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system_smbd.c

/* 
   Unix SMB/CIFS implementation.
   system call wrapper interface.
   Copyright (C) Andrew Tridgell 2002
   Copyright (C) Andrew Barteltt 2002

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.
   
   This program 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 General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/* 
   This file may assume linkage with smbd - for things like become_root()
   etc. 
*/

#include "includes.h"

#ifndef HAVE_GETGROUPLIST

/*
  This is a *much* faster way of getting the list of groups for a user
  without changing the current supplementary group list. The old
  method used getgrent() which could take 20 minutes on a really big
  network with hundeds of thousands of groups and users. The new method
  takes a couple of seconds.

  NOTE!! this function only works if it is called as root!
  */

static int getgrouplist_internals(const char *user, gid_t gid, gid_t *groups,
                          int *grpcnt)
{
      gid_t *gids_saved;
      int ret, ngrp_saved, num_gids;

      if (non_root_mode()) {
            *grpcnt = 0;
            return 0;
      }

      /* work out how many groups we need to save */
      ngrp_saved = getgroups(0, NULL);
      if (ngrp_saved == -1) {
            /* this shouldn't happen */
            return -1;
      }

      gids_saved = SMB_MALLOC_ARRAY(gid_t, ngrp_saved+1);
      if (!gids_saved) {
            errno = ENOMEM;
            return -1;
      }

      ngrp_saved = getgroups(ngrp_saved, gids_saved);
      if (ngrp_saved == -1) {
            SAFE_FREE(gids_saved);
            /* very strange! */
            return -1;
      }

      if (initgroups(user, gid) != 0) {
            DEBUG(0, ("getgrouplist_internals: initgroups() failed!\n"));
            SAFE_FREE(gids_saved);
            return -1;
      }

      /* this must be done to cope with systems that put the current egid in the
         return from getgroups() */
      save_re_gid();
      set_effective_gid(gid);
      setgid(gid);

      num_gids = getgroups(0, NULL);
      if (num_gids == -1) {
            SAFE_FREE(gids_saved);
            /* very strange! */
            return -1;
      }

      if (num_gids + 1 > *grpcnt) {
            *grpcnt = num_gids + 1;
            ret = -1;
      } else {
            ret = getgroups(*grpcnt - 1, &groups[1]);
            if (ret < 0) {
                  SAFE_FREE(gids_saved);
                  /* very strange! */
                  return -1;
            }
            groups[0] = gid;
            *grpcnt = ret + 1;
      }

      restore_re_gid();

      if (sys_setgroups(gid, ngrp_saved, gids_saved) != 0) {
            /* yikes! */
            DEBUG(0,("ERROR: getgrouplist: failed to reset group list!\n"));
            smb_panic("getgrouplist: failed to reset group list!");
      }

      free(gids_saved);
      return ret;
}
#endif

static int sys_getgrouplist(const char *user, gid_t gid, gid_t *groups, int *grpcnt)
{
      int retval;
      bool winbind_env;

      DEBUG(10,("sys_getgrouplist: user [%s]\n", user));

      /* This is only ever called for Unix users, remote memberships are
       * always determined by the info3 coming back from auth3 or the
       * PAC. */
      winbind_env = winbind_env_set();
      winbind_off();

#ifdef HAVE_GETGROUPLIST
      retval = getgrouplist(user, gid, groups, grpcnt);
#else
      become_root();
      retval = getgrouplist_internals(user, gid, groups, grpcnt);
      unbecome_root();
#endif

      /* allow winbindd lookups, but only if they were not already disabled */
      if (!winbind_env) {
            winbind_on();
      }

      return retval;
}

bool getgroups_unix_user(TALLOC_CTX *mem_ctx, const char *user,
                   gid_t primary_gid,
                   gid_t **ret_groups, size_t *p_ngroups)
{
      size_t ngrp;
      int max_grp;
      gid_t *temp_groups;
      gid_t *groups;
      int i;

      max_grp = MIN(32, groups_max());
      temp_groups = SMB_MALLOC_ARRAY(gid_t, max_grp);
      if (! temp_groups) {
            return False;
      }

      if (sys_getgrouplist(user, primary_gid, temp_groups, &max_grp) == -1) {
            temp_groups = SMB_REALLOC_ARRAY(temp_groups, gid_t, max_grp);
            if (!temp_groups) {
                  return False;
            }
            
            if (sys_getgrouplist(user, primary_gid,
                             temp_groups, &max_grp) == -1) {
                  DEBUG(0, ("get_user_groups: failed to get the unix "
                          "group list\n"));
                  SAFE_FREE(temp_groups);
                  return False;
            }
      }
      
      ngrp = 0;
      groups = NULL;

      /* Add in primary group first */
      if (!add_gid_to_array_unique(mem_ctx, primary_gid, &groups, &ngrp)) {
            SAFE_FREE(temp_groups);
            return False;
      }

      for (i=0; i<max_grp; i++) {
            if (!add_gid_to_array_unique(mem_ctx, temp_groups[i],
                              &groups, &ngrp)) {
                  SAFE_FREE(temp_groups);
                  return False;
            }
      }

      *p_ngroups = ngrp;
      *ret_groups = groups;
      SAFE_FREE(temp_groups);
      return True;
}

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