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nsswitch.c

/* Copyright (C) 1996,1997,1998,1999,2001,2002 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <ctype.h>
#include <dlfcn.h>
#include <errno.h>
#include <netdb.h>
#include <bits/libc-lock.h>
#include <search.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>

#include <aliases.h>
#include <grp.h>
#include <netinet/ether.h>
#include <pwd.h>
#include <shadow.h>

#if !defined DO_STATIC_NSS || defined SHARED
# include <gnu/lib-names.h>
#endif

#include "nsswitch.h"

/* Prototypes for the local functions.  */
static name_database *nss_parse_file (const char *fname) internal_function;
static name_database_entry *nss_getline (char *line) internal_function;
static service_user *nss_parse_service_list (const char *line)
     internal_function;
static service_library *nss_new_service (name_database *database,
                               const char *name) internal_function;


/* Declare external database variables.  */
#define DEFINE_DATABASE(name)                                     \
  extern service_user *__nss_##name##_database attribute_hidden;        \
  weak_extern (__nss_##name##_database)
#include "databases.def"
#undef DEFINE_DATABASE

/* Structure to map database name to variable.  */
static struct
{
  const char *name;
  service_user **dbp;
} databases[] =
{
#define DEFINE_DATABASE(name)                                     \
  { #name, &__nss_##name##_database },
#include "databases.def"
#undef DEFINE_DATABASE
};


__libc_lock_define_initialized (static, lock)

#if !defined DO_STATIC_NSS || defined SHARED
/* String with revision number of the shared object files.  */
static const char *const __nss_shlib_revision = LIBNSS_FILES_SO + 15;
#endif

/* The root of the whole data base.  */
static name_database *service_table;


/* -1 == database not found
    0 == database entry pointer stored */
int
__nss_database_lookup (const char *database, const char *alternate_name,
                   const char *defconfig, service_user **ni)
{
  /* Prevent multiple threads to change the service table.  */
  __libc_lock_lock (lock);

  /* Reconsider database variable in case some other thread called
     `__nss_configure_lookup' while we waited for the lock.  */
  if (*ni != NULL)
    {
      __libc_lock_unlock (lock);
      return 0;
    }

  /* Are we initialized yet?  */
  if (service_table == NULL)
    /* Read config file.  */
    service_table = nss_parse_file (_PATH_NSSWITCH_CONF);

  /* Test whether configuration data is available.  */
  if (service_table != NULL)
    {
      /* Return first `service_user' entry for DATABASE.  */
      name_database_entry *entry;

      /* XXX Could use some faster mechanism here.  But each database is
       only requested once and so this might not be critical.  */
      for (entry = service_table->entry; entry != NULL; entry = entry->next)
      if (strcmp (database, entry->name) == 0)
        *ni = entry->service;

      if (*ni == NULL && alternate_name != NULL)
      /* We haven't found an entry so far.  Try to find it with the
         alternative name.  */
      for (entry = service_table->entry; entry != NULL; entry = entry->next)
        if (strcmp (alternate_name, entry->name) == 0)
          *ni = entry->service;
    }

  /* No configuration data is available, either because nsswitch.conf
     doesn't exist or because it doesn't has a line for this database.

     DEFCONFIG specifies the default service list for this database,
     or null to use the most common default.  */
  if (*ni == NULL)
    *ni = nss_parse_service_list (defconfig
                          ?: "nis [NOTFOUND=return] files");

  __libc_lock_unlock (lock);

  return 0;
}
libc_hidden_def (__nss_database_lookup)


/* -1 == not found
    0 == function found
    1 == finished */
int
__nss_lookup (service_user **ni, const char *fct_name, void **fctp)
{
  *fctp = __nss_lookup_function (*ni, fct_name);

  while (*fctp == NULL
       && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
       && (*ni)->next != NULL)
    {
      *ni = (*ni)->next;

