# safe.tcl --
#
# This file provide a safe loading/sourcing mechanism for safe interpreters.
# It implements a virtual path mecanism to hide the real pathnames from the
# slave. It runs in a master interpreter and sets up data structure and
# aliases that will be invoked when used from a slave interpreter.
# 
# See the safe.n man page for details.
#
# Copyright (c) 1996-1997 Sun Microsystems, Inc.
#
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
# See the file "license.terms" for information on usage and redistribution of
# this file, and for a DISCLAIMER OF ALL WARRANTIES.
#
# RCS: @(#) $Id: safe.tcl,v 1.10.2.7 2008/06/26 04:07:40 dgp Exp $
# RCS: @(#) $Id: safe.tcl,v 1.10.2.8 2009/07/27 19:01:32 dgp Exp $

#
# The implementation is based on namespaces. These naming conventions
# are followed:
# The implementation is based on namespaces. These naming conventions are
# followed:
# Private procs starts with uppercase.
# Public  procs are exported and starts with lowercase
#

# Needed utilities package
package require opt 0.4.1;
package require opt 0.4.1

# Create the safe namespace
namespace eval ::safe {

    # Exported API:
    namespace export interpCreate interpInit interpConfigure interpDelete \
	    interpAddToAccessPath interpFindInAccessPath setLogCmd

    ####
    #
    # Setup the arguments parsing
    #
    ####

    # Make sure that our temporary variable is local to this
    # namespace.  [Bug 981733]
    # Make sure that our temporary variable is local to this namespace.  [Bug
    # 981733]
    variable temp

    # Share the descriptions
    set temp [::tcl::OptKeyRegister {
	{-accessPath -list {} "access path for the slave"}
	{-noStatics "prevent loading of statically linked pkgs"}
	{-statics true "loading of statically linked pkgs"}
	{-nestedLoadOk "allow nested loading"}
	{-nested false "nested loading"}
	{-deleteHook -script {} "delete hook"}
    }]

    # create case (slave is optional)
    ::tcl::OptKeyRegister {
	{?slave? -name {} "name of the slave (optional)"}
    } ::safe::interpCreate
    # adding the flags sub programs to the command program
    # (relying on Opt's internal implementation details)
    # adding the flags sub programs to the command program (relying on Opt's
    # internal implementation details)
    lappend ::tcl::OptDesc(::safe::interpCreate) $::tcl::OptDesc($temp)

    # init and configure (slave is needed)
    ::tcl::OptKeyRegister {
	{slave -name {} "name of the slave"}
    } ::safe::interpIC
    # adding the flags sub programs to the command program
    # (relying on Opt's internal implementation details)
    # adding the flags sub programs to the command program (relying on Opt's
    # internal implementation details)
    lappend ::tcl::OptDesc(::safe::interpIC) $::tcl::OptDesc($temp)
    # temp not needed anymore
    ::tcl::OptKeyDelete $temp


    # Helper function to resolve the dual way of specifying staticsok
    # (either by -noStatics or -statics 0)
    # Helper function to resolve the dual way of specifying staticsok (either
    # by -noStatics or -statics 0)
    proc InterpStatics {} {
	foreach v {Args statics noStatics} {
	    upvar $v $v
	}
	set flag [::tcl::OptProcArgGiven -noStatics];
	set flag [::tcl::OptProcArgGiven -noStatics]
	if {$flag && (!$noStatics == !$statics) 
	          && ([::tcl::OptProcArgGiven -statics])} {
	    return -code error\
		    "conflicting values given for -statics and -noStatics"
	}
	if {$flag} {
	    return [expr {!$noStatics}]
	} else {
	    return $statics
	}
    }

    # Helper function to resolve the dual way of specifying nested loading
    # (either by -nestedLoadOk or -nested 1)
    proc InterpNested {} {
	foreach v {Args nested nestedLoadOk} {
	    upvar $v $v
	}
	set flag [::tcl::OptProcArgGiven -nestedLoadOk];
	# note that the test here is the opposite of the "InterpStatics"
	# one (it is not -noNested... because of the wanted default value)
	set flag [::tcl::OptProcArgGiven -nestedLoadOk]
	# note that the test here is the opposite of the "InterpStatics" one
	# (it is not -noNested... because of the wanted default value)
	if {$flag && (!$nestedLoadOk != !$nested) 
	          && ([::tcl::OptProcArgGiven -nested])} {
	    return -code error\
		    "conflicting values given for -nested and -nestedLoadOk"
	}
	if {$flag} {
	    # another difference with "InterpStatics"
	    return $nestedLoadOk
	} else {
	    return $nested
	}
    }

