crypto: shash - Handle partial blocks in API

Provide an option to handle the partial blocks in the shash API.
Almost every hash algorithm has a block size and are only able
to hash partial blocks on finalisation.

Rather than duplicating the partial block handling many times,
add this functionality to the shash API.

It is optional (e.g., hmac would never need this by relying on
the partial block handling of the underlying hash), and to enable
it set the bit CRYPTO_AHASH_ALG_BLOCK_ONLY.

The export format is always that of the underlying hash export,
plus the partial block buffer, followed by a single-byte for the
partial block length.

Set the bit CRYPTO_AHASH_ALG_FINAL_NONZERO to withhold an extra
byte in the partial block.  This will come in handy when this
is extended to ahash where hardware often can't deal with a
zero-length final.

It will also be used for algorithms requiring an extra block for
finalisation (e.g., cmac).

As an optimisation, set the bit CRYPTO_AHASH_ALG_FINUP_MAX if
the algorithm wishes to get as much data as possible instead of
just the last partial block.

The descriptor will be zeroed after finalisation.

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

1 files changed, 15 insertions, 0 deletions

diff --git a/include/crypto/internal/hash.h b/include/crypto/internal/hash.h
index 45c728ac2621..1e80dd084a23 100644
--- a/include/crypto/internal/hash.h
+++ b/include/crypto/internal/hash.h
@@ -11,6 +11,15 @@
 #include <crypto/algapi.h>
 #include <crypto/hash.h>
 
+/* Set this bit to handle partial blocks in the API. */
+#define CRYPTO_AHASH_ALG_BLOCK_ONLY	0x01000000
+
+/* Set this bit if final requires at least one byte. */
+#define CRYPTO_AHASH_ALG_FINAL_NONZERO	0x02000000
+
+/* Set this bit if finup can deal with multiple blocks. */
+#define CRYPTO_AHASH_ALG_FINUP_MAX	0x04000000
+
 #define HASH_FBREQ_ON_STACK(name, req) \
         char __##name##_req[sizeof(struct ahash_request) + \
                             MAX_SYNC_HASH_REQSIZE] CRYPTO_MINALIGN_ATTR; \
@@ -281,5 +290,11 @@ static inline struct ahash_request *ahash_fbreq_on_stack_init(
 	return req;
 }
 
+/* Return the state size without partial block for block-only algorithms. */
+static inline unsigned int crypto_shash_coresize(struct crypto_shash *tfm)
+{
+	return crypto_shash_statesize(tfm) - crypto_shash_blocksize(tfm) - 1;
+}
+
 #endif	/* _CRYPTO_INTERNAL_HASH_H */