Commit 9427c6aa authored by Dmitry Safonov's avatar Dmitry Safonov Committed by David S. Miller
Browse files

net/tcp: Sign SYN-ACK segments with TCP-AO 



Similarly to RST segments, wire SYN-ACKs to TCP-AO.
tcp_rsk_used_ao() is handy here to check if the request socket used AO
and needs a signature on the outgoing segments.

Co-developed-by: default avatarFrancesco Ruggeri <fruggeri@arista.com>
Signed-off-by: default avatarFrancesco Ruggeri <fruggeri@arista.com>
Co-developed-by: default avatarSalam Noureddine <noureddine@arista.com>
Signed-off-by: default avatarSalam Noureddine <noureddine@arista.com>
Signed-off-by: default avatarDmitry Safonov <dima@arista.com>
Acked-by: default avatarDavid Ahern <dsahern@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 06b22ef2

include/net/tcp.h

+3 −0
Original line number Diff line number Diff line
@@ -2221,6 +2221,9 @@ struct tcp_request_sock_ops { 
					struct request_sock *req,

					int sndid, int rcvid);

	int (*ao_calc_key)(struct tcp_ao_key *mkt, u8 *key, struct request_sock *sk);

	int (*ao_synack_hash)(char *ao_hash, struct tcp_ao_key *mkt,

			      struct request_sock *req, const struct sk_buff *skb,

			      int hash_offset, u32 sne);

#endif

#ifdef CONFIG_SYN_COOKIES

	__u32 (*cookie_init_seq)(const struct sk_buff *skb,

include/net/tcp_ao.h

+6 −0
Original line number Diff line number Diff line
@@ -147,6 +147,9 @@ int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb, 
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,

				    int sndid, int rcvid);

int tcp_v4_ao_synack_hash(char *ao_hash, struct tcp_ao_key *mkt,

			  struct request_sock *req, const struct sk_buff *skb,

			  int hash_offset, u32 sne);

int tcp_v4_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,

			  const struct sock *sk,

			  __be32 sisn, __be32 disn, bool send);
@@ -181,6 +184,9 @@ int tcp_v6_ao_hash_skb(char *ao_hash, struct tcp_ao_key *key, 
		       const struct sock *sk, const struct sk_buff *skb,

		       const u8 *tkey, int hash_offset, u32 sne);

int tcp_v6_parse_ao(struct sock *sk, int cmd, sockptr_t optval, int optlen);

int tcp_v6_ao_synack_hash(char *ao_hash, struct tcp_ao_key *ao_key,

			  struct request_sock *req, const struct sk_buff *skb,

			  int hash_offset, u32 sne);

void tcp_ao_established(struct sock *sk);

void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb);

void tcp_ao_connect_init(struct sock *sk);

net/ipv4/tcp_ao.c

+22 −0
Original line number Diff line number Diff line
@@ -568,6 +568,28 @@ int tcp_v4_ao_hash_skb(char *ao_hash, struct tcp_ao_key *key, 
			       tkey, hash_offset, sne);

}



int tcp_v4_ao_synack_hash(char *ao_hash, struct tcp_ao_key *ao_key,

			  struct request_sock *req, const struct sk_buff *skb,

			  int hash_offset, u32 sne)

{

	void *hash_buf = NULL;

	int err;



	hash_buf = kmalloc(tcp_ao_digest_size(ao_key), GFP_ATOMIC);

	if (!hash_buf)

		return -ENOMEM;



	err = tcp_v4_ao_calc_key_rsk(ao_key, hash_buf, req);

	if (err)

		goto out;



	err = tcp_ao_hash_skb(AF_INET, ao_hash, ao_key, req_to_sk(req), skb,

			      hash_buf, hash_offset, sne);

out:

	kfree(hash_buf);

	return err;

}



struct tcp_ao_key *tcp_v4_ao_lookup_rsk(const struct sock *sk,

					struct request_sock *req,

					int sndid, int rcvid)

net/ipv4/tcp_ipv4.c

+1 −0
Original line number Diff line number Diff line
@@ -1681,6 +1681,7 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = { 
#ifdef CONFIG_TCP_AO

	.ao_lookup	=	tcp_v4_ao_lookup_rsk,

	.ao_calc_key	=	tcp_v4_ao_calc_key_rsk,

	.ao_synack_hash	=	tcp_v4_ao_synack_hash,

#endif

#ifdef CONFIG_SYN_COOKIES

	.cookie_init_seq =	cookie_v4_init_sequence,

net/ipv4/tcp_output.c

+56 −16
Original line number Diff line number Diff line
@@ -886,7 +886,7 @@ static unsigned int tcp_synack_options(const struct sock *sk, 
				       struct request_sock *req,

				       unsigned int mss, struct sk_buff *skb,

				       struct tcp_out_options *opts,

				       const struct tcp_md5sig_key *md5,

				       const struct tcp_key *key,

				       struct tcp_fastopen_cookie *foc,

				       enum tcp_synack_type synack_type,

				       struct sk_buff *syn_skb)
@@ -894,8 +894,7 @@ static unsigned int tcp_synack_options(const struct sock *sk, 
	struct inet_request_sock *ireq = inet_rsk(req);

	unsigned int remaining = MAX_TCP_OPTION_SPACE;