    ####
    #
    #  API entry points that needs argument parsing :
    #
    ####


    # Interface/entry point function and front end for "Create"
    proc interpCreate {args} {
	set Args [::tcl::OptKeyParse ::safe::interpCreate $args]
	InterpCreate $slave $accessPath \
		[InterpStatics] [InterpNested] $deleteHook
    }

    proc interpInit {args} {
	set Args [::tcl::OptKeyParse ::safe::interpIC $args]
	if {![::interp exists $slave]} {
	    return -code error "\"$slave\" is not an interpreter"
	}
	InterpInit $slave $accessPath \
		[InterpStatics] [InterpNested] $deleteHook;
		[InterpStatics] [InterpNested] $deleteHook
    }

    proc CheckInterp {slave} {
	if {![IsInterp $slave]} {
	    return -code error \
		    "\"$slave\" is not an interpreter managed by ::safe::"
	}
    }

    # Interface/entry point function and front end for "Configure"
    # This code is awfully pedestrian because it would need
    # Interface/entry point function and front end for "Configure".  This code
    # is awfully pedestrian because it would need more coupling and support
    # more coupling and support between the way we store the
    # configuration values in safe::interp's and the Opt package
    # Obviously we would like an OptConfigure
    # to avoid duplicating all this code everywhere. -> TODO
    # (the app should share or access easily the program/value
    #  stored by opt)
    # This is even more complicated by the boolean flags with no values
    # that we had the bad idea to support for the sake of user simplicity
    # in create/init but which makes life hard in configure...
    # between the way we store the configuration values in safe::interp's and
    # the Opt package. Obviously we would like an OptConfigure to avoid
    # duplicating all this code everywhere.
    # -> TODO (the app should share or access easily the program/value stored
    # by opt)

    # This is even more complicated by the boolean flags with no values that
    # we had the bad idea to support for the sake of user simplicity in
    # create/init but which makes life hard in configure...
    # So this will be hopefully written and some integrated with opt1.0
    # (hopefully for tcl8.1 ?)
    proc interpConfigure {args} {
	switch [llength $args] {
	    1 {
		# If we have exactly 1 argument
		# If we have exactly 1 argument the semantic is to return all
		# the semantic is to return all the current configuration
		# We still call OptKeyParse though we know that "slave"
		# is our given argument because it also checks
		# for the "-help" option.
		# the current configuration. We still call OptKeyParse though
		# we know that "slave" is our given argument because it also
		# checks for the "-help" option.
		set Args [::tcl::OptKeyParse ::safe::interpIC $args]
		CheckInterp $slave
		set res {}
		lappend res [list -accessPath [Set [PathListName $slave]]]
		lappend res [list -statics    [Set [StaticsOkName $slave]]]
		lappend res [list -nested     [Set [NestedOkName $slave]]]
		lappend res [list -deleteHook [Set [DeleteHookName $slave]]]
		join $res
	    }
	    2 {
		# If we have exactly 2 arguments
		# the semantic is a "configure get"
		# If we have exactly 2 arguments the semantic is a "configure
		# get"
		::tcl::Lassign $args slave arg

		# get the flag sub program (we 'know' about Opt's internal
		# representation of data)
		set desc [lindex [::tcl::OptKeyGetDesc ::safe::interpIC] 2]
		set hits [::tcl::OptHits desc $arg]
                if {$hits > 1} {
                    return -code error [::tcl::OptAmbigous $desc $arg]
                } elseif {$hits == 0} {

		    -nested {
			return [list -nested     [Set [NestedOkName $slave]]]
		    }
		    -deleteHook {
			return [list -deleteHook [Set [DeleteHookName $slave]]]
		    }
		    -noStatics {
			# it is most probably a set in fact
			# but we would need then to jump to the set part
			# and it is not *sure* that it is a set action
			# it is most probably a set in fact but we would need
			# then to jump to the set part and it is not *sure*
			# that it is a set action that the user want, so force
			# that the user want, so force it to use the
			# unambigous -statics ?value? instead:
			# it to use the unambigous -statics ?value? instead:
			return -code error\
				"ambigous query (get or set -noStatics ?)\
				use -statics instead"
		    }
		    -nestedLoadOk {
			return -code error\
				"ambigous query (get or set -nestedLoadOk ?)\
				use -nested instead"
		    }
		    default {
			return -code error "unknown flag $name (bug)"
		    }
		}
	    }
	    default {
		# Otherwise we want to parse the arguments like init and create
		# did
		# Otherwise we want to parse the arguments like init and
		# create did
		set Args [::tcl::OptKeyParse ::safe::interpIC $args]
		CheckInterp $slave

