Re: [PATCH] crypto: pkcs7 - Use constant-time message digest comparison

Lukas Wunner <[email protected]> Mon, 20 Jul 2026 08:21:17 +0200

Newsgroups	org.kernel.vger.keyrings,org.kernel.vger.linux-crypto,org.kernel.vger.linux-kernel
Message-ID	<[email protected]>

On Mon, Jul 20, 2026 at 11:23:16AM +0800, Jiangshan Yi wrote:
> +++ b/crypto/asymmetric_keys/pkcs7_verify.c
> @@ -93,8 +94,8 @@ static int pkcs7_digest(struct pkcs7_message *pkcs7,
>  			goto error;
>  		}
>  
> -		if (memcmp(sig->m, sinfo->msgdigest,
> -			   sinfo->msgdigest_len) != 0) {
> +		if (crypto_memneq(sig->m, sinfo->msgdigest,
> +				  sinfo->msgdigest_len)) {
>  			pr_warn("Sig %u: Message digest doesn't match\n",
>  				sinfo->index);
>  			ret = -EKEYREJECTED;

The exact same patch was previously submitted by someone else
and rejected:

https://lore.kernel.org/all/alEsSl8i1_FpoU0f@fudgebox/T/#u