Trusting an unverified code image in a computing device

• US 8,826,405 B2
• Filed: 09/15/2012
• Issued: 09/02/2014
• Est. Priority Date: 01/07/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: de Cesare, Joshua, Smith, Michael, De Atley, Dallas Blake, Wright, John Andrew
• Primary Examiner(s): SHAW, BRIAN F
• Application Number:
  US13/621,183
• Publication Number:
  US 20130081124A1
• Time in Patent Office: 717 Days
• Field of Search: 726/7, 726/26, 726/30, 726/27, 713/156, 713/193, 713/167, 380/239, 711/E12.001, 711/154
• US Class Current: 726/7
• CPC Class Codes: G06F 21/00 Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
• CPC Class Codes: G06F 21/575 Secure boot

Abstract

A method and an apparatus for configuring a key stored within a secure storage area (e.g., ROM) of a device including one of enabling and disabling the key according to a predetermined condition to execute a code image are described. The key may uniquely identify the device. The code image may be loaded from a provider satisfying a predetermined condition to set up at least one component of an operating environment of the device. Verification of the code image may be optional according to the configuration of the key. Secure execution of an unverified code image may be based on a configuration that disables the key.

Claims

1. A computer implemented method, comprising:

executing a trusted code image in a device, wherein the trusted code image comprises a trusted boot image that relates to long term power management associated with the device or a trusted boot image that causes hardware initialization for an operating environment associated with the device, the trusted code image is configured to disable access to a unique identifier stored within a memory of the device, and the unique identifier uniquely identifies the device and is used to verify an unverified application code image,

wherein said executing includes disabling the unique identifier according to a predetermined condition that is preconfigured by a vendor associated with the device, wherein the disabling involves preventing the unverified application code image from accessing device hardware of the device, and wherein the device hardware is accessed by having the unique identifier enabled and by reading or setting one or more values of one or more device hardware parameters of the device;

loading, subsequent to the execution of the trusted code image, the unverified application code image into the device for execution without verifying the unverified application code image according to the unique identifier;

in response to a request to access the device hardware based on the execution of the unverified application code image, executing a secure code in the memory to determine whether the unique identifier is enabled to grant the request to access the device hardware; and

in response to a determination that the unique identifier is disabled, continuing the execution of the unverified application code image without access to the device hardware.

2. The method of claim 1, further comprising verifying, prior to the executing of the trusted code image, the trusted code image in the device according to the unique identifier stored within the memory of the device, wherein the executing comprises executing the trusted code image in response to successfully verifying the trusted code image.

3. The method of claim 1, wherein the trusted code image is loaded from a provider to set up at least one component of an operating environment of the device, the provider satisfying the predetermined condition.

4. The method of claim 1, further comprising, in response to the determination that the unique identifier is disabled, blocking the access to the device hardware based on a configuration associated with the unique identifier, wherein the memory is a ROM (Read Only Memory), and the configuration is specified according to a diagnostic or testing requirement of the device.

5. The method of claim 4, wherein the configuration is related to a hardware switch of the device.

6. The method of claim 1, wherein the unverified application code image is verified based on the secure code.

7. The method of claim 1, wherein the loading of the unverified application code image comprises loading the unverified application code image in the memory of the device without verifying the unverified application code image according to the unique identifier.

8. The method of claim 7, further comprising executing the unverified application code image for an access to the unique identifier.

9. The method of claim 8, wherein the access to the unique identifier is based on an application programming interface called from the unverified application code image.

10. The method of claim 7, wherein the loading of the unverified application code image comprises:

deriving a hash value of the unverified application code image; and

determining whether the unverified application code image is corrupted based on a header value from the unverified application code image and the hash value.

11. The method of claim 1, wherein the unverified application code image comprises diagnostic software for the device.

12. A system comprising:

a processor; and

a memory configured to store computer executable instructions that, when executed by the processor, cause the processor to;

execute a trusted code image in a device, wherein the trusted code image comprises a trusted boot image that relates to long term power management associated with the device or a trusted boot image that causes hardware initialization for an operating environment associated with the device, the trusted code image is configured to disable access to a unique identifier stored within a memory of the device, and the unique identifier uniquely identifies the device and is used to verify an unverified application code image, wherein the instructions further cause the processor to disable the unique identifier according to a predetermined condition that is preconfigured by a vendor associated with the device, wherein the disabling involves preventing the unverified application code image from accessing device hardware of the device, and wherein the device hardware is accessed by having the unique identifier enabled and by reading or setting one or more values of one or more device hardware parameters of the device;

load, subsequent to the execution of the trusted code image, the unverified application code image into the device for execution without verifying the unverified application code image according to the unique identifier;

in response to a request to access device hardware based on the execution of the unverified application code image, execute a secure code in the memory to determine whether the unique identifier is enabled to grant the request to access the device hardware; and

in response to a determination that the unique identifier is disabled, continue the execution of the unverified application code image without access to the device hardware.

13. The system of claim 12, wherein the executable instructions further cause the processor to verify, prior to executing the trusted code image, the trusted code image in the device according to the unique identifier stored within the memory of the device, wherein executing the trusted code image comprises executing the trusted code image in response to successfully verifying the trusted code image.

14. The system of claim 12, wherein the trusted code image is loaded from a provider to set up at least one component of an operating environment of the device, the provider satisfying the predetermined condition.

15. The system of claim 12, wherein the executable instructions further cause the processor to, in response to the determination that the unique identifier is disabled, block the access to the device hardware based on a configuration associated with the unique identifier, wherein the memory is a ROM (Read Only Memory), and the configuration is specified according to a diagnostic or testing requirement of the device.

16. A non-transitory machine-readable storage medium configured to store instructions that, when executed by a processor included in a computing device, cause the computing device to carry out steps that include:

executing a trusted code image in the computing device, wherein the trusted code image comprises a trusted boot image that relates to long term power management associated with the device or a trusted boot image that causes hardware initialization for an operating environment associated with the device, the trusted code image is configured to disable access to a unique identifier stored within a memory of the computing device, and the unique identifier uniquely identifies the computing device and is used to verify an unverified application code image, wherein said executing the trusted code image includes disabling the unique identifier according to a predetermined condition that is preconfigured by a vendor associated with the computing device, wherein the disabling involves preventing the unverified application code image from accessing device hardware of the computing device, and wherein the device hardware is accessed by having the unique identifier enabled and by reading or setting values of device hardware parameters of the device;

loading, subsequent to the execution of the trusted code image, the unverified application code image into the computing device for execution without verifying the application code image according to the unique identifier; and

in response to a request to access the device hardware based on the execution of the unverified application code image, executing a secure code in the memory to determine whether the unique identifier is enabled to grant the request to access the device hardware; and

in response to a determination that the unique identifier is disabled, continuing the execution of the unverified application code image without access to the device hardware.

17. The non-transitory machine-readable storage medium of claim 16, wherein the steps further include, in response to the determination that the unique identifier is disabled, blocking the access to the device hardware based on a configuration associated with the unique identifier, wherein the memory is a ROM (Read Only Memory), and the configuration is specified according to a diagnostic or testing requirement of the computing device.