a2p
accept
access
acct
addftinfo
addr2line
adjtime
afmtodit
after
aio_cancel
aio_error
aio_read
aio_return
aio_suspend
aio_waitcomplete
aio_write
alias
aliases
alloc
anvil
append
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ar
array
as
asa
asn1parse
at
atq
atrm
attemptckalloc
attemptckrealloc
authlib
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autopoint
awk
b64decode
b64encode
basename
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bc
bdes
bell
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bgerror
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big5
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bootparams
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c99
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calendar
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chio
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clock_gettime
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cpp
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destroy
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dh
dhparam
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diff
diff3
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dngettext
do
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dprofpp
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dtmfdecode
du
dup
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eaccess
ec
ecdsa
echo
echotc
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ed
edit
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ee
egrep
elf
elfdump
elif
else
enc
enc2xs
encoding
end
endif
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engine
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entry
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envsubst
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eqn
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errno
error
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eui64
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history
host
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http
hup
i386_get_ioperm
i386_get_ldt
i386_set_ioperm
i386_set_ldt
i386_vm86
iconv
id
ident
idprio
if
ifnames253
ifnames259
image
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incr
indent
indxbib
info
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inode
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intro
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limit
limits
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lj4_font
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ln
load
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locale
locate
lock
lockf
log
logger
login
logins
logname
logout
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lookbib
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lower
lp
lpq
lpr
lprm
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lsort
lstat
lsvfs
lutimes
lynx
m4
madvise
magic
mail
maildiracl
maildirkw
maildirmake
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mailx
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makeinfo
makewhatis
man
manpath
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mc
mcedit
mcview
md2
md4
md5
mdc2
memory
menu
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menubutton
merge
mesg
message
mincore
minherit
minigzip
mkdep
mkdir
mkfifo
mkimapdcert
mklocale
mknod
mkpop3dcert
mkstr
mktemp
mlock
mlockall
mmap
mmroff
modfind
modfnext
modnext
modstat
moduli
more
motd
mount
mprotect
mptable
msdos
msdosfs
msgattrib
msgcat
msgcmp
msgcomm
msgconv
msgen
msgexec
msgfilter
msgfmt
msggrep
msginit
msgmerge
msgs
msgunfmt
msguniq
mskanji
msql2mysql
msync
mt
munlock
munlockall
munmap
mv
myisamchk
myisamlog
myisampack
mysql
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mysqldump
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mysqld_safe
mysqlhotcopy
mysqlimport
mysqlshow
mysql_config
mysql_fix_privilege_tables
mysql_zap
namespace
nanosleep
nawk
nc
ncal
ncplist
ncplogin
ncplogout
neqn
netconfig
netgroup
netid
netstat
networks
newaliases
newgrp
nex
nfsstat
nfssvc
ngettext
nice
nl
nm
nmount
nohup
nologin
notify
nroff
nseq
nslookup
ntp_adjtime
ntp_gettime
nvi
nview
objcopy
objdump
objformat
ocsp
od
onintr
open
openssl
opieaccess
opieinfo
opiekey
opiekeys
opiepasswd
option
options
oqmgr
pack
package
packagens
pagesize
palette
pam_auth
panedwindow
parray
passwd
paste
patch
pathchk
pathconf
pawd
pax
pbm
pcre
pcreapi
pcrebuild
pcrecallout
pcrecompat
pcrecpp
pcregrep
pcrematching
pcrepartial
pcrepattern
pcreperform
pcreposix
pcreprecompile
pcresample
pcretest
perl
perl56delta
perl58delta
perl561delta
perl570delta
perl571delta
perl572delta
perl573delta
perl581delta
perl582delta
perl583delta
perl584delta
perl585delta
perl586delta
perl587delta
perl588delta
perl5004delta
perl5005delta
perlaix
perlamiga
perlapi
perlapio
perlapollo
perlartistic
perlbeos
perlbook
perlboot
perlbot
perlbs2000
perlbug
perlcall
perlcc
perlce
perlcheat
perlclib
perlcn
perlcompile
perlcygwin
perldata
perldbmfilter
perldebguts
perldebtut
perldebug
perldelta
perldgux
perldiag
perldoc
perldos
perldsc
perlebcdic
perlembed
perlepoc
