crypto: hash - Add import/export interface

It is often useful to save the partial state of a hash function
so that it can be used as a base for two or more computations.

The most prominent example is HMAC where all hashes start from
a base determined by the key.  Having an import/export interface
means that we only have to compute that base once rather than
for each message.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 22 insertions, 5 deletions

diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index f9b51d408953..cd16d6e668ce 100644
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -24,6 +24,7 @@ struct shash_desc {
 
 struct shash_alg {
         int (*init)(struct shash_desc *desc);
+        int (*reinit)(struct shash_desc *desc);
         int (*update)(struct shash_desc *desc, const u8 *data,
                       unsigned int len);
         int (*final)(struct shash_desc *desc, u8 *out);
@@ -116,6 +117,11 @@ static inline unsigned int crypto_ahash_reqsize(struct crypto_ahash *tfm)
         return crypto_ahash_crt(tfm)->reqsize;
 }
 
+static inline void *ahash_request_ctx(struct ahash_request *req)
+{
+        return req->__ctx;
+}
+
 static inline int crypto_ahash_setkey(struct crypto_ahash *tfm,
                                       const u8 *key, unsigned int keylen)
 {
@@ -130,6 +136,14 @@ static inline int crypto_ahash_digest(struct ahash_request *req)
         return crt->digest(req);
 }
 
+static inline void crypto_ahash_export(struct ahash_request *req, u8 *out)
+{
+        memcpy(out, ahash_request_ctx(req),
+               crypto_ahash_reqsize(crypto_ahash_reqtfm(req)));
+}
+
+int crypto_ahash_import(struct ahash_request *req, const u8 *in);
+
 static inline int crypto_ahash_init(struct ahash_request *req)
 {
         struct ahash_tfm *crt = crypto_ahash_crt(crypto_ahash_reqtfm(req));
@@ -262,6 +276,13 @@ int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
 int crypto_shash_digest(struct shash_desc *desc, const u8 *data,
                         unsigned int len, u8 *out);
 
+static inline void crypto_shash_export(struct shash_desc *desc, u8 *out)
+{
+        memcpy(out, shash_desc_ctx(desc), crypto_shash_descsize(desc->tfm));
+}
+
+int crypto_shash_import(struct shash_desc *desc, const u8 *in);
+
 static inline int crypto_shash_init(struct shash_desc *desc)
 {
         return crypto_shash_alg(desc->tfm)->init(desc);
diff --git a/include/crypto/internal/hash.h b/include/crypto/internal/hash.h
index 32d3a8ed06de..92fbe7385856 100644
--- a/include/crypto/internal/hash.h
+++ b/include/crypto/internal/hash.h
@@ -66,11 +66,6 @@ static inline struct ahash_request *ahash_dequeue_request(
         return ahash_request_cast(crypto_dequeue_request(queue));
 }
 
-static inline void *ahash_request_ctx(struct ahash_request *req)
-{
-        return req->__ctx;
-}
-
 static inline int ahash_tfm_in_queue(struct crypto_queue *queue,
                                           struct crypto_ahash *tfm)
 {
diff --git a/include/linux/crypto.h b/include/linux/crypto.h
index 44c72f0f9b05..77a1f3d9416d 100644
--- a/include/linux/crypto.h
+++ b/include/linux/crypto.h
@@ -221,6 +221,7 @@ struct ablkcipher_alg {
 
 struct ahash_alg {
         int (*init)(struct ahash_request *req);
+        int (*reinit)(struct ahash_request *req);
         int (*update)(struct ahash_request *req);
         int (*final)(struct ahash_request *req);
         int (*digest)(struct ahash_request *req);