Abstract:
An update utility requests a signature verification of the utility&#39;s signature along with a request to unlock the flash memory stored in the utility. A trusted platform module (“TPM”) performs a signature verification of the utility using a previously stored public key. Upon verification of the signature, the TPM unlocks the flash memory to permit update of the utility. Upon completion of the update, the flash utility issues a lock request to the TPM to relock the flash memory.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application relates to U.S. patent application Ser. No. 09/931,550, entitled “System Management Interrupt Generation Upon Completion of Cryptographic Operation”; and 
   U.S. patent application Ser. No. 09/931,531, entitled “Proving BIOS Trust in a TCPA Compliant System,” which are hereby incorporated by reference herein. 
   TECHNICAL FIELD 
   The present invention relates in general to information handling systems, and in particular, to the update of information in an information handling system. 
   BACKGROUND INFORMATION 
   The Basic Input/Output System (BIOS) of a computer is the backbone of the operation of that computer. The BIOS is programming that controls the basic hardware operations of the computer, including interaction with floppy disk drives, hard disk drives and the keyboard. Because of ever changing computer technologies, even though a computer may still be acceptable to a user, often the BIOS of that computer will not support all of the new technologies. 
   A conventional method for upgrading the BIOS code or image of a computer is to physically replace the Read-Only-Memory (ROM) based BIOS, which in networks systems, would entail replacing the ROM-BIOS in each processor node, which is very time consuming and adds to the overall system down-time of the network. 
   There have been solutions for updating a BIOS image associated with a processor without having to physically replace the ROM-BIOS at each computer in the network. For example, one solution is to provide the computer with a Flash EPROM for the BIOS, also known as a Flash BIOS. With a Flash BIOS, the BIOS image or a portion of the BIOS image can be updated by a software update. This is often performed by downloading or storing the Flash information onto a media storage device, such as a floppy disk, and using the disk at each computer to flash the BIOS. However, this is very time consuming, especially with large network systems. Further, some of the computers on the network may not have floppy drives or the proper medium transfer device. 
   A second method is to send the flash over the network to each computer in the network. The problem with this method is that the flash is subject to someone introducing malicious code, such as a virus, to the flash, thereby causing the BIOS to be flashed with a corrupt image. 
   Yet another method includes transferring the flash information from the source computer to the receiving computer, with the flash information including the flash code, the flash code instructions and an encrypted digital signature corresponding to the identification of the flash code. The sender is authenticated and then the receiving computer is operably placed in a secure mode. A hash value corresponding to the flash information is calculated, and the digital signature from the flash information is decrypted. The flash code is validated by comparing the digital signature of the flash information to the calculated hash, and if validated, the BIOS is flashed with the new flash code, the new flash code is verified, and the computer re-booted power cycled. 
   As a result, there is a need in the art for a more secure procedure for updating a utility within the data processing system. 
   SUMMARY OF THE INVENTION 
   The present invention addresses the foregoing need by having an update utility request a signature verification of the utility&#39;s signature along with a request to unlock the flash memory. A trusted platform module (“TPM”) performs a signature verification of the utility using a previously stored public key. Upon verification of the signature, the TPM unlocks the flash memory to permit update of the utility. Upon completion of the update, the flash utility issues a lock request to the TPM to relock the flash memory. 
   The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
       FIGS. 1-2  illustrate flow diagrams configured in accordance with the present invention; and 
       FIG. 3  illustrates an information handling system configured in accordance with the present invention. 
   

   DETAILED DESCRIPTION 
   In the following description, numerous specific details are set forth such as specific update utilities, etc. to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known circuits have been shown in block diagram form in order not to obscure the present invention in unnecessary detail. For the most part, details concerning timing considerations and the like have been omitted in as much as such details are not necessary to obtain a complete understanding of the present invention and are within the skills of persons of ordinary skill in the relevant art. 
   The present invention makes use of common cryptographic algorithms. Such cryptographic algorithms may be key-based, where special knowledge of variable information called a “key” is required to decrypt ciphertext. There are two prevalent types of key-based algorithms: “symmetric” (also called secret key or single key algorithms) and “public key” (also called asymmetric algorithms). The security in these algorithms is centered around the keys—not the details of the algorithm itself. With asymmetric public key algorithms, the key used for encryption is different from the key used for decryption. It is generally very difficult to calculate the decryption key from an encryption key. In a typical operation, the “public key” used for encryption is made public via a readily accessible directory, while the corresponding “private key” used for decryption is known only to the receipt of the ciphertext. In an exemplary public key transaction, a sender retrieves the recipient&#39;s public key and uses it to encrypt the message prior to sending it. The recipient then decrypts the message with the corresponding private key. 
   It is also possible to encrypt a message using a private key and decrypt it using a public key. This is sometimes used in digital signatures to authenticate the source of a message, and is a process utilized within the present invention. 
