src/src/search.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2015 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* A set of functions to search databases in various formats. An open
   9 database is represented by a void * value which is returned from a lookup-
  10 specific "open" function. These are now all held in individual modules in the
  11 lookups subdirectory and the functions here form a generic interface.
  12
  13 Caching is used to improve performance. Open files are cached until a tidyup
  14 function is called, and for each file the result of the last lookup is cached.
  15 However, if too many files are opened, some of those that are not in use have
  16 to be closed. Those open items that use real files are kept on a LRU chain to
  17 help with this.
  18
  19 All the data is held in permanent store so as to be independent of the stacking
  20 pool that is reset from time to time. In fact, we use malloc'd store so that it
  21 can be freed when the caches are tidied up. It isn't actually clear whether
  22 this is a benefit or not, to be honest. */
  23
  24 #include "exim.h"
  25
  26
  27 /* Tree in which to cache open files until tidyup called. */
  28
  29 static tree_node *search_tree = NULL;
  30
  31 /* Two-way chain of open databases that use real files. This is maintained in
  32 recently-used order for the purposes of closing the least recently used when
  33 too many files are open. */
  34
  35 static tree_node *open_top = NULL;
  36 static tree_node *open_bot = NULL;
  37
  38 /* Count of open databases that use real files */
  39
  40 static int open_filecount = 0;
  41
  42 /* Allow us to reset store used for lookups and lookup caching */
  43
  44 static rmark search_reset_point = NULL;
  45
  46
  47
  48 /*************************************************
  49 *      Validate a plain lookup type name         *
  50 *************************************************/
  51
  52 /* Only those names that are recognized and whose code is included in the
  53 binary give an OK response. Use a binary chop search now that the list has got
  54 so long.
  55
  56 Arguments:
  57   name       lookup type name - not necessarily zero terminated (e.g. dbm*)
  58   len        length of the name
  59
  60 Returns:     +ve => valid lookup name; value is offset in lookup_list
  61              -ve => invalid name; message in search_error_message.
  62 */
  63
  64 int
  65 search_findtype(const uschar *name, int len)
  66 {
  67 int bot = 0;
  68 int top = lookup_list_count;
  69 while (top > bot)
  70   {
  71   int mid = (top + bot)/2;
  72   int c = Ustrncmp(name, lookup_list[mid]->name, len);
  73
  74   /* If c == 0 we have matched the incoming name with the start of the search
  75   type name. However, some search types are substrings of others (e.g. nis and
  76   nisplus) so we need to check that the lengths are the same. The length of the
  77   type name cannot be shorter (else c would not be 0); if it is not equal it
  78   must be longer, and in that case, the incoming name comes before the name we
  79   are testing. By leaving c == 0 when the lengths are different, and doing a
  80   > 0 test below, this all falls out correctly. */
  81
  82   if (c == 0 && Ustrlen(lookup_list[mid]->name) == len)
  83     {
  84     if (lookup_list[mid]->find != NULL) return mid;
  85     search_error_message  = string_sprintf("lookup type \"%.*s\" is not "
  86       "available (not in the binary - check buildtime LOOKUP configuration)",
  87       len, name);
  88     return -1;
  89     }
  90
  91   if (c > 0) bot = mid + 1; else top = mid;
  92   }
  93
  94 search_error_message = string_sprintf("unknown lookup type \"%.*s\"",len,name);
  95 return -1;
  96 }
  97
  98
  99
 100 /*************************************************
 101 *       Validate a full lookup type name         *
 102 *************************************************/
 103
 104 /* This function recognizes the "partial-" prefix and also terminating * and *@
 105 suffixes.
