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