[PATCH] New function (libfshelp) fshelp_cancontrol

[Neal H Walfield]

At the moment, libdiskfs, libnetfs and libtrivfs will only give the
control port to root (Cf. lib{disk,net,triv}fs/file-getcontrol.c).
This is inherently wrong:  a user should be able to get the control
port to a file system if they can send a signal to the process, etc.
Thus, this patch introduces a new funtion, fshelp_cancontrol, into
libfshelp which each of the aforementioned libraries calls.

What does this gain?  After a user starts a translator, they can
use fsysopts, etc.

diff -urN hurd-20010307-snapshot/libfshelp/ChangeLog 
hurd-20010313/libfshelp/ChangeLog
--- hurd-20010307-snapshot/libfshelp/ChangeLog  Wed Jan 31 00:45:32 2001
+++ hurd-20010313/libfshelp/ChangeLog   Fri Mar 30 15:50:52 2001
@@ -1,3 +1,10 @@
+2001-03-29  Neal H Walfield  <neal@cs.uml.edu>
+
+       * fshelp.h: Add function declaration for fshelp_cancontrol.
+       * perms-cancontrol.c:  New file; implementation of
+       fshelp_cancontrol.
+       * Makefile (SRCS): Added perms-cancontrol.c.
+
 2001-01-17  Neal H Walfield  <neal@cs.uml.edu>
 
        * fshelp.h: Add two new parameters to fshelp_open_fn_t:
diff -urN hurd-20010307-snapshot/libfshelp/Makefile 
hurd-20010313/libfshelp/Makefile
--- hurd-20010307-snapshot/libfshelp/Makefile   Thu Jul  1 23:04:24 1999
+++ hurd-20010313/libfshelp/Makefile    Fri Mar 30 15:46:50 2001
@@ -1,5 +1,5 @@
 #
-#   Copyright (C) 1994, 95, 96, 98, 1999 Free Software Foundation, Inc.
+#   Copyright (C) 1994,95,96,98,99,2001 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
@@ -27,7 +27,7 @@
        exec-reauth.c \
        set-options.c \
        get-identity.c \
-       perms-isowner.c perms-access.c perms-checkdirmod.c \
+       perms-isowner.c perms-access.c perms-checkdirmod.c perms-cancontrol.c \
        touch.c
 LCLHDRS = fshelp.h locks.h trans.h
 installhdrs = fshelp.h
diff -urN hurd-20010307-snapshot/libfshelp/fetch-root.c 
hurd-20010313/libfshelp/fetch-root.c
diff -urN hurd-20010307-snapshot/libfshelp/fshelp.h 
hurd-20010313/libfshelp/fshelp.h
--- hurd-20010307-snapshot/libfshelp/fshelp.h   Wed Jan 31 00:45:32 2001
+++ hurd-20010313/libfshelp/fshelp.h    Fri Mar 30 15:47:02 2001
@@ -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
@@ -232,6 +232,10 @@
 
 
 /*  Standardized filesystem permission checking */
+
+/* Check to see whether USER can control the file system, i.e. get
+   a control port.  */
+error_t fshelp_cancontrol (struct iouser *user);
 
 /* Check to see whether USER should be considered the owner of the
    file identified by ST.  If so, return zero; otherwise return an
diff -urN hurd-20010307-snapshot/libfshelp/perms-cancontrol.c 
hurd-20010313/libfshelp/perms-cancontrol.c
--- hurd-20010307-snapshot/libfshelp/perms-cancontrol.c Thu Jan  1 01:00:00 1970
+++ hurd-20010313/libfshelp/perms-cancontrol.c  Fri Mar 30 15:54:12 2001
@@ -0,0 +1,69 @@
+/* Copyright (C) 2001 Free Software Foundation
+
+   This program 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.
+
+   This program 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., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include "fshelp.h"
+#include <errno.h>
+#include <hurd.h>
+#include <hurd/auth.h>
+
+/* Determine if user USER can get our control port.  */
+/* In the Hurd, the a user has authority over another user if at least
+   one the following conditions are met:
+
+     *  The client is root
+     *  At least one of the client's uids match one of the server's uids
+ */
+error_t fshelp_cancontrol (struct iouser *user)
+{
+  error_t err;
+  struct idvec *uids;
+  auth_t auth;
+  int i, j;
+
+  if (idvec_contains (user->uids, 0))
+    return 0;
+
+  uids = make_idvec ();
+  if (! uids)
+    return ENOMEM;
+
+  auth = getauth ();
+  if (auth == MACH_PORT_NULL)
+    {
+      idvec_free (uids);
+      return errno;
+    }
+  
+  err = idvec_merge_auth (uids, NULL, NULL, NULL, auth);
+  mach_port_deallocate (mach_task_self (), auth);
+  if (err)
+    {
+      idvec_free (uids);
+      return err;
+    }
+  
+  for (i = 0; i < user->uids->num; i ++)
+    for (j = 0; j < uids->num; j ++)
+      if (user->uids->ids[i] == uids->ids[j])
+        {
+         idvec_free (uids);
+         return 0;
+       }
+
+  idvec_free (uids);
+  return EPERM;
+}
+
--- hurd-20010329-snapshot/libdiskfs/file-getcontrol.c  Wed Nov 13 01:18:37 1996
+++ hurd-20010329/libdiskfs/file-getcontrol.c   Fri Mar 30 17:29:13 2001
@@ -1,5 +1,5 @@
 /* libdiskfs implementation of fs.defs:file_getcontrol.c
-   Copyright (C) 1992, 1993, 1994, 1995, 1996 Free Software Foundation
+   Copyright (C) 1992,93,94,95,96,2001 Free Software Foundation
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
@@ -17,6 +17,7 @@
 
