[PATCH v2 13/35] net/tcp: Add AO sign to RST packets

From: Dmitry Safonov
Date: Fri Sep 23 2022 - 16:15:02 EST

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Wire up sending resets to TCP-AO hashing.

Co-developed-by: Francesco Ruggeri <fruggeri@xxxxxxxxxx>
Signed-off-by: Francesco Ruggeri <fruggeri@xxxxxxxxxx>
Co-developed-by: Salam Noureddine <noureddine@xxxxxxxxxx>
Signed-off-by: Salam Noureddine <noureddine@xxxxxxxxxx>
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
---
include/net/tcp_ao.h | 7 ++++
net/ipv4/tcp_ao.c | 53 ++++++++++++++++++++++++++++++
net/ipv4/tcp_ipv4.c | 48 ++++++++++++++++++++++++++-
net/ipv6/tcp_ipv6.c | 77 ++++++++++++++++++++++++++++++++++++++++++--
4 files changed, 181 insertions(+), 4 deletions(-)

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index b5516c83e489..35c33f7e9c27 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -117,6 +117,7 @@ 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_do_lookup_sndid(const struct sock *sk, u8 keyid);
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);
@@ -126,6 +127,12 @@ int tcp_ao_cache_traffic_keys(const struct sock *sk, struct tcp_ao_info *ao,
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);
+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);
+
/* ipv4 specific functions */
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,
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 74cbc13f62f4..1fd7d3499d7a 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -421,6 +421,59 @@ static int tcp_ao_hash_skb_data(struct crypto_pool_ahash *hp,
return 0;
}

+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)
+{
+ struct crypto_pool_ahash hp;
+ int tkey_len = tcp_ao_digest_size(key);
+ int hash_offset = ao_hash - (char *)th;
+
+ if (crypto_pool_get(key->crypto_pool_id, (struct crypto_pool *)&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, ao_hash, 0);
+ if (crypto_ahash_final(hp.req))
+ goto clear_hash;
+
+ crypto_pool_put();
+ return 0;
+
+clear_hash:
+ crypto_pool_put();
+clear_hash_noput:
+ memset(ao_hash, 0, tcp_ao_maclen(key));
+ return 1;
+}
+EXPORT_SYMBOL(tcp_ao_hash_hdr);
+
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,
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index b54a2017b84f..32cff30c4455 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -679,11 +679,17 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
#ifdef CONFIG_TCP_MD5SIG
struct tcp_md5sig_key *key = NULL;
const __u8 *md5_hash_location = NULL;
+ const struct tcp_ao_hdr *aoh;
unsigned char newhash[16];
int genhash;
struct sock *sk1 = NULL;
#endif
u64 transmit_time = 0;
+#ifdef CONFIG_TCP_AO
+ struct tcp_ao_key *ao_key = NULL;
+ char traffic_key[TCP_AO_MAX_HASH_SIZE] __tcp_ao_key_align;
+ u32 ao_sne;
+#endif
struct sock *ctl_sk;
struct net *net;

@@ -719,7 +725,7 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
/* 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;

rcu_read_lock();
@@ -785,6 +791,46 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
key, ip_hdr(skb)->saddr,
ip_hdr(skb)->daddr, &rep.th);
}
+#endif
+#ifdef CONFIG_TCP_AO
+ if (sk && aoh && sk->sk_state != TCP_LISTEN) {
+ /* lookup key based on peer address and rcv_next*/
+ ao_key = tcp_ao_do_lookup_sndid(sk, aoh->rnext_keyid);
+
+ if (ao_key) {
+ struct tcp_ao_info *ao_info;
+ u8 keyid;
+
+ ao_info = rcu_dereference(tcp_sk(sk)->ao_info);
+
+ /* XXX: optimize by using cached traffic key depending
+ * on socket state
+ */
+ tcp_v4_ao_calc_key_sk(ao_key, traffic_key, sk,
+ ao_info->lisn, ao_info->risn,
+ true);
+
+ /* rcv_next holds the rcv_next of the peer, make keyid
+ * hold our rcv_next
+ */
+ keyid = ao_info->rnext_key->rcvid;
+ ao_sne = tcp_ao_compute_sne(ao_info->snd_sne,
+ ao_info->snd_sne_seq,
+ ntohl(rep.th.seq));
+
+ rep.opt[0] = htonl((TCPOPT_AO << 24) |
+ (tcp_ao_len(ao_key) << 16) |
+ (aoh->rnext_keyid << 8) | keyid);
+ arg.iov[0].iov_len += round_up(tcp_ao_len(ao_key), 4);
+ rep.th.doff = arg.iov[0].iov_len / 4;
+
+ tcp_ao_hash_hdr(AF_INET, (char *)&rep.opt[1],
+ ao_key, traffic_key,
+ (union tcp_ao_addr *)&ip_hdr(skb)->saddr,
+ (union tcp_ao_addr *)&ip_hdr(skb)->daddr,
+ &rep.th, ao_sne);
+ }
+ }
#endif
/* Can't co-exist with TCPMD5, hence check rep.opt[0] */
if (rep.opt[0] == 0) {
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index ba968e856ca9..f5d339d5291a 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -847,7 +847,9 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops = {
static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32 seq,
u32 ack, u32 win, u32 tsval, u32 tsecr,
int oif, struct tcp_md5sig_key *key, int rst,
- u8 tclass, __be32 label, u32 priority)
+ u8 tclass, __be32 label, u32 priority,
+ struct tcp_ao_key *ao_key, char *tkey,
+ u8 rcv_next, u32 ao_sne)
{
const struct tcphdr *th = tcp_hdr(skb);
struct tcphdr *t1;
@@ -866,6 +868,13 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
if (key)
tot_len += TCPOLEN_MD5SIG_ALIGNED;
#endif
+#ifdef CONFIG_TCP_AO
+ if (ao_key)
+ tot_len += tcp_ao_len(ao_key);
+#endif
+#if defined(CONFIG_TCP_MD5SIG) && defined(CONFIG_TCP_AO)
+ WARN_ON_ONCE(key && ao_key);
+#endif

