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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3FCD4C433F5 for ; Fri, 13 May 2022 21:44:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1384772AbiEMVoH (ORCPT ); Fri, 13 May 2022 17:44:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1384749AbiEMVny (ORCPT ); Fri, 13 May 2022 17:43:54 -0400 Received: from mail.netfilter.org (mail.netfilter.org [217.70.188.207]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 33C212F006; Fri, 13 May 2022 14:43:53 -0700 (PDT) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org, pabeni@redhat.com Subject: [PATCH net-next 17/17] netfilter: conntrack: skip verification of zero UDP checksum Date: Fri, 13 May 2022 23:43:29 +0200 Message-Id: <20220513214329.1136459-18-pablo@netfilter.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220513214329.1136459-1-pablo@netfilter.org> References: <20220513214329.1136459-1-pablo@netfilter.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org From: Kevin Mitchell The checksum is optional for UDP packets. However nf_reject would previously require a valid checksum to elicit a response such as ICMP_DEST_UNREACH. Add some logic to nf_reject_verify_csum to determine if a UDP packet has a zero checksum and should therefore not be verified. Signed-off-by: Kevin Mitchell Signed-off-by: Pablo Neira Ayuso --- include/net/netfilter/nf_reject.h | 21 +++++++++++++++++---- net/ipv4/netfilter/nf_reject_ipv4.c | 10 +++++++--- net/ipv6/netfilter/nf_reject_ipv6.c | 4 ++-- 3 files changed, 26 insertions(+), 9 deletions(-) diff --git a/include/net/netfilter/nf_reject.h b/include/net/netfilter/nf_reject.h index 9051c3a0c8e7..7c669792fb9c 100644 --- a/include/net/netfilter/nf_reject.h +++ b/include/net/netfilter/nf_reject.h @@ -5,12 +5,28 @@ #include #include -static inline bool nf_reject_verify_csum(__u8 proto) +static inline bool nf_reject_verify_csum(struct sk_buff *skb, int dataoff, + __u8 proto) { /* Skip protocols that don't use 16-bit one's complement checksum * of the entire payload. */ switch (proto) { + /* Protocols with optional checksums. */ + case IPPROTO_UDP: { + const struct udphdr *udp_hdr; + struct udphdr _udp_hdr; + + udp_hdr = skb_header_pointer(skb, dataoff, + sizeof(_udp_hdr), + &_udp_hdr); + if (!udp_hdr || udp_hdr->check) + return true; + + return false; + } + case IPPROTO_GRE: + /* Protocols with other integrity checks. */ case IPPROTO_AH: case IPPROTO_ESP: @@ -19,9 +35,6 @@ static inline bool nf_reject_verify_csum(__u8 proto) /* Protocols with partial checksums. */ case IPPROTO_UDPLITE: case IPPROTO_DCCP: - - /* Protocols with optional checksums. */ - case IPPROTO_GRE: return false; } return true; diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c index 4eed5afca392..918c61fda0f3 100644 --- a/net/ipv4/netfilter/nf_reject_ipv4.c +++ b/net/ipv4/netfilter/nf_reject_ipv4.c @@ -80,6 +80,7 @@ struct sk_buff *nf_reject_skb_v4_unreach(struct net *net, struct iphdr *niph; struct icmphdr *icmph; unsigned int len; + int dataoff; __wsum csum; u8 proto; @@ -99,10 +100,11 @@ struct sk_buff *nf_reject_skb_v4_unreach(struct net *net, if (pskb_trim_rcsum(oldskb, ntohs(ip_hdr(oldskb)->tot_len))) return NULL; + dataoff = ip_hdrlen(oldskb); proto = ip_hdr(oldskb)->protocol; if (!skb_csum_unnecessary(oldskb) && - nf_reject_verify_csum(proto) && + nf_reject_verify_csum(oldskb, dataoff, proto) && nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), proto)) return NULL; @@ -311,6 +313,7 @@ EXPORT_SYMBOL_GPL(nf_send_reset); void nf_send_unreach(struct sk_buff *skb_in, int code, int hook) { struct iphdr *iph = ip_hdr(skb_in); + int dataoff = ip_hdrlen(skb_in); u8 proto = iph->protocol; if (iph->frag_off & htons(IP_OFFSET)) @@ -320,12 +323,13 @@ void nf_send_unreach(struct sk_buff *skb_in, int code, int hook) nf_reject_fill_skb_dst(skb_in) < 0) return; - if (skb_csum_unnecessary(skb_in) || !nf_reject_verify_csum(proto)) { + if (skb_csum_unnecessary(skb_in) || + !nf_reject_verify_csum(skb_in, dataoff, proto)) { icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); return; } - if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0) + if (nf_ip_checksum(skb_in, hook, dataoff, proto) == 0) icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); } EXPORT_SYMBOL_GPL(nf_send_unreach); diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c index dffeaaaadcde..f61d4f18e1cf 100644 --- a/net/ipv6/netfilter/nf_reject_ipv6.c +++ b/net/ipv6/netfilter/nf_reject_ipv6.c @@ -31,7 +31,7 @@ static bool nf_reject_v6_csum_ok(struct sk_buff *skb, int hook) if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0) return false; - if (!nf_reject_verify_csum(proto)) + if (!nf_reject_verify_csum(skb, thoff, proto)) return true; return nf_ip6_checksum(skb, hook, thoff, proto) == 0; @@ -388,7 +388,7 @@ static bool reject6_csum_ok(struct sk_buff *skb, int hook) if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0) return false; - if (!nf_reject_verify_csum(proto)) + if (!nf_reject_verify_csum(skb, thoff, proto)) return true; return nf_ip6_checksum(skb, hook, thoff, proto) == 0; -- 2.30.2