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 static 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 static bool icmp_invert_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 static int icmp_packet(struct nf_conn *ct,
  72                        struct sk_buff *skb,
  73                        unsigned int dataoff,
  74                        enum ip_conntrack_info ctinfo,
  75                        const struct nf_hook_state *state)
  76 {
  77         /* Do not immediately delete the connection after the first
  78            successful reply to avoid excessive conntrackd traffic
  79            and also to handle correctly ICMP echo reply duplicates. */
  80         unsigned int *timeout = nf_ct_timeout_lookup(ct);
  81         static const u_int8_t valid_new[] = {
  82                 [ICMP_ECHO] = 1,
  83                 [ICMP_TIMESTAMP] = 1,
  84                 [ICMP_INFO_REQUEST] = 1,
  85                 [ICMP_ADDRESS] = 1
  86         };
  87
  88         if (state->pf != NFPROTO_IPV4)
  89                 return -NF_ACCEPT;
  90
  91         if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
  92             !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
  93                 /* Can't create a new ICMP `conn' with this. */
  94                 pr_debug("icmp: can't create new conn with type %u\n",
  95                          ct->tuplehash[0].tuple.dst.u.icmp.type);
  96                 nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
  97                 return -NF_ACCEPT;
  98         }
  99
 100         if (!timeout)
 101                 timeout = &nf_icmp_pernet(nf_ct_net(ct))->timeout;
 102
 103         nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
 104         return NF_ACCEPT;
 105 }
 106
 107 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 108 static int
 109 icmp_error_message(struct nf_conn *tmpl, struct sk_buff *skb,
 110                    const struct nf_hook_state *state)
 111 {
 112         struct nf_conntrack_tuple innertuple, origtuple;
 113         const struct nf_conntrack_l4proto *innerproto;
 114         const struct nf_conntrack_tuple_hash *h;
 115         const struct nf_conntrack_zone *zone;
 116         enum ip_conntrack_info ctinfo;
 117         struct nf_conntrack_zone tmp;
 118
 119         WARN_ON(skb_nfct(skb));
 120         zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
 121
 122         /* Are they talking about one of our connections? */
 123         if (!nf_ct_get_tuplepr(skb,
 124                                skb_network_offset(skb) + ip_hdrlen(skb)
 125                                                        + sizeof(struct icmphdr),
 126                                PF_INET, state->net, &origtuple)) {
 127                 pr_debug("icmp_error_message: failed to get tuple\n");
 128                 return -NF_ACCEPT;
 129         }
 130
 131         /* rcu_read_lock()ed by nf_hook_thresh */
 132         innerproto = __nf_ct_l4proto_find(origtuple.dst.protonum);
 133
 134         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 135            been preserved inside the ICMP. */
 136         if (!nf_ct_invert_tuple(&innertuple, &origtuple, innerproto)) {
 137                 pr_debug("icmp_error_message: no match\n");
 138                 return -NF_ACCEPT;
 139         }
 140
 141         ctinfo = IP_CT_RELATED;
 142
 143         h = nf_conntrack_find_get(state->net, zone, &innertuple);
 144         if (!h) {
 145                 pr_debug("icmp_error_message: no match\n");
 146                 return -NF_ACCEPT;
 147         }
 148
 149         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 150                 ctinfo += IP_CT_IS_REPLY;
 151
 152         /* Update skb to refer to this connection */
 153         nf_ct_set(skb, nf_ct_tuplehash_to_ctrack(h), ctinfo);
 154         return NF_ACCEPT;
 155 }
 156
 157 static void icmp_error_log(const struct sk_buff *skb,
 158                            const struct nf_hook_state *state,
 159                            const char *msg)
 160 {
 161         nf_l4proto_log_invalid(skb, state->net, state->pf,
 162                                IPPROTO_ICMP, "%s", msg);
 163 }
 164
 165 /* Small and modified version of icmp_rcv */
 166 int nf_conntrack_icmpv4_error(struct nf_conn *tmpl,
 167                               struct sk_buff *skb, unsigned int dataoff,
 168                               const struct nf_hook_state *state)
 169 {
 170         const struct icmphdr *icmph;
 171         struct icmphdr _ih;
 172
 173         /* Not enough header? */
 174         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 175         if (icmph == NULL) {
 176                 icmp_error_log(skb, state, "short packet");
 177                 return -NF_ACCEPT;
 178         }
 179
 180         /* See ip_conntrack_proto_tcp.c */
 181         if (state->net->ct.sysctl_checksum &&
 182             state->hook == NF_INET_PRE_ROUTING &&
 183             nf_ip_checksum(skb, state->hook, dataoff, 0)) {
 184                 icmp_error_log(skb, state, "bad hw icmp checksum");
 185                 return -NF_ACCEPT;
 186         }
 187
 188         /*
 189          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 190          *
 191          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 192          *                discarded.
