postlicyd/greylist.c

   1 /******************************************************************************/
   2 /*          pfixtools: a collection of postfix related tools                  */
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  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
  48     TCBDB *awl_db;
  49     TCBDB *obj_db;
  50 } greylist_config_t;
  51
  52 #define GREYLIST_INIT { .lookup_by_host = false,       \
  53                         .delay = 300,                  \
  54                         .retry_window = 2 * 24 * 2600, \
  55                         .client_awl = 5,               \
  56                         .awl_db = NULL,                \
  57                         .obj_db = NULL }
  58
  59 struct awl_entry {
  60     int32_t count;
  61     time_t  last;
  62 };
  63
  64 struct obj_entry {
  65     time_t first;
  66     time_t last;
  67 };
  68
  69
  70 static bool greylist_initialize(greylist_config_t *config,
  71                                 const char *directory, const char *prefix)
  72 {
  73     char path[PATH_MAX];
  74
  75     if (config->client_awl) {
  76         snprintf(path, sizeof(path), "%s/%swhitelist.db", directory, prefix);
  77         config->awl_db = tcbdbnew();
  78         if (!tcbdbopen(config->awl_db, path, BDBOWRITER | BDBOCREAT)) {
  79             tcbdbdel(config->awl_db);
  80             config->awl_db = NULL;
  81         }
  82         return false;
  83     }
  84
  85     snprintf(path, sizeof(path), "%s/%sgreylist.db", directory, prefix);
  86     config->obj_db = tcbdbnew();
  87     if (!tcbdbopen(config->obj_db, path, BDBOWRITER | BDBOCREAT)) {
  88         tcbdbdel(config->obj_db);
  89         config->obj_db = NULL;
  90         if (config->awl_db) {
  91             tcbdbdel(config->awl_db);
  92             config->awl_db = NULL;
  93         }
  94         return false;
  95     }
  96
  97     return true;
  98 }
  99
 100 static void greylist_shutdown(greylist_config_t *config)
 101 {
 102     if (config->awl_db) {
 103         tcbdbsync(config->awl_db);
 104         tcbdbdel(config->awl_db);
 105         config->awl_db = NULL;
 106     }
 107     if (config->obj_db) {
 108         tcbdbsync(config->obj_db);
 109         tcbdbdel(config->obj_db);
 110         config->obj_db = NULL;
 111     }
 112 }
 113
 114 static const char *sender_normalize(const char *sender, char *buf, int len)
 115 {
 116     const char *at = strchr(sender, '@');
 117     int rpos = 0, wpos = 0, userlen;
 118
 119     if (!at)
 120         return sender;
 121
 122     /* strip extension used for VERP or alike */
 123     userlen = ((char *)memchr(sender, '+', at - sender) ?: at) - sender;
 124
 125     while (rpos < userlen) {
 126         int count = 0;
 127
 128         while (isdigit(sender[rpos + count]) && rpos + count < userlen)
 129             count++;
 130         if (count && !isalnum(sender[rpos + count])) {
 131             /* replace \<\d+\> with '#' */
 132             wpos += m_strputc(buf + wpos, len - wpos, '#');
 133             rpos += count;
 134             count = 0;
 135         }
 136         while (isalnum(sender[rpos + count]) && rpos + count < userlen)
 137             count++;
 138         while (!isalnum(sender[rpos + count]) && rpos + count < userlen)
 139             count++;
 140         wpos += m_strncpy(buf + wpos, len - wpos, sender + rpos, count);
 141         rpos += count;
 142     }
 143
 144     wpos += m_strputc(buf + wpos, len - wpos, '#');
 145     wpos += m_strcpy(buf + wpos, len - wpos, at + 1);
 146     return buf;
 147 }
 148
 149 static const char *c_net(const greylist_config_t *config,
 150                          const char *c_addr, const char *c_name,
 151                          char *cnet, int cnetlen)
 152 {
 153     char ip2[4], ip3[4];
 154     const char *dot, *p;
 155
 156     if (config->lookup_by_host)
 157         return c_addr;
 158
 159     if (!(dot = strchr(c_addr, '.')))
 160         return c_addr;
 161     if (!(dot = strchr(dot + 1, '.')))
 162         return c_addr;
 163
 164     p = ++dot;
 165     if (!(dot = strchr(dot, '.')) || dot - p > 3)
 166         return c_addr;
 167     m_strncpy(ip2, sizeof(ip2), p, dot - p);
 168
 169     p = ++dot;
 170     if (!(dot = strchr(dot, '.')) || dot - p > 3)
 171         return c_addr;
 172     m_strncpy(ip3, sizeof(ip3), p, dot - p);
 173
 174     /* skip if contains the last two ip numbers in the hostname,
 175        we assume it's a pool of dialup of a provider */
 176     if (strstr(c_name, ip2) && strstr(c_name, ip3))
 177         return c_addr;
 178
 179     m_strncpy(cnet, cnetlen, c_addr, dot - c_addr);
 180     return cnet;
 181 }
 182
 183 static bool try_greylist(const greylist_config_t *config,
 184                          const char *sender, const char *c_addr,
 185                          const char *c_name, const char *rcpt)
 186 {
 187 #define INCR_AWL                                              \
 188     aent.count++;                                             \
 189     aent.last = now;                                          \
 190     tcbdbput(config->awl_db, c_addr, c_addrlen, &aent,        \
 191              sizeof(aent));
 192
 193     char sbuf[BUFSIZ], cnet[64], key[BUFSIZ];
 194     const void *res;
 195
 196     time_t now = time(NULL);
 197     struct obj_entry oent = { now, now };
 198     struct awl_entry aent = { 0, 0 };
 199
 200     int len, klen, c_addrlen = strlen(c_addr);
 201
 202     /* Auto whitelist clients.
