CVE-2012-1823 mitigation wrapper

#!/usr/bin/perl

use warnings;
use strict;

use File::Copy;

my $gcc = '/usr/bin/gcc';

my $tempfile = "/var/tmp/$$.c";

my $c = <<CPROG;
/*
 * Small wrapper which strips all arguments to invocations
 * of php-cgi when it is called as a normal CGI handler.
 * This prevents attackers to pass arguments from the query
 * string as defined in RFC 3875. [1]
 *
 * [1] http://www.ietf.org/rfc/rfc3875
 *
 */

#include <sys/socket.h>
#include <sys/un.h>
#include <netinet/in.h>

#include <unistd.h>
#include <errno.h>

#define PHP_ORIG "REALPATH" /* Original binary */

typedef union _sa_t {
    struct sockaddr     sa;
    struct sockaddr_un  sa_unix;
    struct sockaddr_in  sa_inet;
    /* struct sockaddr_in6 should probably be here as well,
     * doesn't matter though, since struct sockaddr_un
     * is big.
     */
} sa_t;

int is_fastcgi(void)
{
    sa_t sa;
    socklen_t len = sizeof(sa);

    return ( getpeername(0, (struct sockaddr *)&sa, &len) != 0 &&
             errno == ENOTCONN );
}

int main(int argc, char **argv)
{
    /* mimic php's cgi detection */
    if ( !is_fastcgi() &&
         (getenv("SERVER_SOFTWARE") ||
          getenv("SERVER_NAME") ||
          getenv("GATEWAY_INTERFACE") ||
          getenv("REQUEST_METHOD") ) )
      argv[1] = NULL;

    execv(PHP_ORIG, argv);
}

CPROG

#print $c;

while (<STDIN>) {
    chomp;
    my $orig = $_;
    my $real = "${orig}.real";
    if ( -e $orig ) {
        my $prog = $c;
        $prog =~ s,REALPATH,$real,gs;
        if ( move( $orig, $real ) ) {
            open my $f, '>', $tempfile;
            print $f $prog;
            close $f;
        my $fh;
            if ( open( $fh, '-|', $gcc, '-o', $orig, $tempfile ) ) {

                #fine
            }
            else {
                print STDERR "problem compiling $orig, moving on.\n";
                next;
            }
            close $fh;
        }
        else {
            print STDERR "problem moving $orig, moving on.\n";
            next;
        }
    }
    else {
        print STDERR "$orig does not exist, moving on.\n";
        next;
    }
}