First, consider turning taint mode on, which will stop your program if it is about to use unfiltered data. Doing that will force you to decide what is and isn't an allowed character before you can do anything dangerous with a user-supplied string.

Once you've done that, make sure the pattern you use to untaint doesn't allow null characters. For example: 

  my $filename;
  if ($param('select') =~ /^(\w+)$/)
  {
    $filename = $1;
  }
  else
  {
    die "Illegal filename!\n";
  }

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sgifford's Web page

In reply to Re: How to avoid Null Byte Injection? by sgifford
in thread How to avoid Null Byte Injection? by Nik

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