path: root/libdiskfs/file-exec.c

/*
   Copyright (C) 1993, 1994, 1995 Free Software Foundation

This file is part of the GNU Hurd.

The GNU Hurd 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 2, or (at your option)
any later version.

The GNU Hurd 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 the GNU Hurd; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* Written by Michael I. Bushnell.  */

#include "priv.h"
#include "fs_S.h"
#include <sys/stat.h>
#include <fcntlbits.h>
#include <hurd/exec.h>
#include <hurd/paths.h>
#include <string.h>

static int
scan_ids (uid_t *set, int setlen, uid_t test)
{
  int i;
  for (i = 0; i < setlen; i++)
    if (set[i] == test)
      return 1;
  return 0;
}

/* If SETID is true, adds ID to the sets OLDGENIDS & OLDAUXIDS, and returns
   the new set in GENIDS and AUXIDS, which are malloced; if SETID is false,
   just makes GENIDS and AUXIDS (malloced) copies of OLDGENIDS & OLDAUXIDS;
   SECURE is also updated to reflect whether a secure exec is called for.
   ENOMEM is returned if a malloc fails, otherwise 0.  The return parameters
   are only touched if this call succeeds.  */
static error_t
setid (int setid, uid_t id, int *secure,
       uid_t *oldgenids, size_t noldgenids,
       uid_t *oldauxids, size_t noldauxids,
       uid_t **genids, size_t *ngenids,
       uid_t **auxids, size_t *nauxids)
{
  /* These hold the new auxids array until we're sure we're going to return. */
  uid_t *_genids, *_auxids;
  size_t _ngenids, _nauxids;

/* Return malloced storage for N uids.  If the malloc fails, return ENOMEM
   from the function enclosing the call.  */
#define MALLOC_IDS(n) \
  ({ void *_p = malloc ((n) * sizeof (uid_t)); if (! _p) return ENOMEM; _p; })

/* Copy N uids/gids from SRC to DST.  */ 
#define COPY_IDS(src, dst, n) \
  bcopy (src, dst, (n) * sizeof (uid_t))

  if (setid)
    {
      /* We are dumping the current first id; put it into the auxids array.
	 This is complex.  The different cases below are intended to make
	 sure that we don't lose any ids (unlike posix) and to make sure that
	 aux ids zero and one (if already set) behave like the posix ones. */
      if (noldauxids == 0)
	{
	  if (noldgenids == 0)
	    {
	      _nauxids = 0;
	      _auxids = 0;
	    }
	  else
	    {
	      _auxids = MALLOC_IDS (_nauxids = 1);
	      _auxids[0] = oldgenids[0];
	    }
	}
      else if (noldauxids == 1)
	{
	  _nauxids = noldgenids > 0 ? 2 : 1;
	  _auxids = MALLOC_IDS (_nauxids);
	  _auxids[0] = oldauxids[0];
	  if (noldgenids > 0)
	    _auxids[1] = oldgenids[0];
	}
      else if (noldauxids == 2)
	{
	  if (noldgenids == 0 || oldgenids[0] == oldauxids[1])
	    {
	      _auxids = MALLOC_IDS (_nauxids = 2);
	      _auxids[0] = oldauxids[0];
	      _auxids[1] = oldauxids[1];
	    }
	  else
	    {
	      /* Shift by one */
	      _auxids = MALLOC_IDS (_nauxids = 3);
	      _auxids[0] = oldauxids[0];
	      _auxids[1] = oldgenids[0];
	      _auxids[2] = oldauxids[1];
	    }
	}
      else
	{
	  /* Just like above, but in the shift case note
	     that the new _auxids[2] shouldn't be allowed
	     to needlessly duplicate something further on. */
	  if (noldgenids == 0
	      || oldgenids[0] == oldauxids[1]
	      || scan_ids (&oldauxids[2], noldauxids - 2, oldauxids[1]))
	    {
	      _auxids = MALLOC_IDS (_nauxids = noldauxids);
	      COPY_IDS (oldauxids, _auxids, _nauxids);
	      if (noldgenids > 0)
		_auxids[1] = oldgenids[0];
	    }
	  else 
	    {
	      _auxids = MALLOC_IDS (_nauxids = noldauxids + 1);
	      _auxids[0] = oldauxids[0];
	      _auxids[1] = oldgenids[0];
	      COPY_IDS (&oldauxids[1], &_auxids[2], noldauxids - 1);
	    }
	}

