1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
5 /* Copyright (c) The Exim Maintainers 2020 - 2022 */
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.
81 There are some calls that use O_RDWR|O_CREAT for the flags. Having discovered
82 this in December 2005, I'm not sure if this is correct or not, but for the
83 moment I haven't changed them.
87 dbfn_open(uschar *name, int flags, open_db *dbblock, BOOL lof, BOOL panic)
90 BOOL read_only = flags == O_RDONLY;
92 uschar dirname[PATHLEN], filename[PATHLEN];
94 DEBUG(D_hints_lookup) acl_level++;
96 /* The first thing to do is to open a separate file on which to lock. This
97 ensures that Exim has exclusive use of the database before it even tries to
98 open it. Early versions tried to lock on the open database itself, but that
99 gave rise to mysterious problems from time to time - it was suspected that some
100 DB libraries "do things" on their open() calls which break the interlocking.
101 The lock file is never written to, but we open it for writing so we can get a
102 write lock if required. If it does not exist, we create it. This is done
103 separately so we know when we have done it, because when running as root we
104 need to change the ownership - see the bottom of this function. We also try to
105 make the directory as well, just in case. We won't be doing this many times
106 unnecessarily, because usually the lock file will be there. If the directory
107 exists, there is no error. */
109 snprintf(CS dirname, sizeof(dirname), "%s/db", spool_directory);
110 snprintf(CS filename, sizeof(filename), "%s/%s.lockfile", dirname, name);
112 priv_drop_temp(exim_uid, exim_gid);
113 if ((dbblock->lockfd = Uopen(filename, O_RDWR, EXIMDB_LOCKFILE_MODE)) < 0)
115 (void)directory_make(spool_directory, US"db", EXIMDB_DIRECTORY_MODE, panic);
116 dbblock->lockfd = Uopen(filename, O_RDWR|O_CREAT, EXIMDB_LOCKFILE_MODE);
120 if (dbblock->lockfd < 0)
122 log_write(0, LOG_MAIN, "%s",
123 string_open_failed("database lock file %s", filename));
124 errno = 0; /* Indicates locking failure */
125 DEBUG(D_hints_lookup) acl_level--;
129 /* Now we must get a lock on the opened lock file; do this with a blocking
130 lock that times out. */
132 lock_data.l_type = read_only? F_RDLCK : F_WRLCK;
133 lock_data.l_whence = lock_data.l_start = lock_data.l_len = 0;
135 DEBUG(D_hints_lookup|D_retry|D_route|D_deliver)
136 debug_printf_indent("locking %s\n", filename);
138 sigalrm_seen = FALSE;
139 ALARM(EXIMDB_LOCK_TIMEOUT);
140 rc = fcntl(dbblock->lockfd, F_SETLKW, &lock_data);
143 if (sigalrm_seen) errno = ETIMEDOUT;
146 log_write(0, LOG_MAIN|LOG_PANIC, "Failed to get %s lock for %s: %s",
147 read_only ? "read" : "write", filename,
148 errno == ETIMEDOUT ? "timed out" : strerror(errno));
149 (void)close(dbblock->lockfd);
150 errno = 0; /* Indicates locking failure */
151 DEBUG(D_hints_lookup) acl_level--;
155 DEBUG(D_hints_lookup) debug_printf_indent("locked %s\n", filename);
157 /* At this point we have an opened and locked separate lock file, that is,
158 exclusive access to the database, so we can go ahead and open it. If we are
159 expected to create it, don't do so at first, again so that we can detect
160 whether we need to change its ownership (see comments about the lock file
161 above.) There have been regular reports of crashes while opening hints
162 databases - often this is caused by non-matching db.h and the library. To make
163 it easy to pin this down, there are now debug statements on either side of the
166 snprintf(CS filename, sizeof(filename), "%s/%s", dirname, name);
168 priv_drop_temp(exim_uid, exim_gid);
169 dbblock->dbptr = exim_dbopen(filename, dirname, flags, EXIMDB_MODE);
170 if (!dbblock->dbptr && errno == ENOENT && flags == O_RDWR)
172 DEBUG(D_hints_lookup)
173 debug_printf_indent("%s appears not to exist: trying to create\n", filename);
174 dbblock->dbptr = exim_dbopen(filename, dirname, flags|O_CREAT, EXIMDB_MODE);
179 /* If the open has failed, return NULL, leaving errno set. If lof is TRUE,