perlfaq
perlfaq1
perlfaq2
perlfaq3
perlfaq4
perlfaq5
perlfaq6
perlfaq7
perlfaq8
perlfaq9
perlfilter
perlfork
perlform
perlfreebsd
perlfunc
perlglossary
perlgpl
perlguts
perlhack
perlhist
perlhpux
perlhurd
perlintern
perlintro
perliol
perlipc
perlirix
perlivp
perljp
perlko
perllexwarn
perllinux
perllocale
perllol
perlmachten
perlmacos
perlmacosx
perlmint
perlmod
perlmodinstall
perlmodlib
perlmodstyle
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perlnetware
perlnewmod
perlnumber
perlobj
perlop
perlopenbsd
perlopentut
perlos2
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perlos400
perlothrtut
perlpacktut
perlplan9
perlpod
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perlport
perlqnx
perlre
perlref
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perlreref
perlretut
perlrun
perlsec
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perlsub
perlsyn
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perltodo
perltooc
perltoot
perltrap
perltru64
perltw
perlunicode
perluniintro
perlutil
perluts
perlvar
perlvmesa
perlvms
perlvos
perlwin32
perlxs
perlxstut
perror
pfbtops
pftp
pgrep
phones
photo
pic
pickup
piconv
pid
pipe
pkcs7
pkcs8
pkcs12
pkg_add
pkg_check
pkg_create
pkg_delete
pkg_info
pkg_sign
pkg_version
pkill
pl2pm
place
pod2html
pod2latex
pod2man
pod2text
pod2usage
podchecker
podselect
poll
popd
popup
posix_madvise
postalias
postcat
postconf
postdrop
postfix
postkick
postlock
postlog
postmap
postqueue
postsuper
pr
pread
preadv
printcap
printenv
printf
proc
procfs
profil
protocols
prove
proxymap
ps
psed
psroff
pstruct
ptrace
publickey
pushd
puts
pwd
pwrite
pwritev
qmgr
qmqpd
quota
quotactl
radiobutton
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rand
ranlib
rcp
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rcsfile
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ree
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replace
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resource
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ripemd160
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rpc
rpcgen
rs
rsa
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rup
ruptime
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rwho
s2p
safe
sasl
sasldblistusers2
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sched_get_priority_max
sched_get_priority_min
sched_rr_get_interval
sched_setparam
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sched_yield
scon
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script
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selection
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semop
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set
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setpriority
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setsockopt
settc
settimeofday
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sha
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sha256
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size
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socket
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sockstat
soelim
sort
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speed
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split
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ssh_config
stab
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strings
strip
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su
subst
sum
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syscall
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sysconftoolcheck
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s_server
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talk
tar
tbl
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tee
tell
telltc
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term
termcap
terminfo
test
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text
textdomain
tfmtodit
tftp
then
threads
time
tip
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top
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tr
trace
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true
truncate
truss
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tsort
tty
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type
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ui
ul
ulimit
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units
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until
unvis
update
uplevel
uptime
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usbhidctl
users
utf8
utimes
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uuidgen
vacation
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version
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vi
vidcontrol
vidfont
view
virtual
vis
vt220keys
vwait
w
wait
wait3
wait4
waitpid
wall
wc
wget
what
whatis
where
whereis
which
while
who
whoami
whois
window
winfo
wish
wm
write
writev
wtmp
x509
xargs
xgettext
xmlwf
xstr
xsubpp
yacc
yes
ypcat
ypchfn
ypchpass
ypchsh
ypmatch
yppasswd
ypwhich
yyfix
zcat
zcmp
zdiff
zegrep
zfgrep
zforce
zgrep
zmore
znew
_exit
__syscall
 
