Method and system for restricting access to user resources

Abstract

A user's set top box (STB), or other client, executes a shell and has an application programming interface (API) by which certain features of the client can be controlled. The client is in communication with a walled garden proxy server (WGPS), which controls access to a walled garden. The walled garden contains links to one or more servers providing network-based services. The client sends a request to the WGPS to access a service provided by a site in the garden. To provide the service, the site sends the client a message containing code calling a function in the API. The WGPS traps the message from the site and looks up the site in a table to determine the access control list (ACL) for the site. The ACL is a bit-map that specifies which functions of the client's API can be invoked by code from the site. The WGPS includes the ACL in the header of the hypertext transport protocol (HTTP) message to the client. The shell receives the message and extracts the ACL. The shell uses the ACL to determine whether the code has permission to execute any called functions in the API. If the code lacks permission, the shell stops execution and sends a message to the site indicating that the site lacks permission. Otherwise, the shell allows the code to call the function.

Claims

We claim:

1. A computer program product comprising:

a computer usable medium having computer readable code embodied therein for passing messages from a server to a client, the computer program product comprising:

a first module for receiving a message from the server intended for the client;

a second module for determining permissions of the server with respect to the client;

a third module for including the determined permissions with the message; and

a fourth module for passing the message and the determined permissions to the client.

2. The computer program product of claim 1, wherein the second module comprises:

a module for determining an identity of the server originating the message;

a module for determining a user agent of the client; and

a module for retrieving the permissions of the server from a permissions table using the determined identity and user agent.

3. The computer program product of claim 2, wherein the permissions table is stored in a database and the module for retrieving the permissions of the server comprises:

a module for interfacing with the database to access the permissions table.

4. The computer program product of claim 1, wherein the third module comprises:

a module for adding a hypertext transport protocol (HTTP) header specifying the determined permissions to the message.

5. The computer program product of claim 1, further comprising:

a fifth module for scanning the message from the server for potential security violations.

6. The computer program product of claim 5, further comprising:

a sixth module for removing headers identified as potential security violations from the message.

7. A computer program product comprising:

a computer usable medium having computer readable code embodied therein for managing access to an application program interface (API) comprising a plurality of functions, the computer program product comprising:

a first module for receiving a message containing code calling a function in the API and an access control list (ACL) indicating API function execution rights of an originator of the message;

a second module for determining whether the ACL indicates that the originator of the message has die right to execute tie called function; and

a third module for sending a response to the originator of the message indicating whether the code successfully called the function.

8. The computer program product of claim 7, wherein the ACL indicating API function execution rights comprises:

a value identifying API functions that can be executed by the originator of the message.

9. The computer program product of claim 7, wherein the ACL indicating API function execution rights comprises:

a value restricting the API functions that can be executed by the originator of the message based on time.

10. The computer program product of claim 7, wherein the message pertains to television and wherein the ACL indicating API function execution rights comprises:

a value restricting the API functions that can be executed by the originator of the message based on a television channel.

11. The computer program product of claim 7, wherein the message pertains to television and wherein the ACL indicating APT function execution rights comprises:

a value restricting the API functions that can be executed by the originator of the message based on a television network.

12. A system comprising:

a client having an application programing interface (API) having functions for controlling resources of the client;

a walled garden having at least one walled garden site for sending a message to the client, the message containing code for calling a function in the API; and

a proxy server in communication with the client and the walled garden for receiving the message from the walled garden site, adding an access control list (ACL) to the message specifying which functions in the API the walled garden site has permission to call, and passing the message and ACL to the client.

13. The system of claim 12, further comprising:

a module in the client for interpreting the ACL to determine whether the walled garden site has permission to call the function in the API.

14. The system of claim 13, further comprising:

a module in the client for sending a message to the walled garden site indicating a result of the function call by the code in the message.

15. The system of claim 12, further comprising:

a database in communication with the proxy server for holding a walled garden permissions table holding the ACL for the at least one walled garden site.

16. The system of claim 12, wherein the walled garden site, proxy server, and client communicate using the hypertext transport protocol (HTTP) and the proxy server adds the ACL as a HTTP header to the message from the walled garden site.