		# Get the current (and not the default) values of
		# whatever has not been given:
		# Get the current (and not the default) values of whatever has
		# not been given:
		if {![::tcl::OptProcArgGiven -accessPath]} {
		    set doreset 1
		    set accessPath [Set [PathListName $slave]]
		} else {
		    set doreset 0
		}
		if {
		if {(![::tcl::OptProcArgGiven -statics]) \
			&& (![::tcl::OptProcArgGiven -noStatics]) } {
		    ![::tcl::OptProcArgGiven -statics]
		    && ![::tcl::OptProcArgGiven -noStatics]
		} then {
		    set statics    [Set [StaticsOkName $slave]]
		} else {
		    set statics    [InterpStatics]
		}
		if {
		if {([::tcl::OptProcArgGiven -nested]) \
			|| ([::tcl::OptProcArgGiven -nestedLoadOk]) } {
		    [::tcl::OptProcArgGiven -nested] ||
		    [::tcl::OptProcArgGiven -nestedLoadOk]
		} then {
		    set nested     [InterpNested]
		} else {
		    set nested     [Set [NestedOkName $slave]]
		}
		if {![::tcl::OptProcArgGiven -deleteHook]} {
		    set deleteHook [Set [DeleteHookName $slave]]
		}

			Log $slave "successful auto_reset" NOTICE
		    }
		}
	    }
	}
    }


    ####
    #
    #  Functions that actually implements the exported APIs
    #
    ####


    #
    # safe::InterpCreate : doing the real job
    #
    # This procedure creates a safe slave and initializes it with the
    # safe base aliases.
    # NB: slave name must be simple alphanumeric string, no spaces,
    # no (), no {},...  {because the state array is stored as part of the name}
    # This procedure creates a safe slave and initializes it with the safe
    # base aliases.
    # NB: slave name must be simple alphanumeric string, no spaces, no (), no
    # {},...  {because the state array is stored as part of the name}
    #
    # Returns the slave name.
    #
    # Optional Arguments : 
    # + slave name : if empty, generated name will be used
    # + access_path: path list controlling where load/source can occur,
    #                if empty: the master auto_path will be used.

	}
	Log $slave "Created" NOTICE

	# Initialize it. (returns slave name)
	InterpInit $slave $access_path $staticsok $nestedok $deletehook
    }


    #
    #
    # InterpSetConfig (was setAccessPath) :
    #    Sets up slave virtual auto_path and corresponding structure
    #    within the master. Also sets the tcl_library in the slave
    #    to be the first directory in the path.
    #    Nb: If you change the path after the slave has been initialized
    #    you probably need to call "auto_reset" in the slave in order that it
    #    gets the right auto_index() array values.
    #    Sets up slave virtual auto_path and corresponding structure within
    #    the master. Also sets the tcl_library in the slave to be the first
    #    directory in the path.
    #    NB: If you change the path after the slave has been initialized you
    #    probably need to call "auto_reset" in the slave in order that it gets
    #    the right auto_index() array values.

    proc ::safe::InterpSetConfig {slave access_path staticsok\
	    nestedok deletehook} {

	# determine and store the access path if empty
	if {$access_path eq ""} {
	    set access_path [uplevel \#0 set auto_path]
	    # Make sure that tcl_library is in auto_path
	    # and at the first position (needed by setAccessPath)
	    # Make sure that tcl_library is in auto_path and at the first
	    # position (needed by setAccessPath)
	    set where [lsearch -exact $access_path [info library]]
	    if {$where == -1} {
		# not found, add it.
		set access_path [concat [list [info library]] $access_path]
		Log $slave "tcl_library was not in auto_path,\
			added it to slave's access_path" NOTICE
	    } elseif {$where != 0} {
		# not first, move it first
		set access_path [concat [list [info library]]\
			[lreplace $access_path $where $where]]
		Log $slave "tcl_libray was not in first in auto_path,\
			moved it to front of slave's access_path" NOTICE
	    
	    }

	    # Add 1st level sub dirs (will searched by auto loading from tcl
	    # code in the slave using glob and thus fail, so we add them
	    # here so by default it works the same).
	    # code in the slave using glob and thus fail, so we add them here
	    # so by default it works the same).
	    set access_path [AddSubDirs $access_path]
	}

	Log $slave "Setting accessPath=($access_path) staticsok=$staticsok\
		nestedok=$nestedok deletehook=($deletehook)" NOTICE

