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Message-ID: <20231004223629.166300-13-dima@arista.com>
Date: Wed, 4 Oct 2023 23:36:16 +0100
From: Dmitry Safonov <dima@...sta.com>
To: David Ahern <dsahern@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Paolo Abeni <pabeni@...hat.com>,
Jakub Kicinski <kuba@...nel.org>,
"David S. Miller" <davem@...emloft.net>
Cc: linux-kernel@...r.kernel.org, Dmitry Safonov <dima@...sta.com>,
Andy Lutomirski <luto@...capital.net>,
Ard Biesheuvel <ardb@...nel.org>,
Bob Gilligan <gilligan@...sta.com>,
Dan Carpenter <error27@...il.com>,
David Laight <David.Laight@...lab.com>,
Dmitry Safonov <0x7f454c46@...il.com>,
Donald Cassidy <dcassidy@...hat.com>,
Eric Biggers <ebiggers@...nel.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Francesco Ruggeri <fruggeri05@...il.com>,
"Gaillardetz, Dominik" <dgaillar@...na.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Ivan Delalande <colona@...sta.com>,
Leonard Crestez <cdleonard@...il.com>,
"Nassiri, Mohammad" <mnassiri@...na.com>,
Salam Noureddine <noureddine@...sta.com>,
Simon Horman <simon.horman@...igine.com>,
"Tetreault, Francois" <ftetreau@...na.com>, netdev@...r.kernel.org
Subject: [PATCH v13 net-next 12/23] net/tcp: Verify inbound TCP-AO signed segments
Now there is a common function to verify signature on TCP segments:
tcp_inbound_hash(). It has checks for all possible cross-interactions
with MD5 signs as well as with unsigned segments.
The rules from RFC5925 are:
(1) Any TCP segment can have at max only one signature.
(2) TCP connections can't switch between using TCP-MD5 and TCP-AO.
(3) TCP-AO connections can't stop using AO, as well as unsigned
connections can't suddenly start using AO.
Co-developed-by: Francesco Ruggeri <fruggeri@...sta.com>
Signed-off-by: Francesco Ruggeri <fruggeri@...sta.com>
Co-developed-by: Salam Noureddine <noureddine@...sta.com>
Signed-off-by: Salam Noureddine <noureddine@...sta.com>
Signed-off-by: Dmitry Safonov <dima@...sta.com>
Acked-by: David Ahern <dsahern@...nel.org>
---
include/net/dropreason-core.h | 17 ++++
include/net/tcp.h | 53 ++++++++++++-
include/net/tcp_ao.h | 14 ++++
net/ipv4/tcp.c | 39 ++--------
net/ipv4/tcp_ao.c | 142 ++++++++++++++++++++++++++++++++++
net/ipv4/tcp_ipv4.c | 10 +--
net/ipv6/tcp_ao.c | 9 ++-
net/ipv6/tcp_ipv6.c | 11 +--
8 files changed, 248 insertions(+), 47 deletions(-)
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 216cde184db1..a01e1860fe25 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -24,6 +24,10 @@
FN(TCP_MD5NOTFOUND) \
FN(TCP_MD5UNEXPECTED) \
FN(TCP_MD5FAILURE) \
+ FN(TCP_AONOTFOUND) \
+ FN(TCP_AOUNEXPECTED) \
+ FN(TCP_AOKEYNOTFOUND) \
+ FN(TCP_AOFAILURE) \
FN(SOCKET_BACKLOG) \
FN(TCP_FLAGS) \
FN(TCP_ZEROWINDOW) \
@@ -162,6 +166,19 @@ enum skb_drop_reason {
* to LINUX_MIB_TCPMD5FAILURE
*/
SKB_DROP_REASON_TCP_MD5FAILURE,
+ /**
+ * @SKB_DROP_REASON_TCP_AONOTFOUND: no TCP-AO hash and one was expected
+ */
+ SKB_DROP_REASON_TCP_AONOTFOUND,
+ /**
+ * @SKB_DROP_REASON_TCP_AOUNEXPECTED: TCP-AO hash is present and it
+ * was not expected.
