netdev - Re: [PATCH net 2/3] tls: clear key material from kernel memory when do_tls_setsockopt

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Message-ID: <567f747b-e817-4a9b-1768-96575caea845@mellanox.com>
Date:   Wed, 5 Sep 2018 16:53:54 +0300
From:   Boris Pismenny <borisp@...lanox.com>
To:     Sabrina Dubroca <sd@...asysnail.net>, netdev@...r.kernel.org
Cc:     Ilya Lesokhin <ilyal@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        Dave Watson <davejwatson@...com>
Subject: Re: [PATCH net 2/3] tls: clear key material from kernel memory when
 do_tls_setsockopt_conf fails

Hi Sabrina,

On 9/5/2018 4:21 PM, Sabrina Dubroca wrote:
> Fixes: 3c4d7559159b ("tls: kernel TLS support")
> Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
> ---
>   net/tls/tls_main.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
> index 180b6640e531..0d432d025471 100644
> --- a/net/tls/tls_main.c
> +++ b/net/tls/tls_main.c
> @@ -499,7 +499,7 @@ static int do_tls_setsockopt_conf(struct sock *sk, char __user *optval,
>   	goto out;
>   
>   err_crypto_info:
> -	memset(crypto_info, 0, sizeof(*crypto_info));
> +	memzero_explicit(crypto_info, sizeof(struct tls12_crypto_info_aes_gcm_128));

Besides the key, there are other (not secret) information in 
tls12_crypto_info_aes_gcm_128. I'd prefer you do not delete it to enable 
users to obtain it (using getsockopt) in case we decide to implement a 
fallback to userspace in the future. Such a fallback must obtain the 
kernel's iv, and record sequence number.

Thanks,
Boris.