LXR linux/net/netfilter/nf_conntrack_proto

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* (C) 1999-2001 Paul `Rusty' Russell
   3 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   4 * (C) 2006-2010 Patrick McHardy <kaber@trash.net>
   5 */
   6
   7#include <linux/types.h>
   8#include <linux/timer.h>
   9#include <linux/netfilter.h>
  10#include <linux/in.h>
  11#include <linux/icmp.h>
  12#include <linux/seq_file.h>
  13#include <net/ip.h>
  14#include <net/checksum.h>
  15#include <linux/netfilter_ipv4.h>
  16#include <net/netfilter/nf_conntrack_tuple.h>
  17#include <net/netfilter/nf_conntrack_l4proto.h>
  18#include <net/netfilter/nf_conntrack_core.h>
  19#include <net/netfilter/nf_conntrack_timeout.h>
  20#include <net/netfilter/nf_conntrack_zones.h>
  21#include <net/netfilter/nf_log.h>
  22
  23#include "nf_internals.h"
  24
  25static const unsigned int nf_ct_icmp_timeout = 30*HZ;
  26
  27bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
  28                       struct net *net, struct nf_conntrack_tuple *tuple)
  29{
  30        const struct icmphdr *hp;
  31        struct icmphdr _hdr;
  32
  33        hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  34        if (hp == NULL)
  35                return false;
  36
  37        tuple->dst.u.icmp.type = hp->type;
  38        tuple->src.u.icmp.id = hp->un.echo.id;
  39        tuple->dst.u.icmp.code = hp->code;
  40
  41        return true;
  42}
  43
  44/* Add 1; spaces filled with 0. */
  45static const u_int8_t invmap[] = {
  46        [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  47        [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  48        [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  49        [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  50        [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  51        [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  52        [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  53        [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
  54};
  55
  56bool nf_conntrack_invert_icmp_tuple(struct nf_conntrack_tuple *tuple,
  57                                    const struct nf_conntrack_tuple *orig)
  58{
  59        if (orig->dst.u.icmp.type >= sizeof(invmap) ||
  60            !invmap[orig->dst.u.icmp.type])
  61                return false;
  62
  63        tuple->src.u.icmp.id = orig->src.u.icmp.id;
  64        tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  65        tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  66        return true;
  67}
  68
  69/* Returns verdict for packet, or -1 for invalid. */
  70int nf_conntrack_icmp_packet(struct nf_conn *ct,
  71                             struct sk_buff *skb,
  72                             enum ip_conntrack_info ctinfo,
  73                             const struct nf_hook_state *state)
  74{
  75        /* Do not immediately delete the connection after the first
  76           successful reply to avoid excessive conntrackd traffic
  77           and also to handle correctly ICMP echo reply duplicates. */
  78        unsigned int *timeout = nf_ct_timeout_lookup(ct);
  79        static const u_int8_t valid_new[] = {
  80                [ICMP_ECHO] = 1,
  81                [ICMP_TIMESTAMP] = 1,
  82                [ICMP_INFO_REQUEST] = 1,
  83                [ICMP_ADDRESS] = 1
  84        };
  85
  86        if (state->pf != NFPROTO_IPV4)
  87                return -NF_ACCEPT;
  88
  89        if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
  90            !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
  91                /* Can't create a new ICMP `conn' with this. */
  92                pr_debug("icmp: can't create new conn with type %u\n",
  93                         ct->tuplehash[0].tuple.dst.u.icmp.type);
  94                nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
  95                return -NF_ACCEPT;
  96        }
  97
  98        if (!timeout)
  99                timeout = &nf_icmp_pernet(nf_ct_net(ct))->timeout;
 100
 101        nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
 102        return NF_ACCEPT;
 103}
 104
 105/* Check inner header is related to any of the existing connections */
 106int nf_conntrack_inet_error(struct nf_conn *tmpl, struct sk_buff *skb,
 107                            unsigned int dataoff,
 108                            const struct nf_hook_state *state,
 109                            u8 l4proto, union nf_inet_addr *outer_daddr)
 110{
 111        struct nf_conntrack_tuple innertuple, origtuple;
 112        const struct nf_conntrack_tuple_hash *h;
 113        const struct nf_conntrack_zone *zone;
 114        enum ip_conntrack_info ctinfo;
 115        struct nf_conntrack_zone tmp;
 116        union nf_inet_addr *ct_daddr;
 117        enum ip_conntrack_dir dir;
 118        struct nf_conn *ct;
 119
 120        WARN_ON(skb_nfct(skb));
 121        zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
 122
 123        /* Are they talking about one of our connections? */
 124        if (!nf_ct_get_tuplepr(skb, dataoff,
 125                               state->pf, state->net, &origtuple))
 126                return -NF_ACCEPT;
 127
 128        /* Ordinarily, we'd expect the inverted tupleproto, but it's
 129           been preserved inside the ICMP. */
 130        if (!nf_ct_invert_tuple(&innertuple, &origtuple))
 131                return -NF_ACCEPT;
 132
 133        h = nf_conntrack_find_get(state->net, zone, &innertuple);
 134        if (!h)
 135                return -NF_ACCEPT;
 136
 137        /* Consider: A -> T (=This machine) -> B
 138         *   Conntrack entry will look like this:
 139         *      Original:  A->B
 140         *      Reply:     B->T (SNAT case) OR A
 141         *
 142         * When this function runs, we got packet that looks like this:
 143         * iphdr|icmphdr|inner_iphdr|l4header (tcp, udp, ..).
