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 int nss_find_entry (struct entry **knownp, const char *key,
  36                            void **valp);
  37 static void nss_insert_entry (struct entry **knownp, const char *key,
  38                               void *val);
  39 static name_database *nss_parse_file (const char *fname);
  40 static name_database_entry *nss_getline (char *line);
  41 static service_user *nss_parse_service_list (const char *line);
  42 static service_library *nss_new_service (name_database *database,
  43                                          const char *name);
  44
  45
  46 __libc_lock_define_initialized (static, lock);
  47
  48
  49 /* Global variable.  */
  50 struct __res_state _res;
  51
  52
  53 /* Nonzero if the sevices are already initialized.  */
  54 static int nss_initialized;
  55
  56
  57 /* The root of the whole data base.  */
  58 static name_database *service_table;
  59
  60
  61 static void
  62 nss_init (void)
  63 {
  64   /* Prevent multiple threads to change the service table.  */
  65   __libc_lock_lock (lock);
  66
  67   if (service_table == NULL)
  68     service_table = nss_parse_file (_PATH_NSSWITCH_CONF);
  69
  70   __libc_lock_unlock (lock);
  71 }
  72
  73
  74 /* -1 == database not found
  75     0 == database entry pointer stored */
  76 int
  77 __nss_database_lookup (const char *database, const char *defconfig,
  78                        service_user **ni)
  79 {
  80   name_database_entry *entry;
  81
  82   if (nss_initialized == 0)
  83     nss_init ();
  84
  85   /* Test whether configuration data is available.  */
  86   if (service_table)
  87     {
  88       /* Return first `service_user' entry for DATABASE.
  89          XXX Will use perfect hashing function for known databases.  */
  90
  91       /* XXX Could use some faster mechanism here.  But each database is
  92          only requested once and so this might not be critical.  */
  93       for (entry = service_table->entry; entry != NULL; entry = entry->next)
  94         if (strcmp (database, entry->name) == 0)
  95           {
  96             *ni = entry->service;
  97             return 0;
  98           }
  99     }
 100
 101   /* No configuration data is available, either because nsswitch.conf
 102      doesn't exist or because it doesn't have a line for this database.  */
 103   entry = malloc (sizeof *entry);
 104   if (entry == NULL)
 105     return -1;
 106   entry->name = database;
 107   /* DEFCONFIG specifies the default service list for this database,
 108      or null to use the most common default.  */
 109   entry->service = nss_parse_service_list (defconfig ?:
 110                                            "compat [NOTFOUND=return] files");
 111
 112   *ni = entry->service;
 113   return 0;
 114 }
 115
 116
 117 /* -1 == not found
 118     0 == adjusted for next function */
 119 int
 120 __nss_lookup (service_user **ni, const char *fct_name, void **fctp)
 121 {
 122   *fctp = nss_lookup_function (*ni, fct_name);
 123
 124   while (*fctp == NULL
 125          && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
 126          && (*ni)->next != NULL)
 127     {
 128       *ni = (*ni)->next;
 129
 130       *fctp = nss_lookup_function (*ni, fct_name);
 131     }
 132
 133   return *fctp != NULL ? 0 : -1;
 134 }
 135
 136
 137 /* -1 == not found
 138     0 == adjusted for next function
 139     1 == finished */
 140 int
 141 __nss_next (service_user **ni, const char *fct_name, void **fctp, int status,
 142             int all_values)
 143 {
 144   if (all_values)
 145     {
 146       if (nss_next_action (*ni, NSS_STATUS_TRYAGAIN) == NSS_ACTION_RETURN
 147           && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_RETURN
 148           && nss_next_action (*ni, NSS_STATUS_NOTFOUND) == NSS_ACTION_RETURN
 149           && nss_next_action (*ni, NSS_STATUS_SUCCESS) == NSS_ACTION_RETURN)
 150         return 1;
 151     }
 152   else
 153     {
 154       /* This is really only for debugging.  */
 155        if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_SUCCESS)
 156          __libc_fatal ("illegal status in " __FUNCTION__);
 157
 158        if (nss_next_action (*ni, status) == NSS_ACTION_RETURN)
 159          return 1;
 160     }
 161
 162   if ((*ni)->next == NULL)
 163     return -1;
 164
 165   do
 166     {
 167       *ni = (*ni)->next;
 168
