nss/nsswitch.c

   1 /* Copyright (C) 1996 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <ctype.h>
  21 #include <dlfcn.h>
  22 #include <errno.h>
  23 #include <netdb.h>
  24 #include <libc-lock.h>
  25 #include <link.h>       /* We need some help from ld.so.  */
  26 #include <search.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30
  31 #include "nsswitch.h"
  32
  33 /* Prototypes for the local functions.  */
  34 static void *nss_lookup_function (service_user *ni, const char *fct_name);
  35 static name_database *nss_parse_file (const char *fname);
  36 static name_database_entry *nss_getline (char *line);
  37 static service_user *nss_parse_service_list (const char *line);
  38 static service_library *nss_new_service (name_database *database,
  39                                          const char *name);
  40
  41
  42 /* Declare external database variables.  */
  43 #define DEFINE_DATABASE(name)                                                 \
  44   extern service_user *__nss_##name##_database;                               \
  45   weak_extern (__nss_##name##_database)
  46 #include "databases.def"
  47 #undef DEFINE_DATABASE
  48
  49 /* Structure to map database name to variable.  */
  50 static struct
  51 {
  52   const char *name;
  53   service_user **dbp;
  54 } databases[] =
  55 {
  56 #define DEFINE_DATABASE(name)                                                 \
  57   { #name, &__nss_##name##_database },
  58 #include "databases.def"
  59 #undef DEFINE_DATABASE
  60 };
  61
  62
  63 __libc_lock_define_initialized (static, lock)
  64
  65
  66 /* Nonzero if the sevices are already initialized.  */
  67 static int nss_initialized;
  68
  69
  70 /* The root of the whole data base.  */
  71 static name_database *service_table;
  72
  73
  74 /* -1 == database not found
  75     0 == database entry pointer stored */
  76 int
  77 __nss_database_lookup (const char *database, const char *alternate_name,
  78                        const char *defconfig, service_user **ni)
  79 {
  80   /* Prevent multiple threads to change the service table.  */
  81   __libc_lock_lock (lock);
  82
  83   /* Reconsider database variable in case some other thread called
  84      `__nss_configure_lookup' while we waited for the lock.  */
  85   if (*ni != NULL)
  86     {
  87       __libc_lock_unlock (lock);
  88       return 0;
  89     }
  90
  91   if (nss_initialized == 0 && service_table == NULL)
  92     /* Read config file.  */
  93     service_table = nss_parse_file (_PATH_NSSWITCH_CONF);
  94
  95   /* Test whether configuration data is available.  */
  96   if (service_table != NULL)
  97     {
  98       /* Return first `service_user' entry for DATABASE.  */
  99       name_database_entry *entry;
 100
 101       /* XXX Could use some faster mechanism here.  But each database is
 102          only requested once and so this might not be critical.  */
 103       for (entry = service_table->entry; entry != NULL; entry = entry->next)
 104         if (strcmp (database, entry->name) == 0)
 105           *ni = entry->service;
 106
 107       if (*ni == NULL && alternate_name != NULL)
 108         /* We haven't found a an entry so far.  Try to find it with
 109            the alternative name.  */
 110         for (entry = service_table->entry; entry != NULL; entry = entry->next)
 111           if (strcmp (alternate_name, entry->name) == 0)
 112             *ni = entry->service;
 113     }
 114
 115   /* No configuration data is available, either because nsswitch.conf
 116      doesn't exist or because it doesn't has a line for this database.
