nss/nsswitch.c

   1 /* Copyright (C) 1996, 1997, 1998 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 #include <gnu/lib-names.h>
  31
  32 #include "nsswitch.h"
  33
  34 /* Prototypes for the local functions.  */
  35 static void *nss_lookup_function (service_user *ni, const char *fct_name);
  36 static name_database *nss_parse_file (const char *fname);
  37 static name_database_entry *nss_getline (char *line);
  38 static service_user *nss_parse_service_list (const char *line);
  39 static service_library *nss_new_service (name_database *database,
  40                                          const char *name);
  41
  42
  43 /* Declare external database variables.  */
  44 #define DEFINE_DATABASE(name)                                                 \
  45   extern service_user *__nss_##name##_database;                               \
  46   weak_extern (__nss_##name##_database)
  47 #include "databases.def"
  48 #undef DEFINE_DATABASE
  49
  50 /* Structure to map database name to variable.  */
  51 static struct
  52 {
  53   const char *name;
  54   service_user **dbp;
  55 } databases[] =
  56 {
  57 #define DEFINE_DATABASE(name)                                                 \
  58   { #name, &__nss_##name##_database },
  59 #include "databases.def"
  60 #undef DEFINE_DATABASE
  61 };
  62
  63
  64 __libc_lock_define_initialized (static, lock)
  65
  66
  67 /* String with revision number of the shared object files.  */
  68 const char *const __nss_shlib_revision = LIBNSS_FILES_SO + 15;
  69
  70
  71 /* The root of the whole data base.  */
  72 static name_database *service_table;
  73
  74
  75 /* -1 == database not found
  76     0 == database entry pointer stored */
  77 int
  78 __nss_database_lookup (const char *database, const char *alternate_name,
  79                        const char *defconfig, service_user **ni)
  80 {
  81   /* Prevent multiple threads to change the service table.  */
  82   __libc_lock_lock (lock);
  83
  84   /* Reconsider database variable in case some other thread called
  85      `__nss_configure_lookup' while we waited for the lock.  */
  86   if (*ni != NULL)
  87     {
  88       __libc_lock_unlock (lock);
  89       return 0;
  90     }
  91
  92   /* Are we initialized yet?  */
  93   if (service_table == NULL)
  94     /* Read config file.  */
  95     service_table = nss_parse_file (_PATH_NSSWITCH_CONF);
  96
  97   /* Test whether configuration data is available.  */
  98   if (service_table != NULL)
  99     {
 100       /* Return first `service_user' entry for DATABASE.  */
 101       name_database_entry *entry;
 102
 103       /* XXX Could use some faster mechanism here.  But each database is
 104          only requested once and so this might not be critical.  */
 105       for (entry = service_table->entry; entry != NULL; entry = entry->next)
 106         if (strcmp (database, entry->name) == 0)
 107           *ni = entry->service;
 108
 109       if (*ni == NULL && alternate_name != NULL)
 110         /* We haven't found an entry so far.  Try to find it with
 111            the alternative name.  */
 112         for (entry = service_table->entry; entry != NULL; entry = entry->next)
 113           if (strcmp (alternate_name, entry->name) == 0)
 114             *ni = entry->service;
 115     }
 116
 117   /* No configuration data is available, either because nsswitch.conf
 118      doesn't exist or because it doesn't has a line for this database.