 203      */
 204     if (config->client_awl) {
 205         res = tcbdbget3(config->awl_db, c_addr, c_addrlen, &len);
 206         if (res && len == sizeof(aent)) {
 207             memcpy(&aent, res, len);
 208         }
 209
 210         /* Whitelist if count is enough.
 211          */
 212         if (aent.count > config->client_awl) {
 213             if (now < aent.last + 3600) {
 214                 INCR_AWL
 215             }
 216
 217             /* OK.
 218              */
 219             return true;
 220         }
 221     }
 222
 223     /* Lookup.
 224      */
 225     klen = snprintf(key, sizeof(key), "%s/%s/%s",
 226                     c_net(config, c_addr, c_name, cnet, sizeof(cnet)),
 227                     sender_normalize(sender, sbuf, sizeof(sbuf)), rcpt);
 228     klen = MIN(klen, ssizeof(key) - 1);
 229
 230     res = tcbdbget3(config->obj_db, key, klen, &len);
 231     if (res && len == sizeof(oent)) {
 232         memcpy(&oent, res, len);
 233     }
 234
 235     /* Discard stored first-seen if it is the first retrial and
 236      * it is beyong the retry window.
 237      */
 238     if (oent.last - oent.first < config->delay
 239         &&  now - oent.first > config->retry_window) {
 240         oent.first = now;
 241     }
 242
 243     /* Update.
 244      */
 245     oent.last = now;
 246     tcbdbput(config->obj_db, key, klen, &oent, sizeof(oent));
 247
 248     /* Auto whitelist clients:
 249      *  algorithm:
 250      *    - on successful entry in the greylist db of a triplet:
 251      *        - client not whitelisted yet ? -> increase count
 252      *                                       -> withelist if count > limit
 253      *        - client whitelisted already ? -> update last-seen timestamp.
 254      */
 255     if (oent.first + config->delay < now) {
 256         if (config->client_awl) {
 257             INCR_AWL
 258         }
 259
 260         /* OK
 261          */
 262         return true;
 263     }
 264
 265     /* DUNNO
 266      */
 267     return false;
 268 }
 269
 270
 271 /* postlicyd filter declaration */
 272
 273 #include "filter.h"
 274
 275 static greylist_config_t *greylist_config_new(void)
 276 {
 277     const greylist_config_t g = GREYLIST_INIT;
 278     greylist_config_t *config = p_new(greylist_config_t, 1);
 279     *config = g;
 280     return config;
 281 }
 282
 283 static void greylist_config_delete(greylist_config_t **config)
 284 {
 285     if (*config) {
 286         greylist_shutdown(*config);
 287         p_delete(config);
 288     }
 289 }
 290
 291 static bool greylist_filter_constructor(filter_t *filter)
 292 {
 293     const char* path   = NULL;
 294     const char* prefix = NULL;
 295     greylist_config_t *config = greylist_config_new();
 296
 297 #define PARSE_CHECK(Expr, Str, ...)                                            \
 298     if (!(Expr)) {                                                             \
 299         syslog(LOG_ERR, Str, ##__VA_ARGS__);                                   \
 300         greylist_config_delete(&config);                                       \
 301         return false;                                                          \
 302     }
 303
 304     foreach (filter_param_t *param, filter->params) {
 305         switch (param->type) {
 306           case ATK_PATH:
 307             path = param->value;
 308             break;
 309
 310           case ATK_PREFIX:
 311             prefix = param->value;
 312             break;
 313
 314           case ATK_LOOKUP_BY_HOST:
 315             config->lookup_by_host = (atoi(param->value) != 0);
 316             break;
 317
 318           case ATK_RETRY_WINDOW:
 319             config->retry_window = atoi(param->value);
 320             break;
 321
 322           case ATK_CLIENT_AWL:
 323             config->client_awl = atoi(param->value);
 324             break;
 325
 326           default: break;
 327         }
 328     }}
 329
 330     PARSE_CHECK(path, "path to greylist db not given");
 331     PARSE_CHECK(greylist_initialize(config, path, prefix ? prefix : ""),
 332                 "can not load greylist database");
 333
 334     filter->data = config;
 335     return true;
 336 }
 337
 338 static void greylist_filter_destructor(filter_t *filter)
 339 {
 340     greylist_config_t *data = filter->data;
 341     greylist_config_delete(&data);
 342     filter->data = data;
 343 }
 344
 345 static filter_result_t greylist_filter(const filter_t *filter,
 346                                        const query_t *query)
 347 {
 348     const greylist_config_t *config = filter->data;
 349     return try_greylist(config, query->sender, query->client_address,
 350                         query->client_name, query->recipient) ?
 351            HTK_MATCH : HTK_FAIL;
 352 }
 353
 354 static int greylist_init(void)
 355 {
 356     filter_type_t type =  filter_register("greylist", greylist_filter_constructor,
 357                                           greylist_filter_destructor,
 358                                           greylist_filter);
 359     /* Hooks.
 360      */
 361     (void)filter_hook_register(type, "error");
 362     (void)filter_hook_register(type, "fail");
 363     (void)filter_hook_register(type, "match");
 364
 365     /* Parameters.
 366      */
 367     (void)filter_param_register(type, "lookup_by_host");
 368     (void)filter_param_register(type, "delay");
 369     (void)filter_param_register(type, "retry_window");
 370     (void)filter_param_register(type, "client_awl");
 371     (void)filter_param_register(type, "path");
 372     (void)filter_param_register(type, "prefix");
 373     return 0;
 374 }
 375 module_init(greylist_init)