      *fctp = __nss_lookup_function (*ni, fct_name);
    }

  return *fctp != NULL ? 0 : (*ni)->next == NULL ? 1 : -1;
}


/* -1 == not found
    0 == adjusted for next function
    1 == finished */
int
__nss_next (service_user **ni, const char *fct_name, void **fctp, int status,
          int all_values)
{
  if (all_values)
    {
      if (nss_next_action (*ni, NSS_STATUS_TRYAGAIN) == NSS_ACTION_RETURN
        && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_RETURN
        && nss_next_action (*ni, NSS_STATUS_NOTFOUND) == NSS_ACTION_RETURN
        && nss_next_action (*ni, NSS_STATUS_SUCCESS) == NSS_ACTION_RETURN)
      return 1;
    }
  else
    {
      /* This is really only for debugging.  */
       if (NSS_STATUS_TRYAGAIN > status || status > NSS_STATUS_RETURN)
       __libc_fatal ("illegal status in __nss_next");

       if (nss_next_action (*ni, status) == NSS_ACTION_RETURN)
       return 1;
    }

  if ((*ni)->next == NULL)
    return -1;

  do
    {
      *ni = (*ni)->next;

      *fctp = __nss_lookup_function (*ni, fct_name);
    }
  while (*fctp == NULL
       && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
       && (*ni)->next != NULL);

  return *fctp != NULL ? 0 : -1;
}
libc_hidden_def (__nss_next)


int
__nss_configure_lookup (const char *dbname, const char *service_line)
{
  service_user *new_db;
  size_t cnt;

  for (cnt = 0; cnt < sizeof databases; ++cnt)
    {
      int cmp = strcmp (dbname, databases[cnt].name);
      if (cmp == 0)
      break;
      if (cmp < 0)
      {
        __set_errno (EINVAL);
        return -1;
      }
    }

  if (cnt == sizeof databases)
    {
      __set_errno (EINVAL);
      return -1;
    }

  /* Test whether it is really used.  */
  if (databases[cnt].dbp == NULL)
    /* Nothing to do, but we could do.  */
    return 0;

  /* Try to generate new data.  */
  new_db = nss_parse_service_list (service_line);
  if (new_db == NULL)
    {
      /* Illegal service specification.  */
      __set_errno (EINVAL);
      return -1;
    }

  /* Prevent multiple threads to change the service table.  */
  __libc_lock_lock (lock);

  /* Install new rules.  */
  *databases[cnt].dbp = new_db;

  __libc_lock_unlock (lock);

  return 0;
}


/* Comparison function for searching NI->known tree.  */
static int
known_compare (const void *p1, const void *p2)
{
  return p1 == p2 ? 0 : strcmp (*(const char *const *) p1,
                        *(const char *const *) p2);
}


void *
__nss_lookup_function (service_user *ni, const char *fct_name)
{
  void **found, *result;

  /* We now modify global data.  Protect it.  */
  __libc_lock_lock (lock);

  /* Search the tree of functions previously requested.  Data in the
     tree are `known_function' structures, whose first member is a
     `const char *', the lookup key.  The search returns a pointer to
     the tree node structure; the first member of the is a pointer to
     our structure (i.e. what will be a `known_function'); since the
     first member of that is the lookup key string, &FCT_NAME is close
     enough to a pointer to our structure to use as a lookup key that
     will be passed to `known_compare' (above).  */

  found = __tsearch (&fct_name, (void **) &ni->known, &known_compare);
  if (*found != &fct_name)
    /* The search found an existing structure in the tree.  */
    result = ((known_function *) *found)->fct_ptr;
  else
    {
      /* This name was not known before.  Now we have a node in the tree
       (in the proper sorted position for FCT_NAME) that points to
       &FCT_NAME instead of any real `known_function' structure.
       Allocate a new structure and fill it in.  */

