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Image of Advanced Programming in the UNIX Environment, Second Edition (Addison-Wesley Professional Computing Series)
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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

Decrypt PROLiNK ADSL Modem Configuration File To Reveal Backdoor

I was recently asked by a friend to examine the settings on a PROLiNK ADSL2 router modem, model PRS1241B, to see if the performance of the modem could be improved as he was having trouble using it for video conferencing. PROLiNK is a brand of Fida International (S) Pte Ltd, a Singapore-based company founded in 1991, that produces a wide range of consumer technology products including a range of ADSL modems and routers. As usual, I wished to make a backup of the current user-configurable settings before modifying any user configurable settings. PROLiNK makes this an easy task to accomplish

UEFI Utility to Read TPM 1.2 PCRs

A Trusted Platform Module (TPM) supports many security functions including a number of special registers called Platform Configuration Registers (PCRs) which can hold data in a shielded location in a manner that prevents tampering or spoofing. A PCR is a 20-byte register. which incidentally is the length of a SHA-1 (Secure Hash Algorithm) hash. Most modern TPMs have 24 or even more PCRs; older ones have 16 PCRs. The TPM 1.2 specification, developed by the Trusted Computing Group (TCG) only requires 16 PCRs. Typically PCRs are used to store measurements. Measurements can be of code, data structures, configuration, information, or

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

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,