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deedb59039
This work adds a direction parameter to netfilter zones, so identity
separation can be performed only in original/reply or both directions
(default). This basically opens up the possibility of doing NAT with
conflicting IP address/port tuples from multiple, isolated tenants
on a host (e.g. from a netns) without requiring each tenant to NAT
twice resp. to use its own dedicated IP address to SNAT to, meaning
overlapping tuples can be made unique with the zone identifier in
original direction, where the NAT engine will then allocate a unique
tuple in the commonly shared default zone for the reply direction.
In some restricted, local DNAT cases, also port redirection could be
used for making the reply traffic unique w/o requiring SNAT.
The consensus we've reached and discussed at NFWS and since the initial
implementation [1] was to directly integrate the direction meta data
into the existing zones infrastructure, as opposed to the ct->mark
approach we proposed initially.
As we pass the nf_conntrack_zone object directly around, we don't have
to touch all call-sites, but only those, that contain equality checks
of zones. Thus, based on the current direction (original or reply),
we either return the actual id, or the default NF_CT_DEFAULT_ZONE_ID.
CT expectations are direction-agnostic entities when expectations are
being compared among themselves, so we can only use the identifier
in this case.
Note that zone identifiers can not be included into the hash mix
anymore as they don't contain a "stable" value that would be equal
for both directions at all times, f.e. if only zone->id would
unconditionally be xor'ed into the table slot hash, then replies won't
find the corresponding conntracking entry anymore.
If no particular direction is specified when configuring zones, the
behaviour is exactly as we expect currently (both directions).
Support has been added for the CT netlink interface as well as the
x_tables raw CT target, which both already offer existing interfaces
to user space for the configuration of zones.
Below a minimal, simplified collision example (script in [2]) with
netperf sessions:
+--- tenant-1 ---+ mark := 1
| netperf |--+
+----------------+ | CT zone := mark [ORIGINAL]
[ip,sport] := X +--------------+ +--- gateway ---+
| mark routing |--| SNAT |-- ... +
+--------------+ +---------------+ |
+--- tenant-2 ---+ | ~~~|~~~
| netperf |--+ +-----------+ |
+----------------+ mark := 2 | netserver |------ ... +
[ip,sport] := X +-----------+
[ip,port] := Y
On the gateway netns, example:
iptables -t raw -A PREROUTING -j CT --zone mark --zone-dir ORIGINAL
iptables -t nat -A POSTROUTING -o <dev> -j SNAT --to-source <ip> --random-fully
iptables -t mangle -A PREROUTING -m conntrack --ctdir ORIGINAL -j CONNMARK --save-mark
iptables -t mangle -A POSTROUTING -m conntrack --ctdir REPLY -j CONNMARK --restore-mark
conntrack dump from gateway netns:
netperf -H 10.1.1.2 -t TCP_STREAM -l60 -p12865,5555 from each tenant netns
tcp 6 431995 ESTABLISHED src=40.1.1.1 dst=10.1.1.2 sport=5555 dport=12865 zone-orig=1
src=10.1.1.2 dst=10.1.1.1 sport=12865 dport=1024
[ASSURED] mark=1 secctx=system_u:object_r:unlabeled_t:s0 use=1
tcp 6 431994 ESTABLISHED src=40.1.1.1 dst=10.1.1.2 sport=5555 dport=12865 zone-orig=2
src=10.1.1.2 dst=10.1.1.1 sport=12865 dport=5555
[ASSURED] mark=2 secctx=system_u:object_r:unlabeled_t:s0 use=1
tcp 6 299 ESTABLISHED src=40.1.1.1 dst=10.1.1.2 sport=39438 dport=33768 zone-orig=1
src=10.1.1.2 dst=10.1.1.1 sport=33768 dport=39438
[ASSURED] mark=1 secctx=system_u:object_r:unlabeled_t:s0 use=1
tcp 6 300 ESTABLISHED src=40.1.1.1 dst=10.1.1.2 sport=32889 dport=40206 zone-orig=2
src=10.1.1.2 dst=10.1.1.1 sport=40206 dport=32889
[ASSURED] mark=2 secctx=system_u:object_r:unlabeled_t:s0 use=2
Taking this further, test script in [2] creates 200 tenants and runs
original-tuple colliding netperf sessions each. A conntrack -L dump in
the gateway netns also confirms 200 overlapping entries, all in ESTABLISHED
state as expected.
