net/tcp: Introduce TCP_AO setsockopt()s

Add 3 setsockopt()s:
1. TCP_AO_ADD_KEY to add a new Master Key Tuple (MKT) on a socket
2. TCP_AO_DEL_KEY to delete present MKT from a socket
3. TCP_AO_INFO to change flags, Current_key/RNext_key on a TCP-AO sk

Userspace has to introduce keys on every socket it wants to use TCP-AO
option on, similarly to TCP_MD5SIG/TCP_MD5SIG_EXT.
RFC5925 prohibits definition of MKTs that would match the same peer,
so do sanity checks on the data provided by userspace. Be as
conservative as possible, including refusal of defining MKT on
an established connection with no AO, removing the key in-use and etc.

(1) and (2) are to be used by userspace key manager to add/remove keys.
(3) main purpose is to set RNext_key, which (as prescribed by RFC5925)
is the KeyID that will be requested in TCP-AO header from the peer to
sign their segments with.

At this moment the life of ao_info ends in tcp_v4_destroy_sock().

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>

3 files changed, 44 insertions, 15 deletions

diff --git a/net/ipv6/Makefile b/net/ipv6/Makefile
index 3036a45e8a1e..d283c59df4c1 100644
--- a/net/ipv6/Makefile
+++ b/net/ipv6/Makefile
@@ -52,4 +52,5 @@ obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o
 ifneq ($(CONFIG_IPV6),)
 obj-$(CONFIG_NET_UDP_TUNNEL) += ip6_udp_tunnel.o
 obj-y += mcast_snoop.o
+obj-$(CONFIG_TCP_AO) += tcp_ao.o
 endif
diff --git a/net/ipv6/tcp_ao.c b/net/ipv6/tcp_ao.c
new file mode 100644
index 000000000000..049ddbabe049
--- /dev/null
+++ b/net/ipv6/tcp_ao.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * INET		An implementation of the TCP Authentication Option (TCP-AO).
+ *		See RFC5925.
+ *
+ * Authors:	Dmitry Safonov <dima@arista.com>
+ *		Francesco Ruggeri <fruggeri@arista.com>
+ *		Salam Noureddine <noureddine@arista.com>
+ */
+#include <linux/tcp.h>
+
+#include <net/tcp.h>
+#include <net/ipv6.h>
+
+int tcp_v6_parse_ao(struct sock *sk, int cmd,
+		    sockptr_t optval, int optlen)
+{
+	return tcp_parse_ao(sk, cmd, AF_INET6, optval, optlen);
+}
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index ee53dad20a59..30bd17d03239 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -76,16 +76,9 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb);
 
 static const struct inet_connection_sock_af_ops ipv6_mapped;
 const struct inet_connection_sock_af_ops ipv6_specific;
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
 static const struct tcp_sock_af_ops tcp_sock_ipv6_specific;
 static const struct tcp_sock_af_ops tcp_sock_ipv6_mapped_specific;
-#else
-static struct tcp_md5sig_key *tcp_v6_md5_do_lookup(const struct sock *sk,
-						   const struct in6_addr *addr,
-						   int l3index)
-{
-	return NULL;
-}
 #endif
 
 /* Helper returning the inet6 address from a given tcp socket.
@@ -239,7 +232,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 		if (sk_is_mptcp(sk))
 			mptcpv6_handle_mapped(sk, true);
 		sk->sk_backlog_rcv = tcp_v4_do_rcv;
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
 		tp->af_specific = &tcp_sock_ipv6_mapped_specific;
 #endif
 
@@ -252,7 +245,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 			if (sk_is_mptcp(sk))
 				mptcpv6_handle_mapped(sk, false);
 			sk->sk_backlog_rcv = tcp_v6_do_rcv;
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
 			tp->af_specific = &tcp_sock_ipv6_specific;
 #endif
 			goto failure;
@@ -769,7 +762,13 @@ clear_hash_nostart:
 	memset(md5_hash, 0, 16);
 	return 1;
 }
-
+#else /* CONFIG_TCP_MD5SIG */
+static struct tcp_md5sig_key *tcp_v6_md5_do_lookup(const struct sock *sk,
+						   const struct in6_addr *addr,
+						   int l3index)
+{
+	return NULL;
+}
 #endif
 
 static void tcp_v6_init_req(struct request_sock *req,
@@ -1228,7 +1227,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
 		if (sk_is_mptcp(newsk))
 			mptcpv6_handle_mapped(newsk, true);
 		newsk->sk_backlog_rcv = tcp_v4_do_rcv;
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
 		newtp->af_specific = &tcp_sock_ipv6_mapped_specific;
 #endif
 
@@ -1896,11 +1895,16 @@ const struct inet_connection_sock_af_ops ipv6_specific = {
 	.mtu_reduced	   = tcp_v6_mtu_reduced,
 };
 
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
 static const struct tcp_sock_af_ops tcp_sock_ipv6_specific = {
+#ifdef CONFIG_TCP_MD5SIG
 	.md5_lookup	=	tcp_v6_md5_lookup,
 	.calc_md5_hash	=	tcp_v6_md5_hash_skb,
 	.md5_parse	=	tcp_v6_parse_md5_keys,
+#endif
+#ifdef CONFIG_TCP_AO
+	.ao_parse	=	tcp_v6_parse_ao,
+#endif
 };
 #endif
 
@@ -1922,11 +1926,16 @@ static const struct inet_connection_sock_af_ops ipv6_mapped = {
 	.mtu_reduced	   = tcp_v4_mtu_reduced,
 };
 
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
 static const struct tcp_sock_af_ops tcp_sock_ipv6_mapped_specific = {
+#ifdef CONFIG_TCP_MD5SIG
 	.md5_lookup	=	tcp_v4_md5_lookup,
 	.calc_md5_hash	=	tcp_v4_md5_hash_skb,
 	.md5_parse	=	tcp_v6_parse_md5_keys,
+#endif
+#ifdef CONFIG_TCP_AO
+	.ao_parse	=	tcp_v6_parse_ao,
+#endif
 };
 #endif
 
@@ -1941,7 +1950,7 @@ static int tcp_v6_init_sock(struct sock *sk)
 
 	icsk->icsk_af_ops = &ipv6_specific;
 
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
 	tcp_sk(sk)->af_specific = &tcp_sock_ipv6_specific;
 #endif