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if_ovpn: cope with loops

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User misconfiguration may lead to routing loops where we try to send the tunnel
packet into the tunnel. This eventually leads to stack overflows and panics.

Avoid this using if_tunnel_check_nesting(), which will drop the packet if we're
looping or we hit three layers of nested tunnels.

MFC after:	1 week
Sponsored by:	Rubicon Communications, LLC ("Netgate")
This commit is contained in:
Kristof Provost 2024-05-13 12:06:47 +02:00
parent 421025a274
commit 59a6666ec9
2 changed files with 17 additions and 0 deletions
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9
sys/net/if_ovpn.c
View File

@ -255,6 +255,7 @@ static const char ovpnname[] = "ovpn";
static const char ovpngroupname[] = "openvpn";
static MALLOC_DEFINE(M_OVPN, ovpnname, "OpenVPN DCO Interface");
#define MTAG_OVPN_LOOP 0x6f76706e /* ovpn */
SYSCTL_DECL(_net_link);
static SYSCTL_NODE(_net_link, IFT_OTHER, openvpn, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
@ -1854,6 +1855,14 @@ ovpn_transmit_to_peer(struct ifnet *ifp, struct mbuf *m,
if (af != 0)
BPF_MTAP2(ifp, &af, sizeof(af), m);
if (__predict_false(if_tunnel_check_nesting(ifp, m, MTAG_OVPN_LOOP, 3))) {
if (_ovpn_lock_trackerp != NULL)
OVPN_RUNLOCK(sc);
OVPN_COUNTER_ADD(sc, lost_data_pkts_out, 1);
m_freem(m);
return (ELOOP);
}
len = m->m_pkthdr.len;
MPASS(len <= ifp->if_mtu);

8
tests/sys/net/if_ovpn/if_ovpn.sh
View File

@ -95,6 +95,10 @@ atf_test_case "4in4" "cleanup"
echo 'foo' | jexec b nc -u -w 2 192.0.2.1 1194
atf_check -s exit:0 -o ignore jexec b ping -c 3 198.51.100.1
# Test routing loop protection
jexec b route add 192.0.2.1 198.51.100.1
atf_check -s exit:2 -o ignore jexec b ping -t 1 -c 1 198.51.100.1
}
4in4_cleanup()
@ -404,6 +408,10 @@ atf_test_case "6in6" "cleanup"
atf_check -s exit:0 -o ignore jexec b ping6 -c 3 2001:db8:1::1
atf_check -s exit:0 -o ignore jexec b ping6 -c 3 -z 16 2001:db8:1::1
# Test routing loop protection
jexec b route add -6 2001:db8::1 2001:db8:1::1
atf_check -s exit:2 -o ignore jexec b ping6 -t 1 -c 3 2001:db8:1::1
}
6in6_cleanup()