US20160006714A1

US20160006714A1 - Protected media pipeline

Info

Publication number: US20160006714A1
Application number: US14/852,520
Authority: US
Inventors: Alexandre Grigorovitch; Chadd Knowlton; Kirt Debique; James Alkove; Geoffrey T. Dunbar; Sumedh N. Barde
Original assignee: Microsoft Technology Licensing LLC
Current assignee: Microsoft Technology Licensing LLC
Priority date: 2005-04-22
Filing date: 2015-09-12
Publication date: 2016-01-07
Also published as: US20060248594A1; US9363481B2

Abstract

A system for processing a media content comprising an application space, a media control mechanism operating in the application space, the media control mechanism controlling the operation of the system, a user interface adapted to provide input to the media control mechanism, a protected space distinct from the application space, and a protected media pipeline operating in the protected space, the protected media pipeline coupled to the media control mechanism, the protected media pipeline adapted to access the media content, process the media content, and output the media content.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation of and claims benefit from U.S. patent application Ser. No. 11/116,689 that was filed on Apr. 27, 2005, and that is a Non-Provisional of U.S. Provisional Patent Application No. 60/673,979 that was filed on Apr. 22, 2005, each of which is incorporated herein by reference in its entirety.

DESCRIPTION OF THE DRAWINGS

The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein:

FIG. 1 is a block diagram showing an example of a typical prior art media player or application designed to operate on an exemplary personal computer.

FIG. 2 is a block diagram showing an example of a trusted media system comprising an application space and a distinct protected space.

FIG. 3 is a block diagram showing exemplary components comprising an end-to-end system for protecting media content and other data from initial input to final output of a computing environment.

FIG. 4 is a block diagram showing exemplary components comprising a protected media pipeline operating in a protected space as part of a trusted media system.

FIG. 5 is a block diagram showing an alternate example of a protected media pipeline having a proxied media source as part of a trusted media system.

FIG. 6 is a block diagram showing an example of a further alternative example of a trusted media system.

FIG. 7 is a block diagram showing a plurality of protected media pipelines.

FIG. 8 is a block diagram showing an exemplary computing environment in which the software applications, systems and methods described in this application may be implemented.

FIG. 9 is a block diagram showing a conventional media application processing media content operating in a conventional computing environment with an indication of an attack against the system.

FIG. 10 is a block diagram showing a trusted application processing media content and utilizing a protected environment or protected space that tends to be resistant to attack.

FIG. 11 is a block diagram showing exemplary components of a trusted application that may be included in the protected environment.

FIG. 12 is a block diagram showing a system for downloading digital media content from a service provider that utilizes an exemplary trusted application utilizing a protected environment.

FIG. 13 is a block diagram showing exemplary attack vectors that may be exploited by a user or mechanism attempting to access media content or other data typically present in a computing environment in an unauthorized manner.

FIG. 14 is a flow diagram showing the process for creating and maintaining a protected environment that tends to limit unauthorized access to media content and other data.

FIG. 15 is a block diagram showing exemplary kernel components and other components utilized in creating an exemplary secure computing environment.

FIG. 16 and FIG. 17 are flow diagrams showing an exemplary process for loading kernel components to create an exemplary secure computing environment.

FIG. 18 is a block diagram showing a secure computing environment loading an application into an exemplary protected environment to form a trusted application that may be resistant to attack.

FIG. 19 is a flow diagram showing an exemplary process for creating a protected environment and loading an application into the protected environment.

FIG. 20 is a block diagram showing an exemplary trusted application utilizing an exemplary protected environment periodically checking the security state of the secure computing environment.

FIG. 21 is a flow diagram showing an exemplary process for periodically checking the security state of the secure computing environment.

FIG. 22 is a block diagram showing an exemplary computing environment including a representation of a protected environment, a trusted media system, and other related elements.

Like reference numerals are used to designate like elements in the accompanying drawings.

DETAILED DESCRIPTION

The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present examples may be constructed or utilized. The description sets forth the functions of the examples and the sequence of steps for constructing and operating the examples. However, the same or equivalent functions and sequences may be accomplished by different examples.
Although the present examples are described and illustrated herein as being implemented in a computer system, the system described is provided as an example and not a limitation. As those skilled in the art will appreciate, the present examples are suitable for application in a variety of different types of electronic systems.

Introduction

Digital media content is widely used in the form of CDs, DVDs and downloadable files. Various devices are able to process this media content including personal computers running various media player applications and the like, CD and DVD players, MP3 players and other general-purpose and/or dedicated electronic devices designed to process digital media content.
Because media content often comes in the form of a for-sale consumer products and the like, producers and providers may be anxious to protect their media content from unauthorized access, duplication, use, etc. Therefore, media content is often encrypted and/or otherwise secured. Some form of encryption key and/or other access mechanism may be provided for use with the media so that it can be accessed when and how appropriate. This key or mechanism may be used by a media application or the like to gain access to the protected media for processing, playing, rendering, etc.
Once the key or other mechanism has been used to decrypt or otherwise access media content within a system the media content may be vulnerable in its unprotected form. It may be possible to attack the system and/or media application so as to gain access to the unprotected media content. This may lead to the unauthorized access, use, duplication, distribution, etc. of the media content.
To avoid unauthorized access, a system that rightfully accesses the media content should be capable of protecting the media content. This protection should extend from the time the key or the like is obtained, used to access the media content, throughout any processing performed on the content, until the content is appropriately rendered in its authorized form. For example, a particular meeting may be recorded and encrypted using an access key with the intent of making the recording available to authorized personnel. Later, the recording is made available to an authorized individual via a media application on a PC. The media application uses the key to decrypt and access the media content, process it and play it for the listener. But if the media application itself has been compromised, or the application and/or content is attacked, the unencrypted media may no longer be protected.
One approach may be to construct a system for accessing, processing and rendering the media content within a protected environment that is designed to prevent unauthorized access to the media content. The example provided here describes a process and system for protecting media content from unauthorized access. Protection may be afforded by a protected media pipeline, among other mechanisms, which processes some, or all, of a media within a protected environment or protected space. A protected media pipeline may be composed of several elements.
A media source that may be part of the protected media pipeline accesses the media content, passes it through a set of transform functions or processes (decoders, effects, etc.) and then to a media sink which renders the processed media to a media output(s) (video rendering process, audio rendering process, etc). As an example, rendering may be as simple as sending audio signals to a set of headphones or it may be sending protected content in a secure manner to yet another process, system or mechanism external to the protected media pipeline.
A protected media pipeline may be constructed as a set or chain of media processing mechanisms operating in a secure or protected environment. In a PC, a protected media pipeline can be thought of as a software process that operates in a secure environment which protects the media content from unauthorized access while the content is being accessed, played and/or otherwise processed by the media system. When media content is being processed by an electronic device, a protected media pipeline can be thought of as a set of media processing mechanisms operating within a secure environment such that the media being processed is resistant to unauthorized access. The mechanism for providing this resistance may be purely physical in nature, such as a sealed case or lack of access points to the media content.
There may be two major aspects to constructing a trusted media system with a protected media pipeline. First, a trusted media system may be designed and constructed in such a way that it acknowledges and adheres to any access rules of the media content by ensuring that no actions are taken with the content above and beyond those allowed. Various mechanisms known to those skilled in this technology area may be used to address this first point. These mechanisms may include using encryption/decryption, key exchanges, passwords, licenses, interaction with a digital rights management system, and the like. Further, this may be as simple as storing the media content on/in a device such that it is resistant to physical, electronic or other methods of accessing and using the media content, except as intended.
Second, the trusted media system may be designed and constructed such that the media content being processed is secure from malicious attacks and/or unauthorized access and use. Processing the media content via a protected media pipeline operating in a protected environment or protected space addresses this second point. So in short, a protected media pipeline operating in a protected space refers to a media processing environment that resists unauthorized access to the media content being processed.
FIG. 1 is a block diagram showing an example of a typical prior art media player or application 100 designed to operate on an exemplary personal computer (FIG. 8, 800). Equivalently, media players may operate on other devices with similar processing capabilities such as consumer electronic devices and the like. Other media applications may include, but are not limited to, media processors, media manipulators, media analyzers, or media formatters. A media application may be a software application program that provides a way of playing media such as audio and video by a digital processor such as a CPU (FIG. 8, 807) or the like. A media application may include a user interface or graphic 101 that may indicate the media being played and provides various user controls. Controls may be accessed through activation with a computer pointing device such as a mouse or by conventional buttons or the like. Such a media application may be thought of as a software application program operating in an application space 102 that is provided by the PC's computing environment (FIG. 8, 801) or operating system.
Another example of a media player may be a hardware device comprising a memory capable of storing media content and various button, switches, displays and controls and the like to allow a user to control the device, select the media to be played, control volume, download media content, etc.
The media player 100 may be comprised of mechanisms 104, 106 and 108. These mechanisms may operate in the application space 102. For a software media player, an application space 102 may be a space created in system memory (FIG. 8, 809) on a PC (FIG. 8, 800) where various software components or processes can be loaded and executed. For a hardware media player an application space 102 may be a printed circuit board and an electronic module containing the electronic elements that perform the processing and functions of the media player 100. The media player application 100 may include other spaces and mechanisms which may provide additional capabilities or features that may or may not be directly related to the processing of media. For example, a second media player playing a music selection may operate in a media application at the same time as a media player playing a newscast.
The application space 102 may include a user interface process 104 coupled to a media control process 106 which in turn is coupled to a media processing process 108. Typically these processes enable the media application 100 to couple to a source of media content 110, process the media content 110 and render it via media output 130. The media content 110 may or may not be encrypted or otherwise protected as part of an overall security and access control scheme.
For example, when activated the media application 100 may access audio content 112 and video content 114 typically available on a DVD ROM, an on-line source, or the like. The media content 110 may be played via media processing 108 which renders the content as audio output 132 and/or video output 134. Audio and video may typically be rendered on the speakers and/or display of a PC (FIG. 8, 800). This system is only one example of common media applications and environments that enable audio and video and the like to be processed, played and/or provided to other processes or systems. Another example of a media application would be a consumer electronic device such as an electronic juke box or the like. Yet another example would be a dedicated electronic device, with or without software and/or firmware.
Application space 102 may contain various processes and, in this example, includes the user interface process 104, the media control process 106, the media processing process 108, or their equivalents, used to coordinate and control the overall operation of the media application 100 and its processes. Typically, to prepare the media content 110, the user interface process 104 may provide an interface 101 for interaction between the user and the application. The media control process 106 or its equivalents may provide the overall management and control of the internal operations of the media application 100. The media processing process 108 may perform the processing of the media content 110 making it possible to render the media content via the media output 130, or perform whatever other media processing it may have been designed to perform.
The processes described above may not be secure against unauthorized access to the media content 110. Processing the media content 110 via such a system may expose it to unauthorized access. Such an unprotected application may enable users and/or attackers, with varying degrees of effort, to access and make use of the media content 110 in an unauthorized manner. For example, unauthorized access may enable the unauthorized sharing, copying, modifying, and/or distributing of media content 110.