17. The system of claim 16, wherein the proxy server examines the message from the walled garden site for potential security violations.

18. The system of claim 17, wherein the proxy server removes any HTTP headers identified as potential security violations from the message.

19. The system of claim 12, wherein the client is a set top box in communication with a display and wherein the APT functions comprise functions for controlling images on the display.

20. The system of claim 12, wherein the API functions comprise functions for performing electronic commerce transactions at the client.

21. The system of claim 12, wherein the API functions comprise functions for accessing an electronic program guide stored at the client.

Description

BACKGROUND

1. Field of the Invention

This invention pertains in general to high-speed data networks and in particular to a system and method for restricting access by servers on the network to resources available on user computer systems.

2. Background of the Invention

Cable television service is usually sold as a subscription to one or more "tiers" of channels. Typically, a basic cable subscription allows access to a small tier of channels and is sold for a relatively low subscription fee. The subscriber can purchase additional tiers of cable channels for additional fees.

In most cable systems, the subscriber uses a "set-top box" (STB) to access the cable channels. The STB contains a microprocessor and other hardware for tuning and descrambling channels in the tiers to which the subscriber has access. The STB may also enable other services, such as pay-per-view or digital music reception in return for additional fees.

In recent years, the STB has incorporated a cable modem that enables access to Internet- and World Wide Web- ("the web") based resources via the cable infrastructure. A cable modem typically has at least one assigned Internet Protocol (IP) address and is managed by an Internet Service Provider (ISP). The ISP inserts and extracts Internet traffic to and from the cable infrastructure and distributes it to the cable modem having the given IP address or the Internet, as appropriate.

U.S. patent application Ser. No. 09/428,235 discloses a walled garden accessible to STB users who are customers of the ISP. Application servers within the walled garden provide services to the users, including, for example, access to electronic content, access to electronic commerce services, and any other functionality that can be provided electronically via a network. The users can subscribe to one or more of the services in the walled garden either individually or as part of a tier. U.S. patent application Ser. No. 09/428,235 discloses a way to restrict users to only those services in the walled garden to which the users are entitled to access.

The walled garden application servers may desire or need to access features of the users' STBs in order to provide certain services. For example, an application server may need to generate text or controls on a user's television display, change the channel to which the STB is tuned, print a receipt on a printer coupled to the STB, or complete a fee transaction using an electronic wallet stored in the STB.

The ISP would prefer to limit the features on the users' STBs to which the application servers have access, typically to generate revenue and enhance security. For example, the ISP may desire to charge a fee for letting an application server change the channel to which the user's STB is tuned or conduct an electronic commerce transaction using the electronic wallet. Likewise, the ISP would like to limit the abilities of the application server to ensure that a misbehaving or compromised application server cannot act maliciously toward a user's STB.

Accordingly, there is a need for away to restrict the features of a user's STB that can be accessed and utilized by an application server within the walled garden. Preferably, the solution to this need will restrict the features at a fine grain, thereby allowing an application server to access only those features which are necessary to provide the service sought by the user.

SUMMARY OF THE INVENTION

The above needs are met by a method and system that passes an access control list (ACL) to the set top box (STB), or other form of client, indicating which functions in the client can be called by a walled garden site. A client is coupled to a television set, computer system, or other device having a display. The client preferably contains a central processing unit, a memory, a television tuner, and a cable modem. The client also preferably contains a video subsystem, for generating images on the display and an input for accepting commands from the user.

The client preferably executes software supporting standard web browsing functionality. In one embodiment, the client executes the WIDOWS CE operating system. Programs executing on the operating system include a hypertext markup language (HTML) rendering engine, a JAVA virtual machine for executing JAVA programs, and other controls supporting web browsing functionality. A shell program also preferably executes on the operating system and generates a user interface on the display. The shell program controls access to sets of application program interfaces (APTs) for providing functionality at the client. For example, the APIs include functions allowing a program to change the channel, access an electronic program guide held by the client, instantiate user interface (UI) elements, and access an electronic walled held by the client.

The cable modem is preferably coupled to a coaxial cable and supports bi-directional broadband communications using the Internet protocol (IP). The coaxial cable is typically aggregated with other cables into a fiber-optic cable. The fiber-optic cable, in turn, is coupled to a cable modem termination server (CMTS) at a headend. The CMTS contains hardware for terminating the IP data channel, including IP switches, routers, and high-availability servers.

