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 #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("no cleanup needed");
 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                     now = time(0);
 197                     tcbdbput(tmp_db, "@@cleanup@@", strlen("@@cleanup@@"), &now, sizeof(now));
 198                 }
 199                 tcxstrdel(key);
 200                 tcxstrdel(value);
 201                 tcbdbcurdel(cur);
 202                 tcbdbsync(tmp_db);
 203             } else {
 204                 warn("cannot run database cleanup: can't open destination database: %s",
 205                      tcbdberrmsg(tcbdbecode(awl_db)));
 206             }
 207             tcbdbdel(tmp_db);
 208         } else {
 209             int ecode = tcbdbecode(awl_db);
 210             warn("can not open database: %s", tcbdberrmsg(ecode));
 211             trashable = ecode != TCENOPERM && ecode != TCEOPEN && ecode != TCENOFILE && ecode != TCESUCCESS;
 212         }
 213         tcbdbdel(awl_db);
 214
 215         /** Cleanup successful, replace the old database with the new one.
 216          */
 217         if (trashable) {
 218             info("database cleanup finished: database was corrupted, create a new one");
 219             unlink(path);
 220         } else if (replace) {
 221             info("database cleanup finished: before %u entries, after %d entries",
 222                    old_count, new_count);
 223             unlink(path);
 224             if (rename(tmppath, path) != 0) {
 225                 UNIXERR("rename");
 226                 resource_release("greylist", path);
 227                 return NULL;
 228             }
 229         } else {
 230             unlink(tmppath);
 231             info("database cleanup finished: nothing to do, %u entries", new_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     res->db = awl_db;
 247     return &res->db;
 248 }
 249
 250
 251 static bool greylist_initialize(greylist_config_t *config,
 252                                 const char *directory, const char *prefix)
 253 {
 254     char path[PATH_MAX];
 255
 256     if (config->client_awl) {
 257         snprintf(path, sizeof(path), "%s/%swhitelist.db", directory, prefix);
 258         info("loading auto-whitelist database");
 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     info("loading greylist database");
 270     config->obj_db = greylist_db_get(config, path,
 271                                      sizeof(struct obj_entry),
 272                                      (db_entry_checker_t)(greylist_check_object));
 273     if (config->obj_db == NULL) {
 274         if (config->awlfilename) {
 275             resource_release("greylist", config->awlfilename);
 276             p_delete(&config->awlfilename);
 277         }
 278         return false;
 279     }
 280     config->objfilename = m_strdup(path);
 281
 282     return true;
 283 }
 284
 285 static void greylist_shutdown(greylist_config_t *config)
 286 {
 287     if (config->awlfilename) {
 288         resource_release("greylist", config->awlfilename);
 289         p_delete(&config->awlfilename);
 290     }
 291     if (config->objfilename) {
 292         resource_release("greylist", config->objfilename);
 293         p_delete(&config->objfilename);
 294     }
 295 }
 296
 297 static const char *sender_normalize(const char *sender, char *buf, int len)
 298 {
 299     const char *at = strchr(sender, '@');
 300     int rpos = 0, wpos = 0, userlen;
 301
 302     if (!at)
 303         return sender;
 304
 305     /* strip extension used for VERP or alike */
 306     userlen = ((char *)memchr(sender, '+', at - sender) ?: at) - sender;
 307
 308     while (rpos < userlen) {
 309         int count = 0;
 310
 311         while (isdigit(sender[rpos + count]) && rpos + count < userlen)
 312             count++;
 313         if (count && !isalnum(sender[rpos + count])) {
 314             /* replace \<\d+\> with '#' */
 315             wpos += m_strputc(buf + wpos, len - wpos, '#');
 316             rpos += count;
 317             count = 0;
 318         }
 319         while (isalnum(sender[rpos + count]) && rpos + count < userlen)
 320             count++;
 321         while (!isalnum(sender[rpos + count]) && rpos + count < userlen)
 322             count++;
 323         wpos += m_strncpy(buf + wpos, len - wpos, sender + rpos, count);
 324         rpos += count;
 325     }
 326
 327     wpos += m_strputc(buf + wpos, len - wpos, '#');
 328     wpos += m_strcpy(buf + wpos, len - wpos, at + 1);
 329     return buf;
 330 }
 331
 332 static const char *c_net(const greylist_config_t *config,
 333                          const char *c_addr, const char *c_name,
 334                          char *cnet, int cnetlen)
 335 {
 336     char ip2[4], ip3[4];
 337     const char *dot, *p;
 338
 339     if (config->lookup_by_host)
 340         return c_addr;
 341
 342     if (!(dot = strchr(c_addr, '.')))
