diff mbox series

[v4,04/21] net/tcp: Prevent TCP-MD5 with TCP-AO being set

Message ID 20230215183335.800122-5-dima@arista.com
State New
Headers
Series net/tcp: Add TCP-AO support |

Commit Message

Dmitry Safonov Feb. 15, 2023, 6:33 p.m. UTC 
  Be as conservative as possible: if there is TCP-MD5 key for a given peer
regardless of L3 interface - don't allow setting TCP-AO key for the same
peer. According to RFC5925, TCP-AO is supposed to replace TCP-MD5 and
there can't be any switch between both on any connected tuple.
Later it can be relaxed, if there's a use, but in the beginning restrict
any intersection.

Note: it's still should be possible to set both TCP-MD5 and TCP-AO keys
on a listening socket for *different* peers.

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     | 24 ++++++++++++++++++++++--
 include/net/tcp_ao.h  | 15 +++++++++++++++
 net/ipv4/tcp_ao.c     | 12 ++++++++++++
 net/ipv4/tcp_ipv4.c   | 12 +++++++++---
 net/ipv4/tcp_output.c | 36 ++++++++++++++++++++++++++++++++++++
 net/ipv6/tcp_ao.c     | 17 +++++++++++++++++
 net/ipv6/tcp_ipv6.c   | 22 ++++++++++++++++++----
 7 files changed, 129 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/include/net/tcp.h b/include/net/tcp.h
index fb18558053cc..2673cc8e5ed5 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1701,6 +1701,7 @@  int tcp_md5_key_copy(struct sock *sk, const union tcp_md5_addr *addr,
 
 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
 		   int family, u8 prefixlen, int l3index, u8 flags);
+void tcp_clear_md5_list(struct sock *sk);
 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
 					 const struct sock *addr_sk);
 
@@ -1709,14 +1710,23 @@  struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
 extern struct static_key_false_deferred tcp_md5_needed;
 struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
 					   const union tcp_md5_addr *addr,
-					   int family);
+					   int family, bool any_l3index);
 static inline struct tcp_md5sig_key *
 tcp_md5_do_lookup(const struct sock *sk, int l3index,
 		  const union tcp_md5_addr *addr, int family)
 {
 	if (!static_branch_unlikely(&tcp_md5_needed.key))
 		return NULL;
-	return __tcp_md5_do_lookup(sk, l3index, addr, family);
+	return __tcp_md5_do_lookup(sk, l3index, addr, family, false);
+}
+
+static inline struct tcp_md5sig_key *
+tcp_md5_do_lookup_any_l3index(const struct sock *sk,
+			      const union tcp_md5_addr *addr, int family)
+{
+	if (!static_branch_unlikely(&tcp_md5_needed.key))
+		return NULL;
+	return __tcp_md5_do_lookup(sk, 0, addr, family, true);
 }
 
 enum skb_drop_reason
@@ -1734,6 +1744,13 @@  tcp_md5_do_lookup(const struct sock *sk, int l3index,
 	return NULL;
 }
 
+static inline struct tcp_md5sig_key *
+tcp_md5_do_lookup_any_l3index(const struct sock *sk,
+			      const union tcp_md5_addr *addr, int family)
+{
+	return NULL;
+}
+
 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,
@@ -2097,6 +2114,9 @@  struct tcp_sock_af_ops {
 					    int optname,
 					    sockptr_t optval,
 					    int optlen);
+	struct tcp_ao_key	*(*ao_lookup)(const struct sock *sk,
+					      struct sock  *addr_sk,
+					      int sndid, int rcvid);
 #endif
 };
 
diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index 92c8c3ed42db..d817dac3bb0a 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -91,12 +91,27 @@  struct tcp_ao_info {
 int tcp_parse_ao(struct sock *sk, int cmd, unsigned short int family,
 		 sockptr_t optval, int optlen);
 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, u16 port);
 /* 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,
+				    int sndid, int rcvid);
 /* ipv6 specific functions */
+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
+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)
+{
+	return NULL;
+}
+
 static inline void tcp_ao_destroy_sock(struct sock *sk)
 {
 }
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 2dc8a3e946b1..4861ba9c89b9 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -165,6 +165,14 @@  void tcp_ao_destroy_sock(struct sock *sk)
 	kfree_rcu(ao, rcu);
 }
 
+struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
+				    int sndid, int rcvid)
+{
+	union tcp_ao_addr *addr = (union tcp_ao_addr *)&addr_sk->sk_daddr;
+
+	return tcp_ao_do_lookup(sk, addr, AF_INET, sndid, rcvid, 0);
+}
+
 static int tcp_ao_current_rnext(struct sock *sk, u16 tcpa_flags,
 				u8 tcpa_sndid, u8 tcpa_rcvid)
 {
@@ -619,6 +627,10 @@  static int tcp_ao_add_cmd(struct sock *sk, unsigned short int family,
 	if (cmd.tcpa_keyflags & ~TCP_AO_KEYF_ALL)
 		return -EINVAL;
 
+	/* Don't allow keys for peers that have a matching TCP-MD5 key */
+	if (tcp_md5_do_lookup_any_l3index(sk, addr, family))
+		return -EKEYREJECTED;
+
 	ao_info = rcu_dereference_protected(tcp_sk(sk)->ao_info,
 					    lockdep_sock_is_held(sk));
 
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 60695942ee2b..b143f5f0ca38 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1073,7 +1073,7 @@  static bool better_md5_match(struct tcp_md5sig_key *old, struct tcp_md5sig_key *
 /* Find the Key structure for an address.  */
 struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
 					   const union tcp_md5_addr *addr,
-					   int family)
+					   int family, bool any_l3index)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_key *key;
@@ -1092,7 +1092,8 @@  struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
 				 lockdep_sock_is_held(sk)) {
 		if (key->family != family)
 			continue;
-		if (key->flags & TCP_MD5SIG_FLAG_IFINDEX && key->l3index != l3index)
+		if (!any_l3index && key->flags & TCP_MD5SIG_FLAG_IFINDEX &&
+		    key->l3index != l3index)
 			continue;
 		if (family == AF_INET) {
 			mask = inet_make_mask(key->prefixlen);
@@ -1304,7 +1305,7 @@  int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, int family,
 }
 EXPORT_SYMBOL(tcp_md5_do_del);
 
-static void tcp_clear_md5_list(struct sock *sk)
+void tcp_clear_md5_list(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_key *key;
@@ -1374,6 +1375,10 @@  static int tcp_v4_parse_md5_keys(struct sock *sk, int optname,
 	if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
 		return -EINVAL;
 
+	/* Don't allow keys for peers that have a matching TCP-AO key */
+	if (tcp_ao_do_lookup(sk, addr, AF_INET, -1, -1, 0))
+		return -EKEYREJECTED;
+
 	return tcp_md5_do_add(sk, addr, AF_INET, prefixlen, l3index, flags,
 			      cmd.tcpm_key, cmd.tcpm_keylen);
 }
@@ -2268,6 +2273,7 @@  static const struct tcp_sock_af_ops tcp_sock_ipv4_specific = {
 	.md5_parse		= tcp_v4_parse_md5_keys,
 #endif
 #ifdef CONFIG_TCP_AO
+	.ao_lookup		= tcp_v4_ao_lookup,
 	.ao_parse		= tcp_v4_parse_ao,
 #endif
 };
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 71d01cf3c13e..3fe291e4a6a2 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3839,6 +3839,42 @@  int tcp_connect(struct sock *sk)
 
 	tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
 
+#if defined(CONFIG_TCP_MD5SIG) && defined(CONFIG_TCP_AO)
+	/* Has to be checked late, after setting daddr/saddr/ops.
+	 * Return error if the peer has both a md5 and a tcp-ao key
+	 * configured as this is ambiguous.
+	 */
+	if (unlikely(rcu_dereference_protected(tp->md5sig_info,
+					       lockdep_sock_is_held(sk)))) {
+		bool needs_md5 = !!tp->af_specific->md5_lookup(sk, sk);
+		bool needs_ao = !!tp->af_specific->ao_lookup(sk, sk, -1, -1);
+
+		if (needs_md5 && needs_ao)
+			return -EKEYREJECTED;
+
+		/* If we have a matching md5 key and no matching tcp-ao key
+		 * then free up ao_info if allocated.
+		 */
+		if (needs_md5) {
+			tcp_ao_destroy_sock(sk);
+		} else if (needs_ao) {
+			tcp_clear_md5_list(sk);
+			kfree(rcu_replace_pointer(tp->md5sig_info, NULL,
+						  lockdep_sock_is_held(sk)));
+		}
+	}
+#endif
+#ifdef CONFIG_TCP_AO
+	if (unlikely(rcu_dereference_protected(tp->ao_info,
+					       lockdep_sock_is_held(sk)))) {
+		/* Don't allow connecting if ao is configured but no
+		 * matching key is found.
+		 */
+		if (!tp->af_specific->ao_lookup(sk, sk, -1, -1))
+			return -EKEYREJECTED;
+	}
+#endif
+
 	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
 		return -EHOSTUNREACH; /* Routing failure or similar. */
 
