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# Introduction to TPMs
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Trusted Platform Modules (TPMs) are a large and complex topic, made all
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the more difficult to explain by the intricate relationships between the
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relevant concepts. This is an attempt at a simple explanation -- much
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simpler than reading hundreds of pages of documents, but then too, too
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light on detail to be immediately useful.
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So what is a TPM? Well, it's a cryptographic co-processor with special
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features to enable "root of trust measurement" (RTM), remote attestation
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of system state, unlocking of local resources that are kept encrypted
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(e.g., filesystems), and more. A TPM can do those things, and it can do
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it with rich authentication and authorization policies.
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> The standards development organization that publishes TPM specifications
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> is the [Trusted Computing Group (TCG)](https://trustedcomputinggroup.org).
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Typically a TPM is a hardware module, a chip, though there are firmware,
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virtual, and simulated TPMs as well, all implemented in software.
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To simplify things we'll consider only TPM 2.0.
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Other parts of this [tutorial](README.md) may cover specific concepts in
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much more detail.
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# Goals
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The goal of this introductory material is to help readers new to TPMs to
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understand them well enough to approach the subjects of:
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- [attestation](/Attestation/README.md)
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- [secure boot](/Boot-with-TPM/README.md)
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and to think about the sorts of things that one can do with TPMs in
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general, which include:
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- device on-boarding
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- ascertaining the state of a device (e.g., has it executed only
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trusted code)
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- unlocking of devices using TPM-based authentication and authorization
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policies (e.g., unlocking a laptop on boot multiple factors such as
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biometrics, smartcards, passwords, time of day, even interaction with
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remote services)
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- using a TPM as a source of entropy for a running OS
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> NOTE: At this time this introduction is very much a layman's
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> introduction, and only an introduction. Readers seeking to do
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> software development using TPMs will want to make use of [TCG
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> specifications and other resources](#Other-Resources).
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## Glossary
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> For a glossary, see section 4 of [TCG TPM 2.0 Library part 1:
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> Architecture](https://trustedcomputinggroup.org/wp-content/uploads/TCG_TPM2_r1p59_Part1_Architecture_pub.pdf).
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# Core Concepts
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Some core concepts in the world of TPMs:
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> NOTE: We will not cover all of these here.
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- cryptography
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- hash extension
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- cryptographic object naming
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- platform configuration registers (PCRs)
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- immutability of object public areas
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- key hierarchies
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- key wrapping
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- restricted cryptographic keys
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- limited resources
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- sessions and authorization
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- other object types, mainly non-volatile (NV) indexes
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- attestation
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We'll assume reader familiarity with the basics of cryptography -- the
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basics of cryptographic primitives as interfaces, but not their
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internals. E.g., hash functions, symmetric encryption, asymmetric
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encryption, and digital signatures.
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Authorization is the most important aspect of a TPM, since that's
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ultimately what it exists for: to authorize a system or application to
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perform certain duties when all the desired conditions allow for it.
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TPMs have a very rich set of options for authorization. It's not just
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[policies](#Policies), but also cryptographic object names used with
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restricted keys to allow access only to applications that also have
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other access.
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Where to start? Let's start with hash extension.
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## Hash Extension
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Hash extension is just appending some data to a current digest-sized
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value, hashing that, and then calling the output the new current value:
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```
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v_0 = 0 # size-of-digest-output zero bits
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v_1 = Extend(v_0, e_0)
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= H(v_0 || e_0)
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v_2 = Extend(v_1, e_1)
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= H(v_1 || e_1)
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= H(H(v_0 || e_0) || e_1)
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v_3 = Extend(v_2, e_2)
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= H(v_2 || e_2)
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= H(H(v_1 || e_1) || e_2)
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= H(H(H(v_0 || e_0) || e_1) || e_2)
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..
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v_n = Extend(v_n-1, e_n-1)
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= H(v_n-1 || e_n-1)
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= H(H(v_n-2 || e_n-2) || e_n-1)
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= H(H(...) || e_n-1)
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```
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where `H()` is a cryptographic hash function.
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Each extension value can be arbitrarily large, and the TPM will use the
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traditional `Init`/`Update`/`Final` approach to making digest
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computation online.
