From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDCE8C433E2 for ; Mon, 20 Jul 2020 13:23:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C231620729 for ; Mon, 20 Jul 2020 13:23:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727019AbgGTNXa (ORCPT ); Mon, 20 Jul 2020 09:23:30 -0400 Received: from [216.151.45.106] ([216.151.45.106]:55950 "EHLO localhost" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726030AbgGTNXa (ORCPT ); Mon, 20 Jul 2020 09:23:30 -0400 X-Greylist: delayed 358 seconds by postgrey-1.27 at vger.kernel.org; Mon, 20 Jul 2020 09:23:29 EDT Received: by localhost (Postfix, from userid 1000) id 2AAA52C95D; Mon, 20 Jul 2020 23:17:31 +1000 (AEST) From: Michael Zhou To: netfilter-devel@vger.kernel.org Cc: Michael Zhou Subject: [PATCH] net/ipv6/netfilter/ip6t_NPT: rewrite addresses in ICMPv6 original packet Date: Mon, 20 Jul 2020 23:17:01 +1000 Message-Id: <20200720131701.17941-1-mzhou@cse.unsw.edu.au> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Detect and rewrite a prefix embedded in an ICMPv6 original packet that was rewritten by a corresponding DNPT/SNPT rule so it will be recognised by the host that sent the original packet. Example Rules in effect on the 1:2:3:4::/64 + 5:6:7:8::/64 side router: * SNPT src-pfx 1:2:3:4::/64 dst-pfx 5:6:7:8::/64 * DNPT src-pfx 5:6:7:8::/64 dst-pfx 1:2:3:4::/64 No rules on the 9:a:b:c::/64 side. 1. 1:2:3:4::1 sends UDP packet to 9:a:b:c::1 2. Router applies SNPT changing src to 5:6:7:8::ffef::1 3. 9:a:b:c::1 receives packet with (src 5:6:7:8::ffef::1 dst 9:a:b:c::1) and replies with ICMPv6 port unreachable to 5:6:7:8::ffef::1, including original packet (src 5:6:7:8::ffef::1 dst 9:a:b:c::1) 4. Router forwards ICMPv6 packet with (src 9:a:b:c::1 dst 5:6:7:8::ffef::1) including original packet (src 5:6:7:8::ffef::1 dst 9:a:b:c::1) and applies DNPT changing dst to 1:2:3:4::1 5. 1:2:3:4::1 receives ICMPv6 packet with (src 9:a:b:c::1 dst 1:2:3:4::1) including original packet (src 5:6:7:8::ffef::1 dst 9:a:b:c::1). It doesn't recognise the original packet as the src doesn't match anything it originally sent With this change, at step 4, DNPT will also rewrite the original packet src to 1:2:3:4::1, so at step 5, 1:2:3:4::1 will recognise the ICMPv6 error and provide feedback to the application properly. Conversely, SNPT will help when ICMPv6 errors are sent from the translated network. 1. 9:a:b:c::1 sends UDP packet to 5:6:7:8::ffef::1 2. Router applies DNPT changing dst to 1:2:3:4::1 3. 1:2:3:4::1 receives packet with (src 9:a:b:c::1 dst 1:2:3:4::1) and replies with ICMPv6 port unreachable to 9:a:b:c::1 including original packet (src 9:a:b:c::1 dst 1:2:3:4::1) 4. Router forwards ICMPv6 packet with (src 1:2:3:4::1 dst 9:a:b:c::1) including original packet (src 9:a:b:c::1 dst 1:2:3:4::1) and applies SNPT changing src to 5:6:7:8::ffef::1 5. 9:a:b:c::1 receives ICMPv6 packet with (src 5:6:7:8::ffef::1 dst 9:a:b:c::1) including original packet (src 9:a:b:c::1 dst 1:2:3:4::1). It doesn't recognise the original packet as the dst doesn't match anything it already sent The change to SNPT means the ICMPv6 original packet dst will be rewritten to 5:6:7:8::ffef::1 in step 4, allowing the error to be properly recognised in step 5. Signed-off-by: Michael Zhou --- net/ipv6/netfilter/ip6t_NPT.c | 37 +++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/net/ipv6/netfilter/ip6t_NPT.c b/net/ipv6/netfilter/ip6t_NPT.c index 9ee077bf4f49..b25e786607ed 100644 --- a/net/ipv6/netfilter/ip6t_NPT.c +++ b/net/ipv6/netfilter/ip6t_NPT.c @@ -77,16 +77,42 @@ static bool ip6t_npt_map_pfx(const struct ip6t_npt_tginfo *npt, return true; } +static struct ipv6hdr *ip6t_npt_icmpv6_bounced_ipv6hdr(struct sk_buff *skb) +{ + if (ipv6_hdr(skb)->nexthdr != IPPROTO_ICMPV6) + return NULL; + + if (!icmpv6_is_err(icmp6_hdr(skb)->icmp6_type)) + return NULL; + + if ((const unsigned char *)&icmp6_hdr(skb)[1] + sizeof(struct ipv6hdr) > + skb_tail_pointer(skb)) + return NULL; + + return (struct ipv6hdr *)&icmp6_hdr(skb)[1]; +} + static unsigned int ip6t_snpt_tg(struct sk_buff *skb, const struct xt_action_param *par) { const struct ip6t_npt_tginfo *npt = par->targinfo; + struct ipv6hdr *bounced_hdr; + struct in6_addr bounced_pfx; if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->saddr)) { icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD, offsetof(struct ipv6hdr, saddr)); return NF_DROP; } + + /* rewrite dst addr of bounced packet which was sent to dst range */ + bounced_hdr = ip6t_npt_icmpv6_bounced_ipv6hdr(skb); + if (bounced_hdr) { + ipv6_addr_prefix(&bounced_pfx, &bounced_hdr->daddr, npt->src_pfx_len); + if (ipv6_addr_cmp(&bounced_pfx, &npt->src_pfx.in6) == 0) + ip6t_npt_map_pfx(npt, &bounced_hdr->daddr); + } + return XT_CONTINUE; } @@ -94,12 +120,23 @@ static unsigned int ip6t_dnpt_tg(struct sk_buff *skb, const struct xt_action_param *par) { const struct ip6t_npt_tginfo *npt = par->targinfo; + struct ipv6hdr *bounced_hdr; + struct in6_addr bounced_pfx; if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->daddr)) { icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD, offsetof(struct ipv6hdr, daddr)); return NF_DROP; } + + /* rewrite src addr of bounced packet which was sent from dst range */ + bounced_hdr = ip6t_npt_icmpv6_bounced_ipv6hdr(skb); + if (bounced_hdr) { + ipv6_addr_prefix(&bounced_pfx, &bounced_hdr->saddr, npt->src_pfx_len); + if (ipv6_addr_cmp(&bounced_pfx, &npt->src_pfx.in6) == 0) + ip6t_npt_map_pfx(npt, &bounced_hdr->saddr); + } + return XT_CONTINUE; } -- 2.25.1