postlicyd/greylist.c

   1 /******************************************************************************/
   2 /*          pfixtools: a collection of postfix related tools                  */
   3 /*          ~~~~~~~~~                                                         */
   4 /*  ________________________________________________________________________  */
   5 /*                                                                            */
   6 /*  Redistribution and use in source and binary forms, with or without        */
   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 #include "resources.h"
  41
  42
  43 typedef struct greylist_config_t {
  44     unsigned lookup_by_host : 1;
  45     unsigned no_sender      : 1;
  46     unsigned no_recipient   : 1;
  47     int delay;
  48     int retry_window;
  49     int client_awl;
  50     int max_age;
  51     int cleanup_period;
  52
  53     char  *awlfilename;
  54     TCBDB **awl_db;
  55     char  *objfilename;
  56     TCBDB **obj_db;
  57 } greylist_config_t;
  58
  59 #define GREYLIST_INIT { .lookup_by_host = false,       \
  60                         .no_sender = false,            \
  61                         .no_recipient = false,         \
  62                         .delay = 300,                  \
  63                         .retry_window = 2 * 24 * 3600, \
  64                         .client_awl = 5,               \
  65                         .max_age = 35 * 3600,          \
  66                         .cleanup_period = 86400,       \
  67                         .awlfilename = NULL,           \
  68                         .awl_db = NULL,                \
  69                         .objfilename = NULL,           \
  70                         .obj_db = NULL }
  71
  72 struct awl_entry {
  73     int32_t count;
  74     time_t  last;
  75 };
  76
  77 struct obj_entry {
  78     time_t first;
  79     time_t last;
  80 };
  81
  82 typedef struct greylist_resource_t {
  83     TCBDB *db;
  84 } greylist_resource_t;
  85
  86
  87 static void greylist_resource_wipe(greylist_resource_t *res)
  88 {
  89     if (res->db) {
  90         tcbdbsync(res->db);
  91         tcbdbdel(res->db);
  92     }
  93     p_delete(&res);
  94 }
  95
  96 static inline bool greylist_check_awlentry(const greylist_config_t *config,
  97                                            struct awl_entry *aent, time_t now)
  98 {
  99     return !(config->max_age > 0 && now - aent->last > config->max_age);
 100 }
 101
 102 static inline bool greylist_check_object(const greylist_config_t *config,
 103                                          const struct obj_entry *oent, time_t now)
 104 {
 105     return !((config->max_age > 0 && now - oent->last > config->max_age)
 106              || (oent->last - oent->first < config->delay
 107                  && now - oent->last > config->retry_window));
 108 }
 109
 110 typedef bool (*db_entry_checker_t)(const greylist_config_t *, const void *, time_t);
 111
 112 static inline bool greylist_db_need_cleanup(const greylist_config_t *config, TCBDB *db)
 113 {
 114     int len = 0;
 115     time_t now = time(NULL);
 116     const time_t *last_cleanup = tcbdbget3(db, "@@cleanup@@", strlen("@@cleanup@@"), &len);
 117     if (last_cleanup == NULL) {
 118         debug("No last cleanup time");
 119     } else {
 120         debug("Last cleanup time %u, (ie %us ago)",
 121               (uint32_t)*last_cleanup, (uint32_t)(now - *last_cleanup));
 122     }
 123     return last_cleanup == NULL
 124         || len != sizeof(*last_cleanup)
 125         || (now - *last_cleanup) >= config->cleanup_period;
 126 }
 127
 128 static TCBDB **greylist_db_get(const greylist_config_t *config, const char *path,
 129                               size_t entry_len, db_entry_checker_t check)
 130 {
 131     TCBDB *awl_db, *tmp_db;
 132     time_t now = time(NULL);
 133
 134     greylist_resource_t *res = resource_get("greylist", path);
 135     if (res == NULL) {
 136         res = p_new(greylist_resource_t, 1);
 137         resource_set("greylist", path, res, (resource_destructor_t)greylist_resource_wipe);
 138     }
 139
 140     /* Open the database and check if cleanup is needed
 141      */
 142     awl_db = res->db;
 143     res->db = NULL;
 144     if (awl_db == NULL) {
 145         awl_db = tcbdbnew();
 146         if (!tcbdbopen(awl_db, path, BDBOWRITER | BDBOCREAT)) {
 147             err("can not open database: %s", tcbdberrmsg(tcbdbecode(awl_db)));
 148             tcbdbdel(awl_db);
 149             resource_release("greylist", path);
 150             return NULL;
 151         }
 152     }
 153     if (!greylist_db_need_cleanup(config, awl_db) || config->max_age <= 0) {
 154         info("%s loaded: no cleanup needed", path);
 155         res->db = awl_db;
 156         return &res->db;
 157     } else {
 158         tcbdbsync(awl_db);
 159         tcbdbdel(awl_db);
 160     }
 161
 162     /* Rebuild a new database after removing too old entries.
