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 variants 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(const 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 independent) */
 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(const uschar * filename, uschar ** errmsg)
 151 {
 152 int fileno;
 153 struct cdb_state *cdbp;
 154 struct stat statbuf;
 155 void * mapbuf;
 156
 157 if ((fileno = Uopen(filename, O_RDONLY, 0)) < 0)
 158   {
 159   int save_errno = errno;
 160   *errmsg = string_open_failed(errno, "%s for cdb lookup", filename);
 161   errno = save_errno;
 162   return NULL;
 163   }
 164
 165 if (fstat(fileno, &statbuf) != 0)
 166   {
 167   int save_errno = errno;
 168   *errmsg = string_open_failed(errno,
 169                               "fstat(%s) failed - cannot do cdb lookup",
 170                               filename);
 171   errno = save_errno;
 172   return NULL;
 173   }
 174
 175 /* If this is a valid file, then it *must* be at least
 176 CDB_HASH_TABLE bytes long */
 177
 178 if (statbuf.st_size < CDB_HASH_TABLE)
 179   {
 180   int save_errno = errno;
 181   *errmsg = string_open_failed(errno,
 182                               "%s too short for cdb lookup",
 183                               filename);
 184   errno = save_errno;
 185   return NULL;
 186   }
 187
 188 /* Having got a file open we need the structure to put things in */
 189 cdbp = store_get(sizeof(struct cdb_state), FALSE);
 190 /* store_get() does not return if memory was not available... */
 191 /* preload the structure.... */
 192 cdbp->fileno = fileno;
 193 cdbp->filelen = statbuf.st_size;
 194 cdbp->cdb_map = NULL;
 195 cdbp->cdb_offsets = NULL;
 196
 197 /* if we are allowed to we use mmap here.... */
 198 #ifdef HAVE_MMAP
 199 if ((mapbuf = mmap(NULL, statbuf.st_size, PROT_READ, MAP_SHARED, fileno, 0))
 200     != MAP_FAILED)
 201   {
 202   /* We have an mmap-ed section.  Now we can just use it */
 203   cdbp->cdb_map = mapbuf;
 204   /* The offsets can be set to the same value since they should
 205    * effectively be cached as well
 206    */
 207   cdbp->cdb_offsets = mapbuf;
 208
 209   /* Now return the state struct */
 210   return(cdbp);
 211   }
 212
 213 /* If we got here the map failed.  Basically we can ignore this since we fall
 214 back to slower methods....  However lets debug log it...  */
 215
 216 DEBUG(D_lookup) debug_printf_indent("cdb mmap failed - %d\n", errno);
 217 #endif /* HAVE_MMAP */
 218
 219 /* In this case we have either not got MMAP allowed, or it failed */
 220
 221 /* get a buffer to stash the basic offsets in - this should speed
 222 things up a lot - especially on multiple lookups */
 223
 224 cdbp->cdb_offsets = store_get(CDB_HASH_TABLE, FALSE);
 225
 226 /* now fill the buffer up... */
 227
 228 if (cdb_bread(fileno, cdbp->cdb_offsets, CDB_HASH_TABLE) == -1)
 229   {
 230   /* read of hash table failed, oh dear, oh.....  time to give up I think....