Exemplary Trusted Media System

FIG. 2 is a block diagram showing an example of a trusted media system 200 comprising an application space 202 and a distinct protected space 230. In this exemplary embodiment of a media player the system comprises a protected media pipeline 232 operating within a protected space 230 in addition to user interface 204 and media control 206 mechanisms operating in the application space 202.
The protected space 230 typically provides a protected environment for media content 110 processing, the protected space 230 resisting unauthorized access to the media content 110 during processing. Media content 110 is typically protected by various built-in security schemes to deliver it un-tampered—with to a user, such as encryption and the like. However, once the media content 110 is decrypted or the like for processing, additional mechanisms to protect it from unauthorized access are required. A protected media pipeline 232 operating in a protected space 230.
Application space 202 may be contain various mechanisms including, but not limited to, a user interface mechanism 204 and a media control mechanism 206, or their equivalents, which are coupled to the protected media pipeline 232 operating within the protected space 230. Typically the user interface process 204 may provide an interface 201 or set of controls for interaction between the user and the system. The media control process 206 may provide the overall management and control of the internal operations of the trusted media system 200. The protected media pipeline 232 operating in the protected space 230 may perform the processing of the media content 110 and render the content via the media output 130, or perform whatever other media processing the media system 200 is designed to perform.
One or more protected spaces 230 may be provided as an extension of a computing environment (FIG. 8, 801) and typically possess a heightened level of security and access control. A protected space 230 may also include mechanisms to ensure that any mechanism operating inside it, such as a protected media pipeline 232, along with any media content being processed within the protected space 230, are used and accessed appropriately. In some embodiments the access and use privileges may be indicated by a media content license and/or a digital rights management system. Alternatively, mechanisms such as password protection, encryption and the like may provide access control.
FIG. 3 is a block diagram showing exemplary components comprising an end-to-end system for protecting media content 110 and other data from initial input 302 to final output 308 of a computing environment 800. Such a system tends to protect media 110 or other data from the point of entry into a computing environment 800 to its final output 130 in addition to providing protection during processing within a protected media pipeline 232 and/or other processing components. Such end-to-end protection may be provided via three major components-protected input 302, a protected space 230 for processing and protected output 308.
Protected input 302 may be implement in hardware and/or software and may limit unauthorized access to media content 110 and/or other data as it is initially received onto the system 800 from some source such as a storage device, network connection, physical memory device and the like. The protected input 302 may be coupled to a protected media pipeline 232 via a secure connection 304. The secure connection 304 allows transfer of the media content 110 between the protected input 302 and the protected media pipeline 232 and/or other processing components and may be implemented using mechanisms such that it is tamper resistant.
Protected output 306 may be implemented in hardware and/or software and may limit unauthorized access to media content 110 as it is transferred from a protected media pipeline 232 or other processing to the output of the computing environment 800 which may be speakers, video displays, storage media, network connections and the like. The protected output 308 may be coupled to a protected media pipeline 232 via a secure connection 306. The secure connection 306 allows transfer of the media content 110, which may be in a processed form, between the protected media pipeline 232 and the protected output 308 and may be implemented using mechanisms such that it is tamper resistant.
Tamper resistance as used here includes limiting unauthorized access, resisting attack and otherwise protecting media content and/or other data from being compromised.
A protected space may also be referred to as a protected environment. Protected spaces or environments and their creation and maintenance are described beginning with the description of FIG. 9 below.

