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 user ID of the calling process to UID.
      26     If the calling process is the super-user, the real
      27     and effective user IDs, and the saved set-user-ID to UID;
      28     if not, the effective user ID is set to UID.  */
      29  int
      30  __setuid (uid_t uid)
      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 UID as the real uid,
      43  	 and as the first element in the list of effective uids.  */
      44  
      45        uid_t *newgen, *newaux, auxbuf[2];
      46        size_t ngen, naux;
      47  
      48        newaux = _hurd_id.aux.uids;
      49        naux = _hurd_id.aux.nuids;
      50        if (_hurd_id.gen.nuids == 0)
      51  	{
      52  	  /* No effective uids now.  The new set will be just UID.  */
      53  	  newgen = &uid;
      54  	  ngen = 1;
      55  	}
      56        else if (_hurd_id.gen.uids[0] == 0)
      57  	{
      58  	  /* We are root; set the effective, real, and saved to UID.  */
      59  	  _hurd_id.gen.uids[0] = uid;
      60  	  _hurd_id.valid = 0;
      61  	  newgen = _hurd_id.gen.uids;
      62  	  ngen = _hurd_id.gen.nuids;
      63  	  if (_hurd_id.aux.nuids < 2)
      64  	    {
      65  	      newaux = auxbuf;
      66  	      naux = 2;
      67  	    }
      68  	  newaux[0] = newaux[1] = uid;
      69  	}
      70        else
      71  	{
      72  	  /* We are not root; just change the effective UID.  */
      73  	  /* XXX that implies an unprivileged setuid(0) will give
      74  	     the caller root, no questions asked! */
      75  	  _hurd_id.gen.uids[0] = uid;
      76  	  _hurd_id.valid = 0;
      77  	  newgen = _hurd_id.gen.uids;
      78  	  ngen = _hurd_id.gen.nuids;
      79  	}
      80  
      81        err = __USEPORT (AUTH, __auth_makeauth
      82  		       (port, NULL, MACH_MSG_TYPE_COPY_SEND, 0,
      83  			newgen, ngen, newaux, naux,
      84  			_hurd_id.gen.gids, _hurd_id.gen.ngids,
      85  			_hurd_id.aux.gids, _hurd_id.aux.ngids,
      86  			&newauth));
      87      }
      88    __mutex_unlock (&_hurd_id.lock);
      89    HURD_CRITICAL_END;
      90    if (err == EINTR)
      91      /* Got a signal while inside an RPC of the critical section, retry again */
      92      goto retry;
      93  
      94    if (err)
      95      return __hurd_fail (err);
      96  
      97    /* Install the new handle and reauthenticate everything.  */
      98    err = __setauth (newauth);
      99    __mach_port_deallocate (__mach_task_self (), newauth);
     100    return err;
     101  }
     102  
     103  weak_alias (__setuid, setuid)