8 *buf, unsigned int len)160 {161 struct crypto_rng *rng = NULL;162 char *drbg = "drbg_nopr_sha256"; /* Hash DRBG with SHA-256, no PR */163 int ret;164 165 if (!buf || !len) {166 pr_debug("No output buffer provided\n");167 return -EINVAL;168 }169 170 rng = crypto_alloc_rng(drbg, 0, 0);171 if (IS_ERR(rng)) {172 pr_debug("could not allocate RNG handle for %s\n", drbg);173 return PTR_ERR(rng);174 }175 176 ret = crypto_rng_get_bytes(rng, buf, len);177 if (ret < 0)178 pr_debug("generation of random numbers failed\n");179 else if (ret == 0)180 pr_debug("RNG returned no data");181 else182 pr_debug("RNG returned %d bytes of data\n", ret);183 184 out:185 crypto_free_rng(rng);186 return ret;187 }188