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>
diff --git a/crypto/shash.c b/crypto/shash.c
index 3f4c713..26aff3f 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -172,6 +172,20 @@
}
EXPORT_SYMBOL_GPL(crypto_shash_digest);
+int crypto_shash_import(struct shash_desc *desc, const u8 *in)
+{
+ struct crypto_shash *tfm = desc->tfm;
+ struct shash_alg *alg = crypto_shash_alg(tfm);
+
+ memcpy(shash_desc_ctx(desc), in, crypto_shash_descsize(tfm));
+
+ if (alg->reinit)
+ alg->reinit(desc);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_shash_import);
+
static int shash_async_setkey(struct crypto_ahash *tfm, const u8 *key,
unsigned int keylen)
{