 343         return c_addr;
 344     if (!(dot = strchr(dot + 1, '.')))
 345         return c_addr;
 346
 347     p = ++dot;
 348     if (!(dot = strchr(dot, '.')) || dot - p > 3)
 349         return c_addr;
 350     m_strncpy(ip2, sizeof(ip2), p, dot - p);
 351
 352     p = ++dot;
 353     if (!(dot = strchr(dot, '.')) || dot - p > 3)
 354         return c_addr;
 355     m_strncpy(ip3, sizeof(ip3), p, dot - p);
 356
 357     /* skip if contains the last two ip numbers in the hostname,
 358        we assume it's a pool of dialup of a provider */
 359     if (strstr(c_name, ip2) && strstr(c_name, ip3))
 360         return c_addr;
 361
 362     m_strncpy(cnet, cnetlen, c_addr, dot - c_addr);
 363     return cnet;
 364 }
 365
 366
 367 static bool try_greylist(const greylist_config_t *config,
 368                          const char *sender, const char *c_addr,
 369                          const char *c_name, const char *rcpt)
 370 {
 371 #define INCR_AWL                                              \
 372     aent.count++;                                             \
 373     aent.last = now;                                          \
 374     debug("whitelist entry for %.*s updated, count %d",       \
 375           c_addrlen, c_addr, aent.count);                     \
 376     tcbdbput(awl_db, c_addr, c_addrlen, &aent, sizeof(aent));
 377
 378     char sbuf[BUFSIZ], cnet[64], key[BUFSIZ];
 379     const void *res;
 380
 381     time_t now = time(NULL);
 382     struct obj_entry oent = { now, now };
 383     struct awl_entry aent = { 0, 0 };
 384
 385     int len, klen, c_addrlen = strlen(c_addr);
 386     TCBDB * const awl_db = config->awl_db ? *(config->awl_db) : NULL;
 387     TCBDB * const obj_db = config->obj_db ? *(config->obj_db) : NULL;
 388
 389     /* Auto whitelist clients.
 390      */
 391     if (config->client_awl) {
 392         res = tcbdbget3(awl_db, c_addr, c_addrlen, &len);
 393         if (res && len == sizeof(aent)) {
 394             memcpy(&aent, res, len);
 395             debug("client %.*s has a whitelist entry, count is %d",
 396                   c_addrlen, c_addr, aent.count);
 397         }
 398
 399         if (!greylist_check_awlentry(config, &aent, now)) {
 400             aent.count = 0;
 401             aent.last  = 0;
 402             debug("client %.*s whitelist entry too old",
 403                   c_addrlen, c_addr);
 404         }
 405
 406         /* Whitelist if count is enough.
 407          */
 408         if (aent.count >= config->client_awl) {
 409             debug("client %.*s whitelisted", c_addrlen, c_addr);
 410             if (now < aent.last + 3600) {
 411                 INCR_AWL
 412             }
 413
 414             /* OK.
 415              */
 416             return true;
 417         }
 418     }
 419
 420     /* Lookup.