#ifdef CONFIG_MPTCP
if (rst && !key) {
@@ -917,6 +926,21 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
&ipv6_hdr(skb)->daddr, t1);
}
#endif
+#ifdef CONFIG_TCP_AO
+ if (ao_key) {
+ *topt++ = htonl((TCPOPT_AO << 24) | (tcp_ao_len(ao_key) << 16) |
+ (ao_key->sndid << 8) | (rcv_next));
+
+ /* TODO: this is right now not going to work for listening
+ * sockets since the socket won't have the needed ipv6
+ * addresses
+ */
+ tcp_ao_hash_hdr(AF_INET6, (char *)topt, ao_key, tkey,
+ (union tcp_ao_addr *)&ipv6_hdr(skb)->saddr,
+ (union tcp_ao_addr *)&ipv6_hdr(skb)->daddr,
+ t1, ao_sne);
+ }
+#endif

memset(&fl6, 0, sizeof(fl6));
fl6.daddr = ipv6_hdr(skb)->saddr;
@@ -990,6 +1014,15 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
__be32 label = 0;
u32 priority = 0;
struct net *net;
+ struct tcp_ao_key *ao_key = NULL;
+ u8 rcv_next = 0;
+ u32 ao_sne = 0;
+#ifdef CONFIG_TCP_AO
+ char traffic_key[TCP_AO_MAX_HASH_SIZE] __tcp_ao_key_align;
+ const struct tcp_ao_hdr *aoh;
+#else
+ u8 *traffic_key = NULL;
+#endif
int oif = 0;

if (th->rst)
@@ -1004,8 +1037,13 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
/* Invalid TCP option size or twice included auth */
+#if defined(CONFIG_TCP_AO)
+ if (tcp_parse_auth_options(th, &md5_hash_location, &aoh))
+ return;
+#else
if (tcp_parse_auth_options(th, &md5_hash_location, NULL))
return;
+#endif

rcu_read_lock();
#endif
@@ -1059,6 +1097,38 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
ack_seq = ntohl(th->seq) + th->syn + th->fin + skb->len -
(th->doff << 2);

+#ifdef CONFIG_TCP_AO
+ /* XXX: Not implemented for listening sockets yet. How do we
+ * get the initial sequence numbers? Might need to pass in
+ * the request socket.
+ */
+ if (sk && aoh && sk->sk_state != TCP_LISTEN) {
+ struct tcp_ao_info *ao_info;
+
+ if (WARN_ON_ONCE(sk->sk_state == TCP_NEW_SYN_RECV))
+ goto out;
+
+ /* rcv_next is the peer's here */
+ ao_key = tcp_ao_do_lookup_sndid(sk, aoh->rnext_keyid);
+
+ if (ao_key) {
+ ao_info = rcu_dereference(tcp_sk(sk)->ao_info);
+
+ /* XXX: optimize by using cached traffic key depending
+ * on socket state
+ */
+ tcp_v6_ao_calc_key_sk(ao_key, traffic_key, sk,
+ ao_info->lisn, ao_info->risn,
+ true);
+
+ /* rcv_next switches to our rcv_next */
+ rcv_next = ao_info->rnext_key->rcvid;
+ ao_sne = tcp_ao_compute_sne(ao_info->snd_sne,
+ ao_info->snd_sne_seq, seq);
+ }
+ }
+#endif
+
if (sk) {
oif = sk->sk_bound_dev_if;
if (sk_fullsock(sk)) {
@@ -1079,7 +1149,8 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
}

tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, key, 1,
- ipv6_get_dsfield(ipv6h), label, priority);
+ ipv6_get_dsfield(ipv6h), label, priority,
+ ao_key, traffic_key, rcv_next, ao_sne);

#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
out:
@@ -1093,7 +1164,7 @@ static void tcp_v6_send_ack(const struct sock *sk, struct sk_buff *skb, u32 seq,
__be32 label, u32 priority)
{
tcp_v6_send_response(sk, skb, seq, ack, win, tsval, tsecr, oif, key, 0,
- tclass, label, priority);
+ tclass, label, priority, NULL, NULL, 0, 0);
}

static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
--
2.37.2

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