 117
 118      DEFCONFIG specifies the default service list for this database,
 119      or null to use the most common default.  */
 120   if (*ni == NULL)
 121     *ni = nss_parse_service_list (defconfig
 122                                   ?: "nis [NOTFOUND=return] files");
 123
 124   __libc_lock_unlock (lock);
 125
 126   return 0;
 127 }
 128
 129
 130 /* -1 == not found
 131     0 == adjusted for next function */
 132 int
 133 __nss_lookup (service_user **ni, const char *fct_name, void **fctp)
 134 {
 135   *fctp = nss_lookup_function (*ni, fct_name);
 136
 137   while (*fctp == NULL
 138          && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
 139          && (*ni)->next != NULL)
 140     {
 141       *ni = (*ni)->next;
 142
 143       *fctp = nss_lookup_function (*ni, fct_name);
 144     }
 145
 146   return *fctp != NULL ? 0 : -1;
 147 }
 148
 149
 150 /* -1 == not found
 151     0 == adjusted for next function
 152     1 == finished */
 153 int
 154 __nss_next (service_user **ni, const char *fct_name, void **fctp, int status,
 155             int all_values)
 156 {
 157   if (all_values)
 158     {
 159       if (nss_next_action (*ni, NSS_STATUS_TRYAGAIN) == NSS_ACTION_RETURN
 160           && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_RETURN
 161           && nss_next_action (*ni, NSS_STATUS_NOTFOUND) == NSS_ACTION_RETURN
 162           && nss_next_action (*ni, NSS_STATUS_SUCCESS) == NSS_ACTION_RETURN)
 163         return 1;
 164     }
 165   else
 166     {
 167       /* This is really only for debugging.  */
 168        if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 169          __libc_fatal ("illegal status in " __FUNCTION__);
 170
 171        if (nss_next_action (*ni, status) == NSS_ACTION_RETURN)
 172          return 1;
 173     }
 174
 175   if ((*ni)->next == NULL)
 176     return -1;
 177
 178   do
 179     {
 180       *ni = (*ni)->next;
 181
 182       *fctp = nss_lookup_function (*ni, fct_name);
 183     }
 184   while (*fctp == NULL
 185          && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
 186          && (*ni)->next != NULL);
 187
 188   return *fctp != NULL ? 0 : -1;
 189 }
 190
 191
 192 int
 193 __nss_configure_lookup (const char *dbname, const char *service_line)
 194 {
 195   service_user *new_db;
 196   size_t cnt;
 197
 198   for (cnt = 0; cnt < sizeof databases; ++cnt)
 199     {
 200       int cmp = strcmp (dbname, databases[cnt].name);
 201       if (cmp == 0)
 202         break;
 203       if (cmp > 0)
 204         {
 205           __set_errno (EINVAL);
 206           return -1;
 207         }
 208     }
 209
 210   if (cnt == sizeof databases)
 211     {
 212       __set_errno (EINVAL);
 213       return -1;
 214     }
 215
 216   /* Test whether it is really used.  */
 217   if (databases[cnt].dbp == NULL)
 218     /* Nothing to do, but we could do.  */
 219     return 0;
 220
 221   /* Try to generate new data.  */
 222   new_db = nss_parse_service_list (service_line);
 223   if (new_db == NULL)
 224     {
 225       /* Illegal service specification.  */
 226       __set_errno (EINVAL);
 227       return -1;
 228     }
 229
 230   /* Prevent multiple threads to change the service table.  */
 231   __libc_lock_lock (lock);
 232
 233   /* Install new rules.  */
 234   *databases[cnt].dbp = new_db;
 235
 236   __libc_lock_unlock (lock);
 237
 238   return 0;
 239 }
 240
 241
 242 static int
 243 nss_dlerror_run (void (*operate) (void))
 244 {
 245   char *last_errstring = NULL;
 246   const char *last_object_name = NULL;
 247   int result;
 248
 249   (void) _dl_catch_error (&last_errstring, &last_object_name, operate);
 250
 251   result = last_errstring != NULL;
 252   if (result)
 253     free (last_errstring);
 254
 255   return result;
 256 }
 257
 258
 259 /* Comparison function for searching NI->known tree.  */
 260 static int
 261 known_compare (const void *p1, const void *p2)
 262 {
 263   return p1 == p2 ? 0 : strcmp (*(const char *const *) p1,
 264                                 *(const char *const *) p2);
 265 }
 266
 267
 268 static void *
 269 nss_lookup_function (service_user *ni, const char *fct_name)
 270 {
 271   void **found, *result;
 272
 273   /* We now modify global data.  Protect it.  */
 274   __libc_lock_lock (lock);
 275
 276   /* Search the tree of functions previously requested.  Data in the
 277      tree are `known_function' structures, whose first member is a
 278      `const char *', the lookup key.  The search returns a pointer to
 279      the tree node structure; the first member of the is a pointer to
 280      our structure (i.e. what will be a `known_function'); since the
 281      first member of that is the lookup key string, &FCT_NAME is close
 282      enough to a pointer to our structure to use as a lookup key that
 283      will be passed to `known_compare' (above).  */
 284
 285   found = __tsearch (&fct_name, (void **) &ni->known, &known_compare);
 286   if (*found != &fct_name)
 287     /* The search found an existing structure in the tree.  */
 288     result = ((known_function *) *found)->fct_ptr;
 289   else
 290     {
 291       /* This name was not known before.  Now we have a node in the tree
 292          (in the proper sorted position for FCT_NAME) that points to
 293          &FCT_NAME instead of any real `known_function' structure.