180 log the event - also for debugging - but debug only if the file just doesn't
186 if (lof && save_errno != ENOENT)
187 log_write(0, LOG_MAIN, "%s", string_open_failed("DB file %s",
190 DEBUG(D_hints_lookup)
191 debug_printf_indent("%s\n", CS string_open_failed("DB file %s",
193 (void)close(dbblock->lockfd);
195 DEBUG(D_hints_lookup) acl_level--;
199 DEBUG(D_hints_lookup)
200 debug_printf_indent("opened hints database %s: flags=%s\n", filename,
201 flags == O_RDONLY ? "O_RDONLY"
202 : flags == O_RDWR ? "O_RDWR"
203 : flags == (O_RDWR|O_CREAT) ? "O_RDWR|O_CREAT"
206 /* Pass back the block containing the opened database handle and the open fd
215 /*************************************************
216 * Unlock and close a database file *
217 *************************************************/
219 /* Closing a file automatically unlocks it, so after closing the database, just
222 Argument: a pointer to an open database block
227 dbfn_close(open_db *dbblock)
229 exim_dbclose(dbblock->dbptr);
230 (void)close(dbblock->lockfd);
231 DEBUG(D_hints_lookup)
232 { debug_printf_indent("closed hints database and lockfile\n"); acl_level--; }
238 /*************************************************
239 * Read from database file *
240 *************************************************/
242 /* Passing back the pointer unchanged is useless, because there is
243 no guarantee of alignment. Since all the records used by Exim need
244 to be properly aligned to pick out the timestamps, etc., we might as
245 well do the copying centrally here.
247 Most calls don't need the length, so there is a macro called dbfn_read which
248 has two arguments; it calls this function adding NULL as the third.
251 dbblock a pointer to an open database block
252 key the key of the record to be read
253 length a pointer to an int into which to return the length, if not NULL
255 Returns: a pointer to the retrieved record, or
256 NULL if the record is not found
260 dbfn_read_with_length(open_db * dbblock, const uschar * key, int * length)
263 EXIM_DATUM key_datum, result_datum;
264 int klen = Ustrlen(key) + 1;
265 uschar * key_copy = store_get(klen, key);
268 memcpy(key_copy, key, klen);
270 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_read: key=%s\n", key);
272 exim_datum_init(&key_datum); /* Some DBM libraries require the datum */
273 exim_datum_init(&result_datum); /* to be cleared before use. */
274 exim_datum_data_set(&key_datum, key_copy);
275 exim_datum_size_set(&key_datum, klen);
277 if (!exim_dbget(dbblock->dbptr, &key_datum, &result_datum)) return NULL;
279 /* Assume the data store could have been tainted. Properly, we should
280 store the taint status with the data. */
282 dlen = exim_datum_size_get(&result_datum);
283 yield = store_get(dlen, GET_TAINTED);
284 memcpy(yield, exim_datum_data_get(&result_datum), dlen);
285 if (length) *length = dlen;
287 exim_datum_free(&result_datum); /* Some DBM libs require freeing */
292 /* Read a record. If the length is not as expected then delete it, write
293 an error log line, delete the record and return NULL.
294 Use this for fixed-size records (so not retry or wait records).
297 dbblock a pointer to an open database block
298 key the key of the record to be read
299 length the expected record length
301 Returns: a pointer to the retrieved record, or
302 NULL if the record is not found/bad
306 dbfn_read_enforce_length(open_db * dbblock, const uschar * key, size_t length)
309 void * yield = dbfn_read_with_length(dbblock, key, &rlen);
313 if (rlen == length) return yield;
314 log_write(0, LOG_MAIN|LOG_PANIC, "Bad db record size for '%s'", key);
315 dbfn_delete(dbblock, key);
321 /*************************************************
322 * Write to database file *
323 *************************************************/
327 dbblock a pointer to an open database block
328 key the key of the record to be written
329 ptr a pointer to the record to be written
330 length the length of the record to be written
332 Returns: the yield of the underlying dbm or db "write" function. If this
333 is dbm, the value is zero for OK.
