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([2a04:241e:502:1d80:f865:21f3:80af:d6db]) by smtp.gmail.com with ESMTPSA id b11sm1174848eja.104.2021.08.12.12.46.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Aug 2021 12:46:50 -0700 (PDT) Subject: Re: [RFCv2 1/9] tcp: authopt: Initial support and key management From: Leonard Crestez To: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Eric Dumazet , "David S. Miller" , Herbert Xu , Kuniyuki Iwashima , David Ahern , Hideaki YOSHIFUJI , Jakub Kicinski , Yuchung Cheng , Francesco Ruggeri , Mat Martineau , Christoph Paasch , Ivan Delalande , Priyaranjan Jha , Menglong Dong , open list , linux-crypto@vger.kernel.org, Network Development , Dmitry Safonov References: <67c1471683200188b96a3f712dd2e8def7978462.1628544649.git.cdleonard@gmail.com> <1e2848fb-1538-94aa-0431-636fa314a36d@gmail.com> Message-ID: <785d945e-c0d2-fee5-39d8-99dc06a074f1@gmail.com> Date: Thu, 12 Aug 2021 22:46:48 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <1e2848fb-1538-94aa-0431-636fa314a36d@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 8/11/21 11:29 AM, Leonard Crestez wrote: > On 8/10/21 11:41 PM, Dmitry Safonov wrote: >> On Tue, 10 Aug 2021 at 02:50, Leonard Crestez >>> +       /* If an old value exists for same local_id it is deleted */ >>> +       key_info = __tcp_authopt_key_info_lookup(sk, info, >>> opt.local_id); >>> +       if (key_info) >>> +               tcp_authopt_key_del(sk, info, key_info); >>> +       key_info = sock_kmalloc(sk, sizeof(*key_info), GFP_KERNEL | >>> __GFP_ZERO); >>> +       if (!key_info) >>> +               return -ENOMEM; >> >> 1. You don't need sock_kmalloc() together with tcp_authopt_key_del(). >>      It just frees the memory and allocates it back straight away - no >> sense in doing that. > > The list is scanned in multiple places in later commits using nothing > but an rcu_read_lock, this means that keys can't be updated in-place. > >> 2. I think RFC says you must not allow a user to change an existing key: >>> MKT parameters are not changed. Instead, new MKTs can be installed, >>> and a connection >>> can change which MKT it uses. >> >> IIUC, it means that one can't just change an existing MKT, but one can >> remove and later >> add MKT with the same (send_id, recv_id, src_addr/port, dst_addr/port). >> >> So, a reasonable thing to do: >> if (key_info) >>      return -EEXIST. > > You're right, making the user delete keys explicitly is better. On a second thought this might be required to mark keys as "send-only" and "recv-only" atomically. Separately from RFC5925 some vendors implement a "keychain" model based on RFC8177 where each key has a distinct "accept-lifetime" and a "send-lifetime". This could be implemented by adding flags "expired_for_send" and "expired_for_recv" but requires the ability to set an expiration mark without the key ever being deleted. -- Regards, Leonard