 163      */
 164     if (config->max_age > 0) {
 165         uint32_t old_count = 0;
 166         uint32_t new_count = 0;
 167         bool replace = false;
 168         bool trashable = false;
 169         char tmppath[PATH_MAX];
 170         snprintf(tmppath, PATH_MAX, "%s.tmp", path);
 171
 172         awl_db = tcbdbnew();
 173         if (tcbdbopen(awl_db, path, BDBOREADER)) {
 174             tmp_db = tcbdbnew();
 175             if (tcbdbopen(tmp_db, tmppath, BDBOWRITER | BDBOCREAT | BDBOTRUNC)) {
 176                 BDBCUR *cur = tcbdbcurnew(awl_db);
 177                 TCXSTR *key, *value;
 178
 179                 key = tcxstrnew();
 180                 value = tcxstrnew();
 181                 if (tcbdbcurfirst(cur)) {
 182                     replace = true;
 183                     do {
 184                         tcxstrclear(key);
 185                         tcxstrclear(value);
 186                         (void)tcbdbcurrec(cur, key, value);
 187
 188                         if ((size_t)tcxstrsize(value) == entry_len
 189                             && check(config, tcxstrptr(value), now)) {
 190                             tcbdbput(tmp_db, tcxstrptr(key), tcxstrsize(key),
 191                                      tcxstrptr(value), entry_len);
 192                             ++new_count;
 193                         }
 194                         ++old_count;
 195                     } while (tcbdbcurnext(cur));
 196                     tcbdbput(tmp_db, "@@cleanup@@", strlen("@@cleanup@@"), &now, sizeof(now));
 197                 }
 198                 tcxstrdel(key);
 199                 tcxstrdel(value);
 200                 tcbdbcurdel(cur);
 201                 tcbdbsync(tmp_db);
 202             } else {
 203                 warn("cannot run database cleanup: can't open destination database: %s",
 204                      tcbdberrmsg(tcbdbecode(awl_db)));
 205             }
 206             tcbdbdel(tmp_db);
 207         } else {
 208             int ecode = tcbdbecode(awl_db);
 209             warn("can not open database: %s", tcbdberrmsg(ecode));
 210             trashable = ecode != TCENOPERM && ecode != TCEOPEN && ecode != TCENOFILE && ecode != TCESUCCESS;
 211         }
 212         tcbdbdel(awl_db);
 213
 214         /** Cleanup successful, replace the old database with the new one.
 215          */
 216         if (trashable) {
 217             info("%s cleanup: database was corrupted, create a new one", path);
 218             unlink(path);
 219         } else if (replace) {
 220             info("%s cleanup: done in %us, before %u, after %u entries",
 221                  path, (uint32_t)(time(0) - now), old_count, new_count);
 222             unlink(path);
 223             if (rename(tmppath, path) != 0) {
 224                 UNIXERR("rename");
 225                 resource_release("greylist", path);
 226                 return NULL;
 227             }
 228         } else {
 229             unlink(tmppath);
 230             info("%s cleanup: done in %us, nothing to do, %u entries",
 231                  path, (uint32_t)(time(0) - now), old_count);
 232         }
 233     }
 234
 235     /* Effectively open the database.
