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 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 107 static int
 108 icmp_error_message(struct nf_conn *tmpl, struct sk_buff *skb,
 109                    const struct nf_hook_state *state)
 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
 117         WARN_ON(skb_nfct(skb));
 118         zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
 119
 120         /* Are they talking about one of our connections? */
 121         if (!nf_ct_get_tuplepr(skb,
 122                                skb_network_offset(skb) + ip_hdrlen(skb)
 123                                                        + sizeof(struct icmphdr),
 124                                PF_INET, state->net, &origtuple)) {
 125                 pr_debug("icmp_error_message: failed to get tuple\n");
 126                 return -NF_ACCEPT;
 127         }
 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                 pr_debug("icmp_error_message: no match\n");
 133                 return -NF_ACCEPT;
 134         }
 135
 136         ctinfo = IP_CT_RELATED;
 137
 138         h = nf_conntrack_find_get(state->net, zone, &innertuple);
 139         if (!h) {
 140                 pr_debug("icmp_error_message: no match\n");
 141                 return -NF_ACCEPT;
 142         }
 143
 144         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 145                 ctinfo += IP_CT_IS_REPLY;
 146
 147         /* Update skb to refer to this connection */
 148         nf_ct_set(skb, nf_ct_tuplehash_to_ctrack(h), ctinfo);
 149         return NF_ACCEPT;
 150 }
 151
 152 static void icmp_error_log(const struct sk_buff *skb,
 153                            const struct nf_hook_state *state,
 154                            const char *msg)
 155 {
 156         nf_l4proto_log_invalid(skb, state->net, state->pf,
 157                                IPPROTO_ICMP, "%s", msg);
 158 }
 159
 160 /* Small and modified version of icmp_rcv */
 161 int nf_conntrack_icmpv4_error(struct nf_conn *tmpl,
 162                               struct sk_buff *skb, unsigned int dataoff,
 163                               const struct nf_hook_state *state)
 164 {
 165         const struct icmphdr *icmph;
 166         struct icmphdr _ih;
 167
 168         /* Not enough header? */
 169         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 170         if (icmph == NULL) {
 171                 icmp_error_log(skb, state, "short packet");
 172                 return -NF_ACCEPT;
 173         }
 174
 175         /* See ip_conntrack_proto_tcp.c */
 176         if (state->net->ct.sysctl_checksum &&
 177             state->hook == NF_INET_PRE_ROUTING &&
 178             nf_ip_checksum(skb, state->hook, dataoff, 0)) {
 179                 icmp_error_log(skb, state, "bad hw icmp checksum");
 180                 return -NF_ACCEPT;
 181         }
 182
 183         /*
 184          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 185          *
 186          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 187          *                discarded.
 188          */
 189         if (icmph->type > NR_ICMP_TYPES) {
 190                 icmp_error_log(skb, state, "invalid icmp type");
 191                 return -NF_ACCEPT;
 192         }
 193
 194         /* Need to track icmp error message? */
 195         if (icmph->type != ICMP_DEST_UNREACH &&
 196             icmph->type != ICMP_SOURCE_QUENCH &&
 197             icmph->type != ICMP_TIME_EXCEEDED &&
 198             icmph->type != ICMP_PARAMETERPROB &&
 199             icmph->type != ICMP_REDIRECT)
 200                 return NF_ACCEPT;
 201
 202         return icmp_error_message(tmpl, skb, state);
 203 }
 204
 205 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 206
 207 #include <linux/netfilter/nfnetlink.h>
 208 #include <linux/netfilter/nfnetlink_conntrack.h>
 209
 210 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 211                                 const struct nf_conntrack_tuple *t)
 212 {
 213         if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
 214             nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
 215             nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code))
 216                 goto nla_put_failure;
 217         return 0;
 218
 219 nla_put_failure:
 220         return -1;
 221 }
 222
 223 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 224         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 225         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 226         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 227 };
 228
 229 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 230                                 struct nf_conntrack_tuple *tuple)
 231 {
 232         if (!tb[CTA_PROTO_ICMP_TYPE] ||
 233             !tb[CTA_PROTO_ICMP_CODE] ||
 234             !tb[CTA_PROTO_ICMP_ID])
 235                 return -EINVAL;
 236
 237         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 238         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 239         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 240
 241         if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
 242             !invmap[tuple->dst.u.icmp.type])
 243                 return -EINVAL;
 244
 245         return 0;
 246 }
 247
 248 static unsigned int icmp_nlattr_tuple_size(void)
 249 {
 250         static unsigned int size __read_mostly;
 251
 252         if (!size)
 253                 size = nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
 254
 255         return size;
 256 }
 257 #endif
 258
 259 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 260
 261 #include <linux/netfilter/nfnetlink.h>
 262 #include <linux/netfilter/nfnetlink_cttimeout.h>
 263
 264 static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
 265                                       struct net *net, void *data)
 266 {
 267         unsigned int *timeout = data;
 268         struct nf_icmp_net *in = nf_icmp_pernet(net);
 269
 270         if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
 271                 if (!timeout)
 272                         timeout = &in->timeout;
 273                 *timeout =
 274                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
 275         } else if (timeout) {
 276                 /* Set default ICMP timeout. */
 277                 *timeout = in->timeout;
 278         }
 279         return 0;
 280 }
 281
 282 static int
 283 icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 284 {
 285         const unsigned int *timeout = data;
 286
 287         if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
 288                 goto nla_put_failure;
 289         return 0;
 290
 291 nla_put_failure:
 292         return -ENOSPC;
 293 }
 294
 295 static const struct nla_policy
 296 icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
 297         [CTA_TIMEOUT_ICMP_TIMEOUT]      = { .type = NLA_U32 },
 298 };
 299 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 300
 301 void nf_conntrack_icmp_init_net(struct net *net)
 302 {
 303         struct nf_icmp_net *in = nf_icmp_pernet(net);
 304
 305         in->timeout = nf_ct_icmp_timeout;
 306 }
 307
 308 const struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
 309 {
 310         .l4proto                = IPPROTO_ICMP,
 311 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 312         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 313         .nlattr_tuple_size      = icmp_nlattr_tuple_size,
 314         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 315         .nla_policy             = icmp_nla_policy,
 316 #endif
 317 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 318         .ctnl_timeout           = {
 319                 .nlattr_to_obj  = icmp_timeout_nlattr_to_obj,
 320                 .obj_to_nlattr  = icmp_timeout_obj_to_nlattr,
 321                 .nlattr_max     = CTA_TIMEOUT_ICMP_MAX,
 322                 .obj_size       = sizeof(unsigned int),
 323                 .nla_policy     = icmp_timeout_nla_policy,
 324         },
 325 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 326 };