ircd/IPcheck.c

   1 /*
   2  * IRC - Internet Relay Chat, ircd/IPcheck.c
   3  * Copyright (C) 1998 Carlo Wood ( Run @ undernet.org )
   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 as published by
   7  * the Free Software Foundation; either version 2, or (at your option)
   8  * any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  */
  19 /** @file
  20  * @brief Code to count users connected from particular IP addresses.
  21  * @version $Id: IPcheck.c,v 1.40 2005/08/15 23:22:50 entrope Exp $
  22  */
  23 #include "config.h"
  24
  25 #include "IPcheck.h"
  26 #include "client.h"
  27 #include "ircd.h"
  28 #include "match.h"
  29 #include "msg.h"
  30 #include "ircd_alloc.h"
  31 #include "ircd_events.h"
  32 #include "ircd_features.h"
  33 #include "ircd_log.h"
  34 #include "ircd_string.h"    /* ircd_ntoa */
  35 #include "s_debug.h"        /* Debug */
  36 #include "s_user.h"         /* TARGET_DELAY */
  37 #include "send.h"
  38
  39 /* #include <assert.h> -- Now using assert in ircd_log.h */
  40 #include <string.h>
  41
  42 /** Stores free target information for a particular user. */
  43 struct IPTargetEntry {
  44   unsigned int  count; /**< Number of free targets targets. */
  45   unsigned char targets[MAXTARGETS]; /**< Array of recent targets. */
  46 };
  47
  48 /** Stores recent information about a particular IP address. */
  49 struct IPRegistryEntry {
  50   struct IPRegistryEntry*  next;   /**< Next entry in the hash chain. */
  51   struct IPTargetEntry*    target; /**< Recent targets, if any. */
  52   struct irc_in_addr       addr;   /**< IP address for this user. */
  53   int                      last_connect; /**< Last connection attempt timestamp. */
  54   unsigned short           connected; /**< Number of currently connected clients. */
  55   unsigned char            attempts; /**< Number of recent connection attempts. */
  56 };
  57
  58 /** Size of hash table (must be a power of two). */
  59 #define IP_REGISTRY_TABLE_SIZE 0x10000
  60 /** Report current time for tracking in IPRegistryEntry::last_connect. */
  61 #define NOW ((unsigned short)(CurrentTime & 0xffff))
  62 /** Time from \a x until now, in seconds. */
  63 #define CONNECTED_SINCE(x) (NOW - (x))
  64
  65 /** Macro for easy access to configured IPcheck clone limit. */
  66 #define IPCHECK_CLONE_LIMIT feature_int(FEAT_IPCHECK_CLONE_LIMIT)
  67 /** Macro for easy access to configured IPcheck clone period. */
  68 #define IPCHECK_CLONE_PERIOD feature_int(FEAT_IPCHECK_CLONE_PERIOD)
  69 /** Macro for easy access to configured IPcheck clone delay. */
  70 #define IPCHECK_CLONE_DELAY feature_int(FEAT_IPCHECK_CLONE_DELAY)
  71
  72 /** Hash table for storing IPRegistryEntry entries. */
  73 static struct IPRegistryEntry* hashTable[IP_REGISTRY_TABLE_SIZE];
  74 /** List of allocated but unused IPRegistryEntry structs. */
  75 static struct IPRegistryEntry* freeList;
  76 /** Periodic timer to look for too-old registry entries. */
  77 static struct Timer expireTimer;
  78
  79 /** Convert IP addresses to canonical form for comparison.  IPv4
  80  * addresses are translated into 6to4 form; IPv6 addresses are left
  81  * alone.
  82  * @param[out] out Receives canonical format for address.
  83  * @param[in] in IP address to canonicalize.
  84  */
  85 static void ip_registry_canonicalize(struct irc_in_addr *out, const struct irc_in_addr *in)
  86 {
  87     if (irc_in_addr_is_ipv4(in)) {
  88         out->in6_16[0] = htons(0x2002);
  89         out->in6_16[1] = in->in6_16[6];
  90         out->in6_16[2] = in->in6_16[7];
  91         out->in6_16[3] = out->in6_16[4] = out->in6_16[5] = 0;
  92         out->in6_16[6] = out->in6_16[7] = 0;
  93     } else
  94         memcpy(out, in, sizeof(*out));
  95 }
  96
  97 /** Calculate hash value for an IP address.
