net/tcp: Add AO sign to RST packets

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

include/net/tcp.h

@@ -2258,7 +2258,12 @@ static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
 
 struct tcp_key {
 	union {
-		struct tcp_ao_key *ao_key;
+		struct {
+			struct tcp_ao_key *ao_key;
+			char *traffic_key;
+			u32 sne;
+			u8 rcv_next;
+		};
 		struct tcp_md5sig_key *md5_key;
 	};
 	enum {

include/net/tcp_ao.h

@@ -120,12 +120,24 @@ 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,
+			 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,

net/ipv4/tcp_ao.c

@@ -48,8 +48,8 @@ int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
  * it's known that the keys in ao_info are matching peer's
  * family/address/VRF/etc.
  */
-static struct tcp_ao_key *tcp_ao_established_key(struct tcp_ao_info *ao,
-						 int sndid, int rcvid)
+struct tcp_ao_key *tcp_ao_established_key(struct tcp_ao_info *ao,
+					  int sndid, int rcvid)
 {
 	struct tcp_ao_key *key;
 
@@ -369,6 +369,66 @@ static int tcp_ao_hash_header(struct tcp_sigpool *hp,
 	return err;
 }
 
+int tcp_ao_hash_hdr(unsigned short int 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 tkey_len = tcp_ao_digest_size(key);
+	int hash_offset = ao_hash - (char *)th;
+	struct tcp_sigpool hp;
+	void *hash_buf = NULL;
+
+	hash_buf = kmalloc(tkey_len, GFP_ATOMIC);
+	if (!hash_buf)
+		goto clear_hash_noput;
+
+	if (tcp_sigpool_start(key->tcp_sigpool_id, &hp))
+		goto clear_hash_noput;
+
+	if (crypto_ahash_setkey(crypto_ahash_reqtfm(hp.req), tkey, tkey_len))
+		goto clear_hash;
+
+	if (crypto_ahash_init(hp.req))
+		goto clear_hash;
+
+	if (tcp_ao_hash_sne(&hp, sne))
+		goto clear_hash;
+	if (family == AF_INET) {
+		if (tcp_v4_ao_hash_pseudoheader(&hp, daddr->a4.s_addr,
+						saddr->a4.s_addr, th->doff * 4))
+			goto clear_hash;
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (family == AF_INET6) {
+		if (tcp_v6_ao_hash_pseudoheader(&hp, &daddr->a6,
+						&saddr->a6, th->doff * 4))
+			goto clear_hash;
+#endif
+	} else {
+		WARN_ON_ONCE(1);
+		goto clear_hash;
+	}
+	if (tcp_ao_hash_header(&hp, th, false,
+			       ao_hash, hash_offset, tcp_ao_maclen(key)))
+		goto clear_hash;
+	ahash_request_set_crypt(hp.req, NULL, hash_buf, 0);
+	if (crypto_ahash_final(hp.req))
+		goto clear_hash;
+
+	memcpy(ao_hash, hash_buf, tcp_ao_maclen(key));
+	tcp_sigpool_end(&hp);
+	kfree(hash_buf);
+	return 0;
+
+clear_hash:
+	tcp_sigpool_end(&hp);
+clear_hash_noput:
+	memset(ao_hash, 0, tcp_ao_maclen(key));
+	kfree(hash_buf);
+	return 1;
+}
+
 int tcp_ao_hash_skb(unsigned short int family,
 		    char *ao_hash, struct tcp_ao_key *key,
 		    const struct sock *sk, const struct sk_buff *skb,
@@ -435,6 +495,44 @@ 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,
+			 struct tcp_ao_key **key, char **traffic_key,
+			 bool *allocated_traffic_key, u8 *keyid, u32 *sne)
+{
+	struct tcp_ao_key *rnext_key;
+	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 | TCPF_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;
+}
+
 int tcp_ao_transmit_skb(struct sock *sk, struct sk_buff *skb,
 			struct tcp_ao_key *key, struct tcphdr *th,
 			__u8 *hash_location)

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,
+				 &key, &traffic_key, &allocated_traffic_key,
+				 &keyid, &ao_sne))
+		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.
  *
@@ -670,28 +716,21 @@ EXPORT_SYMBOL(tcp_v4_send_check);
  *	Exception: precedence violation. We do not implement it in any case.
  */
 
-#ifdef CONFIG_TCP_AO
-#define OPTION_BYTES MAX_TCP_OPTION_SPACE
-#elif defined(CONFIG_TCP_MD5SIG)
-#define OPTION_BYTES TCPOLEN_MD5SIG_ALIGNED
-#else
-#define OPTION_BYTES sizeof(__be32)
-#endif
-
 static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
 {
 	const struct tcphdr *th = tcp_hdr(skb);
 	struct {
 		struct tcphdr th;
-		__be32 opt[OPTION_BYTES / sizeof(__be32)];
+		__be32 opt[REPLY_OPTIONS_LEN];
 	} rep;
+	const __u8 *md5_hash_location = NULL;
+	const struct tcp_ao_hdr *aoh;
 	struct ip_reply_arg arg;
 #ifdef CONFIG_TCP_MD5SIG
-	const __u8 *md5_hash_location = NULL;
 	struct tcp_md5sig_key *key = NULL;
 	unsigned char newhash[16];
-	int genhash;
 	struct sock *sk1 = NULL;
+	int genhash;
 #endif
 	u64 transmit_time = 0;
 	struct sock *ctl_sk;
@@ -728,11 +767,15 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
 	arg.iov[0].iov_len  = sizeof(rep.th);
 
 	net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
-#ifdef CONFIG_TCP_MD5SIG
+
 	/* Invalid TCP option size or twice included auth */
-	if (tcp_parse_auth_options(tcp_hdr(skb), &md5_hash_location, NULL))
+	if (tcp_parse_auth_options(tcp_hdr(skb), &md5_hash_location, &aoh))
 		return;
 
+	if (aoh && tcp_v4_ao_sign_reset(sk, skb, aoh, &arg, &rep.th, rep.opt))
+		return;
+
+#ifdef CONFIG_TCP_MD5SIG
 	rcu_read_lock();
 	if (sk && sk_fullsock(sk)) {
 		const union tcp_md5_addr *addr;