+ */
+ SKB_DROP_REASON_TCP_AOUNEXPECTED,
+ /** @SKB_DROP_REASON_TCP_AOKEYNOTFOUND: TCP-AO key is unknown */
+ SKB_DROP_REASON_TCP_AOKEYNOTFOUND,
+ /** @SKB_DROP_REASON_TCP_AOFAILURE: TCP-AO hash is wrong */
+ SKB_DROP_REASON_TCP_AOFAILURE,
/**
* @SKB_DROP_REASON_SOCKET_BACKLOG: failed to add skb to socket backlog (
* see LINUX_MIB_TCPBACKLOGDROP)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index e2e4e09fb608..2433687c462b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1773,7 +1773,7 @@ tcp_md5_do_lookup_any_l3index(const struct sock *sk,
enum skb_drop_reason
tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
const void *saddr, const void *daddr,
- int family, int dif, int sdif);
+ int family, int l3index, const __u8 *hash_location);
#define tcp_twsk_md5_key(twsk) ((twsk)->tw_md5_key)
@@ -1795,7 +1795,7 @@ tcp_md5_do_lookup_any_l3index(const struct sock *sk,
static inline enum skb_drop_reason
tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
const void *saddr, const void *daddr,
- int family, int dif, int sdif)
+ int family, int l3index, const __u8 *hash_location)
{
return SKB_NOT_DROPPED_YET;
}
@@ -2690,4 +2690,53 @@ static inline bool tcp_ao_required(struct sock *sk, const void *saddr,
return false;
}
+/* Called with rcu_read_lock() */
+static inline enum skb_drop_reason
+tcp_inbound_hash(struct sock *sk, const struct request_sock *req,
+ const struct sk_buff *skb,
+ const void *saddr, const void *daddr,
+ int family, int dif, int sdif)
+{
+ const struct tcphdr *th = tcp_hdr(skb);
+ const struct tcp_ao_hdr *aoh;
+ const __u8 *md5_location;
+ int l3index;
+
+ /* Invalid option or two times meet any of auth options */
+ if (tcp_parse_auth_options(th, &md5_location, &aoh))
+ return SKB_DROP_REASON_TCP_AUTH_HDR;
+
+ if (req) {
+ if (tcp_rsk_used_ao(req) != !!aoh)
+ return SKB_DROP_REASON_TCP_AOFAILURE;
+ }
+
+ /* sdif set, means packet ingressed via a device
+ * in an L3 domain and dif is set to the l3mdev
+ */
+ l3index = sdif ? dif : 0;
+
+ /* Fast path: unsigned segments */
+ if (likely(!md5_location && !aoh)) {
+ /* Drop if there's TCP-MD5 or TCP-AO key with any rcvid/sndid
+ * for the remote peer. On TCP-AO established connection
+ * the last key is impossible to remove, so there's
+ * always at least one current_key.
+ */
+ if (tcp_ao_required(sk, saddr, family))
+ return SKB_DROP_REASON_TCP_AONOTFOUND;
+ if (unlikely(tcp_md5_do_lookup(sk, l3index, saddr, family))) {
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5NOTFOUND);
+ return SKB_DROP_REASON_TCP_MD5NOTFOUND;
+ }
+ return SKB_NOT_DROPPED_YET;
+ }
+
+ if (aoh)
+ return tcp_inbound_ao_hash(sk, skb, family, req, aoh);
+
+ return tcp_inbound_md5_hash(sk, skb, saddr, daddr, family,
+ l3index, md5_location);
+}
+
#endif /* _TCP_H */
diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index 56c2e34ad7d2..6e62235c7cae 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -111,6 +111,9 @@ struct tcp6_ao_context {
};
struct tcp_sigpool;
+#define TCP_AO_ESTABLISHED (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | \
+ TCPF_CLOSE | TCPF_CLOSE_WAIT | \
+ TCPF_LAST_ACK | TCPF_CLOSING)
int tcp_ao_transmit_skb(struct sock *sk, struct sk_buff *skb,
struct tcp_ao_key *key, struct tcphdr *th,
@@ -130,6 +133,10 @@ 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, bool twsk);
void tcp_ao_time_wait(struct tcp_timewait_sock *tcptw, struct tcp_sock *tp);
+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);
struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
const union tcp_ao_addr *addr,
int family, int sndid, int rcvid);
@@ -208,6 +215,13 @@ static inline void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
{
}
+static inline 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)
+{
+ return SKB_NOT_DROPPED_YET;
+}
+
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)
{
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9e38699d714a..dab7a9cf2627 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4369,42 +4369,23 @@ EXPORT_SYMBOL(tcp_md5_hash_key);
enum skb_drop_reason
tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
const void *saddr, const void *daddr,
- int family, int dif, int sdif)
+ int family, int l3index, const __u8 *hash_location)
{
- /*
- * This gets called for each TCP segment that arrives
- * so we want to be efficient.
