[perl #81028] Taintedness of the first operand of a ternary '?:' propagate to unrelated expr in the same list

# New Ticket Created by  Mark Martinec 
# Please include the string:  [perl #81028]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=81028 >


This is a bug report for perl from Mark.Martinec@ijs.si,
generated with the help of perlbug 1.39 running under perl 5.12.2.


-----------------------------------------------------------------
Taintedness of the first operand of a ternary '?:'
propagate to unrelated expressions in the same argument list.

The following test case will illustrate the issue:

#!/usr/bin/perl -T
use Scalar::Util qw(tainted);
my $clean = "ccc";  # not tainted
my $t = "ttt" . substr($0,0,0);  # tainted
sub a { print join(", ", map {tainted($_)?"Y":"n"} @_), "\n" };
a($t, $t?1:0, $clean, substr($clean,0,1), 0+$clean, $clean);

Y, n, n, Y, Y, n

I'm aware that taintedness propagation within an expressions
is rather simpleminded, nevertheless the above test case was
a surprise.

The variable $t is tainted, the $clean is not.

The ternary '?:' conditional operator nicely produces a
non-tainted result even if its first operand is tainted.

As expected the arguments $t?1:0 and $clean as passed
to the called subroutine are not tainted.

What is surprising is that substr($clean,0,1) and 0+$clean
are tainted, even though the $clean is not.

Can this be considered a bug? Can something be done
to restrict this case of a taintedness propagation?


[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.12.2:

Configured by mark at Wed Nov 17 21:05:55 CET 2010.

Summary of my perl5 (revision 5 version 12 subversion 2) configuration:
   
  Platform:
    osname=freebsd, osvers=8.1-release, archname=amd64-freebsd
    uname='freebsd neli.ijs.si 8.1-release freebsd 8.1-release #10: fri jul 30 15:39:39 cest 2010 mark@neli.ijs.si:usrobjusrsrcsysneli amd64 '
    config_args='-sde -Dprefix=/usr/local -Darchlib=/usr/local/lib/perl5/5.12.2/mach -Dprivlib=/usr/local/lib/perl5/5.12.2 -Dman3dir=/usr/local/lib/perl5/5.12.2/perl/man/man3 -Dman1dir=/usr/local/man/man1 -Dsitearch=/usr/local/lib/perl5/site_perl/5.12.2/mach -Dsitelib=/usr/local/lib/perl5/site_perl/5.12.2 -Dscriptdir=/usr/local/bin -Dsiteman3dir=/usr/local/lib/perl5/5.12.2/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Ui_malloc -Ui_iconv -Uinstallusrbinperl -Dcc=cc -Duseshrplib -Dinc_version_list=none -Dccflags=-DAPPLLIB_EXP="/usr/local/lib/perl5/5.12.2/BSDPAN" -Doptimize=-O2 -pipe -fno-strict-aliasing -Ui_gdbm -Dusethreads=n -Dusemymalloc=n -Duse64bitint'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-DAPPLLIB_EXP="/usr/local/lib/perl5/5.12.2/BSDPAN" -DHAS_FPSETMASK -DHAS_FLOATINGPOINT_H -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include',
    optimize='-O2 -pipe -fno-strict-aliasing',
    cppflags='-DAPPLLIB_EXP="/usr/local/lib/perl5/5.12.2/BSDPAN" -DHAS_FPSETMASK -DHAS_FLOATINGPOINT_H -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.2.1 20070719  [FreeBSD]', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -Wl,-E  -fstack-protector -L/usr/local/lib'
    libpth=/usr/lib /usr/local/lib
    libs=-lgdbm -lm -lcrypt -lutil
    perllibs=-lm -lcrypt -lutil
    libc=, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='  -Wl,-R/usr/local/lib/perl5/5.12.2/mach/CORE'
    cccdlflags='-DPIC -fPIC', lddlflags='-shared  -L/usr/local/lib -fstack-protector'

Locally applied patches:
    

---
@INC for perl 5.12.2:
    /usr/local/lib/perl5/5.12.2/BSDPAN
    /usr/local/lib/perl5/site_perl/5.12.2/mach
    /usr/local/lib/perl5/site_perl/5.12.2
    /usr/local/lib/perl5/5.12.2/mach
    /usr/local/lib/perl5/5.12.2
    .

---
Environment for perl 5.12.2:
    HOME=/home/mark
    LANG (unset)
    LANGUAGE=
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/bin:/usr/local/sbin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/kde4/bin/:/usr/local/kde4/sbin:/usr/X11R6/bin
    PERL_BADLANG (unset)
    SHELL=/usr/local/bin/bash

• [perl #81028] Taintedness of the first operand of a ternary '?:' propagate to unrelated expr in the same list by Mark Martinec
• Re: [perl #81028] Taintedness of the first operand of a ternary '?:'propagate to unrelated expr in the same list by Dave Mitchell