Protected Media Pipeline

FIG. 4 is a block diagram showing exemplary components comprising a protected media pipeline 232 operating in a protected space 230 as part of a trusted media system 200. The components 400, 421, 422, 425, and 480 form a protected media pipeline 232 operating in a protected space 230. Of these components, the transforms mechanisms 420 process the media content to prepare it for output. The protected space 230 may also contain other protected elements 410 of the trusted media system 200.
The protected media pipeline 232 typically performs the function of accessing and processing protected media content 110 and producing a protected output in the format determined by the trusted media system 200. Unprotected media content may also be processed in a protected media pipeline 232. Further, unprotected media pipelines may be constructed and operate in the application space 202 or other spaces. However, an unprotected media pipeline operating in the application space 202 would not benefit from a protected environment 230 which limits unauthorized access to the media content. For processing some types of media content, such as unprotected or unencrypted media content, an unprotected pipeline may be acceptable. In some embodiments there may be a plurality of media content having different security levels (some protected and some unprotected), processed through one or more pipelines each adapted to provide the desired level of protection.
In the protected media pipeline 232 a media source 400 may be coupled to a series of transform functions or mechanisms 420. A first transform function F(a)1 421 may be coupled to a second transform function F(b)2 422 which in turn may be coupled to any number of additional transform functions represented by F(z)n 425. The output of the set of transform functions 420 may be coupled to a media sink 480. There are typically one or more transform functions in a protected media pipeline 232, the specific function of each transform depending on the media content 110 and the processing that the trusted media system 200 is designed to perform.
The example shown illustrates transform mechanisms that may be connected in series forming a transform chain. In alternative embodiments of a protected media pipeline 232, two or more of the transform mechanisms may be coupled in parallel and/or two or more media pipelines may be coupled at some point in each pipeline's transform chain forming a single pipeline from that point forward. Further, each transform may have a single input or a plurality of inputs and they may have a single output or a plurality of outputs.
The media source 400 may access media content 110 via hardware and/or appropriate driver software or the like. For example, using a PC for processing music stored on a CD, the media source 400 couples to CD ROM driver software which controls the CD ROM drive hardware (FIG. 8, 804) to read audio data from a CD ROM disk (FIG. 8, 806). The media source 400 is a mechanism used in the construction of a media pipeline to access and receive the media content 110 and make it available to the remaining mechanisms of the media pipeline. Alternatively, a media source 400 may couple with a semiconductor memory in a consumer electronic device to access music stored on the device. Equivalent media sources may provide access to one or more types of media content, including video, digital recordings, and the like.
The media transforms 420, represented by F(a)1, F(b)2 and F(z)n, (421, 422 and 425 respectively) perform specific operations on the media content provided by the media source 400 and may each perform different operations. There are typically at least one media transform in a media pipeline. The media transforms 421, 422 and 425 prepare and/or process the media content 110 for rendering via the media output 130 and/or for further processing. The specific transformations performed may include operations such as encryption and/or decryption of media content, image enhancement of video content, silence detection in audio content, decompression, compression, volume normalization, and the like. Transforms may process media content 110 automatically or be controlled by a user via virtual or physical handles provided through a user interface 204. The specific transforms provided in a pipeline depend on the media content 110 to be processed and the function the trusted media system 200 has constructed the pipeline to perform. In a simple media system or application the processing may be as minimal as decoding an audio media and controlling the volume of the media accessed from a semiconductor memory and played on a headset. In a more complex media system or application a wide variety of processing and media manipulation are possible.
In a trusted media system 200 designed to process encrypted media content one of the transform mechanisms, typically the first transform F(a)1 421, may be a codec which decodes the media content such that it may be further processed. In alternative examples, decryption and/or decompression operations may be performed by distinct mechanisms and one or both operations may be eliminated depending on the format of media content being processed.
When operating on a PC, the media sink 480 may couple the processed or transformed media content 110 to the media output 130 via the media I/O hardware (FIG. 8, 812) controlled by appropriate driver programs. For example, in the case of audio data, the media sink 480 may couple to an available sound driver program which couples audio data that has been transformed to audio output hardware such as an amplifier and/or speakers (FIG. 2, 132). When operating on a consumer electronic device, the media sink 480 may be coupled, for example, to an audio amplifier which in turn couples to speakers or a headset through a connector on the device's case.
By constructing a pipeline that performs the sourcing, transform and sinking functions within a protected space 230, unauthorized access to the media content 110 may be restricted in a manner that conforms to the wishes of the media content provider/owner. Thus, this approach tends to provide a secure processing environment such that a media content provider may trust that their media content 110 will not be compromised while being processed.
The output of the protected media pipeline 232 may be coupled to the input of a media output 130. Alternatively the output of a protected media pipeline 232 may couple to the input of another protected media pipeline or some other process. This coupling may be implemented such that it is tamper resistant and restricts unauthorized access to any data or media content flowing from one pipeline to another or to some other process. The remainder of the elements illustrated in FIG. 4 operate as previously described for FIG. 2.
FIG. 5 is a block diagram showing an alternate example of a protected media pipeline 552 having a proxied media source 510 as part of a trusted media system 500. The proxied media source 510 includes a media source portion 518 and a stub portion 520 that may operate in an unprotected application space 502, and a proxy portion 540 that may operate in a protected space 550. The proxied media source 510 may allow media content 110 to be transferred from the application space 502 via the media source 518 and the stub 520 to the protected space 550 via the proxy 540 by using remote procedure calls or the like.
When used in a PC environment (FIG. 8, 800), the proxied media source 510 architecture described here may simplify the creation of the media source modules by third-party software makers or content providers. Such a simplification may be provided by splitting the proxied media source 510 such that media application writers may only need to implement the media source portion 518. The stub portion 520 and proxy portion 540 may be provided as an element of the protected environment 550.
Further, the use of a proxied media source 510 may support mixing protected and unprotected media content 110 by allowing protected media content to be directed from a media source 518 to a first stub operating as part of a protected media pipeline while the unprotected media content may be directed from the media source 518 to processing modules operating within the unprotected application space 502 or other unprotected space via a second stub portion also operating within the unprotected application space 502 or some other unprotected space.
Similar to the proxied media source 510, the media sink 480 may also be proxied and split into stub and proxy portions. The stub portion may operate in the protected space 650 and may encrypt data prior to forwarding it to the proxy portion operating in an application space 202 or some other space. The remainder of the elements in FIG. 5 operate as previously described for FIG. 4.
FIG. 6 is a block diagram showing an example of a further alternative example of a trusted media system 600. In this embodiment the trusted media system 600 includes a protected media source 610 constructed to include a media source portion 618 and a stub portion 620 which operate in a protected media space 609, and a proxy portion 640 which operates in a protected space 650. The two protected regions 609 and 650 are coupled by the protected media source 610 with data being passed from the media source portion 618 via the stub portion 620 operating in the protected media space 609 to the proxy portion 640 operating in the protected space 650. The protected media source 610 may allow media content 110 to be transferred from the protected media space 609 to the protected pipeline space 650 using remote procedure calls or the like. The protected media source 610 architecture described here may simplify the creation of the media source by third-parties or content providers and result in more stable and secure protected media applications 600. The remaining elements of FIG. 6 operate as previously described for FIG. 4 and FIG. 5.
FIG. 7 is a block diagram showing a plurality of protected media pipelines 751-759. The protected media pipelines 751, 752, 759 operate in a protected space 700. Alternatively each protected media pipeline may operate in its own protected space or various numbers of pipelines may be grouped into one or more protected spaces in any combination. A trusted media system may provide several such protected media pipelines.
An example of such a system may be a trusted media system playing a DVD with its audio content in Dolby digital 5.1 format. In this example there may be six different audio pipelines, one for each of the audio channels, in addition to a video pipeline for the video portion of the DVD. All of the protected media pipelines may operate in the same protected space as shown or, alternatively, the protected media pipelines may be grouped in groups of one or more with each group operating in its own distinct protected space.
In alternative embodiments of a protected media pipeline 232, two or more of the sources, transform mechanisms and/or sinks may be coupled in parallel and/or two or more media pipelines may be coupled at some point in each pipeline forming a single pipeline from that point forward. Alternatively a single pipeline may split into two pipelines. Further, sources, transforms and/or sinks may have a single input or a plurality of inputs and/or they may have a single output or a plurality of outputs. The remaining elements of FIG. 7 operate as previously described for FIG. 4.
FIG. 8 is a block diagram showing an exemplary computing environment 800 in which the software applications, systems and methods described in this application may be implemented. Exemplary personal computer 800 is only one example of a computing system or device that may process media content (FIG. 4, 110) and is not intended to limit the examples described in this application to this particular computing environment or device type.
The computing environment can be implemented with numerous other general purpose or special purpose computing system configurations. Examples of well known computing systems may include, but are not limited to, personal computers 800, hand-held or laptop devices, microprocessor-based systems, multiprocessor systems, set top boxes, programmable consumer electronics, gaming consoles, consumer electronic devices, cellular telephones, PDAs, and the like.
The PC 800 includes a general-purpose computing system in the form of a computing device 801. The components of computing device 801 may include one or more processors (including CPUs, GPUs, microprocessors and the like) 807, a system memory 809, and a system bus 808 that couples the various system components. Processor 807 processes various computer executable instructions to control the operation of computing device 801 and to communicate with other electronic and computing devices (not shown) via various communications connections such as a network connection 814 an the like. The system bus 808 represents any number of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures.
The system memory 809 includes computer readable media in the form of volatile memory, such as random access memory (RAM), and/or non-volatile memory, such as read only memory (ROM). A basic input/output system (BIOS) may be stored in ROM. RAM typically contains data and/or program modules that are immediately accessible to and/or presently operated on by one or more of the processors 807. A trusted media system 200 may be contained in system memory 809.
Mass storage devices 804 and 810 may be coupled to the computing device 801 or incorporated into the computing device by coupling to the system bus. Such mass storage devices 804 and 810 may include a magnetic disk drive which reads from and/or writes to a removable, non volatile magnetic disk (e.g., a “floppy disk”) 805, or an optical disk drive that reads from and/or writes to a removable, non-volatile optical disk such as a CD ROM, DVD ROM or the like 806. Computer readable media 805 and 806 typically embody computer readable instructions, data structures, program modules and the like supplied on floppy disks, CDs, DVDs, portable memory sticks and the like.
Any number of program modules may be stored on the hard disk 810, other mass storage devices 804, and system memory 809 (limited by available space), including by way of example, an operating system(s), one or more application programs, other program modules, and program data. Each of such operating system, application program, other program modules and program data (or some combination thereof) may include an embodiment of the systems and methods described herein. For example, a trusted media system 200 may be stored on mass storage devices 804 and 810 and/or in system memory 809.
A display device 134 may be coupled to the system bus 808 via an interface, such as a video adapter 811. A user can interface with computing device 800 via any number of different input devices 803 such as a keyboard, pointing device, joystick, game pad, serial port, and/or the like. These and other input devices may be coupled to the processors 807 via input/output interfaces 812 that may be coupled to the system bus 808, and may be coupled by other interface and bus structures, such as a parallel port, game port, and/or a universal serial bus (USB).
Computing device 800 may operate in a networked environment using communications connections to one or more remote computers and/or devices through one or more local area networks (LANs), wide area networks (WANs), the Internet, optical links and/or the like. The computing device 800 may be coupled to one or more networks via network adapter 813 or alternatively by a modem, DSL, ISDN interface and/or the like.
Communications connection 814 is an example of communications media. Communications media typically embody computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communications media include wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency, infrared, and other wireless media.
Those skilled in the art will realize that storage devices utilized to store computer-readable program instructions can be distributed across a network. For example a remote computer or device may store an example of the system described as software. A local or terminal computer or device may access the remote computer or device and download a part or all of the software to run the program. Alternatively the local computer may download pieces of the software as needed, or distributively process the software by executing some of the software instructions at the local terminal and some at remote computers or devices.
Those skilled in the art will also realize that by utilizing conventional techniques known to those skilled in the art that all, or a portion, of the software instructions may be carried out by a dedicated electronic circuit such as a digital signal processor (“DSP”), programmable logic array (“PLA”), or the like. The term electronic apparatus as used herein includes computing devices, consumer electronic devices including any software and/or firmware and the like, and electronic devices or circuits containing no software and/or firmware and the like.
The term computer readable medium may include system memory, hard disks, mass storage devices and their associated media, communications media, and the like.