	# clear old autopath if it existed

	set slave_auto_path {}
	set i 0
	foreach dir $access_path {
	    Set [PathToken $i $slave] $dir
	    lappend slave_auto_path "\$[PathToken $i]"
	    incr i
	}
	# Extend the access list with the paths used to look for Tcl
	# Modules. We safe the virtual form separately as well, as
	# syncing it with the slave has to be defered until the
	# necessary commands are present for setup.
	# Extend the access list with the paths used to look for Tcl Modules.
	# We save the virtual form separately as well, as syncing it with the
	# slave has to be defered until the necessary commands are present for
	# setup.
	foreach dir [::tcl::tm::list] {
	    lappend access_path $dir
	    Set [PathToken $i $slave] $dir
	    lappend slave_auto_path "\$[PathToken $i]"
	    lappend slave_tm_path   "\$[PathToken $i]"
	    incr i
	}

	SyncAccessPath $slave
    }

    #
    #
    # FindInAccessPath:
    #    Search for a real directory and returns its virtual Id
    #    (including the "$")
    #    Search for a real directory and returns its virtual Id (including the
    #    "$")
proc ::safe::interpFindInAccessPath {slave path} {
	set access_path [GetAccessPath $slave]
	set where [lsearch -exact $access_path $path]
	if {$where == -1} {
	    return -code error "$path not found in access path $access_path"
	}
	return "\$[PathToken $where]"
    }

    #
    # addToAccessPath:
    #    add (if needed) a real directory to access path
    #    and return its virtual token (including the "$").
    #    add (if needed) a real directory to access path and return its
    #    virtual token (including the "$").
proc ::safe::interpAddToAccessPath {slave path} {
	# first check if the directory is already in there
	try {
	if {![catch {interpFindInAccessPath $slave $path} res]} {
	    return $res
	    return [interpFindInAccessPath $slave $path]
	} on error {} {
	}
	# new one, add it:
	set nname [PathNumberName $slave]
	set n [Set $nname]
	Set [PathToken $n $slave] $path
	    # new one, add it:
	    set nname [PathNumberName $slave]
	    set n [Set $nname]
	    Set [PathToken $n $slave] $path

	set token "\$[PathToken $n]"
	    set token "\$[PathToken $n]"

	Lappend [VirtualPathListName $slave] $token
	Lappend [PathListName $slave] $path
	Set $nname [expr {$n+1}]
	    Lappend [VirtualPathListName $slave] $token
	    Lappend [PathListName $slave] $path
	    Set $nname [expr {$n+1}]

	SyncAccessPath $slave
	    SyncAccessPath $slave

	return $token
    }

	    return $token
	}
    }

    # This procedure applies the initializations to an already existing
    # interpreter. It is useful when you want to install the safe base
    # aliases into a preexisting safe interpreter.
    # interpreter. It is useful when you want to install the safe base aliases
    # into a preexisting safe interpreter.
    proc ::safe::InterpInit {
	slave 
	access_path
	staticsok
	nestedok
	deletehook
    } {

	# Configure will generate an access_path when access_path is
	# Configure will generate an access_path when access_path is empty.
	# empty.
	InterpSetConfig $slave $access_path $staticsok $nestedok $deletehook

	# These aliases let the slave load files to define new commands

	# NB we need to add [namespace current], aliases are always
	# absolute paths.
	::interp alias $slave source {} [namespace current]::AliasSource $slave
	::interp alias $slave load {} [namespace current]::AliasLoad $slave
	# NB we need to add [namespace current], aliases are always absolute
	# paths.
	::interp alias $slave source {} \
		[namespace current]::AliasSource $slave
	::interp alias $slave load {} \
		[namespace current]::AliasLoad $slave

	# This alias lets the slave use the encoding names, convertfrom,
	# convertto, and system, but not "encoding system <name>" to set
	# the system encoding.
	# convertto, and system, but not "encoding system <name>" to set the
	# system encoding.

	::interp alias $slave encoding {} [namespace current]::AliasEncoding \
		$slave
	::interp alias $slave encoding {} \
		[namespace current]::AliasEncoding $slave

	# Handling Tcl Modules, we need a restricted form of Glob.
	::interp alias $slave glob {} [namespace current]::AliasGlob \
		$slave
	::interp alias $slave glob {} \
		[namespace current]::AliasGlob $slave

	# This alias lets the slave have access to a subset of the 'file'
	# command functionality.

	AliasSubset $slave file file dir.* join root.* ext.* tail \
		path.* split
	AliasSubset $slave file \
		file  dir.* join root.* ext.* tail path.* split

	# This alias interposes on the 'exit' command and cleanly terminates
	# the slave.

	::interp alias $slave exit {} [namespace current]::interpDelete $slave
	::interp alias $slave exit {} \
		[namespace current]::interpDelete $slave

	# The allowed slave variables already have been set
	# The allowed slave variables already have been set by Tcl_MakeSafe(3)
	# by Tcl_MakeSafe(3)


