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 static void *
 188 nss_lookup_function (service_user *ni, const char *fct_name)
 189 {
 190   /* Comparison function for searching NI->known tree.  */
 191   int known_compare (const void *p1, const void *p2)
 192     {
 193       return p1 == p2 ? 0 : strcmp (*(const char *const *) p1,
 194                                     *(const char *const *) p2);
 195     }
 196   void **found, *result;
 197
 198   /* We now modify global data.  Protect it.  */
 199   __libc_lock_lock (lock);
 200
 201   /* Search the tree of functions previously requested.  Data in the
 202      tree are `known_function' structures, whose first member is a
 203      `const char *', the lookup key.  The search returns a pointer to
 204      the tree node structure; the first member of the is a pointer to
 205      our structure (i.e. what will be a `known_function'); since the
 206      first member of that is the lookup key string, &FCT_NAME is close
 207      enough to a pointer to our structure to use as a lookup key that
 208      will be passed to `known_compare' (above).  */
 209
 210   found = __tsearch (&fct_name, (void **) &ni->known, &known_compare);
 211   if (*found != &fct_name)
 212     /* The search found an existing structure in the tree.  */
 213     result = ((known_function *) *found)->fct_ptr;
 214   else
 215     {
 216       /* This name was not known before.  Now we have a node in the tree
 217          (in the proper sorted position for FCT_NAME) that points to
 218          &FCT_NAME instead of any real `known_function' structure.
 219          Allocate a new structure and fill it in.  */
 220
 221       known_function *known = malloc (sizeof *known);
 222       if (! known)
 223         {
 224         remove_from_tree:
 225           /* Oops.  We can't instantiate this node properly.
 226              Remove it from the tree.  */
 227           __tdelete (&fct_name, (void **) &ni->known, &known_compare);
 228           result = NULL;
 229         }
 230       else
 231         {
 232           /* Point the tree node at this new structure.  */
 233           *found = known;
 234           known->fct_name = fct_name;
 235
 236           if (ni->library == NULL)
 237             {
 238               /* This service has not yet been used.  Fetch the service
 239                  library for it, creating a new one if need be.  If there
 240                  is no service table from the file, this static variable
 241                  holds the head of the service_library list made from the
 242                  default configuration.  */
 243               static name_database default_table;
 244               ni->library = nss_new_service (service_table ?: &default_table,
 245                                              ni->name);
 246               if (ni->library == NULL)
 247                 {
 248                   /* This only happens when out of memory.  */
 249                   free (known);
 250                   goto remove_from_tree;
 251                 }
 252             }
 253
 254           if (ni->library->lib_handle == NULL)
 255             {
 256               /* Load the shared library.  */
 257               size_t shlen = (7 + strlen (ni->library->name) + 3
 258                               + sizeof (NSS_SHLIB_REVISION));
 259               char shlib_name[shlen];
 260
 261               void do_open (void)
 262                 {
 263                   /* Open and relocate the shared object.  */
 264                   ni->library->lib_handle = _dl_open (shlib_name, RTLD_LAZY);
 265                 }
 266
 267               /* Construct shared object name.  */
 268               __stpcpy (__stpcpy (__stpcpy (shlib_name, "libnss_"),
 269                                   ni->library->name),
 270                         ".so" NSS_SHLIB_REVISION);
 271
 272               if (nss_dlerror_run (do_open) != 0)
 273                 /* Failed to load the library.  */
 274                 ni->library->lib_handle = (void *) -1;
 275             }
 276
 277           if (ni->library->lib_handle == (void *) -1)
 278             /* Library not found => function not found.  */
 279             result = NULL;
 280           else
 281             {
 282               /* Get the desired function.  Again,  GNU ld.so magic ahead.  */
 283               size_t namlen = (5 + strlen (ni->library->name) + 1
 284                                + strlen (fct_name) + 1);
 285               char name[namlen];
 286               struct link_map *map = ni->library->lib_handle;
 287               ElfW(Addr) loadbase;
 288               const ElfW(Sym) *ref = NULL;
 289               void get_sym (void)
 290                 {
 291                   struct link_map *scope[2] = { map, NULL };
 292                   loadbase = _dl_lookup_symbol (name, &ref,
 293                                                 scope, map->l_name, 0, 0);
