From patchwork Wed Sep 9 09:42:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pablo Neira Ayuso X-Patchwork-Id: 261266 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=-12.7 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=ham 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 6A8F7C43461 for ; Wed, 9 Sep 2020 09:45:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 24DD921D79 for ; Wed, 9 Sep 2020 09:45:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730339AbgIIJpY (ORCPT ); Wed, 9 Sep 2020 05:45:24 -0400 Received: from correo.us.es ([193.147.175.20]:34802 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726738AbgIIJm3 (ORCPT ); Wed, 9 Sep 2020 05:42:29 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 206172EFEA9 for ; Wed, 9 Sep 2020 11:42:27 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 0F6B0DA7B6 for ; Wed, 9 Sep 2020 11:42:27 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id 043E7DA796; Wed, 9 Sep 2020 11:42:27 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 69A98DA84A; Wed, 9 Sep 2020 11:42:24 +0200 (CEST) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Wed, 09 Sep 2020 11:42:24 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from localhost.localdomain (unknown [90.77.255.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: pneira@us.es) by entrada.int (Postfix) with ESMTPSA id 3E9594301DE3; Wed, 9 Sep 2020 11:42:24 +0200 (CEST) X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org Subject: [PATCH 01/13] netfilter: ip6t_NPT: rewrite addresses in ICMPv6 original packet Date: Wed, 9 Sep 2020 11:42:07 +0200 Message-Id: <20200909094219.17732-2-pablo@netfilter.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200909094219.17732-1-pablo@netfilter.org> References: <20200909094219.17732-1-pablo@netfilter.org> MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Michael Zhou 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 Signed-off-by: Pablo Neira Ayuso --- net/ipv6/netfilter/ip6t_NPT.c | 39 +++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) diff --git a/net/ipv6/netfilter/ip6t_NPT.c b/net/ipv6/netfilter/ip6t_NPT.c index 9ee077bf4f49..787c74aa85e3 100644 --- a/net/ipv6/netfilter/ip6t_NPT.c +++ b/net/ipv6/netfilter/ip6t_NPT.c @@ -77,16 +77,43 @@ static bool ip6t_npt_map_pfx(const struct ip6t_npt_tginfo *npt, return true; } +static struct ipv6hdr *icmpv6_bounced_ipv6hdr(struct sk_buff *skb, + struct ipv6hdr *_bounced_hdr) +{ + if (ipv6_hdr(skb)->nexthdr != IPPROTO_ICMPV6) + return NULL; + + if (!icmpv6_is_err(icmp6_hdr(skb)->icmp6_type)) + return NULL; + + return skb_header_pointer(skb, + skb_transport_offset(skb) + sizeof(struct icmp6hdr), + sizeof(struct ipv6hdr), + _bounced_hdr); +} + 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 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 = icmpv6_bounced_ipv6hdr(skb, &_bounced_hdr); + 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 +121,24 @@ 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 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 = icmpv6_bounced_ipv6hdr(skb, &_bounced_hdr); + 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; }