	# Source init.tcl and tm.tcl into the slave, to get auto_load
	# and other procedures defined:
	# Source init.tcl and tm.tcl into the slave, to get auto_load and
	# other procedures defined:

	if {[catch {::interp eval $slave\
		{source [file join $tcl_library init.tcl]}} msg]} {
	if {[catch {::interp eval $slave {
	    source [file join $tcl_library init.tcl]
	}} msg]} then {
	    Log $slave "can't source init.tcl ($msg)"
	    error "can't source init.tcl into slave $slave ($msg)"
	}

	if {[catch {::interp eval $slave \
		{source [file join $tcl_library tm.tcl]}} msg]} {
	if {[catch {::interp eval $slave {
	    source [file join $tcl_library tm.tcl]
	}} msg]} then {
	    Log $slave "can't source tm.tcl ($msg)"
	    error "can't source tm.tcl into slave $slave ($msg)"
	}

	# Sync the paths used to search for Tcl modules. This can be
	# done only now, after tm.tcl was loaded.
	::interp eval $slave [list ::tcl::tm::add {*}[Set [TmPathListName $slave]]]
	# Sync the paths used to search for Tcl modules. This can be done only
	# now, after tm.tcl was loaded.
	::interp eval $slave [list \
		::tcl::tm::add {*}[Set [TmPathListName $slave]] ]

	return $slave
    }


    # Add (only if needed, avoid duplicates) 1 level of
    # Add (only if needed, avoid duplicates) 1 level of sub directories to an
    # sub directories to an existing path list.
    # Also removes non directories from the returned list.
    # existing path list.  Also removes non directories from the returned
    # list.
    proc AddSubDirs {pathList} {
	set res {}
	foreach dir $pathList {
	    if {[file isdirectory $dir]} {
		# check that we don't have it yet as a children
		# of a previous dir
		# check that we don't have it yet as a children of a previous
		# dir
		if {[lsearch -exact $res $dir]<0} {
		    lappend res $dir
		}
		foreach sub [glob -directory $dir -nocomplain *] {
		    if {([file isdirectory $sub]) \
			    && ([lsearch -exact $res $sub]<0) } {
			# new sub dir, add it !
	                lappend res $sub
	            }
		}
	    }
	}
	return $res
    }

    # This procedure deletes a safe slave managed by Safe Tcl and
    # cleans up associated state:
    # This procedure deletes a safe slave managed by Safe Tcl and cleans up
    # associated state:

proc ::safe::interpDelete {slave} {

        Log $slave "About to delete" NOTICE

	# If the slave has a cleanup hook registered, call it.
	# check the existance because we might be called to delete an interp
	# which has not been registered with us at all
	# If the slave has a cleanup hook registered, call it.  Check the
	# existance because we might be called to delete an interp which has
	# not been registered with us at all
	set hookname [DeleteHookName $slave]
	if {[Exists $hookname]} {
	    set hook [Set $hookname]
	    if {![::tcl::Lempty $hook]} {
		# remove the hook now, otherwise if the hook
		# calls us somehow, we'll loop
		# remove the hook now, otherwise if the hook calls us somehow,
		# we'll loop
		Unset $hookname
		try {
		if {[catch {{*}$hook $slave} err]} {
		    {*}$hook $slave
		} on error err {
		    Log $slave "Delete hook error ($err)"
		}
	    }
	}

	# Discard the global array of state associated with the slave, and
	# delete the interpreter.

	return
    }

    # Set (or get) the loging mecanism 

proc ::safe::setLogCmd {args} {
    variable Log
    if {[llength $args] == 0} {
	return $Log
	variable Log
	if {[llength $args] == 0} {
	    return $Log
    } else {
	if {[llength $args] == 1} {
	} elseif {[llength $args] == 1} {
	    set Log [lindex $args 0]
	} else {
	    set Log $args
	}
    }
}

    # internal variable
    variable Log {}

    # ------------------- END OF PUBLIC METHODS ------------


    #
    #
    # sets the slave auto_path to the master recorded value.
    # also sets tcl_library to the first token of the virtual path.
    # Sets the slave auto_path to the master recorded value.  Also sets
    # tcl_library to the first token of the virtual path.
    #
    proc SyncAccessPath {slave} {
	set slave_auto_path [Set [VirtualPathListName $slave]]
	::interp eval $slave [list set auto_path $slave_auto_path]
	Log $slave "auto_path in $slave has been set to $slave_auto_path"\
		NOTICE
	::interp eval $slave [list set tcl_library [lindex $slave_auto_path 0]]
    }

