crypto: shash - Export/import hash state only

This patch replaces the full descriptor export with an export of
the partial hash state.  This allows the use of a consistent export
format across all implementations of a given algorithm.

This is useful because a number of cases require the use of the
partial hash state, e.g., PadLock can use the SHA1 hash state
to get around the fact that it can only hash contiguous data
chunks.

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

crypto/shash.c

diff --git a/crypto/shash.c b/crypto/shash.c
index 23e05a1..14a3b70 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -172,19 +172,15 @@
 }
 EXPORT_SYMBOL_GPL(crypto_shash_digest);
 
-int crypto_shash_import(struct shash_desc *desc, const u8 *in)
+static int shash_no_export(struct shash_desc *desc, void *out)
 {
-	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)
-		return alg->reinit(desc);
-
-	return 0;
+	return -ENOSYS;
 }
-EXPORT_SYMBOL_GPL(crypto_shash_import);
+
+static int shash_no_import(struct shash_desc *desc, const void *in)
+{
+	return -ENOSYS;
+}
 
 static int shash_async_setkey(struct crypto_ahash *tfm, const u8 *key,
 			      unsigned int keylen)
@@ -484,12 +480,19 @@
 	struct crypto_alg *base = &alg->base;
 
 	if (alg->digestsize > PAGE_SIZE / 8 ||
-	    alg->descsize > PAGE_SIZE / 8)
+	    alg->descsize > PAGE_SIZE / 8 ||
+	    alg->statesize > PAGE_SIZE / 8)
 		return -EINVAL;
 
 	base->cra_type = &crypto_shash_type;
 	base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
 	base->cra_flags |= CRYPTO_ALG_TYPE_SHASH;
+
+	if (!alg->import)
+		alg->import = shash_no_import;
+	if (!alg->export)
+		alg->export = shash_no_export;
+
 	return 0;
 }