Rewrite the perl finger CGI script shown in Figure to include both appropriate input valid...

Rewrite the perl finger CGI script shown in Figure to include both appropriate input validation and more informative error messages, as suggested by footnote 3 in Section 11.2. Extend the input validation to also permit any of the characters −+% in the middle of $user value, but not at either the start or end of this value. Consider the implications of further permitting space or tab characters within this value. Because such values separate arguments to a shell command, the $user value must be surrounded by the correct quote characters when passed to the finger command. Determine how this is done. If possible, copy your modified script, and the form used to call it, to a suitable Linux/UNIX-hosted Web server, and verify its correct operation.

Figure A Web CGI Injection Attack