/*
* IRC - Internet Relay Chat, ircd/IPcheck.c
* Copyright (C) 1998 Carlo Wood ( Run @ undernet.org )
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/** @file
* @brief Code to count users connected from particular IP addresses.
* @version $Id: IPcheck.c 1098 2005-06-22 14:57:07Z sirvulcan $
*/
#include "config.h"
#include "IPcheck.h"
#include "client.h"
#include "ircd.h"
#include "msg.h"
#include "numnicks.h"
#include "ircd_alloc.h"
#include "ircd_events.h"
#include "ircd_features.h"
#include "s_debug.h"
#include "s_user.h"
#include "send.h"
#include "ssl.h"
#include <assert.h>
#include <string.h>
/** Stores free target information for a particular user. */
struct IPTargetEntry {
int count; /**< Number of free targets targets. */
unsigned char targets[MAXTARGETS]; /**< Array of recent targets. */
};
/** Stores recent information about a particular IP address. */
struct IPRegistryEntry {
struct IPRegistryEntry* next; /**< Next entry in the hash chain. */
struct IPTargetEntry* target; /**< Recent targets, if any. */
unsigned int addr; /**< IP address for this user. */
int last_connect; /**< Last connection attempt timestamp. */
unsigned short connected; /**< Number of currently connected clients. */
unsigned char attempts; /**< Number of recent connection attempts. */
};
/** Size of hash table (must be a power of two). */
#define IP_REGISTRY_TABLE_SIZE 0x10000
/** Report current time for tracking in IPRegistryEntry::last_connect. */
#define NOW ((unsigned short)(CurrentTime & 0xffff))
/** Time from \a x until now, in seconds. */
#define CONNECTED_SINCE(x) (NOW - (x))
/** Macro for easy access to configured IPcheck clone limit. */
#define IPCHECK_CLONE_LIMIT feature_int(FEAT_IPCHECK_CLONE_LIMIT)
/** Macro for easy access to configured IPcheck clone period. */
#define IPCHECK_CLONE_PERIOD feature_int(FEAT_IPCHECK_CLONE_PERIOD)
/** Macro for easy access to configured IPcheck clone delay. */
#define IPCHECK_CLONE_DELAY feature_int(FEAT_IPCHECK_CLONE_DELAY)
/** Hash table for storing IPRegistryEntry entries. */
static struct IPRegistryEntry* hashTable[IP_REGISTRY_TABLE_SIZE];
/** List of allocated but unused IPRegistryEntry structs. */
static struct IPRegistryEntry* freeList = 0;
/** Periodic timer to look for too-old registry entries. */
static struct Timer expireTimer;
/** Calculate hash value for an IP address.
* @param[in] ip Address to hash.
* @return Hash value for address.
*/
static unsigned int ip_registry_hash(unsigned int ip)
{
return ((ip >> 16) ^ ip) & (IP_REGISTRY_TABLE_SIZE - 1);
}
/** Find an IP registry entry if one exists for the IP address.
* @param[in] ip IP address to search for.
* @return Matching registry entry, or NULL if none exists.
*/
static struct IPRegistryEntry* ip_registry_find(unsigned int ip)
{
struct IPRegistryEntry* entry = hashTable[ip_registry_hash(ip)];
for ( ; entry; entry = entry->next) {
if (entry->addr == ip)
break;
}
return entry;
}
/** Add an IP registry entry to the hash table.
* @param[in] entry Registry entry to add.
*/
static void ip_registry_add(struct IPRegistryEntry* entry)
{
unsigned int bucket = ip_registry_hash(entry->addr);
entry->next = hashTable[bucket];
hashTable[bucket] = entry;
}
/** Remove an IP registry entry from the hash table.
* @param[in] entry Registry entry to add.
*/
static void ip_registry_remove(struct IPRegistryEntry* entry)
{
unsigned int bucket = ip_registry_hash(entry->addr);
if (hashTable[bucket] == entry)
hashTable[bucket] = entry->next;
else {
struct IPRegistryEntry* prev = hashTable[bucket];
for ( ; prev; prev = prev->next) {
if (prev->next == entry) {
prev->next = entry->next;
break;
}
}
}
}
/** Allocate a new IP registry entry.
* For members that have a sensible default value, that is used.
* @return Newly allocated registry entry.
