1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
6 * Exim - CDB database lookup module
7 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
9 * Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd
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.
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:
23 * --------------------------------------------------------------
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.
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
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
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.
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
59 #include "lf_functions.h"
62 # include <sys/mman.h>
63 /* Not all implementations declare MAP_FAILED */
65 # define MAP_FAILED ((void *) -1)
66 # endif /* MAP_FAILED */
67 #endif /* HAVE_MMAP */
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)
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....
89 /* 32 bit unsigned type - this is an int on all modern machines */
90 typedef unsigned int uint32;
94 * Internal function to make hash value */
97 cdb_hash(const uschar *buf, unsigned int len)
105 h ^= (uint32) *buf++;
112 * Internal function to read len bytes from disk, coping with oddities */
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; }
134 * Internal function to parse 4 byte number (endian independent) */
137 cdb_unpack(uschar *buf)
140 num = buf[3]; num <<= 8;
141 num += buf[2]; num <<= 8;
142 num += buf[1]; num <<= 8;
147 static void cdb_close(void *handle);
150 cdb_open(uschar *filename,
154 struct cdb_state *cdbp;
158 fileno = Uopen(filename, O_RDONLY, 0);
160 int save_errno = errno;
161 *errmsg = string_open_failed(errno, "%s for cdb lookup", filename);
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",
178 int save_errno = errno;
179 *errmsg = string_open_failed(errno,
180 "fstat(%s) failed - cannot do cdb lookup",
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;
195 /* if we are allowed to we use mmap here.... */
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
209 cdbp->cdb_offsets = mapbuf;
211 /* Now return the state struct */
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...
218 DEBUG(D_lookup) debug_printf("cdb mmap failed - %d\n", errno);
220 #endif /* HAVE_MMAP */
222 /* In this case we have either not got MMAP allowed, or it failed */
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);
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",
240 /* Everything else done - return the cache structure */
246 /*************************************************
247 * Check entry point *
248 *************************************************/
251 cdb_check(void *handle,
258 struct cdb_state * cdbp = handle;
259 return lf_check_file(cdbp->fileno,
271 /*************************************************
273 *************************************************/
276 cdb_find(void *handle,
278 const uschar *keystring,
284 struct cdb_state * cdbp = handle;
297 /* Keep picky compilers happy */
300 key_hash = cdb_hash(keystring, key_len);
302 hash_offset_entry = CDB_HASH_ENTRY * (key_hash & CDB_HASH_MASK);
303 hash_offset = cdb_unpack(cdbp->cdb_offsets + hash_offset_entry);
304 hash_offlen = cdb_unpack(cdbp->cdb_offsets + hash_offset_entry + 4);
306 /* If the offset length is zero this key cannot be in the file */
308 if (hash_offlen == 0)
311 hash_slotnm = (key_hash >> 8) % hash_offlen;
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.... */
317 if ((hash_offset + (hash_offlen * CDB_HASH_ENTRY)) > cdbp->filelen)
319 *errmsg = string_sprintf("cdb: corrupt cdb file %s (too short)",
321 DEBUG(D_lookup) debug_printf("%s\n", *errmsg);
325 cur_offset = hash_offset + (hash_slotnm * CDB_HASH_ENTRY);
326 end_offset = hash_offset + (hash_offlen * CDB_HASH_ENTRY);
328 /* if we are allowed to we use mmap here.... */
331 /* make sure the mmap was OK */
332 if (cdbp->cdb_map != NULL)
