Chapter 1. Introduction to Access Manager components 15
For example, suppose a junction on the WebSEAL host www.abc.com is defined
such that a request for any URL specifying the path /content/xyz (relative to the
Web space root, of course) is to be proxied to the back-end Web server
def.internal.abc.com. /content/xyz is the
junction point, which can be thought of
in a loose sense as being similar in concept to a file system mount point.
A user at a browser then makes a request for
http://www.abc.com/content/xyz/myhtmlfiles/test.html; WebSEAL will examine
the URL and determine whether the request falls within the Web space for the
/content/xyz junction point. It will then proxy the request to def.internal.abc.com
and forward the resulting response back to the browser.
From the perspective of the browser, the request is processed by www.abc.com.
The fact that it is actually handled by the target server def.internal.abc.com is not
known to the user. To support this, WebSEAL performs various transformations
on the response sent to the browser to assure that the back-end server names
are not exposed. This exemplifies one of the powerful capabilities provided by
WebSEAL junctions, that is, the “virtualization of the Web space.” Junctions may
be defined to the individual Web spaces on various back-end servers, yet from
the browser’s point of view, there is only one single Web space.
It was hinted above that more than one target server may be defined for a
particular junction point. For example, the server ghi.internal.abc.com could be
defined as an additional target for the /content/xyz junction point. In this case,
WebSEAL can load-balance among the servers, and should a back-end server
be unavailable, WebSEAL can continue forwarding requests to the remaining
servers for the junction. For situations where it is important that subsequent
requests for a particular user continue going to the same back-end server,
WebSEAL is capable of supporting this via what are called
The above assumes that processing a request does not involve any security
considerations. While WebSEAL is capable of doing a fine job of simply
managing access to Web-based content and applications via simple junctions,
this, of course, leaves out a primary purpose of utilizing WebSEAL. Its integration
with the base Access Manager services to provide access control and flexible
authentication services for Web resources is its main reason for existence.
WebSEAL security functions
One of WebSEAL’s key functions is to protect access to Web content and
applications. To do this, it uses Access Manager’s Authorization Services. The
Authorization Service must know which Web objects (that is, URLs) require
protection, and what level(s) of access to these objects is permitted for the
Access Manager users and groups defined in the user registry.