  98  * @param[in] ip Address to hash; must be in canonical form.
  99  * @return Hash value for address.
 100  */
 101 static unsigned int ip_registry_hash(const struct irc_in_addr *ip)
 102 {
 103   unsigned int res;
 104   /* Only use the first 64 bits of address, since the last 64 bits
 105    * tend to be under user control. */
 106   res = ip->in6_16[0] ^ ip->in6_16[1] ^ ip->in6_16[2] ^ ip->in6_16[3];
 107   return res & (IP_REGISTRY_TABLE_SIZE - 1);
 108 }
 109
 110 /** Find an IP registry entry if one exists for the IP address.
 111  * If \a ip looks like an IPv6 address, only consider the first 64 bits
 112  * of the address. Otherwise, only consider the final 32 bits.
 113  * @param[in] ip IP address to search for.
 114  * @return Matching registry entry, or NULL if none exists.
 115  */
 116 static struct IPRegistryEntry* ip_registry_find(const struct irc_in_addr *ip)
 117 {
 118   struct irc_in_addr canon;
 119   struct IPRegistryEntry* entry;
 120   ip_registry_canonicalize(&canon, ip);
 121   entry = hashTable[ip_registry_hash(&canon)];
 122   for ( ; entry; entry = entry->next) {
 123     int bits = (canon.in6_16[0] == htons(0x2002)) ? 48 : 64;
 124     if (ipmask_check(&canon, &entry->addr, bits))
 125       break;
 126   }
 127   return entry;
 128 }
 129
 130 /** Add an IP registry entry to the hash table.
 131  * @param[in] entry Registry entry to add.
 132  */
 133 static void ip_registry_add(struct IPRegistryEntry* entry)
 134 {
 135   unsigned int bucket = ip_registry_hash(&entry->addr);
 136   entry->next = hashTable[bucket];
 137   hashTable[bucket] = entry;
 138 }
 139
 140 /** Remove an IP registry entry from the hash table.
 141  * @param[in] entry Registry entry to add.
 142  */
 143 static void ip_registry_remove(struct IPRegistryEntry* entry)
 144 {
 145   unsigned int bucket = ip_registry_hash(&entry->addr);
 146   if (hashTable[bucket] == entry)
 147     hashTable[bucket] = entry->next;
 148   else {
 149     struct IPRegistryEntry* prev = hashTable[bucket];
 150     for ( ; prev; prev = prev->next) {
 151       if (prev->next == entry) {
 152         prev->next = entry->next;
 153         break;
 154       }
 155     }
 156   }
 157 }
 158
 159 /** Allocate a new IP registry entry.
 160  * For members that have a sensible default value, that is used.
 161  * @return Newly allocated registry entry.
 162  */
 163 static struct IPRegistryEntry* ip_registry_new_entry(void)
 164 {
 165   struct IPRegistryEntry* entry = freeList;
 166   if (entry)
 167     freeList = entry->next;
 168   else
 169     entry = (struct IPRegistryEntry*) MyMalloc(sizeof(struct IPRegistryEntry));
 170
 171   assert(0 != entry);
 172   memset(entry, 0, sizeof(struct IPRegistryEntry));
 173   entry->last_connect = NOW;     /* Seconds since last connect attempt */
 174   entry->connected    = 1;       /* connected clients for this IP */
 175   entry->attempts     = 1;       /* Number attempts for this IP */
 176   return entry;
 177 }
 178
 179 /** Deallocate memory for \a entry.
 180  * The entry itself is prepended to #freeList.
 181  * @param[in] entry IP registry entry to release.
 182  */
 183 static void ip_registry_delete_entry(struct IPRegistryEntry* entry)
 184 {
 185   if (entry->target)
 186     MyFree(entry->target);
 187   entry->next = freeList;
 188   freeList = entry;
 189 }
 190
 191 /** Update free target count for \a entry.