    # base name for storing all the slave states
    # Base name for storing all the slave states.  The array variable name for
    # the array variable name for slave foo is thus "Sfoo"
    # and for sub slave {foo bar} "Sfoo bar" (spaces are handled
    # ok everywhere (or should))
    # slave foo is thus "Sfoo" and for sub slave {foo bar} "Sfoo bar" (spaces
    # are handled ok everywhere (or should)).  We add the S prefix to avoid
    # We add the S prefix to avoid that a slave interp called "Log"
    # would smash our "Log" variable.
    # that a slave interp called "Log" would smash our "Log" variable.
    proc InterpStateName {slave} {
	return "S$slave"
    }

    # Check that the given slave is "one of us"
    proc IsInterp {slave} {
	expr {[Exists [InterpStateName $slave]] && [::interp exists $slave]}
    }

    # returns the virtual token for directory number N
    # Returns the virtual token for directory number N.  If the slave argument
    # if the slave argument is given, 
    # it will return the corresponding master global variable name
    # is given, it will return the corresponding master global variable name
    proc PathToken {n {slave ""}} {
	if {$slave ne ""} {
	    return "[InterpStateName $slave](access_path,$n)"
	} else {
	    # We need to have a ":" in the token string so
	    # [file join] on the mac won't turn it into a relative
	    # We need to have a ":" in the token string so [file join] on the
	    # mac won't turn it into a relative path.
	    # path.
	    return "p(:$n:)"
	}
    }
    # returns the variable name of the complete path list
    proc PathListName {slave} {
	return "[InterpStateName $slave](access_path)"
    }

	return [InterpStateName $slave](cleanupHook)
    }

    #
    # translate virtual path into real path
    #
    proc TranslatePath {slave path} {
	# somehow strip the namespaces 'functionality' out (the danger
	# is that we would strip valid macintosh "../" queries... :
	# somehow strip the namespaces 'functionality' out (the danger is that
	# we would strip valid macintosh "../" queries... :
	if {[string match "*::*" $path] || [string match "*..*" $path]} {
	    error "invalid characters in path $path"
	}
	set n [expr {[Set [PathNumberName $slave]]-1}]
	for {} {$n>=0} {incr n -1} {
	    # fill the token virtual names with their real value
	    set [PathToken $n] [Set [PathToken $n $slave]]
	}
	# replaces the token by their value
	subst -nobackslashes -nocommands $path
    }


    # Log eventually log an error
    # to enable error logging, set Log to {puts stderr} for instance
    # Log eventually log an error; to enable error logging, set Log to {puts
    # stderr} for instance
    proc Log {slave msg {type ERROR}} {
	variable Log
	if {[info exists Log] && [llength $Log]} {
	    {*}$Log "$type for slave $slave : $msg"
	}
    }


    # file name control (limit access to files/ressources that should be
    # a valid tcl source file)
    # file name control (limit access to files/resources that should be a
    # valid tcl source file)
    proc CheckFileName {slave file} {
	# This used to limit what can be sourced to ".tcl" and forbid files
	# with more than 1 dot and longer than 14 chars, but I changed that
	# for 8.4 as a safe interp has enough internal protection already
	# to allow sourcing anything. - hobbs
	# for 8.4 as a safe interp has enough internal protection already to
	# allow sourcing anything. - hobbs

	if {![file exists $file]} {
	    # don't tell the file path
	    error "no such file or directory"
	}

	if {![file readable $file]} {

	set dir        {}
	set virtualdir {}

	while {$at < [llength $args]} {
	    switch -glob -- [set opt [lindex $args $at]] {
		-nocomplain -
		-join       { lappend cmd $opt ; incr at }
		-join       {
		    lappend cmd $opt
		    incr at
		}
		-directory  {
		    lappend cmd $opt ; incr at
		    lappend cmd $opt
		    incr at
		    set virtualdir [lindex $args $at]

		    # get the real path from the virtual one.
		    try {
		    if {[catch {set dir [TranslatePath $slave $virtualdir]} msg]} {
			set dir [TranslatePath $slave $virtualdir]
		    } on error msg {
			Log $slave $msg
			return -code error "permission denied"
		    }
		    # check that the path is in the access path of that slave
		    try {
		    if {[catch {DirInAccessPath $slave $dir} msg]} {
			DirInAccessPath $slave $dir
		    } on error msg {
			Log $slave $msg
			return -code error "permission denied"
		    }
		    lappend cmd $dir ; incr at
		    lappend cmd $dir
		    incr at
		}
		pkgIndex.tcl {
		    # Oops, this is globbing a subdirectory in regular
		    # package search. That is not wanted. Abort,
		    # handler does catch already (because glob was not
		    # defined before). See package.tcl, lines 484ff in
		    # Oops, this is globbing a subdirectory in regular package
		    # search. That is not wanted. Abort, handler does catch
		    # already (because glob was not defined before). See
		    # package.tcl, lines 484ff in tclPkgUnknown.
		    # tclPkgUnknown.
		    error "unknown command glob"
		}
		-* {
		    Log $slave "Safe base rejecting glob option '$opt'"
		    error      "Safe base rejecting glob option '$opt'"
		}
		default {
		    lappend cmd $opt ; incr at
		    lappend cmd $opt
		    incr at
		}
	    }
	}

