net/tcp: Calculate TCP-AO traffic keys

Add traffic key calculation the way it's described in RFC5926.
Wire it up to tcp_finish_connect() and cache the new keys straight away
on already established TCP connections.

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>

4 files changed, 211 insertions, 0 deletions

diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index ee23356101f4..e478341fc336 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -16,6 +16,34 @@
 #include <net/tcp.h>
 #include <net/ipv6.h>
 
+int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
+			    unsigned int len, struct tcp_sigpool *hp)
+{
+	struct scatterlist sg;
+	int ret;
+
+	if (crypto_ahash_setkey(crypto_ahash_reqtfm(hp->req),
+				mkt->key, mkt->keylen))
+		goto clear_hash;
+
+	ret = crypto_ahash_init(hp->req);
+	if (ret)
+		goto clear_hash;
+
+	sg_init_one(&sg, ctx, len);
+	ahash_request_set_crypt(hp->req, &sg, key, len);
+	crypto_ahash_update(hp->req);
+
+	ret = crypto_ahash_final(hp->req);
+	if (ret)
+		goto clear_hash;
+
+	return 0;
+clear_hash:
+	memset(key, 0, tcp_ao_digest_size(mkt));
+	return 1;
+}
+
 /* Optimized version of tcp_ao_do_lookup(): only for sockets for which
  * it's known that the keys in ao_info are matching peer's
  * family/address/VRF/etc.
@@ -169,6 +197,71 @@ void tcp_ao_destroy_sock(struct sock *sk)
 	kfree_rcu(ao, rcu);
 }
 
+/* 4 tuple and ISNs are expected in NBO */
+static int tcp_v4_ao_calc_key(struct tcp_ao_key *mkt, u8 *key,
+			      __be32 saddr, __be32 daddr,
+			      __be16 sport, __be16 dport,
+			      __be32 sisn,  __be32 disn)
+{
+	/* See RFC5926 3.1.1 */
+	struct kdf_input_block {
+		u8                      counter;
+		u8                      label[6];
+		struct tcp4_ao_context	ctx;
+		__be16                  outlen;
+	} __packed * tmp;
+	struct tcp_sigpool hp;
+	int err;
+
+	err = tcp_sigpool_start(mkt->tcp_sigpool_id, &hp);
+	if (err)
+		return err;
+
+	tmp = hp.scratch;
+	tmp->counter	= 1;
+	memcpy(tmp->label, "TCP-AO", 6);
+	tmp->ctx.saddr	= saddr;
+	tmp->ctx.daddr	= daddr;
+	tmp->ctx.sport	= sport;
+	tmp->ctx.dport	= dport;
+	tmp->ctx.sisn	= sisn;
+	tmp->ctx.disn	= disn;
+	tmp->outlen	= htons(tcp_ao_digest_size(mkt) * 8); /* in bits */
+
+	err = tcp_ao_calc_traffic_key(mkt, key, tmp, sizeof(*tmp), &hp);
+	tcp_sigpool_end(&hp);
+
+	return err;
+}
+
+int tcp_v4_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
+			  const struct sock *sk,
+			  __be32 sisn, __be32 disn, bool send)
+{
+	if (send)
+		return tcp_v4_ao_calc_key(mkt, key, sk->sk_rcv_saddr,
+					  sk->sk_daddr, htons(sk->sk_num),
+					  sk->sk_dport, sisn, disn);
+	else
+		return tcp_v4_ao_calc_key(mkt, key, sk->sk_daddr,
+					  sk->sk_rcv_saddr, sk->sk_dport,
+					  htons(sk->sk_num), disn, sisn);
+}
+
+static int tcp_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
+			      const struct sock *sk,
+			      __be32 sisn, __be32 disn, bool send)
+{
+	if (mkt->family == AF_INET)
+		return tcp_v4_ao_calc_key_sk(mkt, key, sk, sisn, disn, send);
+#if IS_ENABLED(CONFIG_IPV6)
+	else if (mkt->family == AF_INET6)
+		return tcp_v6_ao_calc_key_sk(mkt, key, sk, sisn, disn, send);
+#endif
+	else
+		return -EOPNOTSUPP;
+}
+
 struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
 				    int sndid, int rcvid)
 {
@@ -177,6 +270,113 @@ 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);
 }
 
