defaults.c

   1 /*
   2  * firewall3 - 3rd OpenWrt UCI firewall implementation
   3  *
   4  *   Copyright (C) 2013 Jo-Philipp Wich <jow@openwrt.org>
   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_DEFAULT_##def, fmt }
  24
  25 static const struct fw3_rule_spec default_chains[] = {
  26         C(ANY, FILTER, UNSPEC,        "delegate_input"),
  27         C(ANY, FILTER, UNSPEC,        "delegate_output"),
  28         C(ANY, FILTER, UNSPEC,        "delegate_forward"),
  29         C(ANY, FILTER, UNSPEC,        "reject"),
  30         C(ANY, FILTER, CUSTOM_CHAINS, "input_rule"),
  31         C(ANY, FILTER, CUSTOM_CHAINS, "output_rule"),
  32         C(ANY, FILTER, CUSTOM_CHAINS, "forwarding_rule"),
  33         C(ANY, FILTER, SYN_FLOOD,     "syn_flood"),
  34
  35         C(V4,  NAT,    UNSPEC,        "delegate_prerouting"),
  36         C(V4,  NAT,    UNSPEC,        "delegate_postrouting"),
  37         C(V4,  NAT,    CUSTOM_CHAINS, "prerouting_rule"),
  38         C(V4,  NAT,    CUSTOM_CHAINS, "postrouting_rule"),
  39
  40         C(ANY, MANGLE, UNSPEC,        "mssfix"),
  41         C(ANY, RAW,    UNSPEC,        "notrack"),
  42
  43         { }
  44 };
  45
  46 static const struct fw3_rule_spec toplevel_rules[] = {
  47         C(ANY, FILTER, UNSPEC,        "INPUT -j delegate_input"),
  48         C(ANY, FILTER, UNSPEC,        "OUTPUT -j delegate_output"),
  49         C(ANY, FILTER, UNSPEC,        "FORWARD -j delegate_forward"),
  50
  51         C(V4,  NAT,    UNSPEC,        "PREROUTING -j delegate_prerouting"),
  52         C(V4,  NAT,    UNSPEC,        "POSTROUTING -j delegate_postrouting"),
  53
  54         C(ANY, MANGLE, UNSPEC,        "FORWARD -j mssfix"),
  55         C(ANY, RAW,    UNSPEC,        "PREROUTING -j notrack"),
  56
  57         { }
  58 };
  59
  60 const struct fw3_option fw3_default_opts[] = {
  61         FW3_OPT("input",               target,   defaults, policy_input),
  62         FW3_OPT("forward",             target,   defaults, policy_forward),
  63         FW3_OPT("output",              target,   defaults, policy_output),
  64
  65         FW3_OPT("drop_invalid",        bool,     defaults, drop_invalid),
  66
  67         FW3_OPT("syn_flood",           bool,     defaults, syn_flood),
  68         FW3_OPT("synflood_protect",    bool,     defaults, syn_flood),
  69         FW3_OPT("synflood_rate",       limit,    defaults, syn_flood_rate),
  70         FW3_OPT("synflood_burst",      int,      defaults, syn_flood_rate.burst),
  71
  72         FW3_OPT("tcp_syncookies",      bool,     defaults, tcp_syncookies),
  73         FW3_OPT("tcp_ecn",             bool,     defaults, tcp_ecn),
  74         FW3_OPT("tcp_window_scaling",  bool,     defaults, tcp_window_scaling),
  75
  76         FW3_OPT("accept_redirects",    bool,     defaults, accept_redirects),
  77         FW3_OPT("accept_source_route", bool,     defaults, accept_source_route),
  78
  79         FW3_OPT("custom_chains",       bool,     defaults, custom_chains),
  80         FW3_OPT("disable_ipv6",        bool,     defaults, disable_ipv6),
  81
  82         { }
  83 };
  84
  85
  86 static void
  87 check_policy(struct uci_element *e, enum fw3_target *pol, const char *name)
  88 {
  89         if (*pol == FW3_TARGET_UNSPEC)
  90         {
  91                 warn_elem(e, "has no %s policy specified, defaulting to DROP", name);
  92                 *pol = FW3_TARGET_DROP;
  93         }
  94         else if (*pol > FW3_TARGET_DROP)
  95         {
  96                 warn_elem(e, "has invalid %s policy, defaulting to DROP", name);
  97                 *pol = FW3_TARGET_DROP;
  98         }
  99 }
 100
 101 void
 102 fw3_load_defaults(struct fw3_state *state, struct uci_package *p)
 103 {
 104         struct uci_section *s;
 105         struct uci_element *e;
 106         struct fw3_defaults *defs = &state->defaults;
 107
 108         bool seen = false;
 109
 110         defs->syn_flood_rate.rate  = 25;
 111         defs->syn_flood_rate.burst = 50;
 112         defs->tcp_syncookies       = true;
 113         defs->tcp_window_scaling   = true;
 114         defs->custom_chains        = true;
 115
 116         uci_foreach_element(&p->sections, e)
 117         {
