1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) The Exim Maintainers 2020 - 2024 */
6 /* Copyright (c) University of Cambridge 1995 - 2018 */
7 /* See the file NOTICE for conditions of use and distribution. */
8 /* SPDX-License-Identifier: GPL-2.0-or-later */
13 /* We have buffers holding path names for database files.
14 PATH_MAX could be used here, but would be wasting memory, as we deal
15 with database files like $spooldirectory/db/<name> */
19 /* Functions for accessing Exim's hints database, which consists of a number of
20 different DBM files. This module does not contain code for reading DBM files
21 for (e.g.) alias expansion. That is all contained within the general search
22 functions. As Exim now has support for several DBM interfaces, all the relevant
23 functions are called as inlinable functions from an included file.
25 All the data in Exim's database is in the nature of *hints*. Therefore it
26 doesn't matter if it gets destroyed by accident. These functions are not
27 supposed to implement a "safe" database.
29 Keys are passed in as C strings, and the terminating zero *is* used when
30 building the dbm files. This just makes life easier when scanning the files
33 Synchronization is required on the database files, and this is achieved by
34 means of locking on independent lock files. (Earlier attempts to lock on the
35 DBM files themselves were never completely successful.) Since callers may in
36 general want to do more than one read or write while holding the lock, there
37 are separate open and close functions. However, the calling modules should
38 arrange to hold the locks for the bare minimum of time.
44 dbfn_read_enforce_length
47 dbfn_scan unused; ifdeffout out
50 ACL ratelimit & seen conditions
51 delivery retry handling
52 delivery serialization
53 TLS session resumption
60 /*************************************************
61 * Open and lock a database file *
62 *************************************************/
64 /* Used for accessing Exim's hints databases.
67 name The single-component name of one of Exim's database files.
68 flags Either O_RDONLY or O_RDWR, indicating the type of open required;
69 O_RDWR implies "create if necessary"
70 dbblock Points to an open_db block to be filled in.
71 lof If TRUE, write to the log for actual open failures (locking failures
73 panic If TRUE, panic on failure to create the db directory
75 Returns: NULL if the open failed, or the locking failed. After locking
76 failures, errno is zero.
78 On success, dbblock is returned. This contains the dbm pointer and
79 the fd of the locked lock file.
83 dbfn_open(const uschar * name, int flags, open_db * dbblock,
87 BOOL read_only = flags & O_RDONLY;
89 uschar dirname[PATHLEN], filename[PATHLEN];
91 DEBUG(D_hints_lookup) acl_level++;
93 /* The first thing to do is to open a separate file on which to lock. This
94 ensures that Exim has exclusive use of the database before it even tries to
95 open it. Early versions tried to lock on the open database itself, but that
96 gave rise to mysterious problems from time to time - it was suspected that some