 192  * @param[in,out] entry IP registry entry to update.
 193  */
 194 static unsigned int ip_registry_update_free_targets(struct IPRegistryEntry* entry)
 195 {
 196   unsigned int free_targets = STARTTARGETS;
 197
 198   if (entry->target) {
 199     free_targets = entry->target->count + (CONNECTED_SINCE(entry->last_connect) / TARGET_DELAY);
 200     if (free_targets > STARTTARGETS)
 201       free_targets = STARTTARGETS;
 202     entry->target->count = free_targets;
 203   }
 204   return free_targets;
 205 }
 206
 207 /** Check whether all or part of \a entry needs to be expired.
 208  * If the entry is at least 600 seconds stale, free the entire thing.
 209  * If it is at least 120 seconds stale, expire its free targets list.
 210  * @param[in] entry Registry entry to check for expiration.
 211  */
 212 static void ip_registry_expire_entry(struct IPRegistryEntry* entry)
 213 {
 214   /*
 215    * Don't touch this number, it has statistical significance
 216    * XXX - blah blah blah
 217    */
 218   if (CONNECTED_SINCE(entry->last_connect) > 600) {
 219     /*
 220      * expired
 221      */
 222     Debug((DEBUG_DNS, "IPcheck expiring registry for %s (no clients connected).", ircd_ntoa(&entry->addr)));
 223     ip_registry_remove(entry);
 224     ip_registry_delete_entry(entry);
 225   }
 226   else if (CONNECTED_SINCE(entry->last_connect) > 120 && 0 != entry->target) {
 227     /*
 228      * Expire storage of targets
 229      */
 230     MyFree(entry->target);
 231     entry->target = 0;
 232   }
 233 }
 234
 235 /** Periodic timer callback to check for expired registry entries.
 236  * @param[in] ev Timer event (ignored).
 237  */
 238 static void ip_registry_expire(struct Event* ev)
 239 {
 240   int i;
 241   struct IPRegistryEntry* entry;
 242   struct IPRegistryEntry* entry_next;
 243
 244   assert(ET_EXPIRE == ev_type(ev));
 245   assert(0 != ev_timer(ev));
 246
 247   for (i = 0; i < IP_REGISTRY_TABLE_SIZE; ++i) {
 248     for (entry = hashTable[i]; entry; entry = entry_next) {
 249       entry_next = entry->next;
 250       if (0 == entry->connected)
 251         ip_registry_expire_entry(entry);
 252     }
 253   }
 254 }
 255
 256 /** Initialize the IPcheck subsystem. */
 257 void IPcheck_init(void)
 258 {
 259   timer_add(timer_init(&expireTimer), ip_registry_expire, 0, TT_PERIODIC, 60);
 260 }
 261
 262 /** Check whether a new connection from a local client should be allowed.
 263  * A connection is rejected if someone from the "same" address (see
 264  * ip_registry_find()) connects IPCHECK_CLONE_LIMIT times, each time
 265  * separated by no more than IPCHECK_CLONE_PERIOD seconds.
 266  * @param[in] addr Address of client.
 267  * @param[out] next_target_out Receives time to grant another free target.
 268  * @return Non-zero if the connection is permitted, zero if denied.
 269  */
 270 int ip_registry_check_local(const struct irc_in_addr *addr, time_t* next_target_out)
 271 {
 272   struct IPRegistryEntry* entry = ip_registry_find(addr);
 273   unsigned int free_targets = STARTTARGETS;
 274
 275   if (0 == entry) {
 276     entry       = ip_registry_new_entry();
 277     ip_registry_canonicalize(&entry->addr, addr);
 278     ip_registry_add(entry);
 279     Debug((DEBUG_DNS, "IPcheck added new registry for local connection from %s.", ircd_ntoa(&entry->addr)));
 280     return 1;
 281   }
 282   /* Note that this also counts server connects.
 283    * It is hard and not interesting, to change that.
 284    * Refuse connection if it would overflow the counter.
