Abstract:
In a protocol providing for authentication to a first security realm, but failing to provide for a logout operation to de-authenticate from the first security realm, a logout operation is effected by providing a logout button, hyperlink, or other linking construct that causes a user to be transparently authenticated to a second security realm. For example, with respect to HTTP basic authentication, authentication with the second security realm removes, or logs out, the user from the first security realm.

Description:
FIELD OF THE INVENTION 
   The invention generally relates to logoff authentication, and more particularly to de-authentication from access privileges granted by a HyperText Transport Protocol (HTTP) basic authentication. 
   BACKGROUND 
   Certain communication protocols only provide a login authentication dialog on accessing a particular resource, and do not provide a logout or de-authentication method to remove authentication. For such protocols, once a user is authenticated, the user remains authenticated. This restricts the ability to allow multiple users to share a common access point utilizing such a limited protocol. 
   A well-known protocol having this authentication limitation is HTTP. HTTP provides a basic authentication scheme, in which a web page designer may assign user name/password pairs to particular web resources. One typical technique for triggering authentication dialog boxes is through use of the .htaccess and .htpasswd files utilized by Apache web severs (well-known public-domain Web servers). When a user attempts to access a protected resource, such as with a web browser, the htaccess file tells the web server to instruct the user&#39;s browser to display an authentication dialog comprising a user name and password field. The user must then supply credentials that match the .htpasswd file. If the user provides proper credentials, the user is then allowed access to the resource. 
   Unfortunately, HTTP fails to provide a de-authentication ability for a web browser session. That is, one cannot secure a web site with HTTP basic authentication, and then let multiple users access the site with a single web browser running on a public terminal. This configuration fails because, under basic HTTP authentication, once a first user is authenticated, then the browser session remains authenticated until the web browser session, e.g., the browser window, is closed. This limitation has resulted in having to provide HTTP extensions for logging users into and out of web resources, e.g., by way of Common Gateway Interface (CGI) scripts, Java applets, etc. 
   This limitation may also preclude use of HTTP basic authentication in circumstances where a browser session cannot be closed. For example, terminals having a web browser embedded in Read Only Memory (ROM), or browsers that are integrated into an operating system, may lack a provision for being restarted, and therefore require rebooting or powering cycling to de-authenticate a browser&#39;s session. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become apparent from the following detailed description of the present invention in which: 
       FIG. 1  and  FIG. 2  illustrate a generalized computing environment in which multiple users use a common access point to access a web page. 
       FIG. 2  illustrates a flowchart according to one embodiment for overcoming authentication for a generic authentication protocol. 
       FIG. 3  illustrates a flowchart, according to one embodiment, for overcoming authentication for the HTTP basic authentication protocol. 
       FIG. 4  illustrates a suitable computing environment in which certain aspects of the invention may be implemented. 
   

   DETAILED DESCRIPTION 
     FIG. 1A  illustrates a generalized computing environment in which multiple users  100  use a common access point  102 , such as a network appliance, computer, or other network access device, to access exemplary network resources  104 ,  106  provided by a server  108 . In one embodiment, the web resources are two web pages, and the server a web server, however it will be appreciated that other network elements may be used. 
   Multiple users share the common access point. In one embodiment, a web browser  110  executes on the access point, and the browser is used by users  100  to access an initial web page  104 . In the illustrated embodiment, the web page  104  comprises a login button  114  for authenticating user attempts to access a protected resource  106 . It will be appreciated by one skilled in the art that other linking techniques may also be used, e.g., hyperlinks, etc. Assuming HTTP basic authentication protects access to the protected resource  106 , selection of the button  112  triggers display of an HTTP basic authentication dialog box, see, e.g.,  FIG. 1B  exemplary dialog box  150 , to the user of the common access point  102 . 
   When a user enters valid credentials into the authentication dialog  150 , the web browser  110  loads the protected resource  106 . As illustrated, the protected resource comprises a logout button  112  to de-authenticate the user. As discussed above, no such feature is presently available with HTTP basic authentication. However, as discussed below, multiple security realms can be used to implement de-authentication. 