97 DB libraries "do things" on their open() calls which break the interlocking.
98 The lock file is never written to, but we open it for writing so we can get a
99 write lock if required. If it does not exist, we create it. This is done
100 separately so we know when we have done it, because when running as root we
101 need to change the ownership - see the bottom of this function. We also try to
102 make the directory as well, just in case. We won't be doing this many times
103 unnecessarily, because usually the lock file will be there. If the directory
104 exists, there is no error. */
106 snprintf(CS dirname, sizeof(dirname), "%s/db", spool_directory);
107 snprintf(CS filename, sizeof(filename), "%s/%s.lockfile", dirname, name);
109 priv_drop_temp(exim_uid, exim_gid);
110 if ((dbblock->lockfd = Uopen(filename, O_RDWR, EXIMDB_LOCKFILE_MODE)) < 0)
112 (void)directory_make(spool_directory, US"db", EXIMDB_DIRECTORY_MODE, panic);
113 dbblock->lockfd = Uopen(filename, O_RDWR|O_CREAT, EXIMDB_LOCKFILE_MODE);
117 if (dbblock->lockfd < 0)
119 log_write(0, LOG_MAIN, "%s",
120 string_open_failed("database lock file %s", filename));
121 errno = 0; /* Indicates locking failure */
122 DEBUG(D_hints_lookup) acl_level--;
126 /* Now we must get a lock on the opened lock file; do this with a blocking
127 lock that times out. */
129 lock_data.l_type = read_only? F_RDLCK : F_WRLCK;
130 lock_data.l_whence = lock_data.l_start = lock_data.l_len = 0;
132 DEBUG(D_hints_lookup|D_retry|D_route|D_deliver)
133 debug_printf_indent("locking %s\n", filename);
135 sigalrm_seen = FALSE;
136 ALARM(EXIMDB_LOCK_TIMEOUT);
137 rc = fcntl(dbblock->lockfd, F_SETLKW, &lock_data);
140 if (sigalrm_seen) errno = ETIMEDOUT;
143 log_write(0, LOG_MAIN|LOG_PANIC, "Failed to get %s lock for %s: %s",
144 read_only ? "read" : "write", filename,
145 errno == ETIMEDOUT ? "timed out" : strerror(errno));
146 (void)close(dbblock->lockfd);
147 errno = 0; /* Indicates locking failure */
148 DEBUG(D_hints_lookup) acl_level--;
152 DEBUG(D_hints_lookup) debug_printf_indent("locked %s\n", filename);
154 /* At this point we have an opened and locked separate lock file, that is,
155 exclusive access to the database, so we can go ahead and open it. If we are
156 expected to create it, don't do so at first, again so that we can detect
157 whether we need to change its ownership (see comments about the lock file
158 above.) There have been regular reports of crashes while opening hints
159 databases - often this is caused by non-matching db.h and the library. To make
160 it easy to pin this down, there are now debug statements on either side of the
163 flags &= O_RDONLY | O_RDWR;
164 snprintf(CS filename, sizeof(filename), "%s/%s", dirname, name);
166 priv_drop_temp(exim_uid, exim_gid);
167 dbblock->dbptr = exim_dbopen(filename, dirname, flags, EXIMDB_MODE);
168 if (!dbblock->dbptr && errno == ENOENT && flags == O_RDWR)
170 DEBUG(D_hints_lookup)
171 debug_printf_indent("%s appears not to exist: trying to create\n", filename);
172 dbblock->dbptr = exim_dbopen(filename, dirname, flags|O_CREAT, EXIMDB_MODE);
177 /* If the open has failed, return NULL, leaving errno set. If lof is TRUE,
178 log the event - also for debugging - but debug only if the file just doesn't
184 if (lof && save_errno != ENOENT)
185 log_write(0, LOG_MAIN, "%s", string_open_failed("DB file %s",
188 DEBUG(D_hints_lookup)
189 debug_printf_indent("%s\n", CS string_open_failed("DB file %s",
191 (void)close(dbblock->lockfd);
193 DEBUG(D_hints_lookup) acl_level--;
197 DEBUG(D_hints_lookup)
198 debug_printf_indent("opened hints database %s: flags=%s\n", filename,
199 flags == O_RDONLY ? "O_RDONLY"
200 : flags == O_RDWR ? "O_RDWR"
203 /* Pass back the block containing the opened database handle and the open fd
212 /*************************************************
213 * Unlock and close a database file *
214 *************************************************/
216 /* Closing a file automatically unlocks it, so after closing the database, just
219 Argument: a pointer to an open database block
224 dbfn_close(open_db *dbblock)
226 exim_dbclose(dbblock->dbptr);
227 (void)close(dbblock->lockfd);
228 DEBUG(D_hints_lookup)
229 { debug_printf_indent("closed hints database and lockfile\n"); acl_level--; }
235 /*************************************************
236 * Read from database file *
237 *************************************************/
239 /* Passing back the pointer unchanged is useless, because there is
240 no guarantee of alignment. Since all the records used by Exim need
241 to be properly aligned to pick out the timestamps, etc., we might as
242 well do the copying centrally here.
