postlicyd/greylist.c

   1 /******************************************************************************/
   2 /*          pfixtools: a collection of postfix related tools                  */
   3 /*          ~~~~~~~~~                                                         */
   4 /*  ________________________________________________________________________  */
   5 /*                                                                            */
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   7 /*  modification, are permitted provided that the following conditions        */
   8 /*  are met:                                                                  */
   9 /*                                                                            */
  10 /*  1. Redistributions of source code must retain the above copyright         */
  11 /*     notice, this list of conditions and the following disclaimer.          */
  12 /*  2. Redistributions in binary form must reproduce the above copyright      */
  13 /*     notice, this list of conditions and the following disclaimer in the    */
  14 /*     documentation and/or other materials provided with the distribution.   */
  15 /*  3. The names of its contributors may not be used to endorse or promote    */
  16 /*     products derived from this software without specific prior written     */
  17 /*     permission.                                                            */
  18 /*                                                                            */
  19 /*  THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND   */
  20 /*  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE     */
  21 /*  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR        */
  22 /*  PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS    */
  23 /*  BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR    */
  24 /*  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF      */
  25 /*  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS  */
  26 /*  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN   */
  27 /*  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)   */
  28 /*  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF    */
  29 /*  THE POSSIBILITY OF SUCH DAMAGE.                                           */
  30 /******************************************************************************/
  31
  32 /*
  33  * Copyright © 2007 Pierre Habouzit
  34  */
  35
  36 #include <tcbdb.h>
  37
  38 #include "common.h"
  39 #include "str.h"
  40
  41
  42 typedef struct greylist_config_t {
  43     unsigned lookup_by_host : 1;
  44     int delay;
  45     int retry_window;
  46     int client_awl;
  47     int max_age;
  48
  49     TCBDB *awl_db;
  50     TCBDB *obj_db;
  51 } greylist_config_t;
  52
  53 #define GREYLIST_INIT { .lookup_by_host = false,       \
  54                         .delay = 300,                  \
  55                         .retry_window = 2 * 24 * 3600, \
  56                         .client_awl = 5,               \
  57                         .max_age = 35 * 3600,          \
  58                         .awl_db = NULL,                \
  59                         .obj_db = NULL }
  60
  61 struct awl_entry {
  62     int32_t count;
  63     time_t  last;
  64 };
  65
  66 struct obj_entry {
  67     time_t first;
  68     time_t last;
  69 };
  70
  71 static inline bool greylist_check_awlentry(const greylist_config_t *config,
  72                                            struct awl_entry *aent, time_t now)
  73 {
  74     return !(config->max_age > 0 && now - aent->last > config->max_age);
  75 }
  76
  77 static inline bool greylist_check_object(const greylist_config_t *config,
  78                                          const struct obj_entry *oent, time_t now)
  79 {
  80     return !((config->max_age > 0 && now - oent->last > config->max_age)
  81              || (oent->last - oent->first < config->delay
  82                  && now - oent->last > config->retry_window));
  83 }
  84
  85 typedef bool (*db_entry_checker_t)(const greylist_config_t *, const void *, time_t);
  86
  87 static TCBDB *greylist_db_get(const greylist_config_t *config,
  88                               const char *path, bool cleanup,
  89                               size_t entry_len, db_entry_checker_t check)
  90 {
  91     TCBDB *awl_db, *tmp_db;
  92     time_t now = time(NULL);
  93
  94     /* Rebuild a new database after removing too old entries.
  95      */
  96     if (cleanup && config->max_age > 0) {
  97         uint32_t old_count = 0;
  98         uint32_t new_count = 0;
  99         bool replace = false;
 100         bool trashable = false;
 101         char tmppath[PATH_MAX];
 102         snprintf(tmppath, PATH_MAX, "%s.tmp", path);
 103
 104         info("database cleanup started");
 105         awl_db = tcbdbnew();
 106         if (tcbdbopen(awl_db, path, BDBOREADER)) {
 107             tmp_db = tcbdbnew();
 108             if (tcbdbopen(tmp_db, tmppath, BDBOWRITER | BDBOCREAT | BDBOTRUNC)) {
 109                 BDBCUR *cur = tcbdbcurnew(awl_db);
 110                 TCXSTR *key, *value;
 111
 112                 key = tcxstrnew();
 113                 value = tcxstrnew();
 114                 if (tcbdbcurfirst(cur)) {
 115                     replace = true;
 116                     do {
 117                         tcxstrclear(key);
 118                         tcxstrclear(value);
 119                         (void)tcbdbcurrec(cur, key, value);
 120
 121                         if ((size_t)tcxstrsize(value) == entry_len
 122                             && check(config, tcxstrptr(value), now)) {
 123                             tcbdbput(tmp_db, tcxstrptr(key), tcxstrsize(key),
 124                                      tcxstrptr(value), entry_len);
 125                             ++new_count;
 126                         }
 127                         ++old_count;
 128                     } while (tcbdbcurnext(cur));
 129                 }
 130                 tcxstrdel(key);
 131                 tcxstrdel(value);
 132                 tcbdbcurdel(cur);
 133                 tcbdbsync(tmp_db);
 134             } else {
 135                 warn("cannot run database cleanup: can't open destination database: %s",
 136                      tcbdberrmsg(tcbdbecode(awl_db)));
 137             }
 138             tcbdbdel(tmp_db);
 139         } else {
 140             int ecode = tcbdbecode(awl_db);
 141             warn("can not open database: %s", tcbdberrmsg(ecode));
 142             trashable = ecode != TCENOPERM && ecode != TCEOPEN && ecode != TCENOFILE && ecode != TCESUCCESS;
 143         }
 144         tcbdbdel(awl_db);
 145
 146         /** Cleanup successful, replace the old database with the new one.
