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netfilter: nat: fix icmp id randomization

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Sven Auhagen reported that a 2nd ping request will fail if 'fully-random'
mode is used.

Reason is that if no proto information is given, min/max are both 0,
so we set the icmp id to 0 instead of chosing a random value between
0 and 65535.

Update test case as well to catch this, without fix this yields:
[..]
ERROR: cannot ping ns1 from ns2 with ip masquerade fully-random (attempt 2)
ERROR: cannot ping ns1 from ns2 with ipv6 masquerade fully-random (attempt 2)

... becaus 2nd ping clashes with existing 'id 0' icmp conntrack and gets
dropped.

Fixes: 203f2e7820 ("netfilter: nat: remove l4proto->unique_tuple")
Reported-by: Sven Auhagen <sven.auhagen@voleatech.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2019-04-09 14:45:20 +02:00 • committed by Pablo Neira Ayuso
parent 33d1c01817
commit 5bdac418f3
2 changed files with 35 additions and 12 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

11
net/netfilter/nf_nat_core.c
View file

@ -415,9 +415,14 @@ static void nf_nat_l4proto_unique_tuple(struct nf_conntrack_tuple *tuple,
case IPPROTO_ICMPV6:
/* id is same for either direction... */
keyptr = &tuple->src.u.icmp.id;
min = range->min_proto.icmp.id;
range_size = ntohs(range->max_proto.icmp.id) -
ntohs(range->min_proto.icmp.id) + 1;
if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED)) {
min = 0;
range_size = 65536;
} else {
min = ntohs(range->min_proto.icmp.id);
range_size = ntohs(range->max_proto.icmp.id) -
ntohs(range->min_proto.icmp.id) + 1;
}
goto find_free_id;
#if IS_ENABLED(CONFIG_NF_CT_PROTO_GRE)
case IPPROTO_GRE:

36
tools/testing/selftests/netfilter/nft_nat.sh
View file

@ -321,6 +321,7 @@ EOF
test_masquerade6()
{
local natflags=$1
local lret=0
ip netns exec ns0 sysctl net.ipv6.conf.all.forwarding=1 > /dev/null
@ -354,13 +355,13 @@ ip netns exec ns0 nft -f - <<EOF
table ip6 nat {
chain postrouting {
type nat hook postrouting priority 0; policy accept;
meta oif veth0 masquerade
meta oif veth0 masquerade $natflags
}
}
EOF
ip netns exec ns2 ping -q -c 1 dead:1::99 > /dev/null # ping ns2->ns1
if [ $? -ne 0 ] ; then
echo "ERROR: cannot ping ns1 from ns2 with active ipv6 masquerading"
echo "ERROR: cannot ping ns1 from ns2 with active ipv6 masquerade $natflags"
lret=1
fi
@ -397,19 +398,26 @@ EOF
fi
done
ip netns exec ns2 ping -q -c 1 dead:1::99 > /dev/null # ping ns2->ns1
if [ $? -ne 0 ] ; then
echo "ERROR: cannot ping ns1 from ns2 with active ipv6 masquerade $natflags (attempt 2)"
lret=1
fi
ip netns exec ns0 nft flush chain ip6 nat postrouting
if [ $? -ne 0 ]; then
echo "ERROR: Could not flush ip6 nat postrouting" 1>&2
lret=1
fi
test $lret -eq 0 && echo "PASS: IPv6 masquerade for ns2"
test $lret -eq 0 && echo "PASS: IPv6 masquerade $natflags for ns2"
return $lret
}
test_masquerade()
{
local natflags=$1
local lret=0
ip netns exec ns0 sysctl net.ipv4.conf.veth0.forwarding=1 > /dev/null
@ -417,7 +425,7 @@ test_masquerade()
ip netns exec ns2 ping -q -c 1 10.0.1.99 > /dev/null # ping ns2->ns1
if [ $? -ne 0 ] ; then
echo "ERROR: canot ping ns1 from ns2"
echo "ERROR: cannot ping ns1 from ns2 $natflags"
lret=1
fi
@ -443,13 +451,13 @@ ip netns exec ns0 nft -f - <<EOF
table ip nat {
chain postrouting {
type nat hook postrouting priority 0; policy accept;
meta oif veth0 masquerade
meta oif veth0 masquerade $natflags
}
}
EOF
ip netns exec ns2 ping -q -c 1 10.0.1.99 > /dev/null # ping ns2->ns1
if [ $? -ne 0 ] ; then
echo "ERROR: cannot ping ns1 from ns2 with active ip masquerading"
echo "ERROR: cannot ping ns1 from ns2 with active ip masquere $natflags"
lret=1
fi
@ -485,13 +493,19 @@ EOF
fi
done
ip netns exec ns2 ping -q -c 1 10.0.1.99 > /dev/null # ping ns2->ns1
if [ $? -ne 0 ] ; then
echo "ERROR: cannot ping ns1 from ns2 with active ip masquerade $natflags (attempt 2)"
lret=1
fi
ip netns exec ns0 nft flush chain ip nat postrouting
if [ $? -ne 0 ]; then
echo "ERROR: Could not flush nat postrouting" 1>&2
lret=1
fi
test $lret -eq 0 && echo "PASS: IP masquerade for ns2"
test $lret -eq 0 && echo "PASS: IP masquerade $natflags for ns2"
return $lret
}
@ -750,8 +764,12 @@ test_local_dnat
test_local_dnat6
reset_counters
test_masquerade
test_masquerade6
test_masquerade ""
test_masquerade6 ""
reset_counters
test_masquerade "fully-random"
test_masquerade6 "fully-random"
reset_counters
test_redirect