 144         *
 145         * Above nf_conntrack_find_get() makes lookup based on inner_hdr,
 146         * so we should expect that destination of the found connection
 147         * matches outer header destination address.
 148         *
 149         * In above example, we can consider these two cases:
 150         *  1. Error coming in reply direction from B or M (middle box) to
 151         *     T (SNAT case) or A.
 152         *     Inner saddr will be B, dst will be T or A.
 153         *     The found conntrack will be reply tuple (B->T/A).
 154         *  2. Error coming in original direction from A or M to B.
 155         *     Inner saddr will be A, inner daddr will be B.
 156         *     The found conntrack will be original tuple (A->B).
 157         *
 158         * In both cases, conntrack[dir].dst == inner.dst.
 159         *
 160         * A bogus packet could look like this:
 161         *   Inner: B->T
 162         *   Outer: B->X (other machine reachable by T).
 163         *
 164         * In this case, lookup yields connection A->B and will
 165         * set packet from B->X as *RELATED*, even though no connection
 166         * from X was ever seen.
 167         */
 168        ct = nf_ct_tuplehash_to_ctrack(h);
 169        dir = NF_CT_DIRECTION(h);
 170        ct_daddr = &ct->tuplehash[dir].tuple.dst.u3;
 171        if (!nf_inet_addr_cmp(outer_daddr, ct_daddr)) {
 172                if (state->pf == AF_INET) {
 173                        nf_l4proto_log_invalid(skb, state,
 174                                               l4proto,
 175                                               "outer daddr %pI4 != inner %pI4",
 176                                               &outer_daddr->ip, &ct_daddr->ip);
 177                } else if (state->pf == AF_INET6) {
 178                        nf_l4proto_log_invalid(skb, state,
 179                                               l4proto,
 180                                               "outer daddr %pI6 != inner %pI6",
 181                                               &outer_daddr->ip6, &ct_daddr->ip6);
 182                }
 183                nf_ct_put(ct);
 184                return -NF_ACCEPT;
 185        }
 186
 187        ctinfo = IP_CT_RELATED;
 188        if (dir == IP_CT_DIR_REPLY)
 189                ctinfo += IP_CT_IS_REPLY;
 190
 191        /* Update skb to refer to this connection */
 192        nf_ct_set(skb, ct, ctinfo);
 193        return NF_ACCEPT;
 194}
 195
 196static void icmp_error_log(const struct sk_buff *skb,
 197                           const struct nf_hook_state *state,
 198                           const char *msg)
 199{
 200        nf_l4proto_log_invalid(skb, state, IPPROTO_ICMP, "%s", msg);
 201}
 202
 203/* Small and modified version of icmp_rcv */
 204int nf_conntrack_icmpv4_error(struct nf_conn *tmpl,
 205                              struct sk_buff *skb, unsigned int dataoff,
 206                              const struct nf_hook_state *state)
 207{
 208        union nf_inet_addr outer_daddr;
 209        const struct icmphdr *icmph;
 210        struct icmphdr _ih;
 211
 212        /* Not enough header? */
 213        icmph = skb_header_pointer(skb, dataoff, sizeof(_ih), &_ih);
 214        if (icmph == NULL) {
 215                icmp_error_log(skb, state, "short packet");
 216                return -NF_ACCEPT;
 217        }
 218
 219        /* See nf_conntrack_proto_tcp.c */
 220        if (state->net->ct.sysctl_checksum &&
 221            state->hook == NF_INET_PRE_ROUTING &&
 222            nf_ip_checksum(skb, state->hook, dataoff, IPPROTO_ICMP)) {
 223                icmp_error_log(skb, state, "bad hw icmp checksum");
 224                return -NF_ACCEPT;
 225        }
 226
 227        /*
 228         *      18 is the highest 'known' ICMP type. Anything else is a mystery
 229         *
 230         *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 231         *                discarded.
