Прога / tina-2.5.2 / tcl / lib / tcl8.3 / safe

# 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.
#
# RCS: @(#) $Id: safe.tcl,v 1.6.2.1 2001/04/03 22:54:38 hobbs Exp $

#
# 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;

# Create the safe namespace
namespace eval ::safe {

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

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

# 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)
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)
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)
proc InterpStatics {} {
foreach v {Args statics noStatics} {
upvar $v $v
}
set flag [::tcl::OptProcArgGiven -noStatics];
if {$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 $v
}
set flag [::tcl::OptProcArgGiven -nestedLoadOk];
# note that the test here is the opposite of the "InterpStatics"
# one (it is not -noNested... because of the wanted default value)
if {$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;
}

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
# 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...
# 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
# 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.
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"
::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} {
return -code error [::tcl::OptFlagUsage $desc $arg]
}
CheckInterp $slave
set item [::tcl::OptCurDesc $desc]
set name [::tcl::OptName $item]
switch -exact -- $name {
-accessPath {
return [list -accessPath [Set [PathListName $slave]]]
}
-statics {
return [list -statics [Set [StaticsOkName $slave]]]
}
-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
# that the user want, so force 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
set Args [::tcl::OptKeyParse ::safe::interpIC $args]
CheckInterp $slave
# 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 {(![::tcl::OptProcArgGiven -statics]) \
&& (![::tcl::OptProcArgGiven -noStatics]) } {
set statics [Set [StaticsOkName $slave]]
} else {
set statics [InterpStatics]
}
if {([::tcl::OptProcArgGiven -nested]) \
|| ([::tcl::OptProcArgGiven -nestedLoadOk]) } {
set nested [InterpNested]
} else {
set nested [Set [NestedOkName $slave]]
}
if {![::tcl::OptProcArgGiven -deleteHook]} {
set deleteHook [Set [DeleteHookName $slave]]
}
# we can now reconfigure :
InterpSetConfig $slave $accessPath $statics $nested $deleteHook
# auto_reset the slave (to completly synch the new access_path)
if {$doreset} {
if {[catch {::interp eval $slave {auto_reset}} msg]} {
Log $slave "auto_reset failed: $msg"
} else {
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}
#
# 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.
# + staticsok : flag, if 0 :no static package can be loaded (load {} Xxx)
# if 1 :static packages are ok.
# + nestedok: flag, if 0 :no loading to sub-sub interps (load xx xx sub)
# if 1 : multiple levels are ok.

# use the full name and no indent so auto_mkIndex can find us
proc ::safe::InterpCreate {
slave
access_path
staticsok
nestedok
deletehook
} {
# Create the slave.
if {[string compare "" $slave]} {
::interp create -safe $slave
} else {
# empty argument: generate slave name
set slave [::interp create -safe]
}
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.

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

# determine and store the access path if empty
if {[string equal "" $access_path]} {
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)
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).
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 nname [PathNumberName $slave]
if {[Exists $nname]} {
set n [Set $nname]
for {set i 0} {$i<$n} {incr i} {
Unset [PathToken $i $slave]
}
}

# build new one
set slave_auto_path {}
set i 0
foreach dir $access_path {
Set [PathToken $i $slave] $dir
lappend slave_auto_path "\$[PathToken $i]"
incr i
}
Set $nname $i
Set [PathListName $slave] $access_path
Set [VirtualPathListName $slave] $slave_auto_path

Set [StaticsOkName $slave] $staticsok
Set [NestedOkName $slave] $nestedok
Set [DeleteHookName $slave] $deletehook

SyncAccessPath $slave
}

#
#
# FindInAccessPath:
# 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 "$").
proc ::safe::interpAddToAccessPath {slave path} {
# first check if the directory is already in there
if {![catch {interpFindInAccessPath $slave $path} res]} {
return $res
}
# new one, add it:
set nname [PathNumberName $slave]
set n [Set $nname]
Set [PathToken $n $slave] $path

set token "\$[PathToken $n]"

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

SyncAccessPath $slave

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.
proc ::safe::InterpInit {
slave
access_path
staticsok
nestedok
deletehook
} {

# Configure will generate an access_path when access_path is
# 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

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

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

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

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

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


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

# We don't try to use the -rsrc on the mac because it would get
# confusing if you would want to customize init.tcl
# for a given set of safe slaves, on all the platforms
# you just need to give a specific access_path and
# the mac should be no exception. As there is no
# obvious full "safe ressources" design nor implementation
# for the mac, safe interps there will just don't
# have that ability. (A specific app can still reenable
# that using custom aliases if they want to).
# It would also make the security analysis and the Safe Tcl security
# model platform dependant and thus more error prone.