   For example, one security realm can be associated with the protected resource  106 , such that selecting the login button  112  allows a user  100  of the common access point  102  to be authenticated to that first security realm on providing proper credentials. Another security realm can be associated with the logout button  114 , such that selecting the logout button causes the user to be transparently and automatically authenticated with the other security realm. As will be appreciated by one skilled in the art, under HTTP basic authentication, authentication with another security realm invalidates the first authentication. As will be more clear with reference to the  FIG. 2  flowchart below, this invalidation effects a logout operation from the protected resource&#39;s security realm. 
     FIG. 2  is a flowchart generally illustrating the use of two security realms to effect a logout from HTTP basic authentication. 
   As illustrated, a user first accesses  200  a web browser or other network access program operating on a common access point. Assume the web browser defaults to displaying  202  a login page comprising a login button for accessing a protected resource. In the illustrated embodiment, the login page belongs in a first security realm that is generally accessible to all users of the common access point, e.g., the first security realm has no password protection, or has a public password (see, e.g.,  FIG. 3 ). The protected resource, however, belongs to a private second security realm, where non-public credentials (e.g., user names and/or password pairs) are required to access the protected resource. 
   The user selects  204  the login button to access the protected resource of the second security realm. The protected resource is protected by HTTP basic authentication, e.g., by way of .htaccess/.htpasswd files, or another authentication system having comparable limitations of HTTP basic authentication. In one embodiment, selecting  204  the login button causes the browser to attempt to access  206  the protected resource. Then, due to the HTTP basic authentication protection, attempted access triggers a request  208  for authentication credentials, e.g., an authentication dialog box such as in  FIG. 1B  is provided to the user for filling out. 
   The user then provides  210  appropriate credentials within the authentication dialog box. Note that providing credentials depends on the nature of the authentication system employed. For example,  FIG. 1B  assumes HTTP basic authentication obtains credentials by way of entry into a conventional data entry dialog box. However, it will be appreciated that other authentication techniques may be employed. For example, authentication may include analysis of and/or comparisons between a user&#39;s biometric data, e.g., physical characteristics, fingerprints, retina patterns, body characteristics, voice analysis, etc. 
   Once appropriate credentials are provided, the user is authenticated  212  with the second security realm. The browser is then allowed to access  214  the protected resource of the second security realm. For example, if the protected resource is a web page, the user is allowed to interact with the protected web page. Note that many web pages, or other network resources, may be within the second security realm, allowing the user unrestricted access to these resources once initial authentication is completed. 
   Within a protected resource, a logout button is displayed  216 . On selection  218  thereof by a user, the user is automatically authenticated  220  with a second security realm. As discussed above, HTTP basic authentication does not provide for de-authenticating from the second security realm. However, HTTP basic authentication only provides for one current security realm authentication. By authenticating with the first security realm, the user is de-authenticated from the second security realm. In such fashion, a single browser session of a common access point may be shared among multiple users, where each user may have their own credentials for accessing protected resources. When a user session is complete, a user may logout back to the login page  202  and leave the common access point ready for a subsequent user. 
     FIG. 3  illustrates an exemplary Common Gateway Interface (CGI) application  300  for de-authenticating a user from a second security realm by transparently redirecting the user to a login web page in the first security realm. 
   In this embodiment, the logout button of  FIG. 1  and  FIG. 2  is configured to cause a user&#39;s browser to load logout.cgi, a CGI application operating on the server hosting the protected resource. The illustrated CGI application is a Practical Extraction and Report Language (Perl) script that loads the resource of the first security realm. It will be appreciated that other script and non-script embodiments may perform the operations of the illustrated Perl script. In one embodiment, a user name and password is associated with the login page of the first security realm. Appropriate user name and password values are passed as parameters to the CGI application. 
   In one embodiment, the logout button is configured with a HyperText Transfer Protocol (HTTP) link to the logout.cgi resource, where the link includes authentication credentials as parameters to calling logout.cgi. As will be understood by one skilled in the art, the CGI application receives the user name and password parameters, and passes them on to the host server for validation. For example, if the server operates the Apache web server, then the credentials are compared against appropriate .htaccess/.htpasswd files. 