   Referring to  FIG. 3 , an example is shown of a data processing system  313  which may be used for the invention. The system has a central processing unit (CPU)  310 , which is coupled to various other components by system bus  312 . Read only memory (“ROM”)  316  is coupled to the system bus  312  and includes a basic input/output system (“BIOS”) that controls certain basic functions of the data processing system  313 . Random access memory (“RAM”)  313 , I/O adapter  318 , and communications adapter  434  are also coupled to the system bus  312 . I/O adapter  318  may be a small computer system interface (“SCSI”) adapter that communicates with a disk storage device  320 . Communications adapter  333  interconnects bus  312  with an outside network  350  enabling the data processing system to communicate with other such systems. Input/Output devices are also connected to system bus  312  via user interface adapter  322  and display adapter  336 . Keyboard  324  and mouse  326  are interconnected to bus  312  via user interface adapter  322 . Display monitor  338  is connected to system bus  312  by display adapter  336 . In this manner, a user is capable of inputting to the system throughout the keyboard  324  or mouse  326  and receiving output from the system via display  338 . 
   Implementations of the invention include implementations as a computer system programmed to execute the method or methods described herein, and as a computer program product. According to the computer system implementation, sets of instructions for executing the method or methods may be resident in the random access memory  314  of one or more computer systems configured generally as described above. Until required by the computer system, the set of instructions may be stored as a computer program product in another computer memory, for example, in disk drive  320  (which may include a removable memory such as an optical disk or floppy disk for eventual use in the disk drive  320 ). Further, the computer program product can also be stored at another computer and transmitted when desired to the user&#39;s workstation  313  by a network or by external network  350  such as the Internet. One skilled in the art would appreciate that the physical storage of the sets of instructions physically changes the medium upon which it is stored so that the medium carries computer readable information. The change maybe electrical, magnetic, chemical, biological, or some other physical change. While it is convenient to describe the invention in terms of instructions, symbols, characters, or the like, the reader should remember that all of these and similar terms should be associated with the appropriate physical elements. 
   Note that the invention may describe terms such as comparing, validating, selecting, identifying, or other terms that could be associated with a human operator. However, for at least a number of the operations described herein which form part of at least one of the embodiments, no action by a human operator is desirable. The operations described are, in large part, machine operations processing electrical signals to generate other electrical signals. 
   The present invention is described with respect to the update of a BIOS image within a data processing system, such as system  313 . However, the present invention is applicable to the update of any data and/or image within an information handling system. 
   The present invention makes use of the TCPA (Trusted Computing Platform Alliance) Specification where a trusted platform module (TPM)  351  has been installed within system  313 . The TCPA Specification is published at www.trustedpc.org/home/home.htm, which is hereby incorporated by reference herein. However, it should be noted that the present invention may also be implemented using other cryptographic verification methods and processes. 
   Referring to  FIG. 1 , system  313 , either automatically, or as a result of input from a user, will begin a process where the BIOS image is to be updated. Such a BIOS image may reside within ROM  316  or some other memory module within system  313 . The update of the BIOS image may be received over a network  350  or on a diskette. 
   Referring to  FIG. 1 , in step  101 , a BIOS update application will run on system  313  and will request signature verification of a newly received BIOS image from the TPM  351 . This launches the process illustrated in  FIG. 2  wherein step  201 , the TPM receives the verification request from the BIOS update application and performs a signature verification on the update utility and the updated BIOS image. The TPM  351  may utilize a signature verification process that is a standard method that is used in many cryptographic systems. The sender of the BIOS image computes a “hash” of the original work (a hash is a mathematical computation that is performed on the input; the computation is designed such that the probability of being able to recreate the output without the identical input is low). Then the hash is encrypted using the sender&#39;s private key. This encrypted result is called the signature. When the receiver, the TPM  351 , wishes to verify that the image is authentic, the TPM  351  computes the hash of what was received. The TPM  351  then decrypts the sender&#39;s signature by using the sender&#39;s public key and compares it to the newly computed hash. If they are identical, the TPM  351  then determines that the update image is authentic and has not been modified in transit. 
   Returning to  FIG. 1 , in step  102 , the BIOS update application will continually query the TPM  351  for the status of the verification process. In step  103 , if the TPM verification process has not completed, the process will loop back to step  102 . 
   In  FIG. 2 , in step  202 , a determination is made whether the verification process resulted in a successful verification of the BIOS utility and image. If not, the process proceeds to step  204  where the TPM  351  posts that it has completed the verification process and that the process did not result in a successful verification to the BIOS update application. 
   If in step  202  the verification resulted in a successful verification of the BIOS utility and image, the process proceeds to step  203  where the TPM  351  unlocks the flash memory using various methods, such as a general purpose output pin on the TPM  351 . In step  204 , the TPM  351  will post that it has completed a successful verification to the BIOS update application. 
   Returning to step  103 , since the verification process has completed in accordance with step  204 , the process proceeds to step  104  where if the verification was not successful, then an error message is displayed to the user and the process exits in step  105 . If the verification was successful, then the process proceeds to step  106  where the BIOS update application updates the BIOS image, and unlocks the flash memory. Locking the flash memory can be performed by a request to the TPM  351  to perform the locking process. 
   In addition to the GPIOs there may be new commands to prevent the unauthorized use of the secure unlock function. This requires the addition of a new verify signature command that includes usage authorization. When the TPM  351  receives the secure unlock request, it would first compare the authorization provided by the caller against the authorization stored in the TPM  351 . If the compare fails, the command is rejected without unlocking the flash. If successful, the TPM  351  would then proceed to the signature verification step. 
   The TPM  351  may also have a protocol for storing the BIOS public key and the associated authorization data. This would permit BIOS/and/or management agents to set the authorization. POST code must ensure the authorization data and key are loaded prior to booting the operation. Changing the key or authorization data would require knowledge of the current authorization data. 
   Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.