 231   call the close routine (deallocs the memory), and return NULL */
 232
 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, const uschar * filename, int modemask,
 252   uid_t * owners, gid_t * owngroups, uschar ** errmsg)
 253 {
 254 struct cdb_state * cdbp = handle;
 255 return lf_check_file(cdbp->fileno, filename, S_IFREG, modemask,
 256                      owners, owngroups, "cdb", errmsg) == 0;
 257 }
 258
 259
 260
 261 /*************************************************
 262 *              Find entry point                  *
 263 *************************************************/
 264
 265 static int
 266 cdb_find(void * handle, const uschar * filename, const uschar * keystring,
 267   int key_len, uschar ** result, uschar ** errmsg, uint * do_cache)
 268 {
 269 struct cdb_state * cdbp = handle;
 270 uint32 item_key_len,
 271 item_dat_len,
 272 key_hash,
 273 item_hash,
 274 item_posn,
 275 cur_offset,
 276 end_offset,
 277 hash_offset_entry,
 278 hash_offset,
 279 hash_offlen,
 280 hash_slotnm;
 281
 282 /* Keep picky compilers happy */
 283 do_cache = do_cache;
 284
 285 key_hash = cdb_hash(keystring, key_len);
 286
 287 hash_offset_entry = CDB_HASH_ENTRY * (key_hash & CDB_HASH_MASK);
 288 hash_offset = cdb_unpack(cdbp->cdb_offsets + hash_offset_entry);
 289 hash_offlen = cdb_unpack(cdbp->cdb_offsets + hash_offset_entry + 4);
 290
 291 /* If the offset length is zero this key cannot be in the file */
 292
 293 if (hash_offlen == 0)
 294   return FAIL;
 295
 296 hash_slotnm = (key_hash >> 8) % hash_offlen;
 297
 298 /* check to ensure that the file is not corrupt
 299  * if the hash_offset + (hash_offlen * CDB_HASH_ENTRY) is longer
 300  * than the file, then we have problems.... */
 301
 302 if ((hash_offset + (hash_offlen * CDB_HASH_ENTRY)) > cdbp->filelen)
 303   {
 304   *errmsg = string_sprintf("cdb: corrupt cdb file %s (too short)",
 305                       filename);
 306   DEBUG(D_lookup) debug_printf_indent("%s\n", *errmsg);
 307   return DEFER;
 308   }
 309
 310 cur_offset = hash_offset + (hash_slotnm * CDB_HASH_ENTRY);
 311 end_offset = hash_offset + (hash_offlen * CDB_HASH_ENTRY);
 312
 313 /* if we are allowed to we use mmap here.... */
 314
 315 #ifdef HAVE_MMAP
 316 /* make sure the mmap was OK */
 317 if (cdbp->cdb_map != NULL)
 318   {
 319   uschar * cur_pos = cur_offset + cdbp->cdb_map;
 320   uschar * end_pos = end_offset + cdbp->cdb_map;
 321
 322   for (int loop = 0; (loop < hash_offlen); ++loop)
 323     {
 324     item_hash = cdb_unpack(cur_pos);
 325     cur_pos += 4;
 326     item_posn = cdb_unpack(cur_pos);
 327     cur_pos += 4;
 328
 329     /* if the position is zero then we have a definite miss */
 330
 331     if (item_posn == 0)
 332       return FAIL;
 333
 334     if (item_hash == key_hash)
 335       {                                 /* matching hash value */
 336       uschar * item_ptr = cdbp->cdb_map + item_posn;
 337
 338       item_key_len = cdb_unpack(item_ptr);
 339       item_ptr += 4;
 340       item_dat_len = cdb_unpack(item_ptr);
 341       item_ptr += 4;
 342
 343       /* check key length matches */
 344
 345       if (item_key_len == key_len)
 346         {
 347          /* finally check if key matches */
 348          if (Ustrncmp(keystring, item_ptr, key_len) == 0)
 349            {
 350            /* we have a match....  * make item_ptr point to data */
 351
 352            item_ptr += item_key_len;
 353
 354            /* ... and the returned result.  Assume it is not
 355            tainted, lacking any way of telling.  */
 356
 357            *result = store_get(item_dat_len + 1, FALSE);
 358            memcpy(*result, item_ptr, item_dat_len);
 359            (*result)[item_dat_len] = 0;
 360            return OK;
 361            }
 362         }
 363       }
 364     /* handle warp round of table */
 365     if (cur_pos == end_pos)
 366     cur_pos = cdbp->cdb_map + hash_offset;
 367     }
 368   /* looks like we failed... */
 369   return FAIL;
 370   }
 371
 372 #endif /* HAVE_MMAP */
 373
 374 for (int loop = 0; (loop < hash_offlen); ++loop)
