src/src/lookups/cdb.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /*
   6  * Exim - CDB database lookup module
   7  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   8  *
   9  * Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * --------------------------------------------------------------
  17  * Modified by PH for Exim 4:
  18  *   Changed over to using unsigned chars
  19  *   Makes use of lf_check_file() for file checking
  20  * --------------------------------------------------------------
  21  * Modified by The Exim Maintainers 2015:
  22  *   const propagation
  23  * --------------------------------------------------------------
  24  *
  25  * This program is distributed in the hope that it will be useful,
  26  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  27  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  28  * GNU General Public License for more details.
  29  *
  30  * You should have received a copy of the GNU General Public License
  31  * along with this program; if not, write to the Free Software
  32  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  33  * 02111-1307, USA.
  34  *
  35  *
  36  * This code implements Dan Bernstein's Constant DataBase (cdb) spec.
  37  * Information, the spec and sample code for cdb can be obtained from
  38  *      http://www.pobox.com/~djb/cdb.html
  39  *
  40  * This implementation borrows some code from Dan Bernstein's
  41  * implementation (which has no license restrictions applied to it).
  42  * This (read-only) implementation is completely contained within
  43  * cdb.[ch] it does *not* link against an external cdb library.
  44  *
  45  *
  46  * There are 2 varients included within this code.  One uses MMAP and
  47  * should give better performance especially for multiple lookups on a
  48  * modern machine.  The other is the default implementation which is
  49  * used in the case where the MMAP fails or if MMAP was not compiled
  50  * in.  this implementation is the same as the original reference cdb
  51  * implementation.  The MMAP version is compiled in if the HAVE_MMAP
  52  * preprocessor define is defined - this should be set in the system
  53  * specific os.h file.
  54  *
  55  */
  56
  57
  58 #include "../exim.h"
  59 #include "lf_functions.h"
  60
  61 #ifdef HAVE_MMAP
  62 #  include <sys/mman.h>
  63 /* Not all implementations declare MAP_FAILED */
  64 #  ifndef MAP_FAILED
  65 #    define MAP_FAILED ((void *) -1)
  66 #  endif /* MAP_FAILED */
  67 #endif /* HAVE_MMAP */
  68
  69
  70 #define CDB_HASH_SPLIT 256     /* num pieces the hash table is split into */
  71 #define CDB_HASH_MASK  255     /* mask to and off split value */
  72 #define CDB_HASH_ENTRY 8       /* how big each offset it */
  73 #define CDB_HASH_TABLE (CDB_HASH_SPLIT * CDB_HASH_ENTRY)
  74
  75 /* State information for cdb databases that are open NB while the db
  76  * is open its contents will not change (cdb dbs are normally updated
  77  * atomically by renaming).  However the lifetime of one of these
  78  * state structures should be limited - ie a long running daemon
  79  * that opens one may hit problems....
  80  */
  81
  82 struct cdb_state {
  83   int     fileno;
  84   off_t   filelen;
  85   uschar *cdb_map;
  86   uschar *cdb_offsets;
  87 };
  88
  89 /* 32 bit unsigned type - this is an int on all modern machines */
  90 typedef unsigned int uint32;
  91
  92 /*
  93  * cdb_hash()
  94  * Internal function to make hash value */
  95
  96 static uint32
  97 cdb_hash(uschar *buf, unsigned int len)
  98 {
  99   uint32 h;
 100
 101   h = 5381;
 102   while (len) {
 103     --len;
 104     h += (h << 5);
 105     h ^= (uint32) *buf++;
 106   }
 107   return h;
 108 }
 109
 110 /*
 111  * cdb_bread()