 118                 s = uci_to_section(e);
 119
 120                 if (strcmp(s->type, "defaults"))
 121                         continue;
 122
 123                 if (seen)
 124                 {
 125                         warn_elem(e, "ignoring duplicate section");
 126                         continue;
 127                 }
 128
 129                 fw3_parse_options(&state->defaults, fw3_default_opts, s);
 130
 131                 check_policy(e, &defs->policy_input, "input");
 132                 check_policy(e, &defs->policy_output, "output");
 133                 check_policy(e, &defs->policy_forward, "forward");
 134         }
 135 }
 136
 137 void
 138 fw3_print_default_chains(enum fw3_table table, enum fw3_family family,
 139                          bool reload, struct fw3_state *state)
 140 {
 141         bool rv;
 142         struct fw3_defaults *defs = &state->defaults;
 143         uint32_t custom_mask = ~0;
 144
 145 #define policy(t) \
 146         ((t == FW3_TARGET_REJECT) ? "DROP" : fw3_flag_names[t])
 147
 148         if (family == FW3_FAMILY_V6 && defs->disable_ipv6)
 149                 return;
 150
 151         if (table == FW3_TABLE_FILTER)
 152         {
 153                 fw3_pr(":INPUT %s [0:0]\n", policy(defs->policy_input));
 154                 fw3_pr(":FORWARD %s [0:0]\n", policy(defs->policy_forward));
 155                 fw3_pr(":OUTPUT %s [0:0]\n", policy(defs->policy_output));
 156         }
 157
 158         /* Don't touch user chains on reload */
 159         if (reload)
 160                 delbit(custom_mask, FW3_DEFAULT_CUSTOM_CHAINS);
 161
 162         if (defs->custom_chains)
 163                 set(defs->flags, family, FW3_DEFAULT_CUSTOM_CHAINS);
 164
 165         if (defs->syn_flood)
 166                 set(defs->flags, family, FW3_DEFAULT_SYN_FLOOD);
 167
 168         rv = fw3_pr_rulespec(table, family, defs->flags, custom_mask,
 169                              default_chains, ":%s - [0:0]\n");
 170
 171         if (rv)
 172                 set(defs->flags, family, table);
 173 }
 174
 175 void
 176 fw3_print_default_head_rules(enum fw3_table table, enum fw3_family family,
 177                              bool reload, struct fw3_state *state)
 178 {
 179         int i;
 180         struct fw3_defaults *defs = &state->defaults;
 181         const char *chains[] = {
 182                 "input", "input",
 183                 "output", "output",
 184                 "forward", "forwarding",
 185         };
 186
 187         fw3_pr_rulespec(table, family, NULL, 0, toplevel_rules, "-A %s\n");
 188
 189         switch (table)
 190         {
 191         case FW3_TABLE_FILTER:
 192                 fw3_pr("-A delegate_input -i lo -j ACCEPT\n");
 193                 fw3_pr("-A delegate_output -o lo -j ACCEPT\n");
 194
 195                 if (defs->custom_chains)
 196                 {
 197                         for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 198                         {
 199                                 fw3_pr("-A delegate_%s -m comment "
 200                                        "--comment \"user chain for %s\" -j %s_rule\n",
 201                                            chains[i], chains[i+1], chains[i+1]);
 202                         }
 203                 }
 204
 205                 for (i = 0; i < ARRAY_SIZE(chains); i += 2)
 206                 {
 207                         fw3_pr("-A delegate_%s -m conntrack --ctstate RELATED,ESTABLISHED "
 208                                "-j ACCEPT\n", chains[i]);
 209
 210                         if (defs->drop_invalid)
 211                         {
 212                                 fw3_pr("-A delegate_%s -m conntrack --ctstate INVALID -j DROP\n",
 213                                        chains[i]);
 214                         }
 215                 }
 216
 217                 if (defs->syn_flood)
 218                 {
 219                         fw3_pr("-A syn_flood -p tcp --syn");
 220                         fw3_format_limit(&defs->syn_flood_rate);
 221                         fw3_pr(" -j RETURN\n");
 222
 223                         fw3_pr("-A syn_flood -j DROP\n");
 224                         fw3_pr("-A delegate_input -p tcp --syn -j syn_flood\n");
