2002-05-12 Roland McGrath <roland@frob.com>

* hurd/hurdexec.c (_hurd_exec): Reauthenticate ports/dtable used in
	file_exec to effect svuid=euid, svgid=egid if that is not a no-op.

hurd/hurdexec.c

@@ -1,4 +1,5 @@
-/* Copyright (C) 1991,92,93,94,95,96,97,99,2001 Free Software Foundation, Inc.
+/* Copyright (C) 1991,92,93,94,95,96,97,99,2001,02
+   	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
@@ -25,6 +26,7 @@
 #include <hurd.h>
 #include <hurd/fd.h>
 #include <hurd/signal.h>
+#include <hurd/id.h>
 #include <assert.h>
 #include <argz.h>
 
@@ -41,12 +43,17 @@ _hurd_exec (task_t task, file_t file,
   int ints[INIT_INT_MAX];
   mach_port_t ports[_hurd_nports];
   struct hurd_userlink ulink_ports[_hurd_nports];
+  inline void free_port (unsigned int i)
+    {
+      _hurd_port_free (&_hurd_ports[i], &ulink_ports[i], ports[i]);
+    }
   file_t *dtable;
   unsigned int dtablesize, i;
   struct hurd_port **dtable_cells;
   struct hurd_userlink *ulink_dtable;
   struct hurd_sigstate *ss;
   mach_port_t *please_dealloc, *pdp;
+  int reauth = 0;
 
   /* XXX needs to be hurdmalloc XXX */
   if (argv == NULL)
@@ -67,7 +74,7 @@ _hurd_exec (task_t task, file_t file,
 	if (err = __USEPORT (PROC, __proc_task2proc (port, task, &ports[i])))
 	  {
 	    while (--i > 0)
-	      _hurd_port_free (&_hurd_ports[i], &ulink_ports[i], ports[i]);
+	      free_port (i);
 	    goto outenv;
 	  }
       }
@@ -132,7 +139,7 @@ _hurd_exec (task_t task, file_t file,
        them, the new program would have duplicate user references for them.
        But we cannot deallocate them ourselves, because we must still have
        them after a failed exec call.  */
-    please_dealloc = __alloca ((_hurd_nports + (2 * dtablesize))
+    please_dealloc = __alloca ((_hurd_nports + 3 + (3 * dtablesize))
 				* sizeof (mach_port_t));
   else
     please_dealloc = NULL;
@@ -190,19 +197,155 @@ _hurd_exec (task_t task, file_t file,
   while (dtablesize > 0 && dtable[dtablesize - 1] == MACH_PORT_NULL)
     --dtablesize;
 
-  /* The information is all set up now.  Try to exec the file.  */
+  /* See if we need to diddle the auth port of the new program.
+     The purpose of this is to get the effect setting the saved-set UID and
+     GID to the respective effective IDs after the exec, as POSIX.1 requires.
+     Note that we don't reauthenticate with the proc server; that would be a
+     no-op since it only keeps track of the effective UIDs, and if it did
+     keep track of the available IDs we would have the problem that we'd be
+     changing the IDs before the exec and have to change them back after a
+     failure.  Arguably we could skip all the reauthentications because the
+     available IDs have no bearing on any filesystem.  But the conservative
+     approach is to reauthenticate all the io ports so that no state anywhere
+     reflects that our whole ID set differs from what we've set it to.  */
+  __mutex_lock (&_hurd_id.lock);
+  err = _hurd_check_ids ();
+  if (err == 0 && ((_hurd_id.aux.nuids >= 2 && _hurd_id.gen.nuids >= 1
+		    && _hurd_id.aux.uids[1] != _hurd_id.gen.uids[0])
+		   || (_hurd_id.aux.ngids >= 2 && _hurd_id.gen.ngids >= 1
+		       && _hurd_id.aux.gids[1] != _hurd_id.gen.gids[0])))
+    {
+      /* We have euid != svuid or egid != svgid.  POSIX.1 says that exec
+	 sets svuid = euid and svgid = egid.  So we must get a new auth
+	 port and reauthenticate everything with it.  We'll pass the new
+	 ports in file_exec instead of our own ports.  */
 