#ifdef CONFIG_TCP_MD5SIG

	if (md5) {

	if (tcp_key_is_md5(key)) {

		opts->options |= OPTION_MD5;

		remaining -= TCPOLEN_MD5SIG_ALIGNED;
@@ -906,8 +905,11 @@ static unsigned int tcp_synack_options(const struct sock *sk, 
		 */

		if (synack_type != TCP_SYNACK_COOKIE)

			ireq->tstamp_ok &= !ireq->sack_ok;

	} else if (tcp_key_is_ao(key)) {

		opts->options |= OPTION_AO;

		remaining -= tcp_ao_len(key->ao_key);

		ireq->tstamp_ok &= !ireq->sack_ok;

	}

#endif



	/* We always send an MSS option. */

	opts->mss = mss;
@@ -3653,7 +3655,6 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, 
{

	struct inet_request_sock *ireq = inet_rsk(req);

	const struct tcp_sock *tp = tcp_sk(sk);

	struct tcp_md5sig_key *md5 = NULL;

	struct tcp_out_options opts;

	struct tcp_key key = {};

	struct sk_buff *skb;
@@ -3707,18 +3708,48 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, 
			tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);

	}



#ifdef CONFIG_TCP_MD5SIG

#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)

	rcu_read_lock();

	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));

	if (md5)

#endif

	if (tcp_rsk_used_ao(req)) {

#ifdef CONFIG_TCP_AO

		struct tcp_ao_key *ao_key = NULL;

		u8 maclen = tcp_rsk(req)->maclen;

		u8 keyid = tcp_rsk(req)->ao_keyid;



		ao_key = tcp_sk(sk)->af_specific->ao_lookup(sk, req_to_sk(req),

							    keyid, -1);

		/* If there is no matching key - avoid sending anything,

		 * especially usigned segments. It could try harder and lookup

		 * for another peer-matching key, but the peer has requested

		 * ao_keyid (RFC5925 RNextKeyID), so let's keep it simple here.

		 */

		if (unlikely(!ao_key || tcp_ao_maclen(ao_key) != maclen)) {

			u8 key_maclen = ao_key ? tcp_ao_maclen(ao_key) : 0;



			rcu_read_unlock();

			kfree_skb(skb);

			net_warn_ratelimited("TCP-AO: the keyid %u with maclen %u|%u from SYN packet is not present - not sending SYNACK\n",

					     keyid, maclen, key_maclen);

			return NULL;

		}

		key.ao_key = ao_key;

		key.type = TCP_KEY_AO;

#endif

	} else {

#ifdef CONFIG_TCP_MD5SIG

		key.md5_key = tcp_rsk(req)->af_specific->req_md5_lookup(sk,

					req_to_sk(req));

		if (key.md5_key)

			key.type = TCP_KEY_MD5;

#endif

	}

	skb_set_hash(skb, READ_ONCE(tcp_rsk(req)->txhash), PKT_HASH_TYPE_L4);

	/* bpf program will be interested in the tcp_flags */

	TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK;

	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,

					     foc, synack_type,

					     syn_skb) + sizeof(*th);

	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts,

					     &key, foc, synack_type, syn_skb)

					+ sizeof(*th);



	skb_push(skb, tcp_header_size);

	skb_reset_transport_header(skb);
@@ -3738,15 +3769,24 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, 


	/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */

	th->window = htons(min(req->rsk_rcv_wnd, 65535U));

	tcp_options_write(th, NULL, NULL, &opts, &key);

	tcp_options_write(th, NULL, tcp_rsk(req), &opts, &key);

	th->doff = (tcp_header_size >> 2);

	TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);



#ifdef CONFIG_TCP_MD5SIG

	/* Okay, we have all we need - do the md5 hash if needed */

	if (md5)

	if (tcp_key_is_md5(&key)) {

#ifdef CONFIG_TCP_MD5SIG

		tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,

					       md5, req_to_sk(req), skb);

					key.md5_key, req_to_sk(req), skb);

#endif

	} else if (tcp_key_is_ao(&key)) {

#ifdef CONFIG_TCP_AO

		tcp_rsk(req)->af_specific->ao_synack_hash(opts.hash_location,

					key.ao_key, req, skb,

					opts.hash_location - (u8 *)th, 0);

#endif

	}

#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)

	rcu_read_unlock();

#endif