// SPDX-License-Identifier: GPL-2.0-only
/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2004 Netfilter Core Team <[email protected]>
* (C) 2006-2010 Patrick McHardy <[email protected]>
*/
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/netfilter.h>
#include <linux/in.h>
#include <linux/icmp.h>
#include <linux/seq_file.h>
#include <net/ip.h>
#include <net/checksum.h>
#include <linux/netfilter_ipv4.h>
#include <net/netfilter/nf_conntrack_tuple.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_timeout.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <net/netfilter/nf_log.h>
#include "nf_internals.h"
static const unsigned int nf_ct_icmp_timeout = 30*HZ;
bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
struct net *net, struct nf_conntrack_tuple *tuple)
{
const struct icmphdr *hp;
struct icmphdr _hdr;
hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
if (hp == NULL)
return false;
tuple->dst.u.icmp.type = hp->type;
tuple->src.u.icmp.id = hp->un.echo.id;
tuple->dst.u.icmp.code = hp->code;
return true;
}
/* Add 1; spaces filled with 0. */
static const u_int8_t invmap[] = {
[ICMP_ECHO] = ICMP_ECHOREPLY + 1,
[ICMP_ECHOREPLY] = ICMP_ECHO + 1,
[ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
[ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
[ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
[ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
[ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
[ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
};
bool nf_conntrack_invert_icmp_tuple(struct nf_conntrack_tuple *tuple,
const struct nf_conntrack_tuple *orig)
{
if (orig->dst.u.icmp.type >= sizeof(invmap) ||
!invmap[orig->dst.u.icmp.type])
return false;
tuple->src.u.icmp.id = orig->src.u.icmp.id;
tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
return true;
}
/* Returns verdict for packet, or -1 for invalid. */
int nf_conntrack_icmp_packet(struct nf_conn *ct,
struct sk_buff *skb,
enum ip_conntrack_info ctinfo,
const struct nf_hook_state *state)
{
/* Do not immediately delete the connection after the first
successful reply to avoid excessive conntrackd traffic
and also to handle correctly ICMP echo reply duplicates. */
unsigned int *timeout = nf_ct_timeout_lookup(ct);
static const u_int8_t valid_new[] = {
[ICMP_ECHO] = 1,
[ICMP_TIMESTAMP] = 1,
[ICMP_INFO_REQUEST] = 1,
[ICMP_ADDRESS] = 1
};
if (state->pf != NFPROTO_IPV4)
return -NF_ACCEPT;
if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
!valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
/* Can't create a new ICMP `conn' with this. */
pr_debug("icmp: can't create new conn with type %u\n",
ct->tuplehash[0].tuple.dst.u.icmp.type);
nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
return -NF_ACCEPT;
}
if (!timeout)
timeout = &nf_icmp_pernet(nf_ct_net(ct))->timeout;
nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
return NF_ACCEPT;
}
/* Check inner header is related to any of the existing connections */
int nf_conntrack_inet_error(struct nf_conn *tmpl, struct sk_buff *skb,
unsigned int dataoff,
const struct nf_hook_state *state,
u8 l4proto, union nf_inet_addr *outer_daddr)
{
struct nf_conntrack_tuple innertuple, origtuple;
const struct nf_conntrack_tuple_hash *h;
const struct nf_conntrack_zone *zone;
enum ip_conntrack_info ctinfo;
struct nf_conntrack_zone tmp;
union nf_inet_addr *ct_daddr;
enum ip_conntrack_dir dir;
struct nf_conn *ct;
WARN_ON(skb_nfct(skb));
zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
/* Are they talking about one of our connections? */
if (!nf_ct_get_tuplepr(skb, dataoff,
state->pf, state->net, &origtuple))
return -NF_ACCEPT;
/* Ordinarily, we'd expect the inverted tupleproto, but it's
been preserved inside the ICMP. */
if (!nf_ct_invert_tuple(&innertuple, &origtuple))
return -NF_ACCEPT;
h = nf_conntrack_find_get(state->net, zone, &innertuple);
if (!h)
return -NF_ACCEPT;
/* Consider: A -> T (=This machine) -> B
* Conntrack entry will look like this:
* Original: A->B
* Reply: B->T (SNAT case) OR A
*
* When this function runs, we got packet that looks like this:
* iphdr|icmphdr|inner_iphdr|l4header (tcp, udp, ..).
*
* Above nf_conntrack_find_get() makes lookup based on inner_hdr,
* so we should expect that destination of the found connection
* matches outer header destination address.
*
* In above example, we can consider these two cases:
* 1. Error coming in reply direction from B or M (middle box) to
* T (SNAT case) or A.
* Inner saddr will be B, dst will be T or A.
* The found conntrack will be reply tuple (B->T/A).
* 2. Error coming in original direction from A or M to B.
* Inner saddr will be A, inner daddr will be B.
* The found conntrack will be original tuple (A->B).
*
* In both cases, conntrack[dir].dst == inner.dst.
*
* A bogus packet could look like this:
* Inner: B->T
* Outer: B->X (other machine reachable by T).
*
* In this case, lookup yields connection A->B and will
* set packet from B->X as *RELATED*, even though no connection
* from X was ever seen.
