Virus resistant and hardware independent method of flashing system bios

• US 6,715,074 B1
• Filed: 07/27/1999
• Issued: 03/30/2004
• Est. Priority Date: 07/27/1999
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Chaiken, Craig L.
• Primary Examiner(s): HUA, LY
• Application Number:
  US09/362,077
• Time in Patent Office: 1,708 Days
• Field of Search: 713/164, 713/165, 713/166, 713/167, 713/187, 713/168, 713/200, 713/2, 713/1, 713/100, 713/189, 713/193, 714/6, 714/36, 714/11, 711/100, 711/103, 711/102, 711/104, 711/163, 705/76, 705/57, 380/285
• US Class Current: 713/164
• CPC Class Codes: G06F 21/572 Secure firmware programming, e.g. of basic input output system [BIOS]
• CPC Class Codes: G06F 8/60 Software deployment
• CPC Class Codes: G06Q 20/3821 Electronic credentials

Abstract

A system and method for making sure that before the ROM BIOS of a personal computer is reprogrammed, the BIOS image is compatible with the computer whose BIOS are being reprogrammed. This is done by requiring the utility that performs the reprogramming of the ROM BIOS to have a secure portion of code that is stored in a portion of the computer'"'"'s memory that is inaccessible to a user. The secure portion of code is used to make sure that the BIOS image to be programmed into the computer is compatible with the computer.

Claims

1. A computer system comprising:

a hard disk drive for receiving and storing a BIOS image;

a Flash ROM BIOS part adapted to be flashed with said BIOS image;

a RAM memory for receiving and storing said BIOS image from said hard disk when said BIOS image is to be flashed into said Flash ROM BIOS part, said BIOS image including a flash signature and encoded information for verification that said BIOS image is compatible with a particular computer system;

a utility program operable to generate a software SMI by writing at least part of said flash signature to an SMI port; and

a software SMI handler program responsive to said software SMI for determining whether said BIOS image is a certified BIOS image for a particular computer system and on determination of a certified BIOS image, allowing said- BIOS image to be flashed into said Flash ROM BIOS part.

2. The computer system of claim 1, wherein said software SMI handler program further includes a code that is substantially inaccessible to a computer user.

3. The computer system of claim 1, wherein said software SMI handler can only be, accessed via a software-SMI interrupt.

4. The computer system of claim 1, wherein said BIOS image encoded information comprises at least an encrypted portion, said encrypted portion being decrypted by said software SMI handler program.

5. The computer system of claim 1, wherein said BIOS image encoded information comprises at least one of a CRC and a check sum.

6. The computer system of claim 1, wherein said software SMI handler program is a hardware independent program.

7. The computer system of claim 1, wherein said software SMI handler program is stored in a system management memory segment of memory.

8. The computer system of claim 1, wherein said software SMI handler program exists in a compressed format resistant to disassembly.

9. A method for flashing a ROM BIOS part in a computer system, said method comprising the steps of:

determining a Flash BIOS file name and a Flash BIOS file size for a ROM BIOS to be flashed;

determining a software SMI port location;

placing a BIOS image having said determined Flash BIOS file name and said Flash BIOS file size into RAM, said BIOS image including encoded information for verification that said BIOS image is compatible with said computer system;

using a flash BIOS signature to indicate that flashing said BIOS is intentional;

generating a software SMI interrupt;

in response to said software SMI, determining whether said flash BIOS signature is valid and, if valid, executing a specific code during said software SMI interrupt to determine on the basis of said encoded information whether said BIOS image is a certified BIOS image for said computer system; and

flashing said ROM BIOS part if said BIOS image is determined to be said certified BIOS image.

10. The method for flashing said ROM BIOS part in said computer system of claim 9, wherein said BIOS image having said determined Flash BIOS file name and said Flash BIOS file size is placed in a continuous block of RAM.

11. The method for flashing said ROM BIOS part in said computer system of claim 9, wherein said step of executing a specific code includes a step of decrypting a predetermined encrypted portion of said BIOS image.

12. The method for flashing said ROM BIOS part in said computer system of claim 9, wherein said step of executing a specific code includes a step of checking at least one of a check sum and a CRC found in a predetermined portion of said encoded information of said BIOS image.

13. A method for reprogramming a ROM BIOS part in a computer system, said method comprising the steps-of:

determining whether a user intentionally initiated a ROM BIOS part reprogramming;

after determining that initiation of a ROM BIOS part in the computer system was intentionally initiated, establishing that a ROM BIOS image is a certified ROM BIOS image that is compatible with said computer system; and

reprogramming said ROM BIOS part if said ROM BIOS image is established to be a certified ROM BIOS image for said computer system.

14. The method for reprogramming said ROM BIOS part in a computer system of claim 13, wherein said step of determining utilizes a program initiated by a software SMI to make the determination.

15. The method for reprogramming said ROM BIOS part in a computer system of claim 13, wherein said step of establishing comprises a step of running software stored in a system management memory segment of a RAM in response to a software SMI.

16. The method for reprogramming said ROM BIOS part in a computer system of claim 13, wherein said step of establishing comprises a step of decrypting at least a predetermined portion of said BIOS image with a private key.

17. The method for reprogramming said ROM BIOS part in a computer system of claim 13, wherein said step of reprogramming said ROM BIOS part includes a step of flashing said ROM BIOS part with said ROM BIOS image.