+ /* This gets called for each TCP segment that has TCP-MD5 option.
* We have 3 drop cases:
* o No MD5 hash and one expected.
* o MD5 hash and we're not expecting one.
* o MD5 hash and its wrong.
*/
- const __u8 *hash_location = NULL;
- struct tcp_md5sig_key *hash_expected;
const struct tcphdr *th = tcp_hdr(skb);
const struct tcp_sock *tp = tcp_sk(sk);
- int genhash, l3index;
+ struct tcp_md5sig_key *key;
u8 newhash[16];
+ int genhash;
- /* sdif set, means packet ingressed via a device
- * in an L3 domain and dif is set to the l3mdev
- */
- l3index = sdif ? dif : 0;
+ key = tcp_md5_do_lookup(sk, l3index, saddr, family);
- hash_expected = tcp_md5_do_lookup(sk, l3index, saddr, family);
- if (tcp_parse_auth_options(th, &hash_location, NULL))
- return SKB_DROP_REASON_TCP_AUTH_HDR;
-
- /* We've parsed the options - do we have a hash? */
- if (!hash_expected && !hash_location)
- return SKB_NOT_DROPPED_YET;
-
- if (hash_expected && !hash_location) {
- NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5NOTFOUND);
- return SKB_DROP_REASON_TCP_MD5NOTFOUND;
- }
-
- if (!hash_expected && hash_location) {
+ if (!key && hash_location) {
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5UNEXPECTED);
return SKB_DROP_REASON_TCP_MD5UNEXPECTED;
}
@@ -4414,14 +4395,10 @@ tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
* IPv4-mapped case.
*/
if (family == AF_INET)
- genhash = tcp_v4_md5_hash_skb(newhash,
- hash_expected,
- NULL, skb);
+ genhash = tcp_v4_md5_hash_skb(newhash, key, NULL, skb);
else
- genhash = tp->af_specific->calc_md5_hash(newhash,
- hash_expected,
+ genhash = tp->af_specific->calc_md5_hash(newhash, key,
NULL, skb);
-
if (genhash || memcmp(hash_location, newhash, 16) != 0) {
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMD5FAILURE);
if (family == AF_INET) {
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 0102d0662fca..4813b9283c55 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -761,6 +761,148 @@ void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
treq->maclen = tcp_ao_maclen(key);
}
+static enum skb_drop_reason
+tcp_ao_verify_hash(const struct sock *sk, const struct sk_buff *skb,
+ unsigned short int family, struct tcp_ao_info *info,
+ const struct tcp_ao_hdr *aoh, struct tcp_ao_key *key,
+ u8 *traffic_key, u8 *phash, u32 sne)
+{
+ u8 maclen = aoh->length - sizeof(struct tcp_ao_hdr);
+ const struct tcphdr *th = tcp_hdr(skb);
+ void *hash_buf = NULL;
+
+ if (maclen != tcp_ao_maclen(key))
+ return SKB_DROP_REASON_TCP_AOFAILURE;
+
+ hash_buf = kmalloc(tcp_ao_digest_size(key), GFP_ATOMIC);
+ if (!hash_buf)
+ return SKB_DROP_REASON_NOT_SPECIFIED;
+
+ /* XXX: make it per-AF callback? */
+ tcp_ao_hash_skb(family, hash_buf, key, sk, skb, traffic_key,
+ (phash - (u8 *)th), sne);
+ if (memcmp(phash, hash_buf, maclen)) {
+ kfree(hash_buf);
+ return SKB_DROP_REASON_TCP_AOFAILURE;
+ }
+ kfree(hash_buf);
