linux-kernel - [PATCH 4.9 080/223] crypto: arm64/sha2-ce - correct digest for empty data in finup

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Message-Id: <20190802092244.096277859@linuxfoundation.org>
Date:   Fri,  2 Aug 2019 11:35:05 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Elena Petrova <lenaptr@...gle.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4.9 080/223] crypto: arm64/sha2-ce - correct digest for empty data in finup

From: Elena Petrova <lenaptr@...gle.com>

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@...r.kernel.org
Signed-off-by: Elena Petrova <lenaptr@...gle.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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
@@ -52,7 +52,7 @@ 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;
 
 	/*
 	 * Allow the asm code to perform the finalization if there is no