FreeBSD/Linux/UNIX General Commands Manual
Hypertext Man Pages
safe
 
Safe Tcl(n)		     Tcl Built-In Commands		   Safe Tcl(n)



NAME
       Safe Base  -  A	mechanism  for	creating  and manipulating safe inter-
       preters.

SYNOPSIS
       ::safe::interpCreate ?slave? ?options...?

       ::safe::interpInit slave ?options...?

       ::safe::interpConfigure slave ?options...?

       ::safe::interpDelete slave

       ::safe::interpAddToAccessPath slave directory

       ::safe::interpFindInAccessPath slave directory

       ::safe::setLogCmd ?cmd arg...?

OPTIONS
       ?-accessPath  pathList?	 ?-statics  boolean?  ?-noStatics?    ?-nested
       boolean? ?-nestedLoadOk?  ?-deleteHook script?


DESCRIPTION
       Safe  Tcl is a mechanism for executing untrusted Tcl scripts safely and
       for providing mediated access by such scripts to potentially  dangerous
       functionality.

       The  Safe Base ensures that untrusted Tcl scripts cannot harm the host-
       ing application.  The Safe Base prevents integrity and privacy attacks.
       Untrusted  Tcl  scripts	are prevented from corrupting the state of the
       hosting application or computer. Untrusted scripts are  also  prevented
       from  disclosing  information  stored on the hosting computer or in the
       hosting application to any party.

       The Safe Base allows a master interpreter to  create  safe,  restricted
       interpreters  that  contain a set of predefined aliases for the source,
       load, file, encoding, and exit commands and are able to use  the  auto-
       loading and package mechanisms.

       No  knowledge of the file system structure is leaked to the safe inter-
       preter, because it has access only to  a  virtualized  path  containing
       tokens.	When  the  safe interpreter requests to source a file, it uses
       the token in the virtual path as part of the file name to  source;  the
       master  interpreter  transparently  translates  the  token  into a real
       directory name and executes the requested operation  (see  the  section
       SECURITY  below	for  details).	 Different  levels  of security can be
       selected by using the optional flags of the commands described below.

       All commands provided in the master interpreter by the Safe Base reside
       in the safe namespace:


COMMANDS
       The following commands are provided in the master interpreter:

       ::safe::interpCreate ?slave? ?options...?
	      Creates  a  safe	interpreter, installs the aliases described in
	      the section ALIASES and initializes the auto-loading and package
	      mechanism as specified by the supplied options.  See the OPTIONS
	      section below for a description of the optional  arguments.   If
	      the  slave  argument  is	omitted,  a  name  will  be generated.
	      ::safe::interpCreate always returns the interpreter name.

       ::safe::interpInit slave ?options...?
	      This command is similar to interpCreate except it that does  not
	      create  the  safe  interpreter.  slave must have been created by
	      some other means, like interp create -safe.

       ::safe::interpConfigure slave ?options...?
	      If no options are given, returns the settings  for  all  options
	      for  the	named  safe interpreter as a list of options and their
	      current values for that slave.  If a single additional  argument
	      is  provided, it will return a list of 2 elements name and value
	      where name is the full name of that option and value the current
	      value  for  that	option	and the slave.	If more than two addi-
	      tional arguments are provided,  it  will	reconfigure  the  safe
	      interpreter  and change each and only the provided options.  See
	      the section on OPTIONS below for options	description.   Example
	      of use:
	      # Create a new interp with the same configuration as "$i0" : set
	      i1 [eval safe::interpCreate [safe::interpConfigure $i0]]	#  Get
	      the  current deleteHook set dh [safe::interpConfigure $i0  -del]
	      # Change (only) the statics loading ok attribute of an interp  #
	      and  its deleteHook (leaving the rest unchanged) : safe::interp-
	      Configure $i0  -delete {foo bar} -statics 0 ;

       ::safe::interpDelete slave
	      Deletes the safe interpreter and	cleans	up  the  corresponding
	      master  interpreter data structures.  If a deleteHook script was
	      specified for this interpreter it is evaluated before the inter-
	      preter  is deleted, with the name of the interpreter as an addi-
	      tional argument.

       ::safe::interpFindInAccessPath slave directory
	      This command finds and returns the token for the real  directory
	      directory in the safe interpreter's current virtual access path.
	      It generates an error if the directory is not found.  Example of
	      use:
	      $slave eval [list set tk_library [::safe::interpFindInAccessPath
	      $name $tk_library]]

       ::safe::interpAddToAccessPath slave directory
	      This command adds directory to the virtual path  maintained  for
	      the  safe  interpreter in the master, and returns the token that
	      can be used in the safe interpreter to obtain access to files in
	      that  directory.	 If  the  directory  is already in the virtual
	      path, it only returns the token without adding the directory  to
	      the virtual path again.  Example of use:
	      $slave  eval [list set tk_library [::safe::interpAddToAccessPath
	      $name $tk_library]]

