From 7fc38225363dd8f19e667ad7c77b63bc4a5c065d Mon Sep 17 00:00:00 2001 From: Alin Nastac Date: Wed, 13 Feb 2019 09:14:53 +0100 Subject: netfilter: reject: skip csum verification for protocols that don't support it Some protocols have other means to verify the payload integrity (AH, ESP, SCTP) while others are incompatible with nf_ip(6)_checksum implementation because checksum is either optional or might be partial (UDPLITE, DCCP, GRE). Because nf_ip(6)_checksum was used to validate the packets, ip(6)tables REJECT rules were not capable to generate ICMP(v6) errors for the protocols mentioned above. This commit also fixes the incorrect pseudo-header protocol used for IPv4 packets that carry other transport protocols than TCP or UDP (pseudo-header used protocol 0 iso the proper value). Signed-off-by: Alin Nastac Signed-off-by: Pablo Neira Ayuso --- include/net/netfilter/ipv4/nf_reject.h | 1 + include/net/netfilter/ipv6/nf_reject.h | 1 + include/net/netfilter/nf_reject.h | 27 +++++++++++++++++++++++++++ net/bridge/netfilter/nft_reject_bridge.c | 10 +++++----- net/ipv4/netfilter/nf_reject_ipv4.c | 9 ++------- net/ipv6/netfilter/nf_reject_ipv6.c | 3 +++ 6 files changed, 39 insertions(+), 12 deletions(-) create mode 100644 include/net/netfilter/nf_reject.h diff --git a/include/net/netfilter/ipv4/nf_reject.h b/include/net/netfilter/ipv4/nf_reject.h index 2eb43fcefc50..40e0e0623f46 100644 --- a/include/net/netfilter/ipv4/nf_reject.h +++ b/include/net/netfilter/ipv4/nf_reject.h @@ -5,6 +5,7 @@ #include #include #include +#include void nf_send_unreach(struct sk_buff *skb_in, int code, int hook); void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook); diff --git a/include/net/netfilter/ipv6/nf_reject.h b/include/net/netfilter/ipv6/nf_reject.h index 3a5a9a36a0b2..4a3ef9ebdf6f 100644 --- a/include/net/netfilter/ipv6/nf_reject.h +++ b/include/net/netfilter/ipv6/nf_reject.h @@ -3,6 +3,7 @@ #define _IPV6_NF_REJECT_H #include +#include void nf_send_unreach6(struct net *net, struct sk_buff *skb_in, unsigned char code, unsigned int hooknum); diff --git a/include/net/netfilter/nf_reject.h b/include/net/netfilter/nf_reject.h new file mode 100644 index 000000000000..221f877f29d1 --- /dev/null +++ b/include/net/netfilter/nf_reject.h @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _NF_REJECT_H +#define _NF_REJECT_H + +static inline bool nf_reject_verify_csum(__u8 proto) +{ + /* Skip protocols that don't use 16-bit one's complement checksum + * of the entire payload. + */ + switch (proto) { + /* Protocols with other integrity checks. */ + case IPPROTO_AH: + case IPPROTO_ESP: + case IPPROTO_SCTP: + + /* Protocols with partial checksums. */ + case IPPROTO_UDPLITE: + case IPPROTO_DCCP: + + /* Protocols with optional checksums. */ + case IPPROTO_GRE: + return false; + } + return true; +} + +#endif /* _NF_REJECT_H */ diff --git a/net/bridge/netfilter/nft_reject_bridge.c b/net/bridge/netfilter/nft_reject_bridge.c index 419e8edf23ba..1b1856744c80 100644 --- a/net/bridge/netfilter/nft_reject_bridge.c +++ b/net/bridge/netfilter/nft_reject_bridge.c @@ -125,13 +125,10 @@ static void nft_reject_br_send_v4_unreach(struct net *net, if (pskb_trim_rcsum(oldskb, ntohs(ip_hdr(oldskb)->tot_len))) return; - if (ip_hdr(oldskb)->protocol == IPPROTO_TCP || - ip_hdr(oldskb)->protocol == IPPROTO_UDP) - proto = ip_hdr(oldskb)->protocol; - else - proto = 0; + proto = ip_hdr(oldskb)->protocol; if (!skb_csum_unnecessary(oldskb) && + nf_reject_verify_csum(proto) && nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), proto)) return; @@ -234,6 +231,9 @@ static bool reject6_br_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)) + return true; + return nf_ip6_checksum(skb, hook, thoff, proto) == 0; } diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c index aa8304c618b8..7dc3c324b911 100644 --- a/net/ipv4/netfilter/nf_reject_ipv4.c +++ b/net/ipv4/netfilter/nf_reject_ipv4.c @@ -173,21 +173,16 @@ 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); - u8 proto; + u8 proto = iph->protocol; if (iph->frag_off & htons(IP_OFFSET)) return; - if (skb_csum_unnecessary(skb_in)) { + if (skb_csum_unnecessary(skb_in) || !nf_reject_verify_csum(proto)) { icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); return; } - if (iph->protocol == IPPROTO_TCP || iph->protocol == IPPROTO_UDP) - proto = iph->protocol; - else - proto = 0; - if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0) icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); } diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c index b9c8a763c863..02e9228641e0 100644 --- a/net/ipv6/netfilter/nf_reject_ipv6.c +++ b/net/ipv6/netfilter/nf_reject_ipv6.c @@ -233,6 +233,9 @@ 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)) + return true; + return nf_ip6_checksum(skb, hook, thoff, proto) == 0; } -- cgit v1.2.3-59-g8ed1b