1  /* Copyright (C) 1991-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <errno.h>
      19  #include <unistd.h>
      20  #include <sys/types.h>
      21  #include <hurd.h>
      22  #include <hurd/id.h>
      23  #include <string.h>
      24  
      25  /* Set the group ID of the calling process to UID.
      26     If the calling process is the super-user, the real
      27     and effective group IDs, and the saved set-group-ID to UID;
      28     if not, the effective group ID is set to GID.  */
      29  int
      30  __setgid (gid_t gid)
      31  {
      32    auth_t newauth;
      33    error_t err;
      34  
      35  retry:
      36    HURD_CRITICAL_BEGIN;
      37    __mutex_lock (&_hurd_id.lock);
      38    err = _hurd_check_ids ();
      39  
      40    if (!err)
      41      {
      42        /* Make a new auth handle which has GID as the real gid,
      43  	 and as the first element in the list of effective gids.  */
      44  
      45        gid_t *newgen, *newaux, auxbuf[2];
      46        size_t ngen, naux;
      47  
      48        if (_hurd_id.gen.ngids == 0)
      49  	{
      50  	  /* No effective gids now.  The new set will be just GID.  */
      51  	  newgen = &gid;
      52  	  ngen = 1;
      53  	}
      54        else
      55  	{
      56  	  _hurd_id.gen.gids[0] = gid;
      57  	  _hurd_id.valid = 0;
      58  	  newgen = _hurd_id.gen.gids;
      59  	  ngen = _hurd_id.gen.ngids;
      60  	}
      61  
      62        newaux = _hurd_id.aux.gids;
      63        naux = _hurd_id.aux.ngids;
      64        if (_hurd_id.gen.nuids > 0 && _hurd_id.gen.uids[0] == 0)
      65  	{
      66  	  /* We are root; set the real and saved IDs too.  */
      67  	  _hurd_id.valid = 0;
      68  	  if (_hurd_id.aux.ngids < 2)
      69  	    {
      70  	      newaux = auxbuf;
      71  	      naux = 2;
      72  	    }
      73  	  newaux[0] = newaux[1] = gid;
      74  	}
      75  
      76        err = __USEPORT (AUTH, __auth_makeauth
      77  		       (port, NULL, MACH_MSG_TYPE_COPY_SEND, 0,
      78  			_hurd_id.gen.uids, _hurd_id.gen.nuids,
      79  			_hurd_id.aux.uids, _hurd_id.aux.nuids,
      80  			newgen, ngen, newaux, naux,
      81  			&newauth));
      82      }
      83    __mutex_unlock (&_hurd_id.lock);
      84    HURD_CRITICAL_END;
      85    if (err == EINTR)
      86      /* Got a signal while inside an RPC of the critical section, retry again */
      87      goto retry;
      88  
      89    if (err)
      90      return __hurd_fail (err);
      91  
      92    /* Install the new handle and reauthenticate everything.  */
      93    err = __setauth (newauth);
      94    __mach_port_deallocate (__mach_task_self (), newauth);
      95    return err;
      96  }
      97  
      98  weak_alias (__setgid, setgid)