From 64382c71a5575741933dfdb0cf7162c6e9b8854e Mon Sep 17 00:00:00 2001 From: Dmitry Safonov Date: Mon, 23 Oct 2023 20:22:06 +0100 Subject: net/tcp: Add TCP-AO SNE support Add Sequence Number Extension (SNE) for TCP-AO. This is needed to protect long-living TCP-AO connections from replaying attacks after sequence number roll-over, see RFC5925 (6.2). Co-developed-by: Francesco Ruggeri Signed-off-by: Francesco Ruggeri Co-developed-by: Salam Noureddine Signed-off-by: Salam Noureddine Signed-off-by: Dmitry Safonov Acked-by: David Ahern Signed-off-by: David S. Miller --- include/net/tcp_ao.h | 22 +++++++++++++++++++++- net/ipv4/tcp_ao.c | 46 +++++++++++++++++++++++++++++++++++++--------- net/ipv4/tcp_input.c | 28 ++++++++++++++++++++++++++++ net/ipv4/tcp_ipv4.c | 3 ++- net/ipv4/tcp_minisocks.c | 15 ++++++++++++++- net/ipv6/tcp_ipv6.c | 3 ++- 6 files changed, 104 insertions(+), 13 deletions(-) diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h index cfb55bd9411b..0c3516d1b968 100644 --- a/include/net/tcp_ao.h +++ b/include/net/tcp_ao.h @@ -95,6 +95,25 @@ struct tcp_ao_info { __unused :31; __be32 lisn; __be32 risn; + /* Sequence Number Extension (SNE) are upper 4 bytes for SEQ, + * that protect TCP-AO connection from replayed old TCP segments. + * See RFC5925 (6.2). + * In order to get correct SNE, there's a helper tcp_ao_compute_sne(). + * It needs SEQ basis to understand whereabouts are lower SEQ numbers. + * According to that basis vector, it can provide incremented SNE + * when SEQ rolls over or provide decremented SNE when there's + * a retransmitted segment from before-rolling over. + * - for request sockets such basis is rcv_isn/snt_isn, which seems + * good enough as it's unexpected to receive 4 Gbytes on reqsk. + * - for full sockets the basis is rcv_nxt/snd_una. snd_una is + * taken instead of snd_nxt as currently it's easier to track + * in tcp_snd_una_update(), rather than updating SNE in all + * WRITE_ONCE(tp->snd_nxt, ...) + * - for time-wait sockets the basis is tw_rcv_nxt/tw_snd_nxt. + * tw_snd_nxt is not expected to change, while tw_rcv_nxt may. + */ + u32 snd_sne; + u32 rcv_sne; refcount_t refcnt; /* Protects twsk destruction */ struct rcu_head rcu; }; @@ -147,6 +166,7 @@ enum skb_drop_reason tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb, unsigned short int family, const struct request_sock *req, const struct tcp_ao_hdr *aoh); +u32 tcp_ao_compute_sne(u32 next_sne, u32 next_seq, u32 seq); struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk, const union tcp_ao_addr *addr, int family, int sndid, int rcvid); @@ -156,7 +176,7 @@ int tcp_ao_hash_hdr(unsigned short family, char *ao_hash, 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, + const struct tcp_ao_hdr *aoh, int l3index, u32 seq, struct tcp_ao_key **key, char **traffic_key, bool *allocated_traffic_key, u8 *keyid, u32 *sne); diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c index 1097e99a9ad6..7e14bcd4dfd4 100644 --- a/net/ipv4/tcp_ao.c +++ b/net/ipv4/tcp_ao.c @@ -401,6 +401,21 @@ static int tcp_ao_hash_pseudoheader(unsigned short int family, return -EAFNOSUPPORT; } +u32 tcp_ao_compute_sne(u32 next_sne, u32 next_seq, u32 seq) +{ + u32 sne = next_sne; + + if (before(seq, next_seq)) { + if (seq > next_seq) + sne--; + } else { + if (seq < next_seq) + sne++; + } + + return sne; +} + /* tcp_ao_hash_sne(struct tcp_sigpool *hp) * @hp - used for hashing * @sne - sne value @@ -611,7 +626,7 @@ struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk, } int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb, - const struct tcp_ao_hdr *aoh, int l3index, + const struct tcp_ao_hdr *aoh, int l3index, u32 seq, struct tcp_ao_key **key, char **traffic_key, bool *allocated_traffic_key, u8 *keyid, u32 *sne) { @@ -639,7 +654,7 @@ int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb, sisn = htonl(tcp_rsk(req)->rcv_isn); disn = htonl(tcp_rsk(req)->snt_isn); - *sne = 0; + *sne = tcp_ao_compute_sne(0, tcp_rsk(req)->snt_isn, seq); } else { sisn = th->seq; disn = 0; @@ -670,11 +685,15 @@ int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb, *keyid = (*key)->rcvid; } else { struct tcp_ao_key *rnext_key; + u32 snd_basis; - if (sk->sk_state == TCP_TIME_WAIT) + if (sk->sk_state == TCP_TIME_WAIT) { ao_info = rcu_dereference(tcp_twsk(sk)->ao_info); - else + snd_basis = tcp_twsk(sk)->tw_snd_nxt; + } else { ao_info = rcu_dereference(tcp_sk(sk)->ao_info); + snd_basis = tcp_sk(sk)->snd_una; + } if (!ao_info) return -ENOENT; @@ -684,7 +703,8 @@ int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb, *traffic_key = snd_other_key(*key); rnext_key = READ_ONCE(ao_info->rnext_key); *keyid = rnext_key->rcvid; - *sne = 0; + *sne = tcp_ao_compute_sne(READ_ONCE(ao_info->snd_sne), + snd_basis, seq); } return 0; } @@ -698,6 +718,7 @@ int tcp_ao_transmit_skb(struct sock *sk, struct sk_buff *skb, struct tcp_ao_info *ao; void *tkey_buf = NULL; u8 *traffic_key; + u32 sne; ao = rcu_dereference_protected(tcp_sk(sk)->ao_info, lockdep_sock_is_held(sk)); @@ -717,8 +738,10 @@ int tcp_ao_transmit_skb(struct sock *sk, struct sk_buff *skb, tp->af_specific->ao_calc_key_sk(key, traffic_key, sk, ao->lisn, disn, true); } + sne = tcp_ao_compute_sne(READ_ONCE(ao->snd_sne), READ_ONCE(tp->snd_una), + ntohl(th->seq)); tp->af_specific->calc_ao_hash(hash_location, key, sk, skb, traffic_key, - hash_location - (u8 *)th, 0); + hash_location - (u8 *)th, sne); kfree(tkey_buf); return 0; } @@ -846,7 +869,8 @@ tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb, if (unlikely(th->syn && !th->ack)) goto verify_hash; - sne = 0; + sne = tcp_ao_compute_sne(info->rcv_sne, tcp_sk(sk)->rcv_nxt, + ntohl(th->seq)); /* Established socket, traffic key are cached */ traffic_key = rcv_other_key(key); err = tcp_ao_verify_hash(sk, skb, family, info, aoh, key, @@ -881,14 +905,16 @@ tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb, if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_NEW_SYN_RECV)) { /* Make the initial syn the likely case here */ if (unlikely(req)) { - sne = 0; + sne = tcp_ao_compute_sne(0, tcp_rsk(req)->rcv_isn, + ntohl(th->seq)); sisn = htonl(tcp_rsk(req)->rcv_isn); disn = htonl(tcp_rsk(req)->snt_isn); } else if (unlikely(th->ack && !th->syn)) { /* Possible syncookie packet */ sisn = htonl(ntohl(th->seq) - 1); disn = htonl(ntohl(th->ack_seq) - 1); - sne = 0; + sne = tcp_ao_compute_sne(0, ntohl(sisn), + ntohl(th->seq)); } else if (unlikely(!th->syn)) { /* no way to figure out initial sisn/disn - drop */ return SKB_DROP_REASON_TCP_FLAGS; @@ -986,6 +1012,7 @@ void tcp_ao_connect_init(struct sock *sk) tp->tcp_header_len += tcp_ao_len(key); ao_info->lisn = htonl(tp->write_seq); + ao_info->snd_sne = 0; } else { /* Can't happen: tcp_connect() verifies that there's * at least one tcp-ao key that matches the remote peer. @@ -1021,6 +1048,7 @@ void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb) return; WRITE_ONCE(ao->risn, tcp_hdr(skb)->seq); + ao->rcv_sne = 0; hlist_for_each_entry_rcu(key, &ao->head, node) tcp_ao_cache_traffic_keys(sk, ao, key); diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index de64c0c2fb69..67ca72185f14 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3576,9 +3576,18 @@ static inline bool tcp_may_update_window(const struct tcp_sock *tp, static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack) { u32 delta = ack - tp->snd_una; +#ifdef CONFIG_TCP_AO + struct tcp_ao_info *ao; +#endif sock_owned_by_me((struct