 285    */
 286   if (0 == ++entry->connected)
 287   {
 288     entry->connected--;
 289     Debug((DEBUG_DNS, "IPcheck refusing local connection from %s: counter overflow.", ircd_ntoa(&entry->addr)));
 290     return 0;
 291   }
 292
 293   if (CONNECTED_SINCE(entry->last_connect) > IPCHECK_CLONE_PERIOD)
 294     entry->attempts = 0;
 295
 296   free_targets = ip_registry_update_free_targets(entry);
 297   entry->last_connect = NOW;
 298
 299   if (0 == ++entry->attempts)   /* Check for overflow */
 300     --entry->attempts;
 301
 302   if (entry->attempts < IPCHECK_CLONE_LIMIT) {
 303     if (next_target_out)
 304       *next_target_out = CurrentTime - (TARGET_DELAY * free_targets - 1);
 305   }
 306   else if ((CurrentTime - cli_since(&me)) > IPCHECK_CLONE_DELAY) {
 307     /*
 308      * Don't refuse connection when we just rebooted the server
 309      */
 310 #ifndef NOTHROTTLE
 311     assert(entry->connected > 0);
 312     --entry->connected;
 313     Debug((DEBUG_DNS, "IPcheck refusing local connection from %s: too fast.", ircd_ntoa(&entry->addr)));
 314     return 0;
 315 #endif
 316   }
 317   Debug((DEBUG_DNS, "IPcheck accepting local connection from %s.", ircd_ntoa(&entry->addr)));
 318   return 1;
 319 }
 320
 321 /** Check whether a connection from a remote client should be allowed.
 322  * This is much more relaxed than ip_registry_check_local(): The only
 323  * cause for rejection is when the IPRegistryEntry::connected counter
 324  * would overflow.
 325  * @param[in] cptr Client that has connected.
 326  * @param[in] is_burst Non-zero if client was introduced during a burst.
 327  * @return Non-zero if the client should be accepted, zero if they must be killed.
 328  */
 329 int ip_registry_check_remote(struct Client* cptr, int is_burst)
 330 {
 331   struct IPRegistryEntry* entry;
 332
 333   /*
 334    * Mark that we did add/update an IPregistry entry
 335    */
 336   SetIPChecked(cptr);
 337   if (!irc_in_addr_valid(&cli_ip(cptr))) {
 338     Debug((DEBUG_DNS, "IPcheck accepting remote connection from invalid %s.", ircd_ntoa(&cli_ip(cptr))));
 339     return 1;
 340   }
 341   entry = ip_registry_find(&cli_ip(cptr));
 342   if (0 == entry) {
 343     entry = ip_registry_new_entry();
 344     ip_registry_canonicalize(&entry->addr, &cli_ip(cptr));
 345     if (is_burst)
 346       entry->attempts = 0;
 347     ip_registry_add(entry);
 348     Debug((DEBUG_DNS, "IPcheck added new registry for remote connection from %s.", ircd_ntoa(&entry->addr)));
 349     return 1;
 350   }
 351   /* Avoid overflowing the connection counter. */
 352   if (0 == ++entry->connected) {
 353     Debug((DEBUG_DNS, "IPcheck refusing remote connection from %s: counter overflow.", ircd_ntoa(&entry->addr)));
 354     return 0;
 355   }
 356   if (CONNECTED_SINCE(entry->last_connect) > IPCHECK_CLONE_PERIOD)
 357     entry->attempts = 0;
 358   if (!is_burst) {
 359     if (0 == ++entry->attempts) {
 360       /*
 361        * Check for overflow
 362        */
 363       --entry->attempts;
 364     }
 365     ip_registry_update_free_targets(entry);
 366     entry->last_connect = NOW;
 367   }
 368   Debug((DEBUG_DNS, "IPcheck counting remote connection from %s.", ircd_ntoa(&entry->addr)));
 369   return 1;
 370 }
 371
 372 /** Handle a client being rejected during connection through no fault
 373  * of their own.  This "undoes" the effect of ip_registry_check_local()
 374  * so the client's address is not penalized for the failure.
 375  * @param[in] addr Address of rejected client.
