cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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arpt_mangle.c (2431B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* module that allows mangling of the arp payload */
      3#include <linux/module.h>
      4#include <linux/netfilter.h>
      5#include <linux/netfilter_arp/arpt_mangle.h>
      6#include <net/sock.h>
      7
      8MODULE_LICENSE("GPL");
      9MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
     10MODULE_DESCRIPTION("arptables arp payload mangle target");
     11
     12static unsigned int
     13target(struct sk_buff *skb, const struct xt_action_param *par)
     14{
     15	const struct arpt_mangle *mangle = par->targinfo;
     16	const struct arphdr *arp;
     17	unsigned char *arpptr;
     18	int pln, hln;
     19
     20	if (skb_ensure_writable(skb, skb->len))
     21		return NF_DROP;
     22
     23	arp = arp_hdr(skb);
     24	arpptr = skb_network_header(skb) + sizeof(*arp);
     25	pln = arp->ar_pln;
     26	hln = arp->ar_hln;
     27	/* We assume that pln and hln were checked in the match */
     28	if (mangle->flags & ARPT_MANGLE_SDEV) {
     29		if (ARPT_DEV_ADDR_LEN_MAX < hln ||
     30		   (arpptr + hln > skb_tail_pointer(skb)))
     31			return NF_DROP;
     32		memcpy(arpptr, mangle->src_devaddr, hln);
     33	}
     34	arpptr += hln;
     35	if (mangle->flags & ARPT_MANGLE_SIP) {
     36		if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
     37		   (arpptr + pln > skb_tail_pointer(skb)))
     38			return NF_DROP;
     39		memcpy(arpptr, &mangle->u_s.src_ip, pln);
     40	}
     41	arpptr += pln;
     42	if (mangle->flags & ARPT_MANGLE_TDEV) {
     43		if (ARPT_DEV_ADDR_LEN_MAX < hln ||
     44		   (arpptr + hln > skb_tail_pointer(skb)))
     45			return NF_DROP;
     46		memcpy(arpptr, mangle->tgt_devaddr, hln);
     47	}
     48	arpptr += hln;
     49	if (mangle->flags & ARPT_MANGLE_TIP) {
     50		if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
     51		   (arpptr + pln > skb_tail_pointer(skb)))
     52			return NF_DROP;
     53		memcpy(arpptr, &mangle->u_t.tgt_ip, pln);
     54	}
     55	return mangle->target;
     56}
     57
     58static int checkentry(const struct xt_tgchk_param *par)
     59{
     60	const struct arpt_mangle *mangle = par->targinfo;
     61
     62	if (mangle->flags & ~ARPT_MANGLE_MASK ||
     63	    !(mangle->flags & ARPT_MANGLE_MASK))
     64		return -EINVAL;
     65
     66	if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT &&
     67	   mangle->target != XT_CONTINUE)
     68		return -EINVAL;
     69	return 0;
     70}
     71
     72static struct xt_target arpt_mangle_reg __read_mostly = {
     73	.name		= "mangle",
     74	.family		= NFPROTO_ARP,
     75	.target		= target,
     76	.targetsize	= sizeof(struct arpt_mangle),
     77	.checkentry	= checkentry,
     78	.me		= THIS_MODULE,
     79};
     80
     81static int __init arpt_mangle_init(void)
     82{
     83	return xt_register_target(&arpt_mangle_reg);
     84}
     85
     86static void __exit arpt_mangle_fini(void)
     87{
     88	xt_unregister_target(&arpt_mangle_reg);
     89}
     90
     91module_init(arpt_mangle_init);
     92module_exit(arpt_mangle_fini);