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if_ovpn: fix use-after-free of mbuf

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m_unshare() can return a new mbuf pointer. We update the 'm' pointer in
ovpn_udp_input(), but if we decide to pass on the packet (e.g. because it's for
an unknown peer) the caller (udp_append()) continues with the old 'm' pointer,
eventually resulting in a use-after-free.

Re-order operations in ovpn_udp_input() so that we don't modify the 'm' pointer
until we're committed to keeping the packet.

PR:		283426
Test case by:	takahiro.kurosawa@gmail.com
MFC after:	2 weeks
Sponsored by:	Rubicon Communications, LLC ("Netgate")
This commit is contained in:
Kristof Provost 2025-04-01 15:19:26 +02:00 committed by Franco Fichtner
parent d61f5e3dd9
commit f93d01fa41
2 changed files with 87 additions and 6 deletions
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12
sys/net/if_ovpn.c
View File

@ -2255,12 +2255,6 @@ ovpn_udp_input(struct mbuf *m, int off, struct inpcb *inp,
M_ASSERTPKTHDR(m);
m = m_unshare(m, M_NOWAIT);
if (m == NULL) {
OVPN_COUNTER_ADD(sc, nomem_data_pkts_in, 1);
return (true);
}
OVPN_COUNTER_ADD(sc, transport_bytes_received, m->m_pkthdr.len - off);
ohdrlen = sizeof(*ohdr) - sizeof(ohdr->auth_tag);
@ -2288,6 +2282,12 @@ ovpn_udp_input(struct mbuf *m, int off, struct inpcb *inp,
return (false);
}
m = m_unshare(m, M_NOWAIT);
if (m == NULL) {
OVPN_COUNTER_ADD(sc, nomem_data_pkts_in, 1);
return (true);
}
m = m_pullup(m, off + sizeof(*uhdr) + ohdrlen);
if (m == NULL) {
OVPN_RUNLOCK(sc);

81
tests/sys/net/if_ovpn/if_ovpn.sh
View File

@ -106,6 +106,86 @@ atf_test_case "4in4" "cleanup"
ovpn_cleanup
}
atf_test_case "bz283426" "cleanup"
bz283426_head()
{
atf_set descr 'FreeBSD Bugzilla 283426'
atf_set require.user root
atf_set require.progs openvpn python3
}
bz283426_body()
{
ovpn_init
l=$(vnet_mkepair)
vnet_mkjail a ${l}a
jexec a ifconfig ${l}a 192.0.2.1/24 up
vnet_mkjail b ${l}b
jexec b ifconfig ${l}b 192.0.2.2/24 up
# Sanity check
atf_check -s exit:0 -o ignore jexec a ping -c 1 192.0.2.2
ovpn_start a "
dev ovpn0
dev-type tun
proto udp4
cipher AES-256-GCM
auth SHA256
bind 0.0.0.0:1194
server 198.51.100.0 255.255.255.0
ca $(atf_get_srcdir)/ca.crt
cert $(atf_get_srcdir)/server.crt
key $(atf_get_srcdir)/server.key
dh $(atf_get_srcdir)/dh.pem
mode server
script-security 2
auth-user-pass-verify /usr/bin/true via-env
topology subnet
keepalive 100 600
"
ovpn_start b "
dev tun0
dev-type tun
client
remote 192.0.2.1
auth-user-pass $(atf_get_srcdir)/user.pass
ca $(atf_get_srcdir)/ca.crt
cert $(atf_get_srcdir)/client.crt
key $(atf_get_srcdir)/client.key
dh $(atf_get_srcdir)/dh.pem
keepalive 100 600
"
# Give the tunnel time to come up
sleep 10
atf_check -s exit:0 -o ignore jexec b ping -c 1 198.51.100.1
# Send a broadcast packet in the outer link.
echo "import socket as sk
s = sk.socket(sk.AF_INET, sk.SOCK_DGRAM)
s.setsockopt(sk.SOL_SOCKET, sk.SO_BROADCAST, 1)
s.sendto(b'x' * 1000, ('192.0.2.255', 1194))" | jexec b python3
atf_check -s exit:0 -o ignore jexec b ping -c 3 198.51.100.1
}
bz283426_cleanup()
{
ovpn_cleanup
}
atf_test_case "4mapped" "cleanup"
4mapped_head()
{
@ -1033,6 +1113,7 @@ gcm_128_cleanup()
atf_init_test_cases()
{
atf_add_test_case "4in4"
atf_add_test_case "bz283426"
atf_add_test_case "4mapped"
atf_add_test_case "6in4"
atf_add_test_case "6in6"