 375   {
 376   uschar packbuf[8];
 377
 378   if (lseek(cdbp->fileno, (off_t) cur_offset, SEEK_SET) == -1) return DEFER;
 379   if (cdb_bread(cdbp->fileno, packbuf, 8) == -1) return DEFER;
 380
 381   item_hash = cdb_unpack(packbuf);
 382   item_posn = cdb_unpack(packbuf + 4);
 383
 384   /* if the position is zero then we have a definite miss */
 385
 386   if (item_posn == 0)
 387     return FAIL;
 388
 389   if (item_hash == key_hash)
 390     {                                           /* matching hash value */
 391     if (lseek(cdbp->fileno, (off_t) item_posn, SEEK_SET) == -1) return DEFER;
 392     if (cdb_bread(cdbp->fileno, packbuf, 8) == -1) return DEFER;
 393
 394     item_key_len = cdb_unpack(packbuf);
 395
 396     /* check key length matches */
 397
 398     if (item_key_len == key_len)
 399       {                                 /* finally check if key matches */
 400       rmark reset_point = store_mark();
 401       uschar * item_key = store_get(key_len, TRUE); /* keys liable to be tainted */
 402
 403       if (cdb_bread(cdbp->fileno, item_key, key_len) == -1) return DEFER;
 404       if (Ustrncmp(keystring, item_key, key_len) == 0)
 405         {
 406         /* Reclaim some store */
 407         store_reset(reset_point);
 408
 409         /* matches - get data length */
 410         item_dat_len = cdb_unpack(packbuf + 4);
 411
 412         /* then we build a new result string.  We know we have enough
 413         memory so disable Coverity errors about the tainted item_dat_ken */
 414
 415         *result = store_get(item_dat_len + 1, FALSE);
 416         /* coverity[tainted_data] */
 417         if (cdb_bread(cdbp->fileno, *result, item_dat_len) == -1)
 418           return DEFER;
 419
 420         /* coverity[tainted_data] */
 421         (*result)[item_dat_len] = 0;
 422         return OK;
 423         }
 424       /* Reclaim some store */
 425       store_reset(reset_point);
 426       }
 427     }
 428   cur_offset += 8;
 429
 430   /* handle warp round of table */
 431   if (cur_offset == end_offset)
 432   cur_offset = hash_offset;
 433   }
 434 return FAIL;
 435 }
 436
 437
 438
 439 /*************************************************
 440 *              Close entry point                 *
 441 *************************************************/
 442
 443 /* See local README for interface description */
 444
 445 static void
 446 cdb_close(void *handle)
 447 {
 448 struct cdb_state * cdbp = handle;
 449
 450 #ifdef HAVE_MMAP
 451 if (cdbp->cdb_map)
 452   {
 453   munmap(CS cdbp->cdb_map, cdbp->filelen);
 454   if (cdbp->cdb_map == cdbp->cdb_offsets)
 455      cdbp->cdb_offsets = NULL;
 456   }
 457 #endif /* HAVE_MMAP */
 458
 459 (void)close(cdbp->fileno);
 460 }
 461
 462
 463
 464 /*************************************************
 465 *         Version reporting entry point          *
 466 *************************************************/
 467
 468 /* See local README for interface description. */
 469
 470 #include "../version.h"
 471
 472 void
 473 cdb_version_report(FILE *f)
 474 {
 475 #ifdef DYNLOOKUP
 476 fprintf(f, "Library version: CDB: Exim version %s\n", EXIM_VERSION_STR);
 477 #endif
 478 }
 479
 480
 481 lookup_info cdb_lookup_info = {
 482   US"cdb",                       /* lookup name */
 483   lookup_absfile,                /* uses absolute file name */
 484   cdb_open,                      /* open function */
 485   cdb_check,                     /* check function */
 486   cdb_find,                      /* find function */
 487   cdb_close,                     /* close function */
 488   NULL,                          /* no tidy function */
 489   NULL,                          /* no quoting function */
 490   cdb_version_report             /* version reporting */
 491 };
 492
 493 #ifdef DYNLOOKUP
 494 #define cdb_lookup_module_info _lookup_module_info
 495 #endif
 496
 497 static lookup_info *_lookup_list[] = { &cdb_lookup_info };
 498 lookup_module_info cdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
 499
 500 /* End of lookups/cdb.c */