 294          Allocate a new structure and fill it in.  */
 295
 296       known_function *known = malloc (sizeof *known);
 297       if (! known)
 298         {
 299         remove_from_tree:
 300           /* Oops.  We can't instantiate this node properly.
 301              Remove it from the tree.  */
 302           __tdelete (&fct_name, (void **) &ni->known, &known_compare);
 303           result = NULL;
 304         }
 305       else
 306         {
 307           /* Point the tree node at this new structure.  */
 308           *found = known;
 309           known->fct_name = fct_name;
 310
 311           if (ni->library == NULL)
 312             {
 313               /* This service has not yet been used.  Fetch the service
 314                  library for it, creating a new one if need be.  If there
 315                  is no service table from the file, this static variable
 316                  holds the head of the service_library list made from the
 317                  default configuration.  */
 318               static name_database default_table;
 319               ni->library = nss_new_service (service_table ?: &default_table,
 320                                              ni->name);
 321               if (ni->library == NULL)
 322                 {
 323                   /* This only happens when out of memory.  */
 324                   free (known);
 325                   goto remove_from_tree;
 326                 }
 327             }
 328
 329           if (ni->library->lib_handle == NULL)
 330             {
 331               /* Load the shared library.  */
 332               size_t shlen = (7 + strlen (ni->library->name) + 3
 333                               + sizeof (NSS_SHLIB_REVISION));
 334               char shlib_name[shlen];
 335
 336               void do_open (void)
 337                 {
 338                   /* Open and relocate the shared object.  */
 339                   ni->library->lib_handle = _dl_open (shlib_name, RTLD_LAZY);
 340                 }
 341
 342               /* Construct shared object name.  */
 343               __stpcpy (__stpcpy (__stpcpy (shlib_name, "libnss_"),
 344                                   ni->library->name),
 345                         ".so" NSS_SHLIB_REVISION);
 346
 347               if (nss_dlerror_run (do_open) != 0)
 348                 /* Failed to load the library.  */
 349                 ni->library->lib_handle = (void *) -1l;
 350             }
 351
 352           if (ni->library->lib_handle == (void *) -1l)
 353             /* Library not found => function not found.  */
 354             result = NULL;
 355           else
 356             {
 357               /* Get the desired function.  Again,  GNU ld.so magic ahead.  */
 358               size_t namlen = (5 + strlen (ni->library->name) + 1
 359                                + strlen (fct_name) + 1);
 360               char name[namlen];
 361               struct link_map *map = ni->library->lib_handle;
 362               ElfW(Addr) loadbase;
 363               const ElfW(Sym) *ref = NULL;
 364               void get_sym (void)
 365                 {
 366                   struct link_map *scope[2] = { map, NULL };
 367                   loadbase = _dl_lookup_symbol (name, &ref,
 368                                                 scope, map->l_name, 0);
 369                 }
 370
 371               /* Construct the function name.  */
 372               __stpcpy (__stpcpy (__stpcpy (__stpcpy (name, "_nss_"),
 373                                             ni->library->name),
 374                                   "_"),
 375                         fct_name);
 376
 377               /* Look up the symbol.  */
 378               result = (nss_dlerror_run (get_sym)
 379                         ? NULL : (void *) (loadbase + ref->st_value));
 380             }
 381
 382           /* Remember function pointer for later calls.  Even if null, we
 383              record it so a second try needn't search the library again.  */
 384           known->fct_ptr = result;
 385         }
 386     }
 387
 388   /* Remove the lock.  */
 389   __libc_lock_unlock (lock);
 390