 106
 107 Arguments:
 108   name         the full lookup type name
 109   ptypeptr     where to put the partial type
 110                  after subtraction of 1024 or 2048:
 111                    negative     => no partial matching
 112                    non-negative => minimum number of non-wild components
 113   ptypeaff     where to put a pointer to the affix
 114                  the affix is within name if supplied therein
 115                  otherwise it's a literal string
 116   afflen       the length of the affix
 117   starflags    where to put the SEARCH_STAR and SEARCH_STARAT flags
 118
 119 Returns:     +ve => valid lookup name; value is offset in lookup_list
 120              -ve => invalid name; message in search_error_message.
 121 */
 122
 123 int
 124 search_findtype_partial(const uschar *name, int *ptypeptr, const uschar **ptypeaff,
 125   int *afflen, int *starflags)
 126 {
 127 int len, stype;
 128 int pv = -1;
 129 const uschar *ss = name;
 130
 131 *starflags = 0;
 132 *ptypeaff = NULL;
 133
 134 /* Check for a partial matching type. It must start with "partial", optionally
 135 followed by a sequence of digits. If this is followed by "-", the affix is the
 136 default "*." string. Otherwise we expect an affix in parentheses. Affixes are a
 137 limited number of characters, not including parens. */
 138
 139 if (Ustrncmp(name, "partial", 7) == 0)
 140   {
 141   ss += 7;
 142   if (isdigit (*ss))
 143     {
 144     pv = 0;
 145     while (isdigit(*ss)) pv = pv*10 + *ss++ - '0';
 146     }
 147   else pv = 2;         /* Default number of wild components */
 148
 149   if (*ss == '(')
 150     {
 151     *ptypeaff = ++ss;
 152     while (ispunct(*ss) && *ss != ')') ss++;
 153     if (*ss != ')') goto BAD_TYPE;
 154     *afflen = ss++ - *ptypeaff;
 155     }
 156   else if (*ss++ == '-')
 157     {
 158     *ptypeaff = US "*.";
 159     *afflen = 2;
 160     }
 161   else
 162     {
 163     BAD_TYPE:
 164     search_error_message = string_sprintf("format error in lookup type \"%s\"",
 165       name);
 166     return -1;
 167     }
 168   }
 169
 170 /* Now we are left with a lookup name, possibly followed by * or *@. */
 171
 172 len = Ustrlen(ss);
 173 if (len >= 2 && Ustrncmp(ss + len - 2, "*@", 2) == 0)
 174   {
 175   *starflags |= SEARCH_STARAT;
 176   len -= 2;
 177   }
 178 else if (len >= 1 && ss[len-1]  == '*')
 179   {
 180   *starflags |= SEARCH_STAR;
 181   len--;
 182   }
 183
 184 /* Check for the individual search type. Only those that are actually in the
 185 binary are valid. For query-style types, "partial" and default types are
 186 erroneous. */
 187
 188 stype = search_findtype(ss, len);
 189 if (stype >= 0 && mac_islookup(stype, lookup_querystyle))
 190   {
 191   if (pv >= 0)
 192     {
 193     search_error_message = string_sprintf("\"partial\" is not permitted "
 194       "for lookup type \"%s\"", ss);
 195     return -1;
 196     }
 197   if ((*starflags & (SEARCH_STAR|SEARCH_STARAT)) != 0)
 198     {
 199     search_error_message = string_sprintf("defaults using \"*\" or \"*@\" are "
 200       "not permitted for lookup type \"%s\"", ss);
 201     return -1;
 202     }
 203   }
 204
 205 *ptypeptr = pv;
 206 return stype;
 207 }
 208
 209
 210
 211 /*************************************************
 212 *               Release cached resources         *
 213 *************************************************/
 214
 215 /* When search_open is called it caches the "file" that it opens in
 216 search_tree. The name of the tree node is a concatenation of the search type
 217 with the file name. For query-style lookups, the file name is empty. Real files
 218 are normally closed only when this tidyup routine is called, typically at the
 219 end of sections of code where a number of lookups might occur. However, if too
 220 many files are open simultaneously, some get closed beforehand. They can't be
 221 removed from the tree. There is also a general tidyup function which is called
 222 for the lookup driver, if it exists.
