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net/tcp: Add TCP-AO SNE support

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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 <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>
This commit is contained in:
Dmitry Safonov 2023-10-23 20:22:06 +01:00 committed by David S. Miller
parent af09a341dc
commit 64382c71a5
6 changed files with 104 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
include/net/tcp_ao.h
View File

@ -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);

46
net/ipv4/tcp_ao.c
View File

@ -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);

28
net/ipv4/tcp_input.c
View File

@ -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) {

3
net/ipv4/tcp_ipv4.c
View File

@ -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;

15
net/ipv4/tcp_minisocks.c
View File

@ -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;

3
net/ipv6/tcp_ipv6.c
View File

@ -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) {