       ::safe::setLogCmd ?cmd arg...?
	      This command installs a script that will be called  when	inter-
	      esting  life  cycle  events  occur for a safe interpreter.  When
	      called with no arguments, it  returns  the  currently  installed
	      script.	When  called  with  one argument, an empty string, the
	      currently installed script is removed and logging is turned off.
	      The  script  will  be  invoked  with  one additional argument, a
	      string describing the event of interest.	The main purpose is to
	      help  in	debugging  safe interpreters.  Using this facility you
	      can get complete error messages while the safe interpreter  gets
	      only  generic  error messages.  This prevents a safe interpreter
	      from seeing messages about failures and other events that  might
	      contain sensitive information such as real directory names.
	      Example  of use: ::safe::setLogCmd puts stderr Below is the out-
	      put of a sample session in which a safe interpreter attempted to
	      source  a  file not found in its virtual access path.  Note that
	      the safe interpreter only received an error message saying  that
	      the  file  was  not  found:  NOTICE for slave interp10 : Created
	      NOTICE for slave interp10 : Setting accessPath=(/foo/bar)  stat-
	      icsok=1  nestedok=0  deletehook=()  NOTICE  for slave interp10 :
	      auto_path in interp10 has been set to {$p(:0:)} ERROR for  slave
	      interp10 : /foo/bar/init.tcl: no such file or directory


OPTIONS
       The    following    options   are   common   to	 ::safe::interpCreate,
       ::safe::interpInit, and ::safe::interpConfigure.  Any option  name  can
       be abbreviated to its minimal non-ambiguous name.  Option names are not
       case sensitive.

       -accessPath directoryList
	      This option sets the list of directories	from  which  the  safe
	      interpreter  can	source	and load files.  If this option is not
	      specified, or if it is given as the empty list, the safe	inter-
	      preter  will  use  the  same directories as its master for auto-
	      loading.	See the section SECURITY below for more  detail  about
	      virtual paths, tokens and access control.

       -statics boolean
	      This option specifies if the safe interpreter will be allowed to
	      load statically linked packages (like load {} Tk).  The  default
	      value is true : safe interpreters are allowed to load statically
	      linked packages.

       -noStatics
	      This option is a convenience shortcut  for  -statics  false  and
	      thus  specifies that the safe interpreter will not be allowed to
	      load statically linked packages.

       -nested boolean
	      This option specifies if the safe interpreter will be allowed to
	      load  packages into its own sub-interpreters.  The default value
	      is false : safe interpreters are not allowed  to	load  packages
	      into their own sub-interpreters.

       -nestedLoadOk
	      This  option is a convenience shortcut for -nested true and thus
	      specifies the safe interpreter will be allowed to load  packages
	      into its own sub-interpreters.

       -deleteHook script
	      When  this option is given a non-empty script, it will be evalu-
	      ated in the master with the name of the safe interpreter	as  an
	      additional  argument  just  before  actually  deleting  the safe
	      interpreter.   Giving  an  empty	value  removes	any  currently
	      installed  deletion  hook script for that safe interpreter.  The
	      default value ({}) is not to have any deletion call back.

ALIASES
       The following aliases are provided in a safe interpreter:

       source fileName
	      The requested file, a Tcl source file, is sourced into the  safe
	      interpreter  if  it  is found.  The source alias can only source
	      files from directories in the virtual path for the  safe	inter-
	      preter.  The  source  alias requires the safe interpreter to use
	      one of the token names in its virtual path to denote the	direc-
	      tory in which the file to be sourced can be found.  See the sec-
	      tion on SECURITY for more discussion of  restrictions  on  valid
	      filenames.

       load fileName
	      The  requested file, a shared object file, is dynamically loaded
	      into the safe interpreter if it is  found.   The	filename  must
	      contain  a token name mentioned in the virtual path for the safe
	      interpreter for it to be found successfully.  Additionally,  the
	      shared object file must contain a safe entry point; see the man-
	      ual page for the load command for more details.

       file ?subCmd args...?
	      The file alias provides access to a safe subset of  the  subcom-
	      mands  of the file command; it allows only dirname, join, exten-
	      sion, root, tail,  pathname  and	split  subcommands.  For  more
	      details on what these subcommands do see the manual page for the
	      file command.

       encoding ?subCmd args...?
	      The encoding alias provides access to a safe subset of the  sub-
	      commands	of  the encoding command;  it disallows setting of the
	      system encoding, but allows all other subcommands including sys-
	      tem to check the current encoding.

       exit   The  calling  interpreter  is  deleted  and  its	computation is
	      stopped, but the Tcl process in which this interpreter exists is
	      not terminated.