The CMTS allows the client to access a private network containing a walled garden proxy server (WGPS) via the hypertext transport protocol (HTTP). The WGPS controls access to a walled garden of network-based services. The services available in the walled garden may include, for example, access to electronic content, access to electronic commerce services, and any other functionality that can be provided electronically via a network. These services are provided by one or more walled garden servers coupled to a walled garden network. The walled garden servers may include servers directly coupled to the walled garden network, servers having direct connections to remote application databases, servers coupled to the walled garden network via a virtual private network, and servers having only a frontend on the walled garden network. Each site on a walled garden server is identified by a plot number.

A site held on a server within the walled garden may respond to a user by sending a message containing a JAVASCRIPT program to the client. The program can invoke one or more of the functions in the APIs. The WGPS traps messages from the site and determines the ACL for the site. The ACL is preferably a bit-map that specifies which STB API functions may be called by the site. The WGPS passes the ACL to the client as a header to the message from the site. In addition, the WGPS examines the header received from the site to protect against ACL masquerading or spoofing by the site.

The shell executing on the client extracts the ACL from the header when it receives the message. The shell uses the bit-map to determine which API functions can be invoked by the walled garden site. If the JAVASCRIPT program tries to invoke a function for which it lacks permission, the client halts execution of the program and sends a message back to the site indicating that the invocation failed because the site lacks permission. Otherwise, the client allows the JAVASCRIPT program invoke the function and returns the result to the site. Thus, the walled garden site can use the APIs to provide services to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a high-level view of a network architecture according to a preferred embodiment of the present invention;

FIG. 2 is a high-level block diagram of a client according to an embodiment of the present invention;

FIG. 3 is a block diagram illustrating the various levels of software and hardware executing on the client illustrated in FIG. 2;

FIG. 4 is a high-level logical block diagram illustrating the client, a private network, the Internet, and other related entities;

FIG. 5 is a high-level block diagram of a computer system for performing as one of the servers illustrated in FIG. 4, such as the walled garden proxy server (WGPS) and/or the gateway server (GS);

FIG. 6 is a flow diagram illustrating transactions among the client, WGPS, GS, and keymaster according to a preferred embodiment of the present invention;

FIG. 7 is a flow diagram illustrating transactions between the WGPS, GS, and keymaster that may occur independently of the transactions of FIG. 6;

FIG. 8 illustrates the fields in a ticket according to an embodiment of the present invention; and

FIG. 9 is a flow diagram illustrating transactions among a walled garden site, the WGPS, and the client according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram illustrating a high-level view of the network architecture 100 according to a preferred embodiment of the present invention. A television (TV) 110 is coupled via a data link 111 to a client 112, which is preferably a set top box (STB). The TV 110 can be any form of television, including a conventional analog TV or a high-definition (HD) digital TV. In addition, the TV 110 may be a monitor coupled to the client 112 directly. Alternatively, the client 112 may be coupled to a computer system instead of a TV 110. The data link 111 may be, for example, a serial link, a radio frequency (RF) link, a broadband link, a standard monitor cable, or an S-video link. The client 112 can also be integrated into the TV or computer system.

Typically, the client 112 is an STB and is purchased or leased by a person or household who also subscribes to the cable TV and data communication services. The person or persons who performs this task is often referred to as the "subscriber." Because multiple people may use a single client 112, the person using the client in this description is referred to as a "user." The STB 112 or other device that the user uses to access data communication services is generically referred to as a "client." The distinction between actions performed by the user and client are often blurred, especially when the client performs an action, such as fetching a web page, on behalf of a user. Accordingly, the terms "user" and "client" are often interchangeable in this description.

The client 112 preferably includes at least one tuner for tuning a TV signal and a cable modem for receiving and transmitting data. In addition, the client 112 is preferably coupled to a coaxial cable 114 carrying analog and/or digital TV signals and providing two-way data communication between the client 112 and the rest of the network using the Internet protocol (IP). In alternative embodiments, data communication between the client 112 and the rest of the network may be provided by other forms of communication technologies, including analog modem, digital subscriber line (DSL), and wireless technologies. These alternative technologies may or may not carry TV or other video signals with the data.

