net/netfilter/nf_conntrack_proto_icmp.c

   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
  25 static const unsigned int nf_ct_icmp_timeout = 30*HZ;
  26
  27 bool 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. */
  45 static 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
  56 bool 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. */
  70 int 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 */
 106 int 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->net, state->pf,
 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->net, state->pf,
 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
 196 static 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->net, state->pf,
 201                                IPPROTO_ICMP, "%s", msg);
 202 }
 203
 204 /* Small and modified version of icmp_rcv */
 205 int nf_conntrack_icmpv4_error(struct nf_conn *tmpl,
 206                               struct sk_buff *skb, unsigned int dataoff,
 207                               const struct nf_hook_state *state)
 208 {
 209         union nf_inet_addr outer_daddr;
 210         const struct icmphdr *icmph;
 211         struct icmphdr _ih;
 212
 213         /* Not enough header? */
 214         icmph = skb_header_pointer(skb, dataoff, sizeof(_ih), &_ih);
 215         if (icmph == NULL) {
 216                 icmp_error_log(skb, state, "short packet");
 217                 return -NF_ACCEPT;
 218         }
 219
 220         /* See nf_conntrack_proto_tcp.c */
 221         if (state->net->ct.sysctl_checksum &&
 222             state->hook == NF_INET_PRE_ROUTING &&
 223             nf_ip_checksum(skb, state->hook, dataoff, IPPROTO_ICMP)) {
 224                 icmp_error_log(skb, state, "bad hw icmp checksum");
 225                 return -NF_ACCEPT;
 226         }
 227
 228         /*
 229          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 230          *
 231          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 232          *                discarded.
 233          */
 234         if (icmph->type > NR_ICMP_TYPES) {
 235                 icmp_error_log(skb, state, "invalid icmp type");
 236                 return -NF_ACCEPT;
 237         }
 238
 239         /* Need to track icmp error message? */
 240         if (!icmp_is_err(icmph->type))
 241                 return NF_ACCEPT;
 242
 243         memset(&outer_daddr, 0, sizeof(outer_daddr));
 244         outer_daddr.ip = ip_hdr(skb)->daddr;
 245
 246         dataoff += sizeof(*icmph);
 247         return nf_conntrack_inet_error(tmpl, skb, dataoff, state,
 248                                        IPPROTO_ICMP, &outer_daddr);
 249 }
 250
 251 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 252
 253 #include <linux/netfilter/nfnetlink.h>
 254 #include <linux/netfilter/nfnetlink_conntrack.h>
 255
 256 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 257                                 const struct nf_conntrack_tuple *t)
 258 {
 259         if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
 260             nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
 261             nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code))
 262                 goto nla_put_failure;
 263         return 0;
 264
 265 nla_put_failure:
 266         return -1;
 267 }
 268
 269 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 270         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 271         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 272         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 273 };
 274
 275 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 276                                 struct nf_conntrack_tuple *tuple,
 277                                 u_int32_t flags)
 278 {
 279         if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_TYPE)) {
 280                 if (!tb[CTA_PROTO_ICMP_TYPE])
 281                         return -EINVAL;
 282
 283                 tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 284                 if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
 285                     !invmap[tuple->dst.u.icmp.type])
 286                         return -EINVAL;
 287         }
 288
 289         if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_CODE)) {
 290                 if (!tb[CTA_PROTO_ICMP_CODE])
 291                         return -EINVAL;
 292
 293                 tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 294         }
 295
 296         if (flags & CTA_FILTER_FLAG(CTA_PROTO_ICMP_ID)) {
 297                 if (!tb[CTA_PROTO_ICMP_ID])
 298                         return -EINVAL;
 299
 300                 tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 301         }
 302
 303         return 0;
 304 }
 305
 306 static unsigned int icmp_nlattr_tuple_size(void)
 307 {
 308         static unsigned int size __read_mostly;
 309
 310         if (!size)
 311                 size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
 312
 313         return size;
 314 }
 315 #endif
 316
 317 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 318
 319 #include <linux/netfilter/nfnetlink.h>
 320 #include <linux/netfilter/nfnetlink_cttimeout.h>
 321
 322 static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
 323                                       struct net *net, void *data)
 324 {
 325         unsigned int *timeout = data;
 326         struct nf_icmp_net *in = nf_icmp_pernet(net);
 327
 328         if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
 329                 if (!timeout)
 330                         timeout = &in->timeout;
 331                 *timeout =
 332                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
 333         } else if (timeout) {
 334                 /* Set default ICMP timeout. */
 335                 *timeout = in->timeout;
 336         }
 337         return 0;
 338 }
 339
 340 static int
 341 icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 342 {
 343         const unsigned int *timeout = data;
 344
 345         if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
 346                 goto nla_put_failure;
 347         return 0;
 348
 349 nla_put_failure:
 350         return -ENOSPC;
 351 }
 352
 353 static const struct nla_policy
 354 icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
 355         [CTA_TIMEOUT_ICMP_TIMEOUT]      = { .type = NLA_U32 },
 356 };
 357 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 358
 359 void nf_conntrack_icmp_init_net(struct net *net)
 360 {
 361         struct nf_icmp_net *in = nf_icmp_pernet(net);
 362
 363         in->timeout = nf_ct_icmp_timeout;
 364 }
 365
 366 const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
 367 {
 368         .l4proto                = IPPROTO_ICMP,
 369 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 370         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 371         .nlattr_tuple_size      = icmp_nlattr_tuple_size,
 372         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 373         .nla_policy             = icmp_nla_policy,
 374 #endif
 375 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 376         .ctnl_timeout           = {
 377                 .nlattr_to_obj  = icmp_timeout_nlattr_to_obj,
 378                 .obj_to_nlattr  = icmp_timeout_obj_to_nlattr,
 379                 .nlattr_max     = CTA_TIMEOUT_ICMP_MAX,
 380                 .obj_size       = sizeof(unsigned int),
 381                 .nla_policy     = icmp_timeout_nla_policy,
 382         },
 383 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 384 };