337 dbfn_write(open_db *dbblock, const uschar *key, void *ptr, int length)
339 EXIM_DATUM key_datum, value_datum;
340 dbdata_generic *gptr = (dbdata_generic *)ptr;
341 int klen = Ustrlen(key) + 1;
342 uschar * key_copy = store_get(klen, key);
344 memcpy(key_copy, key, klen);
345 gptr->time_stamp = time(NULL);
347 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_write: key=%s\n", key);
349 exim_datum_init(&key_datum); /* Some DBM libraries require the datum */
350 exim_datum_init(&value_datum); /* to be cleared before use. */
351 exim_datum_data_set(&key_datum, key_copy);
352 exim_datum_size_set(&key_datum, klen);
353 exim_datum_data_set(&value_datum, ptr);
354 exim_datum_size_set(&value_datum, length);
355 return exim_dbput(dbblock->dbptr, &key_datum, &value_datum);
360 /*************************************************
361 * Delete record from database file *
362 *************************************************/
366 dbblock a pointer to an open database block
367 key the key of the record to be deleted
369 Returns: the yield of the underlying dbm or db "delete" function.
373 dbfn_delete(open_db *dbblock, const uschar *key)
375 int klen = Ustrlen(key) + 1;
376 uschar * key_copy = store_get(klen, key);
377 EXIM_DATUM key_datum;
379 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_delete: key=%s\n", key);
381 memcpy(key_copy, key, klen);
382 exim_datum_init(&key_datum); /* Some DBM libraries require clearing */
383 exim_datum_data_set(&key_datum, key_copy);
384 exim_datum_size_set(&key_datum, klen);
385 return exim_dbdel(dbblock->dbptr, &key_datum);
390 /*************************************************
391 * Scan the keys of a database file *
392 *************************************************/
396 dbblock a pointer to an open database block
397 start TRUE if starting a new scan
398 FALSE if continuing with the current scan
399 cursor a pointer to a pointer to a cursor anchor, for those dbm libraries
400 that use the notion of a cursor
402 Returns: the next record from the file, or
403 NULL if there are no more
407 dbfn_scan(open_db *dbblock, BOOL start, EXIM_CURSOR **cursor)
409 EXIM_DATUM key_datum, value_datum;
412 DEBUG(D_hints_lookup) debug_printf_indent("dbfn_scan\n");
414 /* Some dbm require an initialization */
416 if (start) *cursor = exim_dbcreate_cursor(dbblock->dbptr);
418 exim_datum_init(&key_datum); /* Some DBM libraries require the datum */
419 exim_datum_init(&value_datum); /* to be cleared before use. */
421 yield = exim_dbscan(dbblock->dbptr, &key_datum, &value_datum, start, *cursor)
422 ? US exim_datum_data_get(&key_datum) : NULL;
424 /* Some dbm require a termination */
426 if (!yield) exim_dbdelete_cursor(*cursor);
432 /*************************************************
433 **************************************************
434 * Stand-alone test program *
435 **************************************************
436 *************************************************/
441 main(int argc, char **cargv)
444 int max_db = sizeof(dbblock)/sizeof(open_db);
448 dbdata_wait *dbwait = NULL;
449 uschar **argv = USS cargv;
451 uschar structbuffer[1024];
455 printf("Usage: test_dbfn directory\n");
456 printf("The subdirectory called \"db\" in the given directory is used for\n");
457 printf("the files used in this test program.\n");
463 spool_directory = argv[1];
464 debug_selector = D_all - D_memory;
466 big_buffer = malloc(big_buffer_size);
468 for (i = 0; i < max_db; i++) dbblock[i].dbptr = NULL;
470 printf("\nExim's db functions tester: interface type is %s\n", EXIM_DBTYPE);
471 printf("DBM library: ");
473 #ifdef DB_VERSION_STRING
474 printf("Berkeley DB: %s\n", DB_VERSION_STRING);
475 #elif defined(BTREEVERSION) && defined(HASHVERSION)
477 printf("probably Berkeley DB version 1.8x (native mode)\n");