 223
 224 First, there is an internal, recursive subroutine.
 225
 226 Argument:    a pointer to a search_openfile tree node
 227 Returns:     nothing
 228 */
 229
 230 static void
 231 tidyup_subtree(tree_node *t)
 232 {
 233 search_cache *c = (search_cache *)(t->data.ptr);
 234 if (t->left != NULL) tidyup_subtree(t->left);
 235 if (t->right != NULL) tidyup_subtree(t->right);
 236 if (c != NULL &&
 237     c->handle != NULL &&
 238     lookup_list[c->search_type]->close != NULL)
 239   lookup_list[c->search_type]->close(c->handle);
 240 }
 241
 242
 243 /* The external entry point
 244
 245 Argument: none
 246 Returns:  nothing
 247 */
 248
 249 void
 250 search_tidyup(void)
 251 {
 252 int old_pool = store_pool;
 253
 254 DEBUG(D_lookup) debug_printf_indent("search_tidyup called\n");
 255
 256 /* Close individually each cached open file. */
 257
 258 store_pool = POOL_SEARCH;
 259 if (search_tree)
 260   {
 261   tidyup_subtree(search_tree);
 262   search_tree = NULL;
 263   }
 264 open_top = open_bot = NULL;
 265 open_filecount = 0;
 266
 267 /* Call the general tidyup entry for any drivers that have one. */
 268
 269 for (int i = 0; i < lookup_list_count; i++) if (lookup_list[i]->tidy)
 270   (lookup_list[i]->tidy)();
 271
 272 if (search_reset_point) search_reset_point = store_reset(search_reset_point);
 273 store_pool = old_pool;
 274 }
 275
 276
 277
 278
 279 /*************************************************
 280 *             Open search database               *
 281 *************************************************/
 282
 283 /* A mode, and lists of owners and groups, are passed over for checking in
 284 the cases where the database is one or more files. Return NULL, with a message
 285 pointed to by message, in cases of error.
 286
 287 For search types that use a file or files, check up on the mode after
 288 opening. It is tempting to do a stat before opening the file, and use it as
 289 an existence check. However, doing that opens a small security loophole in
 290 that the status could be changed before the file is opened. Can't quite see
 291 what problems this might lead to, but you can't be too careful where security
 292 is concerned. Fstat() on an open file can normally be expected to succeed,
 293 but there are some NFS states where it does not.
 294
 295 There are two styles of query: (1) in the "single-key+file" style, a single
 296 key string and a file name are given, for example, for linear searches, DBM
 297 files, or for NIS. (2) In the "query" style, no "filename" is given; instead
 298 just a single query string is passed. This applies to multiple-key lookup
 299 types such as NIS+.
 300
 301 Before opening, scan the tree of cached files to see if this file is already
 302 open for the correct search type. If so, return the saved handle. If not, put
 303 the handle in the tree for possible subsequent use. See search_tidyup above for
 304 closing all the cached files.
 305
 306 A count of open databases which use real files is maintained, and if this
 307 gets too large, we have to close a cached file. Its entry remains in the tree,
 308 but is marked closed.
