mach/hurd/faccessat.c

/* Test for access to file, relative to open directory.  Hurd version.
   Copyright (C) 2006-2021 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <unistd.h>
#include <sys/types.h>
#include <hurd.h>
#include <hurd/fd.h>
#include <hurd/port.h>
#include <hurd/id.h>
#include <hurd/lookup.h>

static int
hurd_fail_seterrno (error_t err)
{
  return __hurd_fail (err);
}

static int
hurd_fail_noerrno (error_t err)
{
  return -1;
}

static int
__faccessat_common (int fd, const char *file, int type, int at_flags,
                    int (*errfunc) (error_t))
{
  error_t err;
  file_t rcrdir, rcwdir, io;
  int flags, allowed;

  if ((at_flags & AT_EACCESS) == AT_EACCESS)
    {
      /* Use effective permissions.  */
      io = __file_name_lookup_at (fd, at_flags &~ AT_EACCESS, file, 0, 0);
      if (io == MACH_PORT_NULL)
	return -1;
    }
  else
    {
      /* We have to use real permissions instead of the
         usual effective permissions.  */

      int hurd_flags = 0;
      err = __hurd_at_flags (&at_flags, &hurd_flags);
      if (err)
	return errfunc (err);

      error_t reauthenticate_cwdir_at (file_t *result)
	{
	  /* Get a port to the FD directory, authenticated with the real IDs.  */
	  error_t err;
	  mach_port_t ref;
	  ref = __mach_reply_port ();
	  err = HURD_DPORT_USE
	    (fd,
	     ({
	       err = __io_reauthenticate (port, ref, MACH_MSG_TYPE_MAKE_SEND);
	       if (!err)
		 err = __auth_user_authenticate (_hurd_id.rid_auth,
						 ref, MACH_MSG_TYPE_MAKE_SEND,
						 result);
	       err;
	     }));
	  __mach_port_destroy (__mach_task_self (), ref);
	  return err;
	}

      error_t reauthenticate (int which, file_t *result)
	{
	  /* Get a port to our root directory, authenticated with the real IDs.  */
	  error_t err;
	  mach_port_t ref;
	  ref = __mach_reply_port ();
	  err = HURD_PORT_USE
	    (&_hurd_ports[which],
	     ({
	       err = __io_reauthenticate (port, ref, MACH_MSG_TYPE_MAKE_SEND);
	       if (!err)
		 err = __auth_user_authenticate (_hurd_id.rid_auth,
						 ref, MACH_MSG_TYPE_MAKE_SEND,
						 result);
	       err;
	     }));
	  __mach_port_destroy (__mach_task_self (), ref);
	  return err;
	}

      error_t init_port (int which, error_t (*operate) (mach_port_t))
	{
	  switch (which)
	    {
	    case INIT_PORT_AUTH:
	      return (*operate) (_hurd_id.rid_auth);
	    case INIT_PORT_CRDIR:
	      return (reauthenticate (INIT_PORT_CRDIR, &rcrdir) ?:
		      (*operate) (rcrdir));
	    case INIT_PORT_CWDIR:
	      if (fd == AT_FDCWD || file[0] == '/')
		return (reauthenticate (INIT_PORT_CWDIR, &rcwdir) ?:
			(*operate) (rcwdir));
	      else
		return (reauthenticate_cwdir_at (&rcwdir) ?:
			(*operate) (rcwdir));
	    default:
	      return _hurd_ports_use (which, operate);
	    }
	}

      rcrdir = rcwdir = MACH_PORT_NULL;

     retry:
      HURD_CRITICAL_BEGIN;

      __mutex_lock (&_hurd_id.lock);
      /* Get _hurd_id up to date.  */
      if (err = _hurd_check_ids ())
	goto lose;

      if (_hurd_id.rid_auth == MACH_PORT_NULL)
	{
	  /* Set up _hurd_id.rid_auth.  This is a special auth server port
	     which uses the real uid and gid (the first aux uid and gid) as
	     the only effective uid and gid.  */

	  if (_hurd_id.aux.nuids < 1 || _hurd_id.aux.ngids < 1)
	    {
	      /* We do not have a real UID and GID.  Lose, lose, lose!  */
	      err = EGRATUITOUS;
	      goto lose;
	    }

	  /* Create a new auth port using our real UID and GID (the first
	     auxiliary UID and GID) as the only effective IDs.  */
	  if (err = __USEPORT (AUTH,
			       __auth_makeauth (port,
						NULL, MACH_MSG_TYPE_COPY_SEND, 0,
						_hurd_id.aux.uids, 1,
						_hurd_id.aux.uids,
						_hurd_id.aux.nuids,
						_hurd_id.aux.gids, 1,
						_hurd_id.aux.gids,
						_hurd_id.aux.ngids,
						&_hurd_id.rid_auth)))
	    goto lose;
	}

      if (!err)
	/* Look up the file name using the modified init ports.  */
	err = __hurd_file_name_lookup (&init_port, &__getdport, 0,
				       file, hurd_flags, 0, &io);

      /* We are done with _hurd_id.rid_auth now.  */
     lose:
      __mutex_unlock (&_hurd_id.lock);

      HURD_CRITICAL_END;
      if (err == EINTR)
	/* Got a signal while inside an RPC of the critical section, retry again */
	goto retry;

      if (rcrdir != MACH_PORT_NULL)
	__mach_port_deallocate (__mach_task_self (), rcrdir);
      if (rcwdir != MACH_PORT_NULL)
	__mach_port_deallocate (__mach_task_self (), rcwdir);
      if (err)
	return errfunc (err);
    }

  /* Find out what types of access we are allowed to this file.  */
  err = __file_check_access (io, &allowed);
  __mach_port_deallocate (__mach_task_self (), io);
  if (err)
    return errfunc (err);

  flags = 0;
  if (type & R_OK)
    flags |= O_READ;
  if (type & W_OK)
    flags |= O_WRITE;
  if (type & X_OK)
    flags |= O_EXEC;

  if (flags & ~allowed)
    /* We are not allowed all the requested types of access.  */
    return errfunc (EACCES);

  return 0;
}

int
__faccessat_noerrno (int fd, const char *file, int type, int at_flags)
{
  return __faccessat_common (fd, file, type, at_flags, hurd_fail_noerrno);
}

int
__faccessat (int fd, const char *file, int type, int at_flags)
{
  return __faccessat_common (fd, file, type, at_flags, hurd_fail_seterrno);
}
weak_alias (__faccessat, faccessat)