244 Most calls don't need the length, so there is a macro called dbfn_read which
245 has two arguments; it calls this function adding NULL as the third.
248 dbblock a pointer to an open database block
249 key the key of the record to be read
250 length a pointer to an int into which to return the length, if not NULL
252 Returns: a pointer to the retrieved record, or
253 NULL if the record is not found
257 dbfn_read_with_length(open_db * dbblock, const uschar * key, int * length)
260 EXIM_DATUM key_datum, result_datum;
261 int klen = Ustrlen(key) + 1;
262 uschar * key_copy = store_get(klen, key);
265 memcpy(key_copy, key, klen);
267 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_read: key=%s\n", key);
269 exim_datum_init(&key_datum); /* Some DBM libraries require the datum */
270 exim_datum_init(&result_datum); /* to be cleared before use. */
271 exim_datum_data_set(&key_datum, key_copy);
272 exim_datum_size_set(&key_datum, klen);
274 if (!exim_dbget(dbblock->dbptr, &key_datum, &result_datum))
276 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_read: null return\n");
280 /* Assume the data store could have been tainted. Properly, we should
281 store the taint status with the data. */
283 dlen = exim_datum_size_get(&result_datum);
284 yield = store_get(dlen, GET_TAINTED);
285 memcpy(yield, exim_datum_data_get(&result_datum), dlen);
286 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_read: size %u return\n", dlen);
287 if (length) *length = dlen;
289 exim_datum_free(&result_datum); /* Some DBM libs require freeing */
294 /* Read a record. If the length is not as expected then delete it, write
295 an error log line, delete the record and return NULL.
296 Use this for fixed-size records (so not retry or wait records).
299 dbblock a pointer to an open database block
300 key the key of the record to be read
301 length the expected record length
303 Returns: a pointer to the retrieved record, or
304 NULL if the record is not found/bad
308 dbfn_read_enforce_length(open_db * dbblock, const uschar * key, size_t length)
311 void * yield = dbfn_read_with_length(dbblock, key, &rlen);
315 if (rlen == length) return yield;
316 log_write(0, LOG_MAIN|LOG_PANIC, "Bad db record size for '%s'", key);
317 dbfn_delete(dbblock, key);
323 /*************************************************
324 * Write to database file *
325 *************************************************/
329 dbblock a pointer to an open database block
330 key the key of the record to be written
331 ptr a pointer to the record to be written
332 length the length of the record to be written
334 Returns: the yield of the underlying dbm or db "write" function. If this
335 is dbm, the value is zero for OK.
339 dbfn_write(open_db *dbblock, const uschar *key, void *ptr, int length)
341 EXIM_DATUM key_datum, value_datum;
342 dbdata_generic *gptr = (dbdata_generic *)ptr;
343 int klen = Ustrlen(key) + 1;
344 uschar * key_copy = store_get(klen, key);
346 memcpy(key_copy, key, klen);
347 gptr->time_stamp = time(NULL);
349 DEBUG(D_hints_lookup)
350 debug_printf_indent("dbfn_write: key=%s datalen %d\n", key, length);
352 exim_datum_init(&key_datum); /* Some DBM libraries require the datum */
353 exim_datum_init(&value_datum); /* to be cleared before use. */
354 exim_datum_data_set(&key_datum, key_copy);
355 exim_datum_size_set(&key_datum, klen);
356 exim_datum_data_set(&value_datum, ptr);
357 exim_datum_size_set(&value_datum, length);
358 return exim_dbput(dbblock->dbptr, &key_datum, &value_datum);
