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