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Cisco ASA 5500 Series Configuration Guide using ASDM
Chapter72 Configuring Clientless SSL VPN
Configuring Application Helper
Figure72-3 SSO Authentication Using HTTP Forms
While you would expect to configure form parameters that let the ASA include POST data such as the
username and password, you initially might not be aware of additional hidden parameters that the web
server requires. Some authentication applications expect hidden data which is neither visible to nor
entered by the user. You can, however, discover hidden parameters the authenticating web server expects
by making a direct authentication request to the web server from your browser without the ASA in the
middle acting as a proxy. Analyzing the web server response using an HTTP header analyzer reveals
hidden parameters in a format similar to the following:
<param name>=<URL encoded value>&<param name>=<URL encoded>
Some hidden parameters are mandatory and some are optional. If the web server requires data for a
hidden parameter, it rejects any authentication POST request that omits that data. Because a header
analyzer does not tell you if a hidden parameter is mandatory or not, we recommend that you include all
hidden parameters until you determine which are mandatory.
Gathering HTTP Form Data
This section presents the steps for discovering and gathering necessary HTTP Form data. If you do not
know what parameters the authenticating web server requires, you can gather parameter data by
analyzing an authentication exchange using the following steps:
Prerequisites
These steps require a browser and an HTTP header analyzer.
Detailed Steps
Step1 Start your browser and HTTP header analyzer, and connect directly to the web server login page without
going through the ASA.
Step2 After the web server login page has loaded in your browser, examine the login sequence to determine if
a cookie is being set during the exchange. If the web server has loaded a cookie with the login page,
configure this login page URL as the start-URL.
Step3 Enter the username and password to log in to the web server, and press Enter. This action generates the
authentication POST request that you examine using the HTTP header analyzer.
An example POST request—with host HTTP header and body—follows:
148147
Web VPN
server

1

4

5

5

3

2Auth Web
server
Other protected
web server
Tunnel