 112  * Internal function to read len bytes from disk, coping with oddities */
 113
 114 static int
 115 cdb_bread(int fd,
 116          uschar *buf,
 117          int len)
 118 {
 119   int r;
 120   while (len > 0) {
 121     do
 122       r = Uread(fd,buf,len);
 123     while ((r == -1) && (errno == EINTR));
 124     if (r == -1) return -1;
 125     if (r == 0) { errno = EIO; return -1; }
 126     buf += r;
 127     len -= r;
 128   }
 129   return 0;
 130 }
 131
 132 /*
 133  * cdb_bread()
 134  * Internal function to parse 4 byte number (endian independant) */
 135
 136 static uint32
 137 cdb_unpack(uschar *buf)
 138 {
 139   uint32 num;
 140   num =  buf[3]; num <<= 8;
 141   num += buf[2]; num <<= 8;
 142   num += buf[1]; num <<= 8;
 143   num += buf[0];
 144   return num;
 145 }
 146
 147 static void cdb_close(void *handle);
 148
 149 static void *
 150 cdb_open(uschar *filename,
 151          uschar **errmsg)
 152 {
 153   int fileno;
 154   struct cdb_state *cdbp;
 155   struct stat statbuf;
 156   void * mapbuf;
 157
 158   fileno = Uopen(filename, O_RDONLY, 0);
 159   if (fileno == -1) {
 160     int save_errno = errno;
 161     *errmsg = string_open_failed(errno, "%s for cdb lookup", filename);
 162     errno = save_errno;
 163     return NULL;
 164   }
 165
 166   if (fstat(fileno, &statbuf) == 0) {
 167     /* If this is a valid file, then it *must* be at least
 168      * CDB_HASH_TABLE bytes long */
 169     if (statbuf.st_size < CDB_HASH_TABLE) {
 170       int save_errno = errno;
 171       *errmsg = string_open_failed(errno,
 172                                   "%s too short for cdb lookup",
 173                                   filename);
 174       errno = save_errno;
 175       return NULL;
 176     }
 177   } else {
 178     int save_errno = errno;
 179     *errmsg = string_open_failed(errno,
 180                                 "fstat(%s) failed - cannot do cdb lookup",
 181                                 filename);
 182     errno = save_errno;
 183     return NULL;
 184   }
 185
 186   /* Having got a file open we need the structure to put things in */
 187   cdbp = store_get(sizeof(struct cdb_state));
 188   /* store_get() does not return if memory was not available... */
 189   /* preload the structure.... */
 190   cdbp->fileno = fileno;
 191   cdbp->filelen = statbuf.st_size;
 192   cdbp->cdb_map = NULL;
 193   cdbp->cdb_offsets = NULL;
 194
 195   /* if we are allowed to we use mmap here.... */
 196 #ifdef HAVE_MMAP
 197   mapbuf = mmap(NULL,
 198                statbuf.st_size,
 199                PROT_READ,
 200                MAP_SHARED,
 201                fileno,
 202                0);
 203   if (mapbuf != MAP_FAILED) {
 204     /* We have an mmap-ed section.  Now we can just use it */
 205     cdbp->cdb_map = mapbuf;
 206     /* The offsets can be set to the same value since they should
 207      * effectively be cached as well
 208      */
 209     cdbp->cdb_offsets = mapbuf;
 210
 211     /* Now return the state struct */
 212     return(cdbp);
 213   } else {
 214     /* If we got here the map failed.  Basically we can ignore
 215      * this since we fall back to slower methods....
 216      * However lets debug log it...
 217      */
 218     DEBUG(D_lookup) debug_printf("cdb mmap failed - %d\n", errno);
 219   }
 220 #endif /* HAVE_MMAP */
 221
 222   /* In this case we have either not got MMAP allowed, or it failed */
 223
 224   /* get a buffer to stash the basic offsets in - this should speed
 225    * things up a lot - especially on multiple lookups */
 226   cdbp->cdb_offsets = store_get(CDB_HASH_TABLE);
 227
 228   /* now fill the buffer up... */
 229   if (cdb_bread(fileno, cdbp->cdb_offsets, CDB_HASH_TABLE) == -1) {
 230     /* read of hash table failed, oh dear, oh.....
 231      * time to give up I think....