*/
static struct IPRegistryEntry* ip_registry_new_entry()
{
struct IPRegistryEntry* entry = freeList;
if (entry)
freeList = entry->next;
else
entry = (struct IPRegistryEntry*) MyMalloc(sizeof(struct IPRegistryEntry));
assert(0 != entry);
memset(entry, 0, sizeof(struct IPRegistryEntry));
entry->last_connect = NOW; /* Seconds since last connect attempt */
entry->connected = 1; /* connected clients for this IP */
entry->attempts = 1; /* Number attempts for this IP */
return entry;
}
/** Deallocate memory for \a entry.
* The entry itself is prepended to #freeList.
* @param[in] entry IP registry entry to release.
*/
static void ip_registry_delete_entry(struct IPRegistryEntry* entry)
{
if (entry->target)
MyFree(entry->target);
entry->next = freeList;
freeList = entry;
}
/** Update free target count for \a entry.
* @param[in,out] entry IP registry entry to update.
*/
static unsigned int ip_registry_update_free_targets(struct IPRegistryEntry* entry)
{
unsigned int free_targets = STARTTARGETS;
if (entry->target) {
free_targets = entry->target->count + (CONNECTED_SINCE(entry->last_connect) / TARGET_DELAY);
if (free_targets > STARTTARGETS)
free_targets = STARTTARGETS;
entry->target->count = free_targets;
}
return free_targets;
}
/** Check whether all or part of \a entry needs to be expired.
* If the entry is at least 600 seconds stale, free the entire thing.
* If it is at least 120 seconds stale, expire its free targets list.
* @param[in] entry Registry entry to check for expiration.
*/
static void ip_registry_expire_entry(struct IPRegistryEntry* entry)
{
/*
* Don't touch this number, it has statistical significance
* XXX - blah blah blah
*/
if (CONNECTED_SINCE(entry->last_connect) > 600) {
/*
* expired
*/
ip_registry_remove(entry);
ip_registry_delete_entry(entry);
}
else if (CONNECTED_SINCE(entry->last_connect) > 120 && 0 != entry->target) {
/*
* Expire storage of targets
*/
MyFree(entry->target);
entry->target = 0;
}
}
/** Periodic timer callback to check for expired registry entries.
* @param[in] ev Timer event (ignored).
*/
static void ip_registry_expire(struct Event* ev)
{
int i;
struct IPRegistryEntry* entry;
struct IPRegistryEntry* entry_next;
assert(ET_EXPIRE == ev_type(ev));
assert(0 != ev_timer(ev));
for (i = 0; i < IP_REGISTRY_TABLE_SIZE; ++i) {
for (entry = hashTable[i]; entry; entry = entry_next) {
entry_next = entry->next;
if (0 == entry->connected)
ip_registry_expire_entry(entry);
}
}
}
/** Initialize the IPcheck subsystem. */
void IPcheck_init(void)
{
timer_add(timer_init(&expireTimer), ip_registry_expire, 0, TT_PERIODIC, 60);
}
/** Check whether a new connection from a local client should be allowed.
* A connection is rejected if someone from the "same" address (see
* ip_registry_find()) connects IPCHECK_CLONE_LIMIT times, each time
* separated by no more than IPCHECK_CLONE_PERIOD seconds.
* @param[in] addr Address of client.
* @param[out] next_target_out Receives time to grant another free target.
* @return Non-zero if the connection is permitted, zero if denied.
*/
int ip_registry_check_local(unsigned int addr, time_t* next_target_out)
{
struct IPRegistryEntry* entry = ip_registry_find(addr);
unsigned int free_targets = STARTTARGETS;
if (0 == entry) {
entry = ip_registry_new_entry();
entry->addr = addr; /* The IP number of registry entry */
ip_registry_add(entry);
return 1;
}
/* Note that this also connects server connects.
* It is hard and not interesting, to change that.
