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2024-05-10 10ebd8556b7990499c896a550e3d416b444211e6

 kernel/Documentation/crypto/api-samples.rst
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@@ -4,111 +4,89 @@
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4
 Code Example For Symmetric Key Cipher Operation
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5
 -----------------------------------------------
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6
 
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+This code encrypts some data with AES-256-XTS.  For sake of example,
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+all inputs are random bytes, the encryption is done in-place, and it's
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+assumed the code is running in a context where it can sleep.
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+
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11
 ::
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12
 
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-
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-    /* tie all data structures together */
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-    struct skcipher_def {
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-        struct scatterlist sg;
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-        struct crypto_skcipher *tfm;
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-        struct skcipher_request *req;
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-        struct crypto_wait wait;
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-    };
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-
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-    /* Perform cipher operation */
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-    static unsigned int test_skcipher_encdec(struct skcipher_def *sk,
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-                         int enc)
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-    {
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-        int rc;
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-
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-        if (enc)
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-            rc = crypto_wait_req(crypto_skcipher_encrypt(sk->req), &sk->wait);
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-        else
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-            rc = crypto_wait_req(crypto_skcipher_decrypt(sk->req), &sk->wait);
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-
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-	if (rc)
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-		pr_info("skcipher encrypt returned with result %d\n", rc);
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-
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-        return rc;
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-    }
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-
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-    /* Initialize and trigger cipher operation */
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13
     static int test_skcipher(void)
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14
     {
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-        struct skcipher_def sk;
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-        struct crypto_skcipher *skcipher = NULL;
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-        struct skcipher_request *req = NULL;
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-        char *scratchpad = NULL;
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-        char *ivdata = NULL;
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-        unsigned char key[32];
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-        int ret = -EFAULT;
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+            struct crypto_skcipher *tfm = NULL;
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+            struct skcipher_request *req = NULL;
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+            u8 *data = NULL;
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+            const size_t datasize = 512; /* data size in bytes */
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+            struct scatterlist sg;
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+            DECLARE_CRYPTO_WAIT(wait);
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+            u8 iv[16];  /* AES-256-XTS takes a 16-byte IV */
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+            u8 key[64]; /* AES-256-XTS takes a 64-byte key */
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+            int err;
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24
 
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-        skcipher = crypto_alloc_skcipher("cbc-aes-aesni", 0, 0);
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-        if (IS_ERR(skcipher)) {
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-            pr_info("could not allocate skcipher handle\n");
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-            return PTR_ERR(skcipher);
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-        }
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+            /*
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+             * Allocate a tfm (a transformation object) and set the key.
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+             *
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+             * In real-world use, a tfm and key are typically used for many
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+             * encryption/decryption operations.  But in this example, we'll just do a
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+             * single encryption operation with it (which is not very efficient).
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+             */
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32
 
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-        req = skcipher_request_alloc(skcipher, GFP_KERNEL);
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-        if (!req) {
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-            pr_info("could not allocate skcipher request\n");
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-            ret = -ENOMEM;
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-            goto out;
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-        }
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+            tfm = crypto_alloc_skcipher("xts(aes)", 0, 0);
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+            if (IS_ERR(tfm)) {
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+                    pr_err("Error allocating xts(aes) handle: %ld\n", PTR_ERR(tfm));
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+                    return PTR_ERR(tfm);
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+            }
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38
 
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-        skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
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-                          crypto_req_done,
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-                          &sk.wait);
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+            get_random_bytes(key, sizeof(key));
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+            err = crypto_skcipher_setkey(tfm, key, sizeof(key));
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+            if (err) {
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+                    pr_err("Error setting key: %d\n", err);
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+                    goto out;
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+            }
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45
 
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-        /* AES 256 with random key */
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-        get_random_bytes(&key, 32);
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-        if (crypto_skcipher_setkey(skcipher, key, 32)) {
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-            pr_info("key could not be set\n");
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-            ret = -EAGAIN;
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-            goto out;
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-        }
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+            /* Allocate a request object */
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+            req = skcipher_request_alloc(tfm, GFP_KERNEL);
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+            if (!req) {
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+                    err = -ENOMEM;
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+                    goto out;
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+            }
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52
 
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-        /* IV will be random */
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-        ivdata = kmalloc(16, GFP_KERNEL);
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-        if (!ivdata) {
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-            pr_info("could not allocate ivdata\n");
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-            goto out;
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-        }
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-        get_random_bytes(ivdata, 16);
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+            /* Prepare the input data */
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+            data = kmalloc(datasize, GFP_KERNEL);
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+            if (!data) {
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+                    err = -ENOMEM;
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+                    goto out;
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+            }
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+            get_random_bytes(data, datasize);
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60
 
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-        /* Input data will be random */
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-        scratchpad = kmalloc(16, GFP_KERNEL);
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-        if (!scratchpad) {
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-            pr_info("could not allocate scratchpad\n");
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-            goto out;
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-        }
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-        get_random_bytes(scratchpad, 16);
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+            /* Initialize the IV */
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+            get_random_bytes(iv, sizeof(iv));
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63
 
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-        sk.tfm = skcipher;
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-        sk.req = req;
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+            /*
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+             * Encrypt the data in-place.
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+             *
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+             * For simplicity, in this example we wait for the request to complete
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+             * before proceeding, even if the underlying implementation is asynchronous.
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+             *
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+             * To decrypt instead of encrypt, just change crypto_skcipher_encrypt() to
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+             * crypto_skcipher_decrypt().
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+             */
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+            sg_init_one(&sg, data, datasize);
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+            skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
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+                                               CRYPTO_TFM_REQ_MAY_SLEEP,
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+                                          crypto_req_done, &wait);
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+            skcipher_request_set_crypt(req, &sg, &sg, datasize, iv);
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+            err = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
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+            if (err) {
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+                    pr_err("Error encrypting data: %d\n", err);
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+                    goto out;
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+            }
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83
 
90
-        /* We encrypt one block */
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-        sg_init_one(&sk.sg, scratchpad, 16);
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-        skcipher_request_set_crypt(req, &sk.sg, &sk.sg, 16, ivdata);
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-        crypto_init_wait(&sk.wait);
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-
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-        /* encrypt data */
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-        ret = test_skcipher_encdec(&sk, 1);
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-        if (ret)
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-            goto out;
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-
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-        pr_info("Encryption triggered successfully\n");
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-
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+            pr_debug("Encryption was successful\n");
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85
     out:
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-        if (skcipher)
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-            crypto_free_skcipher(skcipher);
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-        if (req)
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+            crypto_free_skcipher(tfm);
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87
             skcipher_request_free(req);
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-        if (ivdata)
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-            kfree(ivdata);
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-        if (scratchpad)
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-            kfree(scratchpad);
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-        return ret;
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+            kfree(data);
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+            return err;
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90
     }
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91
 
114
92
 
..
..
@@ -133,7 +111,6 @@
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111
         if (!sdesc)
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112
             return ERR_PTR(-ENOMEM);
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113
         sdesc->shash.tfm = alg;
136
-        sdesc->shash.flags = 0x0;
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114
         return sdesc;
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115
     }
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116