Re: [PATCH v10 net-next 08/23] net/tcp: Add AO sign to RST packets

[Simon Horman <horms@kernel.org>]

On Tue, Aug 15, 2023 at 08:14:37PM +0100, Dmitry Safonov wrote:
> Wire up sending resets to TCP-AO hashing.
> 
> Co-developed-by: Francesco Ruggeri <fruggeri@arista.com>
> Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
> Co-developed-by: Salam Noureddine <noureddine@arista.com>
> Signed-off-by: Salam Noureddine <noureddine@arista.com>
> Signed-off-by: Dmitry Safonov <dima@arista.com>
> Acked-by: David Ahern <dsahern@kernel.org>

> ---
>  include/net/tcp_ao.h |  12 +++++
>  net/ipv4/tcp_ao.c    | 104 ++++++++++++++++++++++++++++++++++++++++++-
>  net/ipv4/tcp_ipv4.c  |  69 ++++++++++++++++++++++------
>  net/ipv6/tcp_ipv6.c  |  70 ++++++++++++++++++++++-------
>  4 files changed, 225 insertions(+), 30 deletions(-)
> 
> diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
> index e685ad9db949..67f997aabd9c 100644
> --- a/include/net/tcp_ao.h
> +++ b/include/net/tcp_ao.h
> @@ -117,12 +117,24 @@ int tcp_ao_hash_skb(unsigned short int family,
>  		    const u8 *tkey, int hash_offset, u32 sne);
>  int tcp_parse_ao(struct sock *sk, int cmd, unsigned short int family,
>  		 sockptr_t optval, int optlen);
> +struct tcp_ao_key *tcp_ao_established_key(struct tcp_ao_info *ao,
> +					  int sndid, int rcvid);
>  int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
>  			    unsigned int len, struct tcp_sigpool *hp);
>  void tcp_ao_destroy_sock(struct sock *sk);
>  struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
>  				    const union tcp_ao_addr *addr,
>  				    int family, int sndid, int rcvid);
> +int tcp_ao_hash_hdr(unsigned short family, char *ao_hash,
> +		    struct tcp_ao_key *key, const u8 *tkey,
> +		    const union tcp_ao_addr *daddr,
> +		    const union tcp_ao_addr *saddr,
> +		    const struct tcphdr *th, u32 sne);
> +int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb,
> +			 const struct tcp_ao_hdr *aoh, int l3index, u32 seq,
> +			 struct tcp_ao_key **key, char **traffic_key,
> +			 bool *allocated_traffic_key, u8 *keyid, u32 *sne);
> +
>  /* ipv4 specific functions */
>  int tcp_v4_parse_ao(struct sock *sk, int cmd, sockptr_t optval, int optlen);
>  struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
> diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c

...

