net/ipv4/netfilter/nf_conntrack_proto_icmp.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/types.h>
  10 #include <linux/timer.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/in.h>
  13 #include <linux/icmp.h>
  14 #include <linux/seq_file.h>
  15 #include <net/ip.h>
  16 #include <net/checksum.h>
  17 #include <linux/netfilter_ipv4.h>
  18 #include <net/netfilter/nf_conntrack_tuple.h>
  19 #include <net/netfilter/nf_conntrack_l4proto.h>
  20 #include <net/netfilter/nf_conntrack_core.h>
  21 #include <net/netfilter/nf_conntrack_zones.h>
  22 #include <net/netfilter/nf_log.h>
  23
  24 static unsigned int nf_ct_icmp_timeout __read_mostly = 30*HZ;
  25
  26 static bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
  27                               struct nf_conntrack_tuple *tuple)
  28 {
  29         const struct icmphdr *hp;
  30         struct icmphdr _hdr;
  31
  32         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  33         if (hp == NULL)
  34                 return false;
  35
  36         tuple->dst.u.icmp.type = hp->type;
  37         tuple->src.u.icmp.id = hp->un.echo.id;
  38         tuple->dst.u.icmp.code = hp->code;
  39
  40         return true;
  41 }
  42
  43 /* Add 1; spaces filled with 0. */
  44 static const u_int8_t invmap[] = {
  45         [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  46         [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  47         [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  48         [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  49         [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  50         [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  51         [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  52         [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
  53 };
  54
  55 static bool icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
  56                               const struct nf_conntrack_tuple *orig)
  57 {
  58         if (orig->dst.u.icmp.type >= sizeof(invmap) ||
  59             !invmap[orig->dst.u.icmp.type])
  60                 return false;
  61
  62         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  63         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  64         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  65         return true;
  66 }
  67
  68 /* Print out the per-protocol part of the tuple. */
  69 static int icmp_print_tuple(struct seq_file *s,
  70                             const struct nf_conntrack_tuple *tuple)
  71 {
  72         return seq_printf(s, "type=%u code=%u id=%u ",
  73                           tuple->dst.u.icmp.type,
  74                           tuple->dst.u.icmp.code,
  75                           ntohs(tuple->src.u.icmp.id));
  76 }
  77
  78 static unsigned int *icmp_get_timeouts(struct net *net)
  79 {
  80         return &nf_ct_icmp_timeout;
  81 }
  82
  83 /* Returns verdict for packet, or -1 for invalid. */
  84 static int icmp_packet(struct nf_conn *ct,
  85                        const struct sk_buff *skb,
  86                        unsigned int dataoff,
  87                        enum ip_conntrack_info ctinfo,
  88                        u_int8_t pf,
  89                        unsigned int hooknum,
  90                        unsigned int *timeout)
  91 {
  92         /* Do not immediately delete the connection after the first
  93            successful reply to avoid excessive conntrackd traffic
  94            and also to handle correctly ICMP echo reply duplicates. */
  95         nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
  96
  97         return NF_ACCEPT;
  98 }
  99
 100 /* Called when a new connection for this protocol found. */
 101 static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
 102                      unsigned int dataoff, unsigned int *timeouts)
 103 {
 104         static const u_int8_t valid_new[] = {
 105                 [ICMP_ECHO] = 1,
 106                 [ICMP_TIMESTAMP] = 1,
 107                 [ICMP_INFO_REQUEST] = 1,
 108                 [ICMP_ADDRESS] = 1
 109         };
 110
 111         if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
 112             !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
 113                 /* Can't create a new ICMP `conn' with this. */
 114                 pr_debug("icmp: can't create new conn with type %u\n",
 115                          ct->tuplehash[0].tuple.dst.u.icmp.type);
 116                 nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
 117                 return false;
 118         }
 119         return true;
 120 }
 121
 122 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 123 static int
 124 icmp_error_message(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
 125                  enum ip_conntrack_info *ctinfo,
 126                  unsigned int hooknum)
 127 {
 128         struct nf_conntrack_tuple innertuple, origtuple;
 129         const struct nf_conntrack_l4proto *innerproto;
 130         const struct nf_conntrack_tuple_hash *h;
 131         u16 zone = tmpl ? nf_ct_zone(tmpl) : NF_CT_DEFAULT_ZONE;
 132
 133         NF_CT_ASSERT(skb->nfct == NULL);
 134
 135         /* Are they talking about one of our connections? */
 136         if (!nf_ct_get_tuplepr(skb,
 137                                skb_network_offset(skb) + ip_hdrlen(skb)
 138                                                        + sizeof(struct icmphdr),
 139                                PF_INET, &origtuple)) {
 140                 pr_debug("icmp_error_message: failed to get tuple\n");
 141                 return -NF_ACCEPT;
 142         }
 143
 144         /* rcu_read_lock()ed by nf_hook_slow */
 145         innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
 146
 147         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 148            been preserved inside the ICMP. */
 149         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 150                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 151                 pr_debug("icmp_error_message: no match\n");
 152                 return -NF_ACCEPT;
 153         }
 154
 155         *ctinfo = IP_CT_RELATED;
 156
 157         h = nf_conntrack_find_get(net, zone, &innertuple);
 158         if (!h) {
 159                 pr_debug("icmp_error_message: no match\n");
 160                 return -NF_ACCEPT;
 161         }
 162
 163         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 164                 *ctinfo += IP_CT_IS_REPLY;
 165
 166         /* Update skb to refer to this connection */
 167         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 168         skb->nfctinfo = *ctinfo;
 169         return NF_ACCEPT;
 170 }
 171
 172 /* Small and modified version of icmp_rcv */
 173 static int
 174 icmp_error(struct net *net, struct nf_conn *tmpl,
 175            struct sk_buff *skb, unsigned int dataoff,
 176            enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
 177 {
 178         const struct icmphdr *icmph;
 179         struct icmphdr _ih;
 180
 181         /* Not enough header? */
 182         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 183         if (icmph == NULL) {
 184                 if (LOG_INVALID(net, IPPROTO_ICMP))
 185                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 186                                       "nf_ct_icmp: short packet ");
 187                 return -NF_ACCEPT;
 188         }
 189
 190         /* See ip_conntrack_proto_tcp.c */
 191         if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
 192             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
 193                 if (LOG_INVALID(net, IPPROTO_ICMP))
 194                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 195                                       "nf_ct_icmp: bad HW ICMP checksum ");
 196                 return -NF_ACCEPT;
 197         }
 198
 199         /*
 200          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 201          *
 202          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 203          *                discarded.
 204          */
 205         if (icmph->type > NR_ICMP_TYPES) {
 206                 if (LOG_INVALID(net, IPPROTO_ICMP))
 207                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 208                                       "nf_ct_icmp: invalid ICMP type ");
 209                 return -NF_ACCEPT;
 210         }
 211
 212         /* Need to track icmp error message? */
 213         if (icmph->type != ICMP_DEST_UNREACH &&
 214             icmph->type != ICMP_SOURCE_QUENCH &&
 215             icmph->type != ICMP_TIME_EXCEEDED &&
 216             icmph->type != ICMP_PARAMETERPROB &&
 217             icmph->type != ICMP_REDIRECT)
 218                 return NF_ACCEPT;
 219
 220         return icmp_error_message(net, tmpl, skb, ctinfo, hooknum);
 221 }
 222
 223 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 224
 225 #include <linux/netfilter/nfnetlink.h>
 226 #include <linux/netfilter/nfnetlink_conntrack.h>
 227
 228 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 229                                 const struct nf_conntrack_tuple *t)
 230 {
 231         NLA_PUT_BE16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id);
 232         NLA_PUT_U8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type);
 233         NLA_PUT_U8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code);
 234
 235         return 0;
 236
 237 nla_put_failure:
 238         return -1;
 239 }
 240
 241 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 242         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 243         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 244         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 245 };
 246
 247 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 248                                 struct nf_conntrack_tuple *tuple)
 249 {
 250         if (!tb[CTA_PROTO_ICMP_TYPE] ||
 251             !tb[CTA_PROTO_ICMP_CODE] ||
 252             !tb[CTA_PROTO_ICMP_ID])
 253                 return -EINVAL;
 254
 255         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 256         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 257         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 258
 259         if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
 260             !invmap[tuple->dst.u.icmp.type])
 261                 return -EINVAL;
 262
 263         return 0;
 264 }
 265
 266 static int icmp_nlattr_tuple_size(void)
 267 {
 268         return nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
 269 }
 270 #endif
 271
 272 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 273
 274 #include <linux/netfilter/nfnetlink.h>
 275 #include <linux/netfilter/nfnetlink_cttimeout.h>
 276
 277 static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[], void *data)
 278 {
 279         unsigned int *timeout = data;
 280
 281         if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
 282                 *timeout =
 283                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
 284         } else {
 285                 /* Set default ICMP timeout. */
 286                 *timeout = nf_ct_icmp_timeout;
 287         }
 288         return 0;
 289 }
 290
 291 static int
 292 icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 293 {
 294         const unsigned int *timeout = data;
 295
 296         NLA_PUT_BE32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ));
 297
 298         return 0;
 299
 300 nla_put_failure:
 301         return -ENOSPC;
 302 }
 303
 304 static const struct nla_policy
 305 icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
 306         [CTA_TIMEOUT_ICMP_TIMEOUT]      = { .type = NLA_U32 },
 307 };
 308 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 309
 310 #ifdef CONFIG_SYSCTL
 311 static struct ctl_table_header *icmp_sysctl_header;
 312 static struct ctl_table icmp_sysctl_table[] = {
 313         {
 314                 .procname       = "nf_conntrack_icmp_timeout",
 315                 .data           = &nf_ct_icmp_timeout,
 316                 .maxlen         = sizeof(unsigned int),
 317                 .mode           = 0644,
 318                 .proc_handler   = proc_dointvec_jiffies,
 319         },
 320         { }
 321 };
 322 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 323 static struct ctl_table icmp_compat_sysctl_table[] = {
 324         {
 325                 .procname       = "ip_conntrack_icmp_timeout",
 326                 .data           = &nf_ct_icmp_timeout,
 327                 .maxlen         = sizeof(unsigned int),
 328                 .mode           = 0644,
 329                 .proc_handler   = proc_dointvec_jiffies,
 330         },
 331         { }
 332 };
 333 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 334 #endif /* CONFIG_SYSCTL */
 335
 336 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
 337 {
 338         .l3proto                = PF_INET,
 339         .l4proto                = IPPROTO_ICMP,
 340         .name                   = "icmp",
 341         .pkt_to_tuple           = icmp_pkt_to_tuple,
 342         .invert_tuple           = icmp_invert_tuple,
 343         .print_tuple            = icmp_print_tuple,
 344         .packet                 = icmp_packet,
 345         .get_timeouts           = icmp_get_timeouts,
 346         .new                    = icmp_new,
 347         .error                  = icmp_error,
 348         .destroy                = NULL,
 349         .me                     = NULL,
 350 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 351         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 352         .nlattr_tuple_size      = icmp_nlattr_tuple_size,
 353         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 354         .nla_policy             = icmp_nla_policy,
 355 #endif
 356 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 357         .ctnl_timeout           = {
 358                 .nlattr_to_obj  = icmp_timeout_nlattr_to_obj,
 359                 .obj_to_nlattr  = icmp_timeout_obj_to_nlattr,
 360                 .nlattr_max     = CTA_TIMEOUT_ICMP_MAX,
 361                 .obj_size       = sizeof(unsigned int),
 362                 .nla_policy     = icmp_timeout_nla_policy,
 363         },
 364 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 365 #ifdef CONFIG_SYSCTL
 366         .ctl_table_header       = &icmp_sysctl_header,
 367         .ctl_table              = icmp_sysctl_table,
 368 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 369         .ctl_compat_table       = icmp_compat_sysctl_table,
 370 #endif
 371 #endif
 372 };