 376  */
 377 void ip_registry_connect_fail(const struct irc_in_addr *addr)
 378 {
 379   struct IPRegistryEntry* entry = ip_registry_find(addr);
 380   if (entry && 0 == --entry->attempts) {
 381     Debug((DEBUG_DNS, "IPcheck noting local connection failure for %s.", ircd_ntoa(&entry->addr)));
 382     ++entry->attempts;
 383   }
 384 }
 385
 386 /** Handle a client that has successfully connected.
 387  * This copies free target information to \a cptr from his address's
 388  * registry entry and sends him a NOTICE describing the parameters for
 389  * the entry.
 390  * @param[in,out] cptr Client that has successfully connected.
 391  */
 392 void ip_registry_connect_succeeded(struct Client *cptr)
 393 {
 394   const char*             tr    = "";
 395   unsigned int free_targets     = STARTTARGETS;
 396   struct IPRegistryEntry* entry = ip_registry_find(&cli_ip(cptr));
 397
 398   assert(entry);
 399   if (entry->target) {
 400     memcpy(cli_targets(cptr), entry->target->targets, MAXTARGETS);
 401     free_targets = entry->target->count;
 402     tr = " tr";
 403   }
 404   Debug((DEBUG_DNS, "IPcheck noting local connection success for %s.", ircd_ntoa(&entry->addr)));
 405   sendcmdto_one(&me, CMD_NOTICE, cptr, "%C :on %u ca %u(%u) ft %u(%u)%s",
 406                 cptr, entry->connected, entry->attempts, IPCHECK_CLONE_LIMIT,
 407                 free_targets, STARTTARGETS, tr);
 408 }
 409
 410 /** Handle a client that decided to disconnect (or was killed after
 411  * completing his connection).  This updates the free target
 412  * information for his IP registry entry.
 413  * @param[in] cptr Client that has exited.
 414  */
 415 void ip_registry_disconnect(struct Client *cptr)
 416 {
 417   struct IPRegistryEntry* entry = ip_registry_find(&cli_ip(cptr));
 418   if (!irc_in_addr_valid(&cli_ip(cptr))) {
 419     Debug((DEBUG_DNS, "IPcheck noting dicconnect from invalid %s.", ircd_ntoa(&cli_ip(cptr))));
 420     return;
 421   }
 422   assert(entry);
 423   assert(entry->connected > 0);
 424   Debug((DEBUG_DNS, "IPcheck noting disconnect from %s.", ircd_ntoa(&entry->addr)));
 425   /*
 426    * If this was the last one, set `last_connect' to disconnect time (used for expiration)
 427    */
 428   if (0 == --entry->connected) {
 429     if (CONNECTED_SINCE(entry->last_connect) > IPCHECK_CLONE_LIMIT * IPCHECK_CLONE_PERIOD) {
 430       /*
 431        * Otherwise we'd penalize for this old value if the client reconnects within 20 seconds
 432        */
 433       entry->attempts = 0;
 434     }
 435     ip_registry_update_free_targets(entry);
 436     entry->last_connect = NOW;
 437   }
 438   if (MyConnect(cptr)) {
 439     unsigned int free_targets;
 440     /*
 441      * Copy the clients targets
 442      */
 443     if (0 == entry->target) {
 444       entry->target = (struct IPTargetEntry*) MyMalloc(sizeof(struct IPTargetEntry));
 445       entry->target->count = STARTTARGETS;
 446     }
 447     assert(0 != entry->target);
 448
 449     memcpy(entry->target->targets, cli_targets(cptr), MAXTARGETS);
 450     /*
 451      * This calculation can be pretty unfair towards large multi-user hosts, but
 452      * there is "nothing" we can do without also allowing spam bots to send more
 453      * messages or by drastically increasing the amount of memory used in the IPregistry.
 454      *
 455      * The problem is that when a client disconnects, leaving no free targets, then
 456      * the next client from that IP number has to pay for it (getting no free targets).
 457      * But ALSO the next client, and the next client, and the next client etc - until
 458      * another client disconnects that DOES leave free targets.  The reason for this
 459      * is that if there are 10 SPAM bots, and they all disconnect at once, then they
 460      * ALL should get no free targets when reconnecting.  We'd need to store an entry
 461      * per client (instead of per IP number) to avoid this.