*
* Don't allow more then 255 connects from one IP number, ever
*/
if (0 == ++entry->connected) {
entry->connected--;
return 0;
}
if (CONNECTED_SINCE(entry->last_connect) > IPCHECK_CLONE_PERIOD)
entry->attempts = 0;
free_targets = ip_registry_update_free_targets(entry);
entry->last_connect = NOW;
if (0 == ++entry->attempts) /* Check for overflow */
--entry->attempts;
if (entry->attempts < IPCHECK_CLONE_LIMIT) {
if (next_target_out)
*next_target_out = CurrentTime - (TARGET_DELAY * free_targets - 1);
}
else if ((CurrentTime - cli_since(&me)) > IPCHECK_CLONE_DELAY) {
/*
* Don't refuse connection when we just rebooted the server
*/
if (feature_bool(FEAT_NOTHROTTLE))
return 1;
else {
assert(entry->connected>0);
--entry->connected;
return 0;
}
}
return 1;
}
/** Check whether a connection from a remote client should be allowed.
* This is much more relaxed than ip_registry_check_local(): The only
* cause for rejection is when the IPRegistryEntry::connected counter
* would overflow.
* @param[in] cptr Client that has connected.
* @param[in] is_burst Non-zero if client was introduced during a burst.
* @return Non-zero if the client should be accepted, zero if they must be killed.
*/
int ip_registry_check_remote(struct Client* cptr, int is_burst)
{
struct IPRegistryEntry* entry = ip_registry_find((cli_ip(cptr)).s_addr);
/*
* Mark that we did add/update an IPregistry entry
*/
SetIPChecked(cptr);
if (0 == entry) {
entry = ip_registry_new_entry();
entry->addr = (cli_ip(cptr)).s_addr;
if (is_burst)
entry->attempts = 0;
ip_registry_add(entry);
}
else {
if (0 == ++entry->connected) {
/*
* Don't allow more then 255 connects from one IP number, ever
*/
return 0;
}
if (CONNECTED_SINCE(entry->last_connect) > IPCHECK_CLONE_PERIOD)
entry->attempts = 0;
if (!is_burst) {
if (0 == ++entry->attempts) {
/*
* Check for overflow
*/
--entry->attempts;
}
ip_registry_update_free_targets(entry);
entry->last_connect = NOW;
}
}
return 1;
}
/** Handle a client being rejected during connection through no fault
* of their own. This "undoes" the effect of ip_registry_check_local()
* so the client's address is not penalized for the failure.
* @param[in] addr Address of rejected client.
*/
void ip_registry_connect_fail(unsigned int addr)
{
struct IPRegistryEntry* entry = ip_registry_find(addr);
if (entry) {
if (0 == --entry->attempts)
++entry->attempts; /* check for overflow */
}
}
/** Handle a client that has successfully connected.
* This copies free target information to \a cptr from his address's
* registry entry and sends him a NOTICE describing the parameters for
* the entry.
* @param[in,out] cptr Client that has successfully connected.
*/
void ip_registry_connect_succeeded(struct Client *cptr)
{
const char* tr = "";
unsigned int free_targets = STARTTARGETS;
struct IPRegistryEntry* entry = ip_registry_find((cli_ip(cptr)).s_addr);
if (!entry) {
Debug((DEBUG_ERROR, "Missing registry entry for: %s", cli_sock_ip(cptr)));
return;
}
if (entry->target) {
memcpy(cli_targets(cptr), entry->target->targets, MAXTARGETS);
free_targets = entry->target->count;
tr = " tr";
}
sendcmdto_one(&me, CMD_NOTICE, cptr, "%C :on %u ca %u(%u) ft %u(%u)%s",
cptr, entry->connected, entry->attempts, IPCHECK_CLONE_LIMIT,
free_targets, STARTTARGETS, tr);
}
/** Handle a client that decided to disconnect (or was killed after
* completing his connection). This updates the free target
* information for his IP registry entry.
* @param[in] cptr Client that has exited.
