[PATCH v10 net-next 08/23] net/tcp: Add AO sign to RST packets

From: Dmitry Safonov
Date: Tue Aug 15 2023 - 15:16:23 EST

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>
Acked-by: David Ahern <dsahern@xxxxxxxxxx>
---
include/net/tcp_ao.h | 12 +++++
net/ipv4/tcp_ao.c | 104 ++++++++++++++++++++++++++++++++++++++++++-
net/ipv4/tcp_ipv4.c | 69 ++++++++++++++++++++++------
net/ipv6/tcp_ipv6.c | 70 ++++++++++++++++++++++-------
4 files changed, 225 insertions(+), 30 deletions(-)

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index e685ad9db949..67f997aabd9c 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -117,12 +117,24 @@ 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, u32 seq,
+ 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,
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index d10daee79fe6..81ce4fe546f2 100644
--- a/net/ipv4/tcp_ao.c
+++ b/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 +495,46 @@ 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, u32 seq,
+ struct tcp_ao_key **key, char **traffic_key,
+ bool *allocated_traffic_key, u8 *keyid, u32 *sne)
+{
+ 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)) {
+ return -1;
+ } else {
+ struct tcp_ao_key *rnext_key;
+
+ if (sk->sk_state == TCP_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;
+}
+
static int tcp_ao_cache_traffic_keys(const struct sock *sk,
struct tcp_ao_info *ao,
struct tcp_ao_key *ao_key)
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 31169971cc56..f07a12f478d4 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/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, reply->seq,
+ &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;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 5c1880d5f5bc..08b016d5c1d9 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -854,7 +854,9 @@ 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, u32 txhash)
+ u8 tclass, __be32 label, u32 priority, u32 txhash,
+ struct tcp_ao_key *ao_key, char *tkey,
+ u8 rcv_next, u32 ao_sne)
{
const struct tcphdr *th = tcp_hdr(skb);
struct tcphdr *t1;
@@ -873,6 +875,13 @@ 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) {
@@ -924,6 +933,17 @@ 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));
+
+ 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;
@@ -986,19 +1006,24 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
{
const struct tcphdr *th = tcp_hdr(skb);
struct ipv6hdr *ipv6h = ipv6_hdr(skb);
- u32 seq = 0, ack_seq = 0;
- struct tcp_md5sig_key *key = NULL;
-#ifdef CONFIG_TCP_MD5SIG
const __u8 *md5_hash_location = NULL;
+ u32 seq = 0, ack_seq = 0, ao_sne = 0;
+ bool allocated_traffic_key = false;
+ struct tcp_md5sig_key *key = NULL;
+ struct tcp_ao_key *ao_key = NULL;
+ const struct tcp_ao_hdr *aoh;
+ char *traffic_key = NULL;
+ __be32 label = 0;
+ u32 priority = 0;
+ struct net *net;
+ u8 rcv_next = 0;
+ u32 txhash = 0;
+ int oif = 0;
+#ifdef CONFIG_TCP_MD5SIG
unsigned char newhash[16];
int genhash;
struct sock *sk1 = NULL;
#endif
- __be32 label = 0;
- u32 priority = 0;
- struct net *net;
- u32 txhash = 0;
- int oif = 0;

if (th->rst)
return;
@@ -1010,12 +1035,11 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb)
return;

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(th, &md5_hash_location, NULL))
+ if (tcp_parse_auth_options(th, &md5_hash_location, &aoh))
return;
-
rcu_read_lock();
+#ifdef CONFIG_TCP_MD5SIG
if (sk && sk_fullsock(sk)) {
int l3index;

@@ -1064,6 +1088,19 @@ 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
+ if (aoh) {
+ int l3index;
+
+ l3index = tcp_v6_sdif(skb) ? tcp_v6_iif_l3_slave(skb) : 0;
+ if (tcp_ao_prepare_reset(sk, skb, aoh, l3index, htonl(seq),
+ &ao_key, &traffic_key,
+ &allocated_traffic_key,
+ &rcv_next, &ao_sne))
+ goto out;
+ }
+#endif
+
if (sk) {
oif = sk->sk_bound_dev_if;
if (sk_fullsock(sk)) {
@@ -1086,10 +1123,13 @@ 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, txhash);
+ ipv6_get_dsfield(ipv6h), label, priority, txhash,
+ ao_key, traffic_key, rcv_next, ao_sne);

-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
out:
+ if (allocated_traffic_key)
+ kfree(traffic_key);
rcu_read_unlock();
#endif
}
@@ -1100,7 +1140,7 @@ static void tcp_v6_send_ack(const struct sock *sk, struct sk_buff *skb, u32 seq,
__be32 label, u32 priority, u32 txhash)
{
tcp_v6_send_response(sk, skb, seq, ack, win, tsval, tsecr, oif, key, 0,
- tclass, label, priority, txhash);
+ tclass, label, priority, txhash, NULL, NULL, 0, 0);
}

static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
--
2.41.0