334 uschar * cur_pos = cur_offset + cdbp->cdb_map;
335 uschar * end_pos = end_offset + cdbp->cdb_map;
337 for (int loop = 0; (loop < hash_offlen); ++loop)
339 item_hash = cdb_unpack(cur_pos);
341 item_posn = cdb_unpack(cur_pos);
344 /* if the position is zero then we have a definite miss */
349 if (item_hash == key_hash)
350 { /* matching hash value */
351 uschar * item_ptr = cdbp->cdb_map + item_posn;
353 item_key_len = cdb_unpack(item_ptr);
355 item_dat_len = cdb_unpack(item_ptr);
358 /* check key length matches */
360 if (item_key_len == key_len)
362 /* finally check if key matches */
363 if (Ustrncmp(keystring, item_ptr, key_len) == 0)
365 /* we have a match.... * make item_ptr point to data */
367 item_ptr += item_key_len;
369 /* ... and the returned result */
371 *result = store_get(item_dat_len + 1);
372 memcpy(*result, item_ptr, item_dat_len);
373 (*result)[item_dat_len] = 0;
378 /* handle warp round of table */
379 if (cur_pos == end_pos)
380 cur_pos = cdbp->cdb_map + hash_offset;
382 /* looks like we failed... */
386 #endif /* HAVE_MMAP */
388 for (int loop = 0; (loop < hash_offlen); ++loop)
392 if (lseek(cdbp->fileno, (off_t) cur_offset, SEEK_SET) == -1) return DEFER;
393 if (cdb_bread(cdbp->fileno, packbuf, 8) == -1) return DEFER;
395 item_hash = cdb_unpack(packbuf);
396 item_posn = cdb_unpack(packbuf + 4);
398 /* if the position is zero then we have a definite miss */
403 if (item_hash == key_hash)
404 { /* matching hash value */
405 if (lseek(cdbp->fileno, (off_t) item_posn, SEEK_SET) == -1) return DEFER;
406 if (cdb_bread(cdbp->fileno, packbuf, 8) == -1) return DEFER;
408 item_key_len = cdb_unpack(packbuf);
410 /* check key length matches */
412 if (item_key_len == key_len)
413 { /* finally check if key matches */
414 uschar * item_key = store_get(key_len);
416 if (cdb_bread(cdbp->fileno, item_key, key_len) == -1) return DEFER;
417 if (Ustrncmp(keystring, item_key, key_len) == 0) {
419 /* Reclaim some store */
420 store_reset(item_key);
422 /* matches - get data length */
423 item_dat_len = cdb_unpack(packbuf + 4);
425 /* then we build a new result string. We know we have enough
426 memory so disable Coverity errors about the tainted item_dat_ken */
428 *result = store_get(item_dat_len + 1);
429 /* coverity[tainted_data] */
430 if (cdb_bread(cdbp->fileno, *result, item_dat_len) == -1)
433 /* coverity[tainted_data] */
434 (*result)[item_dat_len] = 0;
437 /* Reclaim some store */
438 store_reset(item_key);
443 /* handle warp round of table */
444 if (cur_offset == end_offset)
445 cur_offset = hash_offset;
452 /*************************************************
453 * Close entry point *
454 *************************************************/
456 /* See local README for interface description */
459 cdb_close(void *handle)
461 struct cdb_state * cdbp = handle;
466 munmap(CS cdbp->cdb_map, cdbp->filelen);
467 if (cdbp->cdb_map == cdbp->cdb_offsets)
468 cdbp->cdb_offsets = NULL;
470 #endif /* HAVE_MMAP */
472 (void)close(cdbp->fileno);
477 /*************************************************
478 * Version reporting entry point *
479 *************************************************/
481 /* See local README for interface description. */
483 #include "../version.h"
486 cdb_version_report(FILE *f)
489 fprintf(f, "Library version: CDB: Exim version %s\n", EXIM_VERSION_STR);
494 lookup_info cdb_lookup_info = {
495 US"cdb", /* lookup name */
496 lookup_absfile, /* uses absolute file name */
497 cdb_open, /* open function */
498 cdb_check, /* check function */
499 cdb_find, /* find function */
500 cdb_close, /* close function */
501 NULL, /* no tidy function */
502 NULL, /* no quoting function */
503 cdb_version_report /* version reporting */
507 #define cdb_lookup_module_info _lookup_module_info
510 static lookup_info *_lookup_list[] = { &cdb_lookup_info };
511 lookup_module_info cdb_lookup_module_info = { LOOKUP_MODULE_INFO_MAGIC, _lookup_list, 1 };
513 /* End of lookups/cdb.c */