 232      * call the close routine (deallocs the memory), and return NULL */
 233     *errmsg = string_open_failed(errno,
 234                                 "cannot read header from %s for cdb lookup",
 235                                 filename);
 236     cdb_close(cdbp);
 237     return NULL;
 238   }
 239
 240   /* Everything else done - return the cache structure */
 241   return cdbp;
 242 }
 243
 244
 245
 246 /*************************************************
 247 *             Check entry point                  *
 248 *************************************************/
 249
 250 static BOOL
 251 cdb_check(void *handle,
 252          uschar *filename,
 253          int modemask,
 254          uid_t *owners,
 255          gid_t *owngroups,
 256          uschar **errmsg)
 257 {
 258   struct cdb_state * cdbp = handle;
 259   return lf_check_file(cdbp->fileno,
 260                        filename,
 261                        S_IFREG,
 262                        modemask,
 263                        owners,
 264                        owngroups,
 265                        "cdb",
 266                        errmsg) == 0;
 267 }
 268
 269
 270
 271 /*************************************************
 272 *              Find entry point                  *
 273 *************************************************/
 274
 275 static int
 276 cdb_find(void *handle,
 277         uschar *filename,
 278         const uschar *keystring,
 279         int  key_len,
 280         uschar **result,
 281         uschar **errmsg,
 282         BOOL *do_cache)
 283 {
 284   struct cdb_state * cdbp = handle;
 285   uint32 item_key_len,
 286     item_dat_len,
 287     key_hash,
 288     item_hash,
 289     item_posn,
 290     cur_offset,
 291     end_offset,
 292     hash_offset_entry,
 293     hash_offset,
 294     hash_offlen,
 295     hash_slotnm;
 296   int loop;
 297
 298   /* Keep picky compilers happy */
 299   do_cache = do_cache;
 300
 301   key_hash = cdb_hash((uschar *)keystring, key_len);
 302
 303   hash_offset_entry = CDB_HASH_ENTRY * (key_hash & CDB_HASH_MASK);
 304   hash_offset = cdb_unpack(cdbp->cdb_offsets + hash_offset_entry);
 305   hash_offlen = cdb_unpack(cdbp->cdb_offsets + hash_offset_entry + 4);
 306
 307   /* If the offset length is zero this key cannot be in the file */
 308   if (hash_offlen == 0) {
 309     return FAIL;
 310   }
 311   hash_slotnm = (key_hash >> 8) % hash_offlen;
 312
 313   /* check to ensure that the file is not corrupt
 314    * if the hash_offset + (hash_offlen * CDB_HASH_ENTRY) is longer
 315    * than the file, then we have problems.... */
 316   if ((hash_offset + (hash_offlen * CDB_HASH_ENTRY)) > cdbp->filelen) {
 317     *errmsg = string_sprintf("cdb: corrupt cdb file %s (too short)",
 318                             filename);
 319     DEBUG(D_lookup) debug_printf("%s\n", *errmsg);
 320     return DEFER;
 321   }
 322
 323   cur_offset = hash_offset + (hash_slotnm * CDB_HASH_ENTRY);
 324   end_offset = hash_offset + (hash_offlen * CDB_HASH_ENTRY);
 325   /* if we are allowed to we use mmap here.... */
 326 #ifdef HAVE_MMAP
 327   /* make sure the mmap was OK */
 328   if (cdbp->cdb_map != NULL) {
 329     uschar * cur_pos = cur_offset + cdbp->cdb_map;
 330     uschar * end_pos = end_offset + cdbp->cdb_map;
 331     for (loop = 0; (loop < hash_offlen); ++loop) {
 332       item_hash = cdb_unpack(cur_pos);
 333       cur_pos += 4;
 334       item_posn = cdb_unpack(cur_pos);
 335       cur_pos += 4;
 336       /* if the position is zero then we have a definite miss */
 337       if (item_posn == 0)
 338        return FAIL;
 339
 340       if (item_hash == key_hash) {
 341        /* matching hash value */
 342        uschar * item_ptr = cdbp->cdb_map + item_posn;
 343        item_key_len = cdb_unpack(item_ptr);
 344        item_ptr += 4;
 345        item_dat_len = cdb_unpack(item_ptr);
 346        item_ptr += 4;
 347        /* check key length matches */
 348        if (item_key_len == key_len) {
 349          /* finally check if key matches */
 350          if (Ustrncmp(keystring, item_ptr, key_len) == 0) {
 351            /* we have a match....
