1 /* 2 * firewall3 - 3rd OpenWrt UCI firewall implementation 3 * 4 * Copyright (C) 2013 Jo-Philipp Wich <jo@mein.io> 5 * 6 * Permission to use, copy, modify, and/or distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 #include "defaults.h" 20 21 22 #define C(f, tbl, def, fmt) \ 23 { FW3_FAMILY_##f, FW3_TABLE_##tbl, FW3_FLAG_##def, fmt } 24 25 static const struct fw3_chain_spec default_chains[] = { 26 C(ANY, FILTER, UNSPEC, "reject"), 27 C(ANY, FILTER, CUSTOM_CHAINS, "input_rule"), 28 C(ANY, FILTER, CUSTOM_CHAINS, "output_rule"), 29 C(ANY, FILTER, CUSTOM_CHAINS, "forwarding_rule"), 30 C(ANY, FILTER, SYN_FLOOD, "syn_flood"), 31 32 C(V4, NAT, CUSTOM_CHAINS, "prerouting_rule"), 33 C(V4, NAT, CUSTOM_CHAINS, "postrouting_rule"), 34 35 { } 36 }; 37 38 const struct fw3_option fw3_flag_opts[] = { 39 FW3_OPT("input", target, defaults, policy_input), 40 FW3_OPT("forward", target, defaults, policy_forward), 41 FW3_OPT("output", target, defaults, policy_output), 42 43 FW3_OPT("drop_invalid", bool, defaults, drop_invalid), 44 FW3_OPT("tcp_reject_code", reject_code, defaults, tcp_reject_code), 45 FW3_OPT("any_reject_code", reject_code, defaults, any_reject_code), 46 47 FW3_OPT("syn_flood", bool, defaults, syn_flood), 48 FW3_OPT("synflood_protect", bool, defaults, syn_flood), 49 FW3_OPT("synflood_rate", limit, defaults, syn_flood_rate), 50 FW3_OPT("synflood_burst", int, defaults, syn_flood_rate.burst), 51 52 FW3_OPT("tcp_syncookies", bool, defaults, tcp_syncookies), 53 FW3_OPT("tcp_ecn", int, defaults, tcp_ecn), 54 FW3_OPT("tcp_window_scaling", bool, defaults, tcp_window_scaling), 55 56 FW3_OPT("accept_redirects", bool, defaults, accept_redirects), 57 FW3_OPT("accept_source_route", bool, defaults, accept_source_route), 58 59 FW3_OPT("auto_helper", bool, defaults, auto_helper), 60 FW3_OPT("custom_chains", bool, defaults, custom_chains), 61 FW3_OPT("disable_ipv6", bool, defaults, disable_ipv6), 62 FW3_OPT("flow_offloading", bool, defaults, flow_offloading), 63 FW3_OPT("flow_offloading_hw", bool, defaults, flow_offloading_hw), 64 65 FW3_OPT("__flags_v4", int, defaults, flags[0]), 66 FW3_OPT("__flags_v6", int, defaults, flags[1]), 67 68 { } 69 }; 70 71 72 static void 73 check_policy(struct uci_element *e, enum fw3_flag *pol, const char *name) 74 { 75 if (*pol == FW3_FLAG_UNSPEC) 76 { 77 warn_elem(e, "has no %s policy specified, defaulting to DROP", name); 78 *pol = FW3_FLAG_DROP; 79 } 80 else if (*pol > FW3_FLAG_DROP) 81 { 82 warn_elem(e, "has invalid %s policy, defaulting to DROP", name); 83 *pol = FW3_FLAG_DROP; 84 } 85 } 86 87 static void 88 check_target(struct uci_element *e, bool *available, const char *target, const bool ipv6) 89 { 90 const bool b = fw3_has_target(ipv6, target); 91 if (!b) 92 { 93 warn_elem(e, "requires unavailable target extension %s, disabling", target); 94 } 95 *available = b; 96 } 97 98 static void 99 check_any_reject_code(struct uci_element *e, enum fw3_reject_code *any_reject_code) 100 { 101 if (*any_reject_code == FW3_REJECT_CODE_TCP_RESET) { 102 warn_elem(e, "tcp-reset not valid for any_reject_code, defaulting to port-unreach"); 103 *any_reject_code = FW3_REJECT_CODE_PORT_UNREACH; 104 } 105 } 106 107 static const char* 108 get_reject_code(enum fw3_family family, enum fw3_reject_code reject_code) 109 { 110 