I also did run various other tests with some permutations of the script,
to mention some: SNAT in random/random-fully/persistent mode, no zones (no
overlaps), static zones (original, reply, both directions), etc.
[1] http://thread.gmane.org/gmane.comp.security.firewalls.netfilter.devel/57412/
[2] https://paste.fedoraproject.org/242835/65657871/
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
137 lines
3.3 KiB
C
137 lines
3.3 KiB
C
/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/types.h>
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#include <linux/ipv6.h>
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#include <linux/in6.h>
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#include <linux/netfilter.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/icmp.h>
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#include <linux/sysctl.h>
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#include <net/ipv6.h>
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#include <net/inet_frag.h>
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#include <linux/netfilter_ipv6.h>
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#include <linux/netfilter_bridge.h>
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#if IS_ENABLED(CONFIG_NF_CONNTRACK)
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_l4proto.h>
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#include <net/netfilter/nf_conntrack_l3proto.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
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#endif
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#include <net/netfilter/nf_conntrack_zones.h>
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#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
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static enum ip6_defrag_users nf_ct6_defrag_user(unsigned int hooknum,
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struct sk_buff *skb)
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{
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u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
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#if IS_ENABLED(CONFIG_NF_CONNTRACK)
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if (skb->nfct) {
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enum ip_conntrack_info ctinfo;
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const struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
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zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
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}
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#endif
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if (nf_bridge_in_prerouting(skb))
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return IP6_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id;
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if (hooknum == NF_INET_PRE_ROUTING)
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return IP6_DEFRAG_CONNTRACK_IN + zone_id;
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else
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return IP6_DEFRAG_CONNTRACK_OUT + zone_id;
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}
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static unsigned int ipv6_defrag(const struct nf_hook_ops *ops,
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struct sk_buff *skb,
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const struct nf_hook_state *state)
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{
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struct sk_buff *reasm;
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#if IS_ENABLED(CONFIG_NF_CONNTRACK)
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/* Previously seen (loopback)? */
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if (skb->nfct && !nf_ct_is_template((struct nf_conn *)skb->nfct))
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return NF_ACCEPT;
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#endif
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reasm = nf_ct_frag6_gather(skb, nf_ct6_defrag_user(ops->hooknum, skb));
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/* queued */
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if (reasm == NULL)
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return NF_STOLEN;
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/* error occurred or not fragmented */
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if (reasm == skb)
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return NF_ACCEPT;
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nf_ct_frag6_consume_orig(reasm);
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NF_HOOK_THRESH(NFPROTO_IPV6, ops->hooknum, state->sk, reasm,
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state->in, state->out,
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state->okfn, NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
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return NF_STOLEN;
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}
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static struct nf_hook_ops ipv6_defrag_ops[] = {
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{
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.hook = ipv6_defrag,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV6,
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.hooknum = NF_INET_PRE_ROUTING,
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.priority = NF_IP6_PRI_CONNTRACK_DEFRAG,
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},
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{
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.hook = ipv6_defrag,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV6,
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.hooknum = NF_INET_LOCAL_OUT,
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.priority = NF_IP6_PRI_CONNTRACK_DEFRAG,
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},
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};
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static int __init nf_defrag_init(void)
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{
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int ret = 0;
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ret = nf_ct_frag6_init();
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if (ret < 0) {
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pr_err("nf_defrag_ipv6: can't initialize frag6.\n");
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return ret;
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}
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ret = nf_register_hooks(ipv6_defrag_ops, ARRAY_SIZE(ipv6_defrag_ops));
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if (ret < 0) {
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pr_err("nf_defrag_ipv6: can't register hooks\n");
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goto cleanup_frag6;
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}
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return ret;
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cleanup_frag6:
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nf_ct_frag6_cleanup();
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return ret;
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}
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static void __exit nf_defrag_fini(void)
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{
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nf_unregister_hooks(ipv6_defrag_ops, ARRAY_SIZE(ipv6_defrag_ops));
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nf_ct_frag6_cleanup();
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}
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void nf_defrag_ipv6_enable(void)
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{
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}
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EXPORT_SYMBOL_GPL(nf_defrag_ipv6_enable);
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module_init(nf_defrag_init);
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module_exit(nf_defrag_fini);
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MODULE_LICENSE("GPL");
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