 119
 120      DEFCONFIG specifies the default service list for this database,
 121      or null to use the most common default.  */
 122   if (*ni == NULL)
 123     *ni = nss_parse_service_list (defconfig
 124                                   ?: "nis [NOTFOUND=return] files");
 125
 126   __libc_lock_unlock (lock);
 127
 128   return 0;
 129 }
 130
 131
 132 /* -1 == not found
 133     0 == adjusted for next function
 134     1 == finished */
 135 int
 136 __nss_lookup (service_user **ni, const char *fct_name, void **fctp)
 137 {
 138   *fctp = nss_lookup_function (*ni, fct_name);
 139
 140   while (*fctp == NULL
 141          && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
 142          && (*ni)->next != NULL)
 143     {
 144       *ni = (*ni)->next;
 145
 146       *fctp = nss_lookup_function (*ni, fct_name);
 147     }
 148
 149   return *fctp != NULL ? 0 : (*ni)->next == NULL ? 1 : -1;
 150 }
 151
 152
 153 /* -1 == not found
 154     0 == adjusted for next function
 155     1 == finished */
 156 int
 157 __nss_next (service_user **ni, const char *fct_name, void **fctp, int status,
 158             int all_values)
 159 {
 160   if (all_values)
 161     {
 162       if (nss_next_action (*ni, NSS_STATUS_TRYAGAIN) == NSS_ACTION_RETURN
 163           && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_RETURN
 164           && nss_next_action (*ni, NSS_STATUS_NOTFOUND) == NSS_ACTION_RETURN
 165           && nss_next_action (*ni, NSS_STATUS_SUCCESS) == NSS_ACTION_RETURN)
 166         return 1;
 167     }
 168   else
 169     {
 170       /* This is really only for debugging.  */
 171        if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
 172          __libc_fatal ("illegal status in " __FUNCTION__);
 173
 174        if (nss_next_action (*ni, status) == NSS_ACTION_RETURN)
 175          return 1;
 176     }
 177
 178   if ((*ni)->next == NULL)
 179     return -1;
 180
 181   do
 182     {
 183       *ni = (*ni)->next;
 184
 185       *fctp = nss_lookup_function (*ni, fct_name);
 186     }
 187   while (*fctp == NULL
 188          && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
 189          && (*ni)->next != NULL);
 190
 191   return *fctp != NULL ? 0 : -1;
 192 }
 193
 194
 195 int
 196 __nss_configure_lookup (const char *dbname, const char *service_line)
 197 {
 198   service_user *new_db;
 199   size_t cnt;
 200
 201   for (cnt = 0; cnt < sizeof databases; ++cnt)
 202     {
 203       int cmp = strcmp (dbname, databases[cnt].name);
 204       if (cmp == 0)
 205         break;
 206       if (cmp < 0)
 207         {
 208           __set_errno (EINVAL);
 209           return -1;
 210         }
 211     }
 212
 213   if (cnt == sizeof databases)
 214     {
 215       __set_errno (EINVAL);
 216       return -1;
 217     }
 218
 219   /* Test whether it is really used.  */
 220   if (databases[cnt].dbp == NULL)
 221     /* Nothing to do, but we could do.  */
 222     return 0;
 223
 224   /* Try to generate new data.  */
 225   new_db = nss_parse_service_list (service_line);
 226   if (new_db == NULL)
 227     {
 228       /* Illegal service specification.  */
 229       __set_errno (EINVAL);
 230       return -1;
 231     }
 232
 233   /* Prevent multiple threads to change the service table.  */
 234   __libc_lock_lock (lock);
 235
 236   /* Install new rules.  */
 237   *databases[cnt].dbp = new_db;
 238
 239   __libc_lock_unlock (lock);
 240
 241   return 0;
 242 }
 243
 244
 245 static int
 246 nss_dlerror_run (void (*operate) (void))
 247 {
 248   char *last_errstring = NULL;
 249   int result;
 250
 251   (void) _dl_catch_error (&last_errstring, operate);
 252
 253   result = last_errstring != NULL;
 254   if (result)
 255     free (last_errstring);
 256
 257   return result;
 258 }
 259
 260
 261 /* Comparison function for searching NI->known tree.  */
 262 static int
 263 known_compare (const void *p1, const void *p2)
 264 {
 265   return p1 == p2 ? 0 : strcmp (*(const char *const *) p1,
 266                                 *(const char *const *) p2);
 267 }
 268
 269
 270 static void *
 271 nss_lookup_function (service_user *ni, const char *fct_name)
 272 {
 273   void **found, *result;
 274
 275   /* We now modify global data.  Protect it.  */
 276   __libc_lock_lock (lock);
 277
 278   /* Search the tree of functions previously requested.  Data in the
 279      tree are `known_function' structures, whose first member is a
 280      `const char *', the lookup key.  The search returns a pointer to
 281      the tree node structure; the first member of the is a pointer to
 282      our structure (i.e. what will be a `known_function'); since the
 283      first member of that is the lookup key string, &FCT_NAME is close
 284      enough to a pointer to our structure to use as a lookup key that
 285      will be passed to `known_compare' (above).  */
 286
 287   found = __tsearch (&fct_name, (void **) &ni->known, &known_compare);
 288   if (*found != &fct_name)
 289     /* The search found an existing structure in the tree.  */
 290     result = ((known_function *) *found)->fct_ptr;
 291   else
 292     {
 293       /* This name was not known before.  Now we have a node in the tree
 294          (in the proper sorted position for FCT_NAME) that points to
 295          &FCT_NAME instead of any real `known_function' structure.
