linux-kernel - Re: [PATCH v2 09/25] tcp: authopt: Disable via sysctl by default

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Message-ID: <cccdd347-57ee-62e5-2824-a3e7e2910395@gmail.com>
Date:   Fri, 5 Nov 2021 01:46:10 +0000
From:   Dmitry Safonov <0x7f454c46@...il.com>
To:     Leonard Crestez <cdleonard@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Francesco Ruggeri <fruggeri@...sta.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Christoph Paasch <cpaasch@...le.com>,
        Ivan Delalande <colona@...sta.com>,
        Priyaranjan Jha <priyarjha@...gle.com>, netdev@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 09/25] tcp: authopt: Disable via sysctl by default

On 11/1/21 16:34, Leonard Crestez wrote:
> This is mainly intended to protect against local privilege escalations
> through a rarely used feature so it is deliberately not namespaced.
> 
> Enforcement is only at the setsockopt level, this should be enough to
> ensure that the tcp_authopt_needed static key never turns on.
> 
> No effort is made to handle disabling when the feature is already in
> use.
> 
> Signed-off-by: Leonard Crestez <cdleonard@...il.com>
> ---
[..]
> diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c
> index 5e80e5e5e36e..7c49dcce7d24 100644
> --- a/net/ipv4/tcp_authopt.c
> +++ b/net/ipv4/tcp_authopt.c
> @@ -3,10 +3,15 @@
>  #include <linux/kernel.h>
>  #include <net/tcp.h>
>  #include <net/tcp_authopt.h>
>  #include <crypto/hash.h>
>  
> +/* This is mainly intended to protect against local privilege escalations through
> + * a rarely used feature so it is deliberately not namespaced.
> + */
> +int sysctl_tcp_authopt;

Could you add pr_warn_once() for setsockopt() without this set, so that
it's visible in dmesg for a user that gets -EPERM.

Thanks,
          Dmitry