linux-kernel - [PATCH v5 4/5] net/tcp: Don't add key with non-matching VRF on connected sockets

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Message-ID: <20231204190044.450107-5-dima@arista.com>
Date:   Mon,  4 Dec 2023 19:00:43 +0000
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>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Francesco Ruggeri <fruggeri05@...il.com>,
        Salam Noureddine <noureddine@...sta.com>,
        Simon Horman <horms@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH v5 4/5] net/tcp: Don't add key with non-matching VRF on connected sockets

If the connection was established, don't allow adding TCP-AO keys that
don't match the peer. Currently, there are checks for ip-address
matching, but L3 index check is missing. Add it to restrict userspace
shooting itself somewhere.

Yet, nothing restricts the CAP_NET_RAW user from trying to shoot
themselves by performing setsockopt(SO_BINDTODEVICE) or
setsockopt(SO_BINDTOIFINDEX) over an established TCP-AO connection.
So, this is just "minimum effort" to potentially save someone's
debugging time, rather than a full restriction on doing weird things.

Fixes: 248411b8cb89 ("net/tcp: Wire up l3index to TCP-AO")
Signed-off-by: Dmitry Safonov <dima@...sta.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp_ao.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index c8be1d526eac..18dacfef7a07 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -1608,6 +1608,15 @@ static int tcp_ao_add_cmd(struct sock *sk, unsigned short int family,
 		if (!dev || !l3index)
 			return -EINVAL;
 
+		if (!bound_dev_if || bound_dev_if != cmd.ifindex) {
+			/* tcp_ao_established_key() doesn't expect having
+			 * non peer-matching key on an established TCP-AO
+			 * connection.
+			 */
+			if (!((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE)))
+				return -EINVAL;
+		}
+
 		/* It's still possible to bind after adding keys or even
 		 * re-bind to a different dev (with CAP_NET_RAW).
 		 * So, no reason to return error here, rather try to be
-- 
2.43.0