1  /* setresgid -- set real group ID, effective group ID, and saved-set group ID
       2     Copyright (C) 2002-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the 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     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <errno.h>
      20  #include <unistd.h>
      21  #include <hurd.h>
      22  #include <hurd/id.h>
      23  
      24  /* Set the real group ID, effective group ID, and saved-set group ID,
      25     of the calling process to RGID, EGID, and SGID, respectively.  */
      26  int
      27  __setresgid (gid_t rgid, gid_t egid, gid_t sgid)
      28  {
      29    auth_t newauth;
      30    error_t err;
      31  
      32  retry:
      33    HURD_CRITICAL_BEGIN;
      34    __mutex_lock (&_hurd_id.lock);
      35    err = _hurd_check_ids ();
      36  
      37    if (!err)
      38      {
      39        /* Make a new auth handle which has EGID as the first element in the
      40  	 list of effective gids.  */
      41  
      42        uid_t *newgen, *newaux;
      43        uid_t auxs[2] = { rgid, sgid };
      44        size_t ngen, naux;
      45  
      46        newgen = _hurd_id.gen.gids;
      47        ngen = _hurd_id.gen.ngids;
      48        if (egid != -1)
      49  	{
      50  	  if (_hurd_id.gen.ngids == 0)
      51  	    {
      52  	      /* No effective gids now.  The new set will be just UID.  */
      53  	      newgen = &egid;
      54  	      ngen = 1;
      55  	    }
      56  	  else
      57  	    {
      58  	      _hurd_id.gen.gids[0] = egid;
      59  	      _hurd_id.valid = 0;
      60  	    }
      61  	}
      62  
      63        newaux = _hurd_id.aux.gids;
      64        naux = _hurd_id.aux.ngids;
      65        if (rgid != -1)
      66  	{
      67  	  if (_hurd_id.aux.ngids == 0)
      68  	    {
      69  	      newaux = &rgid;
      70  	      naux = 1;
      71  	    }
      72  	  else
      73  	    {
      74  	      _hurd_id.aux.gids[0] = rgid;
      75  	      _hurd_id.valid = 0;
      76  	    }
      77  	}
      78  
      79        if (sgid != -1)
      80  	{
      81  	  if (rgid == -1)
      82  	    {
      83  	      if (_hurd_id.aux.ngids >= 1)
      84  		auxs[0] = _hurd_id.aux.gids[0];
      85  	      else if (_hurd_id.gen.ngids >= 1)
      86  		auxs[0] = _hurd_id.gen.gids[0];
      87  	      else
      88  		/* Not even an effective GID.
      89                     Fall back to the only GID we have. */
      90  		auxs[0] = sgid;
      91  	    }
      92  	  if (_hurd_id.aux.ngids <= 1)
      93  	    {
      94  	      /* No saved gids now.  The new set will be just UID.  */
      95  	      newaux = auxs;
      96  	      naux = 2;
      97  	    }
      98  	  else
      99  	    {
     100  	      _hurd_id.aux.gids[1] = sgid;
     101  	      _hurd_id.valid = 0;
     102  	    }
     103  	}
     104  
     105        err = __USEPORT (AUTH, __auth_makeauth
     106  		       (port, NULL, MACH_MSG_TYPE_COPY_SEND, 0,
     107  			_hurd_id.gen.uids, _hurd_id.gen.nuids,
     108  			_hurd_id.aux.uids, _hurd_id.aux.nuids,
     109  			newgen, ngen, newaux, naux,
     110  			&newauth));
     111      }
     112    __mutex_unlock (&_hurd_id.lock);
     113    HURD_CRITICAL_END;
     114    if (err == EINTR)
     115      /* Got a signal while inside an RPC of the critical section, retry again */
     116      goto retry;
     117  
     118    if (err)
     119      return __hurd_fail (err);
     120  
     121    /* Install the new handle and reauthenticate everything.  */
     122    err = __setauth (newauth);
     123    __mach_port_deallocate (__mach_task_self (), newauth);
     124    return err;
     125  }
     126  libc_hidden_def (__setresgid)
     127  weak_alias (__setresgid, setresgid)