[PATCH v2 10/35] net/tcp: Calculate TCP-AO traffic keys

Dmitry Safonov
2022-09-23T20:14:40Z

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>
---
include/net/tcp.h | 5 ++
include/net/tcp_ao.h | 44 ++++++++++-
net/ipv4/tcp_ao.c | 180 ++++++++++++++++++++++++++++++++++++++++++
net/ipv4/tcp_input.c | 1 +
net/ipv4/tcp_ipv4.c | 1 +
net/ipv4/tcp_output.c | 1 +
net/ipv6/tcp_ao.c | 40 ++++++++++
net/ipv6/tcp_ipv6.c | 1 +
8 files changed, 272 insertions(+), 1 deletion(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 9c71f48cc99c..e140ae4fe653 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2078,6 +2078,11 @@ struct tcp_sock_af_ops {
struct tcp_ao_key *(*ao_lookup)(const struct sock *sk,
struct sock *addr_sk,
int sndid, int rcvid);
+ int (*ao_calc_key_sk)(struct tcp_ao_key *mkt,
+ u8 *key,
+ const struct sock *sk,
+ __be32 sisn, __be32 disn,
+ bool send);
#endif
};

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index c550f1a6f5fd..f83a4d09a4ce 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -88,9 +88,33 @@ struct tcp_ao_info {
};

#ifdef CONFIG_TCP_AO
+/* TCP-AO structures and functions */
+
+struct tcp4_ao_context {
+ __be32 saddr;
+ __be32 daddr;
+ __be16 sport;
+ __be16 dport;
+ __be32 sisn;
+ __be32 disn;
+};
+
+struct tcp6_ao_context {
+ struct in6_addr saddr;
+ struct in6_addr daddr;
+ __be16 sport;
+ __be16 dport;
+ __be32 sisn;
+ __be32 disn;
+};
+
int tcp_parse_ao(struct sock *sk, int cmd, unsigned short int family,
sockptr_t optval, int optlen);
+int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
+ unsigned int len);
void tcp_ao_destroy_sock(struct sock *sk);
+int tcp_ao_cache_traffic_keys(const struct sock *sk, struct tcp_ao_info *ao,
+ struct tcp_ao_key *ao_key);
struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
const union tcp_ao_addr *addr,
int family, int sndid, int rcvid, u16 port);
@@ -98,13 +122,23 @@ struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
int tcp_v4_parse_ao(struct sock *sk, int optname, sockptr_t optval, int optlen);
struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
int sndid, int rcvid);
+int tcp_v4_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
+ const struct sock *sk,
+ __be32 sisn, __be32 disn, bool send);
/* ipv6 specific functions */
+int tcp_v6_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
+ const struct sock *sk, __be32 sisn,
+ __be32 disn, bool send);
struct tcp_ao_key *tcp_v6_ao_lookup(const struct sock *sk,
struct sock *addr_sk,
int sndid, int rcvid);
int tcp_v6_parse_ao(struct sock *sk, int cmd,
sockptr_t optval, int optlen);
-#else
+void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb);
+void tcp_ao_connect_init(struct sock *sk);
+
+#else /* CONFIG_TCP_AO */
+
static inline struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
const union tcp_ao_addr *addr,
int family, int sndid, int rcvid, u16 port)
@@ -115,6 +149,14 @@ static inline struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
static inline void tcp_ao_destroy_sock(struct sock *sk)
{
}
+
+static inline void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb)
+{
+}
+
+static inline void tcp_ao_connect_init(struct sock *sk)
+{
+}
#endif

#endif /* _TCP_AO_H */
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 2e90b5a7b941..841f5db7393b 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -16,6 +16,42 @@
#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 crypto_pool_ahash hp;
+ struct scatterlist sg;
+ int ret;
+
+ if (crypto_pool_get(mkt->crypto_pool_id, (struct crypto_pool *)&hp))
+ goto clear_hash_noput;
+
+ 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);
+
+ /* TODO: Revisit on how to get different output length */
+ ret = crypto_ahash_final(hp.req);
+ if (ret)
+ goto clear_hash;
+
+ crypto_pool_put();
+ return 0;
+clear_hash:
+ crypto_pool_put();
+clear_hash_noput:
+ memset(key, 0, tcp_ao_digest_size(mkt));
+ return 1;
+}
+
static struct tcp_ao_key *tcp_ao_do_lookup_rcvid(struct sock *sk, u8 keyid)
{
struct tcp_sock *tp = tcp_sk(sk);
@@ -181,6 +217,47 @@ 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;
+
+ 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 */
+
+ return tcp_ao_calc_traffic_key(mkt, key, &tmp, sizeof(tmp));
+}
+
+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);
+}
+
struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
int sndid, int rcvid)
{
@@ -189,6 +266,103 @@ 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, 0);
}