In the embodiment where the client 112 is coupled to a coaxial cable, the coaxial cable 114 is aggregated with other cables at a node 116, typically from geographically proximate locations, into a fiber-optic cable 118. The fiber-optic cable 118, in turn, is aggregated with other fiber-optic cables at a headend 120.

The headend 120 integrates signals from multiple sources into the fiber-optic cable 118. In one embodiment, the headend 120 receives analog 122A and digital 122B television signals via analog 124A and digital 124B satellite downlinks, respectively. In addition, the headend 120 includes a cable modem termination server (CMTS) 126 for terminating the IP data channel, including IP switches, routers, and high-availability servers.

The CMTS 126 is preferably coupled to a private network 128 maintained by an Internet service provider (ISP) or other organization. In a preferred embodiment of the present invention, the private network 128 includes the high-speed network architecture described in U.S. patent application Ser. No. 08/811,586, now U.S. Pat. No. 6,370,571, entitled SYSTEM AND METHOD FOR DELIVERING HIGH-PERFORMANCE ONLINE MULTIMEDIA SERVICES, filed on Mar. 5, 1997 by Milo S. Medin, which is hereby incorporated by reference herein. In general, (by the private network 128 provides network access to the users by managing a cable modem contained within the client 112. A widely accepted standard for cable modems is the Multimedia Cable Network System (MCNS) Data-Over-Cable Service Interface Specifications (DOCSIS). The private network 128 also provides connectivity to servers providing services to the clients, such as caching, account and billing management, electronic commerce, information databases, and any other functionality that can be achieved via a network. Typically, the resources on the private network 128 can be accessed by only subscribers of the ISP.

In the illustrated embodiment, the private network 128 is in communication with the Internet 130 via a network link 132. For security purposes, a preferred embodiment of the present invention restricts the ability of the client 112 to download software from the Internet 130. However, other embodiments may provide the client 112 with full access to the Internet 130 or restrict the client to only the resources available in the private network 128.

FIG. 2 is a high-level block diagram of a client 112 according to an embodiment of the present invention. Preferably, the client 112 is an STB and supports both broadcast services including video, audio, and data, and IP-based services including e-mail, web browsing, IP multicast, and streaming video and audio. In a preferred embodiment of the present invention, the client 112 is a GENERAL INSTRUMENTS DCT-5000, although any STB, computer system, or modem providing equivalent functionality can be substituted. The client 112 preferably includes components typically found in a computer system including a central processing unit (CPU) 210. The CPU 210 can be any type of general or specific purpose processor and processes instructions and data for providing the functionality described herein. The CPU 210 is coupled via a bus 212 to a random access memory (RAM) 214, a read only memory (ROM) 216, and non-volatile memory 218, such as flash memory. The RAM 214 is preferably synchronous dynamic RAM (SDRAM) and stores programs and data used by the CPU 210 as is well known in the art. Similarly, the ROM 216 and flash memory 218 store instructions and data used to maintain the system operation and configuration.

The bus 212 also couples the CPU 210 with a graphics and video subsystem 220 which generates text and video images on the TV 110. In addition to providing conventional TV images, the graphics and video subsystem 220 preferably generates a user interface (UI) by which the user can access the features and services provided by the client 112. The graphics and video subsystem 220 may also support advanced features such as 3-D graphics, video decoding, and video digitizing.

TV and cable modem tuners 222, 224 are also, preferably coupled to the bus 212. The TV tuner 222 is preferably a frequency-agile tuner dedicated to analog and digital broadcast services. The cable modem tuner 224 is preferably a frequency-agile tuner dedicated to cable modem services. Although not shown in FIG. 2, the client 112 may also include other tuners for handling an out-of-band data channel and a return signal path. The tuners 222, 224 receive the signal from the coaxial cable 114.