 309
 310 Arguments:
 311   filename       the name of the file for single-key+file style lookups,
 312                  NULL for query-style lookups
 313   search_type    the type of search required
 314   modemask       if a real single file is used, this specifies mode bits that
 315                  must not be set; otherwise it is ignored
 316   owners         if a real single file is used, this specifies the possible
 317                  owners of the file; otherwise it is ignored
 318   owngroups      if a real single file is used, this specifies the possible
 319                  group owners of the file; otherwise it is ignored
 320
 321 Returns:         an identifying handle for the open database;
 322                  this is the pointer to the tree block in the
 323                  cache of open files; return NULL on open failure, with
 324                  a message in search_error_message
 325 */
 326
 327 void *
 328 search_open(uschar *filename, int search_type, int modemask, uid_t *owners,
 329   gid_t *owngroups)
 330 {
 331 void *handle;
 332 tree_node *t;
 333 search_cache *c;
 334 lookup_info *lk = lookup_list[search_type];
 335 uschar keybuffer[256];
 336 int old_pool = store_pool;
 337
 338 if (filename && is_tainted(filename))
 339   {
 340   log_write(0, LOG_MAIN|LOG_PANIC,
 341     "Tainted filename for search: '%s'", filename);
 342   return NULL;
 343   }
 344
 345 /* Change to the search store pool and remember our reset point */
 346
 347 store_pool = POOL_SEARCH;
 348 if (!search_reset_point) search_reset_point = store_mark();
 349
 350 DEBUG(D_lookup) debug_printf_indent("search_open: %s \"%s\"\n", lk->name,
 351   filename ? filename : US"NULL");
 352
 353 /* See if we already have this open for this type of search, and if so,
 354 pass back the tree block as the handle. The key for the tree node is the search
 355 type plus '0' concatenated with the file name. There may be entries in the tree
 356 with closed files if a lot of files have been opened. */
 357
 358 sprintf(CS keybuffer, "%c%.254s", search_type + '0',
 359   filename ? filename : US"");
 360
 361 if ((t = tree_search(search_tree, keybuffer)))
 362   {
 363   if ((c = (search_cache *)t->data.ptr)->handle)
 364     {
 365     DEBUG(D_lookup) debug_printf_indent("  cached open\n");
 366     store_pool = old_pool;
 367     return t;
 368     }
 369   DEBUG(D_lookup) debug_printf_indent("  cached closed\n");
 370   }
 371
 372 /* Otherwise, we need to open the file or database - each search type has its
 373 own code, which is now split off into separately compiled modules. Before doing
 374 this, if the search type is one that uses real files, check on the number that
 375 we are holding open in the cache. If the limit is reached, close the least
 376 recently used one. */
 377
 378 if (lk->type == lookup_absfile && open_filecount >= lookup_open_max)
 379   if (!open_bot)
 380     log_write(0, LOG_MAIN|LOG_PANIC, "too many lookups open, but can't find "
 381       "one to close");
 382   else
 383     {
 384     search_cache *c = (search_cache *)(open_bot->data.ptr);
 385     DEBUG(D_lookup) debug_printf_indent("Too many lookup files open\n  closing %s\n",
 386       open_bot->name);
 387     if ((open_bot = c->up))
 388       ((search_cache *)(open_bot->data.ptr))->down = NULL;
 389     else
 390       open_top = NULL;
 391     ((lookup_list[c->search_type])->close)(c->handle);
 392     c->handle = NULL;
 393     open_filecount--;
 394     }
 395
 396 /* If opening is successful, call the file-checking function if there is one,
 397 and if all is still well, enter the open database into the tree. */
 398
 399 if (!(handle = (lk->open)(filename, &search_error_message)))
 400   {
 401   store_pool = old_pool;
 402   return NULL;
 403   }
 404
 405 if (  lk->check
 406    && !lk->check(handle, filename, modemask, owners, owngroups,
 407          &search_error_message))
 408   {
 409   lk->close(handle);
 410   store_pool = old_pool;
 411   return NULL;
 412   }
 413
 414 /* If this is a search type that uses real files, keep count. */
 415
 416 if (lk->type == lookup_absfile) open_filecount++;
 417
 418 /* If we found a previously opened entry in the tree, re-use it; otherwise
 419 insert a new entry. On re-use, leave any cached lookup data and the lookup
 420 count alone. */
 421
 422 if (!t)
 423   {
 424   t = store_get(sizeof(tree_node) + Ustrlen(keybuffer), FALSE);
 425   t->data.ptr = c = store_get(sizeof(search_cache), FALSE);
 426   c->item_cache = NULL;
 427   Ustrcpy(t->name, keybuffer);
 428   tree_insertnode(&search_tree, t);
 429   }
 430 else c = t->data.ptr;
 431
 432 c->handle = handle;
 433 c->search_type = search_type;
 434 c->up = c->down = NULL;
 435
 436 store_pool = old_pool;
 437 return t;
 438 }
 439
 440
 441
 442
 443
 444 /*************************************************
 445 *  Internal function: Find one item in database  *
 446 *************************************************/
 447
 448 /* The answer is always put into dynamic store. The last lookup for each handle
 449 is cached.
