Secure boot runtime universal filesystem

An information handling system may include at least one processor; and a computer-readable medium having instructions thereon that are executable by the at least one processor for: prior to initialization of an operating system, executing a pre-boot environment; and within the pre-boot environment, downloading a universal filesystem driver from a first back-end server and loading the universal filesystem driver in the pre-boot environment, wherein the universal filesystem driver is a single pre-boot firmware volume that comprises drivers for a plurality of different filesystems.

TECHNICAL FIELD

The present disclosure relates in general to information handling systems, and more particularly to features of a pre-boot environment of information handling systems.

BACKGROUND

Currently, there are many difficulties in accessing storage devices (e.g., hard drives, solid state drives, etc.) from a pre-boot environment of an information handling system such as a Unified Extensible Firmware Interface (UEFI) Basic Input/Output System (BIOS) pre-boot environment.

It is to be noted that various terms discussed herein are described in the UEFI Specification Version 2.8, released March 2019 (hereinafter, UEFI Specification), which is hereby incorporated by reference in its entirety. One of ordinary skill in the art with the benefit of this disclosure will understand its applicability to other specifications (e.g., prior or successor versions of the UEFI Specification). Further, some embodiments may be applicable to different technologies other than UEFI.

It may be desirable to embed multiple filesystem drivers into a pre-boot environment in order to handle different filesystem types and sizes. (For example, a driver for FAT filesystems may have a limit of 4 GB, etc.)

Further, some pre-boot environments may connect to a remote server and load an image file for booting a cloud-based Service OS (SOS). But there is currently no satisfactory way to authenticate or verify such downloads (e.g., authentication may be possible at the level of an entire disk image, but not at the level of individual files within the image, which may individually implicate points of attack from a security standpoint).

Further, the increasing use of containerized/virtual machine architectures may give rise to additional considerations.

It would thus be desirable to have a universal filesystem driver available in the pre-boot phase that addresses the shortcomings of existing solutions.

It should be noted that the discussion of a technique in the Background section of this disclosure does not constitute an admission of prior-art status. No such admissions are made herein, unless clearly and unambiguously identified as such.

SUMMARY

In accordance with the teachings of the present disclosure, the disadvantages and problems associated with pre-boot environments for information handling systems may be reduced or eliminated.

In accordance with embodiments of the present disclosure, an information handling system may include at least one processor; and a computer-readable medium having instructions thereon that are executable by the at least one processor for: prior to initialization of an operating system, executing a pre-boot environment; and within the pre-boot environment, downloading a universal filesystem driver from a first back-end server and loading the universal filesystem driver in the pre-boot environment, wherein the universal filesystem driver is a single pre-boot firmware volume that comprises drivers for a plurality of different filesystems.

In accordance with these and other embodiments of the present disclosure, a method may include an information handling system executing a pre-boot environment prior to initialization of an operating system; and within the pre-boot environment, the information handling system downloading a universal filesystem driver from a first back-end server and loading the universal filesystem driver in the pre-boot environment, wherein the universal filesystem driver is a single pre-boot firmware volume that comprises drivers for a plurality of different filesystems.

In accordance with these and other embodiments of the present disclosure, an article of manufacture may include a non-transitory, computer-readable medium having computer-executable code thereon that is executable by a processor of an information handling system for: executing a pre-boot environment prior to initialization of an operating system; and within the pre-boot environment, downloading a universal filesystem driver from a first back-end server and loading the universal filesystem driver in the pre-boot environment, wherein the universal filesystem driver is a single pre-boot firmware volume that comprises drivers for a plurality of different filesystems.

DETAILED DESCRIPTION

Preferred embodiments and their advantages are best understood by reference toFIGS. 1 through 6, wherein like numbers are used to indicate like and corresponding parts.

For purposes of this disclosure, when two or more elements are referred to as “coupled” to one another, such term indicates that such two or more elements are in electronic communication or mechanical communication, as applicable, whether connected directly or indirectly, with or without intervening elements.

When two or more elements are referred to as “coupleable” to one another, such term indicates that they are capable of being coupled together.

For the purposes of this disclosure, the term “computer-readable medium” (e.g., transitory or non-transitory computer-readable medium) may include any instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a period of time. Computer-readable media may include, without limitation, storage media such as a direct access storage device (e.g., a hard disk drive or floppy disk), a sequential access storage device (e.g., a tape disk drive), compact disk, CD-ROM, DVD, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and/or flash memory; communications media such as wires, optical fibers, microwaves, radio waves, and other electromagnetic and/or optical carriers; and/or any combination of the foregoing.