 225                 }
 226
 227                 fw3_pr("-A reject -p tcp -j REJECT --reject-with tcp-reset\n");
 228                 fw3_pr("-A reject -j REJECT --reject-with port-unreach\n");
 229
 230                 break;
 231
 232         case FW3_TABLE_NAT:
 233                 if (defs->custom_chains)
 234                 {
 235                         fw3_pr("-A delegate_prerouting "
 236                                "-m comment --comment \"user chain for prerouting\" "
 237                                "-j prerouting_rule\n");
 238
 239                         fw3_pr("-A delegate_postrouting "
 240                                "-m comment --comment \"user chain for postrouting\" "
 241                                "-j postrouting_rule\n");
 242                 }
 243                 break;
 244
 245         default:
 246                 break;
 247         }
 248 }
 249
 250 void
 251 fw3_print_default_tail_rules(enum fw3_table table, enum fw3_family family,
 252                              bool reload, struct fw3_state *state)
 253 {
 254         struct fw3_defaults *defs = &state->defaults;
 255
 256         if (table != FW3_TABLE_FILTER)
 257                 return;
 258
 259         if (defs->policy_input == FW3_TARGET_REJECT)
 260                 fw3_pr("-A delegate_input -j reject\n");
 261
 262         if (defs->policy_output == FW3_TARGET_REJECT)
 263                 fw3_pr("-A delegate_output -j reject\n");
 264
 265         if (defs->policy_forward == FW3_TARGET_REJECT)
 266                 fw3_pr("-A delegate_forward -j reject\n");
 267 }
 268
 269 static void
 270 set_default(const char *name, bool set)
 271 {
 272         FILE *f;
 273         char path[sizeof("/proc/sys/net/ipv4/tcp_window_scaling\0")];
 274
 275         snprintf(path, sizeof(path), "/proc/sys/net/ipv4/tcp_%s", name);
 276
 277         info(" * Set tcp_%s to %s", name, set ? "on" : "off", name);
 278
 279         if (!(f = fopen(path, "w")))
 280         {
 281                 info("   ! Unable to write value: %s", strerror(errno));
 282                 return;
 283         }
 284
 285         fprintf(f, "%u\n", set);
 286         fclose(f);
 287 }
 288
 289 void
 290 fw3_set_defaults(struct fw3_state *state)
 291 {
 292         set_default("ecn",            state->defaults.tcp_ecn);
 293         set_default("syncookies",     state->defaults.tcp_syncookies);
 294         set_default("window_scaling", state->defaults.tcp_window_scaling);
 295 }
 296
 297 static void
 298 reset_policy(enum fw3_table table, enum fw3_target policy)
 299 {
 300         if (table != FW3_TABLE_FILTER)
 301                 return;
 302
 303         fw3_pr(":INPUT %s [0:0]\n", fw3_flag_names[policy]);
 304         fw3_pr(":OUTPUT %s [0:0]\n", fw3_flag_names[policy]);
 305         fw3_pr(":FORWARD %s [0:0]\n", fw3_flag_names[policy]);
 306 }
 307
 308 void
 309 fw3_flush_rules(enum fw3_table table, enum fw3_family family,
 310                 bool pass2, bool reload, struct fw3_state *state)
 311 {
 312         struct fw3_defaults *defs = &state->defaults;
 313         uint32_t custom_mask = ~0;
 314
 315         if (!has(defs->flags, family, table))
 316                 return;
 317
 318         /* don't touch user chains on selective stop */
 319         if (reload)
 320                 delbit(custom_mask, FW3_DEFAULT_CUSTOM_CHAINS);
 321
 322         if (!pass2)
 323         {
 324                 reset_policy(table, reload ? FW3_TARGET_DROP : FW3_TARGET_ACCEPT);
 325
 326                 fw3_pr_rulespec(table, family, defs->flags, custom_mask,
 327                                 toplevel_rules, "-D %s\n");
 328
 329                 fw3_pr_rulespec(table, family, defs->flags, custom_mask,
 330                                 default_chains, "-F %s\n");
 331         }
 332         else
 333         {
 334                 fw3_pr_rulespec(table, family, defs->flags, custom_mask,
 335                                 default_chains, "-X %s\n");
 336
 337                 del(defs->flags, family, table);
 338         }
 339 }
 340
 341 void
 342 fw3_flush_all(enum fw3_table table)
 343 {
 344         reset_policy(table, FW3_TARGET_ACCEPT);
 345
 346         fw3_pr("-F\n");
 347         fw3_pr("-X\n");
 348 }