 232         */
 233        if (icmph->type > NR_ICMP_TYPES) {
 234                icmp_error_log(skb, state, "invalid icmp type");
 235                return -NF_ACCEPT;
 236        }
 237
 238        /* Need to track icmp error message? */
 239        if (!icmp_is_err(icmph->type))
 240                return NF_ACCEPT;
 241
 242        memset(&outer_daddr, 0, sizeof(outer_daddr));
 243        outer_daddr.ip = ip_hdr(skb)->daddr;
 244
 245        dataoff += sizeof(*icmph);
 246        return nf_conntrack_inet_error(tmpl, skb, dataoff, state,
 247                                       IPPROTO_ICMP, &outer_daddr);
 248}
 249
 250#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 251
 252#include <linux/netfilter/nfnetlink.h>
 253#include <linux/netfilter/nfnetlink_conntrack.h>
 254
 255static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 256                                const struct nf_conntrack_tuple *t)
 257{
 258        if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
 259            nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
 260            nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code))
 261                goto nla_put_failure;
 262        return 0;
 263
 264nla_put_failure:
 265        return -1;
 266}
 267
 268static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 269        [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 270        [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 271        [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 272};
 273
 274static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 275                                struct nf_conntrack_tuple *tuple,
 276                                u_int32_t flags)
 277{
 278        if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_TYPE)) {
 279                if (!tb[CTA_PROTO_ICMP_TYPE])
 280                        return -EINVAL;
 281
 282                tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 283                if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
 284                    !invmap[tuple->dst.u.icmp.type])
 285                        return -EINVAL;
 286        }
 287
 288        if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_CODE)) {
 289                if (!tb[CTA_PROTO_ICMP_CODE])
 290                        return -EINVAL;
 291
 292                tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 293        }
 294
 295        if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_ID)) {
 296                if (!tb[CTA_PROTO_ICMP_ID])
 297                        return -EINVAL;
 298
 299                tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 300        }
 301
 302        return 0;
 303}
 304
 305static unsigned int icmp_nlattr_tuple_size(void)
 306{
 307        static unsigned int size __read_mostly;
 308
 309        if (!size)
 310                size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
 311
 312        return size;
 313}
 314#endif
 315
 316#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 317
 318#include <linux/netfilter/nfnetlink.h>
 319#include <linux/netfilter/nfnetlink_cttimeout.h>
 320
 321static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
 322                                      struct net *net, void *data)
 323{
 324        unsigned int *timeout = data;
 325        struct nf_icmp_net *in = nf_icmp_pernet(net);
 326
 327        if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
 328                if (!timeout)
 329                        timeout = &in->timeout;
 330                *timeout =
 331                        ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
 332        } else if (timeout) {
 333                /* Set default ICMP timeout. */
 334                *timeout = in->timeout;
 335        }
 336        return 0;
 337}
 338
 339static int
 340icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 341{
 342        const unsigned int *timeout = data;
 343
 344        if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
 345                goto nla_put_failure;
 346        return 0;
 347
 348nla_put_failure:
 349        return -ENOSPC;
 350}
 351
 352static const struct nla_policy
 353icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
 354        [CTA_TIMEOUT_ICMP_TIMEOUT]      = { .type = NLA_U32 },
 355};
 356#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 357
 358void nf_conntrack_icmp_init_net(struct net *net)
 359{
 360        struct nf_icmp_net *in = nf_icmp_pernet(net);
 361
 362        in->timeout = nf_ct_icmp_timeout;
 363}
 364
 365const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
 366{
 367        .l4proto                = IPPROTO_ICMP,
 368#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 369        .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 370        .nlattr_tuple_size      = icmp_nlattr_tuple_size,
 371        .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 372        .nla_policy             = icmp_nla_policy,
 373#endif
 374#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 375        .ctnl_timeout           = {
 376                .nlattr_to_obj  = icmp_timeout_nlattr_to_obj,
 377                .obj_to_nlattr  = icmp_timeout_obj_to_nlattr,
 378                .nlattr_max     = CTA_TIMEOUT_ICMP_MAX,
 379                .obj_size       = sizeof(unsigned int),
 380                .nla_policy     = icmp_timeout_nla_policy,
 381        },
 382#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 383};
 384