Protected Environment

FIG. 9 is a block diagram showing a conventional media application 100 processing media content 110 operating in a conventional computing environment 900 with an indication of an attack 907 against the system 901. A conventional computing environment 900 may be provided by a personal computer (“PC”) or consumer electronics (“CE”) device 901 that may include operating system (“OS”) 902. Typical operating systems often partition their operation into a user mode 903, and a kernel mode 904. User mode 903 and kernel mode 904 may be used by one or more application programs 100. An application program 100 may be used to process media content 110 that may be transferred to the device 901 via some mechanism, such as a CD ROM drive, Internet connection or the like. An example of content 110 would be media files that may be used to reproduce audio and video information.
The computing environment 900 may typically include an operating system (“OS”) 902 that facilitates operation of the application 100, in conjunction with the one or more central processing units (“CPU”). Many operating systems 902 may allow multiple users to have access to the operation of the CPU. Multiple users may have ranges of access privileges typically ranging from those of a typical user to those of an administrator. Administrators typically have a range of access privileges to applications 100 running on the system, the user mode 903 and the kernel 904. Such a computing environment 900 may be susceptible to various types of attacks 907. Attacks may include not only outsiders seeking to gain access to the device 901 and the content 110 on it, but also attackers having administrative rights to the device 901 or other types of users having whatever access rights granted them.
FIG. 10 is a block diagram showing a trusted application 200 processing media content 110 and utilizing a protected environment or protected space 230 that tends to be resistant to attack 1005. The term “trusted application”, as used here, may be defined as an application that utilizes processes operating in a protected environment such that they tend to be resistant to attack 1005 and limit unauthorized access to any media content 110 or other data being processed. Thus, components or elements of an application operating in a protected environment are typically considered “trusted” as they tend to limit unauthorized access and tend to be resistant to attack. Such an application 200 may be considered a trusted application itself or it may utilize another trusted application to protect a portion of its processes and/or data.
For example, a trusted media player 200 may be designed to play media content 110 that is typically licensed only for use such that the media content 110 cannot be accessed in an unauthorized manner. Such a trusted application 200 may not operate and/or process the media content 110 unless the computing environment 1000 can provide the required level of security, such as by providing a protected environment 230 resistant to attack 1005.
As used herein, the term “process” may be defined as an instance of a program (including executable code, machine instructions, variables, data, state information, etc.), residing and/or operating in a kernel space, user space and/or any other space of an operating system and/or computing environment.
A digital rights management system 1004 or the like may be utilized with the protected environment 230. The use of a digital rights management system 1004 is merely provided as an example and may not be utilized with a protected environment or a secure computing environment. Typically a digital rights management system utilizes tamper-resistant software (“TRS”) which tends to be expensive to produce and may negatively impact computing performance. Utilizing a trusted application 200 may minimize the amount of TRS functionality required to provide enhanced protection.
Various mechanisms known to those skilled in this technology area may be utilized in place of, in addition to, or in conjunction with a typical digital rights management system. These mechanisms may include, but are not limited to, encryption/decryption, key exchanges, passwords, licenses, and the like. Thus, digital right management as used herein may be a mechanism as simple as decrypting an encrypted media, utilizing a password to access data, or other tamper-resistant mechanisms. The mechanisms to perform these tasks may be very simple and entirely contained within the trusted application 200 or may be accessed via interfaces that communicate with complex systems otherwise distinct from the trusted application 200.
FIG. 11 is a block diagram showing exemplary components of a trusted application 200 that may be included in the protected environment 230. A trusted application 200 will typically utilize a protected environment 230 for at least a portion of its subcomponents 232, 400, 480. Other components 1101 of the trusted application may not utilize a protected environment. Components 232, 400 and 480 involved in the processing of media content or data that may call for an enhanced level of protection from attack or unauthorized access may operate within a protected environment 230. A protected environment 230 may be utilized by a single trusted application 200 or, possibly, by a plurality of trusted applications. Alternatively, a trusted application 200 may utilize a plurality of protected environments. A trusted application 200 may also couple to and/or utilize a digital rights management system 1004.
In the example shown, source 400 and sink 480 are shown as part of a media pipeline 232 operating in the protected environment 230. A protected environment 230 tends to ensure that, once protected and/or encrypted content 1109 has been received and decrypted, the trusted application 200 and its components prevent unauthorized access to the content 1109.
Digital rights management 1004 may provide a further avenue of protection for the trusted application 200 and the content 1109 it processes. Through a system of licenses 1108, device certificates 1111, and other security mechanisms a content provider is typically able to have confidence that encrypted content 1109 has been delivered to the properly authorized device and that the content 1109 is used as intended.
FIG. 12 is a block diagram showing a system for downloading digital media content 1210 from a service provider 1207 to an exemplary trusted application 200 utilizing a protected environment 230. In the example shown the trusted application 200 is shown being employed in two places 1201, 1203. The trusted application 200 may be used in a CE device 1201 or a PC 1203. Digital media 1210 may be downloaded via a service provider 1207 and the Internet 1205 for use by the trusted application 200. Alternatively, digital media may be made available to the trusted application via other mechanisms such as a network, a CD or DVD disk, or other storage media. Further, the digital media 1210 may be provided in an encrypted form 1109 requiring a system of decryption keys, licenses, certificates and/or the like which may take the form of a digital rights management system 1004. The data or media content 1210 provided to the trusted application may or may not be protected, i.e., encrypted or the like.
In one example, a trusted application 200 may utilize a digital rights management (“DRM”) system 1004 or the like along with a protected environment 230. In this case, the trusted application 200 is typically designed to acknowledge, and adhere to, the content's usage policies by limiting usage of the content to that authorized by the content provider via the policies. Implementing this may involve executing code which typically interrogates content licenses and subsequently makes decisions about whether or not a requested action can be taken on a piece of content. This functionality may be provided, at least in part, by a digital rights management system 1004. An example of a Digital Rights Management system is provided in U.S. patent application Ser. No. 09/290,363, filed Apr. 12, 1999, U.S. patent application Ser. Nos. 10/185,527, 10/185,278, and 10/185,511, each of which filed on Jun. 28, 2002, and incorporated herein by reference in its entirety.
Building a trusted application 200 that may be utilized in the CE device 1201 or the PC 1203 may include making sure the trusted application 200 which decrypts and processes the content 1109 may be “secure” from malicious attacks. Thus, a protected environment 230 typically refers to an environment that may not be easy to attack.
As shown, the trusted applications 200 operate in a consumer electronics device 1201, which can be periodically synced to a PC 1203 that also provides a trusted application. The PC 1203 is in turn coupled 1204 to the internet 1205. The internet connection allows digital media 1210 to be provided by a service provider 1207. The service provider 1207 may transmit licenses and encrypted media 1206 over the internet 1205 to trusted application 200. Once encrypted media is delivered and decrypted it may be susceptible to various forms of attack.
A protected computing environment tends to provide an environment that limit hackers from gaining access to unauthorized content. A hacker may include hackers acting as a systems administrator. A systems administrator typically has full control of virtually all of the processes being executed on a computer, but this access may not be desirable. For example, if a system user has been granted a license to use a media file it should not be acceptable for a system administrator different from the user to be able to access the media file. A protected environment tends to contribute to the creation of a process in which code that decrypts and processes content can operate without giving hackers access to the decrypted content. A protected environment may also limit unauthorized access to users of privilege, such as administrators, and/or any other user, who may otherwise gain unauthorized access to protected content. Protection may include securing typical user mode (FIG. 9, 903) processes and kernel mode (FIG. 9, 904) processes and any data they may be processing.
Processes operating in the kernel may be susceptible to attack. For example, in the kernel of a typical operating system objects are created, including processes, which may allow unlimited access by an administrator. Thus, an administrator, typically with full access privileges, may access virtually all processes.
Protected content may include policy or similar information indicating the authorized use of the content. Such policy may be enforced via a DRM system or other mechanism. Typically, access to the protected content is granted through the DRM system or other security mechanism, which may enforce policy. However, a system administrator, with full access to the system, may alter the state of the DRM system or mechanism to disregard the content policy.
A protected environment tends to provide a protected space that restricts unauthorized access to media content being processed therein, even for high-privilege users such as an administrator. When a protected environment is used in conjunction with a system of digital rights management or the like, a trusted application may be created in which a content provider may feel that adequate security is provided to protect digital media from unauthorized access and may also protect the content's policy from be tampered with along with any other data, keys or protection mechanisms that may be associated with the media content.
Current operating system (“OS”) architectures typically present numerous possible attack vectors that could compromise a media application and any digital media content being processed. For purposes of this example, attacks that may occur in an OS are grouped into two types of attacks, which are kernel mode attacks and user mode attacks.