 #include "priv.h"
 #include "fs_S.h"
+#include <hurd/fshelp.h>
 
 /* Implement file_getcontrol as described in <hurd/fs.defs>. */
 kern_return_t
@@ -24,28 +25,27 @@
                          mach_port_t *control,
                          mach_msg_type_name_t *controltype)
 {
-  int error = 0;
+  int err;
   struct port_info *newpi;
   
   if (!cred)
     return EOPNOTSUPP;
   
-  if (!idvec_contains (cred->user->uids, 0))
-    error = EPERM;
-  else
-    {
-      error = ports_create_port (diskfs_control_class, diskfs_port_bucket,
-                                sizeof (struct port_info), &newpi);
-      if (! error)
-       {
-         spin_lock (&_diskfs_control_lock);
-         _diskfs_ncontrol_ports++;
-         spin_unlock (&_diskfs_control_lock);
-         *control = ports_get_right (newpi);
-         *controltype = MACH_MSG_TYPE_MAKE_SEND;
-         ports_port_deref (newpi);
-       }
-    }
+  err = fshelp_cancontrol (cred->user);
+  if (err)
+    return err;
+
+  err = ports_create_port (diskfs_control_class, diskfs_port_bucket,
+                          sizeof (struct port_info), &newpi);
+  if (err)
+    return err;
+
+  spin_lock (&_diskfs_control_lock);
+  _diskfs_ncontrol_ports++;
+  spin_unlock (&_diskfs_control_lock);
+  *control = ports_get_right (newpi);
+  *controltype = MACH_MSG_TYPE_MAKE_SEND;
+  ports_port_deref (newpi);
 
-  return error;
+  return 0;
 }
--- hurd-20010329-snapshot/libnetfs/file-getcontrol.c   Tue Nov 19 00:50:14 1996
+++ hurd-20010329/libnetfs/file-getcontrol.c    Fri Mar 30 17:29:03 2001
@@ -1,6 +1,6 @@
 /* Return the filesystem corresponding to a file
 
-   Copyright (C) 1995, 1996 Free Software Foundation, Inc.
+   Copyright (C) 1995, 1996, 2001 Free Software Foundation, Inc.
    Written by Michael I. Bushnell, p/BSG.
 
    This file is part of the GNU Hurd.
@@ -21,6 +21,7 @@
 
 #include "netfs.h"
 #include "fsys_S.h"
+#include <hurd/fshelp.h>
 
 error_t
 netfs_S_file_getcontrol (struct protid *user,
@@ -33,10 +34,10 @@
   if (!user)
     return EOPNOTSUPP;
 
-  if (!idvec_contains (user->user->uids, 0))
-    return EPERM;
+  err = fshelp_cancontrol (user->user);
+  if (err)
+    return err;
   
-  /* They've got root; give it to them. */
   err = ports_create_port (netfs_control_class, netfs_port_bucket,
                           sizeof (struct port_info), &pi);
   if (err)
--- hurd-20010329-snapshot/libtrivfs/file-getcontrol.c  Mon Nov 13 19:55:02 1995
+++ hurd-20010329/libtrivfs/file-getcontrol.c   Fri Mar 30 17:28:41 2001
@@ -1,5 +1,5 @@
 /* 
-   Copyright (C) 1994 Free Software Foundation
+   Copyright (C) 1994, 2001 Free Software Foundation
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
@@ -17,17 +17,21 @@
 
 #include "priv.h"
 #include "fs_S.h"
+#include <hurd/fshelp.h>
 
 kern_return_t
 trivfs_S_file_getcontrol (struct trivfs_protid *cred,
                          mach_port_t reply, mach_msg_type_name_t reply_type,
                          mach_port_t *cntl, mach_msg_type_name_t *cntltype)
 {
+  error_t err;
   if (!cred)
     return EOPNOTSUPP;
-  if (!cred->isroot)
-    return EPERM;
   
+  err = fshelp_cancontrol (cred->user);
+  if (err)
+    return err;
+
   *cntl = ports_get_right (cred->po->cntl);
   *cntltype = MACH_MSG_TYPE_MAKE_SEND;
   return 0;

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