net/netfilter/nf_conntrack_proto_icmp.c

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