      /* Whew.  Now set the new id. */
      _ngenids = noldgenids ?: 1;
      _genids = malloc (_ngenids * sizeof (uid_t));

      if (! _genids)
	{
	  free (_auxids);
	  return ENOMEM;
	}

      _genids[0] = id;
      if (noldgenids > 1)
	COPY_IDS (&oldgenids[1], &_genids[1], _ngenids - 1);

      if (secure && !*secure
	  && !scan_ids (oldgenids, noldgenids, id)
	  && !scan_ids (oldauxids, noldauxids, id))
	*secure = 1;
    }
  else
    /* Not SETID; just copy the old values.  */
    {
      _ngenids = noldgenids;
      _nauxids = noldauxids;
      _genids = MALLOC_IDS (_ngenids);
      _auxids = malloc (_nauxids * sizeof (uid_t));

      if (! _auxids)
	{
	  free (_genids);
	  return ENOMEM;
	}

      COPY_IDS (oldgenids, _genids, _ngenids);
      COPY_IDS (oldauxids, _auxids, _nauxids);
    }

  /* Finally we can zot the return params.  */
  *genids = _genids;
  *ngenids = _ngenids;
  *auxids = _auxids;
  *nauxids = _nauxids;

  return 0;
}

kern_return_t 
diskfs_S_file_exec (struct protid *cred,
		    task_t task,
		    int flags,
		    char *argv,
		    u_int argvlen,
		    char *envp,
		    u_int envplen,
		    mach_port_t *fds,
		    u_int fdslen,
		    mach_port_t *portarray,
		    u_int portarraylen,
		    int *intarray,
		    u_int intarraylen,
		    mach_port_t *deallocnames,
		    u_int deallocnameslen,
		    mach_port_t *destroynames,
		    u_int destroynameslen)
{
  struct node *np;
  error_t err;
  struct protid *newpi;
  int suid, sgid, secure;
  
  if (!cred)
    return EOPNOTSUPP;

  if (diskfs_exec == MACH_PORT_NULL)
    diskfs_exec = file_name_lookup (_SERVERS_EXEC, 0, 0);
  if (diskfs_exec == MACH_PORT_NULL)
    return EOPNOTSUPP;
  
  np = cred->po->np;

  mutex_lock (&np->lock);

  if ((cred->po->openstat & O_EXEC) == 0)
    {
      mutex_unlock (&np->lock);
      return EBADF;
    }
  
  if (!((np->dn_stat.st_mode & (S_IXUSR|S_IXGRP|S_IXOTH))
	|| ((np->dn_stat.st_mode & S_IUSEUNK)
	    && (np->dn_stat.st_mode & (S_IEXEC << S_IUNKSHIFT)))))
    {
      mutex_unlock (&np->lock);
      return EACCES;
    }
  
  if ((np->dn_stat.st_mode & S_IFMT) == S_IFDIR)
    {
      mutex_unlock (&np->lock);
      return EACCES;
    }

  suid = np->dn_stat.st_mode & S_ISUID; /* XXX not if we can't do it... */
  sgid = np->dn_stat.st_mode & S_ISGID;	/* XXX not of we can't do it... */
  secure = 0;
  
  if (suid || sgid)
    {
      /* These variables describe the auth port that the
	 user gave us. */
      uid_t aubuf[10], gubuf[10], agbuf[20], ggbuf[20];
      uid_t *oldauxuids = aubuf, *oldgenuids = gubuf;
      gid_t *oldauxgids = agbuf, *oldgengids = ggbuf;
      int noldauxuids = 10, noldgenuids = 10;
      int noldauxgids = 20, noldgengids = 20;

