Systems and methods for updating a secure boot process on a computer with a hardware security module

• US 8,028,172 B2
• Filed: 01/14/2005
• Issued: 09/27/2011
• Est. Priority Date: 01/14/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Schwartz, Jonathan, Hunter, Jamie, Schwartz, James Anthony Jr., England, Paul, Ray, Kenneth D., Thom, Stefan, Humphries, Russell
• Primary Examiner(s): TRAN, ELLEN C
• Application Number:
  US11/036,018
• Publication Number:
  US 20060161784A1
• Time in Patent Office: 2,447 Days
• Field of Search: 726/16, 713/164, 713/193, 713/194
• US Class Current: 713/193
• CPC Class Codes: G06F 21/575 Secure boot

Abstract

Systems and methods are provided for maintaining and updating a secure boot process on a computer with a trusted platform module (TPM). A boot process may be maintained by inspecting a log of TPM activity, determining data that prevented a secret to unseal, and returning the data to an original state. In situations where this type of recovery is not workable, techniques for authenticating a user may be used, allowing the authenticated user to bypass the security features of the boot process and reseal the boot secrets to platform configuration register (PCR) values that may have changed. Finally, a secure boot process may be upgraded by migrating TPM sealed secrets to a temporary storage location, updating one or more aspects of a secure boot process, and resealing the secrets to the resulting new platform configuration. Other advantages and features of the invention are described below.

Claims

1. A computer readable medium, wherein the computer readable medium is not a transitory signal, bearing instructions for a computer, said computer comprising a Hardware Security Module (HSM) that accesses recorded values, compares submitted values indicative of at least one measurement to the recorded values, and releases a sealed secret (a released secret) if the submitted values match the recorded values, said computer readable medium comprising:

A. instructions for securely booting a computer, comprising;

i. instructions for measuring data involved in a boot process;

ii. instructions for submitting a measurement of said data to the HSM;

iii. instructions for requesting release of the sealed secret from the HSM, wherein said instructions for securely booting a computer cannot successfully complete a normal boot operation without said secret; and

iv. releasing the sealed secret only if the measurement submitted to the HSM is correct when compared to a recorded value, wherein the released sealed secret is different from the measurement and the recorded value; and

B. instructions for updating said data involved in a boot process, comprising;

i. instructions for migrating the released secret to temporary storage where it remains while the data involved in the boot process is updated;

ii. instructions for measuring updated data involved in the boot process; and

iii. instructions for restricting access to the migrated released secret by resealing it using the measurement of the updated data involved in the boot process, wherein the secret may be subsequently obtained by submitting at least a measurement of said updated data to the HSM.

2. The computer readable medium of claim 1 wherein the HSM is a Trusted Platform Module (TPM).

3. The computer readable medium of claim 1 wherein the data is at least one of a software and a data component.

4. The computer readable storage medium of claim 1 wherein said instructions for measuring data comprise instructions for computing a hash of the data.

5. The computer readable storage medium of claim 1 wherein said instructions for submitting a measurement comprise instructions for extending a platform configuration register (PCR).

6. The computer readable storage medium of claim 1 wherein the instructions for restricting access to the secret use an anticipated measurement of the updated data.

7. The computer readable storage medium of claim 1, the instructions for updating said data involved in a boot process further comprising instructions for rebooting the computer.

8. A method for recovering a secure computer boot process on a computer comprising a Hardware Security Module (HSM) that accesses recorded values, compares submitted values indicative of at least one measurement to the recorded values, and releases a sealed secret (a released secret) if the submitted values are correct, said method comprising:

A. securely booting a computer, comprising;

i. measuring data involved in a boot process;

ii. submitting a measurement of said data to the HSM;

iii. requesting release of the sealed secret from the HSM, wherein said instructions for securely booting a computer cannot successfully complete a normal boot operation without said secret;

iv. releasing the sealed secret only if the measurement submitted to the HSM is correct when compared to a recorded value, wherein the released sealed secret is different from the measurement and the recorded value;

B. updating said data involved in a boot process, comprising;

i. migrating the released secret to temporary storage where it remains while the data involved in the boot process is updated;

ii. measuring updated data involved in the boot process;

iii. restricting access to the migrated released secret by resealing it using the measurement of the updated data involved in the boot process, wherein the secret may be subsequently obtained by submitting at least a measurement of said updated data to the HSM.

9. The method of claim 8 wherein the HSM is a Trusted Platform Module (TPM).

10. The method of claim 8 wherein the data is a software component.

11. The method of claim 8 wherein said measuring data comprises computing a hash of the data.

12. The method of claim 8 wherein said submitting a measurement comprises extending a platform configuration register (PCR).

13. The method of claim 8 wherein an anticipated measurement of the updated data involved in the boot process is used when resealing the migrated released secret.

14. The method of claim 8, the step of updating said data involved in a boot process further comprising rebooting the computer.

15. A computer comprising a Hardware Security Module (HSM) that accesses recorded values, compares submitted values indicative of at least one measurement to the recorded values, and releases a sealed secret (a released secret) if the submitted values are correct, said computer comprising:

A. means for securely booting a computer, comprising;

i. means for measuring data involved in a boot process;

ii. means for submitting a measurement of said data to the HSM;

iii. means for requesting release of the sealed secret from the HSM, wherein said means for securely booting a computer cannot successfully complete a normal boot operation without said secret;

iv. means for releasing the sealed secret only if the measurement submitted to the HSM is correct when compared to a recorded value, wherein the released sealed secret is different from the measurement and the recorded value;

B. means for updating said data involved in a boot process, comprising;

i. means for migrating the released secret to temporary storage where it remains while the data involved in the boot process is updated;

ii. means for measuring updated data involved in the boot process;

iii. means for restricting access to the migrated released secret by resealing it using the measurement of the updated data involved in the boot process, wherein the secret may be subsequently obtained by submitting at least a measurement of said updated data to the HSM.

16. The computer of claim 15 wherein the HSM is a Trusted Platform Module (TPM).

17. The computer of claim 15 wherein the data is a software component.

18. The computer of claim 15 wherein said means for measuring data comprise means for computing a hash of the data.

19. The computer of claim 15 wherein said means for submitting a measurement comprise means for extending a platform configuration register (PCR).

20. The computer of claim 15, the means for updating said data involved in a boot process further comprising means for rebooting the computer.