	Log $slave "GLOB = $cmd" NOTICE

	try {
	if {[catch {::interp invokehidden $slave glob {*}$cmd} msg]} {
	    ::interp invokehidden $slave glob {*}$cmd
	} on error msg {
	    Log $slave $msg
	    return -code error "script error"
	}

	Log $slave "GLOB @ $msg" NOTICE

	# Translate path back to what the slave should see.
	set res {}
	foreach p $msg {
	    regsub -- ^$dir $p $virtualdir p
	    lappend res $p
	}

	Log $slave "GLOB @ $res" NOTICE
	return $res
    }

    # AliasSource is the target of the "source" alias in safe interpreters.

    proc AliasSource {slave args} {

	set argc [llength $args]
	# Extended for handling of Tcl Modules to allow not only
	# "source filename", but "source -encoding E filename" as
	# Extended for handling of Tcl Modules to allow not only "source
	# filename", but "source -encoding E filename" as well.
	# well.
	if {[lindex $args 0] eq "-encoding"} {
	    incr argc -2
	    set encoding [lrange $args 0 1]
	    set at 2
	} else {
	    set at 0
	    set encoding {}
	}
	if {$argc != 1} {
	    set msg "wrong # args: should be \"source ?-encoding E? fileName\""
	    Log $slave "$msg ($args)"
	    return -code error $msg
	}
	set file [lindex $args $at]
	
	# get the real path from the virtual one.
	try {
	if {[catch {set file [TranslatePath $slave $file]} msg]} {
	    set file [TranslatePath $slave $file]
	} on error msg {
	    Log $slave $msg
	    return -code error "permission denied"
	}
	
	# check that the path is in the access path of that slave
	try {
	if {[catch {FileInAccessPath $slave $file} msg]} {
	    FileInAccessPath $slave $file
	} on error msg {
	    Log $slave $msg
	    return -code error "permission denied"
	}

	# do the checks on the filename :
	try {
	if {[catch {CheckFileName $slave $file} msg]} {
	    CheckFileName $slave $file
	} on error msg {
	    Log $slave "$file:$msg"
	    return -code error $msg
	}

	# passed all the tests , lets source it:
	if {[catch {
	    # We use catch here because we want to catch non-error/ok too
	if {[catch {::interp invokehidden $slave source {*}$encoding $file} msg]} {
	    ::interp invokehidden $slave source {*}$encoding $file
	} msg]} then {
	    Log $slave $msg
	    return -code error "script error"
	}
	return $msg
    }

    # AliasLoad is the target of the "load" alias in safe interpreters.

    proc AliasLoad {slave file args} {

	set argc [llength $args]
	if {$argc > 2} {
	    set msg "load error: too many arguments"
	    Log $slave "$msg ($argc) {$file $args}"
	    return -code error $msg
	}

	# package name (can be empty if file is not).
	set package [lindex $args 0]

	# Determine where to load. load use a relative interp path
	# and {} means self, so we can directly and safely use passed arg.
	# Determine where to load. load use a relative interp path and {}
	# means self, so we can directly and safely use passed arg.
	set target [lindex $args 1]
	if {$target ne ""} {
	    # we will try to load into a sub sub interp
	    # check that we want to authorize that.
	    # we will try to load into a sub sub interp; check that we want to
	    # authorize that.
	    if {![NestedOk $slave]} {
		Log $slave "loading to a sub interp (nestedok)\
			disabled (trying to load $package to $target)"
		return -code error "permission denied (nested load)"
	    }
	    
	}

	# Determine what kind of load is requested
	if {$file eq ""} {
	    # static package loading
	    if {$package eq ""} {
		set msg "load error: empty filename and no package name"
		Log $slave $msg
		return -code error $msg
	    }
	    if {![StaticsOk $slave]} {
		Log $slave "static packages loading disabled\
			(trying to load $package to $target)"
		return -code error "permission denied (static package)"
	    }
	} else {
	    # file loading

	    # get the real path from the virtual one.
	    try {
	    if {[catch {set file [TranslatePath $slave $file]} msg]} {
		set file [TranslatePath $slave $file]
	    } on error msg {
		Log $slave $msg
		return -code error "permission denied"
	    }