 147          */
 148         if (trashable) {
 149             info("database cleanup finished: database was corrupted, create a new one");
 150             unlink(path);
 151         } else if (replace) {
 152             info("database cleanup finished: before %u entries, after %d entries",
 153                    old_count, new_count);
 154             unlink(path);
 155             if (rename(tmppath, path) != 0) {
 156                 UNIXERR("rename");
 157                 return NULL;
 158             }
 159         } else {
 160             info("database cleanup finished: nothing to do, %u entries", new_count);
 161         }
 162     }
 163
 164     /* Effectively open the database.
 165      */
 166     awl_db = tcbdbnew();
 167     if (!tcbdbopen(awl_db, path, BDBOWRITER | BDBOCREAT)) {
 168         err("can not open database: %s", tcbdberrmsg(tcbdbecode(awl_db)));
 169         tcbdbdel(awl_db);
 170         return NULL;
 171     }
 172     return awl_db;
 173 }
 174
 175
 176 static bool greylist_initialize(greylist_config_t *config,
 177                                 const char *directory, const char *prefix)
 178 {
 179     char path[PATH_MAX];
 180
 181     if (config->client_awl) {
 182         snprintf(path, sizeof(path), "%s/%swhitelist.db", directory, prefix);
 183         info("loading auto-whitelist database");
 184         config->awl_db = greylist_db_get(config, path, true,
 185                                          sizeof(struct awl_entry),
 186                                          (db_entry_checker_t)(greylist_check_awlentry));
 187         if (config->awl_db == NULL) {
 188             return false;
 189         }
 190     }
 191
 192     snprintf(path, sizeof(path), "%s/%sgreylist.db", directory, prefix);
 193     info("loading greylist database");
 194     config->obj_db = greylist_db_get(config, path, true,
 195                                      sizeof(struct obj_entry),
 196                                      (db_entry_checker_t)(greylist_check_object));
 197     if (config->obj_db == NULL) {
 198         if (config->awl_db) {
 199             tcbdbdel(config->awl_db);
 200             config->awl_db = NULL;
 201         }
 202         return false;
 203     }
 204
 205     return true;
 206 }
 207
 208 static void greylist_shutdown(greylist_config_t *config)
 209 {
 210     if (config->awl_db) {
 211         tcbdbsync(config->awl_db);
 212         tcbdbdel(config->awl_db);
 213         config->awl_db = NULL;
 214     }
 215     if (config->obj_db) {
 216         tcbdbsync(config->obj_db);
 217         tcbdbdel(config->obj_db);
 218         config->obj_db = NULL;
 219     }
 220 }
 221
 222 static const char *sender_normalize(const char *sender, char *buf, int len)
 223 {
 224     const char *at = strchr(sender, '@');
 225     int rpos = 0, wpos = 0, userlen;
 226
 227     if (!at)
 228         return sender;
 229
 230     /* strip extension used for VERP or alike */
 231     userlen = ((char *)memchr(sender, '+', at - sender) ?: at) - sender;
 232
 233     while (rpos < userlen) {
 234         int count = 0;
 235
 236         while (isdigit(sender[rpos + count]) && rpos + count < userlen)
 237             count++;
 238         if (count && !isalnum(sender[rpos + count])) {
 239             /* replace \<\d+\> with '#' */
 240             wpos += m_strputc(buf + wpos, len - wpos, '#');
 241             rpos += count;
 242             count = 0;
 243         }
 244         while (isalnum(sender[rpos + count]) && rpos + count < userlen)
 245             count++;
 246         while (!isalnum(sender[rpos + count]) && rpos + count < userlen)
 247             count++;
 248         wpos += m_strncpy(buf + wpos, len - wpos, sender + rpos, count);
 249         rpos += count;
 250     }
 251
 252     wpos += m_strputc(buf + wpos, len - wpos, '#');
 253     wpos += m_strcpy(buf + wpos, len - wpos, at + 1);
 254     return buf;
 255 }
 256
 257 static const char *c_net(const greylist_config_t *config,
 258                          const char *c_addr, const char *c_name,
 259                          char *cnet, int cnetlen)
 260 {
 261     char ip2[4], ip3[4];
 262     const char *dot, *p;
 263
 264     if (config->lookup_by_host)
 265         return c_addr;
 266
 267     if (!(dot = strchr(c_addr, '.')))
