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#include "first.h"
#include "base.h"
#include "log.h"
#include "buffer.h"
#include "http_header.h"
#include "sock_addr.h"
#include "plugin.h"
#include <stdlib.h>
#include <string.h>
/**
* mod_evasive
*
* A combination of lighttpd modules provides similar features
* to those in (old) Apache mod_evasive
*
* - limit of connections per IP
* ==> mod_evasive
* - provide a list of block-listed ip/networks (no access)
* ==> block at firewall
* ==> block using lighttpd.conf conditionals and mod_access
* ==> block using mod_magnet and an external (updatable) constant database
* https://wiki.lighttpd.net/AbsoLUAtion#Fight-DDoS
* - provide a white-list of ips/network which is not affected by the limit
* ==> allow using lighttpd.conf conditionals
* and configure evasive.max-conns-per-ip = 0 for whitelist
* - provide a bandwidth limiter per IP
* ==> set using lighttpd.conf conditionals
* and configure connection.kbytes-per-second
* - enforce additional policy using mod_magnet and libmodsecurity
* ==> https://wiki.lighttpd.net/AbsoLUAtion#Mod_Security
*
* started by:
* - w1zzard@techpowerup.com
*/
typedef struct {
unsigned short max_conns;
unsigned short silent;
const buffer *location;
} plugin_config;
typedef struct {
PLUGIN_DATA;
plugin_config defaults;
plugin_config conf;
} plugin_data;
INIT_FUNC(mod_evasive_init) {
return calloc(1, sizeof(plugin_data));
}
static void mod_evasive_merge_config_cpv(plugin_config * const pconf, const config_plugin_value_t * const cpv) {
switch (cpv->k_id) { /* index into static config_plugin_keys_t cpk[] */
case 0: /* evasive.max-conns-per-ip */
pconf->max_conns = cpv->v.shrt;
break;
case 1: /* evasive.silent */
pconf->silent = (0 != cpv->v.u);
break;
case 2: /* evasive.location */
pconf->location = cpv->v.b;
break;
default:/* should not happen */
return;
}
}
static void mod_evasive_merge_config(plugin_config * const pconf, const config_plugin_value_t *cpv) {
do {
mod_evasive_merge_config_cpv(pconf, cpv);
} while ((++cpv)->k_id != -1);
}
static void mod_evasive_patch_config(request_st * const r, plugin_data * const p) {
p->conf = p->defaults; /* copy small struct instead of memcpy() */
/*memcpy(&p->conf, &p->defaults, sizeof(plugin_config));*/
for (int i = 1, used = p->nconfig; i < used; ++i) {
if (config_check_cond(r, (uint32_t)p->cvlist[i].k_id))
mod_evasive_merge_config(&p->conf,p->cvlist + p->cvlist[i].v.u2[0]);
}
}
SETDEFAULTS_FUNC(mod_evasive_set_defaults) {
static const config_plugin_keys_t cpk[] = {
{ CONST_STR_LEN("evasive.max-conns-per-ip"),
T_CONFIG_SHORT,
T_CONFIG_SCOPE_CONNECTION }
,{ CONST_STR_LEN("evasive.silent"),
T_CONFIG_BOOL,
T_CONFIG_SCOPE_CONNECTION }
,{ CONST_STR_LEN("evasive.location"),
T_CONFIG_STRING,
T_CONFIG_SCOPE_CONNECTION }
,{ NULL, 0,
T_CONFIG_UNSET,
T_CONFIG_SCOPE_UNSET }
};
plugin_data * const p = p_d;
if (!config_plugin_values_init(srv, p, cpk, "mod_evasive"))
return HANDLER_ERROR;
/* process and validate config directives
* (init i to 0 if global context; to 1 to skip empty global context) */
for (int i = !p->cvlist[0].v.u2[1]; i < p->nconfig; ++i) {
config_plugin_value_t *cpv = p->cvlist + p->cvlist[i].v.u2[0];
for (; -1 != cpv->k_id; ++cpv) {
switch (cpv->k_id) {
case 0: /* evasive.max-conns-per-ip */
case 1: /* evasive.silent */
break;
case 2: /* evasive.location */
if (buffer_is_blank(cpv->v.b))
cpv->v.b = NULL;
break;
default:/* should not happen */
break;
}
}
}
/* initialize p->defaults from global config context */
if (p->nconfig > 0 && p->cvlist->v.u2[1]) {
const config_plugin_value_t *cpv = p->cvlist + p->cvlist->v.u2[0];
if (-1 != cpv->k_id)
mod_evasive_merge_config(&p->defaults, cpv);
}
return HANDLER_GO_ON;
}
__attribute_cold__
__attribute_noinline__
static handler_t
mod_evasive_reached_per_ip_limit (request_st * const r, const plugin_data * const p)
{
if (!p->conf.silent) {
log_error(r->conf.errh, __FILE__, __LINE__,
"%s turned away. Too many connections.",
r->con->dst_addr_buf.ptr);
}
if (p->conf.location) {
http_header_response_set(r, HTTP_HEADER_LOCATION,
CONST_STR_LEN("Location"),
BUF_PTR_LEN(p->conf.location));
r->http_status = 302;
r->resp_body_finished = 1;
} else {
r->http_status = 403;
}
r->handler_module = NULL;
return HANDLER_FINISHED;
}
static handler_t
mod_evasive_check_per_ip_limit (request_st * const r, const plugin_data * const p, const connection *c)
{
const sock_addr * const dst_addr = &r->con->dst_addr;
for (uint_fast32_t conns_by_ip = 0; c; c = c->next) {
/* count connections already actively serving data for the same IP
* (only count connections already behind the 'read request' state) */
if (c->request.state > CON_STATE_REQUEST_END
&& sock_addr_is_addr_eq(&c->dst_addr, dst_addr)
&& ++conns_by_ip > p->conf.max_conns)
return mod_evasive_reached_per_ip_limit(r, p);/* HANDLER_FINISHED */
}
return HANDLER_GO_ON;
}
URIHANDLER_FUNC(mod_evasive_uri_handler) {
plugin_data * const p = p_d;
mod_evasive_patch_config(r, p);
return (p->conf.max_conns == 0) /* no limit set, nothing to block */
? HANDLER_GO_ON
: mod_evasive_check_per_ip_limit(r, p, r->con->srv->conns);
}
int mod_evasive_plugin_init(plugin *p);
int mod_evasive_plugin_init(plugin *p) {
p->version = LIGHTTPD_VERSION_ID;
p->name = "evasive";
p->init = mod_evasive_init;
p->set_defaults = mod_evasive_set_defaults;
p->handle_uri_clean = mod_evasive_uri_handler;
return 0;
}
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