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Note that `H(e0 || e1 || e2) != Extend(Extend(Extend(0, e0), e1), e2)`.
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Hash extension makes "message" boundaries strong.
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Hash extension is most of what a PCR is, but hash extension is used in
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other TPM concepts besides PCRs, such as policy naming.
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## Coping with Severe Resource Limits Using Digests and Hash Extension
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Hardware TPMs are extremely limited in memory and non-volatile memory
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capacity. As a result they cannot hold large entities.
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A common theme in TPMs is the use of digests, and hash extension digests
|
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in particular, as a stand-in for large entities that might not fit at
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once on the TPM.
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TPMs use digests as stand-ins for large entities of various types:
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- eventlogs
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- policies
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- auditing
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We'll discuss at least two of those: event logs, and policies.
|
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## Platform Configuration Registers (PCRs)
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A PCR, then, is just a hash extension output. The only operations on
|
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PCRs are: read, extend, and reset. All richness of semantics of PCRs
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come from how they are used:
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- what the governing TCG platform specification says about them
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- what they are extended with and by what code (in what locality)
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- what purposes they are read for
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- attestation
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- authorization
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Note that a PCR value by itself is devoid of meaning. To add meaning
|
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one must have access to the list of discrete values extended into the
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PCR, as well as the order in which they were extended into the PCR. And
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one must know the meaning of each such value.
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### Eventlogs
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Any TPM-using platform has to provide a way to keep a log of PCR hash
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extension values. Such a log is known as the "eventlog".
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The TPM itself cannot hold this log -- the TPM is too
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resource-constrained.
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## Root of Trust Measurements (RTM)
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When a computer and its TPM start up, most PCRs are set to all-zeros,
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and then the computer's boot firmware performs a core root of trust
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measurement (CRTM) to "measure" (i.e., hash) the the next boot stage and
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extend it into an agreed-upon PCR. The entire boot process should,
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ideally, perform RTMs. At the end of the boot process some set of PCRs
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should reflect the totality of the code path taken to complete booting.
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Some PCRs are used to measure the BIOS, others to measure option ROMs,
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and others to measure the operating system. Each platform has a
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specification for which PCRs are used or reserved for what purposes. In
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principle one could measure the entirety of an operating system and all
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the code that is installed on the system.
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RTM can be used to ensure that only known-trusted code is executed, and
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that important resources are not unlocked unless the state of the system
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when they are needed is "has only executed trusted code to get here".
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Note that some PCRs are left to be used by "applications".
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Some terms:
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- core RTM (CRTM) -- initial measurements performed upon power-on
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- static RTM (SRTM) -- subsequent-to-CRTM measurements of next boot
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stages
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- dynamic RTM (DRTM) -- measurements involved in rebooting
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Resource unlocking can be done by creating objects tied to a set of PCRs
|
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such that they must each have specific values for the TPM to be willing
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to unlock (unseal) the object.
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### The PCR Extension Eventlog
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On the "PC platform" (which includes x64 servers) the BIOS keeps a log
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of all the PCR extensions it has performed. The OS should keep its own
|
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log of extensions it performs of PCRs reserved to the OS. Each
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application has to keep a log of the extensions of the PCRs allocated to
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it. Again, the TPM itself cannot do this.
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The eventlog documents how each PCR evolved to their current state,
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whatever it might be. Since PCR extension values are typically digests,
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the eventlog is very dry, but it can still be used to evaluate whether
|
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the current PCR values represent a trusted state. For example, one
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might have a database of known-good and known-bad firmware/ROM digests,
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then one can check that only known-good ones appear in the eventlog and
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that reproducing the hash extensions described by the eventlog produces
|
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the same PCR values as one can read, and if so it follows that the
|
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system has only executed trusted code to arrive at the state identified
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by the PCRs.
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Note though that PCRs and RTM are not enough on their own to keep a
|
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system from executing untrusted code. A system can be configured to
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allow execution of arbitrary code at some point (e.g., download and
|
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execute) and to not extend PCRs accordingly, in which case the execution
|
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of untrusted code will not be reflected in any RTM.
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## Tickets
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> Tickets are yet another device for coping with TPMs having limited
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> resources. Interaction with TPMs is via request/response
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> commands, and tickets are largely about making TPMs stateless between
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> related commands.
