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Date:   Tue, 28 May 2019 15:35:06 +0100
Message-Id: <20190528143506.212198-1-lenaptr@google.com>
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Subject: [PATCH] arm64 sha2-ce finup: correct digest for empty data
From:   Elena Petrova <lenaptr@google.com>
To:     linux-crypto@vger.kernel.org
Cc:     Elena Petrova <lenaptr@google.com>, stable@vger.kernel.org
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Sender: linux-crypto-owner@vger.kernel.org
Precedence: bulk

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@vger.kernel.org
Signed-off-by: Elena Petrova <lenaptr@google.com>
---
 arch/arm64/crypto/sha2-ce-glue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/crypto/sha2-ce-glue.c b/arch/arm64/crypto/sha2-ce-glue.c
index a725997e55f2..6a5ade974a35 100644
--- a/arch/arm64/crypto/sha2-ce-glue.c
+++ b/arch/arm64/crypto/sha2-ce-glue.c
@@ -60,7 +60,7 @@ static int sha256_ce_finup(struct shash_desc *desc, const u8 *data,
 			   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 (!crypto_simd_usable()) {
 		if (len)
-- 
2.22.0.rc1.257.g3120a18244-goog