FIG. 1illustrates a block diagram of an example information handling system102, in accordance with embodiments of the present disclosure. In some embodiments, information handling system102may comprise a server chassis configured to house a plurality of servers or “blades.” In other embodiments, information handling system102may comprise a personal computer (e.g., a desktop computer, laptop computer, mobile computer, and/or notebook computer). In yet other embodiments, information handling system102may comprise a storage enclosure configured to house a plurality of physical disk drives and/or other computer-readable media for storing data (which may generally be referred to as “physical storage resources”). As shown inFIG. 1, information handling system102may comprise a processor103, a memory104communicatively coupled to processor103, a BIOS105(e.g., a UEFI BIOS) communicatively coupled to processor103, a network interface108communicatively coupled to processor103. In addition to the elements explicitly shown and described, information handling system102may include one or more other information handling resources.

As shown inFIG. 1, memory104may have stored thereon an operating system106. Operating system106may comprise any program of executable instructions (or aggregation of programs of executable instructions) configured to manage and/or control the allocation and usage of hardware resources such as memory, processor time, disk space, and input and output devices, and provide an interface between such hardware resources and application programs hosted by operating system106. In addition, operating system106may include all or a portion of a network stack for network communication via a network interface (e.g., network interface108for communication over a data network). Although operating system106is shown inFIG. 1as stored in memory104, in some embodiments operating system106may be stored in storage media accessible to processor103, and active portions of operating system106may be transferred from such storage media to memory104for execution by processor103.

Network interface108may comprise one or more suitable systems, apparatuses, or devices operable to serve as an interface between information handling system102and one or more other information handling systems via an in-band network. Network interface108may enable information handling system102to communicate using any suitable transmission protocol and/or standard. In these and other embodiments, network interface108may comprise a network interface card, or “NIC.” In these and other embodiments, network interface108may be enabled as a local area network (LAN)-on-motherboard (LOM) card.

As discussed above, it would be desirable to have a universal filesystem driver available in the pre-boot phase of information handling system102. Various embodiments of this disclosure may provide such functionality in different contexts. For example, some embodiments may be applicable in the context of “traditional” systems (e.g., non-virtualized, non-containerized systems). Other embodiments may be applicable in “modern” systems (e.g., virtualized and/or containerized systems), which may use a virtual machine manager (VMM) such as a hypervisor.

For context,FIG. 2illustrates a block diagram of an information handling system configured for a modern use case. Host202is illustrated schematically, including CPU203and RAM204. Various portions of these hardware resources are respectively reserved for VMM use and for use by the host environment itself. In the host environment, various UEFI modules (shown as UEFI driver1, UEFI driver2, DXE (driver execution environment) driver, and UEFI app) may execute. In the VMM context, BIOSConnect or another platform may execute as a VM guest, and additional VM guests may also execute.

Turning now toFIGS. 3A and 3B, a flow chart of an example method for universal filesystems in the context of traditional systems is shown, in accordance with some embodiments. According to some embodiments, the method may begin at step302. As noted above, teachings of the present disclosure may be implemented in a variety of configurations of information handling system102. As such, the preferred initialization point for the method and the order of the steps comprising the method may depend on the implementation chosen.

This embodiment of the present disclosure may include a universal file system (UFS) driver implemented as a UEFI firmware volume (FV). This driver may be downloaded from a secure manufacturer back-end server at step304as part of a pre-boot flow at runtime in some embodiments, which is shown at step302. (Dell's BIOSConnect is one example of such a platform which will be discussed herein. One of ordinary skill in the art with the benefit of this disclosure will understand that in various embodiments, other platforms may be used instead.) This FV may contains drivers for various file systems such as EXT2, EXT3, NTFS, CIFS, NFS, etc.

Each of the files that need to be downloaded as part of the pre-boot UEFI flow may be wrapped with a metadata format that contains: 1) a secure universal file system identifier (SUFI), indicating the filesystem type associated with the file; and 2) a per-segment identifier (SEGI) for verification of segments. A segment may be any desired size chunk of data, such as every 4 GB in some embodiments.

A secure filesystem (SF) driver may also be downloaded from the secure manufacturer back-end server as part of the pre-boot flow at runtime. This driver may have a protocol such as “Dell Secure Filesystem Identifier” in one embodiment, which may be used to validate each downloaded file's SUFI, with the first file being a list of the files that are to be downloaded. See step306-312. If the validation is unsuccessful, the process may be aborted at step316.