diff --git a/net/ipv6/tcp_ao.c b/net/ipv6/tcp_ao.c
index 049ddbabe049..a56ab0a9cf55 100644
--- a/net/ipv6/tcp_ao.c
+++ b/net/ipv6/tcp_ao.c
@@ -12,6 +12,23 @@ 
 #include <net/tcp.h>
 #include <net/ipv6.h>
 
+struct tcp_ao_key *tcp_v6_ao_do_lookup(const struct sock *sk,
+				       const struct in6_addr *addr,
+				       int sndid, int rcvid)
+{
+	return tcp_ao_do_lookup(sk, (union tcp_ao_addr *)addr, AF_INET6,
+				sndid, rcvid, 0);
+}
+
+struct tcp_ao_key *tcp_v6_ao_lookup(const struct sock *sk,
+				    struct sock *addr_sk,
+				    int sndid, int rcvid)
+{
+	struct in6_addr *addr = &addr_sk->sk_v6_daddr;
+
+	return tcp_v6_ao_do_lookup(sk, addr, sndid, rcvid);
+}
+
 int tcp_v6_parse_ao(struct sock *sk, int cmd,
 		    sockptr_t optval, int optlen)
 {
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 9edb84eb457b..8b38c112affb 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -601,6 +601,7 @@  static int tcp_v6_parse_md5_keys(struct sock *sk, int optname,
 {
 	struct tcp_md5sig cmd;
 	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&cmd.tcpm_addr;
+	union tcp_ao_addr *addr;
 	int l3index = 0;
 	u8 prefixlen;
 	u8 flags;
@@ -655,13 +656,24 @@  static int tcp_v6_parse_md5_keys(struct sock *sk, int optname,
 	if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
 		return -EINVAL;
 
-	if (ipv6_addr_v4mapped(&sin6->sin6_addr))
-		return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3],
+	if (ipv6_addr_v4mapped(&sin6->sin6_addr)) {
+		addr = (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3];
+
+		/* Don't allow keys for peers that have a matching TCP-AO key */
+		if (tcp_ao_do_lookup(sk, addr, AF_INET, -1, -1, 0))
+			return -EKEYREJECTED;
+		return tcp_md5_do_add(sk, addr,
 				      AF_INET, prefixlen, l3index, flags,
 				      cmd.tcpm_key, cmd.tcpm_keylen);
+	}
+
+	addr = (union tcp_md5_addr *)&sin6->sin6_addr;
+
+	/* Don't allow keys for peers that have a matching TCP-AO key */
+	if (tcp_ao_do_lookup(sk, addr, AF_INET6, -1, -1, 0))
+		return -EKEYREJECTED;
 
-	return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin6->sin6_addr,
-			      AF_INET6, prefixlen, l3index, flags,
+	return tcp_md5_do_add(sk, addr, AF_INET6, prefixlen, l3index, flags,
 			      cmd.tcpm_key, cmd.tcpm_keylen);
 }
 
@@ -1902,6 +1914,7 @@  static const struct tcp_sock_af_ops tcp_sock_ipv6_specific = {
 	.md5_parse	=	tcp_v6_parse_md5_keys,
 #endif
 #ifdef CONFIG_TCP_AO
+	.ao_lookup	=	tcp_v6_ao_lookup,
 	.ao_parse	=	tcp_v6_parse_ao,
 #endif
 };
@@ -1933,6 +1946,7 @@  static const struct tcp_sock_af_ops tcp_sock_ipv6_mapped_specific = {
 	.md5_parse	=	tcp_v6_parse_md5_keys,
 #endif
 #ifdef CONFIG_TCP_AO
+	.ao_lookup	=	tcp_v6_ao_lookup,
 	.ao_parse	=	tcp_v6_parse_ao,
 #endif
 };