 450
 451 Arguments:
 452   handle       the handle from search_open; points to tree node
 453   filename     the filename that was handed to search_open, or
 454                NULL for query-style searches
 455   keystring    the keystring for single-key+file lookups, or
 456                the querystring for query-style lookups
 457
 458 Returns:       a pointer to a dynamic string containing the answer,
 459                or NULL if the query failed or was deferred; in the
 460                latter case, search_find_defer is set TRUE; after an unusual
 461                failure, there may be a message in search_error_message.
 462 */
 463
 464 static uschar *
 465 internal_search_find(void *handle, uschar *filename, uschar *keystring)
 466 {
 467 tree_node * t = (tree_node *)handle;
 468 search_cache * c = (search_cache *)(t->data.ptr);
 469 expiring_data * e = NULL;       /* compiler quietening */
 470 uschar * data = NULL;
 471 int search_type = t->name[0] - '0';
 472 int old_pool = store_pool;
 473
 474 /* Lookups that return DEFER may not always set an error message. So that
 475 the callers don't have to test for NULL, set an empty string. */
 476
 477 search_error_message = US"";
 478 f.search_find_defer = FALSE;
 479
 480 DEBUG(D_lookup) debug_printf_indent("internal_search_find: file=\"%s\"\n  "
 481   "type=%s key=\"%s\"\n", filename,
 482   lookup_list[search_type]->name, keystring);
 483
 484 /* Insurance. If the keystring is empty, just fail. */
 485
 486 if (keystring[0] == 0) return NULL;
 487
 488 /* Use the special store pool for search data */
 489
 490 store_pool = POOL_SEARCH;
 491
 492 /* Look up the data for the key, unless it is already in the cache for this
 493 file. No need to check c->item_cache for NULL, tree_search will do so. */
 494
 495 if (  (t = tree_search(c->item_cache, keystring))
 496    && (!(e = t->data.ptr)->expiry || e->expiry > time(NULL))
 497    )
 498   { /* Data was in the cache already; set the pointer from the tree node */
 499   data = e->data.ptr;
 500   DEBUG(D_lookup) debug_printf_indent("cached data used for lookup of %s%s%s\n",
 501     keystring,
 502     filename ? US"\n  in " : US"", filename ? filename : US"");
 503   }
 504 else
 505   {
 506   uint do_cache = UINT_MAX;
 507   int keylength = Ustrlen(keystring);
 508
 509   DEBUG(D_lookup)
 510     {
 511     if (t) debug_printf_indent("cached data found but past valid time; ");
 512     debug_printf_indent("%s lookup required for %s%s%s\n",
 513       filename ? US"file" : US"database",
 514       keystring,
 515       filename ? US"\n  in " : US"", filename ? filename : US"");
 516     }
 517
 518   /* Call the code for the different kinds of search. DEFER is handled
 519   like FAIL, except that search_find_defer is set so the caller can
 520   distinguish if necessary. */
 521
 522   if (lookup_list[search_type]->find(c->handle, filename, keystring, keylength,
 523       &data, &search_error_message, &do_cache) == DEFER)
 524     f.search_find_defer = TRUE;
 525
 526   /* A record that has been found is now in data, which is either NULL
 527   or points to a bit of dynamic store. Cache the result of the lookup if
 528   caching is permitted. Lookups can disable caching, when they did something
 529   that changes their data. The mysql and pgsql lookups do this when an
 530   UPDATE/INSERT query was executed. */
 531
 532   else if (do_cache)
 533     {
 534     int len = keylength + 1;
 535
 536     if (t)      /* Previous, out-of-date cache entry.  Update with the */
 537       {         /* new result and forget the old one */
