Protected boot flow

• US 6,711,675 B1
• Filed: 02/11/2000
• Issued: 03/23/2004
• Est. Priority Date: 02/11/2000
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Stevens, William A. Jr., Gafken, Andrew H., Hale, Robert P., Spiegel, Christopher J.
• Primary Examiner(s): BUTLER, DENNIS
• Application Number:
  US09/503,046
• Time in Patent Office: 1,502 Days
• Field of Search: 713/2, 713/1, 713/200, 713/202
• US Class Current: 713/2
• CPC Class Codes: G06F 21/575 Secure boot
• CPC Class Codes: G06F 9/4401 Bootstrapping security arrangements therefor G06F21/57

Abstract

A protected boot sequence in a computer system. A reset vector directs the system to a boot program including a protected program. This protected program verifies the integrity of the BIOS contents before branching to the BIOS for execution of normal bootstrap functions. The protected program can also lock down various blocks of bootstrap code to prevent them from being changed after a certain point in the boot sequence. The protected boot sequence can proceed in layers, with each layer providing some level of validation or security for succeeding layers.

Claims

1. A method of booting software in a computer system, comprising:

initiating a reset function;

executing a first protected program;

validating a firmware-based BIOS program with code that cannot be updated by the computer system by verifying the BIOS program contains expected code;

locking down portions of at least one of the first protected program and the BIOS program; and

executing the BIOS program.

2. The method of claim 1, wherein said executing the BIOS program includes validating and executing an operating system loader.

3. The method of claim 1, wherein said validating includes locating the BIOS program.

4. The method of claim 1, wherein said initiating includes branching to an entry point of a boot sequence in the first protected program.

5. The method of claim 1, wherein said executing the BIOS program includes initializing a main memory.

6. The method of claim 1, wherein said executing the BIOS program includes determining a reset type.

7. The method of claim 1, wherein said validating the BIOS program includes validating and installing updated modules.

8. The method of claim 1, wherein said validating the BIOS program includes validating a second protected program, and executing the BIOS program includes executing the second protected program.

9. The method of claim 8, wherein the second protected program is an option ROM program.

10. A method of booting software in a computer system, comprising:

initiating a reset function;

executing a first protected program that cannot be updated by the computer system;

validating, through said executing a first protected program, at least one of first and second firmware-based BIOS programs by verifying the at least one of the first and second BIOS programs contains expected code;

executing the first BIOS program;

executing a second protected program; and

executing the second BIOS program, wherein at least one of said executing the first protected program and said executing the second protected program includes locking down blocks of data in at least one of said first protected program, said second protected program, said first BIOS program, and said second BIOS program.

11. The method of claim 10, wherein said initiating includes branching to an entry point of a boot sequence in the first protected program.

12. The method of claim 10, wherein said executing the first BIOS program includes initializing a main memory.

13. The method of claim 10, wherein said executing the first BIOS program includes determining a reset type.

14. The method of claim 10, wherein said executing the second protected program includes loading additional security elements into memory.

15. The method of claim 10, wherein at least one of said executing the first BIOS program and said executing the second BIOS program includes validating an operating system loader.

16. The method of claim 15, further comprising executing the operating system loader.

17. The method of claim 10, wherein said validating includes validating an option ROM.

18. The method of claim 17, wherein said executing at least one of the first and second BIOS programs includes executing a validated option ROM program.

19. The method of claim 10, wherein said validating includes validating and installing updated modules.

20. A machine-readable medium having stored thereon instructions, which when executed by at least one processor causes said at least one processor to perform the following:

initiating a reset function;

executing a protected program that cannot be updated by the at least one processor;

validating, by said executing a protected program, a firmware-based BIOS program by verifying the BIOS program contains expected code;

locking down portions of at least one of said protected program and said BIOS program; and

executing the BIOS program.

21. The medium of claim 20, wherein said executing the BIOS program includes validating and executing an operating system loader.

22. The medium of claim 20, wherein said validating includes locating the BIOS program.

23. The medium of claim 20, wherein said initiating includes branching to an entry point of a boot sequence in the first protected program.

24. The medium of claim 20, wherein said validating the BIOS program includes validating a second protected program, and executing the BIOS program includes executing the second protected program.

25. The medium of claim 20, wherein said validating the BIOS program includes validating and installing updated modules.

26. An apparatus, comprising:

a first firmware-based memory block containing a protected first program sequence; and

a second firmware-based memory block containing a second program sequence for booting a computer system;

wherein the first program sequence includes instructions for validating the second program sequence by verifying the second program sequence contains expected code and for transferring control to the second program sequence;

wherein the protected first program sequence cannot be updated by the computer system;

wherein the first program sequence includes instructions for locking down at least one of a portion of the first memory block and a portion of the second memory block.

27. The apparatus of claim 26, wherein the second program sequences includes instructions for locking down at least one of a portion of the first memory block and a portion of the second memory block.

28. The apparatus of claim 26, wherein at least one of the first and second program sequences includes instructions for validating an option ROM.

29. The apparatus of claim 26, wherein at least one of the first and second program sequences includes instructions for validating and installing updated modules.

30. The apparatus of claim 26, wherein the first program sequence includes instructions for locating the second program sequence.

31. The apparatus of claim 26, wherein the second program sequence includes a BIOS program sequence.