Re: [PATCH net-next v6 23/23] net: WireGuard secure network tunnel

Ivan Labáth
2018-11-05T13:06:51Z

On 26. 9. 2018 18:04, Jason A. Donenfeld wrote:
> Hi Ivan,
>
> On Wed, Sep 26, 2018 at 6:00 PM Ivan Labáth <labokml@labo.rs> wrote:
>>
>> On 25.09.2018 16:56, Jason A. Donenfeld wrote:
>>> Extensive documentation and description of the protocol and
>>> considerations, along with formal proofs of the cryptography, are> available at:
>>>
>>> * https://www.wireguard.com/
>>> * https://www.wireguard.com/papers/wireguard.pdf
>> []
>>> +enum { HANDSHAKE_DSCP = 0x88 /* AF41, plus 00 ECN */ };
>> []
>>> + if (skb->protocol == htons(ETH_P_IP)) {
>>> + len = ntohs(ip_hdr(skb)->tot_len);
>>> + if (unlikely(len < sizeof(struct iphdr)))
>>> + goto dishonest_packet_size;
>>> + if (INET_ECN_is_ce(PACKET_CB(skb)->ds))
>>> + IP_ECN_set_ce(ip_hdr(skb));
>>> + } else if (skb->protocol == htons(ETH_P_IPV6)) {
>>> + len = ntohs(ipv6_hdr(skb)->payload_len) +
>>> + sizeof(struct ipv6hdr);
>>> + if (INET_ECN_is_ce(PACKET_CB(skb)->ds))
>>> + IP6_ECN_set_ce(skb, ipv6_hdr(skb));
>>> + } else
>> []
>>> + skb_queue_walk (&packets, skb) {
>>> + /* 0 for no outer TOS: no leak. TODO: should we use flowi->tos
>>> + * as outer? */
>>> + PACKET_CB(skb)->ds = ip_tunnel_ecn_encap(0, ip_hdr(skb), skb);
>>> + PACKET_CB(skb)->nonce =
>>> + atomic64_inc_return(&key->counter.counter) - 1;
>>> + if (unlikely(PACKET_CB(skb)->nonce >= REJECT_AFTER_MESSAGES))
>>> + goto out_invalid;
>>> + }
>> Hi,
>>
>> is there documentation and/or rationale for ecn handling?
>> Quick search for ecn and dscp didn't reveal any.
>
> ECN support was developed with Dave Taht so that it does the right
> thing with CAKE and such. He's CC'd, so that he can fill in details,
> and sure, we can write these up. As well, I can add the rationale for
> the handshake-packet-specific DSCP value to the paper in the next few
> days; thanks for pointing out these documentation oversights.
>
> Jason
>

Any news on this?

To be clear, question is not about an insignificant documentation
oversight. It is about copying bits from inner packets to outer packets
of a secure* tunnel and documenting it AFAICT nowhere, while claiming
extensive documentation.

* it really should be specified what secure tunnel means, as it has many
plausible interpretations and wireguard surely does not fulfill all of them.

Ivan