479 printf("probably Berkeley DB version 1.8x (compatibility mode)\n");
481 #elif defined(_DBM_RDONLY) || defined(dbm_dirfno)
482 printf("probably ndbm\n");
483 #elif defined(USE_TDB)
484 printf("using tdb\n");
487 printf("probably GDBM (native mode)\n");
489 printf("probably GDBM (compatibility mode)\n");
493 /* Test the functions */
495 printf("\nTest the functions\n> ");
497 while (Ufgets(buffer, 256, stdin) != NULL)
499 int len = Ustrlen(buffer);
503 uschar *cmd = buffer;
504 while (len > 0 && isspace((uschar)buffer[len-1])) len--;
507 if (isdigit((uschar)*cmd))
510 while (isdigit((uschar)*cmd)) cmd++;
511 Uskip_whitespace(&cmd);
514 if (Ustrncmp(cmd, "open", 4) == 0)
519 Uskip_whitespace(&s);
521 for (i = 0; i < max_db; i++)
522 if (dbblock[i].dbptr == NULL) break;
526 printf("Too many open databases\n> ");
531 odb = dbfn_open(s, O_RDWR, dbblock + i, TRUE, TRUE);
537 printf("opened %d\n", current);
539 /* Other error cases will have written messages */
540 else if (errno == ENOENT)
542 printf("open failed: %s%s\n", strerror(errno),
544 " (or other Berkeley DB error)"
552 else if (Ustrncmp(cmd, "write", 5) == 0)
555 uschar * key = cmd + 5, * data;
559 printf("No current database\n");
563 Uskip_whitespace(&key);
565 Uskip_nonwhite(&data);
567 Uskip_whitespace(&data);
569 dbwait = (dbdata_wait *)(&structbuffer);
570 Ustrcpy(dbwait->text, data);
574 rc = dbfn_write(dbblock + current, key, dbwait,
575 Ustrlen(data) + sizeof(dbdata_wait));
577 if (rc != 0) printf("Failed: %s\n", strerror(errno));
580 else if (Ustrncmp(cmd, "read", 4) == 0)
582 uschar * key = cmd + 4;
585 printf("No current database\n");
588 Uskip_whitespace(&key);
591 dbwait = (dbdata_wait *)dbfn_read_with_length(dbblock+ current, key, NULL);
593 printf("%s\n", (dbwait == NULL)? "<not found>" : CS dbwait->text);
596 else if (Ustrncmp(cmd, "delete", 6) == 0)
598 uschar * key = cmd + 6;
601 printf("No current database\n");
604 Uskip_whitespace(&key);
605 dbfn_delete(dbblock + current, key);
608 else if (Ustrncmp(cmd, "scan", 4) == 0)
611 BOOL startflag = TRUE;
613 uschar keybuffer[256];
616 printf("No current database\n");
620 while ((key = dbfn_scan(dbblock + current, startflag, &cursor)) != NULL)
623 Ustrcpy(keybuffer, key);
624 dbwait = (dbdata_wait *)dbfn_read_with_length(dbblock + current,
626 printf("%s: %s\n", keybuffer, dbwait->text);
629 printf("End of scan\n");
632 else if (Ustrncmp(cmd, "close", 5) == 0)
634 uschar * s = cmd + 5;
635 Uskip_whitespace(&s);
637 if (i >= max_db || dbblock[i].dbptr == NULL) printf("Not open\n"); else
640 dbfn_close(dbblock + i);
642 dbblock[i].dbptr = NULL;
643 if (i == current) current = -1;
647 else if (Ustrncmp(cmd, "file", 4) == 0)
649 uschar * s = cmd + 4;
650 Uskip_whitespace(&s);
652 if (i >= max_db || dbblock[i].dbptr == NULL) printf("Not open\n");
656 else if (Ustrncmp(cmd, "time", 4) == 0)
658 showtime = ~showtime;
659 printf("Timing %s\n", showtime? "on" : "off");
662 else if (Ustrcmp(cmd, "q") == 0 || Ustrncmp(cmd, "quit", 4) == 0) break;
664 else if (Ustrncmp(cmd, "help", 4) == 0)
666 printf("close [<number>] close file [<number>]\n");
667 printf("delete <key> remove record from current file\n");
668 printf("file <number> make file <number> current\n");
669 printf("open <name> open db file\n");
670 printf("q[uit] exit program\n");
671 printf("read <key> read record from current file\n");
672 printf("scan scan current file\n");
673 printf("time time display on/off\n");
674 printf("write <key> <rest-of-line> write record to current file\n");
677 else printf("Eh?\n");
679 if (showtime && stop >= start)
680 printf("start=%d stop=%d difference=%d\n", (int)start, (int)stop,
681 (int)(stop - start));
686 for (i = 0; i < max_db; i++)
688 if (dbblock[i].dbptr != NULL)
690 printf("\nClosing %d", i);
691 dbfn_close(dbblock + i);