The first type of attack is the kernel mode attack. Kernel mode is typically considered to be the trusted base of the operating system. The core of the operating system, most system and peripheral drivers operate in kernel mode. Typically any piece of code running in the kernel is susceptible to intrusion by any other piece of code running in the kernel, which tends not to be the case for user mode. Also, code running in kernel mode typically has access to substantially all user mode processes. A CPU may also provide privilege levels for various code types. Kernel mode code is typically assigned the highest level of privilege by such a CPU, typically giving it full access to the system.
The second type of attack is the user mode attack. Code that runs in user mode may or may not be considered trusted code by the system depending on the level of privilege it has been assigned. This level of privilege may be determined by the user context or account in which it is operating. User mode code running in the context of an administrator account may have full access to the other code running on the system. In addition, code that runs in user mode may be partitioned to prevent one user from accessing another's processes.
These attacks may be further broken down into specific attack vectors. The protected environment is typically designed to protect against unauthorized access that may otherwise be obtained via one or more of these attack vectors. The protected environment may protect against attack vectors that may include: process creation, malicious user mode applications, loading malicious code into a process, malicious kernel code, invalid trust authorities, and external attack vectors.
Process creation is a possible attack vector. An operating system typically includes a “create process” mechanism that allows a parent process to create a child process being created. A malicious parent process may, by modifying the create process code or by altering the data it creates, make unauthorized modifications to the child process. This could result in compromising digital media that may be processed by a child process created by a malicious parent process.
Malicious user mode applications are a possible attack vector. An operating system typically includes administrator level privileges. Processes running with administrator privileges may have unlimited access to many operating system mechanisms and to nearly all processes running on the computer. Thus, in Windows for example, a malicious user mode application running with administrator privileges may gain access to many other processes running on the computer and may thus compromise digital media. Similarly, processes operating in the context of any user may be attacked by any malicious process operating in the same context.
Loading malicious code into a secure process is a possible attack vector. It may be possible to append or add malicious code to a process. Such a compromised process cannot be trusted and may obtain unauthorized access to any media content or other data being processed by the modified process.
Malicious kernel mode code is a possible attack vector. An operating system typically includes a “system level” of privilege. In Windows, for example, all code running in kernel mode is typically running as system and therefore may have maximum privileges. The usual result is that all drivers running in kernel mode have maximum opportunity to attack any user mode application, for example. Such an attack by malicious kernel mode code may compromise digital media.
Invalid trust authorities (TAs) are a possible attack vector. TAs may participate in the validation of media licenses and may subsequently “unlock” the content of a digital media. TAs may be specific to a media type or format and may be implemented by media providers or their partners. As such, TAs may be pluggable and/or may be provided as dynamic link libraries (“DLL”). A DLL or the like may be loaded by executable code, including malicious code. In order for a TA to ensure that the media is properly utilized it needs to be able to ensure that the process in which it is running is secure. Otherwise the digital media may be compromised.
External attacks are another possible attack vector. There are a set of attacks that don't require malicious code running in a system in order to attack it. For instance, attaching a debugger to a process or a kernel debugger to the machine, looking for sensitive data in a binary file on a disk, etc., are all possible mechanisms for finding and compromising digital media or the processes that can access digital media.
FIG. 13 is a block diagram showing exemplary attack vectors 1307-1310 that may be exploited by a user or mechanism attempting to access media content or other data 1300 typically present in a computing environment 900 in an unauthorized manner. A protected environment may protect against these attack vectors such that unauthorized access to trusted applications and the data they process is limited and resistance to attack is provided. Such attacks may be made by users of the system or mechanisms that may include executable code. The media application 100 is shown at the center of the diagram and the attack vectors 1307-1310 tend to focus on accessing sensitive data 1300 being stored and/or processed by the application 100.
A possible attack vector 1309 may be initiated via a malicious user mode application 1302. In the exemplary operating system architecture both the parent of a process, and any process with administrative privileges, typically have unlimited access to other processes, such as one processing media content, and the data they process. Such access to media content may be unauthorized. Thus a protected environment may ensure that a trusted application and the media content it processes are resistant to attacks by other user mode applications and/or processes.
A possible attack vector 1308 is the loading of malicious code 1303 into a process 1301. Having a secure process that is resistant to attacks from the outside is typically only as secure as the code running on the inside forming the process. Given that DLLs and other code are typically loaded into processes for execution, a mechanism that may ensure that the code being loaded is trusted to run inside a process before loading it into the process may be provided in a protected environment.
A possible vector of attack 1310 is through malicious kernel mode code 1304. Code running in kernel mode 904 typically has maximum privileges. The result may be that drivers running in kernel mode may have a number of opportunities to attack other applications. For instance, a driver may be able to access memory directly in another process. The result of this is that a driver could, once running, get access to a processes memory which may contain decrypted “encrypted media content” (FIG. 11, 1109). Kernel Mode attacks may be prevented by ensuring that the code running in the kernel is non-malicious code, as provided by this example.
A possible attack vector 1307 is by external attacks 1306 to the system 900. This group represents the set of attacks that typically do not require malicious code to be running on the system 900. For instance, attaching a debugger to an application and/or a process on the system, searching a machine 900 for sensitive data, etc. A protected environment may be created to resist these types of attacks.
FIG. 14 is a flow diagram showing the process 1400 for creating and maintaining a protected environment that tends to limit unauthorized access to media content and other data. The sequence 1400 begins when a computer system is started 1402 and the kernel of the operating system is loaded and a kernel secure flag is set 1404 to an initial value. The process continues through the time that a protected environment is typically created and an application is typically loaded into it 1406. The process includes periodic checking 1408 via the protected environment that seeks to ensure the system remains secure through the time the secure process is needed.
The term “kernel”, as used here, is defined as the central module of an operating system for a computing environment, system or device. The kernel module may be implemented in the form of computer-executable instructions and/or electronic logic circuits. Typically, the kernel is responsible for memory management, process and task management, and storage media management of a computing environment. The term “kernel component”, as used here, is defined to be a basic controlling mechanism, module, computer-executable instructions and/or electronic logic circuit that forms a portion of the kernel. For example, a kernel component may be a “loader”, which may be responsible for loading other kernel components in order to establish a fully operational kernel.
To summarize the process of creating and maintaining a protected environment:
1. Block 1402 represents the start-up of a computer system. This typically begins what is commonly known as the boot process and includes loading an operating system from disk or some other storage media.
2. Typically one of the first operations during the boot process is the loading of the kernel and its components. This example provides the validation of kernel components and, if all are successfully validated as secure, the setting of a flag indicating the kernel is secure. This is shown in block 1404.
3. After the computer system is considered fully operational a user may start an application such as a trusted media player which may call for a protected environment. This example provides a secure kernel with an application operating in a protected environment, as shown in block 1406.
4. Once the protected environment has been created and one or more of the processes of the application have been loaded into it and are operating, the trusted environment may periodically check the kernel secure flag to ensure the kernel remains secure, as shown in block 1408. That is, from the point in time that the trusted application begins operation, a check may be made periodically to determine whether any unauthorized kernel components have been loaded. Such unauthorized kernel components could attack the trusted application or the data it may be processing. Therefore, if any such components are loaded, the kernel secure flag may be set appropriately.
FIG. 15 is a block diagram showing exemplary kernel components 1520-1530 and other components 1510-1514 utilized in creating an exemplary secure computing environment 1000. This figure shows a computer system containing several components 1510-1530 typically stored on a disk or the like, several of which are used to form the kernel of an operating system when a computer is started. Arrow 1404 indicates the process of loading the kernel components into memory forming the operational kernel of the system. The loaded kernel 1550 is shown containing its various components 1551-1562 and a kernel secure flag 1590 indicating whether or not the kernel is considered secure for a protected environment. The kernel secure flag 1590 being described as a “flag” is not meant to be limiting; it may be implemented as a boolean variable or as a more complex data structure or mechanism.
Kernel components 1520-1530 are typically “signed” and may include certificate data 1538 that may enable the kernel to validate that they are the components they claim to be, that they have not been modified and/or are not malicious. A signature block and/or certificate data 1538 may be present in each kernel component 1520-1530 and/or each loaded kernel component 1560, 1562. The signature and/or certificate data 1538 may be unique to each component. The signature and/or certificate data 1538 may be used in the creation and maintenance of protected environments as indicated below. Typically a component is “signed” by its provider in such as way as to securely identify the source of the component and/or indicate whether it may have been tampered with. A signature may be implemented as a hash of the component's header or by using other techniques. A conventional certificate or certificate chain may also be included with a component that may be used to determine if the component can be trusted. The signature and/or certificate data 1538 are typically added to a component before it is distributed for public use. Those skilled in the art will be familiar with these technologies and their use.