 352             * make item_ptr point to data */
 353            item_ptr += item_key_len;
 354            /* ... and the returned result */
 355            *result = store_get(item_dat_len + 1);
 356            memcpy(*result, item_ptr, item_dat_len);
 357            (*result)[item_dat_len] = 0;
 358            return OK;
 359          }
 360        }
 361       }
 362       /* handle warp round of table */
 363       if (cur_pos == end_pos)
 364        cur_pos = cdbp->cdb_map + hash_offset;
 365     }
 366     /* looks like we failed... */
 367     return FAIL;
 368   }
 369 #endif /* HAVE_MMAP */
 370   for (loop = 0; (loop < hash_offlen); ++loop) {
 371     uschar packbuf[8];
 372     if (lseek(cdbp->fileno, (off_t) cur_offset,SEEK_SET) == -1) return DEFER;
 373     if (cdb_bread(cdbp->fileno, packbuf,8) == -1) return DEFER;
 374     item_hash = cdb_unpack(packbuf);
 375     item_posn = cdb_unpack(packbuf + 4);
 376     /* if the position is zero then we have a definite miss */
 377     if (item_posn == 0)
 378       return FAIL;
 379
 380     if (item_hash == key_hash) {
 381       /* matching hash value */
 382       if (lseek(cdbp->fileno, (off_t) item_posn, SEEK_SET) == -1) return DEFER;
 383       if (cdb_bread(cdbp->fileno, packbuf, 8) == -1) return DEFER;
 384       item_key_len = cdb_unpack(packbuf);
 385       /* check key length matches */
 386       if (item_key_len == key_len) {
 387        /* finally check if key matches */
 388        uschar * item_key = store_get(key_len);
 389        if (cdb_bread(cdbp->fileno, item_key, key_len) == -1) return DEFER;
 390        if (Ustrncmp(keystring, item_key, key_len) == 0) {
 391          /* Reclaim some store */
 392          store_reset(item_key);
 393          /* matches - get data length */
 394          item_dat_len = cdb_unpack(packbuf + 4);
 395          /* then we build a new result string */
 396          *result = store_get(item_dat_len + 1);
 397          if (cdb_bread(cdbp->fileno, *result, item_dat_len) == -1)
 398            return DEFER;
 399          (*result)[item_dat_len] = 0;
 400          return OK;
 401        }
 402        /* Reclaim some store */
 403        store_reset(item_key);
 404       }
 405     }
 406     cur_offset += 8;
 407
 408     /* handle warp round of table */
 409     if (cur_offset == end_offset)
 410       cur_offset = hash_offset;
 411   }
 412   return FAIL;
 413 }
 414
 415
 416
 417 /*************************************************
 418 *              Close entry point                 *
 419 *************************************************/
 420
 421 /* See local README for interface description */
 422
 423 static void
 424 cdb_close(void *handle)
 425 {
 426 struct cdb_state * cdbp = handle;
 427
 428 #ifdef HAVE_MMAP
 429  if (cdbp->cdb_map) {
 430    munmap(CS cdbp->cdb_map, cdbp->filelen);
 431    if (cdbp->cdb_map == cdbp->cdb_offsets)
 432      cdbp->cdb_offsets = NULL;
 433  }
 434 #endif /* HAVE_MMAP */
 435
 436  (void)close(cdbp->fileno);
 437 }
 438
 439
 440
 441 /*************************************************
 442 *         Version reporting entry point          *
 443 *************************************************/
 444
 445 /* See local README for interface description. */
 446
 447 #include "../version.h"
 448
 449 void
 450 cdb_version_report(FILE *f)
 451 {
 452 #ifdef DYNLOOKUP
 453 fprintf(f, "Library version: CDB: Exim version %s\n", EXIM_VERSION_STR);
 454 #endif
 455 }
 456
 457
 458 lookup_info cdb_lookup_info = {
 459   US"cdb",                       /* lookup name */
 460   lookup_absfile,                /* uses absolute file name */
 461   cdb_open,                      /* open function */
 462   cdb_check,                     /* check function */
 463   cdb_find,                      /* find function */
 464   cdb_close,                     /* close function */
 465   NULL,                          /* no tidy function */
 466   NULL,                          /* no quoting function */
 467   cdb_version_report             /* version reporting */
 468 };
 469
 470 #ifdef DYNLOOKUP
 471 #define cdb_lookup_module_info _lookup_module_info
 472 #endif
 473
 474 static lookup_info *_lookup_list[] = { &cdb_lookup_info };
 475 lookup_module_info cdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
 476
 477 /* End of lookups/cdb.c */