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