When a typical computer system is started or “booted” the operating system's loading process or “kernel loader” 1551 will typically load the components of the kernel from disk or the like into a portion of system memory to form the kernel of the operating system. Once all of the kernel components are loaded and operational the computer and operating system are considered “booted” and ready for normal operation.
Kernel component # 1 1520 thru kernel component #n 1530, in the computing environment, may be stored on a disk or other storage media, along with a revocation list 1514, a kernel dump flag 1512 and a debugger 1510 along with a debug credential 1511. Arrow 1404 indicates the kernel loading process which reads the various components 1514-1530 from their storage location and loads them into system memory forming a functional operating system kernel 1550. The kernel dump flag 1512 being described as a “flag” is not meant to be limiting; it may be implemented as a boolean variable or as a more complex data structure or mechanism.
The kernel loader 1551 along with the PE management portion of the kernel 1552, the revocation list 1554 and two of the kernel components 1520 and 1522 are shown loaded into the kernel, the latter as blocks 1560 and 1562, along with an indication of space for additional kernel components yet to be loaded into the kernel, 1564 and 1570. Finally, the kernel 1550 includes a kernel secure flag 1590 which may be used to indicate whether or not the kernel 1550 is currently considered secure or not. This illustration is provided as an example and is not intended to be limiting or complete. The kernel loader 1551, the PE management portion of the kernel 1552 and/or the other components of the kernel are shown as distinct kernel components for clarity of explanation but, in actual practice, may or may not be distinguishable from other portions of the kernel.
Included in the computing environment 1000 may be a revocation list 1514 that may be used in conjunction with the signature and certificate data 1538 associated with the kernel components 1560 and 1562. This object 1514 may retain a list of signatures, certificates and/or certificate chains that are no longer considered valid as of the creation date of the list 1514. The revocation list 1514 is shown loaded into the kernel as object 1554. Such lists are maintained because a validly-signed and certified component, for example components 1560 and 1562, may later be discovered to have some problem. The system may use such a list 1554 to check kernel components 1520-1530 as they are loaded, which may be properly signed and/or have trusted certificate data 1538, but that may have subsequently been deemed untrustworthy. Such a revocation list 1554 will typically include version information 1555 so that it can more easily be identified, managed and updated as required.
Another component of the system that may impact kernel security is a debugger 1510. Debuggers may not typically be considered a part of the kernel but may be present in a computing environment 1000. Debuggers, including those known as kernel debuggers, system analyzers, and the like, may have broad access to the system and the processes running on the system along with any data present. A debugger 1510 may be able access any data in a computing environment 1000, including media content that should not be accessed in a manner other than that authorized. On the other hand, debugging is typically a part of developing new functionality and it should be possible to debug within protected environments the code intended to process protected media content. A debugger 1510 may thus include debug credentials 1511 which may indicate that the presence of the debugger 1510 on a system is authorized. Thus detection of the presence of a debugger 1510 along with any accompanying credentials 1511 may be a part of the creation and maintenance of protected environments (FIG. 14, 1400).
The computing environment 1000 may include a kernel dump flag 1512. This flag 1512 may be used to indicate how much of kernel memory is available for inspection in case of a catastrophic system failure. Such kernel dumps may be used for postmortem debugging after such as failure. If such a flag 1512 indicates that system memory is available for inspection upon a dump then the kernel 1550 may be considered insecure as hacker could run an application which exposes protected media in system memory and then force a catastrophic failure condition which may result in the system memory being available for inspection, including that containing the exposed media content. Thus a kernel dump flag 1512 may be used in the creation and maintenance of a protected environments (FIG. 14, 1400).
FIG. 16 and FIG. 17 are flow diagrams showing an exemplary process 1404 for loading kernel components to create an exemplary secure computing environment. This process 1404 begins after the kernel loader has been started and the PE management portion of the kernel has been loaded and made operational. Not shown in these figures, the PE management portion of the kernel may validate the kernel loader itself and/or any other kernel elements that may have been previously loaded. Validation is usually defined as determining whether or not a given component is considered secure and trustworthy as illustrated in part 2 of this process 1404.
The term “authorized for secure use” and the like as used below with respect to kernel components has the following specific meaning. A kernel containing any components that are not authorized for secure use does not provide a secure computing environment within which protected environments may operate. The opposite may not be true as it depends on other factors such as attack vectors.
1. Block 1601 shows the start of the loading process 1404 after the PE management portion of the kernel has been loaded and made operational. Any component loaded in the kernel prior to this may be validated as described above.
2. Block 1602 shows the kernel secure flag initially set to TRUE unless any component loaded prior to the PE management portion of the kernel, or that component itself, is found to be insecure at which point the kernel secure flag may be set to FALSE. In practice the indication of TRUE or FALSE may take various forms; the use of TRUE or FALSE here is only an example and is not meant to be limiting.
3. Block 1604 indicates a check for the presence of a debugger in the computing environment. Alternatively a debugger could reside remotely and be attached to the computing environment via a network or other communications media to a process in the computing environment. If no debugger is detected the loading process 1404 continues at block 1610. Otherwise it continues at block 1609. Not shown in the diagram, this check may be performed periodically and the state of the kernel secure flag updated accordingly.
4. If a debugger is detected, block 1606 shows a check for debug credentials which may indicate that debugging is authorized on the system in the presence of a protected environment. If such credentials are not present, the kernel secure flag may be set to FALSE as shown in block 1608. Otherwise the loading process 1404 continues at block 1610.
5. Block 1610 shows a check of the kernel dump flag. If this flag indicates that a full kernel memory dump or the like is possible then the kernel secure flag may be set to FALSE as shown in block 1608. Otherwise the loading process 1404 continues at block 1612. Not shown in the diagram, this check may be performed periodically and the state of the kernel secure flag updated accordingly.
6. Block 1612 shows the loading of the revocation list into the kernel. In cases where the revocation list may be used to check debug credentials, or other previously loaded credentials, signatures, certificate data, or the like, this step may take place earlier in the sequence (prior to the loading of credentials and the like to be checked) than shown. Not shown in the diagram is that, once this component is loaded, any and all previously loaded kernel components may be checked to see if their signature and/or certificate data has been revoked per the revocation list. If any have been revoked, the kernel secure flag may be set to FALSE and the loading process 1404 continues at block 1614. Note that a revocation list may or may not be loaded into the kernel to be used in the creation and maintenance of a protected environments.
7. Block 1614 shows the transition to part 2 of this diagram shown in FIG. 17 and continuing at block 1701.
8. Block 1702 shows a check for any additional kernel components to be loaded. If all components have been loaded then the load process 1404 is usually complete and the kernel secure flag remains in whatever state it was last set to, either TRUE or FALSE. If there are additional kernel components to be loaded the load process 1404 continues at block 1706.
9. Block 1706 shows a check for a valid signature of the next component to be loaded. If the signature is invalid then the kernel secure flag may be set to FALSE as shown in block 1718. Otherwise the loading process 1404 continues at block 1708. If no component signature is available the component may be considered insecure and the kernel secure flag may be set to FALSE as shown in block 1718. Signature validity may be determined by checking for a match on a list of valid signatures and/or by checking whether the signer's identity is a trusted identity. As familiar to those skilled in the security technology area, other methods could also be used to validate component signatures.
10. Block 1708 shows a check of the component's certificate data. If the certificate data is invalid then the kernel secure flag may be set to FALSE as shown in block 1718. Otherwise the loading process 1404 continues at block 1710. If no component certificate data is available the component may be considered insecure and the kernel secure flag may be set to FALSE as shown in block 1718. Certificate data validity may be determined by checking the component's certificate data to see if the component is authorized for secure use. As familiar to those skilled in the art, other methods could also be used to validate component certificate data.
11. Block 1710 shows a check of the component's signature against a revocation list. If the signature is present on the list, indicating that it has been revoked, then the kernel secure flag may be set to FALSE as shown in block 1718. Otherwise the loading process 1404 continues at block 1712.
12. Block 1712 shows a check of the component's certificate data against a revocation. If the certificate data is present on the list, indicating that it has been revoked, then the kernel secure flag may be set to FALSE as shown in block 1718. Otherwise the loading process 1404 continues at block 1714.
13. Block 1714 shows a check of the component's signature to determine if it is OK for use. This check may be made by inspecting the component's leaf certificate data to see if the component is authorized for secure use. Certain attributes in the certificate data may indicate if the component is approved for protected environment usage. If not the component may not be appropriately signed and the kernel secure flag may be set to FALSE as shown in block 1718. Otherwise the loading process 1404 continues at block 1716.
14. Block 1716 shows a check of the component's root certificate data. This check may be made by inspecting the component's root certificate data to see if it is listed on a list of trusted root certificates. If not the component may be considered insecure and the kernel secure flag may be set to FALSE as shown in block 1718. Otherwise the loading process 1404 continues at block 1720.