 236      */
 237     res->db = NULL;
 238     awl_db = tcbdbnew();
 239     if (!tcbdbopen(awl_db, path, BDBOWRITER | BDBOCREAT)) {
 240         err("can not open database: %s", tcbdberrmsg(tcbdbecode(awl_db)));
 241         tcbdbdel(awl_db);
 242         resource_release("greylist", path);
 243         return NULL;
 244     }
 245
 246     info("%s loaded", path);
 247     res->db = awl_db;
 248     return &res->db;
 249 }
 250
 251
 252 static bool greylist_initialize(greylist_config_t *config,
 253                                 const char *directory, const char *prefix)
 254 {
 255     char path[PATH_MAX];
 256
 257     if (config->client_awl) {
 258         snprintf(path, sizeof(path), "%s/%swhitelist.db", directory, prefix);
 259         config->awl_db = greylist_db_get(config, path,
 260                                          sizeof(struct awl_entry),
 261                                          (db_entry_checker_t)(greylist_check_awlentry));
 262         if (config->awl_db == NULL) {
 263             return false;
 264         }
 265         config->awlfilename = m_strdup(path);
 266     }
 267
 268     snprintf(path, sizeof(path), "%s/%sgreylist.db", directory, prefix);
 269     config->obj_db = greylist_db_get(config, path,
 270                                      sizeof(struct obj_entry),
 271                                      (db_entry_checker_t)(greylist_check_object));
 272     if (config->obj_db == NULL) {
 273         if (config->awlfilename) {
 274             resource_release("greylist", config->awlfilename);
 275             p_delete(&config->awlfilename);
 276         }
 277         return false;
 278     }
 279     config->objfilename = m_strdup(path);
 280
 281     return true;
 282 }
 283
 284 static void greylist_shutdown(greylist_config_t *config)
 285 {
 286     if (config->awlfilename) {
 287         resource_release("greylist", config->awlfilename);
 288         p_delete(&config->awlfilename);
 289     }
 290     if (config->objfilename) {
 291         resource_release("greylist", config->objfilename);
 292         p_delete(&config->objfilename);
 293     }
 294 }
 295
 296 static const char *sender_normalize(const char *sender, char *buf, int len)
 297 {
 298     const char *at = strchr(sender, '@');
 299     int rpos = 0, wpos = 0, userlen;
 300
 301     if (!at)
 302         return sender;
 303
 304     /* strip extension used for VERP or alike */
 305     userlen = ((char *)memchr(sender, '+', at - sender) ?: at) - sender;
 306
 307     while (rpos < userlen) {
 308         int count = 0;
 309
 310         while (isdigit(sender[rpos + count]) && rpos + count < userlen)
 311             count++;
 312         if (count && !isalnum(sender[rpos + count])) {
 313             /* replace \<\d+\> with '#' */
 314             wpos += m_strputc(buf + wpos, len - wpos, '#');
 315             rpos += count;
 316             count = 0;
 317         }
 318         while (isalnum(sender[rpos + count]) && rpos + count < userlen)
 319             count++;
 320         while (!isalnum(sender[rpos + count]) && rpos + count < userlen)
 321             count++;
 322         wpos += m_strncpy(buf + wpos, len - wpos, sender + rpos, count);
 323         rpos += count;
 324     }
 325
 326     wpos += m_strputc(buf + wpos, len - wpos, '#');
 327     wpos += m_strcpy(buf + wpos, len - wpos, at + 1);
 328     return buf;
 329 }
 330
 331 static const char *c_net(const greylist_config_t *config,
 332                          const char *c_addr, const char *c_name,
 333                          char *cnet, int cnetlen)
 334 {
 335     char ip2[4], ip3[4];
 336     const char *dot, *p;
 337
 338     if (config->lookup_by_host)
 339         return c_addr;
 340
 341     if (!(dot = strchr(c_addr, '.')))
 342         return c_addr;
 343     if (!(dot = strchr(dot + 1, '.')))