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To avoid having to re-perform various operations -or remember having
|
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performed them- between command invocations, a TPM can produce a
|
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"ticket" that consists of an HMAC over a TPM-generated assertion, keyed
|
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by a key known only to the TPM, and return it to the caller who can then
|
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present it in a subsequent command related to the first.
|
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|
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|
For example, when signing data the TPM will first digest the data to
|
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|
sign over several commands and generate a ticket saying it did produce
|
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|
that digest, then later it can sign the digest after validating the
|
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|
ticket that it produced.
|
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|
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|
Another example is a policy ticket, which allows one to avoid having to
|
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re-authenticate (e.g., with smartcard, biometrics, passwords) on every
|
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command for small window of time.
|
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|
> When would a user be authenticated? Well, typically at boot time, or
|
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|
> maybe at wake from sleep/hibernate time. A laptop could be configured
|
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|
> to require a user to authenticate with biometrics and possibly a
|
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> password or a smartcard. Note that such policies are not required by
|
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> the specifications, but rather something that one can choose to use.
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> There are five types of tickets. We won't cover them here. Readers
|
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> who end up needing to know about them can look at section 11.4.6.3 of
|
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> `TCG TPM 2.0 Library, part 1: Architecture`.
|
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|
|
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|
## Cryptographic Object Naming
|
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|
|
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|
TPMs support a variety of types of objects. Objects generally have
|
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|
pointer-like "handles" that they are often used in the TPM APIs. But
|
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|
more importantly, objects have cryptographically-secure names that are
|
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|
used in many cases.
|
||||||
|
|
||||||
|
The cryptographically-secure name of an object is the hash of the
|
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|
object's "public area".
|
||||||
|
|
||||||
|
The public area of, say, an asymmetric key is a data structure that
|
||||||
|
includes the public key (corresponding to the private key), and various
|
||||||
|
attributes of the key (e.g., its algorithm, but also whether it is bound
|
||||||
|
to the TPM where it resides, or to its key hierarchy), unseal policy,
|
||||||
|
and access policy.
|
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|
|
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|
This concept is extremely important. Because object names are the
|
||||||
|
outputs of cryptographically strong digest (hash) functions, they are
|
||||||
|
resistant to collision attacks, first pre-image attacks, and second
|
||||||
|
pre-image attacks -- as strong as the hash algorithm used anyways.
|
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|
Which means that object names cannot be forged easily, which means that
|
||||||
|
they can be used in context where a peer needs certain guarantees, or
|
||||||
|
to defeat active attacks.
|
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|
|
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|
### Immutability of Object Public Areas
|
||||||
|
|
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|
Because the name of an object is a digest of its public area, the public
|
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|
area cannot be changed after creating it. One can delete and then
|
||||||
|
recreate an object in order to "change" its public area, but this
|
||||||
|
necessarily yields a new name.
|
||||||
|
|
||||||
|
### Cryptographic Object Naming as a Binding
|
||||||
|
|
||||||
|
> This section comes too soon, since it relates to attestation and
|
||||||
|
> restricted keys. Still, it may be useful to illustrate cryptographic
|
||||||
|
> object naming with one particularly important use of it.
|
||||||
|
|
||||||
|
A pair of functions, `TPM2_MakeCredential()` and
|
||||||
|
`TPM2_ActivateCredential()`, illustrate the use of cryptographic object
|
||||||
|
naming as a binding or a sort of authorization function.
|
||||||
|
|
||||||
|
`TPM2_MakeCredential()` can be used to encrypt a datum (a "credential")
|
||||||
|
to a target TPM such that the target will _only be willing to decrypt
|
||||||
|
it_ if *and only if* the application calling `TPM2_ActivateCredential()`
|
||||||
|
to decrypt that credential has access to some key named by the sender,
|
||||||
|
and that name is a cryptographic name that the sender can and must
|
||||||
|
compute for itself.
|
||||||
|
|
||||||
|
The semantics of these two functions can be used to defeat a
|
||||||
|
cut-and-paste attack in attestation protocols.