 268         return c_addr;
 269     if (!(dot = strchr(dot + 1, '.')))
 270         return c_addr;
 271
 272     p = ++dot;
 273     if (!(dot = strchr(dot, '.')) || dot - p > 3)
 274         return c_addr;
 275     m_strncpy(ip2, sizeof(ip2), p, dot - p);
 276
 277     p = ++dot;
 278     if (!(dot = strchr(dot, '.')) || dot - p > 3)
 279         return c_addr;
 280     m_strncpy(ip3, sizeof(ip3), p, dot - p);
 281
 282     /* skip if contains the last two ip numbers in the hostname,
 283        we assume it's a pool of dialup of a provider */
 284     if (strstr(c_name, ip2) && strstr(c_name, ip3))
 285         return c_addr;
 286
 287     m_strncpy(cnet, cnetlen, c_addr, dot - c_addr);
 288     return cnet;
 289 }
 290
 291
 292 static bool try_greylist(const greylist_config_t *config,
 293                          const char *sender, const char *c_addr,
 294                          const char *c_name, const char *rcpt)
 295 {
 296 #define INCR_AWL                                              \
 297     aent.count++;                                             \
 298     aent.last = now;                                          \
 299     debug("whitelist entry for %.*s updated, count %d",       \
 300           c_addrlen, c_addr, aent.count);                     \
 301     tcbdbput(config->awl_db, c_addr, c_addrlen, &aent,        \
 302              sizeof(aent));
 303
 304     char sbuf[BUFSIZ], cnet[64], key[BUFSIZ];
 305     const void *res;
 306
 307     time_t now = time(NULL);
 308     struct obj_entry oent = { now, now };
 309     struct awl_entry aent = { 0, 0 };
 310
 311     int len, klen, c_addrlen = strlen(c_addr);
 312
 313     /* Auto whitelist clients.
 314      */
 315     if (config->client_awl) {
 316         res = tcbdbget3(config->awl_db, c_addr, c_addrlen, &len);
 317         if (res && len == sizeof(aent)) {
 318             memcpy(&aent, res, len);
 319             debug("client %.*s has a whitelist entry, count is %d",
 320                   c_addrlen, c_addr, aent.count);
 321         }
 322
 323         if (!greylist_check_awlentry(config, &aent, now)) {
 324             aent.count = 0;
 325             aent.last  = 0;
 326             debug("client %.*s whitelist entry too old",
 327                   c_addrlen, c_addr);
 328         }
 329
 330         /* Whitelist if count is enough.
 331          */
 332         if (aent.count >= config->client_awl) {
 333             debug("client %.*s whitelisted", c_addrlen, c_addr);
 334             if (now < aent.last + 3600) {
 335                 INCR_AWL
 336             }
 337
 338             /* OK.
 339              */
 340             return true;
 341         }
 342     }
 343
 344     /* Lookup.
 345      */
 346     klen = snprintf(key, sizeof(key), "%s/%s/%s",
 347                     c_net(config, c_addr, c_name, cnet, sizeof(cnet)),
 348                     sender_normalize(sender, sbuf, sizeof(sbuf)), rcpt);
 349     klen = MIN(klen, ssizeof(key) - 1);
 350
 351     res = tcbdbget3(config->obj_db, key, klen, &len);
 352     if (res && len == sizeof(oent)) {
 353         memcpy(&oent, res, len);
 354         debug("found a greylist entry for %.*s", klen, key);
 355     }
 356
 357     /* Discard stored first-seen if it is the first retrial and
 358      * it is beyong the retry window and too old entries.
 359      */
 360     if (!greylist_check_object(config, &oent, now)) {
 361         oent.first = now;
 362         debug("invalid retry for %.*s: %s", klen, key,
 363               (config->max_age > 0 && now - oent.last > config->max_age) ?
 364                   "too old entry"
 365                 : (oent.last - oent.first < config->delay ?