SECURITY
       The  Safe  Base	does  not  attempt to completely prevent annoyance and
       denial of service attacks. These forms of attack prevent  the  applica-
       tion  or  user  from  temporarily  using the computer to perform useful
       work, for example by consuming all available CPU time or all  available
       screen real estate.  These attacks, while aggravating, are deemed to be
       of lesser importance in general than integrity and privacy attacks that
       the Safe Base is to prevent.

       The  commands  available in a safe interpreter, in addition to the safe
       set as defined in interp manual page, are mediated aliases for  source,
       load, exit, and safe subsets of file and encoding. The safe interpreter
       can also auto-load code and it can request that packages be loaded.

       Because some of these commands access the local file system, there is a
       potential  for  information  leakage about its directory structure.  To
       prevent this, commands that take file names  as	arguments  in  a  safe
       interpreter  use  tokens  instead  of  the real directory names.  These
       tokens are translated to the real directory name while  a  request  to,
       e.g.,  source  a file is mediated by the master interpreter.  This vir-
       tual path system is maintained in the master interpreter for each  safe
       interpreter   created   by   ::safe::interpCreate   or  initialized  by
       ::safe::interpInit and the path maps  tokens  accessible  in  the  safe
       interpreter into real path names on the local file system thus prevent-
       ing safe interpreters from gaining knowledge about the structure of the
       file  system  of  the  host on which the interpreter is executing.  The
       only valid file names arguments for the source and  load  aliases  pro-
       vided  to  the slave are path in the form of [file join token filename]
       (i.e. when using the native file path formats: token/filename on  Unix,
       token\filename  on Windows, and token:filename on the Mac), where token
       is representing one of the directories of the accessPath list and file-
       name  is  one  file  in	that  directory (no sub directories access are
       allowed).

       When a token is used in a safe interpreter in a request	to  source  or
       load  a	file,  the token is checked and translated to a real path name
       and the file to be sourced or loaded is located	on  the  file  system.
       The  safe  interpreter  never  gains  knowledge of the actual path name
       under which the file is stored on the file system.

       To further prevent potential information leakage from  sensitive  files
       that  are accidentally included in the set of files that can be sourced
       by a safe interpreter, the source alias restricts access to files meet-
       ing  the  following constraints: the file name must fourteen characters
       or shorter, must not contain more than one dot ("."), must end up  with
       the extension .tcl or be called tclIndex.

       Each  element  of the initial access path list will be assigned a token
       that will be set in the slave auto_path and the first element  of  that
       list will be set as the tcl_library for that slave.

       If  the	access	path  argument	is not given or is the empty list, the
       default behavior is to let the slave access the same  packages  as  the
       master  has  access to (Or to be more precise: only packages written in
       Tcl (which by definition can't be dangerous as they run	in  the  slave
       interpreter)  and  C extensions that provides a Safe_Init entry point).
       For that purpose, the master's auto_path will be used to construct  the
       slave  access path.  In order that the slave successfully loads the Tcl
       library files (which includes the auto-loading  mechanism  itself)  the
       tcl_library  will be added or moved to the first position if necessary,
       in the slave access path, so the slave tcl_library will be the same  as
       the  master's  (its  real  path	will  still  be invisible to the slave
       though).  In order that auto-loading works the same for the  slave  and
       the  master in this by default case, the first-level sub directories of
       each directory in the master auto_path  will  also  be  added  (if  not
       already	included)  to the slave access path.  You can always specify a
       more restrictive path for which sub directories will never be  searched
       by  explicitly specifying your directory list with the -accessPath flag
       instead of relying on this default mechanism.

       When the accessPath is changed after the first creation or  initializa-
       tion  (i.e. through interpConfigure -accessPath list), an auto_reset is
       automatically evaluated in the  safe  interpreter  to  synchronize  its
       auto_index with the new token list.


SEE ALSO
       interp(n), library(n), load(n), package(n), source(n), unknown(n)


KEYWORDS
       alias,  auto-loading,  auto_mkindex,  load,  master  interpreter,  safe
       interpreter, slave interpreter, source



Tcl				      8.0			   Safe Tcl(n)
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