+ return SKB_NOT_DROPPED_YET;
+}
+
+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)
+{
+ const struct tcphdr *th = tcp_hdr(skb);
+ u8 *phash = (u8 *)(aoh + 1); /* hash goes just after the header */
+ struct tcp_ao_info *info;
+ enum skb_drop_reason ret;
+ struct tcp_ao_key *key;
+ __be32 sisn, disn;
+ u8 *traffic_key;
+ u32 sne = 0;
+
+ info = rcu_dereference(tcp_sk(sk)->ao_info);
+ if (!info)
+ return SKB_DROP_REASON_TCP_AOUNEXPECTED;
+
+ if (unlikely(th->syn)) {
+ sisn = th->seq;
+ disn = 0;
+ }
+
+ /* Fast-path */
+ if (likely((1 << sk->sk_state) & TCP_AO_ESTABLISHED)) {
+ enum skb_drop_reason err;
+ struct tcp_ao_key *current_key;
+
+ /* Check if this socket's rnext_key matches the keyid in the
+ * packet. If not we lookup the key based on the keyid
+ * matching the rcvid in the mkt.
+ */
+ key = READ_ONCE(info->rnext_key);
+ if (key->rcvid != aoh->keyid) {
+ key = tcp_ao_established_key(info, -1, aoh->keyid);
+ if (!key)
+ goto key_not_found;
+ }
+
+ /* Delayed retransmitted SYN */
+ if (unlikely(th->syn && !th->ack))
+ goto verify_hash;
+
+ sne = 0;
+ /* Established socket, traffic key are cached */
+ traffic_key = rcv_other_key(key);
+ err = tcp_ao_verify_hash(sk, skb, family, info, aoh, key,
+ traffic_key, phash, sne);
+ if (err)
+ return err;
+ current_key = READ_ONCE(info->current_key);
+ /* Key rotation: the peer asks us to use new key (RNext) */
+ if (unlikely(aoh->rnext_keyid != current_key->sndid)) {
+ /* If the key is not found we do nothing. */
+ key = tcp_ao_established_key(info, aoh->rnext_keyid, -1);
+ if (key)
+ /* pairs with tcp_ao_del_cmd */
+ WRITE_ONCE(info->current_key, key);
+ }
+ return SKB_NOT_DROPPED_YET;
+ }
+
+ /* Lookup key based on peer address and keyid.
+ * current_key and rnext_key must not be used on tcp listen
+ * sockets as otherwise:
+ * - request sockets would race on those key pointers
+ * - tcp_ao_del_cmd() allows async key removal
+ */
+ key = tcp_ao_inbound_lookup(family, sk, skb, -1, aoh->keyid);
+ if (!key)
+ goto key_not_found;
+
+ if (th->syn && !th->ack)
+ goto verify_hash;
+
+ if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_NEW_SYN_RECV)) {
+ /* Make the initial syn the likely case here */
+ if (unlikely(req)) {
+ sne = 0;
+ 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;
+ } else if (unlikely(!th->syn)) {
+ /* no way to figure out initial sisn/disn - drop */
+ return SKB_DROP_REASON_TCP_FLAGS;
+ }
+ } else if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
+ disn = info->lisn;
+ if (th->syn || th->rst)
+ sisn = th->seq;
+ else
+ sisn = info->risn;
+ } else {
+ WARN_ONCE(1, "TCP-AO: Unexpected sk_state %d", sk->sk_state);
+ return SKB_DROP_REASON_TCP_AOFAILURE;
+ }
+verify_hash:
+ traffic_key = kmalloc(tcp_ao_digest_size(key), GFP_ATOMIC);
+ if (!traffic_key)
+ return SKB_DROP_REASON_NOT_SPECIFIED;
+ tcp_ao_calc_key_skb(key, traffic_key, skb, sisn, disn, family);