*/
ct = nf_ct_tuplehash_to_ctrack(h);
dir = NF_CT_DIRECTION(h);
ct_daddr = &ct->tuplehash[dir].tuple.dst.u3;
if (!nf_inet_addr_cmp(outer_daddr, ct_daddr)) {
if (state->pf == AF_INET) {
nf_l4proto_log_invalid(skb, state,
l4proto,
"outer daddr %pI4 != inner %pI4",
&outer_daddr->ip, &ct_daddr->ip);
} else if (state->pf == AF_INET6) {
nf_l4proto_log_invalid(skb, state,
l4proto,
"outer daddr %pI6 != inner %pI6",
&outer_daddr->ip6, &ct_daddr->ip6);
}
nf_ct_put(ct);
return -NF_ACCEPT;
}
ctinfo = IP_CT_RELATED;
if (dir == IP_CT_DIR_REPLY)
ctinfo += IP_CT_IS_REPLY;
/* Update skb to refer to this connection */
nf_ct_set(skb, ct, ctinfo);
return NF_ACCEPT;
}
static void icmp_error_log(const struct sk_buff *skb,
const struct nf_hook_state *state,
const char *msg)
{
nf_l4proto_log_invalid(skb, state, IPPROTO_ICMP, "%s", msg);
}
/* Small and modified version of icmp_rcv */
int nf_conntrack_icmpv4_error(struct nf_conn *tmpl,
struct sk_buff *skb, unsigned int dataoff,
const struct nf_hook_state *state)
{
union nf_inet_addr outer_daddr;
const struct icmphdr *icmph;
struct icmphdr _ih;
/* Not enough header? */
icmph = skb_header_pointer(skb, dataoff, sizeof(_ih), &_ih);
if (icmph == NULL) {
icmp_error_log(skb, state, "short packet");
return -NF_ACCEPT;
}
/* See nf_conntrack_proto_tcp.c */
if (state->net->ct.sysctl_checksum &&
state->hook == NF_INET_PRE_ROUTING &&
nf_ip_checksum(skb, state->hook, dataoff, IPPROTO_ICMP)) {
icmp_error_log(skb, state, "bad hw icmp checksum");
return -NF_ACCEPT;
}
/*
* 18 is the highest 'known' ICMP type. Anything else is a mystery
*
* RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
* discarded.
*/
if (icmph->type > NR_ICMP_TYPES) {
icmp_error_log(skb, state, "invalid icmp type");
return -NF_ACCEPT;
}
/* Need to track icmp error message? */
if (!icmp_is_err(icmph->type))
return NF_ACCEPT;
memset(&outer_daddr, 0, sizeof(outer_daddr));
outer_daddr.ip = ip_hdr(skb)->daddr;
dataoff += sizeof(*icmph);
return nf_conntrack_inet_error(tmpl, skb, dataoff, state,
IPPROTO_ICMP, &outer_daddr);
}
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_conntrack.h>
static int icmp_tuple_to_nlattr(struct sk_buff *skb,
const struct nf_conntrack_tuple *t)
{
if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code))
goto nla_put_failure;
return 0;
nla_put_failure:
return -1;
}
static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
[CTA_PROTO_ICMP_TYPE] = { .type = NLA_U8 },
[CTA_PROTO_ICMP_CODE] = { .type = NLA_U8 },
[CTA_PROTO_ICMP_ID] = { .type = NLA_U16 },
};
static int icmp_nlattr_to_tuple(struct nlattr *tb[],
struct nf_conntrack_tuple *tuple,
u_int32_t flags)
{
if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_TYPE)) {
if (!tb[CTA_PROTO_ICMP_TYPE])
return -EINVAL;
tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
!invmap[tuple->dst.u.icmp.type])
return -EINVAL;
}
if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_CODE)) {
if (!tb[CTA_PROTO_ICMP_CODE])
return -EINVAL;
tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
}
if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_ID)) {
if (!tb[CTA_PROTO_ICMP_ID])
return -EINVAL;
tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
}
return 0;
}
static unsigned int icmp_nlattr_tuple_size(void)
{
static unsigned int size __read_mostly;
if (!size)
size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
return size;
}
#endif
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_cttimeout.h>
static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
struct net *net, void *data)
{
unsigned int *timeout = data;
struct nf_icmp_net *in = nf_icmp_pernet(net);
if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
if (!timeout)
timeout = &in->timeout;
*timeout =
ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
} else if (timeout) {
/* Set default ICMP timeout. */
*timeout = in->timeout;
}
return 0;
}
static int
icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
{
const unsigned int *timeout = data;
if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
goto nla_put_failure;
return 0;
nla_put_failure:
return -ENOSPC;
}
static const struct nla_policy
icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
[CTA_TIMEOUT_ICMP_TIMEOUT] = { .type = NLA_U32 },
};
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
void nf_conntrack_icmp_init_net(struct net *net)
{
struct nf_icmp_net *in = nf_icmp_pernet(net);
in->timeout = nf_ct_icmp_timeout;
}
const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
{
.l4proto = IPPROTO_ICMP,
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
.tuple_to_nlattr = icmp_tuple_to_nlattr,
.nlattr_tuple_size = icmp_nlattr_tuple_size,
.nlattr_to_tuple = icmp_nlattr_to_tuple,
.nla_policy = icmp_nla_policy,
#endif
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
.ctnl_timeout = {
.nlattr_to_obj = icmp_timeout_nlattr_to_obj,
.obj_to_nlattr = icmp_timeout_obj_to_nlattr,
.nlattr_max = CTA_TIMEOUT_ICMP_MAX,
.obj_size = sizeof(unsigned int),
.nla_policy = icmp_timeout_nla_policy,
},
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
};
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