 169       *fctp = nss_lookup_function (*ni, fct_name);
 170     }
 171   while (*fctp == NULL
 172          && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
 173          && (*ni)->next != NULL);
 174
 175   return *fctp != NULL ? 0 : -1;
 176 }
 177
 178
 179 static int
 180 nss_dlerror_run (void (*operate) (void))
 181 {
 182   const char *last_errstring = NULL;
 183   const char *last_object_name = NULL;
 184
 185   (void) _dl_catch_error (&last_errstring, &last_object_name, operate);
 186
 187   return last_errstring != NULL;
 188 }
 189
 190
 191 static void *
 192 nss_lookup_function (service_user *ni, const char *fct_name)
 193 {
 194   void *result;
 195
 196   /* Determine whether current function is loaded.  */
 197   if (nss_find_entry (&ni->known, fct_name, &result) >= 0)
 198     return result;
 199
 200   /* We now modify global data.  Protect it.  */
 201   __libc_lock_lock (lock);
 202
 203   if (ni->library == NULL)
 204     {
 205       /* This service has not yet been used.  Fetch the service library
 206          for it, creating a new one if need be.  If there is no service
 207          table from the file, this static variable holds the head of the
 208          service_library list made from the default configuration.  */
 209       static name_database default_table;
 210       ni->library = nss_new_service (service_table ?: &default_table,
 211                                      ni->name);
 212       if (ni->library == NULL)
 213         {
 214           /* This only happens when out of memory.  */
 215           __libc_lock_unlock (lock);
 216           return NULL;
 217         }
 218     }
 219
 220   if (ni->library->lib_handle == NULL)
 221     {
 222       /* Load the shared library.  */
 223       size_t shlen = (7 + strlen (ni->library->name) + 3
 224                       + sizeof (NSS_SHLIB_REVISION));
 225       char shlib_name[shlen];
 226
 227       void do_open (void)
 228         {
 229           /* Open and relocate the shared object.  */
 230           ni->library->lib_handle = _dl_open (shlib_name, RTLD_LAZY);
 231         }
 232
 233       /* Construct name.  */
 234       __stpcpy (__stpcpy (__stpcpy (shlib_name, "libnss_"), ni->library->name),
 235                 ".so" NSS_SHLIB_REVISION);
 236
 237       if (nss_dlerror_run (do_open) != 0)
 238         /* Failed to load the library.  */
 239         ni->library->lib_handle = (void *) -1;
 240     }
 241
 242   if (ni->library->lib_handle == (void *) -1)
 243     /* Library not found => function not found.  */
 244     result = NULL;
 245   else
 246     {
 247       /* Get the desired function.  Again,  GNU ld.so magic ahead.  */
 248       size_t namlen = (5 + strlen (ni->library->name) + 1
 249                        + strlen (fct_name) + 1);
 250       char name[namlen];
 251       struct link_map *map = ni->library->lib_handle;
 252       ElfW(Addr) loadbase;
 253       const ElfW(Sym) *ref = NULL;
 254       void get_sym (void)
 255         {
 256           struct link_map *scope[2] = { map, NULL };
 257           loadbase = _dl_lookup_symbol (name, &ref, scope, map->l_name, 0, 0);
 258         }
 259
 260       __stpcpy (__stpcpy (__stpcpy (__stpcpy (name, "_nss_"),
 261                                     ni->library->name),
 262                           "_"),
 263                 fct_name);
 264
 265       result = (nss_dlerror_run (get_sym)
 266                 ? NULL : (void *) (loadbase + ref->st_value));
 267     }
 268
 269   /* Remember function pointer for the usage.  */
 270   nss_insert_entry (&ni->known, fct_name, result);
 271
 272   /* Remove the lock.  */
 273   __libc_lock_unlock (lock);
 274
 275   return result;
 276 }
 277
 278
 279 static int
 280 known_compare (const void *p1, const void *p2)
 281 {
 282   known_function *v1 = (known_function *) p1;
 283   known_function *v2 = (known_function *) p2;
 284
 285   return strcmp (v1->fct_name, v2->fct_name);
 286 }
 287
 288
 289 static int
 290 nss_find_entry (struct entry **knownp, const char *key, void **valp)
 291 {
 292   known_function looking_for = { fct_name: key };
 293   struct entry **found;
 294
 295   found = __tfind (&looking_for, (const void **) knownp, known_compare);
 296
 297   if (found == NULL)
 298     return -1;
 299
 300   *valp = ((known_function *) (*found)->key)->fct_ptr;
 301
 302   return 0;
 303 }
 304
 305
 306 static void