+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_sk(sk)->af_specific->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);
+ return tcp_sk(sk)->af_specific->ao_calc_key_sk(ao_key, traffic_key, sk,
+ ao->lisn, ao->risn,
+ false);
+}
+
+void tcp_ao_connect_init(struct sock *sk)
+{
+ struct tcp_ao_info *ao_info;
+ struct tcp_ao_key *key;
+ struct tcp_sock *tp = tcp_sk(sk);
+ union tcp_ao_addr *addr;
+ 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, sk->sk_dport) == 0)
+ 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);
+ crypto_pool_release(key->crypto_pool_id);
+ atomic_sub(tcp_ao_sizeof_key(key), &sk->sk_omem_alloc);
+ kfree_rcu(key, 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);
+ ao_info->snd_sne = 0;
+ ao_info->snd_sne_seq = tp->write_seq;
+ } else {
+ WARN_ON_ONCE(1);
+ rcu_assign_pointer(tp->ao_info, NULL);
+ kfree(ao_info);
+ }
+}
+
+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;
+
+ ao->risn = tcp_hdr(skb)->seq;
+
+ ao->rcv_sne = 0;
+ ao->rcv_sne_seq = ntohl(tcp_hdr(skb)->seq);
+
+ hlist_for_each_entry_rcu(key, &ao->head, node) {
+ tcp_ao_cache_traffic_keys(sk, ao, key);
+ }
+}
+
static int tcp_ao_current_rnext(struct sock *sk, u16 tcpa_flags,
u8 tcpa_sndid, u8 tcpa_rcvid)
{
@@ -681,6 +855,12 @@ 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 bc2ea12221f9..ad9ced317768 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6051,6 +6051,7 @@ 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;

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index f3d183be2595..e05bdad361c3 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2251,6 +2251,7 @@ 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 4b9ffd6b901d..23069a34dd47 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3661,6 +3661,7 @@ static void tcp_connect_init(struct sock *sk)
if (tp->af_specific->md5_lookup(sk, sk))
tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
#endif
+ tcp_ao_connect_init(sk);

/* If user gave his TCP_MAXSEG, record it to clamp */
if (tp->rx_opt.user_mss)
diff --git a/net/ipv6/tcp_ao.c b/net/ipv6/tcp_ao.c
index 221b8adb4f73..888ee6242334 100644
--- a/net/ipv6/tcp_ao.c
+++ b/net/ipv6/tcp_ao.c
@@ -13,6 +13,46 @@
#include <net/tcp.h>
#include <net/ipv6.h>

+int tcp_v6_ao_calc_key(struct tcp_ao_key *mkt, u8 *key,
+ const struct in6_addr *saddr,
+ const struct in6_addr *daddr,
+ __be16 sport, __be16 dport,
+ __be32 sisn, __be32 disn)
+{
+ struct kdf_input_block {
+ u8 counter;
+ u8 label[6];
+ struct tcp6_ao_context ctx;
+ __be16 outlen;
+ } __packed tmp;
+
+ 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 */
+
+ return tcp_ao_calc_traffic_key(mkt, key, &tmp, sizeof(tmp));
+}
+
+int tcp_v6_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_v6_ao_calc_key(mkt, key, &sk->sk_v6_rcv_saddr,
+ &sk->sk_v6_daddr, htons(sk->sk_num),
+ sk->sk_dport, sisn, disn);
+ else
+ return tcp_v6_ao_calc_key(mkt, key, &sk->sk_v6_daddr,
+ &sk->sk_v6_rcv_saddr, sk->sk_dport,
+ htons(sk->sk_num), disn, sisn);
+}
+
struct tcp_ao_key *tcp_v6_ao_do_lookup(const struct sock *sk,
const struct in6_addr *addr,
int sndid, int rcvid)
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index f5780a3fbd1b..c6d2389030f2 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1905,6 +1905,7 @@ static const struct tcp_sock_af_ops tcp_sock_ipv6_specific = {
#ifdef CONFIG_TCP_AO
.ao_lookup = tcp_v6_ao_lookup,
.ao_parse = tcp_v6_parse_ao,
+ .ao_calc_key_sk = tcp_v6_ao_calc_key_sk,
#endif
};
#endif
--
2.37.2