 344         return c_addr;
 345
 346     p = ++dot;
 347     if (!(dot = strchr(dot, '.')) || dot - p > 3)
 348         return c_addr;
 349     m_strncpy(ip2, sizeof(ip2), p, dot - p);
 350
 351     p = ++dot;
 352     if (!(dot = strchr(dot, '.')) || dot - p > 3)
 353         return c_addr;
 354     m_strncpy(ip3, sizeof(ip3), p, dot - p);
 355
 356     /* skip if contains the last two ip numbers in the hostname,
 357        we assume it's a pool of dialup of a provider */
 358     if (strstr(c_name, ip2) && strstr(c_name, ip3))
 359         return c_addr;
 360
 361     m_strncpy(cnet, cnetlen, c_addr, dot - c_addr);
 362     return cnet;
 363 }
 364
 365
 366 static bool try_greylist(const greylist_config_t *config,
 367                          const char *sender, const char *c_addr,
 368                          const char *c_name, const char *rcpt)
 369 {
 370 #define INCR_AWL                                              \
 371     aent.count++;                                             \
 372     aent.last = now;                                          \
 373     debug("whitelist entry for %.*s updated, count %d",       \
 374           c_addrlen, c_addr, aent.count);                     \
 375     tcbdbput(awl_db, c_addr, c_addrlen, &aent, sizeof(aent));
 376
 377     char sbuf[BUFSIZ], cnet[64], key[BUFSIZ];
 378     const void *res;
 379
 380     time_t now = time(NULL);
 381     struct obj_entry oent = { now, now };
 382     struct awl_entry aent = { 0, 0 };
 383
 384     int len, klen, c_addrlen = strlen(c_addr);
 385     TCBDB * const awl_db = config->awl_db ? *(config->awl_db) : NULL;
 386     TCBDB * const obj_db = config->obj_db ? *(config->obj_db) : NULL;
 387
 388     /* Auto whitelist clients.
 389      */
 390     if (config->client_awl) {
 391         res = tcbdbget3(awl_db, c_addr, c_addrlen, &len);
 392         if (res && len == sizeof(aent)) {
 393             memcpy(&aent, res, len);
 394             debug("client %.*s has a whitelist entry, count is %d",
 395                   c_addrlen, c_addr, aent.count);
 396         }
 397
 398         if (!greylist_check_awlentry(config, &aent, now)) {
 399             aent.count = 0;
 400             aent.last  = 0;
 401             debug("client %.*s whitelist entry too old",
 402                   c_addrlen, c_addr);
 403         }
 404
 405         /* Whitelist if count is enough.
 406          */
 407         if (aent.count >= config->client_awl) {
 408             debug("client %.*s whitelisted", c_addrlen, c_addr);
 409             if (now < aent.last + 3600) {
 410                 INCR_AWL
 411             }
 412
 413             /* OK.
 414              */
 415             return true;
 416         }
 417     }
 418
 419     /* Lookup.
 420      */
 421     klen = snprintf(key, sizeof(key), "%s/%s/%s",
 422                     c_net(config, c_addr, c_name, cnet, sizeof(cnet)),
 423                     config->no_sender ? "" : sender_normalize(sender, sbuf, sizeof(sbuf)),
 424                     config->no_recipient ? "" : rcpt);
 425     klen = MIN(klen, ssizeof(key) - 1);
 426
 427     res = tcbdbget3(obj_db, key, klen, &len);
 428     if (res && len == sizeof(oent)) {
 429         memcpy(&oent, res, len);
 430         debug("found a greylist entry for %.*s", klen, key);
 431     }
 432
 433     /* Discard stored first-seen if it is the first retrial and
 434      * it is beyong the retry window and too old entries.
 435      */
 436     if (!greylist_check_object(config, &oent, now)) {
 437         oent.first = now;
 438         debug("invalid retry for %.*s: %s", klen, key,
 439               (config->max_age > 0 && now - oent.last > config->max_age) ?
 440                   "too old entry"
 441                 : (oent.last - oent.first < config->delay ?
 442                   "retry too early" : "retry too late" ));
 443     }
 444
 445     /* Update.
 446      */
 447     oent.last = now;
 448     tcbdbput(obj_db, key, klen, &oent, sizeof(oent));
 449
 450     /* Auto whitelist clients:
 451      *  algorithm:
 452      *    - on successful entry in the greylist db of a triplet:
 453      *        - client not whitelisted yet ? -> increase count
 454      *                                       -> withelist if count > limit
 455      *        - client whitelisted already ? -> update last-seen timestamp.
