Customizing Web application login

You can create a form login page and an error page to authenticate a user. A Web client or a browser can authenticate a user to a Web server using one of the following mechanisms:

• HTTP basic authentication: A Web server requests the Web client to authenticate and the Web client passes a user ID and a password in the HTTP header.

• HTTPS client authentication: This mechanism requires a user (Web client) to possess a public key certificate. The Web client sends the certificate to a Web server that requests the client certificates. This authentication mechanism is strong and uses the Hypertext Transfer Protocol with Secure Sockets Layer (HTTPS) protocol.

• Form-based Authentication: A developer controls the look and feel of the login screens using this authentication mechanism.

The Hypertext Transfer Protocol (HTTP) basic authentication transmits a user password from the Web client to the Web server in simple base64 encoding. Form-based authentication transmits a user password from the browser to the Web server in plain text. Therefore, both HTTP basic authentication and form-based authentication are not very secure unless the HTTPS protocol is used.

The Web application deployment descriptor contains information about which authentication mechanism to use. When form-based authentication is used, the deployment descriptor also contains entries for login and error pages. A login page can be either an HTML page or a JavaServer Pages file. This login page displays on the Web client side when a secured resource (servlet, JSP file, HTML page) is accessed from the application. On authentication failure, an error page displays. You can write login and error pages to suit the application needs and control the look and feel of these pages. During assembly of the application, an assembler can set the authentication mechanism for the application and set the login and error pages in the deployment descriptor. Form login uses the servlet sendRedirect method, which has several implications for the user. The sendRedirect method is used twice during form login:

• The sendRedirect method initially displays the form login page in the Web browser. It later redirects the Web browser back to the originally requested protected page. The sendRedirect(String URL) method tells the Web browser to use the HTTP GET request to get the page that is specified in the Web address. If HTTP POST is the first request to a protected servlet or JavaServer Pages file, and no previous authentication or login occurred, then HTTP POST is not delivered to the requested page. However, HTTP GET is delivered because form login uses the sendRedirect method, which behaves as an HTTP GET request that tries to display a requested page after a login occurs.

• Using HTTP POST, you might experience a scenario where an unprotected HTML form collects data from users and then posts this data to protected servlets or JSP files for processing, but the users are not logged in for the resource. To avoid this scenario, structure your Web application or permissions so that users are forced to use a form login page before the application performs any HTTP POST actions to protected servlets or JSP files.

Procedure

1. Create a form login page with the required look and feel, including the required elements to perform form-based authentication. For an example, see Example: Form login.

2. Create an error page. You can program error pages to retry authentication or to display an appropriate error message.

3. Place the login page and error page in the Web archive (.war) file relative to the top directory. For example, if the login page is configured as /login.html in the deployment descriptor, place it in the top directory of the WAR file. An assembler can also perform this step using the assembly tool.

4. Create a form logout page and insert it to the application only when the Web application requires a form-based authentication mechanism.

Example

See the Example: Form login article for sample form login pages. The WebSphere Application Server Samples Gallery provides a form login Sample that demonstrates how to use the WebSphere Application Server login facilities to implement and configure form login procedures. The Sample integrates the following technologies to demonstrate the WebSphere Application Server and Java 2 Platform, Enterprise Edition (J2EE) login functionality:

• J2EE form-based login

• J2EE servlet filter with login

• IBM extension: form-based login

The form login sample is part of the Technology Samples package. For more information on how to access the form login sample, see Accessing Samples.

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