 193          */
 194         if (icmph->type > NR_ICMP_TYPES) {
 195                 icmp_error_log(skb, state, "invalid icmp type");
 196                 return -NF_ACCEPT;
 197         }
 198
 199         /* Need to track icmp error message? */
 200         if (icmph->type != ICMP_DEST_UNREACH &&
 201             icmph->type != ICMP_SOURCE_QUENCH &&
 202             icmph->type != ICMP_TIME_EXCEEDED &&
 203             icmph->type != ICMP_PARAMETERPROB &&
 204             icmph->type != ICMP_REDIRECT)
 205                 return NF_ACCEPT;
 206
 207         return icmp_error_message(tmpl, skb, state);
 208 }
 209
 210 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 211
 212 #include <linux/netfilter/nfnetlink.h>
 213 #include <linux/netfilter/nfnetlink_conntrack.h>
 214
 215 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 216                                 const struct nf_conntrack_tuple *t)
 217 {
 218         if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
 219             nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
 220             nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code))
 221                 goto nla_put_failure;
 222         return 0;
 223
 224 nla_put_failure:
 225         return -1;
 226 }
 227
 228 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 229         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 230         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 231         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 232 };
 233
 234 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 235                                 struct nf_conntrack_tuple *tuple)
 236 {
 237         if (!tb[CTA_PROTO_ICMP_TYPE] ||
 238             !tb[CTA_PROTO_ICMP_CODE] ||
 239             !tb[CTA_PROTO_ICMP_ID])
 240                 return -EINVAL;
 241
 242         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 243         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 244         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 245
 246         if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
 247             !invmap[tuple->dst.u.icmp.type])
 248                 return -EINVAL;
 249
 250         return 0;
 251 }
 252
 253 static unsigned int icmp_nlattr_tuple_size(void)
 254 {
 255         static unsigned int size __read_mostly;
 256
 257         if (!size)
 258                 size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
 259
 260         return size;
 261 }
 262 #endif
 263
 264 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 265
 266 #include <linux/netfilter/nfnetlink.h>
 267 #include <linux/netfilter/nfnetlink_cttimeout.h>
 268
 269 static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
 270                                       struct net *net, void *data)
 271 {
 272         unsigned int *timeout = data;
 273         struct nf_icmp_net *in = nf_icmp_pernet(net);
 274
 275         if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
 276                 if (!timeout)
 277                         timeout = &in->timeout;
 278                 *timeout =
 279                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
 280         } else if (timeout) {
 281                 /* Set default ICMP timeout. */
 282                 *timeout = in->timeout;
 283         }
 284         return 0;
 285 }
 286
 287 static int
 288 icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 289 {
 290         const unsigned int *timeout = data;
 291
 292         if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
 293                 goto nla_put_failure;
 294         return 0;
 295
 296 nla_put_failure:
 297         return -ENOSPC;
 298 }
 299
 300 static const struct nla_policy
 301 icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
 302         [CTA_TIMEOUT_ICMP_TIMEOUT]      = { .type = NLA_U32 },
 303 };
 304 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 305
 306 #ifdef CONFIG_SYSCTL
 307 static struct ctl_table icmp_sysctl_table[] = {
 308         {
 309                 .procname       = "nf_conntrack_icmp_timeout",
 310                 .maxlen         = sizeof(unsigned int),
 311                 .mode           = 0644,
 312                 .proc_handler   = proc_dointvec_jiffies,
 313         },
 314         { }
 315 };
 316 #endif /* CONFIG_SYSCTL */
 317
 318 static int icmp_kmemdup_sysctl_table(struct nf_proto_net *pn,
 319                                      struct nf_icmp_net *in)
 320 {
 321 #ifdef CONFIG_SYSCTL
 322         pn->ctl_table = kmemdup(icmp_sysctl_table,
 323                                 sizeof(icmp_sysctl_table),
 324                                 GFP_KERNEL);
 325         if (!pn->ctl_table)
 326                 return -ENOMEM;
 327
 328         pn->ctl_table[0].data = &in->timeout;
 329 #endif
 330         return 0;
 331 }
 332
 333 static int icmp_init_net(struct net *net)
 334 {
 335         struct nf_icmp_net *in = nf_icmp_pernet(net);
 336         struct nf_proto_net *pn = &in->pn;
 337
 338         in->timeout = nf_ct_icmp_timeout;
 339
 340         return icmp_kmemdup_sysctl_table(pn, in);
 341 }
 342
 343 static struct nf_proto_net *icmp_get_net_proto(struct net *net)
 344 {
 345         return &net->ct.nf_ct_proto.icmp.pn;
 346 }
 347
 348 const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
 349 {
 350         .l4proto                = IPPROTO_ICMP,
 351         .pkt_to_tuple           = icmp_pkt_to_tuple,
 352         .invert_tuple           = icmp_invert_tuple,
 353         .packet                 = icmp_packet,
 354         .destroy                = NULL,
 355         .me                     = NULL,
 356 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 357         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 358         .nlattr_tuple_size      = icmp_nlattr_tuple_size,
 359         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 360         .nla_policy             = icmp_nla_policy,
 361 #endif
 362 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 363         .ctnl_timeout           = {
 364                 .nlattr_to_obj  = icmp_timeout_nlattr_to_obj,
 365                 .obj_to_nlattr  = icmp_timeout_obj_to_nlattr,
 366                 .nlattr_max     = CTA_TIMEOUT_ICMP_MAX,
 367                 .obj_size       = sizeof(unsigned int),
 368                 .nla_policy     = icmp_timeout_nla_policy,
 369         },
 370 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 371         .init_net               = icmp_init_net,
 372         .get_net_proto          = icmp_get_net_proto,
 373 };