switch (reject_code) { 111 case FW3_REJECT_CODE_TCP_RESET: 112 return "tcp-reset"; 113 case FW3_REJECT_CODE_PORT_UNREACH: 114 return "port-unreach"; 115 case FW3_REJECT_CODE_ADM_PROHIBITED: 116 return family == FW3_FAMILY_V6 ? "adm-prohibited": "admin-prohib"; 117 default: 118 return "unknown"; 119 } 120 } 121 122 void 123 fw3_load_defaults(struct fw3_state *state, struct uci_package *p) 124 { 125 struct uci_section *s; 126 struct uci_element *e; 127 struct fw3_defaults *defs = &state->defaults; 128 129 bool seen = false; 130 131 defs->tcp_reject_code = FW3_REJECT_CODE_TCP_RESET; 132 defs->any_reject_code = FW3_REJECT_CODE_PORT_UNREACH; 133 defs->syn_flood_rate.rate = 25; 134 defs->syn_flood_rate.burst = 50; 135 defs->tcp_syncookies = true; 136 defs->tcp_window_scaling = true; 137 defs->custom_chains = true; 138 defs->auto_helper = true; 139 140 uci_foreach_element(&p->sections, e) 141 { 142 s = uci_to_section(e); 143 144 if (strcmp(s->type, "defaults")) 145 continue; 146 147 if (seen) 148 { 149 warn_elem(e, "ignoring duplicate section"); 150 continue; 151 } 152 153 if(!fw3_parse_options(&state->defaults, fw3_flag_opts, s)) 154 warn_elem(e, "has invalid options"); 155 156 check_policy(e, &defs->policy_input, "input"); 157 check_policy(e, &defs->policy_output, "output"); 158 check_policy(e, &defs->policy_forward, "forward"); 159 160 check_any_reject_code(e, &defs->any_reject_code); 161 162 /* exists in both ipv4 and ipv6, if at all, so only check ipv4 */ 163 check_target(e, &defs->flow_offloading, "FLOWOFFLOAD", false); 164 } 165 } 166 167 void 168 fw3_print_default_chains(struct fw3_ipt_handle *handle, struct fw3_state *state, 169 bool reload) 170 { 171 struct fw3_defaults *defs = &state->defaults; 172 const struct fw3_chain_spec *c; 173 174 #define policy(t) \ 175 ((t == FW3_FLAG_REJECT) ? FW3_FLAG_DROP : t) 176 177 if (handle->family == FW3_FAMILY_V6 && defs->disable_ipv6) 178 return; 179 180 if (handle->table == FW3_TABLE_FILTER) 181 { 182 fw3_ipt_set_policy(handle, "INPUT", policy(defs->policy_input)); 183 fw3_ipt_set_policy(handle, "OUTPUT", policy(defs->policy_output)); 184 fw3_ipt_set_policy(handle, "FORWARD", policy(defs->policy_forward)); 185 } 186 187 if (defs->custom_chains) 188 set(defs->flags, handle->family, FW3_FLAG_CUSTOM_CHAINS); 189 190 if (defs->syn_flood) 191 set(defs->flags, handle->family, FW3_FLAG_SYN_FLOOD); 192 193 for (c = default_chains; c->format; c++) 194 { 195 /* don't touch user chains on selective stop */ 196 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS) 197 continue; 198 199 if (!fw3_is_family(c, handle->family)) 200 continue; 201 202 if (c->table != handle->table) 203 continue; 204 205 if (c->flag && 206 !fw3_hasbit(defs->flags[handle->family == FW3_FAMILY_V6], c->flag)) 207 continue; 208 209 fw3_ipt_create_chain(handle, c->format); 210 } 211 212 set(defs->flags, handle->family, handle->table); 213 } 214 215 void 216 fw3_print_default_head_rules(struct fw3_ipt_handle *handle, 217 struct fw3_state *state, bool reload) 218 { 219 int i; 220 struct fw3_defaults *defs = &state->defaults; 221 struct fw3_device lodev = { .set = true }; 222 struct fw3_protocol tcp = { .protocol = 6 }; 223 struct fw3_ipt_rule *r; 224 225 const char *chains[] = { 226 "INPUT", "input", 227 "OUTPUT", "output", 