|
||||||
|
|
||||||
|
## Key Hierarchies
|
||||||
|
|
||||||
|
TPMs have multiple key hierarchies, each with zero, one or more primary
|
||||||
|
keys, each with zero, one, or more children keys:
|
||||||
|
|
||||||
|
```
|
||||||
|
seed
|
||||||
|
|
|
||||||
|
|
|
||||||
|
v
|
||||||
|
primary key (asymmetric encryption)
|
||||||
|
|
|
||||||
|
|
|
||||||
|
v
|
||||||
|
secondary keys (of any kind)
|
||||||
|
|
|
||||||
|
|
|
||||||
|
v
|
||||||
|
...
|
||||||
|
```
|
||||||
|
|
||||||
|
Note that every key has a parent or is a primary key.
|
||||||
|
|
||||||
|
There are four built-in hierarchies:
|
||||||
|
|
||||||
|
- platform hierarchy
|
||||||
|
- endorsement hierarchy
|
||||||
|
- storage hierarchy
|
||||||
|
- null hierarchy
|
||||||
|
|
||||||
|
of which only the endorsement and storage hierarchies will be of
|
||||||
|
interest to most readers.
|
||||||
|
|
||||||
|
The endorsement hierarchy is used to authenticate (when needed) that a
|
||||||
|
TPM is a legitimate TPM. The primary endorsement key is known as the EK
|
||||||
|
(endorsement key). Hardware TPMs come with a certificate for the EK
|
||||||
|
issued by the TPM's manufacturer. This EK certificate ("EKcert") can be
|
||||||
|
used to authenticate the TPM's legitimacy. The EK's public key
|
||||||
|
("EKpub") can be used to uniquely identify a TPM, and possibly link to
|
||||||
|
the platform's, and even the platform's user(s)' identities.
|
||||||
|
|
||||||
|
The `TPM2_CreatePrimary()` and `TPM2_CreateLoaded()` commands create key
|
||||||
|
objects deterministically from the hierarchy's seed and the "template"
|
||||||
|
used to create the key (which includes a "unique" area that provides
|
||||||
|
"entropy" to the key derivation function).
|
||||||
|
|
||||||
|
## Key Wrapping and Resource Management
|
||||||
|
|
||||||
|
Key wrapping is encrypting a secret or private key (key encryotion key,
|
||||||
|
or KEK) such that a specific entity may recover the plain key.
|
||||||
|
|
||||||
|
A decrypt-only asymmetric private key can be used to encrypt secrets to
|
||||||
|
the TPM on which that private key resides.
|
||||||
|
|
||||||
|
As well as wrapping secrets by encryption to public keys, TPMs also use
|
||||||
|
wrapping in a symmetric key known only to the TPM for the purpose of
|
||||||
|
saving keys off the TPM.
|
||||||
|
|
||||||
|
This is used for resource management: since hardware TPMs have very
|
||||||
|
limited resources, objects need to created or loaded, used, then saved
|
||||||
|
off-TPM to make room for other objects to be loaded (unless they are not
|
||||||
|
to be used again, then saving them is pointless). Only a TPM that saved
|
||||||
|
an object can load it again, but some objects can be exported to other
|
||||||
|
TPMs by encrypting them to their destination TPMs' EKpubs.
|
||||||
|
|
||||||
|
With a resource manager and access broker, a TPM can appear to have
|
||||||
|
infinite resources.
|
||||||
|
|
||||||
|
### Controlling Exportability of Keys
|
||||||
|
|
||||||
|
A key that is `fixedTPM` cannot leave the TPM in cleartext. It can be
|
||||||
|
saved off the TPM it resides in, but only that TPM can load it again.
|
||||||
|
|
||||||
|
A key that is `fixedParent` cannot be moved from one part of a key
|
||||||
|
hierarchy to another -- it cannot be "re-parented". Though if its
|
||||||
|
parent is neither `fixedParent` nor `fixedTPM` then the parent and its
|
||||||
|
descendants can be moved as a group to some other TPM.
|
||||||
|
|
||||||
|
> Key hierarchies are an important TPM topic that we're not really
|
||||||
|
> addresing in this intro.
|
||||||
|
|
||||||
|
## Persistence
|
||||||
|
|
||||||
|
In a TPM, key objects are, by default, transient, meaning the TPM will
|
||||||
|
forget them if restarted. Still, they can be saved (encrypted in a
|
||||||
|
secret key only the TPM knows) and later reloaded.