 538       e->expiry = do_cache == UINT_MAX ? 0 : time(NULL)+do_cache;
 539       e->data.ptr = data;
 540       }
 541     else
 542       {
 543       e = store_get(sizeof(expiring_data) + sizeof(tree_node) + len, is_tainted(keystring));
 544       e->expiry = do_cache == UINT_MAX ? 0 : time(NULL)+do_cache;
 545       e->data.ptr = data;
 546       t = (tree_node *)(e+1);
 547       memcpy(t->name, keystring, len);
 548       t->data.ptr = e;
 549       tree_insertnode(&c->item_cache, t);
 550       }
 551     }
 552
 553   /* If caching was disabled, empty the cache tree. We just set the cache
 554   pointer to NULL here, because we cannot release the store at this stage. */
 555
 556   else
 557     {
 558     DEBUG(D_lookup) debug_printf_indent("lookup forced cache cleanup\n");
 559     c->item_cache = NULL;
 560     }
 561   }
 562
 563 DEBUG(D_lookup)
 564   {
 565   if (data)
 566     debug_printf_indent("lookup yielded: %s\n", data);
 567   else if (f.search_find_defer)
 568     debug_printf_indent("lookup deferred: %s\n", search_error_message);
 569   else debug_printf_indent("lookup failed\n");
 570   }
 571
 572 /* Return it in new dynamic store in the regular pool */
 573
 574 store_pool = old_pool;
 575 return data ? string_copy(data) : NULL;
 576 }
 577
 578
 579
 580
 581 /*************************************************
 582 * Find one item in database, possibly wildcarded *
 583 *************************************************/
 584
 585 /* This function calls the internal function above; once only if there
 586 is no partial matching, but repeatedly when partial matching is requested.
 587
 588 Arguments:
 589   handle         the handle from search_open
 590   filename       the filename that was handed to search_open, or
 591                    NULL for query-style searches
 592   keystring      the keystring for single-key+file lookups, or
 593                    the querystring for query-style lookups
 594   partial        -1 means no partial matching;
 595                    otherwise it's the minimum number of components;
 596   affix          the affix string for partial matching
 597   affixlen       the length of the affix string
 598   starflags      SEARCH_STAR and SEARCH_STARAT flags
 599   expand_setup   pointer to offset for setting up expansion strings;
 600                  don't do any if < 0
 601
 602 Returns:         a pointer to a dynamic string containing the answer,
 603                  or NULL if the query failed or was deferred; in the
 604                  latter case, search_find_defer is set TRUE
 605 */
 606
 607 uschar *
 608 search_find(void *handle, uschar *filename, uschar *keystring, int partial,
 609   const uschar *affix, int affixlen, int starflags, int *expand_setup)
 610 {
 611 tree_node *t = (tree_node *)handle;
 612 BOOL set_null_wild = FALSE;
 613 uschar *yield;
 614
 615 DEBUG(D_lookup)
 616   {
 617   if (partial < 0) affixlen = 99;   /* So that "NULL" prints */
 618   debug_printf_indent("search_find: file=\"%s\"\n  key=\"%s\" "
 619     "partial=%d affix=%.*s starflags=%x\n",
 620     (filename == NULL)? US"NULL" : filename,
 621     keystring, partial, affixlen, affix, starflags);
 622   }
 623
 624 /* Arrange to put this database at the top of the LRU chain if it is a type
 625 that opens real files. */
 626
 627 if (  open_top != (tree_node *)handle
 628    && lookup_list[t->name[0]-'0']->type == lookup_absfile)
 629   {
 630   search_cache *c = (search_cache *)(t->data.ptr);
 631   tree_node *up = c->up;
 632   tree_node *down = c->down;
 633
 634   /* Cut it out of the list. A newly opened file will a NULL up pointer.