An infrared (IR) transceiver 226 is also preferably coupled to the bus 212. The transceiver 226 can communicate with a wireless remote control or keyboard, thereby allowing a user to access the features of the client 112 either directly or via on-screen menus. The client 112 also preferably includes a secure microprocessor 228 for supporting secure transactions as described below. The secure microprocessor 228 holds a unique identification value for the client 112 called the "Box ID," a private/public key pair, and other information that can be used to authorize and authenticate messages to and from the client 112. In alternative embodiments, the client 112 may also include an audio accelerator for performing audio processing, an input/output (I/O) controller for communicating with external devices such as storage devices and hard copy output devices, and/or a network adapter for communicating with a local-area network.

FIG. 3 is a block diagram illustrating the various levels of client software program modules and hardware executing on the client 112 illustrated in FIG. 2. At the lowest level is the hardware 310 for executing the software and performing the basic functions supported by the client 112. Device drivers 312 for the various hardware elements sit between the operating system (OS) 314 and the hardware 310. In one embodiment, the OS 314 is a version of the WINDOWS CE operating system from MICROSOFT CORPORATION of Redmond, Wash. However, other OS's may also be used. The OS 314 controls the operation of the client 112 and makes the features of the client available to other programs executing on the client 112. The OS 314 uses the device drivers 312 to communicate with the hardware 310. In addition, a TV application programming interface (API) 316 also sits between the OS 314 and the hardware 310. The OS 313 uses the TV API 316 to access dedicated TV functionality within the hardware 310.

A JAVA virtual machine (JVM) 318 and hypertext markup language (HTML) rendering engine 320 preferably execute on the OS 314. The JVM 318 functions as a virtual machine and provides an execution space for JAVA programs 322. The JAVA programs 322 may be stored locally on the client 112 or downloaded from the private network 128 or the Internet 130. In addition, the JAVA programs 322 may utilize JAVA classes dedicated to supporting the TV and media functions available on the client 112. Similarly, the HTML rendering engine 320 supports traditional web browsing functionality. A user can use the web browser controls 324 to navigate through hypertext documents as is well known in the art.

In a preferred embodiment of the present invention, a shell program 326 executes at the highest level. The shell program 326 may be implemented using, for example, native code, JAVA, JAVSCRIPT, ActiveX controls, HTML, and/or dynamic link libraries (DLLs). The shell program 326 is the controlling application and provides the user interface (UI) on the TV 110 and application support for channel navigation, an electronic program guide, storing user preferences, email, and walled garden 420 access.

Preferably, the shell program 326 contains a set of foundation layer APIs 328 that can be called by programs downloaded via the private network 128. In one embodiment, the functions in the APIs are accessed by JAVASCRIPT code downloaded to the client 112 via HTTP. All functions available through the APIs are subject to access control and a program making use of the APIs must be authorized to access the functions. If a program calls a function for which it is not authorized, the client 112 returns a FAIL_FUNCTION_NOT_AUTHORIZED error status message to the program. This status message indicates to the program that the server that supplied the program is riot authorized to perform that function on the client 112.

Exemplary sets of APIs are described in the Appendix. As described therein, the APIs allow a program to change the television channel to which the client 112 is tuned, inquire about the details of a channel line-up, access an electronic program guide (EPG) stored by the client, instantiate UI elements on the television 110, retrieve information about viewer (i.e., user) accounts, access electronic wallet (E-wallet) functionality in the client to conduct electronic commerce transactions, set reminders for display on the television 110, and print pages on a printer (not shown) coupled to the client. Additional APIs may allow controlling scaling of the broadcast video picture on the television 110 and accessing settings stored by the client 112, including user preferences, bookmarks, parental controls, and diagnostics. Other APIs can easily be added to the shell 326 to provide functionality desired by the ISP, server, or users. Preferably, each function in the APIs is named, numbered, or otherwise uniquely identified. Likewise, groups of functions, related or otherwise, may also be named, numbered, or otherwise identified.

FIG. 4 is a high-level logical block diagram illustrating the client 112, the private network 128, the Internet 130, and other related entities. As shown in FIG. 4, the CMTS 126 is preferably coupled to a proxy server 410. The proxy server 410 provides caching of web pages and other data for the clients served by the CMTS 126. The proxy server 410 is connected to a network backbone 412. A walled garden proxy server (WGPS) 414, gateway server (GS) 416, and WWW Internet proxy server 418 (Internet server) are also coupled to the network backbone 412.