Otherwise, once the SF driver validates each file, the file may then be passed to the UFS driver for handling at step314.FIG. 3Billustrates the operation of the UFS component.

UFS may then read the metadata of the file and get the file type to trigger loading of the appropriate filesystem code within the UFS driver at step320. The UFS may validate each segment of the file based on its SEGI at step322. the validation is unsuccessful, the process may be aborted at step326.

Otherwise, once the UFS validates each segment, then at steps328-340, additional processing of the file takes place. In particular, UFS may allow for the filesystem driver that has been selected and loaded to consume the file, either one segment at a time or all at once in various embodiments. (For example, FAT32 has a limit of 4 GB, and so a segment-based approach may be used in that situation.)

As UFS consumes the file, it may format an area (e.g., located on a RAMDISK, a solid state drive, a hard drive, etc.) with the appropriate filesystem format as needed. The SF driver may then move on to the next file requested from the secure back-end server. Once the SF finishes handling all files, then UFS and SF UEFI drivers may be unloaded at step342. If there are additional files, the method may loop back to step308ofFIG. 3Afor additional processing.

AlthoughFIGS. 3A and 3Bdisclose a particular number of steps to be taken with respect to the disclosed method, the method may be executed with greater or fewer steps than those depicted inFIGS. 3A and 3B. In addition, althoughFIGS. 3A and 3Bdisclose a certain order of steps to be taken with respect to the method, the steps may be completed in any suitable order.

The method ofFIGS. 3A and 3Bmay be implemented using information handling system102and/or any other system operable to implement the method. In certain embodiments, the method may be implemented partially or fully in software and/or firmware embodied in computer-readable media.

Turning now toFIGS. 4A and 4B, a flow chart of another example method for universal filesystems in the context of traditional systems is shown, in accordance with some embodiments. According to some embodiments, the method may begin at step402. As noted above, teachings of the present disclosure may be implemented in a variety of configurations of information handling system102. As such, the preferred initialization point for the method and the order of the steps comprising the method may depend on the implementation chosen.

InFIGS. 4A and 4B, a CIFS/NFS file manifest is used instead of a local manifest. For the sake of brevity, only the differences ofFIGS. 4A and 4Brelative toFIGS. 3A and 3Bwill be discussed in detail.

In particular, in the method ofFIGS. 4A and 4B, UFS may load a CIFS/NFS client driver at step406and mount the remote filesystem locally. At step408, the SF may read the file headers of all the files in the file system. The remainder of the method ofFIGS. 4A and 4Bmay be carried out largely in similar fashion to that ofFIGS. 3A and 3B.

AlthoughFIGS. 4A and 4Bdisclose a particular number of steps to be taken with respect to the disclosed method, the method may be executed with greater or fewer steps than those depicted inFIGS. 4A and 4B. In addition, althoughFIGS. 4A and 4Bdisclose a certain order of steps to be taken with respect to the method, the steps may be completed in any suitable order.

The method ofFIGS. 4A and 4Bmay be implemented using information handling system102and/or any other system operable to implement the method. In certain embodiments, the method may be implemented partially or fully in software and/or firmware embodied in computer-readable media.

Turning now toFIGS. 5A and 5B, a flow chart of an example method for universal filesystems in the context of modern systems is shown, in accordance with some embodiments. According to some embodiments, the method may begin at step502. As noted above, teachings of the present disclosure may be implemented in a variety of configurations of information handling system102. As such, the preferred initialization point for the method and the order of the steps comprising the method may depend on the implementation chosen.

A VMM may first be launched on the host system at step502. This VMM will then have access to various system resources. Various VMM drivers may be initialized at step503(e.g., drivers for memory protection and allocation, interrupt management, exception handling, etc.). Various drivers needed to launch a pre-boot platform such as BIOSConnect may be loaded in the VMM context, and then the pre-boot platform may start execution as a VMM guest at step504.

The UFS driver FV mentioned above with respect toFIGS. 3A and 3Bmay be downloaded in the VMM context from the pre-boot platform at runtime at step505. Each of the files that need to be downloaded as part of the pre-boot UEFI flow may be wrapped with a metadata format that contains the SUFI and SEGI mentioned above. The SF driver mentioned above may also be downloaded in the VMM context.