|
||||||
|
|
||||||
|
Transient objects can be made persistent, but because hardware TPMs have
|
||||||
|
very little non-volatile memory, few keys should be made persistent.
|
||||||
|
Instead you can save them (wrapped to a TPM-only KEK) and reload them as
|
||||||
|
needed.
|
||||||
|
|
||||||
|
Because primary keys (for any hierarchy other than the null hierarchy)
|
||||||
|
are derived deterministically from a built-in and protected seed, and
|
||||||
|
from a template, they are persistent even when not moved to NV storage
|
||||||
|
and even when not saved as long as the hierarchy's seed is not reset.
|
||||||
|
|
||||||
|
(Resetting the endorsement hierarchy seed is a very dramatic action, as
|
||||||
|
it changes the EK/EKpub and renders any provisioned EKcert useless.
|
||||||
|
Resetting the storage hierarchy seed is much less dramatic. The NULL
|
||||||
|
hierarchy is reset every time the TPM resets.)
|
||||||
|
|
||||||
|
PCRs always persist, but they get reset on restart.
|
||||||
|
|
||||||
|
NV indexes always persist. (But in disorderly resets/shutdowns a
|
||||||
|
hybrid NV index may not be sync'ed to NV.)
|
||||||
|
|
||||||
|
## Non-Volatile (NV) Indexes
|
||||||
|
|
||||||
|
TPMs also have a special kind of non-volatile object: NV indexes.
|
||||||
|
|
||||||
|
> NOTE: NV indexes are not "objects" in the sense that the TCG's
|
||||||
|
> specifications mean. TCG's definition of "object" is
|
||||||
|
>
|
||||||
|
> > key or data that has a public portion and, optionally, a
|
||||||
|
> > sensitive portion; and which is a member of a hierarchy
|
||||||
|
|
||||||
|
NV indexes come in multiple flavors for various uses:
|
||||||
|
|
||||||
|
- store public data (e.g., an NV index is used to store the EKcert)
|
||||||
|
- emulate PCRs
|
||||||
|
- monotonic counters
|
||||||
|
- fields of write-once bits (bitfields) (for, e.g., revocation)
|
||||||
|
- ...
|
||||||
|
|
||||||
|
NV indexes can be used standalone, and/or in connection with policies,
|
||||||
|
to enrich application TPM semantics.
|
||||||
|
|
||||||
|
## Authentication and Authorization
|
||||||
|
|
||||||
|
TPMs have multiple ways to authenticate users/entities:
|
||||||
|
|
||||||
|
- plain passwords (legacy)
|
||||||
|
- HMAC based on secret keys or passwords
|
||||||
|
- public key signed attestations of identification by biometric
|
||||||
|
authentication devices
|
||||||
|
|
||||||
|
TPMs have two ways to authorize access to various objects:
|
||||||
|
|
||||||
|
- plain passwords (legacy)
|
||||||
|
- HMAC proof of possession of a secret key or password
|
||||||
|
- arbitrarily complex policies that can make reference to:
|
||||||
|
- PCR state
|
||||||
|
- NV index state
|
||||||
|
- time of day
|
||||||
|
- authentication state
|
||||||
|
- etc.
|
||||||
|
|
||||||
|
### Policies
|
||||||
|
|
||||||
|
A policy consists of a sequence of "commands" that each asserts
|
||||||
|
something of interest.
|
||||||
|
|
||||||
|
Policies are particularly interesting because they are cryptographically
|
||||||
|
named using hash extension with the sequence of "commands" that make up
|
||||||
|
a policy. Therefore no matter how complex and large a policy is, it is
|
||||||
|
always "compressed" to a hash digest.
|
||||||
|
|
||||||
|
It is the responsibility of the application that will attempt to use a
|
||||||
|
policy-protected resource to know what the policy's definition is and
|
||||||
|
restate it to the TPM when it goes to make use of that resource. The
|
||||||
|
TPM will evaluate the policy and, at the end, check that its digest
|
||||||
|
matches that of the policy-protected resource. Thus, and because policy
|
||||||
|
digests are small and fixed-sized, they can be arbitrarily more complex
|
||||||
|
than a TPM's limited resources would otherwise allow.
