From: Alin Nastac <alin.nastac@xxxxxxxxx>
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 <alin.nastac@xxxxxxxxx>
---
include/net/netfilter/ipv4/nf_reject.h | 1 +
include/net/netfilter/ipv6/nf_reject.h | 1 +
include/net/netfilter/nf_reject.h | 26 ++++++++++++++++++++++++++
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, 38 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 2eb43fc..40e0e06 100644
--- a/include/net/netfilter/ipv4/nf_reject.h
+++ b/include/net/netfilter/ipv4/nf_reject.h
@@ -5,6 +5,7 @@
#include <linux/skbuff.h>
#include <net/ip.h>
#include <net/icmp.h>
+#include <net/netfilter/nf_reject.h>
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 3a5a9a3..4a3ef9e 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 <linux/icmpv6.h>
+#include <net/netfilter/nf_reject.h>
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 0000000..f327ded
--- /dev/null
+++ b/include/net/netfilter/nf_reject.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NF_REJECT_H
+#define _NF_REJECT_H
+
+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 419e8ed..1b18567 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 aa8304c..7dc3c32 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 b9c8a76..02e9228 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;
}
--
2.7.4
