1Code Examples
2=============
3
4Code Example For Symmetric Key Cipher Operation
5-----------------------------------------------
6
7::
8
9
10    struct tcrypt_result {
11        struct completion completion;
12        int err;
13    };
14
15    /* tie all data structures together */
16    struct skcipher_def {
17        struct scatterlist sg;
18        struct crypto_skcipher *tfm;
19        struct skcipher_request *req;
20        struct tcrypt_result result;
21    };
22
23    /* Callback function */
24    static void test_skcipher_cb(struct crypto_async_request *req, int error)
25    {
26        struct tcrypt_result *result = req->data;
27
28        if (error == -EINPROGRESS)
29            return;
30        result->err = error;
31        complete(&result->completion);
32        pr_info("Encryption finished successfully\n");
33    }
34
35    /* Perform cipher operation */
36    static unsigned int test_skcipher_encdec(struct skcipher_def *sk,
37                         int enc)
38    {
39        int rc = 0;
40
41        if (enc)
42            rc = crypto_skcipher_encrypt(sk->req);
43        else
44            rc = crypto_skcipher_decrypt(sk->req);
45
46        switch (rc) {
47        case 0:
48            break;
49        case -EINPROGRESS:
50        case -EBUSY:
51            rc = wait_for_completion_interruptible(
52                &sk->result.completion);
53            if (!rc && !sk->result.err) {
54                reinit_completion(&sk->result.completion);
55                break;
56            }
57        default:
58            pr_info("skcipher encrypt returned with %d result %d\n",
59                rc, sk->result.err);
60            break;
61        }
62        init_completion(&sk->result.completion);
63
64        return rc;
65    }
66
67    /* Initialize and trigger cipher operation */
68    static int test_skcipher(void)
69    {
70        struct skcipher_def sk;
71        struct crypto_skcipher *skcipher = NULL;
72        struct skcipher_request *req = NULL;
73        char *scratchpad = NULL;
74        char *ivdata = NULL;
75        unsigned char key[32];
76        int ret = -EFAULT;
77
78        skcipher = crypto_alloc_skcipher("cbc-aes-aesni", 0, 0);
79        if (IS_ERR(skcipher)) {
80            pr_info("could not allocate skcipher handle\n");
81            return PTR_ERR(skcipher);
82        }
83
84        req = skcipher_request_alloc(skcipher, GFP_KERNEL);
85        if (!req) {
86            pr_info("could not allocate skcipher request\n");
87            ret = -ENOMEM;
88            goto out;
89        }
90
91        skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
92                          test_skcipher_cb,
93                          &sk.result);
94
95        /* AES 256 with random key */
96        get_random_bytes(&key, 32);
97        if (crypto_skcipher_setkey(skcipher, key, 32)) {
98            pr_info("key could not be set\n");
99            ret = -EAGAIN;
100            goto out;
101        }
102
103        /* IV will be random */
104        ivdata = kmalloc(16, GFP_KERNEL);
105        if (!ivdata) {
106            pr_info("could not allocate ivdata\n");
107            goto out;
108        }
109        get_random_bytes(ivdata, 16);
110
111        /* Input data will be random */
112        scratchpad = kmalloc(16, GFP_KERNEL);
113        if (!scratchpad) {
114            pr_info("could not allocate scratchpad\n");
115            goto out;
116        }
117        get_random_bytes(scratchpad, 16);
118
119        sk.tfm = skcipher;
120        sk.req = req;
121
122        /* We encrypt one block */
123        sg_init_one(&sk.sg, scratchpad, 16);
124        skcipher_request_set_crypt(req, &sk.sg, &sk.sg, 16, ivdata);
125        init_completion(&sk.result.completion);
126
127        /* encrypt data */
128        ret = test_skcipher_encdec(&sk, 1);
129        if (ret)
130            goto out;
131
132        pr_info("Encryption triggered successfully\n");
133
134    out:
135        if (skcipher)
136            crypto_free_skcipher(skcipher);
137        if (req)
138            skcipher_request_free(req);
139        if (ivdata)
140            kfree(ivdata);
141        if (scratchpad)
142            kfree(scratchpad);
143        return ret;
144    }
145
146
147Code Example For Use of Operational State Memory With SHASH
148-----------------------------------------------------------
149
150::
151
152
153    struct sdesc {
154        struct shash_desc shash;
155        char ctx[];
156    };
157
158    static struct sdescinit_sdesc(struct crypto_shash *alg)
159    {
160        struct sdescsdesc;
161        int size;
162
163        size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
164        sdesc = kmalloc(size, GFP_KERNEL);
165        if (!sdesc)
166            return ERR_PTR(-ENOMEM);
167        sdesc->shash.tfm = alg;
168        sdesc->shash.flags = 0x0;
169        return sdesc;
170    }
171
172    static int calc_hash(struct crypto_shashalg,
173                 const unsigned chardata, unsigned int datalen,
174                 unsigned chardigest) {
175        struct sdescsdesc;
176        int ret;
177
178        sdesc = init_sdesc(alg);
179        if (IS_ERR(sdesc)) {
180            pr_info("trusted_key: can't alloc %s\n", hash_alg);
181            return PTR_ERR(sdesc);
182        }
183
184        ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);
185        kfree(sdesc);
186        return ret;
187    }
188
189
190Code Example For Random Number Generator Usage
191----------------------------------------------
192
193::
194
195
196    static int get_random_numbers(u8 *buf, unsigned int len)
197    {
198        struct crypto_rngrng = NULL;
199        chardrbg = "drbg_nopr_sha256"; /* Hash DRBG with SHA-256, no PR */
200        int ret;
201
202        if (!buf || !len) {
203            pr_debug("No output buffer provided\n");
204            return -EINVAL;
205        }
206
207        rng = crypto_alloc_rng(drbg, 0, 0);
208        if (IS_ERR(rng)) {
209            pr_debug("could not allocate RNG handle for %s\n", drbg);
210            return -PTR_ERR(rng);
211        }
212
213        ret = crypto_rng_get_bytes(rng, buf, len);
214        if (ret < 0)
215            pr_debug("generation of random numbers failed\n");
216        else if (ret == 0)
217            pr_debug("RNG returned no data");
218        else
219            pr_debug("RNG returned %d bytes of data\n", ret);
220
221    out:
222        crypto_free_rng(rng);
223        return ret;
224    }
225