crypto: doc - convert crypto API documentation to Sphinx

With the conversion of the kernel crypto API DocBook to Sphinx, the
monolithic document is broken up into individual documents. The
documentation is unchanged with the exception of a slight reordering to
keep the individual document parts self-contained.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

1 files changed, 224 insertions, 0 deletions

diff --git a/Documentation/crypto/api-samples.rst b/Documentation/crypto/api-samples.rst
new file mode 100644
index 000000000000..0a10819f6107
--- /dev/null
+++ b/Documentation/crypto/api-samples.rst
@@ -0,0 +1,224 @@
+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 sdescinit_sdesc(struct crypto_shash *alg)
+    {
+        struct sdescsdesc;
+        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 sdescsdesc;
+        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;
+    }