363 /*************************************************
364 * Delete record from database file *
365 *************************************************/
369 dbblock a pointer to an open database block
370 key the key of the record to be deleted
372 Returns: the yield of the underlying dbm or db "delete" function.
376 dbfn_delete(open_db *dbblock, const uschar *key)
378 int klen = Ustrlen(key) + 1;
379 uschar * key_copy = store_get(klen, key);
380 EXIM_DATUM key_datum;
382 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_delete: key=%s\n", key);
384 memcpy(key_copy, key, klen);
385 exim_datum_init(&key_datum); /* Some DBM libraries require clearing */
386 exim_datum_data_set(&key_datum, key_copy);
387 exim_datum_size_set(&key_datum, klen);
388 return exim_dbdel(dbblock->dbptr, &key_datum);
394 /* XXX This appears to be unused. There's a separate implementation
395 in dbutils.c for dumpdb and fixdb, using the same underlying support.
398 /*************************************************
399 * Scan the keys of a database file *
400 *************************************************/
404 dbblock a pointer to an open database block
405 start TRUE if starting a new scan
406 FALSE if continuing with the current scan
407 cursor a pointer to a pointer to a cursor anchor, for those dbm libraries
408 that use the notion of a cursor
410 Returns: the next record from the file, or
411 NULL if there are no more
415 dbfn_scan(open_db *dbblock, BOOL start, EXIM_CURSOR **cursor)
417 EXIM_DATUM key_datum, value_datum;
420 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_scan\n");
422 /* Some dbm require an initialization */
424 if (start) *cursor = exim_dbcreate_cursor(dbblock->dbptr);
426 exim_datum_init(&key_datum); /* Some DBM libraries require the datum */
427 exim_datum_init(&value_datum); /* to be cleared before use. */
429 yield = exim_dbscan(dbblock->dbptr, &key_datum, &value_datum, start, *cursor)
430 ? US exim_datum_data_get(&key_datum) : NULL;
432 /* Some dbm require a termination */
434 if (!yield) exim_dbdelete_cursor(*cursor);
441 /*************************************************
442 **************************************************
443 * Stand-alone test program *
444 **************************************************
445 *************************************************/
450 main(int argc, char **cargv)
453 int max_db = sizeof(dbblock)/sizeof(open_db);
457 dbdata_wait *dbwait = NULL;
458 uschar **argv = USS cargv;
460 uschar structbuffer[1024];
464 printf("Usage: test_dbfn directory\n");
465 printf("The subdirectory called \"db\" in the given directory is used for\n");
466 printf("the files used in this test program.\n");
472 spool_directory = argv[1];
473 debug_selector = D_all - D_memory;
475 big_buffer = malloc(big_buffer_size);
477 for (i = 0; i < max_db; i++) dbblock[i].dbptr = NULL;
479 printf("\nExim's db functions tester: interface type is %s\n", EXIM_DBTYPE);
480 printf("DBM library: ");
482 #ifdef DB_VERSION_STRING
483 printf("Berkeley DB: %s\n", DB_VERSION_STRING);
484 #elif defined(BTREEVERSION) && defined(HASHVERSION)
486 printf("probably Berkeley DB version 1.8x (native mode)\n");
488 printf("probably Berkeley DB version 1.8x (compatibility mode)\n");
490 #elif defined(_DBM_RDONLY) || defined(dbm_dirfno)
491 printf("probably ndbm\n");
492 #elif defined(USE_TDB)
493 printf("using tdb\n");
496 printf("probably GDBM (native mode)\n");
498 printf("probably GDBM (compatibility mode)\n");