 307 nss_insert_entry (struct entry **knownp, const char *key, void *val)
 308 {
 309   known_function *to_insert;
 310
 311   to_insert = (known_function *) malloc (sizeof (known_function));
 312   if (to_insert == NULL)
 313     return;
 314
 315   to_insert->fct_name = key;
 316   to_insert->fct_ptr = val;
 317
 318   __tsearch (to_insert, (void **) knownp, known_compare);
 319 }
 320
 321
 322 static name_database *
 323 nss_parse_file (const char *fname)
 324 {
 325   FILE *fp;
 326   name_database *result;
 327   name_database_entry *last;
 328   char *line;
 329   size_t len;
 330
 331   /* Open the configuration file.  */
 332   fp = fopen (fname, "r");
 333   if (fp == NULL)
 334     return NULL;
 335
 336   result = (name_database *) malloc (sizeof (name_database));
 337   if (result == NULL)
 338     return NULL;
 339
 340   result->entry = NULL;
 341   result->library = NULL;
 342   last = NULL;
 343   line = NULL;
 344   len = 0;
 345   do
 346     {
 347       name_database_entry *this;
 348       ssize_t n;
 349       char *cp;
 350
 351       n = __getline (&line, &len, fp);
 352       if (n < 0)
 353         break;
 354       if (line[n - 1] == '\n')
 355         line[n - 1] = '\0';
 356
 357       /* Because the file format does not know any form of quoting we
 358          can search forward for the next '#' character and if found
 359          make it terminating the line.  */
 360       cp = strchr (line, '#');
 361       if (cp != NULL)
 362         *cp = '\0';
 363
 364       /* If the line is blank it is ignored.  */
 365       if (line[0] == '\0')
 366         continue;
 367
 368       /* Each line completely specifies the actions for a database.  */
 369       this = nss_getline (line);
 370       if (this != NULL)
 371         {
 372           if (last != NULL)
 373             last->next = this;
 374           else
 375             result->entry = this;
 376
 377           last = this;
 378         }
 379     }
 380   while (!feof (fp));
 381
 382   /* Free the buffer.  */
 383   free (line);
 384   /* Close configuration file.  */
 385   fclose (fp);
 386
 387   return result;
 388 }
 389
 390
 391 /* Read the source names: `<source> ( "[" <status> "=" <action> "]" )*'.  */
 392 static service_user *
 393 nss_parse_service_list (const char *line)
 394 {
 395   service_user *result = NULL, **nextp = &result;
 396
 397   while (1)
 398     {
 399       service_user *new_service;
 400       const char *name;
 401
 402       while (isspace (line[0]))
 403         ++line;
 404       if (line[0] == '\0')
 405         /* No source specified.  */
 406         return result;
 407
 408       /* Read <source> identifier.  */
 409       name = line;
 410       while (line[0] != '\0' && !isspace (line[0]) && line[0] != '[')
 411         ++line;
 412       if (name == line)
 413         return result;
 414
 415
 416       new_service = (service_user *) malloc (sizeof (service_user));
 417       if (new_service == NULL)
 418         return result;
 419       else
 420         {
 421           char *source = (char *) malloc (line - name + 1);
 422           if (source == NULL)
 423             {
 424               free (new_service);
 425               return result;
 426             }
 427           memcpy (source, name, line - name);
 428           source[line - name] = '\0';
 429
 430           new_service->name = source;
 431         }
 432
 433       /* Set default actions.  */
 434       new_service->actions[2 + NSS_STATUS_TRYAGAIN] = NSS_ACTION_CONTINUE;
 435       new_service->actions[2 + NSS_STATUS_UNAVAIL] = NSS_ACTION_CONTINUE;
 436       new_service->actions[2 + NSS_STATUS_NOTFOUND] = NSS_ACTION_CONTINUE;
 437       new_service->actions[2 + NSS_STATUS_SUCCESS] = NSS_ACTION_RETURN;
 438       new_service->library = NULL;
 439       new_service->known = NULL;
 440       new_service->next = NULL;
 441
 442       while (isspace (line[0]))
 443         ++line;
 444
 445       if (line[0] == '[')
 446         {
 447           /* Read criterions.  */
 448           do
 449             ++line;
 450           while (line[0] != '\0' && isspace (line[0]));
 451
 452           do
 453             {
 454               int not;
 455               enum nss_status status;
 456               lookup_actions action;
 457
 458               /* Grok ! before name to mean all statii but that one.  */
 459               if (not = line[0] == '!')
