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