#!/usr/bin/perl -wT
use strict;
use MIME::Base64;

my $file_in = 'base64data';

### get variables
chomp (my $file_out = <STDIN>);
my $data_enc;
my $data_unenc;

$ENV{PATH} = "";

### check file_in
unless ($file_in =~ /^[\w][\w\._-]*$/) {
    print "Insecure file_in\n";
    exit;
}
if ($file_in =~ /^\.{2,}$/) {
    print "Insecure file_in path\n";
    exit;
}

### untaint file_out
unless ($file_out =~ /[\w][\w\._-]*$/) {
    print "Insecure file_out\n";
    exit;
}
if ($file_out =~ /^\.{2,}$/) {
    print "Insecure file_out path\n";
    exit;
}

### get the data from input_file
open (FILEIN, "< $file_in")
    or die "Couldn't open input file:\n$!\n";

while (<FILEIN>) {
    $data_enc .= $_;
}

close (FILEIN);

### unencode the data
$data_unenc = decode_base64($data_enc);

### write the data to the output file
open (FILEOUT, "> $file_out")
    or die "Couldn't create output file:\n$!\n";

print FILEOUT $data_unenc;

close (FILEOUT);

### finish
print "Operation successful.\n";

exit;
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