 296          Allocate a new structure and fill it in.  */
 297
 298       known_function *known = malloc (sizeof *known);
 299       if (! known)
 300         {
 301         remove_from_tree:
 302           /* Oops.  We can't instantiate this node properly.
 303              Remove it from the tree.  */
 304           __tdelete (&fct_name, (void **) &ni->known, &known_compare);
 305           result = NULL;
 306         }
 307       else
 308         {
 309           /* Point the tree node at this new structure.  */
 310           *found = known;
 311           known->fct_name = fct_name;
 312
 313           if (ni->library == NULL)
 314             {
 315               /* This service has not yet been used.  Fetch the service
 316                  library for it, creating a new one if need be.  If there
 317                  is no service table from the file, this static variable
 318                  holds the head of the service_library list made from the
 319                  default configuration.  */
 320               static name_database default_table;
 321               ni->library = nss_new_service (service_table ?: &default_table,
 322                                              ni->name);
 323               if (ni->library == NULL)
 324                 {
 325                   /* This only happens when out of memory.  */
 326                   free (known);
 327                   goto remove_from_tree;
 328                 }
 329             }
 330
 331           if (ni->library->lib_handle == NULL)
 332             {
 333               /* Load the shared library.  */
 334               size_t shlen = (7 + strlen (ni->library->name) + 3
 335                               + strlen (NSS_SHLIB_REVISION) + 1);
 336               char shlib_name[shlen];
 337
 338               void do_open (void)
 339                 {
 340                   /* Open and relocate the shared object.  */
 341                   ni->library->lib_handle = _dl_open (shlib_name, RTLD_LAZY);
 342                 }
 343
 344               /* Construct shared object name.  */
 345               __stpcpy (__stpcpy (__stpcpy (__stpcpy (shlib_name, "libnss_"),
 346                                             ni->library->name),
 347                                   ".so"),
 348                         NSS_SHLIB_REVISION);
 349
 350               if (nss_dlerror_run (do_open) != 0)
 351                 /* Failed to load the library.  */
 352                 ni->library->lib_handle = (void *) -1l;
 353             }
 354
 355           if (ni->library->lib_handle == (void *) -1l)
 356             /* Library not found => function not found.  */
 357             result = NULL;
 358           else
 359             {
 360               /* Get the desired function.  Again,  GNU ld.so magic ahead.  */
 361               size_t namlen = (5 + strlen (ni->library->name) + 1
 362                                + strlen (fct_name) + 1);
 363               char name[namlen];
 364               struct link_map *map = ni->library->lib_handle;
 365               ElfW(Addr) loadbase;
 366               const ElfW(Sym) *ref = NULL;
 367               void get_sym (void)
 368                 {
 369                   struct link_map *scope[2] = { map, NULL };
 370                   loadbase = _dl_lookup_symbol (name, &ref,
 371                                                 scope, map->l_name, 0);
 372                 }
 373
 374               /* Construct the function name.  */
 375               __stpcpy (__stpcpy (__stpcpy (__stpcpy (name, "_nss_"),
 376                                             ni->library->name),
 377                                   "_"),
 378                         fct_name);
 379
 380               /* Look up the symbol.  */
 381               result = (nss_dlerror_run (get_sym)
 382                         ? NULL : (void *) (loadbase + ref->st_value));
 383             }
 384
 385           /* Remember function pointer for later calls.  Even if null, we
 386              record it so a second try needn't search the library again.  */
 387           known->fct_ptr = result;
 388         }
 389     }
 390
 391   /* Remove the lock.  */