> @@ -435,6 +495,46 @@ struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
>  	return tcp_ao_do_lookup(sk, addr, AF_INET, sndid, rcvid);
>  }
>  
> +int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb,
> +			 const struct tcp_ao_hdr *aoh, int l3index, u32 seq,
> +			 struct tcp_ao_key **key, char **traffic_key,
> +			 bool *allocated_traffic_key, u8 *keyid, u32 *sne)
> +{
> +	struct tcp_ao_info *ao_info;
> +
> +	*allocated_traffic_key = false;
> +	/* If there's no socket - than initial sisn/disn are unknown.
> +	 * Drop the segment. RFC5925 (7.7) advises to require graceful
> +	 * restart [RFC4724]. Alternatively, the RFC5925 advises to
> +	 * save/restore traffic keys before/after reboot.
> +	 * Linux TCP-AO support provides TCP_AO_ADD_KEY and TCP_AO_REPAIR
> +	 * options to restore a socket post-reboot.
> +	 */
> +	if (!sk)
> +		return -ENOTCONN;
> +
> +	if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_NEW_SYN_RECV)) {
> +		return -1;
> +	} else {
> +		struct tcp_ao_key *rnext_key;
> +
> +		if (sk->sk_state == TCP_TIME_WAIT)
> +			return -1;
> +		ao_info = rcu_dereference(tcp_sk(sk)->ao_info);
> +		if (!ao_info)
> +			return -ENOENT;
> +
> +		*key = tcp_ao_established_key(ao_info, aoh->rnext_keyid, -1);
> +		if (!*key)
> +			return -ENOENT;
> +		*traffic_key = snd_other_key(*key);
> +		rnext_key = READ_ONCE(ao_info->rnext_key);
> +		*keyid = rnext_key->rcvid;
> +		*sne = 0;
> +	}
> +	return 0;
> +}
> +
>  static int tcp_ao_cache_traffic_keys(const struct sock *sk,
>  				     struct tcp_ao_info *ao,
>  				     struct tcp_ao_key *ao_key)
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 31169971cc56..f07a12f478d4 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -657,6 +657,52 @@ void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb)
>  }
>  EXPORT_SYMBOL(tcp_v4_send_check);
>  
> +#define REPLY_OPTIONS_LEN      (MAX_TCP_OPTION_SPACE / sizeof(__be32))
> +
> +static bool tcp_v4_ao_sign_reset(const struct sock *sk, struct sk_buff *skb,
> +				 const struct tcp_ao_hdr *aoh,
> +				 struct ip_reply_arg *arg, struct tcphdr *reply,
> +				 __be32 reply_options[REPLY_OPTIONS_LEN])
> +{
> +#ifdef CONFIG_TCP_AO
> +	int sdif = tcp_v4_sdif(skb);
> +	int dif = inet_iif(skb);
> +	int l3index = sdif ? dif : 0;
> +	bool allocated_traffic_key;
> +	struct tcp_ao_key *key;
> +	char *traffic_key;
> +	bool drop = true;
> +	u32 ao_sne = 0;
> +	u8 keyid;
> +
> +	rcu_read_lock();
> +	if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, reply->seq,
> +				 &key, &traffic_key, &allocated_traffic_key,
> +				 &keyid, &ao_sne))

Hi Dmitry,

The type of the 4th parameter of tcp_ao_prepare_reset() (seq) is u32,
but here a __be32 value is passed.

Also, it seems that parameter is unused by tcp_ao_prepare_reset().

> +		goto out;
> +
> +	reply_options[0] = htonl((TCPOPT_AO << 24) | (tcp_ao_len(key) << 16) |
> +				 (aoh->rnext_keyid << 8) | keyid);
> +	arg->iov[0].iov_len += round_up(tcp_ao_len(key), 4);
> +	reply->doff = arg->iov[0].iov_len / 4;
> +
> +	if (tcp_ao_hash_hdr(AF_INET, (char *)&reply_options[1],
> +			    key, traffic_key,
> +			    (union tcp_ao_addr *)&ip_hdr(skb)->saddr,
> +			    (union tcp_ao_addr *)&ip_hdr(skb)->daddr,
> +			    reply, ao_sne))
> +		goto out;
> +	drop = false;
> +out:
> +	rcu_read_unlock();
> +	if (allocated_traffic_key)
> +		kfree(traffic_key);
> +	return drop;
> +#else
> +	return true;
> +#endif
> +}
> +
>  /*
>   *	This routine will send an RST to the other tcp.
>   *

...

> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c

...

> @@ -1064,6 +1088,19 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
>  		ack_seq = ntohl(th->seq) + th->syn + th->fin + skb->len -
>  			  (th->doff << 2);
>  
> +#ifdef CONFIG_TCP_AO
> +	if (aoh) {
> +		int l3index;
> +
> +		l3index = tcp_v6_sdif(skb) ? tcp_v6_iif_l3_slave(skb) : 0;
> +		if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, htonl(seq),

Ditto.

> +					 &ao_key, &traffic_key,
> +					 &allocated_traffic_key,
> +					 &rcv_next, &ao_sne))
> +			goto out;
> +	}
> +#endif
> +
>  	if (sk) {
>  		oif = sk->sk_bound_dev_if;
>  		if (sk_fullsock(sk)) {

...