2001-06-21 Neal H Walfield <neal@cs.uml.edu>

	* fshelp.h (fshelp_iscontroller): Declare new function.
	* perms-iscontroller.c: New file.
	* Makefile (SRCS): Add it.

3 files changed, 48 insertions, 2 deletions

diff --git a/libfshelp/Makefile b/libfshelp/Makefile
index 6dc47da6..11c14985 100644
--- a/libfshelp/Makefile
+++ b/libfshelp/Makefile
@@ -27,7 +27,8 @@ SRCS =	lock-acquire.c lock-init.c \
 	exec-reauth.c \
 	set-options.c \
 	get-identity.c \
-	perms-isowner.c perms-access.c perms-checkdirmod.c \
+	perms-isowner.c perms-iscontroller.c perms-access.c \
+	perms-checkdirmod.c \
 	touch.c
 LCLHDRS = fshelp.h locks.h trans.h
 installhdrs = fshelp.h
diff --git a/libfshelp/fshelp.h b/libfshelp/fshelp.h
index 81e1fadb..88f63b69 100644
--- a/libfshelp/fshelp.h
+++ b/libfshelp/fshelp.h
@@ -1,5 +1,5 @@
 /* FS helper library definitions
-   Copyright (C) 1994,95,96,97,98,99,2000 Free Software Foundation, Inc.
+   Copyright (C) 1994,95,96,97,98,99,2000,01 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
@@ -238,6 +238,13 @@ error_t fshelp_set_options (struct argp *argp, int flags,
    appropriate error code. */
 error_t fshelp_isowner (struct stat *st, struct iouser *user);
 
+/* Check to see whether USER should be considered a controller of the
+   filesystem.  Which is to say, check to see if we should give USER the
+   control port.  ST is the stat of the root node.  USER is the user
+   asking for a send right to the control port.  */
+error_t
+fshelp_iscontroller (struct stat *st, struct iouser *user);
+
 /* Check to see whether the user USER can operate on a file identified
    by ST.  OP is one of S_IREAD, S_IWRITE, and S_IEXEC.  If the access
    is permitted, return zero; otherwise return an appropriate error
diff --git a/libfshelp/perms-iscontroller.c b/libfshelp/perms-iscontroller.c
new file mode 100644
index 00000000..456da2a2
--- /dev/null
+++ b/libfshelp/perms-iscontroller.c
@@ -0,0 +1,38 @@
+/* see whether a user should be considered a controller of the filesystem
+   Copyright (C) 2001 Free Software Foundation, Inc.
+   Written by Neal H Walfield <neal@cs.uml.edu>.
+
+   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 this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA. */
+
+#include <unistd.h>
+#include "fshelp.h"
+
+/* Check to see whether USER should be considered a controller of the
+   filesystem.  Which is to say, check to see if we should give USER the
+   control port.  ST is the stat of the root node.  USER is the user
+   asking for a send right to the control port.  */
+error_t
+fshelp_iscontroller (struct stat *st, struct iouser *user)
+{
+  /* Permitted if USER has the superuser uid, the owner uid or if the
+     USER has authority over the process's effective id.  */
+  if (idvec_contains (user->uids, st->st_uid)
+      || idvec_contains (user->uids, st->st_uid)
+      || idvec_contains (user->uids, geteuid ()))
+    return 0;
+  return EPERM;
+}