 294                 }
 295
 296               /* Construct the function name.  */
 297               __stpcpy (__stpcpy (__stpcpy (__stpcpy (name, "_nss_"),
 298                                             ni->library->name),
 299                                   "_"),
 300                         fct_name);
 301
 302               /* Look up the symbol.  */
 303               result = (nss_dlerror_run (get_sym)
 304                         ? NULL : (void *) (loadbase + ref->st_value));
 305             }
 306
 307           /* Remember function pointer for later calls.  Even if null, we
 308              record it so a second try needn't search the library again.  */
 309           known->fct_ptr = result;
 310         }
 311     }
 312
 313   /* Remove the lock.  */
 314   __libc_lock_unlock (lock);
 315
 316   return result;
 317 }
 318
 319
 320 static name_database *
 321 nss_parse_file (const char *fname)
 322 {
 323   FILE *fp;
 324   name_database *result;
 325   name_database_entry *last;
 326   char *line;
 327   size_t len;
 328
 329   /* Open the configuration file.  */
 330   fp = fopen (fname, "r");
 331   if (fp == NULL)
 332     return NULL;
 333
 334   result = (name_database *) malloc (sizeof (name_database));
 335   if (result == NULL)
 336     return NULL;
 337
 338   result->entry = NULL;
 339   result->library = NULL;
 340   last = NULL;
 341   line = NULL;
 342   len = 0;
 343   do
 344     {
 345       name_database_entry *this;
 346       ssize_t n;
 347       char *cp;
 348
 349       n = __getline (&line, &len, fp);
 350       if (n < 0)
 351         break;
 352       if (line[n - 1] == '\n')
 353         line[n - 1] = '\0';
 354
 355       /* Because the file format does not know any form of quoting we
 356          can search forward for the next '#' character and if found
 357          make it terminating the line.  */
 358       cp = strchr (line, '#');
 359       if (cp != NULL)
 360         *cp = '\0';
 361
 362       /* If the line is blank it is ignored.  */
 363       if (line[0] == '\0')
 364         continue;
 365
 366       /* Each line completely specifies the actions for a database.  */
 367       this = nss_getline (line);
 368       if (this != NULL)
 369         {
 370           if (last != NULL)
 371             last->next = this;
 372           else
 373             result->entry = this;
 374
 375           last = this;
 376         }
 377     }
 378   while (!feof (fp));
 379
 380   /* Free the buffer.  */
 381   free (line);
 382   /* Close configuration file.  */
 383   fclose (fp);
 384
 385   return result;
 386 }
 387
 388
 389 /* Read the source names: `<source> ( "[" <status> "=" <action> "]" )*'.  */
 390 static service_user *
 391 nss_parse_service_list (const char *line)
 392 {
 393   service_user *result = NULL, **nextp = &result;
 394
 395   while (1)
 396     {
 397       service_user *new_service;
 398       const char *name;
 399
 400       while (isspace (line[0]))
 401         ++line;
 402       if (line[0] == '\0')
 403         /* No source specified.  */
 404         return result;
 405
 406       /* Read <source> identifier.  */
 407       name = line;
 408       while (line[0] != '\0' && !isspace (line[0]) && line[0] != '[')
 409         ++line;
 410       if (name == line)
 411         return result;
 412
 413
 414       new_service = (service_user *) malloc (sizeof (service_user));
 415       if (new_service == NULL)
 416         return result;
 417       else
 418         {
 419           char *source = (char *) malloc (line - name + 1);
 420           if (source == NULL)
 421             {
 422               free (new_service);
 423               return result;
 424             }
 425           memcpy (source, name, line - name);
 426           source[line - name] = '\0';
 427
 428           new_service->name = source;
 429         }
 430
 431       /* Set default actions.  */
 432       new_service->actions[2 + NSS_STATUS_TRYAGAIN] = NSS_ACTION_CONTINUE;
 433       new_service->actions[2 + NSS_STATUS_UNAVAIL] = NSS_ACTION_CONTINUE;
 434       new_service->actions[2 + NSS_STATUS_NOTFOUND] = NSS_ACTION_CONTINUE;
 435       new_service->actions[2 + NSS_STATUS_SUCCESS] = NSS_ACTION_RETURN;
 436       new_service->library = NULL;
 437       new_service->known = NULL;
 438       new_service->next = NULL;
 439
 440       while (isspace (line[0]))
 441         ++line;
 442
 443       if (line[0] == '[')
 444         {
 445           /* Read criterions.  */
 446           do
 447             ++line;
 448           while (line[0] != '\0' && isspace (line[0]));
 449
 450           do
 451             {
 452               int not;
 453               enum nss_status status;
 454               lookup_actions action;
 455
 456               /* Grok ! before name to mean all statii but that one.  */
 457               if (not = line[0] == '!')