 635   Otherwise there will be a non-NULL up pointer, since we checked above that
 636   this block isn't already at the top of the list. */
 637
 638   if (up)
 639     {
 640     ((search_cache *)(up->data.ptr))->down = down;
 641     if (down)
 642       ((search_cache *)(down->data.ptr))->up = up;
 643     else
 644       open_bot = up;
 645     }
 646
 647   /* Now put it at the head of the list. */
 648
 649   c->up = NULL;
 650   c->down = open_top;
 651   if (!open_top) open_bot = t;
 652   else ((search_cache *)(open_top->data.ptr))->up = t;
 653   open_top = t;
 654   }
 655
 656 DEBUG(D_lookup)
 657   {
 658   debug_printf_indent("LRU list:\n");
 659   for (tree_node *t = open_top; t; )
 660     {
 661     search_cache *c = (search_cache *)(t->data.ptr);
 662     debug_printf_indent("  %s\n", t->name);
 663     if (t == open_bot) debug_printf_indent("  End\n");
 664     t = c->down;
 665     }
 666   }
 667
 668 /* First of all, try to match the key string verbatim. If matched a complete
 669 entry but could have been partial, flag to set up variables. */
 670
 671 yield = internal_search_find(handle, filename, keystring);
 672 if (f.search_find_defer) return NULL;
 673
 674 if (yield) { if (partial >= 0) set_null_wild = TRUE; }
 675
 676 /* Not matched a complete entry; handle partial lookups, but only if the full
 677 search didn't defer. Don't use string_sprintf() to construct the initial key,
 678 just in case the original key is too long for the string_sprintf() buffer (it
 679 *has* happened!). The case of a zero-length affix has to be treated specially.
 680 */
 681
 682 else if (partial >= 0)
 683   {
 684   int len = Ustrlen(keystring);
 685   uschar *keystring2;
 686
 687   /* Try with the affix on the front, except for a zero-length affix */
 688
 689   if (affixlen == 0) keystring2 = keystring; else
 690     {
 691     keystring2 = store_get(len + affixlen + 1,
 692                         is_tainted(keystring) || is_tainted(affix));
 693     Ustrncpy(keystring2, affix, affixlen);
 694     Ustrcpy(keystring2 + affixlen, keystring);
 695     DEBUG(D_lookup) debug_printf_indent("trying partial match %s\n", keystring2);
 696     yield = internal_search_find(handle, filename, keystring2);
 697     if (f.search_find_defer) return NULL;
 698     }
 699
 700   /* The key in its entirety did not match a wild entry; try chopping off
 701   leading components. */
 702
 703   if (yield == NULL)
 704     {
 705     int dotcount = 0;
 706     uschar *keystring3 = keystring2 + affixlen;
 707     uschar *s = keystring3;
 708     while (*s != 0) if (*s++ == '.') dotcount++;
 709
 710     while (dotcount-- >= partial)
 711       {
 712       while (*keystring3 != 0 && *keystring3 != '.') keystring3++;
 713
 714       /* If we get right to the end of the string (which will be the last time
 715       through this loop), we've failed if the affix is null. Otherwise do one
 716       last lookup for the affix itself, but if it is longer than 1 character,
 717       remove the last character if it is ".". */
 718
 719       if (*keystring3 == 0)
 720         {
 721         if (affixlen < 1) break;
 722         if (affixlen > 1 && affix[affixlen-1] == '.') affixlen--;
 723         Ustrncpy(keystring2, affix, affixlen);
 724         keystring2[affixlen] = 0;
 725         keystring3 = keystring2;
 726         }
 727       else
 728         {
 729         keystring3 -= affixlen - 1;
 730         if (affixlen > 0) Ustrncpy(keystring3, affix, affixlen);
 731         }
 732
 733       DEBUG(D_lookup) debug_printf_indent("trying partial match %s\n", keystring3);
 734       yield = internal_search_find(handle, filename, keystring3);