502 /* Test the functions */
504 printf("\nTest the functions\n> ");
506 while (Ufgets(buffer, 256, stdin) != NULL)
508 int len = Ustrlen(buffer);
512 uschar *cmd = buffer;
513 while (len > 0 && isspace((uschar)buffer[len-1])) len--;
516 if (isdigit((uschar)*cmd))
519 while (isdigit((uschar)*cmd)) cmd++;
520 Uskip_whitespace(&cmd);
523 if (Ustrncmp(cmd, "open", 4) == 0)
528 Uskip_whitespace(&s);
530 for (i = 0; i < max_db; i++)
531 if (dbblock[i].dbptr == NULL) break;
535 printf("Too many open databases\n> ");
540 odb = dbfn_open(s, O_RDWR, dbblock + i, TRUE, TRUE);
546 printf("opened %d\n", current);
548 /* Other error cases will have written messages */
549 else if (errno == ENOENT)
551 printf("open failed: %s%s\n", strerror(errno),
553 " (or other Berkeley DB error)"
561 else if (Ustrncmp(cmd, "write", 5) == 0)
564 uschar * key = cmd + 5, * data;
568 printf("No current database\n");
572 Uskip_whitespace(&key);
574 Uskip_nonwhite(&data);
576 Uskip_whitespace(&data);
578 dbwait = (dbdata_wait *)(&structbuffer);
579 Ustrcpy(dbwait->text, data);
583 rc = dbfn_write(dbblock + current, key, dbwait,
584 Ustrlen(data) + sizeof(dbdata_wait));
586 if (rc != 0) printf("Failed: %s\n", strerror(errno));
589 else if (Ustrncmp(cmd, "read", 4) == 0)
591 uschar * key = cmd + 4;
594 printf("No current database\n");
597 Uskip_whitespace(&key);
600 dbwait = (dbdata_wait *)dbfn_read_with_length(dbblock+ current, key, NULL);
602 printf("%s\n", (dbwait == NULL)? "<not found>" : CS dbwait->text);
605 else if (Ustrncmp(cmd, "delete", 6) == 0)
607 uschar * key = cmd + 6;
610 printf("No current database\n");
613 Uskip_whitespace(&key);
614 dbfn_delete(dbblock + current, key);
617 else if (Ustrncmp(cmd, "scan", 4) == 0)
620 BOOL startflag = TRUE;
622 uschar keybuffer[256];
625 printf("No current database\n");
629 while ((key = dbfn_scan(dbblock + current, startflag, &cursor)) != NULL)
632 Ustrcpy(keybuffer, key);
633 dbwait = (dbdata_wait *)dbfn_read_with_length(dbblock + current,
635 printf("%s: %s\n", keybuffer, dbwait->text);
638 printf("End of scan\n");
641 else if (Ustrncmp(cmd, "close", 5) == 0)
643 uschar * s = cmd + 5;
644 Uskip_whitespace(&s);
646 if (i >= max_db || dbblock[i].dbptr == NULL) printf("Not open\n"); else
649 dbfn_close(dbblock + i);
651 dbblock[i].dbptr = NULL;
652 if (i == current) current = -1;
656 else if (Ustrncmp(cmd, "file", 4) == 0)
658 uschar * s = cmd + 4;
659 Uskip_whitespace(&s);
661 if (i >= max_db || dbblock[i].dbptr == NULL) printf("Not open\n");
665 else if (Ustrncmp(cmd, "time", 4) == 0)
667 showtime = ~showtime;
668 printf("Timing %s\n", showtime? "on" : "off");
671 else if (Ustrcmp(cmd, "q") == 0 || Ustrncmp(cmd, "quit", 4) == 0) break;
673 else if (Ustrncmp(cmd, "help", 4) == 0)
675 printf("close [<number>] close file [<number>]\n");
676 printf("delete <key> remove record from current file\n");
677 printf("file <number> make file <number> current\n");
678 printf("open <name> open db file\n");
679 printf("q[uit] exit program\n");
680 printf("read <key> read record from current file\n");
681 printf("scan scan current file\n");
682 printf("time time display on/off\n");
683 printf("write <key> <rest-of-line> write record to current file\n");
686 else printf("Eh?\n");
688 if (showtime && stop >= start)
689 printf("start=%d stop=%d difference=%d\n", (int)start, (int)stop,
690 (int)(stop - start));
695 for (i = 0; i < max_db; i++)
697 if (dbblock[i].dbptr != NULL)
699 printf("\nClosing %d", i);
700 dbfn_close(dbblock + i);