      /* These describe the auth port we are trying to create. */
      uid_t *auxuids = 0, *genuids = 0;
      gid_t *auxgids = 0, *gengids = 0;
      int nauxuids = 0, ngenuids = 0;
      int nauxgids = 0, ngengids = 0;
      auth_t newauth;

      int i;
      
      void
	reauth (mach_port_t *port, int isproc)
	  {
	    mach_port_t newport, ref;
	    if (*port == MACH_PORT_NULL)
	      return;
	    ref = mach_reply_port ();
	    err = (isproc ? proc_reauthenticate : io_reauthenticate)
	      (*port, ref, MACH_MSG_TYPE_MAKE_SEND);
	    if (!err)
	      err = auth_user_authenticate (newauth, *port, ref,
					    MACH_MSG_TYPE_MAKE_SEND, &newport);
	    if (err)
	      {
		/* Could not reauthenticate.  Roland thinks we should not
		   give away the old port.  I disagree; it can't actually hurt
		   because the old id's are still available, so it's no
		   security problem. */

		/* Nothing Happens. */
	      }
	    else
	      {
		if (isproc)
		  mach_port_deallocate (mach_task_self (), newport);
		else
		  {
		    mach_port_deallocate (mach_task_self (), *port);
		    *port = newport;
		  }
	      }
	    mach_port_destroy (mach_task_self (), ref);
	  }


      /* STEP 0: Fetch the user's current id's. */
      
      /* First fetch the current ID's the user has. */
      err = auth_getids (portarray[INIT_PORT_AUTH],
			 &oldgenuids, &noldgenuids,
			 &oldauxuids, &noldauxuids,
			 &oldgengids, &noldgengids,
			 &oldauxgids, &noldauxgids);
      if (err)
	goto abandon_suid;


      /* STEP 1: Find out if the user's permission will be
	 increasing, or just rearranged. */

      /* If the user's auth port is fraudulent, then these values
	 will be wrong.  No matter; we will repeat these checks
	 using secure id sets later if the port turns out to be 
	 bogus.  */

      err = setid (suid, np->dn_stat.st_uid, &secure,
		   oldgenuids, noldgenuids, oldauxuids, noldauxuids,
		   &genuids, &ngenuids, &auxuids, &nauxuids);
      if (! err)
	err = setid (sgid, np->dn_stat.st_gid, &secure,
		     oldgengids, noldgengids, oldauxgids, noldauxgids,
		     &gengids, &ngengids, &auxgids, &nauxgids);
      if (scan_ids (oldgenuids, noldgenuids, 0) 
	  || scan_ids (oldauxuids, noldauxuids, 0))
	secure = 0;		/* If we're root, we don't have to be. */
      
      /* Deallocate the buffers if MiG allocated them. */
      if (oldgenuids != gubuf)
	vm_deallocate (mach_task_self (), (vm_address_t) oldgenuids, 
		       noldgenuids * sizeof (uid_t));
      if (oldauxuids != aubuf)
	vm_deallocate (mach_task_self (), (vm_address_t) oldauxuids,
		       noldauxuids * sizeof (uid_t));
      if (oldgengids != ggbuf)
	vm_deallocate (mach_task_self (), (vm_address_t) oldgengids,
		       noldgengids * (sizeof (gid_t)));
      if (oldauxgids != agbuf)
	vm_deallocate (mach_task_self (), (vm_address_t) oldauxgids,
		       noldauxgids * (sizeof (gid_t)));

      if (err)
	goto free_abandon_suid;


