i recently upgraded an old redhat 7.2 box to perl 5.8.4 (from 5.8.0) and have encountered some weirdness with taint-checking and IO::Socket. here's the smallest test-case i could come up with:

i have the following XML file:

<?xml version="1.0"?>
<settings>
    <base>http://www.google.com</base>
</settings>

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and the following perl:

#!/usr/bin/perl -wT

use strict;
use LWP::Simple;
use XML::Simple;

my $config = XML::Simple::XMLin("test.xml");

my $base = $config->{base};

if ($base =~ m{^(http://[\w\.\/\-]+)$}) {
    $base = $1;
} else {
    print $base, " didn't match\n";
}

print get("$base/index.html");

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when i run it under perl 5.8.4, i get:

Insecure dependency in connect while running with -T switch at /usr/lo
+cal/lib/perl5/5.8.4/i686-linux/IO/Socket.pm line 114.

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if i run it under 5.8.0, it works as expected.

so how on earth does it still consider $base to be tainted? it passes through the conditional without printing anything, so it certainly looks like it should be untainted.

if i don't get $base through XML::Simple, and instead just say $base = "http://www.google.com", it works. if i don't do any string interpolation in the last line it works. ie, if i change the last line to just: 

print get($base);

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it works.

it looks like some Twiki users have encountered the same problem but haven't found any solution other than turning off taint-checking (which i don't consider a legitimate option on a public server).

so is this a perl bug, or am i missing something really stupid and obvious? can anyone else duplicate it?

anders pearson

In reply to perl 5.8.4, IO::Socket, and taint checking by thraxil

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