 460                 ++line;
 461
 462               /* Read status name.  */
 463               name = line;
 464               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 465                      && line[0] != ']')
 466                 ++line;
 467
 468               /* Compare with known statii.  */
 469               if (line - name == 7)
 470                 {
 471                   if (__strncasecmp (name, "SUCCESS", 7) == 0)
 472                     status = NSS_STATUS_SUCCESS;
 473                   else if (__strncasecmp (name, "UNAVAIL", 7) == 0)
 474                     status = NSS_STATUS_UNAVAIL;
 475                   else
 476                     return result;
 477                 }
 478               else if (line - name == 8)
 479                 {
 480                   if (__strncasecmp (name, "NOTFOUND", 8) == 0)
 481                     status = NSS_STATUS_NOTFOUND;
 482                   else if (__strncasecmp (name, "TRYAGAIN", 8) == 0)
 483                     status = NSS_STATUS_TRYAGAIN;
 484                   else
 485                     return result;
 486                 }
 487               else
 488                 return result;
 489
 490               while (isspace (line[0]))
 491                 ++line;
 492               if (line[0] != '=')
 493                 return result;
 494               do
 495                 ++line;
 496               while (isspace (line[0]));
 497
 498               name = line;
 499               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 500                      && line[0] != ']')
 501                 ++line;
 502
 503               if (line - name == 6 && __strncasecmp (name, "RETURN", 6) == 0)
 504                 action = NSS_ACTION_RETURN;
 505               else if (line - name == 8
 506                        && __strncasecmp (name, "CONTINUE", 8) == 0)
 507                 action = NSS_ACTION_CONTINUE;
 508               else
 509                 return result;
 510
 511               if (not)
 512                 {
 513                   /* Save the current action setting for this status,
 514                      set them all to the given action, and reset this one.  */
 515                   const lookup_actions save = new_service->actions[2 + status];
 516                   new_service->actions[2 + NSS_STATUS_TRYAGAIN] = action;
 517                   new_service->actions[2 + NSS_STATUS_UNAVAIL] = action;
 518                   new_service->actions[2 + NSS_STATUS_NOTFOUND] = action;
 519                   new_service->actions[2 + NSS_STATUS_SUCCESS] = action;
 520                   new_service->actions[2 + status] = save;
 521                 }
 522               else
 523                 new_service->actions[2 + status] = action;
 524
 525               /* Skip white spaces.  */
 526               while (isspace (line[0]))
 527                 ++line;
 528             }
 529           while (line[0] != ']');
 530
 531           /* Skip the ']'.  */
 532           ++line;
 533         }
 534
 535       *nextp = new_service;
 536       nextp = &new_service->next;
 537     }
 538 }
 539
 540 static name_database_entry *
 541 nss_getline (char *line)
 542 {
 543   const char *name;
 544   name_database_entry *result;
 545
 546   /* Ignore leading white spaces.  ATTENTION: this is different from
 547      what is implemented in Solaris.  The Solaris man page says a line
 548      beginning with a white space character is ignored.  We regard
 549      this as just another misfeature in Solaris.  */
 550   while (isspace (line[0]))
 551     ++line;
 552
 553   /* Recognize `<database> ":"'.  */
 554   name = line;
 555   while (line[0] != '\0' && !isspace (line[0]) && line[0] != ':')
 556     ++line;
 557   if (line[0] == '\0' || name == line)
 558     /* Syntax error.  */
 559     return NULL;
 560   *line++ = '\0';
 561
 562   result = (name_database_entry *) malloc (sizeof (name_database_entry));
 563   if (result == NULL)
 564     return NULL;
 565
 566   /* Save the database name.  */
 567   {
 568     const size_t len = strlen (name) + 1;
 569     char *new = malloc (len);
 570     if (new == NULL)
 571       {
 572         free (result);
 573         return NULL;
 574       }
 575     result->name = memcpy (new, name, len);
 576   }
 577
 578   /* Parse the list of services.  */
 579   result->service = nss_parse_service_list (line);
 580
 581   result->next = NULL;
 582   return result;
 583 }
 584
 585
 586 static service_library *
 587 nss_new_service (name_database *database, const char *name)
 588 {
 589   service_library **currentp = &database->library;
 590
 591   while (*currentp != NULL)
 592     {
 593       if (strcmp ((*currentp)->name, name) == 0)
 594         return *currentp;
 595       currentp = &(*currentp)->next;
 596     }
 597
 598   /* We have to add the new service.  */
 599   *currentp = (service_library *) malloc (sizeof (service_library));
 600   if (*currentp == NULL)
 601     return NULL;
 602
 603   (*currentp)->name = name;
 604   (*currentp)->lib_handle = NULL;
 605   (*currentp)->next = NULL;
 606
 607   return *currentp;
 608 }