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syzbot reported a division by 0 bug in the netfilter nat code:
divide error: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 4168 Comm: syzkaller034710 Not tainted 4.16.0-rc1+ #309
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:nf_nat_l4proto_unique_tuple+0x291/0x530
net/netfilter/nf_nat_proto_common.c:88
RSP: 0018:ffff8801b2466778 EFLAGS: 00010246
RAX: 000000000000f153 RBX: ffff8801b2466dd8 RCX: ffff8801b2466c7c
RDX: 0000000000000000 RSI: ffff8801b2466c58 RDI: ffff8801db5293ac
RBP: ffff8801b24667d8 R08: ffff8801b8ba6dc0 R09: ffffffff88af5900
R10: ffff8801b24666f0 R11: 0000000000000000 R12: 000000002990f153
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8801b2466c7c
FS: 00000000017e3880(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000208fdfe4 CR3: 00000001b5340002 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
dccp_unique_tuple+0x40/0x50 net/netfilter/nf_nat_proto_dccp.c:30
get_unique_tuple+0xc28/0x1c10 net/netfilter/nf_nat_core.c:362
nf_nat_setup_info+0x1c2/0xe00 net/netfilter/nf_nat_core.c:406
nf_nat_redirect_ipv6+0x306/0x730 net/netfilter/nf_nat_redirect.c:124
redirect_tg6+0x7f/0xb0 net/netfilter/xt_REDIRECT.c:34
ip6t_do_table+0xc2a/0x1a30 net/ipv6/netfilter/ip6_tables.c:365
ip6table_nat_do_chain+0x65/0x80 net/ipv6/netfilter/ip6table_nat.c:41
nf_nat_ipv6_fn+0x594/0xa80 net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:302
nf_nat_ipv6_local_fn+0x33/0x5d0
net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:407
ip6table_nat_local_fn+0x2c/0x40 net/ipv6/netfilter/ip6table_nat.c:69
nf_hook_entry_hookfn include/linux/netfilter.h:120 [inline]
nf_hook_slow+0xba/0x1a0 net/netfilter/core.c:483
nf_hook include/linux/netfilter.h:243 [inline]
NF_HOOK include/linux/netfilter.h:286 [inline]
ip6_xmit+0x10ec/0x2260 net/ipv6/ip6_output.c:277
inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
dccp_transmit_skb+0x9ac/0x10f0 net/dccp/output.c:142
dccp_connect+0x369/0x670 net/dccp/output.c:564
dccp_v6_connect+0xe17/0x1bf0 net/dccp/ipv6.c:946
__inet_stream_connect+0x2d4/0xf00 net/ipv4/af_inet.c:620
inet_stream_connect+0x58/0xa0 net/ipv4/af_inet.c:684
SYSC_connect+0x213/0x4a0 net/socket.c:1639
SyS_connect+0x24/0x30 net/socket.c:1620
do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x441c69
RSP: 002b:00007ffe50cc0be8 EFLAGS: 00000217 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000441c69
RDX: 000000000000001c RSI: 00000000208fdfe4 RDI: 0000000000000003
RBP: 00000000006cc018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000538 R11: 0000000000000217 R12: 0000000000403590
R13: 0000000000403620 R14: 0000000000000000 R15: 0000000000000000
Code: 48 89 f0 83 e0 07 83 c0 01 38 d0 7c 08 84 d2 0f 85 46 02 00 00 48 8b
45 c8 44 0f b7 20 e8 88 97 04 fd 31 d2 41 0f b7 c4 4c 89 f9 <41> f7 f6 48
c1 e9 03 48 b8 00 00 00 00 00 fc ff df 0f b6 0c 01
RIP: nf_nat_l4proto_unique_tuple+0x291/0x530
net/netfilter/nf_nat_proto_common.c:88 RSP: ffff8801b2466778
The problem is that currently we don't have any check on the
configured port range. A port range == -1 triggers the bug, while
other negative values may require a very long time to complete the
following loop.
This commit addresses the issue swapping the two ends on negative
ranges. The check is performed in nf_nat_l4proto_unique_tuple() since
the nft nat loads the port values from nft registers at runtime.
v1 -> v2: use the correct 'Fixes' tag
v2 -> v3: update commit message, drop unneeded READ_ONCE()
Fixes: 5b1158e909ec ("[NETFILTER]: Add NAT support for nf_conntrack")
Reported-by: syzbot+8012e198bd037f4871e5@syzkaller.appspotmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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replace:
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
with
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
replace:
#if !defined(CONFIG_NF_NAT) && !defined(CONFIG_NF_NAT_MODULE)
with
#if !IS_ENABLED(CONFIG_NF_NAT)
replace:
#if !defined(CONFIG_NF_CONNTRACK) && !defined(CONFIG_NF_CONNTRACK_MODULE)
with
#if !IS_ENABLED(CONFIG_NF_CONNTRACK)
And add missing:
IS_ENABLED(CONFIG_NF_CT_NETLINK)
in net/ipv{4,6}/netfilter/nf_nat_l3proto_ipv{4,6}.c
Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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We currently use prandom_u32() for allocation of ports in tcp bind(0)
and udp code. In case of plain SNAT we try to keep the ports as is
or increment on collision.
SNAT --random mode does use per-destination incrementing port
allocation. As a recent paper pointed out in [1] that this mode of
port allocation makes it possible to an attacker to find the randomly
allocated ports through a timing side-channel in a socket overloading
attack conducted through an off-path attacker.
So, NF_NAT_RANGE_PROTO_RANDOM actually weakens the port randomization
in regard to the attack described in this paper. As we need to keep
compatibility, add another flag called NF_NAT_RANGE_PROTO_RANDOM_FULLY
that would replace the NF_NAT_RANGE_PROTO_RANDOM hash-based port
selection algorithm with a simple prandom_u32() in order to mitigate
this attack vector. Note that the lfsr113's internal state is
periodically reseeded by the kernel through a local secure entropy
source.
More details can be found in [1], the basic idea is to send bursts
of packets to a socket to overflow its receive queue and measure
the latency to detect a possible retransmit when the port is found.
Because of increasing ports to given destination and port, further
allocations can be predicted. This information could then be used by
an attacker for e.g. for cache-poisoning, NS pinning, and degradation
of service attacks against DNS servers [1]:
The best defense against the poisoning attacks is to properly
deploy and validate DNSSEC; DNSSEC provides security not only
against off-path attacker but even against MitM attacker. We hope
that our results will help motivate administrators to adopt DNSSEC.
However, full DNSSEC deployment make take significant time, and
until that happens, we recommend short-term, non-cryptographic
defenses. We recommend to support full port randomisation,
according to practices recommended in [2], and to avoid
per-destination sequential port allocation, which we show may be
vulnerable to derandomisation attacks.
Joint work between Hannes Frederic Sowa and Daniel Borkmann.
[1] https://sites.google.com/site/hayashulman/files/NIC-derandomisation.pdf
[2] http://arxiv.org/pdf/1205.5190v1.pdf
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Convert the IPv4 NAT implementation to a protocol independent core and
address family specific modules.
Signed-off-by: Patrick McHardy <kaber@trash.net>
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