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