   In another embodiment, the first security realm can be server-side configured to not require passing of a user name or password, and therefore the login page can be simply loaded to effect authentication with the first security realm. In one embodiment, the user name for the first security realm (the main page for the public access point) must be assigned a globally unique name to ensure no inadvertent authentication into the second security realm. 
     FIG. 4  and the following discussion are intended to provide a brief, general description of a suitable computing environment in which certain aspects of the illustrated invention may be implemented. For example, an exemplary system for embodying the common access point  102  or web server  108  of  FIG. 1  includes a machine  400  having system bus  402  for coupling various machine components. 
   Typically, attached to the bus are processors  404 , a memory  406  (e.g., RAM, ROM), storage devices  408 , a video interface  410 , and input/output interface ports  412 . The machine may also include embedded controllers, such as Programmable Logic Devices or Arrays (PLD, PLA), Generic or Programmable Array Logic (GAL, PAL), Field-Programmable Gate Arrays (FPGA), Application Specific Integrated Circuits (ASIC), single-chip computers, smart cards, etc. 
   The machine is expected to operate in a networked environment using logical connections to one or more remote machines  414 ,  416  through a network interface  418 , modem  420 , or other communication pathway. Machines may be interconnected by way of a wired or wireless network  422 , including an intranet, the Internet, local area networks, wide area networks, cellular, cable, laser, satellite, microwave, Blue Tooth, optical, infrared, or other carrier technology. 
   The invention may be described by reference to program modules that may be stored in memory  406  and/or storage devices  408 . Program modules include procedures, functions, programs, components, data structures, and the like, for performing particular tasks or implementing particular abstract data types. One skilled in the art will realize that program modules may be high-level programming language constructs, or low-level hardware instructions and/or contexts, and that they may be utilized in a compressed or encrypted format. Data may be stored in memory  406 , storage devices  408 , and associated media. 
   Program modules may be implemented within a single machine, or processed in a distributed network environment, and be stored in both local and remote memory. Memory and storage devices include hard-drives, floppy-disks, optical storage, magnetic cassettes, tapes, flash memory cards, memory sticks, digital video disks, biological storage, and the like, as well as wired and wireless transmission environments, such as network  422 , over which program modules may be delivered in the form of packets, serial data, parallel data, or other suitable transmission format. 
   Thus, for example, with respect to the illustrated embodiments, assuming machine  400  operates as the common access point  102 , then remote devices  414 ,  416  may other common access points or web servers. It will be appreciated that remote machines  414 ,  416  may be configured like machine  400 , and therefore include many or all of the elements discussed for machine. It should also be appreciated that machines  400 ,  414 ,  416  may be embodied within a single device, or separate communicatively-coupled components. 
   Illustrated methods, and corresponding written descriptions thereof, are intended to illustrate machine-accessible media storing directives, or the like, which may be incorporated into single and multi-processor machines, portable computers, such as handheld devices including Personal Digital Assistants (PDAs), cellular telephones, and the like. Having described and illustrated the principles of the invention with reference to illustrated embodiments, it will be recognized that the illustrated embodiments can be modified in arrangement and detail without departing from such principles. 
   And, even though the foregoing discussion has focused on particular embodiments, it is understood that other configurations are contemplated. In particular, even though expressions such as “in one embodiment,” “in another embodiment,” or the like are used herein, these phrases are meant to generally reference embodiment possibilities, and are not intended to limit the invention to particular embodiment configurations. As used herein, these terms may reference the same or different embodiments, and unless implicitly or expressly indicated otherwise, embodiments are combinable into other embodiments. Consequently, in view of the wide variety of permutations to the above-described embodiments, the detailed description is intended to be illustrative only, and should not be taken as limiting the scope of the invention. 
   What is claimed as the invention, therefore, is all such modifications as may come within the scope and spirit of the following claims and equivalents thereto.