	    # check the translated path
	    try {
	    if {[catch {FileInAccessPath $slave $file} msg]} {
		FileInAccessPath $slave $file
	    } on error msg {
		Log $slave $msg
		return -code error "permission denied (path)"
	    }
	}

	if {[catch {::interp invokehidden\
		$slave load $file $package $target} msg]} {
	try {
	    ::interp invokehidden $slave load $file $package $target
	} on error msg {
	    Log $slave $msg
	    return -code error $msg
	}

	return $msg
    }

    # FileInAccessPath raises an error if the file is not found in
    # the list of directories contained in the (master side recorded) slave's
    # FileInAccessPath raises an error if the file is not found in the list of
    # directories contained in the (master side recorded) slave's access path.
    # access path.

    # the security here relies on "file dirname" answering the proper
    # result.... needs checking ?
    # result... needs checking ?
    proc FileInAccessPath {slave file} {

	set access_path [GetAccessPath $slave]

	if {[file isdirectory $file]} {
	    error "\"$file\": is a directory"
	}
	set parent [file dirname $file]

	# Normalize paths for comparison since lsearch knows nothing of
	# potential pathname anomalies.
	set norm_parent [file normalize $parent]
	foreach path $access_path {
	    lappend norm_access_path [file normalize $path]
	}

	if {[lsearch -exact $norm_access_path $norm_parent] == -1} {
	if {$norm_parent ni $norm_access_path} {
	    error "\"$file\": not in access_path"
	}
    }

    proc DirInAccessPath {slave dir} {
	set access_path [GetAccessPath $slave]

	if {[file isfile $dir]} {
	    error "\"$dir\": is a file"
	}

	# Normalize paths for comparison since lsearch knows nothing of
	# potential pathname anomalies.
	set norm_dir [file normalize $dir]
	foreach path $access_path {
	    lappend norm_access_path [file normalize $path]
	}

	if {[lsearch -exact $norm_access_path $norm_dir] == -1} {
	if {$norm_dir ni $norm_access_path} {
	    error "\"$dir\": not in access_path"
	}
    }

    # This procedure enables access from a safe interpreter to only a subset of
    # the subcommands of a command:
    # This procedure enables access from a safe interpreter to only a subset
    # of the subcommands of a command:

    proc Subset {slave command okpat args} {
	set subcommand [lindex $args 0]
	if {[regexp $okpat $subcommand]} {
	    return [$command {*}$args]
	}
	set msg "not allowed to invoke subcommand $subcommand of $command"
	Log $slave $msg
	error $msg
    }

    # This procedure installs an alias in a slave that invokes "safesubset"
    # in the master to execute allowed subcommands. It precomputes the pattern
    # of allowed subcommands; you can use wildcards in the pattern if you wish
    # to allow subcommand abbreviation.
    # This procedure installs an alias in a slave that invokes "safesubset" in
    # the master to execute allowed subcommands. It precomputes the pattern of
    # allowed subcommands; you can use wildcards in the pattern if you wish to
    # allow subcommand abbreviation.
    #
    # Syntax is: AliasSubset slave alias target subcommand1 subcommand2...

    proc AliasSubset {slave alias target args} {
	set pat ^(; set sep ""
	set pat "^("
	set sep ""
	foreach sub $args {
	    append pat $sep$sub
	    set sep |
	}
	append pat )\$
	append pat ")\$"
	::interp alias $slave $alias {}\
		[namespace current]::Subset $slave $target $pat
    }

    # AliasEncoding is the target of the "encoding" alias in safe interpreters.

    proc AliasEncoding {slave args} {

	set argc [llength $args]

	set okpat "^(name.*|convert.*)\$"
	set subcommand [lindex $args 0]

	if {[regexp $okpat $subcommand]} {
	    return [::interp invokehidden $slave encoding {*}$args]
	}

	if {[string first $subcommand system] == 0} {
	    if {$argc == 1} {
		# passed all the tests , lets source it:
		try {
		if {[catch {::interp invokehidden \
			$slave encoding system} msg]} {
		    return [::interp invokehidden $slave encoding system]
		} on error msg {
		    Log $slave $msg
		    return -code error "script error"
		}
	    } else {
		set msg "wrong # args: should be \"encoding system\""
		Log $slave $msg
		error $msg
	    }
	    set msg "wrong # args: should be \"encoding system\""
	} else {
	    set msg "wrong # args: should be \"encoding option ?arg ...?\""
	}
	    Log $slave $msg
	    error $msg
	}

	Log $slave $msg
	error $msg
    }
}
	return $msg
    }

}