Provided by: libtaint-runtime-perl_0.3-3build1_amd64 bug


       Taint::Runtime - Runtime enable taint checking


         ### sample "enable" usage

         #!/usr/bin/perl -w
         use Taint::Runtime qw(enable taint_env);
         # having the keyword enable in the import list starts taint

         ### sample $TAINT usage

         #!/usr/bin/perl -w
         use Taint::Runtime qw($TAINT taint_env);
         $TAINT = 1;

         # taint is now enabled

         if (1) {
           local $TAINT = 0;

           # do something we trust

         # back to an untrustwory area

         ### sample functional usage

         #!/usr/bin/perl -w
         use strict;
         use Taint::Runtime qw(taint_start is_tainted taint_env
                               taint untaint

         ### other operations here

         taint_start(); # taint should become active
         taint_env(); # %ENV was previously untainted

         print taint_enabled() ? "enabled\n" : "not enabled\n";

         my $var = taint("some string");

         print is_tainted($var) ? "tainted\n" : "not tainted\n";

         $var = untaint($var);
         # OR
         untaint \$var;

         print is_tainted($var) ? "tainted\n" : "not tainted\n";


       First - you probably shouldn't use this module to control taint.  You should probably use
       the -T switch on the commandline instead.  There are a somewhat limited number of
       legitimate use cases where you should use this module instead of the -T switch.  Unless
       you have a specific and good reason for not using the -T option, you should use the -T

       Taint is a good thing.  However, few people (that I work with or talk to or discuss items
       with) use taint even though they should.  The goal of this module isn't to use taint less,
       but to actually encourage its use more.  This module aims to make using taint as painless
       as possible (This can be an argument against it - often implementation of security implies
       pain - so taking away pain might lessen security - sort of).

       In general - the more secure your script needs to be - the earlier on in your program that
       tainting should be enabled.  For most setuid scripts, you should enable taint by using the
       -T switch.  Without doing so you allow for a non-root user to override @INC which allows
       for them to put their own module in the place of trusted modules.  This is bad.  This is
       very bad.  Use the -T switch.

       There are some common places where this module may be useful, and where most people don't
       use it.  One such place is in a web server.  The -T switch removes PERL5LIB and PERLLIB
       and '.' from @INC (or remove them before they can be added).  This makes sense under
       setuid.  The use of the -T switch in a CGI environment may cause a bit of a headache.  For
       new development, CGI scripts it may be possible to use the -T switch and for mod_perl
       environments there is the PerlTaint variable.  Both of these methods will enable taint and
       from that point on development should be done with taint.

       However, many (possibly most) perl web server implentations add their own paths to the
       PERL5LIB.  All CGI's and mod_perl scripts can then have access.  Using the -T switch
       throws a wrench into the works as suddenly PERL5LIB disappears (mod_perl can easily have
       the extra directories added again using <perl>push @INC, '/our/lib/dir';</perl>).  The
       company I work for has 200 plus user visible scripts mixed with some mod_perl.  Currently
       none of the scripts use taint.  We would like for them all to, but it is not feasible to
       make the change all at once.  Taint::Runtime allows for moving legacy scripts over one at
       a time.

       Again, if you are using setuid - don't use this script.

       If you are not using setuid and have reasons not to use the -T and are using this module,
       make sure that taint is enabled before processing any user data.  Also remember that
       taint_env() to mark it as tainted (especially important in CGI scripts which all read from

       If you are not using the -T switch, you most likely should use the following at the very
       top of your script:

         #!/usr/bin/perl -w

         use strict;
         use Taint::Runtime qw(enable taint_env);

       Though this module allows for you to turn taint off - you probably shouldn't.  This module
       is more for you to turn taint on - and once it is on it probably ought to stay on.


       The following very basic functions provide the base functionality.

           Sets PL_tainting

           Sets PL_tainting

           View of PL_tainting

           Returns a zero length tainted string.


       The variable $TAINT is tied to the current state of taint.  If $TAINT is set to 0 taint
       mode is off.  When it is set to 1 taint mode is enabled.

         if (1) {
           local $TAINT = 1;

           # taint is enabled


           Not really functions.  If these keywords are in the import list, taint will be either
           enabled or disabled.

           Start taint mode.  $TAINT will equal 1.

           Stop taint mode.  $TAINT will equal 0.

           Convenience function that taints the keys and values of %ENV.  If the -T switch was
           not used - you most likely should call this as soon as taint mode is enabled.

           Taints the passed in variable.  Only works on writeable scalar values.  If a scalar
           ref is passed in - it is modified.  If a scalar is passed in (non ref) it is copied,
           modified and returned.  If a value was undefined, it becomes a zero length defined and
           tainted string.


             my $tainted_copy = taint($some_var);

           For a stronger taint, see the Taint module by Dan Sulgalski which is capable of
           tainting most types of data.

           Untaints the passed in variable.  Only works on writeable scalar values.  If a scalar
           ref is passed in - it is modified.  If a scalar is passed in (non ref) it is copied,
           modified and returned.  If a value was undefined it becomes an untainted undefined

           Note:  Just because the variable is untainted, doesn't mean that it is safe.  You
           really should use CGI::Ex::Validate, or Data::FormValidator or any of the Untaint::
           modules.  If you are doing your own validation, and once you have put the user data
           through very strict checks, then you can use untaint.

             if ($var_to_be_untainted =~ /^[\w\.\-]{0,100}$/) {

             my $untainted_copy = untaint($some_var);

           Boolean - Is taint on.

           Returns a zero length tainted string.

           Boolean - True if the passed value is tainted.

           Convenience function that attempts to deply recurse a structure and mark it as
           tainted.  Takes a hashref, arrayref, scalar ref, or scalar and recursively untaints
           the structure.

           For a stronger taint, see the Taint module by Dan Sulgalski which is capable of
           tainting most types of data.


       (Be sure to call taint_env() after turning taint on the first time)

         #!/usr/bin/perl -T

         use Taint::Runtime qw(enable);
         # this does not create a function called enable - just starts taint

         use Taint::Runtime qw($TAINT);
         $TAINT = 1;

         use Taint::Runtime qw(taint_start);


         use Taint::Runtime qw(disable);
         # this does not create a function called disable - just stops taint

         use Taint::Runtime qw($TAINT);
         $TAINT = 0;

         use Taint::Runtime qw(taint_stop);


       C code was provided by "hv" on perlmonks.  This module wouldn't really be possible without
       insight into the internals that "hv" provided.  His post with the code was shown in this
       node on perlmonks:

       The basic premise in that node was the following code:

         use Inline C => 'void _start_taint() { PL_tainting = 1; }';
         use Inline C => 'SV* _tainted() { PL_tainted = 1; return newSVpvn("", 0); }';

       In this module, these two lines have instead been turned into XS for runtime speed (and so
       you won't need Inline and Parse::RecDescent).

       Note: even though "hv" provided the base code example, that doesn't mean that he
       necessarily endorses the idea.  If there are disagreements, quirks, annoyances or any
       other negative side effects with this module - blame me - not "hv."


       Thanks to Alexey A. Kiritchun for pointing out untaint failure on multiline strings.


       Paul Seamons (2005)

       C stub functions by "hv" on


       This module may be used and distributed under the same terms as Perl itself.