[PATCH 4.19 175/271] crypto: arm64/sha2-ce - correct digest for empty data in finup

From: Greg Kroah-Hartman
Date: Thu Jul 25 2019 - 11:02:35 EST

From: Elena Petrova <lenaptr@xxxxxxxxxx>

commit 6bd934de1e393466b319d29c4427598fda096c57 upstream.

The sha256-ce finup implementation for ARM64 produces wrong digest
for empty input (len=0). Expected: the actual digest, result: initial
value of SHA internal state. The error is in sha256_ce_finup:
for empty data `finalize` will be 1, so the code is relying on
sha2_ce_transform to make the final round. However, in
sha256_base_do_update, the block function will not be called when
len == 0.

Fix it by setting finalize to 0 if data is empty.

Fixes: 03802f6a80b3a ("crypto: arm64/sha2-ce - move SHA-224/256 ARMv8 implementation to base layer")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Elena Petrova <lenaptr@xxxxxxxxxx>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/arm64/crypto/sha2-ce-glue.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/crypto/sha2-ce-glue.c
+++ b/arch/arm64/crypto/sha2-ce-glue.c
@@ -59,7 +59,7 @@ static int sha256_ce_finup(struct shash_
unsigned int len, u8 *out)
struct sha256_ce_state *sctx = shash_desc_ctx(desc);
- bool finalize = !sctx->sst.count && !(len % SHA256_BLOCK_SIZE);
+ bool finalize = !sctx->sst.count && !(len % SHA256_BLOCK_SIZE) && len;

if (!may_use_simd()) {
if (len)