+static int tcp_ao_cache_traffic_keys(const struct sock *sk,
+				     struct tcp_ao_info *ao,
+				     struct tcp_ao_key *ao_key)
+{
+	u8 *traffic_key = snd_other_key(ao_key);
+	int ret;
+
+	ret = tcp_ao_calc_key_sk(ao_key, traffic_key, sk,
+				 ao->lisn, ao->risn, true);
+	if (ret)
+		return ret;
+
+	traffic_key = rcv_other_key(ao_key);
+	ret = tcp_ao_calc_key_sk(ao_key, traffic_key, sk,
+				 ao->lisn, ao->risn, false);
+	return ret;
+}
+
+void tcp_ao_connect_init(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcp_ao_info *ao_info;
+	union tcp_ao_addr *addr;
+	struct tcp_ao_key *key;
+	int family;
+
+	ao_info = rcu_dereference_protected(tp->ao_info,
+					    lockdep_sock_is_held(sk));
+	if (!ao_info)
+		return;
+
+	/* Remove all keys that don't match the peer */
+	family = sk->sk_family;
+	if (family == AF_INET)
+		addr = (union tcp_ao_addr *)&sk->sk_daddr;
+#if IS_ENABLED(CONFIG_IPV6)
+	else if (family == AF_INET6)
+		addr = (union tcp_ao_addr *)&sk->sk_v6_daddr;
+#endif
+	else
+		return;
+
+	hlist_for_each_entry_rcu(key, &ao_info->head, node) {
+		if (!tcp_ao_key_cmp(key, addr, key->prefixlen, family, -1, -1))
+			continue;
+
+		if (key == ao_info->current_key)
+			ao_info->current_key = NULL;
+		if (key == ao_info->rnext_key)
+			ao_info->rnext_key = NULL;
+		hlist_del_rcu(&key->node);
+		atomic_sub(tcp_ao_sizeof_key(key), &sk->sk_omem_alloc);
+		call_rcu(&key->rcu, tcp_ao_key_free_rcu);
+	}
+
+	key = tp->af_specific->ao_lookup(sk, sk, -1, -1);
+	if (key) {
+		/* if current_key or rnext_key were not provided,
+		 * use the first key matching the peer
+		 */
+		if (!ao_info->current_key)
+			ao_info->current_key = key;
+		if (!ao_info->rnext_key)
+			ao_info->rnext_key = key;
+		tp->tcp_header_len += tcp_ao_len(key);
+
+		ao_info->lisn = htonl(tp->write_seq);
+	} else {
+		/* Can't happen: tcp_connect() verifies that there's
+		 * at least one tcp-ao key that matches the remote peer.
+		 */
+		WARN_ON_ONCE(1);
+		rcu_assign_pointer(tp->ao_info, NULL);
+		kfree(ao_info);
+	}
+}
+
+void tcp_ao_established(struct sock *sk)
+{
+	struct tcp_ao_info *ao;
+	struct tcp_ao_key *key;
+
+	ao = rcu_dereference_protected(tcp_sk(sk)->ao_info,
+				       lockdep_sock_is_held(sk));
+	if (!ao)
+		return;
+
+	hlist_for_each_entry_rcu(key, &ao->head, node)
+		tcp_ao_cache_traffic_keys(sk, ao, key);
+}
+
+void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_ao_info *ao;
+	struct tcp_ao_key *key;
+
+	ao = rcu_dereference_protected(tcp_sk(sk)->ao_info,
+				       lockdep_sock_is_held(sk));
+	if (!ao)
+		return;
+
+	WRITE_ONCE(ao->risn, tcp_hdr(skb)->seq);
+
+	hlist_for_each_entry_rcu(key, &ao->head, node)
+		tcp_ao_cache_traffic_keys(sk, ao, key);
+}
+
 static bool tcp_ao_can_set_current_rnext(struct sock *sk)
 {
 	/* There aren't current/rnext keys on TCP_LISTEN sockets */
@@ -558,6 +758,12 @@ static int tcp_ao_add_cmd(struct sock *sk, unsigned short int family,
 	if (ret < 0)
 		goto err_free_sock;
 
+	/* Change this condition if we allow adding keys in states
+	 * like close_wait, syn_sent or fin_wait...
+	 */
+	if (sk->sk_state == TCP_ESTABLISHED)
+		tcp_ao_cache_traffic_keys(sk, ao_info, key);
+
 	tcp_ao_link_mkt(ao_info, key);
 	if (first) {
 		sk_gso_disable(sk);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 00d04ab68958..6ee0342b5338 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6151,6 +6151,7 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
+	tcp_ao_finish_connect(sk, skb);
 	tcp_set_state(sk, TCP_ESTABLISHED);
 	icsk->icsk_ack.lrcvtime = tcp_jiffies32;
 
@@ -6648,6 +6649,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 					  skb);
 			WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
 		}
+		tcp_ao_established(sk);
 		smp_mb();
 		tcp_set_state(sk, TCP_ESTABLISHED);
 		sk->sk_state_change(sk);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 698e58a3ccec..3c73b5829377 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2288,6 +2288,7 @@ static const struct tcp_sock_af_ops tcp_sock_ipv4_specific = {
 #ifdef CONFIG_TCP_AO
 	.ao_lookup		= tcp_v4_ao_lookup,
 	.ao_parse		= tcp_v4_parse_ao,
+	.ao_calc_key_sk		= tcp_v4_ao_calc_key_sk,
 #endif
 };
 #endif
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 1b90107f7038..9fbf1b2e2025 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3749,6 +3749,8 @@ static void tcp_connect_init(struct sock *sk)
 	if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps))
 		tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;
 
+	tcp_ao_connect_init(sk);
+
 	/* If user gave his TCP_MAXSEG, record it to clamp */
 	if (tp->rx_opt.user_mss)
 		tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;