Impostor has been written in Java and was designed to be extensible and
pluggable. This means that it can easily extended to support additional or
different websites, user credential databases, challenge/response mechanisms and
content filtering behaviors. The Impostor proxy daemon (the core service)
consists of Java "classes" in the Java "package" named impostor.
The daemon requires four components (i.e. other Java classes) to exist in the
so-called "unnamed" package. Each of these four supporting components
needs to implement a particular Java "interface" in order to provide
the functionality expected by the daemon. As a developer, you have to write
classes implementing these interfaces in order to extend/modify Impostor's
behavior.
The four Java interfaces are the following:
RequestRecognizer: This component is responsible for
recognizing and filling in HTTP requests that constitute login requests for websites. The set of
SSO-enables websites is defined as the set of websites for which the RequestRecognizer component
recognizes login requests. The RequestRecognizer component is active in step 1 of
the figure (as it identifies a login request) and in step 3 (as it "fills in" the request such that it results in the user being logged into the website).
A developer needs to implement this interface in order to extend the set of SSO-enabled websites.
ChallengeReponseManager: This component is responsible for creating challenges (which are issued in step 2.1 of
the figure), checking whether a given Impostor username
is valid, and checking whether or not the response to a given challenge is valid (step 2.2).
A developer needs to implement this interface in order to make Impostor use
a particular challenge/response mechanism.
UserManager: This component provides the mapping between the
username of any given Impostor user and his/her website-specific authentication credentials (which are typically username/password pairs). The
UserManager component is active in step 3 of the
figure, as it is used to acquire the user's website-specific
authentication credentials. In other words, this component implements
Impostor's credential database. A developer can make Impostor use the
credential database of his/her choice by implementing this interface.
ContentFilter: This component provides the service of content filtering in step 4
of the figure. It is supposed to look for sensitive
information that should not be sent to the user's machine and (optionally)
replace it with other data. In order to change Impostor's content filtering
bahavior, a developer needs to implement this interface.
For exact definitions you can also have a look at the Java API.
