[PATCH] arm64 sha2-ce finup: correct digest for empty data

[PATCH] arm64 sha2-ce finup: correct digest for empty data

[Elena Petrova]

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

Re: [PATCH] arm64 sha2-ce finup: correct digest for empty data

[Ard Biesheuvel]

On Tue, 28 May 2019 at 16:35, Elena Petrova <lenaptr@google.com> wrote:
>
> 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>

Thanks again

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
>  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
>

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

[Herbert Xu]

On Tue, May 28, 2019 at 03:35:06PM +0100, Elena Petrova wrote:
> 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>
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  arch/arm64/crypto/sha2-ce-glue.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt