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