15. Block 1720 shows the loading of the component into the kernel where it is now considered operational. Then the loading process 1404 returns to block 1702 to check for any further components to be loaded.
FIG. 18 is a block diagram showing a secure computing environment 1000 loading an application 100 into an exemplary protected environment 230 to form a trusted application that may be resistant to attack. In this example the kernel may be the same as that described in FIG. 15, has already been loaded and the system 1000 is considered fully operational. At this point, as an example, a user starts media application 100. The media application 100 may call for the creation of a protected environment 230 for one or more of its processes and/or components to operate within. The protected environment creation process 1406 creates the protected environment 230 and loads the application 100 and/or its components as described below.
FIG. 19 is a flow diagram showing an exemplary process 1406 for creating a protected environment and loading an application into the protected environment. This process 1406 includes the initial step of creating a secure process followed by validating the software component to be loaded into it and then loading the software component into the new secure process and making it operational. Upon success, the result may be a software component operating in a protected environment supported by a secure kernel. Such a software component, along with any digital media content or other data it processes, may be protected from various attacks, including those described above.
1. Block 1901 shows the start of the protected environment creation process 1406. This point is usually reached when some application or code calls for a protected environment to operate.
2. Block 1902 shows the establishment of a protected environment. While not shown in the diagram, this may be accomplished by requesting the operating system to create a new secure process. Code later loaded and operating in this secure process may be considered to be operating in a protected environment. If the kernel secure flag is set to FALSE then the “create new secure process” request may fail. This may be because the system as a whole is considered insecure and unsuitable for a protected environment and any application or data requiring a protected environment. Alternatively, the “create new secure process” request may succeed and the component loaded into the new process may be informed that the system is considered insecure so that it can modify its operations accordingly. Otherwise the process 1406 continues at block 1906.
3. Block 1906 shows a check for a valid signature of the software component to be loaded into the new secure process or protected environment. If the signature is invalid then the process 1406 may fail as shown in block 1918. Otherwise the process 1406 continues at block 1908. Not shown in the process is that the program, or its equivalent, creating the new secure process may also be checked for a valid signature and the like. Thus, for either the component itself and/or the program creating the new secure process, if no signature is available the component may be considered insecure and the process 1406 may fail as shown in block 1918. Signature validity may be determined by checking for a match on a list of valid signatures and/or by checking whether the signer's identity is a trusted identity. As familiar to those skilled in the security technology area, other methods could also be used to validate component signatures.
4. Block 1908 shows a check of the software component's certificate data. If the certificate data is invalid then the process 1406 may fail as shown in block 1918. Otherwise the process 1406 continues at block 1910. If no component certificate data is available the component may be considered insecure and the process 1406 may fail as shown in block 1918. Certificate data validity may be determined by checking the component's certificate data to see if the component is authorized for secure use. As familiar to those skilled in the art, other methods could also be used to validate component certificate data.
Block 1910 shows a check of the component's signature against a revocation list. If the signature is present on the list, indicating that it has been revoked, then the process 1406 may fail as shown in block 1918. Otherwise the process 1406 continues at block 1912.
12. Block 1912 shows a check of the component's certificate data against the revocation list. If the certificate data is present on the list, indicating that it has been revoked, then the process 1406 may fail as shown in block 1918. Otherwise the process 1406 continues at block 1914.
13. Block 1914 shows a check of the component's signature to determine if it is acceptable for use. This check may be made by inspecting the component's leaf certificate data to see if the component is authorized for secure use. Certain attributes in the certificate data may indicate if the component is approved for protected environment usage. If not the component may be considered to not be appropriately signed and the process 1406 may fail as shown in block 1918. Otherwise the process 1406 continues at block 1916.
14. Block 1916 shows a check of the component's root certificate data. This check may be made by inspecting the component's root certificate data to see if it is listed on a list of trusted root certificates. If not the component may be considered insecure and the process 1406 may fail as shown in block 1918. Otherwise the process 1406 continues at block 1920.
15. Block 1918 shows the failure of the software component to load followed by block 1930, the end of the protected environment creation process 1406.
16. Block 1920 shows the software component being loaded into the protected environment, where it is considered operational, followed by block 1930, the end of the protected environment creation process 1406.
FIG. 20 is a block diagram showing an exemplary trusted application utilizing an exemplary protected environment 230 periodically checking 1408 the security state 1590 of the secure computing environment 1000. In this example, the computing environment 1000 and the kernel 1550 may be the same as those described in FIG. 15 and FIG. 16. The kernel 1550 has already been loaded and the computer 1000 is considered fully operational. Further, a protected environment has been created and the appropriate components of the trusted application have been loaded into it and made operational, establishing a trusted application utilizing a protected environment 230, hereafter referred to simply as the “protected environment”.
The protected environment 230 may periodically check with the PE management portion of the kernel 1552 to determine whether the kernel 1550 remains secure over time. This periodic check may be performed because it is possible for a new component to be loaded into the kernel 1550 at any time, including a component that may be considered insecure. If this were to occur, the state of the kernel secure flag 1590 may change to FALSE and the code operating in the protected environment 230 has the opportunity to respond appropriately.
For example, consider a media player application that was started on a PC 1000 with a secure kernel 1550 and a portion of the media player application operating in a protected environment 230 processing digital media content that is licensed only for secure use. In this example, if a new kernel component that is considered insecure is loaded while the media player application is processing the media content, then the check kernel secure state process 1040 would note the kernel secure flag 1590 has changed to FALSE indicating the kernel 1550 may no longer be secure.
Alternatively, the revocation list 1545 may be updated and a kernel component previously considered secure may no longer be considered secure, resulting in the kernel secure flag 1590 being set to FALSE. At this point the application may receive notification that the system 1000 is no longer considered secure and can terminate operation, or take other appropriate action to protect itself and/or the media content it is processing.
FIG. 21 is a flow diagram showing an exemplary process 1408 for periodically checking the security state of the secure computing environment. This process 1408 may be used by a protected environment 230 to determine if the kernel remains secure over time. The protected environment 230 may periodically use this process 1408 to check the current security status of the kernel. The protected environment 230 and/or the software component operating within it may use the current security status information to modify its operation appropriately. Periodic activation of the process may be implemented using conventional techniques.
The diagram in FIG. 21 shows a sequence of communications 1408, illustrated with exemplary pseudo code, between the protected environment 230 and the PE management portion of the kernel 1552. This communication may include a check of the version of a revocation list which may give an application the ability to specify a revocation list of at least a certain version. This communications sequence may be cryptographically secured using conventional techniques.
1. The protected environment 230 makes a IsKernelSecure(MinRLVer) call 2120 to the PE management portion of the kernel to query the current security state of the kernel. Included in this call 2120 may be the minimum version (MinRLVer) of the revocation list expected to be utilized.
2. The PE management portion of the kernel checks to see if the protected environment, which is the calling process, is secure. If not, then it may provide a Return(SecureFlag=FALSE) indication 2122 to the protected environment and the communications sequence 1408 is complete. This security check may be done by the PE management portion of the kernel checking the protected environment for a valid signature and/or certificate data as described above.
3. Otherwise, the PE management portion of the kernel checks the kernel secure flag in response to the call 2120. If the state of the flag is FALSE then it may provide a Return(SecureFlag=FALSE) indication 2124 to the protected environment and the communications sequence 1408 is complete.
4. Otherwise, the PE management portion of the kernel checks the revocation list version information for the revocation list. If the revocation list has version information that is older than that requested in the IsKernelSecure(MinRLVer) call 2120 then several options are possible. First, as indicated in the diagram, the PE management portion of the kernel may provide a Return(SecureFlag=FALSE) indication 2126 to the protected environment and the communications sequence 1408 is complete.
Alternatively, and not shown in the diagram, an appropriate version revocation list may be located and utilized, all kernel components may be re-validated using this new or updated list, the kernel secure flag updated as appropriate and the previous step # 3 of this communications sequence 1408 repeated.
5. Otherwise, the PE management portion of the kernel may provide a Return(SecureFlag=TRUE) indication 2128 to the protected environment and the communications sequence 1408 is complete.
FIG. 22 is a block diagram showing an exemplary computing environment 800 including a representation of a protected environment 230, a trusted media system 200, and other related elements. Exemplary personal computer 800 is similar to that shown in FIG. 8 with the addition of kernel components 1520-1530 that may be stored on the disk 810 along with the other operating system code and the like. Media application 100 and/or a digital rights management system 1004 may be stored on the disk 810 along with other application programs. These components 1520-1530 and applications 100, 1004 may be loaded into system memory 809 and considered operational. Shown loaded in system memory 809 is a trusted application 200 utilizing a protected environment 230 and media content 110.

