Re: [PATCH URGENT crypto v2] crypto: arm64/chacha - correctly walk through blocks

[Eric Biggers]

On Wed, Mar 18, 2020 at 08:27:32PM -0600, Jason A. Donenfeld wrote:
> Prior, passing in chunks of 2, 3, or 4, followed by any additional
> chunks would result in the chacha state counter getting out of sync,
> resulting in incorrect encryption/decryption, which is a pretty nasty
> crypto vuln: "why do images look weird on webpages?" WireGuard users
> never experienced this prior, because we have always, out of tree, used
> a different crypto library, until the recent Frankenzinc addition. This
> commit fixes the issue by advancing the pointers and state counter by
> the actual size processed. It also fixes up a bug in the (optional,
> costly) stride test that prevented it from running on arm64.
> 
> Fixes: b3aad5bad26a ("crypto: arm64/chacha - expose arm64 ChaCha routine as library function")
> Reported-and-tested-by: Emil Renner Berthing <kernel@xxxxxxxx>
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v5.5+
> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
> ---
>  arch/arm64/crypto/chacha-neon-glue.c   |  8 ++++----
>  lib/crypto/chacha20poly1305-selftest.c | 11 ++++++++---
>  2 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/crypto/chacha-neon-glue.c b/arch/arm64/crypto/chacha-neon-glue.c
> index c1f9660d104c..37ca3e889848 100644
> --- a/arch/arm64/crypto/chacha-neon-glue.c
> +++ b/arch/arm64/crypto/chacha-neon-glue.c
> @@ -55,10 +55,10 @@ static void chacha_doneon(u32 *state, u8 *dst, const u8 *src,
>  			break;
>  		}
>  		chacha_4block_xor_neon(state, dst, src, nrounds, l);
> -		bytes -= CHACHA_BLOCK_SIZE * 5;
> -		src += CHACHA_BLOCK_SIZE * 5;
> -		dst += CHACHA_BLOCK_SIZE * 5;
> -		state[12] += 5;
> +		bytes -= l;
> +		src += l;
> +		dst += l;
> +		state[12] += DIV_ROUND_UP(l, CHACHA_BLOCK_SIZE);
>  	}
>  }
>  
> diff --git a/lib/crypto/chacha20poly1305-selftest.c b/lib/crypto/chacha20poly1305-selftest.c
> index c391a91364e9..fa43deda2660 100644
> --- a/lib/crypto/chacha20poly1305-selftest.c
> +++ b/lib/crypto/chacha20poly1305-selftest.c
> @@ -9028,10 +9028,15 @@ bool __init chacha20poly1305_selftest(void)
>  	     && total_len <= 1 << 10; ++total_len) {
>  		for (i = 0; i <= total_len; ++i) {
>  			for (j = i; j <= total_len; ++j) {
> +				k = 0;
>  				sg_init_table(sg_src, 3);
> -				sg_set_buf(&sg_src[0], input, i);
> -				sg_set_buf(&sg_src[1], input + i, j - i);
> -				sg_set_buf(&sg_src[2], input + j, total_len - j);
> +				if (i)
> +					sg_set_buf(&sg_src[k++], input, i);
> +				if (j - i)
> +					sg_set_buf(&sg_src[k++], input + i, j - i);
> +				if (total_len - j)
> +					sg_set_buf(&sg_src[k++], input + j, total_len - j);
> +				sg_init_marker(sg_src, k);
>  				memset(computed_output, 0, total_len);
>  				memset(input, 0, total_len);
>  

Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>

Herbert, can you send this to Linus for 5.6?

- Eric