      /* STEP 3: Attempt to create this new auth handle. */
      err = auth_makeauth (diskfs_auth_server_port, &portarray[INIT_PORT_AUTH],
			   MACH_MSG_TYPE_COPY_SEND, 1, 
			   genuids, ngenuids,
			   auxuids, nauxuids,
			   gengids, ngengids,
			   auxgids, nauxgids,
			   &newauth);
      if (err == EINVAL)
	/* The user's auth port was bogus.  As we can't trust what the user
	   has told us about ids, we use the authentication on the file being
	   execed (which we know is good), as the effective ids, and assume
	   no aux ids.  */
	{
	  /* Free our first attempts.  [Reinit to 0, so we can free them]  */
	  free (genuids); genuids = 0;
	  free (auxuids); auxuids = 0;
	  free (gengids); gengids = 0;
	  free (auxgids); auxgids = 0;

	  err = setid (suid, np->dn_stat.st_uid, &secure,
		       cred->uids, cred->nuids, 0, 0,
		       &genuids, &ngenuids, &auxuids, &nauxuids);
	  if (! err)
	    err = setid (sgid, np->dn_stat.st_gid, &secure,
			 cred->gids, cred->ngids, 0, 0,
			 &gengids, &ngengids, &auxgids, &nauxgids);
	  if (diskfs_isuid (0, cred))
	    secure = 0;		/* If we're root, we don't have to be. */

	  if (err)
	    goto abandon_suid;	/* setid() failed.  */

	  /* Trrrry again...  */
	  err = auth_makeauth (diskfs_auth_server_port, 0,
			       MACH_MSG_TYPE_COPY_SEND, 1, 
			       genuids, ngenuids, auxuids, nauxuids,
			       gengids, ngengids, auxgids, nauxgids,
			       &newauth);
	}

      if (err)
	goto free_abandon_suid;
      
      /* STEP 4: Re-authenticate all the ports we are handing to the user
	 with this new port, and install the new auth port in portarray. */
      for (i = 0; i < fdslen; ++i)
	reauth (&fds[i], 0);
      if (secure)
	/* Not worth doing; the exec server will just do it again.  */
	portarray[INIT_PORT_CRDIR] = MACH_PORT_NULL;
      else
	reauth (&portarray[INIT_PORT_CRDIR], 0);
      reauth (&portarray[INIT_PORT_PROC], 1);
      reauth (&portarray[INIT_PORT_CWDIR], 0);
      mach_port_deallocate (mach_task_self (), portarray[INIT_PORT_AUTH]);
      portarray[INIT_PORT_AUTH] = newauth;

      if (ngenuids > 0)
	proc_setowner (portarray[INIT_PORT_PROC], genuids[0]);

      /* STEP 5: If we must be secure, then set the appropriate flags
	 to tell the exec server so. */
      if (secure)
	flags |= EXEC_SECURE | EXEC_NEWTASK;

    free_abandon_suid:
      free (genuids);
      free (auxuids);
      free (gengids);
      free (auxgids);
    }
 abandon_suid:

  /* If the user can't read the file, then we should use a new task,
     which would be inaccessible to the user.  Actually, this doesn't
     work, because the proc server will still give out the task port
     to the user.  Too many things depend on that that it can't be
     changed.  So this vague attempt isn't even worth trying.  */
#if 0
  if (diskfs_access (np, S_IREAD, cred))
    flags |= EXEC_NEWTASK;
#endif

  newpi = diskfs_make_protid (diskfs_make_peropen (np, O_READ, 
						   cred->po->dotdotport),
			      cred->uids, cred->nuids,
			      cred->gids, cred->ngids);
  mutex_unlock (&np->lock);

  err = exec_exec (diskfs_exec, 
		   ports_get_right (newpi),
		   MACH_MSG_TYPE_MAKE_SEND,
		   task, flags, argv, argvlen, envp, envplen, 
		   fds, MACH_MSG_TYPE_COPY_SEND, fdslen,
		   portarray, MACH_MSG_TYPE_COPY_SEND, portarraylen,
		   intarray, intarraylen, deallocnames, deallocnameslen,
		   destroynames, destroynameslen);

  ports_port_deref (newpi);
  if (!err)
    {
      unsigned int i;
      
      mach_port_deallocate (mach_task_self (), task);
      for (i = 0; i < fdslen; i++)
	mach_port_deallocate (mach_task_self (), fds[i]);
      for (i = 0; i < portarraylen; i++)
	mach_port_deallocate (mach_task_self (), portarray[i]);
    }

  return err; 
}