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Date:   Mon, 6 Jul 2020 12:07:17 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Herbert Xu <herbert@gondor.apana.org.au>
Cc:     Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
Subject: Re: [PATCH] crypto: chacha - Add DEFINE_CHACHA_STATE macro
Message-ID: <20200706190717.GB736284@gmail.com>
References: <20200706133733.GA6479@gondor.apana.org.au>
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On Mon, Jul 06, 2020 at 11:37:34PM +1000, Herbert Xu wrote:
> diff --git a/lib/crypto/chacha20poly1305.c b/lib/crypto/chacha20poly1305.c
> index ad0699ce702f9..1d7bb0b91b83c 100644
> --- a/lib/crypto/chacha20poly1305.c
> +++ b/lib/crypto/chacha20poly1305.c
> @@ -94,7 +94,7 @@ void chacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len,
>  			      const u64 nonce,
>  			      const u8 key[CHACHA20POLY1305_KEY_SIZE])
>  {
> -	u32 chacha_state[CHACHA_STATE_WORDS];
> +	DEFINE_CHACHA_STATE(chacha_state);
>  	u32 k[CHACHA_KEY_WORDS];
>  	__le64 iv[2];
>  
> @@ -116,7 +116,7 @@ void xchacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len,
>  			       const u8 nonce[XCHACHA20POLY1305_NONCE_SIZE],
>  			       const u8 key[CHACHA20POLY1305_KEY_SIZE])
>  {
> -	u32 chacha_state[CHACHA_STATE_WORDS];
> +	DEFINE_CHACHA_STATE(chacha_state);
>  
>  	xchacha_init(chacha_state, key, nonce);
>  	__chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len, chacha_state);
> @@ -172,7 +172,7 @@ bool chacha20poly1305_decrypt(u8 *dst, const u8 *src, const size_t src_len,
>  			      const u64 nonce,
>  			      const u8 key[CHACHA20POLY1305_KEY_SIZE])
>  {
> -	u32 chacha_state[CHACHA_STATE_WORDS];
> +	DEFINE_CHACHA_STATE(chacha_state);
>  	u32 k[CHACHA_KEY_WORDS];
>  	__le64 iv[2];
>  	bool ret;
> @@ -198,7 +198,7 @@ bool xchacha20poly1305_decrypt(u8 *dst, const u8 *src, const size_t src_len,
>  			       const u8 nonce[XCHACHA20POLY1305_NONCE_SIZE],
>  			       const u8 key[CHACHA20POLY1305_KEY_SIZE])
>  {
> -	u32 chacha_state[CHACHA_STATE_WORDS];
> +	DEFINE_CHACHA_STATE(chacha_state);
>  
>  	xchacha_init(chacha_state, key, nonce);
>  	return __chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len,
> @@ -216,7 +216,7 @@ bool chacha20poly1305_crypt_sg_inplace(struct scatterlist *src,
>  {
>  	const u8 *pad0 = page_address(ZERO_PAGE(0));
>  	struct poly1305_desc_ctx poly1305_state;
> -	u32 chacha_state[CHACHA_STATE_WORDS];
> +	DEFINE_CHACHA_STATE(chacha_state);
>  	struct sg_mapping_iter miter;
>  	size_t partial = 0;
>  	unsigned int flags;

This changes chacha_state to be a pointer, which breaks clearing the state
because that uses sizeof(chacha_state):

	memzero_explicit(chacha_state, sizeof(chacha_state));

It would need to be changed to use CHACHA_BLOCK_SIZE.

- Eric