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Using the EFI_SHELL_PROTOCOL To Read a File

In this post, I provide the source code for a working UEFI shell application which displays the contents of an ASCII file using functionality provided by the EFI_SHELL_PROTOCOL protocol. The current version of the EFI_SHELL_PROTOCOL is 2.1 and here are the exposed protocol interfaces: typedef struct _EFI_SHELL_PROTOCOL { EFI_SHELL_EXECUTE Execute; EFI_SHELL_GET_ENV GetEnv; EFI_SHELL_SET_ENV SetEnv; EFI_SHELL_GET_ALIAS GetAlias; EFI_SHELL_SET_ALIAS SetAlias; EFI_SHELL_GET_HELP_TEXT GetHelpText; EFI_SHELL_GET_DEVICE_PATH_FROM_MAP GetDevicePathFromMap; EFI_SHELL_GET_MAP_FROM_DEVICE_PATH GetMapFromDevicePath; EFI_SHELL_GET_DEVICE_PATH_FROM_FILE_PATH GetDevicePathFromFilePath; EFI_SHELL_GET_FILE_PATH_FROM_DEVICE_PATH GetFilePathFromDevicePath; EFI_SHELL_SET_MAP SetMap; EFI_SHELL_GET_CUR_DIR GetCurDir; EFI_SHELL_SET_CUR_DIR SetCurDir; EFI_SHELL_OPEN_FILE_LIST OpenFileList; EFI_SHELL_FREE_FILE_LIST FreeFileList; EFI_SHELL_REMOVE_DUP_IN_FILE_LIST RemoveDupInFileList; EFI_SHELL_BATCH_IS_ACTIVE BatchIsActive; EFI_SHELL_IS_ROOT_SHELL IsRootShell; EFI_SHELL_ENABLE_PAGE_BREAK EnablePageBreak; EFI_SHELL_DISABLE_PAGE_BREAK DisablePageBreak; EFI_SHELL_GET_PAGE_BREAK GetPageBreak; EFI_SHELL_GET_DEVICE_NAME GetDeviceName; EFI_SHELL_GET_FILE_INFO GetFileInfo; EFI_SHELL_SET_FILE_INFO SetFileInfo; EFI_SHELL_OPEN_FILE_BY_NAME OpenFileByName; EFI_SHELL_CLOSE_FILE CloseFile;

UEFI Utility to Read TPM 2.0 PCRs

In a previous post, I discussed how to retrieve Platform Configuration Register (PCR) values from a discrete TPM (Trusted Platform Module) 1.2 chip (dTPM 1.2) and provided source code for a UEFI shell utility to display the digests from the first 16 PCRs. In this post, I discuss a number of key TPM 2.0 features and provide the source code for a UEFI shell utility to display the digests from the first 24 PCRs of a TPM 2.0 implementation. What is driving the move to TPM 2.0? Simple, TPM 1.2 ((ISO/IEC 11889) only supports one hash algorithm, i.e. SHA1, and

RNG Protocol Error in Lenovo ThinkPad Firmware

The UEFI specification defines a Random Number Generator protocol (RNG), which can be used to provide random numbers for use in nonces, key generators, signature schemes and more. This protocol was first introduced in version 2.4 of the specification. A UEFI RNG service that implements this protocol takes an optional input value that identifies an RNG algorithm and provides a RNG value based on the input value and internal state, including the state of its entropy sources. When a Deterministic Random Bit Generator (DRBG) is used on the output of the raw entropy source, its security level must be at

UEFI-based Windows 10 Platform - Failure to Boot Due to Missing or Corrupt BCD

I was prompted to write this post as a result of Windows 10 Professional recently attempting to do a silent update while I was waiting in an airport which I unknowingly interrupted when I powered down my UEFI-based laptop prior to boarding the plane. When I later powered on the laptop, it failed to boot and simply displayed the following message: A Boot Configuration Data (BCD) store (there can be more than one) contains boot configuration parameters which control how the operating system is started in Windows 10. First introduced in Windows Vista, these parameters were previously stored in the

Accessing TPM Functionality From UEFI Shell - Part 1

A Trusted Platform Module (TPM) is, traditionally, a hardware device (chip) designed to enable commodity computing platforms (think laptop or personal computer) to achieve greater levels of security than non-TPM equipped platform. There are over 600 million installed TPMs, mostly in high-end laptops made by Lenovo, HP, Dell, Toshiba and others. TPMs are manufactured by many chip producers including Atmel, STMicroelectronics and Toshiba. Via it’s Trusted Execution Technology (TXT), Intel now incorporates TPM functionality in many of its current processors. TPM technology is specified by the Trusted Computing Group (TCG), an industry consortium that includes Intel, Microsoft, AMD, IBM, HP,