source: vendor/3.5.2/source3/lib/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();
        (void)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) {
                (void)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(128, 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;
}