w3_2_Basic_Authentication

Basic Authentication
-------------------
HTTP Basic Access Authentication
----------------------------------
-> Method for HTTP user agent to provide username and password with a request;
-> Server can challenge a client to authenticate itself;
-> Client needs to send a response;

Client                                                                Server
  |                                                                     |
  |   -----Initiates request--->                                        |
  
    <---HTTP/1.1 401 UNAUTHORIZED  WWW-Authenticate : Basic ----------  |
    
    -->---Get/index.html HTTP/1.1 ----Authorization : Basic (Base64 encoded string)- Host: www.....com -------->
    
  Authorization Header
  -------------------------
  -> Authorization Header is constructed as follows:
  1. Username and password are combined into a string "username:password".
  2. The resulring string literal is then encoded using Base64;
  3. The authorization method and a space, i.e. "Basic" is put before the encoded string;
  
  Authorization: Basic (Base64 Encoded string);
  
  Express and Authentication
  ---------------------------
  
  Express application is structured as a sequence of middleware that are executed in a sequence one after another;
  Middleware
      |
      |
     \ /
  Middleware
      |
      |
     \ /
  Authentication Middleware-----
      |Authenticated            |
      |Next();                  |
     \ /                        |Not Authenticated
   Middleware                   |Next(error);
      |                         |
      |                        \ /
     \ /                    Error Handler
   Middleware