webfs: buffer overflows, file and directory exposure

CAN-2003-0832 - When virtual hosting is enabled, a remote client could specify ".." as the hostname in a request, allowing retrieval of directory listings or files above the document root.

CAN-2003-0833 - A long pathname could overflow a buffer allocated on the stack, allowing execution of arbitrary code. In order to exploit this vulnerability, it would be necessary to be able to create directories on the server in a location which could be accessed by the web server. In conjunction with CAN-2003-0832, this could be a world-writable directory such as /var/tmp.