![Pablo Neira Ayuso](/assets/img/avatar_default.png)
Users cannot forge malformed IPv4/IPv6 headers via raw sockets that they
can inject into the stack. Specifically, not for IPv4 since 55888dfb6b
("AF_RAW: Augment raw_send_hdrinc to expand skb to fit iphdr->ihl
(v2)"). IPv6 raw sockets also ensure that packets have a well-formed
IPv6 header available in the skbuff.
At quick glance, br_netfilter also validates layer 3 headers and it
drops malformed both IPv4 and IPv6 packets.
Therefore, let's remove this defensive check all over the place.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
151 lines
3.6 KiB
C
151 lines
3.6 KiB
C
/*
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* This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
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*
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* Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
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* Copyright (C) 2000-2004 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/module.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netdevice.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <net/sock.h>
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#include <net/route.h>
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#include <linux/ip.h>
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#include <net/ip.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
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MODULE_DESCRIPTION("iptables mangle table");
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#define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
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(1 << NF_INET_LOCAL_IN) | \
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(1 << NF_INET_FORWARD) | \
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(1 << NF_INET_LOCAL_OUT) | \
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(1 << NF_INET_POST_ROUTING))
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static int __net_init iptable_mangle_table_init(struct net *net);
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static const struct xt_table packet_mangler = {
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.name = "mangle",
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.valid_hooks = MANGLE_VALID_HOOKS,
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.me = THIS_MODULE,
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.af = NFPROTO_IPV4,
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.priority = NF_IP_PRI_MANGLE,
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.table_init = iptable_mangle_table_init,
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};
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static unsigned int
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ipt_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state)
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{
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unsigned int ret;
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const struct iphdr *iph;
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u_int8_t tos;
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__be32 saddr, daddr;
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u_int32_t mark;
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int err;
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/* Save things which could affect route */
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mark = skb->mark;
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iph = ip_hdr(skb);
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saddr = iph->saddr;
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daddr = iph->daddr;
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tos = iph->tos;
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ret = ipt_do_table(skb, state, state->net->ipv4.iptable_mangle);
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/* Reroute for ANY change. */
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if (ret != NF_DROP && ret != NF_STOLEN) {
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iph = ip_hdr(skb);
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if (iph->saddr != saddr ||
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iph->daddr != daddr ||
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skb->mark != mark ||
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iph->tos != tos) {
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err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
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if (err < 0)
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ret = NF_DROP_ERR(err);
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}
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}
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return ret;
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}
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/* The work comes in here from netfilter.c. */
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static unsigned int
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iptable_mangle_hook(void *priv,
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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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if (state->hook == NF_INET_LOCAL_OUT)
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return ipt_mangle_out(skb, state);
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return ipt_do_table(skb, state, state->net->ipv4.iptable_mangle);
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}
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static struct nf_hook_ops *mangle_ops __read_mostly;
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static int __net_init iptable_mangle_table_init(struct net *net)
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{
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struct ipt_replace *repl;
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int ret;
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if (net->ipv4.iptable_mangle)
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return 0;
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repl = ipt_alloc_initial_table(&packet_mangler);
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if (repl == NULL)
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return -ENOMEM;
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ret = ipt_register_table(net, &packet_mangler, repl, mangle_ops,
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&net->ipv4.iptable_mangle);
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kfree(repl);
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return ret;
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}
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static void __net_exit iptable_mangle_net_exit(struct net *net)
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{
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if (!net->ipv4.iptable_mangle)
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return;
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ipt_unregister_table(net, net->ipv4.iptable_mangle, mangle_ops);
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net->ipv4.iptable_mangle = NULL;
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}
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static struct pernet_operations iptable_mangle_net_ops = {
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.exit = iptable_mangle_net_exit,
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};
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static int __init iptable_mangle_init(void)
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{
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int ret;
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mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook);
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if (IS_ERR(mangle_ops)) {
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ret = PTR_ERR(mangle_ops);
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return ret;
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}
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ret = register_pernet_subsys(&iptable_mangle_net_ops);
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if (ret < 0) {
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kfree(mangle_ops);
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return ret;
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}
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ret = iptable_mangle_table_init(&init_net);
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if (ret) {
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unregister_pernet_subsys(&iptable_mangle_net_ops);
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kfree(mangle_ops);
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}
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return ret;
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}
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static void __exit iptable_mangle_fini(void)
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{
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unregister_pernet_subsys(&iptable_mangle_net_ops);
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kfree(mangle_ops);
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}
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module_init(iptable_mangle_init);
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module_exit(iptable_mangle_fini);
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