*/
void ip_registry_disconnect(struct Client *cptr)
{
struct IPRegistryEntry* entry = ip_registry_find((cli_ip(cptr)).s_addr);
if (0 == entry) {
/*
* trying to find an entry for a server causes this to happen,
* servers should never have FLAG_IPCHECK set
*/
return;
}
/*
* If this was the last one, set `last_connect' to disconnect time (used for expiration)
*/
/* assert(entry->connected>0); */
if (0 == --entry->connected) {
if (CONNECTED_SINCE(entry->last_connect) > IPCHECK_CLONE_LIMIT * IPCHECK_CLONE_PERIOD) {
/*
* Otherwise we'd penetalize for this old value if the client reconnects within 20 seconds
*/
entry->attempts = 0;
}
ip_registry_update_free_targets(entry);
entry->last_connect = NOW;
}
if (MyConnect(cptr)) {
unsigned int free_targets;
/*
* Copy the clients targets
*/
if (0 == entry->target) {
entry->target = (struct IPTargetEntry*) MyMalloc(sizeof(struct IPTargetEntry));
entry->target->count = STARTTARGETS;
}
assert(0 != entry->target);
memcpy(entry->target->targets, cli_targets(cptr), MAXTARGETS);
/*
* This calculation can be pretty unfair towards large multi-user hosts, but
* there is "nothing" we can do without also allowing spam bots to send more
* messages or by drastically increasing the ammount of memory used in the IPregistry.
*
* The problem is that when a client disconnects, leaving no free targets, then
* the next client from that IP number has to pay for it (getting no free targets).
* But ALSO the next client, and the next client, and the next client etc - until
* another client disconnects that DOES leave free targets. The reason for this
* is that if there are 10 SPAM bots, and they all disconnect at once, then they
* ALL should get no free targets when reconnecting. We'd need to store an entry
* per client (instead of per IP number) to avoid this.
*/
if (cli_nexttarget(cptr) < CurrentTime) {
/*
* Number of free targets
*/
free_targets = (CurrentTime - cli_nexttarget(cptr)) / TARGET_DELAY + 1;
}
else
free_targets = 0;
/*
* Add bonus, this is pretty fuzzy, but it will help in some cases.
*/
if ((CurrentTime - cli_firsttime(cptr)) > 600)
/*
* Was longer then 10 minutes online?
*/
free_targets += (CurrentTime - cli_firsttime(cptr) - 600) / TARGET_DELAY;
/*
* Finally, store smallest value for Judgement Day
*/
if (free_targets < entry->target->count)
entry->target->count = free_targets;
}
}
/** Find number of clients from a particular IP address.
* @param[in] addr Address to look up.
* @return Number of clients known to be connected from that address.
*/
int ip_registry_count(unsigned int addr)
{
struct IPRegistryEntry* entry = ip_registry_find(addr);
return (entry) ? entry->connected : 0;
}
/** Check whether a client is allowed to connect locally.
* @param[in] a Address of client.
* @param[out] next_target_out Receives time to grant another free target.
* @return Non-zero if the connection is permitted, zero if denied.
*/
int IPcheck_local_connect(struct in_addr a, time_t* next_target_out)
{
assert(0 != next_target_out);
return ip_registry_check_local(a.s_addr, next_target_out);
}
/** Check whether a client is allowed to connect remotely.
* @param[in] cptr Client that has connected.
* @param[in] is_burst Non-zero if client was introduced during a burst.
* @return Non-zero if the client should be accepted, zero if they must be killed.
*/
int IPcheck_remote_connect(struct Client *cptr, int is_burst)
{
assert(0 != cptr);
return ip_registry_check_remote(cptr, is_burst);
}
/** Handle a client being rejected during connection through no fault
* of their own. This "undoes" the effect of ip_registry_check_local()
* so the client's address is not penalized for the failure.
* @param[in] a Address of rejected client.
*/
void IPcheck_connect_fail(struct in_addr a)
{
ip_registry_connect_fail(a.s_addr);
}
/** Handle a client that has successfully connected.
* This copies free target information to \a cptr from his address's
* registry entry and sends him a NOTICE describing the parameters for
* the entry.
* @param[in,out] cptr Client that has successfully connected.
*/
void IPcheck_connect_succeeded(struct Client *cptr)
{
assert(0 != cptr);
ip_registry_connect_succeeded(cptr);
}
/** Handle a client that decided to disconnect (or was killed after
* completing his connection). This updates the free target
* information for his IP registry entry.
* @param[in] cptr Client that has exited.
*/
void IPcheck_disconnect(struct Client *cptr)
{
assert(0 != cptr);
ip_registry_disconnect(cptr);
}
/** Find number of clones of a client.
* @param[in] cptr Client whose address to look up.
* @return Number of clients known to be connected from that address.
*/
unsigned short IPcheck_nr(struct Client *cptr)
{
assert(0 != cptr);
return ip_registry_count(cli_ip(cptr).s_addr);
}
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