+      auth_t newauth;
+
+      _hurd_id.aux.uids[1] = _hurd_id.gen.uids[0];
+      _hurd_id.aux.gids[1] = _hurd_id.gen.gids[0];
+      _hurd_id.valid = 0;
+      if (_hurd_id.rid_auth != MACH_PORT_NULL)
+	{
+	  __mach_port_deallocate (__mach_task_self (), _hurd_id.rid_auth);
+	  _hurd_id.rid_auth = MACH_PORT_NULL;
+	}
+
+      err = __auth_makeauth (ports[INIT_PORT_AUTH],
+			     NULL, MACH_MSG_TYPE_COPY_SEND, 0,
+			     _hurd_id.gen.uids, _hurd_id.gen.nuids,
+			     _hurd_id.aux.uids, _hurd_id.aux.nuids,
+			     _hurd_id.gen.gids, _hurd_id.gen.ngids,
+			     _hurd_id.aux.gids, _hurd_id.aux.ngids,
+			     &newauth);
+      if (err == 0)
+	{
+	  /* Now we have to reauthenticate the ports with this new ID.
+	   */
+
+	  inline error_t reauth_io (io_t port, io_t *newport)
+	    {
+	      mach_port_t ref = __mach_reply_port ();
+	      *newport = MACH_PORT_NULL;
+	      error_t err = __io_reauthenticate (port,
+						 ref, MACH_MSG_TYPE_MAKE_SEND);
+	      if (!err)
+		err = __auth_user_authenticate (newauth,
+						ref, MACH_MSG_TYPE_MAKE_SEND,
+						newport);
+	      __mach_port_destroy (__mach_task_self (), ref);
+	      return err;
+	    }
+	  inline void reauth_port (unsigned int idx)
+	    {
+	      io_t newport;
+	      err = reauth_io (ports[idx], &newport) ?: err;
+	      if (pdp)
+		*pdp++ = ports[idx]; /* XXX presumed still in _hurd_ports */
+	      free_port (idx);
+	      ports[idx] = newport;
+	    }
+
+	  if (pdp)
+	    *pdp++ = ports[INIT_PORT_AUTH];
+	  free_port (INIT_PORT_AUTH);
+	  ports[INIT_PORT_AUTH] = newauth;
+
+	  reauth_port (INIT_PORT_CRDIR);
+	  reauth_port (INIT_PORT_CWDIR);
+
+	  if (!err)
+	    {
+	      /* Now we'll reauthenticate each file descriptor.  */
+	      if (ulink_dtable == NULL)
+		{
+		  assert (dtable == _hurd_init_dtable);
+		  dtable = __alloca (dtablesize * sizeof (dtable[0]));
+		  for (i = 0; i < dtablesize; ++i)
+		    if (_hurd_init_dtable[i] != MACH_PORT_NULL)
+		      {
+			if (pdp)
+			  *pdp++ = _hurd_init_dtable[i];
+			err = reauth_io (_hurd_init_dtable[i], &dtable[i]);
+			if (err)
+			  {
+			    while (++i < dtablesize)
+			      dtable[i] = MACH_PORT_NULL;
+			    break;
+			  }
+		      }
+		    else
+		      dtable[i] = MACH_PORT_NULL;
+		}
+	      else
+		{
+		  if (pdp)
+		    {
+		      /* Ask to deallocate all the old fd ports,
+			 since we will have new ones in DTABLE.  */
+		      memcpy (pdp, dtable, dtablesize * sizeof pdp[0]);
+		      pdp += dtablesize;
+		    }
+		  for (i = 0; i < dtablesize; ++i)
+		    if (dtable[i] != MACH_PORT_NULL)
+		      {
+			io_t newport;
+			err = reauth_io (dtable[i], &newport);
+			_hurd_port_free (dtable_cells[i], &ulink_dtable[i],
+					 dtable[i]);
+			dtable[i] = newport;
+			if (err)
+			  {
+			    while (++i < dtablesize)
+			      _hurd_port_free (dtable_cells[i],
+					       &ulink_dtable[i], dtable[i]);
+			    break;
+			  }
+		      }
+		  ulink_dtable = NULL;
+		  dtable_cells = NULL;
+		}
+	    }
+	}
+
+      reauth = 1;
+    }
+  __mutex_unlock (&_hurd_id.lock);
+
+  /* The information is all set up now.  Try to exec the file.  */
+  if (!err)
     {
       int flags;
 
       if (pdp)
 	{
-	/* Request the exec server to deallocate some ports from us if the exec
+	  /* Request the exec server to deallocate some ports from us if
-	   succeeds.  The init ports and descriptor ports will arrive in the
+	     the exec succeeds.  The init ports and descriptor ports will
-	   new program's exec_startup message.  If we failed to deallocate
+	     arrive in the new program's exec_startup message.  If we
-	   them, the new program would have duplicate user references for them.
+	     failed to deallocate them, the new program would have
-	   But we cannot deallocate them ourselves, because we must still have
+	     duplicate user references for them.  But we cannot deallocate
-	   them after a failed exec call.  */
+	     them ourselves, because we must still have them after a failed
+	     exec call.  */
 
 	  for (i = 0; i < _hurd_nports; ++i)
 	    *pdp++ = ports[i];
@@ -212,9 +355,10 @@ _hurd_exec (task_t task, file_t file,
 
       flags = 0;
 #ifdef EXEC_SIGTRAP
-    /* PTRACE_TRACEME sets all bits in _hurdsig_traced, which is propagated
+      /* PTRACE_TRACEME sets all bits in _hurdsig_traced, which is
-       through exec by INIT_TRACEMASK, so this checks if PTRACE_TRACEME has
+	 propagated through exec by INIT_TRACEMASK, so this checks if
-       been called in this process in any of its current or prior lives.  */
+	 PTRACE_TRACEME has been called in this process in any of its
+	 current or prior lives.  */
       if (__sigismember (&_hurdsig_traced, SIGKILL))
 	flags |= EXEC_SIGTRAP;
 #endif
@@ -229,16 +373,23 @@ _hurd_exec (task_t task, file_t file,
 
   /* Release references to the standard ports.  */
   for (i = 0; i < _hurd_nports; ++i)
-    if (i == INIT_PORT_PROC && task != __mach_task_self ())
+    if ((i == INIT_PORT_PROC && task != __mach_task_self ())
+	|| (reauth && (i == INIT_PORT_AUTH
+		       || i == INIT_PORT_CRDIR || i == INIT_PORT_CWDIR)))
       __mach_port_deallocate (__mach_task_self (), ports[i]);
     else
-      _hurd_port_free (&_hurd_ports[i], &ulink_ports[i], ports[i]);
+      free_port (i);
 
-  if (ulink_dtable != NULL)
   /* Release references to the file descriptor ports.  */
+  if (ulink_dtable != NULL)
+    {
       for (i = 0; i < dtablesize; ++i)
 	if (dtable[i] != MACH_PORT_NULL)
 	  _hurd_port_free (dtable_cells[i], &ulink_dtable[i], dtable[i]);
+    }
+  else if (dtable && dtable != _hurd_init_dtable)
+    for (i = 0; i < dtablesize; ++i)
+      __mach_port_deallocate (__mach_task_self (), dtable[i]);
 
   /* Release lock on the file descriptor table. */
   __mutex_unlock (&_hurd_dtable_lock);