 366                   "retry too early" : "retry too late" ));
 367     }
 368
 369     /* Update.
 370      */
 371     oent.last = now;
 372     tcbdbput(config->obj_db, key, klen, &oent, sizeof(oent));
 373
 374     /* Auto whitelist clients:
 375      *  algorithm:
 376      *    - on successful entry in the greylist db of a triplet:
 377      *        - client not whitelisted yet ? -> increase count
 378      *                                       -> withelist if count > limit
 379      *        - client whitelisted already ? -> update last-seen timestamp.
 380      */
 381     if (oent.first + config->delay < now) {
 382         debug("valid retry for %.*s", klen, key);
 383         if (config->client_awl) {
 384             INCR_AWL
 385         }
 386
 387         /* OK
 388          */
 389         return true;
 390     }
 391
 392     /* DUNNO
 393      */
 394     return false;
 395 }
 396
 397
 398 /* postlicyd filter declaration */
 399
 400 #include "filter.h"
 401
 402 static greylist_config_t *greylist_config_new(void)
 403 {
 404     const greylist_config_t g = GREYLIST_INIT;
 405     greylist_config_t *config = p_new(greylist_config_t, 1);
 406     *config = g;
 407     return config;
 408 }
 409
 410 static void greylist_config_delete(greylist_config_t **config)
 411 {
 412     if (*config) {
 413         greylist_shutdown(*config);
 414         p_delete(config);
 415     }
 416 }
 417
 418 static bool greylist_filter_constructor(filter_t *filter)
 419 {
 420     const char* path   = NULL;
 421     const char* prefix = NULL;
 422     greylist_config_t *config = greylist_config_new();
 423
 424 #define PARSE_CHECK(Expr, Str, ...)                                            \
 425     if (!(Expr)) {                                                             \
 426         err(Str, ##__VA_ARGS__);                                               \
 427         greylist_config_delete(&config);                                       \
 428         return false;                                                          \
 429     }
 430
 431     foreach (filter_param_t *param, filter->params) {
 432         switch (param->type) {
 433           FILTER_PARAM_PARSE_STRING(PATH,   path);
 434           FILTER_PARAM_PARSE_STRING(PREFIX, prefix);
 435           FILTER_PARAM_PARSE_BOOLEAN(LOOKUP_BY_HOST, config->lookup_by_host);
 436           FILTER_PARAM_PARSE_INT(RETRY_WINDOW, config->retry_window);
 437           FILTER_PARAM_PARSE_INT(CLIENT_AWL,   config->client_awl);
 438           FILTER_PARAM_PARSE_INT(DELAY,        config->delay);
 439           FILTER_PARAM_PARSE_INT(MAX_AGE,      config->max_age);
 440
 441           default: break;
 442         }
 443     }}
 444
 445     PARSE_CHECK(path, "path to greylist db not given");
 446     PARSE_CHECK(greylist_initialize(config, path, prefix ? prefix : ""),
 447                 "can not load greylist database");
 448
 449     filter->data = config;
 450     return true;
 451 }
 452
 453 static void greylist_filter_destructor(filter_t *filter)
 454 {
 455     greylist_config_t *data = filter->data;
 456     greylist_config_delete(&data);
 457     filter->data = data;
 458 }
 459
 460 static filter_result_t greylist_filter(const filter_t *filter,
 461                                        const query_t *query)
 462 {
 463     const greylist_config_t *config = filter->data;
 464     if (query->state != SMTP_RCPT) {
 465         warn("greylisting only works as smtpd_recipient_restrictions");
 466         return HTK_ABORT;
 467     }
 468
 469     return try_greylist(config, query->sender, query->client_address,
 470                         query->client_name, query->recipient) ?
 471            HTK_WHITELIST : HTK_GREYLIST;
 472 }
 473
 474 static int greylist_init(void)
 475 {
 476     filter_type_t type =  filter_register("greylist", greylist_filter_constructor,
 477                                           greylist_filter_destructor,
 478                                           greylist_filter);
 479     /* Hooks.
 480      */
 481     (void)filter_hook_register(type, "abort");
 482     (void)filter_hook_register(type, "error");
 483     (void)filter_hook_register(type, "greylist");
 484     (void)filter_hook_register(type, "whitelist");
 485
 486     /* Parameters.
 487      */
 488     (void)filter_param_register(type, "lookup_by_host");
 489     (void)filter_param_register(type, "delay");
 490     (void)filter_param_register(type, "retry_window");
 491     (void)filter_param_register(type, "client_awl");
 492     (void)filter_param_register(type, "max_age");
 493     (void)filter_param_register(type, "path");
 494     (void)filter_param_register(type, "prefix");
 495     return 0;
 496 }
 497 module_init(greylist_init)