sock *)tp); tp->bytes_acked += delta; +#ifdef CONFIG_TCP_AO + ao = rcu_dereference_protected(tp->ao_info, + lockdep_sock_is_held((struct sock *)tp)); + if (ao && ack < tp->snd_una) + ao->snd_sne++; +#endif tp->snd_una = ack; } @@ -3586,9 +3595,18 @@ static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack) static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq) { u32 delta = seq - tp->rcv_nxt; +#ifdef CONFIG_TCP_AO + struct tcp_ao_info *ao; +#endif sock_owned_by_me((struct sock *)tp); tp->bytes_received += delta; +#ifdef CONFIG_TCP_AO + ao = rcu_dereference_protected(tp->ao_info, + lockdep_sock_is_held((struct sock *)tp)); + if (ao && seq < tp->rcv_nxt) + ao->rcv_sne++; +#endif WRITE_ONCE(tp->rcv_nxt, seq); } @@ -6456,6 +6474,16 @@ consume: * simultaneous connect with crossed SYNs. * Particularly, it can be connect to self. */ +#ifdef CONFIG_TCP_AO + struct tcp_ao_info *ao; + + ao = rcu_dereference_protected(tp->ao_info, + lockdep_sock_is_held(sk)); + if (ao) { + WRITE_ONCE(ao->risn, th->seq); + ao->rcv_sne = 0; + } +#endif tcp_set_state(sk, TCP_SYN_RECV); if (tp->rx_opt.saw_tstamp) { diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index ece95d5138e1..bdec99707028 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -676,7 +676,7 @@ static bool tcp_v4_ao_sign_reset(const struct sock *sk, struct sk_buff *skb, u8 keyid; rcu_read_lock(); - if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, + if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, ntohl(reply->seq), &key, &traffic_key, &allocated_traffic_key, &keyid, &ao_sne)) goto out; @@ -1034,6 +1034,7 @@ static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb) struct tcp_ao_key *rnext_key; key.traffic_key = snd_other_key(key.ao_key); + key.sne = READ_ONCE(ao_info->snd_sne); rnext_key = READ_ONCE(ao_info->rnext_key); key.rcv_next = rnext_key->rcvid; key.type = TCP_KEY_AO; diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 8d941a6e066b..a9807eeb311c 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -51,6 +51,18 @@ tcp_timewait_check_oow_rate_limit(struct inet_timewait_sock *tw, return TCP_TW_SUCCESS; } +static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq) +{ +#ifdef CONFIG_TCP_AO + struct tcp_ao_info *ao; + + ao = rcu_dereference(tcptw->ao_info); + if (unlikely(ao && seq < tcptw->tw_rcv_nxt)) + WRITE_ONCE(ao->rcv_sne, ao->rcv_sne + 1); +#endif + tcptw->tw_rcv_nxt = seq; +} + /* * * Main purpose of TIME-WAIT state is to close connection gracefully, * when one of ends sits in LAST-ACK or CLOSING retransmitting FIN @@ -136,7 +148,8 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, /* FIN arrived, enter true time-wait state. */ tw->tw_substate = TCP_TIME_WAIT; - tcptw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq; + twsk_rcv_nxt_update(tcptw, TCP_SKB_CB(skb)->end_seq); + if (tmp_opt.saw_tstamp) { tcptw->tw_ts_recent_stamp = ktime_get_seconds(); tcptw->tw_ts_recent = tmp_opt.rcv_tsval; diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index cc899caf348e..4dcbc13e9ec8 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1090,7 +1090,7 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb) int l3index; l3index = tcp_v6_sdif(skb) ? tcp_v6_iif_l3_slave(skb) : 0; - if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, + if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, seq, &key.ao_key, &key.traffic_key, &allocated_traffic_key, &key.rcv_next, &key.sne)) @@ -1167,6 +1167,7 @@ static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb) /* rcv_next switches to our rcv_next */ rnext_key = READ_ONCE(ao_info->rnext_key); key.rcv_next = rnext_key->rcvid; + key.sne = READ_ONCE(ao_info->snd_sne); key.type = TCP_KEY_AO; #else if (0) { -- cgit