 735       if (f.search_find_defer) return NULL;
 736       if (yield)
 737         {
 738         /* First variable is the wild part; second is the fixed part. Take care
 739         to get it right when keystring3 is just "*". */
 740
 741         if (expand_setup && *expand_setup >= 0)
 742           {
 743           int fixedlength = Ustrlen(keystring3) - affixlen;
 744           int wildlength = Ustrlen(keystring) - fixedlength - 1;
 745           *expand_setup += 1;
 746           expand_nstring[*expand_setup] = keystring;
 747           expand_nlength[*expand_setup] = wildlength;
 748           *expand_setup += 1;
 749           expand_nstring[*expand_setup] = keystring + wildlength + 1;
 750           expand_nlength[*expand_setup] = (fixedlength < 0)? 0 : fixedlength;
 751           }
 752         break;
 753         }
 754       keystring3 += affixlen;
 755       }
 756     }
 757
 758   else set_null_wild = TRUE; /* Matched a wild entry without any wild part */
 759   }
 760
 761 /* If nothing has been matched, but the option to look for "*@" is set, try
 762 replacing everything to the left of @ by *. After a match, the wild part
 763 is set to the string to the left of the @. */
 764
 765 if (!yield  &&  starflags & SEARCH_STARAT)
 766   {
 767   uschar *atat = Ustrrchr(keystring, '@');
 768   if (atat != NULL && atat > keystring)
 769     {
 770     int savechar;
 771     savechar = *(--atat);
 772     *atat = '*';
 773
 774     DEBUG(D_lookup) debug_printf_indent("trying default match %s\n", atat);
 775     yield = internal_search_find(handle, filename, atat);
 776     *atat = savechar;
 777     if (f.search_find_defer) return NULL;
 778
 779     if (yield && expand_setup && *expand_setup >= 0)
 780       {
 781       *expand_setup += 1;
 782       expand_nstring[*expand_setup] = keystring;
 783       expand_nlength[*expand_setup] = atat - keystring + 1;
 784       *expand_setup += 1;
 785       expand_nstring[*expand_setup] = keystring;
 786       expand_nlength[*expand_setup] = 0;
 787       }
 788     }
 789   }
 790
 791 /* If we still haven't matched anything, and the option to look for "*" is set,
 792 try that. If we do match, the first variable (the wild part) is the whole key,
 793 and the second is empty. */
 794
 795 if (!yield  &&  starflags & (SEARCH_STAR|SEARCH_STARAT))
 796   {
 797   DEBUG(D_lookup) debug_printf_indent("trying to match *\n");
 798   yield = internal_search_find(handle, filename, US"*");
 799   if (yield && expand_setup && *expand_setup >= 0)
 800     {
 801     *expand_setup += 1;
 802     expand_nstring[*expand_setup] = keystring;
 803     expand_nlength[*expand_setup] = Ustrlen(keystring);
 804     *expand_setup += 1;
 805     expand_nstring[*expand_setup] = keystring;
 806     expand_nlength[*expand_setup] = 0;
 807     }
 808   }
 809
 810 /* If this was a potentially partial lookup, and we matched either a
 811 complete non-wild domain entry, or we matched a wild-carded entry without
 812 chopping off any of the domain components, set up the expansion variables
 813 (if required) so that the first one is empty, and the second one is the
 814 fixed part of the domain. The set_null_wild flag is set only when yield is not
 815 NULL. */
 816
 817 if (set_null_wild && expand_setup && *expand_setup >= 0)
 818   {
 819   *expand_setup += 1;
 820   expand_nstring[*expand_setup] = keystring;
 821   expand_nlength[*expand_setup] = 0;
 822   *expand_setup += 1;
 823   expand_nstring[*expand_setup] = keystring;
 824   expand_nlength[*expand_setup] = Ustrlen(keystring);
 825   }
 826
 827 return yield;
 828 }
 829
 830 /* End of search.c */