ee586bbc28
tcp resets are never emitted if the packet that triggers the reject/reset has an invalid checksum. For icmp error responses there was no such check. It allows to distinguish icmp response generated via iptables -I INPUT -p udp --dport 42 -j REJECT and those emitted by network stack (won't respond if csum is invalid, REJECT does). Arguably its possible to avoid this by using conntrack and only using REJECT with -m conntrack NEW/RELATED. However, this doesn't work when connection tracking is not in use or when using nf_conntrack_checksum=0. Furthermore, sending errors in response to invalid csums doesn't make much sense so just add similar test as in nf_send_reset. Validate csum if needed and only send the response if it is ok. Reference: http://bugzilla.redhat.com/show_bug.cgi?id=1169829 Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
75 lines
2 KiB
C
75 lines
2 KiB
C
/*
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* Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
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* Copyright (c) 2013 Eric Leblond <eric@regit.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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* Development of this code funded by Astaro AG (http://www.astaro.com/)
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/netlink.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter/nf_tables.h>
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#include <net/netfilter/nf_tables.h>
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#include <net/netfilter/ipv4/nf_reject.h>
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#include <net/netfilter/nft_reject.h>
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static void nft_reject_ipv4_eval(const struct nft_expr *expr,
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struct nft_data data[NFT_REG_MAX + 1],
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const struct nft_pktinfo *pkt)
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{
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struct nft_reject *priv = nft_expr_priv(expr);
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switch (priv->type) {
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case NFT_REJECT_ICMP_UNREACH:
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nf_send_unreach(pkt->skb, priv->icmp_code,
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pkt->ops->hooknum);
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break;
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case NFT_REJECT_TCP_RST:
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nf_send_reset(pkt->skb, pkt->ops->hooknum);
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break;
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}
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data[NFT_REG_VERDICT].verdict = NF_DROP;
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}
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static struct nft_expr_type nft_reject_ipv4_type;
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static const struct nft_expr_ops nft_reject_ipv4_ops = {
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.type = &nft_reject_ipv4_type,
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.size = NFT_EXPR_SIZE(sizeof(struct nft_reject)),
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.eval = nft_reject_ipv4_eval,
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.init = nft_reject_init,
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.dump = nft_reject_dump,
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};
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static struct nft_expr_type nft_reject_ipv4_type __read_mostly = {
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.family = NFPROTO_IPV4,
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.name = "reject",
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.ops = &nft_reject_ipv4_ops,
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.policy = nft_reject_policy,
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.maxattr = NFTA_REJECT_MAX,
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.owner = THIS_MODULE,
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};
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static int __init nft_reject_ipv4_module_init(void)
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{
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return nft_register_expr(&nft_reject_ipv4_type);
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}
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static void __exit nft_reject_ipv4_module_exit(void)
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{
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nft_unregister_expr(&nft_reject_ipv4_type);
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}
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module_init(nft_reject_ipv4_module_init);
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module_exit(nft_reject_ipv4_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
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MODULE_ALIAS_NFT_AF_EXPR(AF_INET, "reject");
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