 392   __libc_lock_unlock (lock);
 393
 394   return result;
 395 }
 396
 397
 398 static name_database *
 399 nss_parse_file (const char *fname)
 400 {
 401   FILE *fp;
 402   name_database *result;
 403   name_database_entry *last;
 404   char *line;
 405   size_t len;
 406
 407   /* Open the configuration file.  */
 408   fp = fopen (fname, "r");
 409   if (fp == NULL)
 410     return NULL;
 411
 412   result = (name_database *) malloc (sizeof (name_database));
 413   if (result == NULL)
 414     return NULL;
 415
 416   result->entry = NULL;
 417   result->library = NULL;
 418   last = NULL;
 419   line = NULL;
 420   len = 0;
 421   do
 422     {
 423       name_database_entry *this;
 424       ssize_t n;
 425       char *cp;
 426
 427       n = __getline (&line, &len, fp);
 428       if (n < 0)
 429         break;
 430       if (line[n - 1] == '\n')
 431         line[n - 1] = '\0';
 432
 433       /* Because the file format does not know any form of quoting we
 434          can search forward for the next '#' character and if found
 435          make it terminating the line.  */
 436       cp = strchr (line, '#');
 437       if (cp != NULL)
 438         *cp = '\0';
 439
 440       /* If the line is blank it is ignored.  */
 441       if (line[0] == '\0')
 442         continue;
 443
 444       /* Each line completely specifies the actions for a database.  */
 445       this = nss_getline (line);
 446       if (this != NULL)
 447         {
 448           if (last != NULL)
 449             last->next = this;
 450           else
 451             result->entry = this;
 452
 453           last = this;
 454         }
 455     }
 456   while (!feof (fp));
 457
 458   /* Free the buffer.  */
 459   free (line);
 460   /* Close configuration file.  */
 461   fclose (fp);
 462
 463   return result;
 464 }
 465
 466
 467 /* Read the source names:
 468         `( <source> ( "[" "!"? (<status> "=" <action> )+ "]" )? )*'
 469    */
 470 static service_user *
 471 nss_parse_service_list (const char *line)
 472 {
 473   service_user *result = NULL, **nextp = &result;
 474
 475   while (1)
 476     {
 477       service_user *new_service;
 478       const char *name;
 479
 480       while (isspace (line[0]))
 481         ++line;
 482       if (line[0] == '\0')
 483         /* No source specified.  */
 484         return result;
 485
 486       /* Read <source> identifier.  */
 487       name = line;
 488       while (line[0] != '\0' && !isspace (line[0]) && line[0] != '[')
 489         ++line;
 490       if (name == line)
 491         return result;
 492
 493
 494       new_service = (service_user *) malloc (sizeof (service_user));
 495       if (new_service == NULL)
 496         return result;
 497       else
 498         {
 499           char *source = (char *) malloc (line - name + 1);
 500           if (source == NULL)
 501             {
 502               free (new_service);
 503               return result;
 504             }
 505           memcpy (source, name, line - name);
 506           source[line - name] = '\0';
 507
 508           new_service->name = source;
 509         }
 510
 511       /* Set default actions.  */
 512       new_service->actions[2 + NSS_STATUS_TRYAGAIN] = NSS_ACTION_CONTINUE;
 513       new_service->actions[2 + NSS_STATUS_UNAVAIL] = NSS_ACTION_CONTINUE;
 514       new_service->actions[2 + NSS_STATUS_NOTFOUND] = NSS_ACTION_CONTINUE;
 515       new_service->actions[2 + NSS_STATUS_SUCCESS] = NSS_ACTION_RETURN;
 516       new_service->actions[2 + NSS_STATUS_RETURN] = NSS_ACTION_RETURN;
 517       new_service->library = NULL;
 518       new_service->known = NULL;
 519       new_service->next = NULL;
 520
 521       while (isspace (line[0]))
 522         ++line;
 523
 524       if (line[0] == '[')
 525         {
 526           /* Read criterions.  */
 527           do
 528             ++line;
 529           while (line[0] != '\0' && isspace (line[0]));
 530
 531           do
 532             {
 533               int not;
 534               enum nss_status status;
 535               lookup_actions action;
 536
 537               /* Grok ! before name to mean all statii but that one.  */
 538               if (not = line[0] == '!')