Claims

1. A computing device comprising:

a processor;

memory coupled to the processor;

a protected media pipeline implemented at least in part by the processor and the memory, the protected media pipeline configured to process digital media, the protected media pipeline comprising:

a media source coupled to a first secure connection over which the digital media is received via the media source into the protected media pipeline; and

a media sink coupled to a second secure connection over which processed digital media is transferred via the media sink out of the protected media pipeline.

2. The computing device of claim 1 coupled to a protected input via the first secure connection and via which the digital media is initially received into the computing device, where the protected input is configured to limit unauthorized access to the digital media.

3. The computing device of claim 1 coupled to a protected output via the second secure connection and via which the processed digital media is transferred from the computing device, where the protected output is configured to limit unauthorized access to the processed digital media.

4. The computing device of claim 1 where the first secure connection is configured to limit unauthorized access to the digital media.

5. The computing device of claim 1 where the second secure connection is configured to limit unauthorized access to the processed digital media.

6. The computing device of claim 1, the protected media pipeline further comprising a protected space that includes at least one transform mechanism that is configured to transform the digital media, where the protected space is configured to limit unauthorized access to the digital media and the processed digital media.

7. The computing device of claim 1, where the protected media pipeline is configured to limit unauthorized access to the digital media and the processed digital media.

8. A method performed on a computing device that comprises a processor, memory, and a protected media pipeline that is configured to process digital media, the method comprising:

receiving, by a media source over a first secure connection into the protected media pipeline, the digital media, where the media source is a component of the protected media pipeline;

transferring, by a media sink over a second secure connection out of the protected media pipeline, processed digital media, where the media sink is a component of the protected media pipeline.

9. The method of claim 9, the receiving based on the computing device being coupled to a protected input via the first secure connection and via which the digital media is initially received into the computing device, where the protected input is configured to limit unauthorized access to the digital media.

10. The method of claim 9, the transferring based on the computing device being coupled to a protected output via the second secure connection and via which the processed digital media is transferred from the computing device, where the protected output is configured to limit unauthorized access to the processed digital media.

11. The method of claim 9 where the first secure connection is configured to limit unauthorized access to the digital media.

12. The method of claim 9 where the second secure connection is configured to limit unauthorized access to the processed digital media.

13. The method of claim 9 further comprising transforming, by at least one transform mechanism, the digital media, where the at least one transform mechanism is a component of a protected space of the protected media pipeline, where the protected space is configured to limit unauthorized access to the digital media and the processed digital media.

14. The method of claim 9, where the protected media pipeline is configured to limit unauthorized access to the digital media and the processed digital media.

15. At least on computer-readable media that comprises:

memory that includes computer-executable instructions that, based on execution by a computing device that comprises a protected media pipeline that is configured to process digital media, configure the computing device to perform actions comprising:

receiving, via a media source over a first secure connection into the protected media pipeline, the digital media, where the media source is a component of the protected media pipeline;

transferring, via a media sink over a second secure connection out of the protected media pipeline, processed digital media, where the media sink is a component of the protected media pipeline.

16. The at least on computer-readable media of claim 15, the receiving based on the computing device being coupled to a protected input via the first secure connection and via which the digital media is initially received into the computing device, where the protected input is configured to limit unauthorized access to the digital media.

17. The at least on computer-readable media of claim 15, the transferring based on the computing device being coupled to a protected output via the second secure connection and via which the processed digital media is transferred from the computing device, where the protected output is configured to limit unauthorized access to the processed digital media.

18. The at least on computer-readable media of claim 15 where the first secure connection is configured to limit unauthorized access to the digital media, or where the second secure connection is configured to limit unauthorized access to the processed digital media.

19. The at least on computer-readable media of claim 15, the actions further comprising transforming, by at least one transform mechanism, the digital media, where the at least one transform mechanism is a component of a protected space of the protected media pipeline, where the protected space is configured to limit unauthorized access to the digital media and the processed digital media.

20. The at least on computer-readable media of claim 15, where the protected media pipeline is configured to limit unauthorized access to the digital media and the processed digital media.