      known_function *known = malloc (sizeof *known);
      if (! known)
      {
      remove_from_tree:
        /* Oops.  We can't instantiate this node properly.
           Remove it from the tree.  */
        __tdelete (&fct_name, (void **) &ni->known, &known_compare);
        result = NULL;
      }
      else
      {
        /* Point the tree node at this new structure.  */
        *found = known;
        known->fct_name = fct_name;

        if (ni->library == NULL)
          {
            /* This service has not yet been used.  Fetch the service
             library for it, creating a new one if need be.  If there
             is no service table from the file, this static variable
             holds the head of the service_library list made from the
             default configuration.  */
            static name_database default_table;
            ni->library = nss_new_service (service_table ?: &default_table,
                                   ni->name);
            if (ni->library == NULL)
            {
              /* This only happens when out of memory.  */
              free (known);
              goto remove_from_tree;
            }
          }

#if !defined DO_STATIC_NSS || defined SHARED
        if (ni->library->lib_handle == NULL)
          {
            /* Load the shared library.  */
            size_t shlen = (7 + strlen (ni->library->name) + 3
                        + strlen (__nss_shlib_revision) + 1);
            int saved_errno = errno;
            char shlib_name[shlen];

            /* Construct shared object name.  */
            __stpcpy (__stpcpy (__stpcpy (__stpcpy (shlib_name,
                                          "libnss_"),
                                  ni->library->name),
                          ".so"),
                  __nss_shlib_revision);

            ni->library->lib_handle = __libc_dlopen (shlib_name);
            if (ni->library->lib_handle == NULL)
            {
              /* Failed to load the library.  */
              ni->library->lib_handle = (void *) -1l;
              __set_errno (saved_errno);
            }
          }

        if (ni->library->lib_handle == (void *) -1l)
          /* Library not found => function not found.  */
          result = NULL;
        else
          {
            /* Get the desired function.  */
            size_t namlen = (5 + strlen (ni->library->name) + 1
                         + strlen (fct_name) + 1);
            char name[namlen];

            /* Construct the function name.  */
            __stpcpy (__stpcpy (__stpcpy (__stpcpy (name, "_nss_"),
                                  ni->library->name),
                          "_"),
                  fct_name);

            /* Look up the symbol.  */
            result = __libc_dlsym (ni->library->lib_handle, name);
          }
#else
        /* We can't get function address dynamically in static linking. */
        {
# define DEFINE_ENT(h,nm)                                         \
          { #h"_get"#nm"ent_r", _nss_##h##_get##nm##ent_r },                  \
          { #h"_end"#nm"ent", _nss_##h##_end##nm##ent },                \
          { #h"_set"#nm"ent", _nss_##h##_set##nm##ent },
# define DEFINE_GET(h,nm)                                         \
          { #h"_get"#nm"_r", _nss_##h##_get##nm##_r },
# define DEFINE_GETBY(h,nm,ky)                                          \
          { #h"_get"#nm"by"#ky"_r", _nss_##h##_get##nm##by##ky##_r },
          static struct fct_tbl { const char *fname; void *fp; } *tp, tbl[] =
            {
# include "function.def"
            { NULL, NULL }
            };
          size_t namlen = (5 + strlen (ni->library->name) + 1
                       + strlen (fct_name) + 1);
          char name[namlen];

          /* Construct the function name.  */
          __stpcpy (__stpcpy (__stpcpy (name, ni->library->name),
                        "_"),
                  fct_name);

          result = NULL;
          for (tp = &tbl[0]; tp->fname; tp++)
            if (strcmp (tp->fname, name) == 0)
            {
              result = tp->fp;
              break;
            }
        }
#endif

        /* Remember function pointer for later calls.  Even if null, we
           record it so a second try needn't search the library again.  */
        known->fct_ptr = result;
      }
    }

  /* Remove the lock.  */
  __libc_lock_unlock (lock);

  return result;
}


static name_database *
internal_function
nss_parse_file (const char *fname)
{
  FILE *fp;
  name_database *result;
  name_database_entry *last;
  char *line;
  size_t len;