228 "FORWARD", "forwarding", 229 }; 230 231 switch (handle->table) 232 { 233 case FW3_TABLE_FILTER: 234 235 sprintf(lodev.name, "lo"); 236 237 r = fw3_ipt_rule_create(handle, NULL, &lodev, NULL, NULL, NULL); 238 fw3_ipt_rule_target(r, "ACCEPT"); 239 fw3_ipt_rule_append(r, "INPUT"); 240 241 r = fw3_ipt_rule_create(handle, NULL, NULL, &lodev, NULL, NULL); 242 fw3_ipt_rule_target(r, "ACCEPT"); 243 fw3_ipt_rule_append(r, "OUTPUT"); 244 245 if (defs->custom_chains) 246 { 247 for (i = 0; i < ARRAY_SIZE(chains); i += 2) 248 { 249 r = fw3_ipt_rule_new(handle); 250 fw3_ipt_rule_comment(r, "Custom %s rule chain", chains[i+1]); 251 fw3_ipt_rule_target(r, "%s_rule", chains[i+1]); 252 fw3_ipt_rule_append(r, chains[i]); 253 } 254 } 255 256 if (defs->flow_offloading) 257 { 258 r = fw3_ipt_rule_new(handle); 259 fw3_ipt_rule_comment(r, "Traffic offloading"); 260 fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED"); 261 fw3_ipt_rule_target(r, "FLOWOFFLOAD"); 262 if (defs->flow_offloading_hw) 263 fw3_ipt_rule_addarg(r, false, "--hw", NULL); 264 fw3_ipt_rule_append(r, "FORWARD"); 265 } 266 267 for (i = 0; i < ARRAY_SIZE(chains); i += 2) 268 { 269 r = fw3_ipt_rule_new(handle); 270 fw3_ipt_rule_extra(r, "-m conntrack --ctstate RELATED,ESTABLISHED"); 271 fw3_ipt_rule_target(r, "ACCEPT"); 272 fw3_ipt_rule_append(r, chains[i]); 273 274 if (defs->drop_invalid) 275 { 276 r = fw3_ipt_rule_new(handle); 277 fw3_ipt_rule_extra(r, "-m conntrack --ctstate INVALID"); 278 fw3_ipt_rule_target(r, "DROP"); 279 fw3_ipt_rule_append(r, chains[i]); 280 } 281 } 282 283 if (defs->syn_flood) 284 { 285 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL); 286 fw3_ipt_rule_extra(r, "--syn"); 287 fw3_ipt_rule_limit(r, &defs->syn_flood_rate); 288 fw3_ipt_rule_target(r, "RETURN"); 289 fw3_ipt_rule_append(r, "syn_flood"); 290 291 r = fw3_ipt_rule_new(handle); 292 fw3_ipt_rule_target(r, "DROP"); 293 fw3_ipt_rule_append(r, "syn_flood"); 294 295 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL); 296 fw3_ipt_rule_extra(r, "--syn"); 297 fw3_ipt_rule_target(r, "syn_flood"); 298 fw3_ipt_rule_append(r, "INPUT"); 299 } 300 301 r = fw3_ipt_rule_create(handle, &tcp, NULL, NULL, NULL, NULL); 302 fw3_ipt_rule_target(r, "REJECT"); 303 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->tcp_reject_code)); 304 fw3_ipt_rule_append(r, "reject"); 305 306 r = fw3_ipt_rule_new(handle); 307 fw3_ipt_rule_target(r, "REJECT"); 308 fw3_ipt_rule_addarg(r, false, "--reject-with", get_reject_code(handle->family, defs->any_reject_code)); 309 fw3_ipt_rule_append(r, "reject"); 310 311 break; 312 313 case FW3_TABLE_NAT: 314 if (defs->custom_chains) 315 { 316 r = fw3_ipt_rule_new(handle); 317 fw3_ipt_rule_comment(r, "Custom prerouting rule chain"); 318 fw3_ipt_rule_target(r, "prerouting_rule"); 319 fw3_ipt_rule_append(r, "PREROUTING"); 320 321 r = fw3_ipt_rule_new(handle); 322 fw3_ipt_rule_comment(r, "Custom postrouting rule chain"); 323 fw3_ipt_rule_target(r, "postrouting_rule"); 324 fw3_ipt_rule_append(r, "POSTROUTING"); 325 } 326 break; 327 328 default: 329 break; 330 } 331 } 332 333 void 334 fw3_print_default_tail_rules(struct fw3_ipt_handle *handle, 335 struct fw3_state *state, bool reload) 336 { 337 struct fw3_defaults *defs = &state->defaults; 338 struct fw3_ipt_rule *r; 339 340 if (handle->table != FW3_TABLE_FILTER) 341 return; 342 343 if (defs->policy_input == FW3_FLAG_REJECT) 344 { 345 r = fw3_ipt_rule_new(handle); 346 347 if (!r) 348 return; 349 350 fw3_ipt_rule_target(r, "reject"); 351 fw3_ipt_rule_append(r, "INPUT"); 352 } 353 354 if (defs->policy_output == FW3_FLAG_REJECT) 355 { 356 r = fw3_ipt_rule_new(handle); 357 358 if (!r) 359 return; 360 361 fw3_ipt_rule_target(r, "reject"); 362 fw3_ipt_rule_append(r, "OUTPUT"); 363 } 364 365 if (defs->policy_forward == FW3_FLAG_REJECT) 366 { 367 r = fw3_ipt_rule_new(handle); 368 369 if (!r) 370 return; 371 372 fw3_ipt_rule_target(r, "reject"); 373 fw3_ipt_rule_append(r, "FORWARD"); 374 } 375 } 376 377 static void 378 set_default(const char *name, int set) 379 { 380 FILE *f; 381 char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")]; 382 383 snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name); 384 385 info(" * Set tcp_%s to %s", name, set ? "on" : "off"); 386 387 if (!(f = fopen(path, "w"))) 388 { 389 info(" ! Unable to write value: %s", strerror(errno)); 390 return; 391 } 392 393 fprintf(f, "%u\n", set); 394 fclose(f); 395 } 396 397 void 398 fw3_set_defaults(struct fw3_state *state) 399 { 400 set_default("ecn", state->defaults.tcp_ecn); 401 set_default("syncookies", state->defaults.tcp_syncookies); 402 set_default("window_scaling", state->defaults.tcp_window_scaling); 403 } 404 405 void 406 fw3_flush_rules(struct fw3_ipt_handle *handle, struct fw3_state *state, 407 bool reload) 408 { 409 enum fw3_flag policy = reload ? FW3_FLAG_DROP : FW3_FLAG_ACCEPT; 410 struct fw3_defaults *defs = &state->defaults; 411 const struct fw3_chain_spec *c; 412 413 if (!has(defs->flags, handle->family, handle->table)) 414 return; 415 416 if (handle->table == FW3_TABLE_FILTER) 417 { 418 fw3_ipt_set_policy(handle, "INPUT", policy); 419 fw3_ipt_set_policy(handle, "OUTPUT", policy); 420 fw3_ipt_set_policy(handle, "FORWARD", policy); 421 } 422 423 fw3_ipt_delete_id_rules(handle, "INPUT"); 424 fw3_ipt_delete_id_rules(handle, "OUTPUT"); 425 fw3_ipt_delete_id_rules(handle, "FORWARD"); 426 fw3_ipt_delete_id_rules(handle, "PREROUTING"); 427 fw3_ipt_delete_id_rules(handle, "POSTROUTING"); 428 429 for (c = default_chains; c->format; c++) 430 { 431 /* don't touch user chains on selective stop */ 432 if (reload && c->flag == FW3_FLAG_CUSTOM_CHAINS) 433 continue; 434 435 if (!fw3_is_family(c, handle->family)) 436 continue; 437 438 if (c->table != handle->table) 439 continue; 440 441 if (c->flag && !has(defs->flags, handle->family, c->flag)) 442 continue; 443 444 fw3_ipt_flush_chain(handle, c->format); 445 446 /* keep certain basic chains that do not depend on any settings to 447 avoid purging unrelated user rules pointing to them */ 448 if (reload && !c->flag) 449 continue; 450 451 fw3_ipt_delete_chain(handle, c->format); 452 } 453 454 del(defs->flags, handle->family, handle->table); 455 } 456 457 void 458 fw3_flush_all(struct fw3_ipt_handle *handle) 459 { 460 if (handle->table == FW3_TABLE_FILTER) 461 { 462 fw3_ipt_set_policy(handle, "INPUT", FW3_FLAG_ACCEPT); 463 fw3_ipt_set_policy(handle, "OUTPUT", FW3_FLAG_ACCEPT); 464 fw3_ipt_set_policy(handle, "FORWARD", FW3_FLAG_ACCEPT); 465 } 466 467 fw3_ipt_flush(handle); 468 } 469
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