|
||||||
|
|
||||||
|
All the policy commands that are to be evaluated successfully to grant
|
||||||
|
access have to be known to the entity that wants that access. Of
|
||||||
|
course, that entity will have to satisfy -at access time- the conditions
|
||||||
|
expressed by the relevant policy. And that entity has to know the
|
||||||
|
policy because the TPM knows only a digest of it.
|
||||||
|
|
||||||
|
### Policy Construction
|
||||||
|
|
||||||
|
Construction of a policy consists of computing it by hash extending an
|
||||||
|
initial all-zeroes value with the commands that make up the policy.
|
||||||
|
|
||||||
|
### Policy Evaluation
|
||||||
|
|
||||||
|
Evaluation of a policy consists of issuing those same commands to the
|
||||||
|
TPM in a session, with those commands either evaluated immediately or
|
||||||
|
deferred to the time of execution of the to-be-authorized command, but
|
||||||
|
the TPM computes the same hash extension as it goes. Once all policy
|
||||||
|
commands being evaluated have succeeded, the resulting hash extension
|
||||||
|
value is compared to the policy that protects the resource(s) being used
|
||||||
|
by the to-be-authorized command, and if it matches, then the command is
|
||||||
|
allowed, otherwise it is not.
|
||||||
|
|
||||||
|
### Indirect Policies
|
||||||
|
|
||||||
|
Because an object's policy is part of its name, that policy cannot be
|
||||||
|
changed after creation. An indirect policy command allows for a policy
|
||||||
|
to change over time without having to recreate the authorized object.
|
||||||
|
|
||||||
|
### Compound Policies
|
||||||
|
|
||||||
|
Policies consist of a conjunction (logical-AND) of assertions that must
|
||||||
|
be true at evaluation time.
|
||||||
|
|
||||||
|
However, there is a special policy command that allows for alternation
|
||||||
|
(logical-OR). This policy command has a number of alternative policy
|
||||||
|
digests. At evaluation time, one of the alternation digests must match
|
||||||
|
the extension value for the policy commands up to (but excluding) the
|
||||||
|
logical-OR policy command. At evaluation time the caller must have
|
||||||
|
picked one of the alternatives and executed the commands that make it
|
||||||
|
up.
|
||||||
|
|
||||||
|
(Recall that the application has to know the definition of the policy
|
||||||
|
because the TPM knows only the policy's digest.)
|
||||||
|
|
||||||
|
### Rich Policy Semantics
|
||||||
|
|
||||||
|
With all these features, and with all the flexibility allowed by NV
|
||||||
|
indexes, policies can be used to:
|
||||||
|
|
||||||
|
- require that N-of-M users authenticate
|
||||||
|
- require multi-factor authentication (password, biometric, smartcard)
|
||||||
|
- enforce bank vault-like time of day restrictions
|
||||||
|
- check revocation (using NV index bit-field objects)
|
||||||
|
- check system RTM state (PCRs)
|
||||||
|
- distinguish user roles
|
||||||
|
|
||||||
|
## Sessions
|
||||||
|
|
||||||
|
A session is an object (meaning, among other things, that it can be
|
||||||
|
loaded and unloaded as needed) that represents the current policy
|
||||||
|
construction or evaluation hash extension digest (the `policyDigest`),
|
||||||
|
and the objects that have been granted access.
|
||||||
|
|
||||||
|
## Restricted Cryptographic Keys
|
||||||
|
|
||||||
|
Cryptographic keys can either be unrestricted or restricted.
|
||||||
|
|
||||||
|
An unrestricted signing key can be used to sign arbitrary content.
|
||||||
|
|
||||||
|
A restricted signing key can be used to sign only TPM-generated content
|
||||||
|
as part of specific TPM restricted signing commands. Such content
|
||||||
|
always begins with a magic byte sequence. Conversely, the TPM refuses
|
||||||
|
to sign externally generated content that starts with that magic byte
|
||||||
|
sequence.