  /* Open the configuration file.  */
  fp = fopen (fname, "r");
  if (fp == NULL)
    return NULL;

  /* No threads use this stream.  */
  __fsetlocking (fp, FSETLOCKING_BYCALLER);

  result = (name_database *) malloc (sizeof (name_database));
  if (result == NULL)
    return NULL;

  result->entry = NULL;
  result->library = NULL;
  last = NULL;
  line = NULL;
  len = 0;
  do
    {
      name_database_entry *this;
      ssize_t n;

      n = __getline (&line, &len, fp);
      if (n < 0)
      break;
      if (line[n - 1] == '\n')
      line[n - 1] = '\0';

      /* Because the file format does not know any form of quoting we
       can search forward for the next '#' character and if found
       make it terminating the line.  */
      *__strchrnul (line, '#') = '\0';

      /* If the line is blank it is ignored.  */
      if (line[0] == '\0')
      continue;

      /* Each line completely specifies the actions for a database.  */
      this = nss_getline (line);
      if (this != NULL)
      {
        if (last != NULL)
          last->next = this;
        else
          result->entry = this;

        last = this;
      }
    }
  while (!feof_unlocked (fp));

  /* Free the buffer.  */
  free (line);
  /* Close configuration file.  */
  fclose (fp);

  return result;
}


/* Read the source names:
      `( <source> ( "[" "!"? (<status> "=" <action> )+ "]" )? )*'
   */
static service_user *
internal_function
nss_parse_service_list (const char *line)
{
  service_user *result = NULL, **nextp = &result;

  while (1)
    {
      service_user *new_service;
      const char *name;

      while (isspace (line[0]))
      ++line;
      if (line[0] == '\0')
      /* No source specified.  */
      return result;

      /* Read <source> identifier.  */
      name = line;
      while (line[0] != '\0' && !isspace (line[0]) && line[0] != '[')
      ++line;
      if (name == line)
      return result;


      new_service = (service_user *) malloc (sizeof (service_user)
                                   + (line - name + 1));
      if (new_service == NULL)
      return result;

      *((char *) __mempcpy (new_service->name, name, line - name)) = '\0';

      /* Set default actions.  */
      new_service->actions[2 + NSS_STATUS_TRYAGAIN] = NSS_ACTION_CONTINUE;
      new_service->actions[2 + NSS_STATUS_UNAVAIL] = NSS_ACTION_CONTINUE;
      new_service->actions[2 + NSS_STATUS_NOTFOUND] = NSS_ACTION_CONTINUE;
      new_service->actions[2 + NSS_STATUS_SUCCESS] = NSS_ACTION_RETURN;
      new_service->actions[2 + NSS_STATUS_RETURN] = NSS_ACTION_RETURN;
      new_service->library = NULL;
      new_service->known = NULL;
      new_service->next = NULL;

      while (isspace (line[0]))
      ++line;

      if (line[0] == '[')
      {
        /* Read criterions.  */
        do
          ++line;
        while (line[0] != '\0' && isspace (line[0]));

        do
          {
            int not;
            enum nss_status status;
            lookup_actions action;

            /* Grok ! before name to mean all statii but that one.  */
            not = line[0] == '!';
            if (not)
            ++line;

            /* Read status name.  */
            name = line;
            while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
                 && line[0] != ']')
            ++line;

            /* Compare with known statii.  */
            if (line - name == 7)
            {
              if (__strncasecmp (name, "SUCCESS", 7) == 0)
                status = NSS_STATUS_SUCCESS;
              else if (__strncasecmp (name, "UNAVAIL", 7) == 0)
                status = NSS_STATUS_UNAVAIL;
              else
                return result;
            }
            else if (line - name == 8)
            {
              if (__strncasecmp (name, "NOTFOUND", 8) == 0)
                status = NSS_STATUS_NOTFOUND;
              else if (__strncasecmp (name, "TRYAGAIN", 8) == 0)
                status = NSS_STATUS_TRYAGAIN;
              else
                return result;
            }
            else
            return result;