 391   return result;
 392 }
 393
 394
 395 static name_database *
 396 nss_parse_file (const char *fname)
 397 {
 398   FILE *fp;
 399   name_database *result;
 400   name_database_entry *last;
 401   char *line;
 402   size_t len;
 403
 404   /* Open the configuration file.  */
 405   fp = fopen (fname, "r");
 406   if (fp == NULL)
 407     return NULL;
 408
 409   result = (name_database *) malloc (sizeof (name_database));
 410   if (result == NULL)
 411     return NULL;
 412
 413   result->entry = NULL;
 414   result->library = NULL;
 415   last = NULL;
 416   line = NULL;
 417   len = 0;
 418   do
 419     {
 420       name_database_entry *this;
 421       ssize_t n;
 422       char *cp;
 423
 424       n = __getline (&line, &len, fp);
 425       if (n < 0)
 426         break;
 427       if (line[n - 1] == '\n')
 428         line[n - 1] = '\0';
 429
 430       /* Because the file format does not know any form of quoting we
 431          can search forward for the next '#' character and if found
 432          make it terminating the line.  */
 433       cp = strchr (line, '#');
 434       if (cp != NULL)
 435         *cp = '\0';
 436
 437       /* If the line is blank it is ignored.  */
 438       if (line[0] == '\0')
 439         continue;
 440
 441       /* Each line completely specifies the actions for a database.  */
 442       this = nss_getline (line);
 443       if (this != NULL)
 444         {
 445           if (last != NULL)
 446             last->next = this;
 447           else
 448             result->entry = this;
 449
 450           last = this;
 451         }
 452     }
 453   while (!feof (fp));
 454
 455   /* Free the buffer.  */
 456   free (line);
 457   /* Close configuration file.  */
 458   fclose (fp);
 459
 460   return result;
 461 }
 462
 463
 464 /* Read the source names:
 465         `( <source> ( "[" "!"? (<status> "=" <action> )+ "]" )? )*'
 466    */
 467 static service_user *
 468 nss_parse_service_list (const char *line)
 469 {
 470   service_user *result = NULL, **nextp = &result;
 471
 472   while (1)
 473     {
 474       service_user *new_service;
 475       const char *name;
 476
 477       while (isspace (line[0]))
 478         ++line;
 479       if (line[0] == '\0')
 480         /* No source specified.  */
 481         return result;
 482
 483       /* Read <source> identifier.  */
 484       name = line;
 485       while (line[0] != '\0' && !isspace (line[0]) && line[0] != '[')
 486         ++line;
 487       if (name == line)
 488         return result;
 489
 490
 491       new_service = (service_user *) malloc (sizeof (service_user));
 492       if (new_service == NULL)
 493         return result;
 494       else
 495         {
 496           char *source = (char *) malloc (line - name + 1);
 497           if (source == NULL)
 498             {
 499               free (new_service);
 500               return result;
 501             }
 502           memcpy (source, name, line - name);
 503           source[line - name] = '\0';
 504
 505           new_service->name = source;
 506         }
 507
 508       /* Set default actions.  */
 509       new_service->actions[2 + NSS_STATUS_TRYAGAIN] = NSS_ACTION_CONTINUE;
 510       new_service->actions[2 + NSS_STATUS_UNAVAIL] = NSS_ACTION_CONTINUE;
 511       new_service->actions[2 + NSS_STATUS_NOTFOUND] = NSS_ACTION_CONTINUE;
 512       new_service->actions[2 + NSS_STATUS_SUCCESS] = NSS_ACTION_RETURN;
 513       new_service->actions[2 + NSS_STATUS_RETURN] = NSS_ACTION_RETURN;
 514       new_service->library = NULL;
 515       new_service->known = NULL;
 516       new_service->next = NULL;
 517
 518       while (isspace (line[0]))
 519         ++line;
 520
 521       if (line[0] == '[')
 522         {
 523           /* Read criterions.  */
 524           do
 525             ++line;
 526           while (line[0] != '\0' && isspace (line[0]));
 527
 528           do
 529             {
 530               int not;
 531               enum nss_status status;
 532               lookup_actions action;
 533
 534               /* Grok ! before name to mean all statii but that one.  */
 535               if (not = line[0] == '!')