+ ret = tcp_ao_verify_hash(sk, skb, family, info, aoh, key,
+ traffic_key, phash, sne);
+ kfree(traffic_key);
+ return ret;
+
+key_not_found:
+ return SKB_DROP_REASON_TCP_AOKEYNOTFOUND;
+}
+
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 b4d26d893f9d..1b1ad6da5929 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2202,9 +2202,9 @@ int tcp_v4_rcv(struct sk_buff *skb)
if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
drop_reason = SKB_DROP_REASON_XFRM_POLICY;
else
- drop_reason = tcp_inbound_md5_hash(sk, skb,
- &iph->saddr, &iph->daddr,
- AF_INET, dif, sdif);
+ drop_reason = tcp_inbound_hash(sk, req, skb,
+ &iph->saddr, &iph->daddr,
+ AF_INET, dif, sdif);
if (unlikely(drop_reason)) {
sk_drops_add(sk, skb);
reqsk_put(req);
@@ -2281,8 +2281,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
goto discard_and_relse;
}
- drop_reason = tcp_inbound_md5_hash(sk, skb, &iph->saddr,
- &iph->daddr, AF_INET, dif, sdif);
+ drop_reason = tcp_inbound_hash(sk, NULL, skb, &iph->saddr, &iph->daddr,
+ AF_INET, dif, sdif);
if (drop_reason)
goto discard_and_relse;
diff --git a/net/ipv6/tcp_ao.c b/net/ipv6/tcp_ao.c
index 99753e12c08c..8b04611c9078 100644
--- a/net/ipv6/tcp_ao.c
+++ b/net/ipv6/tcp_ao.c
@@ -53,11 +53,12 @@ int tcp_v6_ao_calc_key_skb(struct tcp_ao_key *mkt, u8 *key,
const struct sk_buff *skb,
__be32 sisn, __be32 disn)
{
- const struct ipv6hdr *iph = ipv6_hdr(skb);
- const struct tcphdr *th = tcp_hdr(skb);
+ const struct ipv6hdr *iph = ipv6_hdr(skb);
+ const struct tcphdr *th = tcp_hdr(skb);
- return tcp_v6_ao_calc_key(mkt, key, &iph->saddr, &iph->daddr,
- th->source, th->dest, sisn, disn);
+ return tcp_v6_ao_calc_key(mkt, key, &iph->saddr,
+ &iph->daddr, th->source,
+ th->dest, sisn, disn);
}
int tcp_v6_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 38d784236168..412e75788247 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1779,9 +1779,9 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
struct sock *nsk;
sk = req->rsk_listener;
- drop_reason = tcp_inbound_md5_hash(sk, skb,
- &hdr->saddr, &hdr->daddr,
- AF_INET6, dif, sdif);
+ drop_reason = tcp_inbound_hash(sk, req, skb,
+ &hdr->saddr, &hdr->daddr,
+ AF_INET6, dif, sdif);
if (drop_reason) {
sk_drops_add(sk, skb);
reqsk_put(req);
@@ -1854,8 +1854,8 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
goto discard_and_relse;
}
- drop_reason = tcp_inbound_md5_hash(sk, skb, &hdr->saddr, &hdr->daddr,
- AF_INET6, dif, sdif);
+ drop_reason = tcp_inbound_hash(sk, NULL, skb, &hdr->saddr, &hdr->daddr,
+ AF_INET6, dif, sdif);
if (drop_reason)
goto discard_and_relse;
@@ -2083,6 +2083,7 @@ static const struct tcp_sock_af_ops tcp_sock_ipv6_mapped_specific = {
.ao_lookup = tcp_v6_ao_lookup,
.calc_ao_hash = tcp_v4_ao_hash_skb,
.ao_parse = tcp_v6_parse_ao,
+ .ao_calc_key_sk = tcp_v4_ao_calc_key_sk,
#endif
};
#endif
--
2.42.0
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