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

return $slave
}


# Add (only if needed, avoid duplicates) 1 level of
# sub directories to an 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
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:

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
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
Unset $hookname
if {[catch {eval $hook [list $slave]} err]} {
Log $slave "Delete hook error ($err)"
}
}
}

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

set statename [InterpStateName $slave]
if {[Exists $statename]} {
Unset $statename
}

# if we have been called twice, the interp might have been deleted
# already
if {[::interp exists $slave]} {
::interp delete $slave
Log $slave "Deleted" NOTICE
}

return
}

# Set (or get) the loging mecanism

proc ::safe::setLogCmd {args} {
variable Log
if {[llength $args] == 0} {
return $Log
} else {
if {[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.
#
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
# 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))
# We add the S prefix to avoid 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
# if the slave argument is given,
# it will return the corresponding master global variable name
proc PathToken {n {slave ""}} {
if {[string compare "" $slave]} {
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
# path.
return "p(:$n:)"
}
}
# returns the variable name of the complete path list
proc PathListName {slave} {
return "[InterpStateName $slave](access_path)"
}
# returns the variable name of the complete path list
proc VirtualPathListName {slave} {
return "[InterpStateName $slave](access_path_slave)"
}
# returns the variable name of the number of items
proc PathNumberName {slave} {
return "[InterpStateName $slave](access_path,n)"
}
# returns the staticsok flag var name
proc StaticsOkName {slave} {
return "[InterpStateName $slave](staticsok)"
}
# returns the nestedok flag var name
proc NestedOkName {slave} {
return "[InterpStateName $slave](nestedok)"
}
# Run some code at the namespace toplevel
proc Toplevel {args} {
namespace eval [namespace current] $args
}
# set/get values
proc Set {args} {
eval Toplevel set $args
}
# lappend on toplevel vars
proc Lappend {args} {
eval Toplevel lappend $args
}
# unset a var/token (currently just an global level eval)
proc Unset {args} {
eval Toplevel unset $args
}
# test existance
proc Exists {varname} {
Toplevel info exists $varname
}
# short cut for access path getting
proc GetAccessPath {slave} {
Set [PathListName $slave]
}
# short cut for statics ok flag getting
proc StaticsOk {slave} {
Set [StaticsOkName $slave]
}
# short cut for getting the multiples interps sub loading ok flag
proc NestedOk {slave} {
Set [NestedOkName $slave]
}
# interp deletion storing hook name
proc DeleteHookName {slave} {
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... :
if {[regexp {(::)|(\.\.)} $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
proc Log {slave msg {type ERROR}} {
variable Log
if {[info exists Log] && [llength $Log]} {
eval $Log [list "$type for slave $slave : $msg"]
}
}


# file name control (limit access to files/ressources that should be
# a valid tcl source file)
proc CheckFileName {slave file} {
# limit what can be sourced to .tcl
# and forbid files with more than 1 dot and
# longer than 14 chars
set ftail [file tail $file]
if {[string length $ftail]>14} {
error "$ftail: filename too long"
}
if {[regexp {\..*\.} $ftail]} {
error "$ftail: more than one dot is forbidden"
}
if {[string compare $ftail "tclIndex"] && \
[string compare -nocase [file extension $ftail] ".tcl"]} {
error "$ftail: must be a *.tcl or tclIndex"
}

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

if {![file readable $file]} {
# don't tell the file path
error "not readable"
}
}


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

proc AliasSource {slave args} {

set argc [llength $args]
# Allow only "source filename"
# (and not mac specific -rsrc for instance - see comment in ::init
# for current rationale)
if {$argc != 1} {
set msg "wrong # args: should be \"source fileName\""
Log $slave "$msg ($args)"
return -code error $msg
}
set file [lindex $args 0]

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

# check that the path is in the access path of that slave
if {[catch {FileInAccessPath $slave $file} msg]} {
Log $slave $msg
return -code error "permission denied"
}

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

# passed all the tests , lets source it:
if {[catch {::interp invokehidden $slave source $file} msg]} {
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.
set target [lindex $args 1]
if {[string length $target]} {
# 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 {[string length $file] == 0} {
# static package loading
if {[string length $package] == 0} {
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.
if {[catch {set file [TranslatePath $slave $file]} msg]} {
Log $slave $msg
return -code error "permission denied"
}

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

if {[catch {::interp invokehidden\
$slave load $file $package $target} 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
# access path.

# the security here relies on "file dirname" answering the proper
# 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]
if {[lsearch -exact $access_path $parent] == -1} {
error "\"$file\": not in access_path"
}
}

# 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 $subcommand]} {
return [eval {$command $subcommand} [lrange $args 1 end]]
}
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.
#
# Syntax is: AliasSubset slave alias target subcommand1 subcommand2...

proc AliasSubset {slave alias target args} {
set pat ^(; set sep ""
foreach sub $args {
append pat $sep$sub
set sep |
}
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 [eval ::interp invokehidden $slave encoding $subcommand \
[lrange $args 1 end]]
}

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

return $msg
}

}