Preferably, the client 112 communicates with the servers on the network 412 using standard communications protocols including the IP, hypertext transport protocol (HTTP), and secure sockets layer (SSL). Communications between the client 112 and the various servers often takes the form of hypertext markup language (HTML) documents, extensible markup language (XML) documents, JAVASCRIPT programs, and data provided through forms. Servers and data on the network 412 are preferably identified with uniform resource locators (URLs).

Each user of the client 112 preferably has a unique identification. A user can log into the client 112 by inputting the user's identity and a personal identification number (PIN) or other form of password. This user information is preferably stored in a local database held in, for example, the non-volatile memory 218 or a storage device. The database has a record for each user of the client 112 and associates the record with the user's login information. The client 112 can provide the user's login information to other servers in the network 128 when necessary to authenticate the user. For security, the user records stored in the client 112 are opaque and cannot be viewed without the login information of the particular user. When a user logs into the client 112, the login preferably remains valid until the user explicitly logs out or the client 112 is turned off. If no user has logged into the client 112, one embodiment of the present invention uses a default user profile. The rights and privileges of the default user profile can be set by the ISP.

The WGPS 414 is the entry point for the walled garden 420. Although FIG. 4 illustrates only a single walled garden 420, an embodiment of the present invention can have multiple walled gardens controlled by a single WGPS or by multiple WGPS'. Each walled garden may be controlled by a different multiple systems operator (MSO) (e.g., a different cable television company).

The illustrated walled garden 420 includes one or more servers which, in turn, hold one or more sites for providing network-based services to the users. The services may include, for example, access to electronic content such as channel guides, magazines, newspapers, stock prices, music, or video, access to electronic commerce services such as stock trading and buying and selling goods, access to a time-based or metered service, and any other functionality that can be provided electronically via a network. Preferably, the services are implemented using a combination of JAVA, XML, HTML, and/or JAVASCRIPT. The servers may be maintained by the MSO, ISP, or by other organizations who have formed business relationships with the party managing the walled garden 420. In one embodiment, the services in the walled garden 420 are arranged into sets of tiers. Preferably, the user can subscribe to one or more of the services in the walled garden 420 either individually or as part of a tier.

The WGPS 414 has an associated database 415 for holding permissions available to the user and the walled garden sites. To access the walled garden 420, the client must present a "ticket" to the WGPS 414 specifying the walled garden 420 and services to which the user has access. Alternatively, the ticket may specify only those services which the user does not have access. The database 415 identifies "poisoned" tickets, i.e., those tickets that are no longer accepted and holds keys for decrypting encrypted tickets. The database also holds information identifying the MSO or MSOs who's customers have access to the walled garden 420 in order to ensure that the ticket is affiliated with the particular walled garden. The WGPS 414 uses the ticket and the information in the database 415 to authenticate the user and authorize the user to access the services in the walled garden 420.

The database 415 also identifies the rights of walled garden sites to access the APIs in the clients 112. Preferably, the database 415 stores a Walled Garden Permissions Table that specifies the API access rights of each server or site in the walled garden. In one embodiment of the present invention, the permissions table is as follows:

                 Walled Garden Permissions Table
        URL Prefix    User Agent      WG ACL        Affiliation
        http:// . . . DCT-5000        010111        0110
        http:// . . . DCT-5000        010101        0100
        http:// . . . DCT-5000        011101        0001
        . . .         . . .           . . .         . . .
        http:// . . . DCT-5000        110101        1000

• Inventors
  Brown, Ralph W.; Keller, Robert; Medin, Milo S.; Temkin, David;
• Assignee
  At Home Corporation (San Mateo, CA)
• Published
  May-4-2004
• Current US Classes:
  709/225
  709/229
  713/201
  719/328
  725/110
  725/118
  725/2
• Application #
  427778
• International Classes
  G06F 015/16; G06F 015/173; H04N 007/173
• Field of Search
  709/229 709/238 709/217 709/225 709/245 713/200 713/201 713/202 725/114 725/118 725/120 725/37 725/2 725/110 707/4 380/33 719/328
• Examiner
  Wiley; David
• Agent
  Fenwick & West LLP
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