 456      */
 457     if (oent.first + config->delay < now) {
 458         debug("valid retry for %.*s", klen, key);
 459         if (config->client_awl) {
 460             INCR_AWL
 461         }
 462
 463         /* OK
 464          */
 465         return true;
 466     }
 467
 468     /* DUNNO
 469      */
 470     return false;
 471 }
 472
 473
 474 /* postlicyd filter declaration */
 475
 476 #include "filter.h"
 477
 478 static greylist_config_t *greylist_config_new(void)
 479 {
 480     const greylist_config_t g = GREYLIST_INIT;
 481     greylist_config_t *config = p_new(greylist_config_t, 1);
 482     *config = g;
 483     return config;
 484 }
 485
 486 static void greylist_config_delete(greylist_config_t **config)
 487 {
 488     if (*config) {
 489         greylist_shutdown(*config);
 490         p_delete(config);
 491     }
 492 }
 493
 494 static bool greylist_filter_constructor(filter_t *filter)
 495 {
 496     const char* path   = NULL;
 497     const char* prefix = NULL;
 498     greylist_config_t *config = greylist_config_new();
 499
 500 #define PARSE_CHECK(Expr, Str, ...)                                            \
 501     if (!(Expr)) {                                                             \
 502         err(Str, ##__VA_ARGS__);                                               \
 503         greylist_config_delete(&config);                                       \
 504         return false;                                                          \
 505     }
 506
 507     foreach (filter_param_t *param, filter->params) {
 508         switch (param->type) {
 509           FILTER_PARAM_PARSE_STRING(PATH,   path);
 510           FILTER_PARAM_PARSE_STRING(PREFIX, prefix);
 511           FILTER_PARAM_PARSE_BOOLEAN(LOOKUP_BY_HOST, config->lookup_by_host);
 512           FILTER_PARAM_PARSE_BOOLEAN(NO_SENDER, config->no_sender);
 513           FILTER_PARAM_PARSE_BOOLEAN(NO_RECIPIENT, config->no_recipient);
 514           FILTER_PARAM_PARSE_INT(RETRY_WINDOW, config->retry_window);
 515           FILTER_PARAM_PARSE_INT(CLIENT_AWL,   config->client_awl);
 516           FILTER_PARAM_PARSE_INT(DELAY,        config->delay);
 517           FILTER_PARAM_PARSE_INT(MAX_AGE,      config->max_age);
 518           FILTER_PARAM_PARSE_INT(CLEANUP_PERIOD, config->cleanup_period);
 519
 520           default: break;
 521         }
 522     }}
 523
 524     PARSE_CHECK(path, "path to greylist db not given");
 525     PARSE_CHECK(greylist_initialize(config, path, prefix ? prefix : ""),
 526                 "can not load greylist database");
 527
 528     filter->data = config;
 529     return true;
 530 }
 531
 532 static void greylist_filter_destructor(filter_t *filter)
 533 {
 534     greylist_config_t *data = filter->data;
 535     greylist_config_delete(&data);
 536     filter->data = data;
 537 }
 538
 539 static filter_result_t greylist_filter(const filter_t *filter,
 540                                        const query_t *query,
 541                                        filter_context_t *context)
 542 {
 543     const greylist_config_t *config = filter->data;
 544     if (!config->no_recipient && query->state != SMTP_RCPT) {
 545         warn("greylisting on recipient only works as smtpd_recipient_restrictions");
 546         return HTK_ABORT;
 547     }
 548     if (!config->no_sender && query->state < SMTP_MAIL) {
 549         warn("greylisting on sender must be performed after (or at) MAIL TO");
 550         return HTK_ABORT;
 551     }
 552
 553     return try_greylist(config, query->sender, query->client_address,
 554                         query->client_name, query->recipient) ?
 555            HTK_WHITELIST : HTK_GREYLIST;
 556 }
 557
 558 static int greylist_init(void)
 559 {
 560     filter_type_t type =  filter_register("greylist", greylist_filter_constructor,
 561                                           greylist_filter_destructor,
 562                                           greylist_filter, NULL, NULL);
 563     /* Hooks.
 564      */
 565     (void)filter_hook_register(type, "abort");
 566     (void)filter_hook_register(type, "error");
 567     (void)filter_hook_register(type, "greylist");
 568     (void)filter_hook_register(type, "whitelist");
 569
 570     /* Parameters.
 571      */
 572     (void)filter_param_register(type, "lookup_by_host");
 573     (void)filter_param_register(type, "no_sender");
 574     (void)filter_param_register(type, "no_recipient");
 575     (void)filter_param_register(type, "delay");
 576     (void)filter_param_register(type, "retry_window");
 577     (void)filter_param_register(type, "client_awl");
 578     (void)filter_param_register(type, "max_age");
 579     (void)filter_param_register(type, "cleanup_period");
 580     (void)filter_param_register(type, "path");
 581     (void)filter_param_register(type, "prefix");
 582     return 0;
 583 }
 584 module_init(greylist_init)