            while (isspace (line[0]))
            ++line;
            if (line[0] != '=')
            return result;
            do
            ++line;
            while (isspace (line[0]));

            name = line;
            while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
                 && line[0] != ']')
            ++line;

            if (line - name == 6 && __strncasecmp (name, "RETURN", 6) == 0)
            action = NSS_ACTION_RETURN;
            else if (line - name == 8
                   && __strncasecmp (name, "CONTINUE", 8) == 0)
            action = NSS_ACTION_CONTINUE;
            else
            return result;

            if (not)
            {
              /* Save the current action setting for this status,
                 set them all to the given action, and reset this one.  */
              const lookup_actions save = new_service->actions[2 + status];
              new_service->actions[2 + NSS_STATUS_TRYAGAIN] = action;
              new_service->actions[2 + NSS_STATUS_UNAVAIL] = action;
              new_service->actions[2 + NSS_STATUS_NOTFOUND] = action;
              new_service->actions[2 + NSS_STATUS_SUCCESS] = action;
              new_service->actions[2 + status] = save;
            }
            else
            new_service->actions[2 + status] = action;

            /* Skip white spaces.  */
            while (isspace (line[0]))
            ++line;
          }
        while (line[0] != ']');

        /* Skip the ']'.  */
        ++line;
      }

      *nextp = new_service;
      nextp = &new_service->next;
    }
}

static name_database_entry *
internal_function
nss_getline (char *line)
{
  const char *name;
  name_database_entry *result;
  size_t len;

  /* Ignore leading white spaces.  ATTENTION: this is different from
     what is implemented in Solaris.  The Solaris man page says a line
     beginning with a white space character is ignored.  We regard
     this as just another misfeature in Solaris.  */
  while (isspace (line[0]))
    ++line;

  /* Recognize `<database> ":"'.  */
  name = line;
  while (line[0] != '\0' && !isspace (line[0]) && line[0] != ':')
    ++line;
  if (line[0] == '\0' || name == line)
    /* Syntax error.  */
    return NULL;
  *line++ = '\0';

  len = strlen (name) + 1;

  result = (name_database_entry *) malloc (sizeof (name_database_entry) + len);
  if (result == NULL)
    return NULL;

  /* Save the database name.  */
  memcpy (result->name, name, len);

  /* Parse the list of services.  */
  result->service = nss_parse_service_list (line);

  result->next = NULL;
  return result;
}


static service_library *
internal_function
nss_new_service (name_database *database, const char *name)
{
  service_library **currentp = &database->library;

  while (*currentp != NULL)
    {
      if (strcmp ((*currentp)->name, name) == 0)
      return *currentp;
      currentp = &(*currentp)->next;
    }

  /* We have to add the new service.  */
  *currentp = (service_library *) malloc (sizeof (service_library));
  if (*currentp == NULL)
    return NULL;

  (*currentp)->name = name;
  (*currentp)->lib_handle = NULL;
  (*currentp)->next = NULL;

  return *currentp;
}


/* Free all resources if necessary.  */
libc_freeres_fn (free_mem)
{
  name_database *top = service_table;
  name_database_entry *entry;
  service_library *library;

  if (top == NULL)
    /* Maybe we have not read the nsswitch.conf file.  */
    return;

  /* Don't disturb ongoing other threads (if there are any).  */
  service_table = NULL;

  entry = top->entry;
  while (entry != NULL)
    {
      name_database_entry *olde = entry;
      service_user *service = entry->service;

      while (service != NULL)
      {
        service_user *olds = service;

        if (service->known != NULL)
          __tdestroy (service->known, free);

        service = service->next;
        free (olds);
      }

      entry = entry->next;
      free (olde);
    }

  library = top->library;
  while (library != NULL)
    {
      service_library *oldl = library;

      __libc_dlclose (library->lib_handle);

      library = library->next;
      free (oldl);
    }

  free (top);
}

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