crypto: doc - hash data structures

The hash data structures needed to be filled in by cipher developers are
documented.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index 74b13ec1ebd449caf644fde19ed17921af9e4649..bf458fc272aaf1e44e031c4f2b634770ec6af332 100644 (file)
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -17,6 +17,28 @@
 
 struct crypto_ahash;
 
+/**
+ * DOC: Message Digest Algorithm Definitions
+ *
+ * These data structures define modular message digest algorithm
+ * implementations, managed via crypto_register_ahash(),
+ * crypto_register_shash(), crypto_unregister_ahash() and
+ * crypto_unregister_shash().
+ */
+
+/**
+ * struct hash_alg_common - define properties of message digest
+ * @digestsize: Size of the result of the transformation. A buffer of this size
+ *             must be available to the @final and @finup calls, so they can
+ *             store the resulting hash into it. For various predefined sizes,
+ *             search include/crypto/ using
+ *             git grep _DIGEST_SIZE include/crypto.
+ * @statesize: Size of the block for partial state of the transformation. A
+ *            buffer of this size must be passed to the @export function as it
+ *            will save the partial state of the transformation into it. On the
+ *            other side, the @import function will load the state from a
+ *            buffer of this size as well.
+ */
 struct hash_alg_common {
        unsigned int digestsize;
        unsigned int statesize;
@@ -37,6 +59,62 @@ struct ahash_request {
        void *__ctx[] CRYPTO_MINALIGN_ATTR;
 };
 
+/**
+ * struct ahash_alg - asynchronous message digest definition
+ * @init: Initialize the transformation context. Intended only to initialize the
+ *       state of the HASH transformation at the begining. This shall fill in
+ *       the internal structures used during the entire duration of the whole
+ *       transformation. No data processing happens at this point.
+ * @update: Push a chunk of data into the driver for transformation. This
+ *        function actually pushes blocks of data from upper layers into the
+ *        driver, which then passes those to the hardware as seen fit. This
+ *        function must not finalize the HASH transformation by calculating the
+ *        final message digest as this only adds more data into the
+ *        transformation. This function shall not modify the transformation
+ *        context, as this function may be called in parallel with the same
+ *        transformation object. Data processing can happen synchronously
+ *        [SHASH] or asynchronously [AHASH] at this point.
+ * @final: Retrieve result from the driver. This function finalizes the
+ *        transformation and retrieves the resulting hash from the driver and
+ *        pushes it back to upper layers. No data processing happens at this
+ *        point.
+ * @finup: Combination of @update and @final. This function is effectively a
+ *        combination of @update and @final calls issued in sequence. As some
+ *        hardware cannot do @update and @final separately, this callback was
+ *        added to allow such hardware to be used at least by IPsec. Data
+ *        processing can happen synchronously [SHASH] or asynchronously [AHASH]
+ *        at this point.
+ * @digest: Combination of @init and @update and @final. This function
+ *         effectively behaves as the entire chain of operations, @init,
+ *         @update and @final issued in sequence. Just like @finup, this was
+ *         added for hardware which cannot do even the @finup, but can only do
+ *         the whole transformation in one run. Data processing can happen
+ *         synchronously [SHASH] or asynchronously [AHASH] at this point.
+ * @setkey: Set optional key used by the hashing algorithm. Intended to push
+ *         optional key used by the hashing algorithm from upper layers into
+ *         the driver. This function can store the key in the transformation
+ *         context or can outright program it into the hardware. In the former
+ *         case, one must be careful to program the key into the hardware at
+ *         appropriate time and one must be careful that .setkey() can be
+ *         called multiple times during the existence of the transformation
+ *         object. Not  all hashing algorithms do implement this function as it
+ *         is only needed for keyed message digests. SHAx/MDx/CRCx do NOT
+ *         implement this function. HMAC(MDx)/HMAC(SHAx)/CMAC(AES) do implement
+ *         this function. This function must be called before any other of the
+ *         @init, @update, @final, @finup, @digest is called. No data
+ *         processing happens at this point.
+ * @export: Export partial state of the transformation. This function dumps the
+ *         entire state of the ongoing transformation into a provided block of
+ *         data so it can be @import 'ed back later on. This is useful in case
+ *         you want to save partial result of the transformation after
+ *         processing certain amount of data and reload this partial result
+ *         multiple times later on for multiple re-use. No data processing
+ *         happens at this point.
+ * @import: Import partial state of the transformation. This function loads the
+ *         entire state of the ongoing transformation from a provided block of
+ *         data so the transformation can continue from this point onward. No
+ *         data processing happens at this point.
+ */
 struct ahash_alg {
        int (*init)(struct ahash_request *req);
        int (*update)(struct ahash_request *req);
@@ -63,6 +141,23 @@ struct shash_desc {
                crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \
        struct shash_desc *shash = (struct shash_desc *)__##shash##_desc
 
+/**
+ * struct shash_alg - synchronous message digest definition
+ * @init: see struct ahash_alg
+ * @update: see struct ahash_alg
+ * @final: see struct ahash_alg
+ * @finup: see struct ahash_alg
+ * @digest: see struct ahash_alg
+ * @export: see struct ahash_alg
+ * @import: see struct ahash_alg
+ * @setkey: see struct ahash_alg
+ * @digestsize: see struct ahash_alg
+ * @statesize: see struct ahash_alg
+ * @dedcsize: Size of the operational state for the message digest. This state
+ *           size is the memory size that needs to be allocated for
+ *           shash_desc.__ctx
+ * @base: internally used
+ */
 struct shash_alg {
        int (*init)(struct shash_desc *desc);
        int (*update)(struct shash_desc *desc, const u8 *data,