và số byte mà không được đọc. Bạn kiểm tra tài sản timed_out trong kịch bản của bạn để xác định xem kết nối đã có thời gian tự động đổi kiểu của nó cho phép bạn để xác định xem đó chuỗi mà người dùng nhập vào là có khả năng được hiểu là số (vì nó sẽ có thể được sử dụng của bạn script). | 184 CHAPTER 9 CONTROLLING ACCESS I AUTHENTICATION username and password. Basic Authentication over unencrypted networks should therefore be used only in cases where modest security will suffice such as applications that are more-or-less public but need to be reasonably able to attribute actions or access to a particular user. A great example of this is an application such as a photo manipulator that stores no actual copies of photos or any other privacy-related data but that is greatly enhanced by allowing users to save preferences from session to session and access them again on different computers. HTTP Digest Authentication RFC2068 which defines HTTP available at http was issued in January 1997 just seven months after RFC 1945 and it carried over the Basic Authentication specification from the earlier version. But it also explicitly allowed for extensions to the protocol s authentication methods and it introduced HTTP Digest Authentication referring the reader to RFC2069 available at http for a complete description. HTTP Digest Authentication is capable of protecting a user s password in transit over even an unencrypted network by including it in a message digest that has been hashed with the md5 function. Digest Authentication is handled by Apache s experimental mod_auth_digest module see http docs mod as follows 1. A client requests a protected resource. 2. The server sends back a 401 Unauthorized header along with a WWW-Authenticate Digest header with Basic Authentication it was a WWW-Authenticate Basic header that includes a nonce or a number used once. A nonce is typically a client IP address concatenated with a timestamp and some sort of private key or data known only to the server all expressed in hexadecimal format. 3. The client after collecting a username and password from the user sends back a second request for authentication. This request is in the form of an .
