net/tcp: Wire TCP-AO to request sockets

Now when the new request socket is created from the listening socket,
it's recorded what MKT was used by the peer. tcp_rsk_used_ao() is
a new helper for checking if TCP-AO option was used to create the
request socket.
tcp_ao_copy_all_matching() will copy all keys that match the peer on the
request socket, as well as preparing them for the usage (creating
traffic keys).

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 58 insertions, 8 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a78112d78d06..2bd56b57f3c9 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1072,13 +1072,47 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 	u32 seq = (sk->sk_state == TCP_LISTEN) ? tcp_rsk(req)->snt_isn + 1 :
 					     tcp_sk(sk)->snd_nxt;
 
-	/* RFC 7323 2.3
-	 * The window field (SEG.WND) of every outgoing segment, with the
-	 * exception of <SYN> segments, MUST be right-shifted by
-	 * Rcv.Wind.Shift bits:
-	 */
+#ifdef CONFIG_TCP_AO
+	if (tcp_rsk_used_ao(req)) {
+		const union tcp_md5_addr *addr;
+		const struct tcp_ao_hdr *aoh;
+
+		/* Invalid TCP option size or twice included auth */
+		if (tcp_parse_auth_options(tcp_hdr(skb), NULL, &aoh))
+			return;
+		if (!aoh)
+			return;
+
+		addr = (union tcp_md5_addr *)&ip_hdr(skb)->saddr;
+		key.ao_key = tcp_ao_do_lookup(sk, addr, AF_INET,
+					      aoh->rnext_keyid, -1);
+		if (unlikely(!key.ao_key)) {
+			/* Send ACK with any matching MKT for the peer */
+			key.ao_key = tcp_ao_do_lookup(sk, addr, AF_INET, -1, -1);
+			/* Matching key disappeared (user removed the key?)
+			 * let the handshake timeout.
+			 */
+			if (!key.ao_key) {
+				net_info_ratelimited("TCP-AO key for (%pI4, %d)->(%pI4, %d) suddenly disappeared, won't ACK new connection\n",
+						     addr,
+						     ntohs(tcp_hdr(skb)->source),
+						     &ip_hdr(skb)->daddr,
+						     ntohs(tcp_hdr(skb)->dest));
+				return;
+			}
+		}
+		key.traffic_key = kmalloc(tcp_ao_digest_size(key.ao_key), GFP_ATOMIC);
+		if (!key.traffic_key)
+			return;
+
+		key.type = TCP_KEY_AO;
+		key.rcv_next = aoh->keyid;
+		tcp_v4_ao_calc_key_rsk(key.ao_key, key.traffic_key, req);
+#else
+	if (0) {
+#endif
 #ifdef CONFIG_TCP_MD5SIG
-	if (static_branch_unlikely(&tcp_md5_needed.key)) {
+	} else if (static_branch_unlikely(&tcp_md5_needed.key)) {
 		const union tcp_md5_addr *addr;
 		int l3index;
 
@@ -1087,8 +1121,14 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 		key.md5_key = tcp_md5_do_lookup(sk, l3index, addr, AF_INET);
 		if (key.md5_key)
 			key.type = TCP_KEY_MD5;
-	}
 #endif
+	}
+
+	/* RFC 7323 2.3
+	 * The window field (SEG.WND) of every outgoing segment, with the
+	 * exception of <SYN> segments, MUST be right-shifted by
+	 * Rcv.Wind.Shift bits:
+	 */
 	tcp_v4_send_ack(sk, skb, seq,
 			tcp_rsk(req)->rcv_nxt,
 			req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
@@ -1098,6 +1138,8 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			inet_rsk(req)->no_srccheck ? IP_REPLY_ARG_NOSRCCHECK : 0,
 			ip_hdr(skb)->tos,
 			READ_ONCE(tcp_rsk(req)->txhash));
+	if (tcp_key_is_ao(&key))
+		kfree(key.traffic_key);
 }
 
 /*
@@ -1636,6 +1678,10 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
 	.req_md5_lookup	=	tcp_v4_md5_lookup,
 	.calc_md5_hash	=	tcp_v4_md5_hash_skb,
 #endif
+#ifdef CONFIG_TCP_AO
+	.ao_lookup	=	tcp_v4_ao_lookup_rsk,
+	.ao_calc_key	=	tcp_v4_ao_calc_key_rsk,
+#endif
 #ifdef CONFIG_SYN_COOKIES
 	.cookie_init_seq =	cookie_v4_init_sequence,
 #endif
@@ -1737,12 +1783,16 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
 	/* Copy over the MD5 key from the original socket */
 	addr = (union tcp_md5_addr *)&newinet->inet_daddr;
 	key = tcp_md5_do_lookup(sk, l3index, addr, AF_INET);
-	if (key) {
+	if (key && !tcp_rsk_used_ao(req)) {
 		if (tcp_md5_key_copy(newsk, addr, AF_INET, 32, l3index, key))
 			goto put_and_exit;
 		sk_gso_disable(newsk);
 	}
 #endif
+#ifdef CONFIG_TCP_AO
+	if (tcp_ao_copy_all_matching(sk, newsk, req, skb, AF_INET))
+		goto put_and_exit; /* OOM, release back memory */
+#endif
 
 	if (__inet_inherit_port(sk, newsk) < 0)
 		goto put_and_exit;