 421      */
 422     klen = snprintf(key, sizeof(key), "%s/%s/%s",
 423                     c_net(config, c_addr, c_name, cnet, sizeof(cnet)),
 424                     config->no_sender ? "" : sender_normalize(sender, sbuf, sizeof(sbuf)),
 425                     config->no_recipient ? "" : rcpt);
 426     klen = MIN(klen, ssizeof(key) - 1);
 427
 428     res = tcbdbget3(obj_db, key, klen, &len);
 429     if (res && len == sizeof(oent)) {
 430         memcpy(&oent, res, len);
 431         debug("found a greylist entry for %.*s", klen, key);
 432     }
 433
 434     /* Discard stored first-seen if it is the first retrial and
 435      * it is beyong the retry window and too old entries.
 436      */
 437     if (!greylist_check_object(config, &oent, now)) {
 438         oent.first = now;
 439         debug("invalid retry for %.*s: %s", klen, key,
 440               (config->max_age > 0 && now - oent.last > config->max_age) ?
 441                   "too old entry"
 442                 : (oent.last - oent.first < config->delay ?
 443                   "retry too early" : "retry too late" ));
 444     }
 445
 446     /* Update.
 447      */
 448     oent.last = now;
 449     tcbdbput(obj_db, key, klen, &oent, sizeof(oent));
 450
 451     /* Auto whitelist clients:
 452      *  algorithm:
 453      *    - on successful entry in the greylist db of a triplet:
 454      *        - client not whitelisted yet ? -> increase count
 455      *                                       -> withelist if count > limit
 456      *        - client whitelisted already ? -> update last-seen timestamp.
 457      */
 458     if (oent.first + config->delay < now) {
 459         debug("valid retry for %.*s", klen, key);
 460         if (config->client_awl) {
 461             INCR_AWL
 462         }
 463
 464         /* OK
 465          */
 466         return true;
 467     }
 468
 469     /* DUNNO
 470      */
 471     return false;
 472 }
 473
 474
 475 /* postlicyd filter declaration */
 476
 477 #include "filter.h"
 478
 479 static greylist_config_t *greylist_config_new(void)
 480 {
 481     const greylist_config_t g = GREYLIST_INIT;
 482     greylist_config_t *config = p_new(greylist_config_t, 1);
 483     *config = g;
 484     return config;
 485 }
 486
 487 static void greylist_config_delete(greylist_config_t **config)
 488 {
 489     if (*config) {
 490         greylist_shutdown(*config);
 491         p_delete(config);
 492     }
 493 }
 494
 495 static bool greylist_filter_constructor(filter_t *filter)
 496 {
 497     const char* path   = NULL;
 498     const char* prefix = NULL;
 499     greylist_config_t *config = greylist_config_new();
 500
 501 #define PARSE_CHECK(Expr, Str, ...)                                            \
 502     if (!(Expr)) {                                                             \
 503         err(Str, ##__VA_ARGS__);                                               \
 504         greylist_config_delete(&config);                                       \
 505         return false;                                                          \
 506     }
 507
 508     foreach (filter_param_t *param, filter->params) {
 509         switch (param->type) {
 510           FILTER_PARAM_PARSE_STRING(PATH,   path);
 511           FILTER_PARAM_PARSE_STRING(PREFIX, prefix);
 512           FILTER_PARAM_PARSE_BOOLEAN(LOOKUP_BY_HOST, config->lookup_by_host);
 513           FILTER_PARAM_PARSE_BOOLEAN(NO_SENDER, config->no_sender);
 514           FILTER_PARAM_PARSE_BOOLEAN(NO_RECIPIENT, config->no_recipient);
 515           FILTER_PARAM_PARSE_INT(RETRY_WINDOW, config->retry_window);
 516           FILTER_PARAM_PARSE_INT(CLIENT_AWL,   config->client_awl);
 517           FILTER_PARAM_PARSE_INT(DELAY,        config->delay);
 518           FILTER_PARAM_PARSE_INT(MAX_AGE,      config->max_age);
 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, "path");
 580     (void)filter_param_register(type, "prefix");
 581     return 0;
 582 }
 583 module_init(greylist_init)