aboutsummaryrefslogtreecommitdiff
path: root/Documentation/crypto/api-samples.rst
blob: d021fd96a76ded1fd3a70c1c3166e7258c5127c9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
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;
    }