 539                 ++line;
 540
 541               /* Read status name.  */
 542               name = line;
 543               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 544                      && line[0] != ']')
 545                 ++line;
 546
 547               /* Compare with known statii.  */
 548               if (line - name == 7)
 549                 {
 550                   if (__strncasecmp (name, "SUCCESS", 7) == 0)
 551                     status = NSS_STATUS_SUCCESS;
 552                   else if (__strncasecmp (name, "UNAVAIL", 7) == 0)
 553                     status = NSS_STATUS_UNAVAIL;
 554                   else
 555                     return result;
 556                 }
 557               else if (line - name == 8)
 558                 {
 559                   if (__strncasecmp (name, "NOTFOUND", 8) == 0)
 560                     status = NSS_STATUS_NOTFOUND;
 561                   else if (__strncasecmp (name, "TRYAGAIN", 8) == 0)
 562                     status = NSS_STATUS_TRYAGAIN;
 563                   else
 564                     return result;
 565                 }
 566               else
 567                 return result;
 568
 569               while (isspace (line[0]))
 570                 ++line;
 571               if (line[0] != '=')
 572                 return result;
 573               do
 574                 ++line;
 575               while (isspace (line[0]));
 576
 577               name = line;
 578               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 579                      && line[0] != ']')
 580                 ++line;
 581
 582               if (line - name == 6 && __strncasecmp (name, "RETURN", 6) == 0)
 583                 action = NSS_ACTION_RETURN;
 584               else if (line - name == 8
 585                        && __strncasecmp (name, "CONTINUE", 8) == 0)
 586                 action = NSS_ACTION_CONTINUE;
 587               else
 588                 return result;
 589
 590               if (not)
 591                 {
 592                   /* Save the current action setting for this status,
 593                      set them all to the given action, and reset this one.  */
 594                   const lookup_actions save = new_service->actions[2 + status];
 595                   new_service->actions[2 + NSS_STATUS_TRYAGAIN] = action;
 596                   new_service->actions[2 + NSS_STATUS_UNAVAIL] = action;
 597                   new_service->actions[2 + NSS_STATUS_NOTFOUND] = action;
 598                   new_service->actions[2 + NSS_STATUS_SUCCESS] = action;
 599                   new_service->actions[2 + status] = save;
 600                 }
 601               else
 602                 new_service->actions[2 + status] = action;
 603
 604               /* Skip white spaces.  */
 605               while (isspace (line[0]))
 606                 ++line;
 607             }
 608           while (line[0] != ']');
 609
 610           /* Skip the ']'.  */
 611           ++line;
 612         }
 613
 614       *nextp = new_service;
 615       nextp = &new_service->next;
 616     }
 617 }
 618
 619 static name_database_entry *
 620 nss_getline (char *line)
 621 {
 622   const char *name;
 623   name_database_entry *result;
 624
 625   /* Ignore leading white spaces.  ATTENTION: this is different from
 626      what is implemented in Solaris.  The Solaris man page says a line
 627      beginning with a white space character is ignored.  We regard
 628      this as just another misfeature in Solaris.  */
 629   while (isspace (line[0]))
 630     ++line;
 631
 632   /* Recognize `<database> ":"'.  */
 633   name = line;
 634   while (line[0] != '\0' && !isspace (line[0]) && line[0] != ':')
 635     ++line;
 636   if (line[0] == '\0' || name == line)
 637     /* Syntax error.  */
 638     return NULL;
 639   *line++ = '\0';
 640
 641   result = (name_database_entry *) malloc (sizeof (name_database_entry));
 642   if (result == NULL)
 643     return NULL;
 644
 645   /* Save the database name.  */
 646   {
 647     const size_t len = strlen (name) + 1;
 648     char *new = malloc (len);
 649     if (new == NULL)
 650       {
 651         free (result);
 652         return NULL;
 653       }
 654     result->name = memcpy (new, name, len);
 655   }
 656
 657   /* Parse the list of services.  */
 658   result->service = nss_parse_service_list (line);
 659
 660   result->next = NULL;
 661   return result;
 662 }
 663
 664
 665 static service_library *
 666 nss_new_service (name_database *database, const char *name)
 667 {
 668   service_library **currentp = &database->library;
 669
 670   while (*currentp != NULL)
 671     {
 672       if (strcmp ((*currentp)->name, name) == 0)
 673         return *currentp;
 674       currentp = &(*currentp)->next;
 675     }
 676
 677   /* We have to add the new service.  */
 678   *currentp = (service_library *) malloc (sizeof (service_library));
 679   if (*currentp == NULL)
 680     return NULL;
 681
 682   (*currentp)->name = name;
 683   (*currentp)->lib_handle = NULL;
 684   (*currentp)->next = NULL;
 685
 686   return *currentp;
 687 }