|
||||||
|
|
||||||
|
A restricted decryption key can only be used to decrypt ciphertexts
|
||||||
|
whose plaintexts have a certain structure. In particular these are used
|
||||||
|
for `TPM2_MakeCredential()`/`TPM2_ActivateCredential()` to allow the
|
||||||
|
TPM-using application to get the plaintext if and only if (IFF) the
|
||||||
|
plaintext cryptographically names an object that the application has
|
||||||
|
access to. This is used to communicate secrets ("credentials") to TPMs.
|
||||||
|
|
||||||
|
There is also a notion of signing keys that can only be used to sign
|
||||||
|
PKIX certificates.
|
||||||
|
|
||||||
|
## Attestation
|
||||||
|
|
||||||
|
Attestation is the process of demonstrating that a system's current
|
||||||
|
state is "trusted", or the truthfulness of some set of assertions.
|
||||||
|
|
||||||
|
Often a system gets something in exchange for attesting to its current
|
||||||
|
state. E.g., keys for unlocking filesystems, or device credentials.
|
||||||
|
|
||||||
|
As you can see in our [tutorial on attestation](/Attestation/README.md),
|
||||||
|
many TPM concepts can be used to great effect:
|
||||||
|
|
||||||
|
- using PCRs to attest to system state
|
||||||
|
- using policies and sealed-to-PCRs objects to attest to authentication
|
||||||
|
events on the system
|
||||||
|
- using restricted keys and cryptographic object naming to authenticate
|
||||||
|
a TPM and bind it to its host
|
||||||
|
- delivering key material to authenticated systems via their TPMs
|
||||||
|
- unlocking resources following successful attestation
|
||||||
|
- authorization of devices onto a network
|
||||||
|
- etc.
|
||||||
|
|
||||||
|
# Other Resources
|
||||||
|
|
||||||
|
[A Practical Guide to TPM 2.0](https://trustedcomputinggroup.org/resource/a-practical-guide-to-tpm-2-0/)
|
||||||
|
is an excellent book that informed much of this tutorial.
|
||||||
|
|
||||||
|
Nokia has a [TPM course](https://github.com/nokia/TPMCourse/tree/master/docs).
|
||||||
|
|
||||||
|
The TCG has a number of members-only tutorials, but it seems that it is
|
||||||
|
possible to be invited to be a non-fee paying member.
|
||||||
|
|
||||||
|
Core TCG TPM specs:
|
||||||
|
|
||||||
|
- [TCG TPM 2.0 Library part 1: Architecture](https://trustedcomputinggroup.org/wp-content/uploads/TCG_TPM2_r1p59_Part1_Architecture_pub.pdf).
|
||||||
|
- [TCG TPM 2.0 Library part 2: Structures](https://trustedcomputinggroup.org/wp-content/uploads/TCG_TPM2_r1p59_Part2_Structures_pub.pdf).
|
||||||
|
- [TCG TPM 2.0 Library part 3: Commands, section 12](https://trustedcomputinggroup.org/wp-content/uploads/TCG_TPM2_r1p59_Part3_Commands_pub.pdf).
|
||||||
|
- [TCG TPM 2.0 Library part 3: Commands Code, section 12](https://trustedcomputinggroup.org/wp-content/uploads/TCG_TPM2_r1p59_Part3_Commands_code_pub.pdf).
|
|
@ -12,10 +12,10 @@ Why GitHub?
|
||||||
|
|
||||||
## Current list of tutorials from [TPM.dev] members
|
## Current list of tutorials from [TPM.dev] members
|
||||||
|
|
||||||
1. Attestation, MakeCredential, ActivateCredential
|
1. [Boot with TPM: Secure vs Measured vs Trusted](Boot-with-TPM/tpmboot.md)
|
||||||
1. Boot with TPM: Secure vs Measured vs Trusted
|
1. [Random Number Generator](Random_Number_Generator/article.md)
|
||||||
1. Random Number Generator
|
1. [Attestation, MakeCredential, ActivateCredential](Attestation/README.md)
|
||||||
1. TPM Introduction (Work in progress - PR #8)
|
1. Introduction to TPM Concepts (Work in progress - PR #8)
|
||||||
|
|
||||||
## List of tutorials that will be transfered to GitHub from [TPM.dev]
|
## List of tutorials that will be transfered to GitHub from [TPM.dev]
|
||||||
|
|
||||||
|
|
Loading…
Reference in a new issue