 536                 ++line;
 537
 538               /* Read status name.  */
 539               name = line;
 540               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 541                      && line[0] != ']')
 542                 ++line;
 543
 544               /* Compare with known statii.  */
 545               if (line - name == 7)
 546                 {
 547                   if (__strncasecmp (name, "SUCCESS", 7) == 0)
 548                     status = NSS_STATUS_SUCCESS;
 549                   else if (__strncasecmp (name, "UNAVAIL", 7) == 0)
 550                     status = NSS_STATUS_UNAVAIL;
 551                   else
 552                     return result;
 553                 }
 554               else if (line - name == 8)
 555                 {
 556                   if (__strncasecmp (name, "NOTFOUND", 8) == 0)
 557                     status = NSS_STATUS_NOTFOUND;
 558                   else if (__strncasecmp (name, "TRYAGAIN", 8) == 0)
 559                     status = NSS_STATUS_TRYAGAIN;
 560                   else
 561                     return result;
 562                 }
 563               else
 564                 return result;
 565
 566               while (isspace (line[0]))
 567                 ++line;
 568               if (line[0] != '=')
 569                 return result;
 570               do
 571                 ++line;
 572               while (isspace (line[0]));
 573
 574               name = line;
 575               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 576                      && line[0] != ']')
 577                 ++line;
 578
 579               if (line - name == 6 && __strncasecmp (name, "RETURN", 6) == 0)
 580                 action = NSS_ACTION_RETURN;
 581               else if (line - name == 8
 582                        && __strncasecmp (name, "CONTINUE", 8) == 0)
 583                 action = NSS_ACTION_CONTINUE;
 584               else
 585                 return result;
 586
 587               if (not)
 588                 {
 589                   /* Save the current action setting for this status,
 590                      set them all to the given action, and reset this one.  */
 591                   const lookup_actions save = new_service->actions[2 + status];
 592                   new_service->actions[2 + NSS_STATUS_TRYAGAIN] = action;
 593                   new_service->actions[2 + NSS_STATUS_UNAVAIL] = action;
 594                   new_service->actions[2 + NSS_STATUS_NOTFOUND] = action;
 595                   new_service->actions[2 + NSS_STATUS_SUCCESS] = action;
 596                   new_service->actions[2 + status] = save;
 597                 }
 598               else
 599                 new_service->actions[2 + status] = action;
 600
 601               /* Skip white spaces.  */
 602               while (isspace (line[0]))
 603                 ++line;
 604             }
 605           while (line[0] != ']');
 606
 607           /* Skip the ']'.  */
 608           ++line;
 609         }
 610
 611       *nextp = new_service;
 612       nextp = &new_service->next;
 613     }
 614 }
 615
 616 static name_database_entry *
 617 nss_getline (char *line)
 618 {
 619   const char *name;
 620   name_database_entry *result;
 621
 622   /* Ignore leading white spaces.  ATTENTION: this is different from
 623      what is implemented in Solaris.  The Solaris man page says a line
 624      beginning with a white space character is ignored.  We regard
 625      this as just another misfeature in Solaris.  */
 626   while (isspace (line[0]))
 627     ++line;
 628
 629   /* Recognize `<database> ":"'.  */
 630   name = line;
 631   while (line[0] != '\0' && !isspace (line[0]) && line[0] != ':')
 632     ++line;
 633   if (line[0] == '\0' || name == line)
 634     /* Syntax error.  */
 635     return NULL;
 636   *line++ = '\0';
 637
 638   result = (name_database_entry *) malloc (sizeof (name_database_entry));
 639   if (result == NULL)
 640     return NULL;
 641
 642   /* Save the database name.  */
 643   {
 644     const size_t len = strlen (name) + 1;
 645     char *new = malloc (len);
 646     if (new == NULL)
 647       {
 648         free (result);
 649         return NULL;
 650       }
 651     result->name = memcpy (new, name, len);
 652   }
 653
 654   /* Parse the list of services.  */
 655   result->service = nss_parse_service_list (line);
 656
 657   result->next = NULL;
 658   return result;
 659 }
 660
 661
 662 static service_library *
 663 nss_new_service (name_database *database, const char *name)
 664 {
 665   service_library **currentp = &database->library;
 666
 667   while (*currentp != NULL)
 668     {
 669       if (strcmp ((*currentp)->name, name) == 0)
 670         return *currentp;
 671       currentp = &(*currentp)->next;
 672     }
 673
 674   /* We have to add the new service.  */
 675   *currentp = (service_library *) malloc (sizeof (service_library));
 676   if (*currentp == NULL)
 677     return NULL;
 678
 679   (*currentp)->name = name;
 680   (*currentp)->lib_handle = NULL;
 681   (*currentp)->next = NULL;
 682
 683   return *currentp;
 684 }