 458                 ++line;
 459
 460               /* Read status name.  */
 461               name = line;
 462               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 463                      && line[0] != ']')
 464                 ++line;
 465
 466               /* Compare with known statii.  */
 467               if (line - name == 7)
 468                 {
 469                   if (__strncasecmp (name, "SUCCESS", 7) == 0)
 470                     status = NSS_STATUS_SUCCESS;
 471                   else if (__strncasecmp (name, "UNAVAIL", 7) == 0)
 472                     status = NSS_STATUS_UNAVAIL;
 473                   else
 474                     return result;
 475                 }
 476               else if (line - name == 8)
 477                 {
 478                   if (__strncasecmp (name, "NOTFOUND", 8) == 0)
 479                     status = NSS_STATUS_NOTFOUND;
 480                   else if (__strncasecmp (name, "TRYAGAIN", 8) == 0)
 481                     status = NSS_STATUS_TRYAGAIN;
 482                   else
 483                     return result;
 484                 }
 485               else
 486                 return result;
 487
 488               while (isspace (line[0]))
 489                 ++line;
 490               if (line[0] != '=')
 491                 return result;
 492               do
 493                 ++line;
 494               while (isspace (line[0]));
 495
 496               name = line;
 497               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 498                      && line[0] != ']')
 499                 ++line;
 500
 501               if (line - name == 6 && __strncasecmp (name, "RETURN", 6) == 0)
 502                 action = NSS_ACTION_RETURN;
 503               else if (line - name == 8
 504                        && __strncasecmp (name, "CONTINUE", 8) == 0)
 505                 action = NSS_ACTION_CONTINUE;
 506               else
 507                 return result;
 508
 509               if (not)
 510                 {
 511                   /* Save the current action setting for this status,
 512                      set them all to the given action, and reset this one.  */
 513                   const lookup_actions save = new_service->actions[2 + status];
 514                   new_service->actions[2 + NSS_STATUS_TRYAGAIN] = action;
 515                   new_service->actions[2 + NSS_STATUS_UNAVAIL] = action;
 516                   new_service->actions[2 + NSS_STATUS_NOTFOUND] = action;
 517                   new_service->actions[2 + NSS_STATUS_SUCCESS] = action;
 518                   new_service->actions[2 + status] = save;
 519                 }
 520               else
 521                 new_service->actions[2 + status] = action;
 522
 523               /* Skip white spaces.  */
 524               while (isspace (line[0]))
 525                 ++line;
 526             }
 527           while (line[0] != ']');
 528
 529           /* Skip the ']'.  */
 530           ++line;
 531         }
 532
 533       *nextp = new_service;
 534       nextp = &new_service->next;
 535     }
 536 }
 537
 538 static name_database_entry *
 539 nss_getline (char *line)
 540 {
 541   const char *name;
 542   name_database_entry *result;
 543
 544   /* Ignore leading white spaces.  ATTENTION: this is different from
 545      what is implemented in Solaris.  The Solaris man page says a line
 546      beginning with a white space character is ignored.  We regard
 547      this as just another misfeature in Solaris.  */
 548   while (isspace (line[0]))
 549     ++line;
 550
 551   /* Recognize `<database> ":"'.  */
 552   name = line;
 553   while (line[0] != '\0' && !isspace (line[0]) && line[0] != ':')
 554     ++line;
 555   if (line[0] == '\0' || name == line)
 556     /* Syntax error.  */
 557     return NULL;
 558   *line++ = '\0';
 559
 560   result = (name_database_entry *) malloc (sizeof (name_database_entry));
 561   if (result == NULL)
 562     return NULL;
 563
 564   /* Save the database name.  */
 565   {
 566     const size_t len = strlen (name) + 1;
 567     char *new = malloc (len);
 568     if (new == NULL)
 569       {
 570         free (result);
 571         return NULL;
 572       }
 573     result->name = memcpy (new, name, len);
 574   }
 575
 576   /* Parse the list of services.  */
 577   result->service = nss_parse_service_list (line);
 578
 579   result->next = NULL;
 580   return result;
 581 }
 582
 583
 584 static service_library *
 585 nss_new_service (name_database *database, const char *name)
 586 {
 587   service_library **currentp = &database->library;
 588
 589   while (*currentp != NULL)
 590     {
 591       if (strcmp ((*currentp)->name, name) == 0)
 592         return *currentp;
 593       currentp = &(*currentp)->next;
 594     }
 595
 596   /* We have to add the new service.  */
 597   *currentp = (service_library *) malloc (sizeof (service_library));
 598   if (*currentp == NULL)
 599     return NULL;
 600
 601   (*currentp)->name = name;
 602   (*currentp)->lib_handle = NULL;
 603   (*currentp)->next = NULL;
 604
 605   return *currentp;
 606 }