Certain portions ofFIGS. 5A and 5Bare generally similar to corresponding portions ofFIGS. 3A, 3B, 4A, and 4B, and thus for the sake of brevity they are not discussed in detail.

As above, once the SF driver validates each file, the file may then be passed to UFS to handle. UFS may read the metadata of the file and get the file type to trigger loading of the appropriate filesystem code within the UFS driver. The UFS may validate each segment of the file based on its SEGI.

UFS then allows for the filesystem driver that has been selected and loaded to consume the file, either one segment at a time or all at once in various embodiments. (For example, FAT32 has a limit of 4 GB, and so a segment-based approach may be used in that situation.)

As UFS consumes the file, it may format an area (e.g., located on a RAMDISK, a solid state drive, a hard drive, etc.) with the appropriate filesystem format as needed. The SF driver may then move on to the next file requested from the secure back-end server.

While the SF or the UFS performs various file operations, there are still possibilities of malicious behavior or memory-related exceptions in the runtime. In case of any exception during Open( )/Read( )/Write( ) of files, an exception handler may handle the exception in the VMM environment. It can signal an event for saving the VMM execution context in the host context and resume the execution of the VMM after the exceptions have been handled.

Thus, exception handling in the VMM helps in maintaining the flow of UEFI execution without any issues while still handling the exceptions inside the VMM environment.

Once the SF finishes handling all files, then UFS and SF UEFI drivers may be unloaded. Finally, VMM teardown may proceed at step544.

In some embodiments, the UFS driver FV may also be able to interact with any host-based filesystems in the VMM context, so that any exceptions or malicious code may be handled appropriately. Further, in the pre-boot context, a minimal VMM handler in the pre-boot UFS context may ensure the security of the filesystem layer to avoid any malicious code or rootkits.

AlthoughFIGS. 5A and 5Bdisclose a particular number of steps to be taken with respect to the disclosed method, the method may be executed with greater or fewer steps than those depicted inFIGS. 5A and 5B. In addition, althoughFIGS. 5A and 5Bdisclose a certain order of steps to be taken with respect to the method, the steps may be completed in any suitable order.

The method ofFIGS. 5A and 5Bmay be implemented using information handling system102and/or any other system operable to implement the method. In certain embodiments, the method may be implemented partially or fully in software and/or firmware embodied in computer-readable media.

Turning now toFIG. 6, a flow chart of an example method for exception handling is shown, in accordance with some embodiments. According to some embodiments, the method may begin at step602. As noted above, teachings of the present disclosure may be implemented in a variety of configurations of information handling system102. As such, the preferred initialization point for the method and the order of the steps comprising the method may depend on the implementation chosen.

At step602, the UEFI environment is in host execution mode. Starting with the VmmInit( ) function at step604, the VMM execution environment may take over.

As noted above with respect toFIGS. 5A and 5B, the UFS and SF drivers may be executed at step606. At step608, a malicious or erroneous action may be taken by the executing code. For example, the code may attempt to alter memory protection attributes or access outside-of-VMM memory regions.

At step610, the appropriate module may throw an exception. A VMM exception handler library may generate a signal at step612to save the VMM execution context in the host environment. The exception may then be handled at step614, and a VmmResume( ) event may be signaled at step616. Finally, a signal handler in the host environment may re-initialize the VMM execution at step618, and flow may return to step602.

AlthoughFIG. 6discloses a particular number of steps to be taken with respect to the disclosed method, the method may be executed with greater or fewer steps than those depicted inFIG. 6. In addition, althoughFIG. 6discloses a certain order of steps to be taken with respect to the method, the steps may be completed in any suitable order.

The method ofFIG. 6may be implemented using information handling system102and/or any other system operable to implement the method. In certain embodiments, the method may be implemented partially or fully in software and/or firmware embodied in computer-readable media.

Although various possible advantages with respect to embodiments of this disclosure have been described, one of ordinary skill in the art with the benefit of this disclosure will understand that in any particular embodiment, not all of such advantages may be applicable. In any particular embodiment, some, all, or even none of the listed advantages may apply.

Unless otherwise specifically noted, articles depicted in the drawings are not necessarily drawn to scale. However, in some embodiments, articles depicted in the drawings may be to scale.

Further, reciting in the appended claims that a structure is “configured to” or “operable to” perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112(f) for that claim element. Accordingly, none of the claims in this application as filed are intended to be interpreted as having means-plus-function elements. Should Applicant wish to invoke § 112(f) during prosecution, Applicant will recite claim elements using the “means for [performing a function]” construct.