 462      */
 463     if (cli_nexttarget(cptr) < CurrentTime) {
 464         /*
 465          * Number of free targets
 466          */
 467       free_targets = (CurrentTime - cli_nexttarget(cptr)) / TARGET_DELAY + 1;
 468     }
 469     else
 470       free_targets = 0;
 471     /*
 472      * Add bonus, this is pretty fuzzy, but it will help in some cases.
 473      */
 474     if ((CurrentTime - cli_firsttime(cptr)) > 600)
 475       /*
 476        * Was longer then 10 minutes online?
 477        */
 478       free_targets += (CurrentTime - cli_firsttime(cptr) - 600) / TARGET_DELAY;
 479     /*
 480      * Finally, store smallest value for Judgment Day
 481      */
 482     if (free_targets < entry->target->count)
 483       entry->target->count = free_targets;
 484   }
 485 }
 486
 487 /** Find number of clients from a particular IP address.
 488  * @param[in] addr Address to look up.
 489  * @return Number of clients known to be connected from that address.
 490  */
 491 int ip_registry_count(const struct irc_in_addr *addr)
 492 {
 493   struct IPRegistryEntry* entry = ip_registry_find(addr);
 494   return (entry) ? entry->connected : 0;
 495 }
 496
 497 /** Check whether a client is allowed to connect locally.
 498  * @param[in] a Address of client.
 499  * @param[out] next_target_out Receives time to grant another free target.
 500  * @return Non-zero if the connection is permitted, zero if denied.
 501  */
 502 int IPcheck_local_connect(const struct irc_in_addr *a, time_t* next_target_out)
 503 {
 504   assert(0 != next_target_out);
 505   return ip_registry_check_local(a, next_target_out);
 506 }
 507
 508 /** Check whether a client is allowed to connect remotely.
 509  * @param[in] cptr Client that has connected.
 510  * @param[in] is_burst Non-zero if client was introduced during a burst.
 511  * @return Non-zero if the client should be accepted, zero if they must be killed.
 512  */
 513 int IPcheck_remote_connect(struct Client *cptr, int is_burst)
 514 {
 515   assert(0 != cptr);
 516   assert(!IsIPChecked(cptr));
 517   return ip_registry_check_remote(cptr, is_burst);
 518 }
 519
 520 /** Handle a client being rejected during connection through no fault
 521  * of their own.  This "undoes" the effect of ip_registry_check_local()
 522  * so the client's address is not penalized for the failure.
 523  * @param[in] cptr Client who has been rejected.
 524  */
 525 void IPcheck_connect_fail(const struct Client *cptr)
 526 {
 527   assert(IsIPChecked(cptr));
 528   ip_registry_connect_fail(&cli_ip(cptr));
 529 }
 530
 531 /** Handle a client that has successfully connected.
 532  * This copies free target information to \a cptr from his address's
 533  * registry entry and sends him a NOTICE describing the parameters for
 534  * the entry.
 535  * @param[in,out] cptr Client that has successfully connected.
 536  */
 537 void IPcheck_connect_succeeded(struct Client *cptr)
 538 {
 539   assert(0 != cptr);
 540   assert(IsIPChecked(cptr));
 541   ip_registry_connect_succeeded(cptr);
 542 }
 543
 544 /** Handle a client that decided to disconnect (or was killed after
 545  * completing his connection).  This updates the free target
 546  * information for his IP registry entry.
 547  * @param[in] cptr Client that has exited.
 548  */
 549 void IPcheck_disconnect(struct Client *cptr)
 550 {
 551   assert(0 != cptr);
 552   assert(IsIPChecked(cptr));
 553   ip_registry_disconnect(cptr);
 554 }
 555
 556 /** Find number of clones of a client.
 557  * @param[in] cptr Client whose address to look up.
 558  * @return Number of clients known to be connected from that address.
 559  */
 560 unsigned short IPcheck_nr(struct Client *cptr)
 561 {
 562   assert(0 != cptr);
 563   return ip_registry_count(&cli_ip(cptr));
 564 }