mirror of
https://github.com/google/go-attestation.git
synced 2024-12-24 07:06:45 +00:00
5df8a8e979
* Add build tag to turn off TPM12 support and avoid tspi dependency * Add notspi build flag related information in README.md
133 lines
4.3 KiB
Markdown
133 lines
4.3 KiB
Markdown
Go-Attestation
|
|
==============
|
|
|
|
[![GoDoc](https://godoc.org/github.com/google/go-attestation/attest?status.svg)](https://godoc.org/github.com/google/go-attestation/attest)
|
|
|
|
Go-Attestation abstracts remote attestation operations across a variety of platforms
|
|
and TPMs, enabling remote validation of machine identity and state. This project
|
|
attempts to provide high level primitives for both client and server logic.
|
|
|
|
Talks on this project:
|
|
|
|
* _"Making Device Identity Trustworthy"_ - Open Source Summit Europe - October 2019 - ([Slides](https://static.sched.com/hosted_files/osseu19/ec/Device%20Identity.pdf))
|
|
* _"Using TPMs to Cryptographically Verify Devices at Scale"_ - Open Source Summit North America - September 2019 - ([Video](https://www.youtube.com/watch?v=EmEymlA5Q5Q) 39min)
|
|
* _"Making Remote Attestation Useful on Linux"_ - Linux Security Summit - September 2019 - ([Video](https://www.youtube.com/watch?v=TKva_h66Ptc) 26min)
|
|
|
|
## Status
|
|
|
|
Go-Attestation is under active development and **is not** ready for production use. Expect
|
|
API changes at any time.
|
|
|
|
Please note that this is not an official Google product.
|
|
|
|
## Installation
|
|
|
|
The go-attestation package is installable using go get: `go get github.com/google/go-attestation/attest`
|
|
|
|
Linux users must install `libtspi` and its headers if they need TPM 1.2 support. This can be installed on debian-based systems using: `sudo apt-get install libtspi-dev`.
|
|
|
|
In case Linux users need only TPM 2.0 support, they can:
|
|
* still install `libtspi`
|
|
* or turn off cgo completely, e.g., `CGO_ENABLED=0 go build`
|
|
* or use `notspi` build tag if cgo is needed for some reasons, e.g., `go build --tags=notspi`
|
|
|
|
## Example: device identity
|
|
|
|
TPMs can be used to identify a device remotely and provision unique per-device
|
|
hardware-bound keys.
|
|
|
|
TPMs are provisioned with a set of Endorsement Keys (EKs) by the manufacturer.
|
|
These optionally include a certificate signed by the manufacturer and act as a
|
|
TPM's identity. For privacy reasons the EK can't be used to sign or encrypt data
|
|
directly, and is instead used to attest to the presence of a signing key, an
|
|
Attestation Key (AK), on the same TPM. (Newer versions of the spec may allow the
|
|
EK to sign directly.)
|
|
|
|
During attestation, a TPM generates an AK and proves to a certificate authority
|
|
that the AK is on the same TPM as a EK. If the certificate authority trusts the
|
|
EK, it can transitively trust the AK, for example by issuing a certificate for
|
|
the AK.
|
|
|
|
To perform attestation, the client generates an AK and sends the EK and AK
|
|
parameters to the server:
|
|
|
|
```go
|
|
// Client generates an AK and sends it to the server
|
|
|
|
config := &attest.OpenConfig{}
|
|
tpm, err := attest.OpenTPM(config)
|
|
if err != nil {
|
|
// handle error
|
|
}
|
|
|
|
eks, err := tpm.EKs()
|
|
if err != nil {
|
|
// handle error
|
|
}
|
|
ek := eks[0]
|
|
|
|
akConfig := &attest.AKConfig{}
|
|
ak, err := tpm.NewAK(akConfig)
|
|
if err != nil {
|
|
// handle error
|
|
}
|
|
attestParams := ak.AttestationParameters()
|
|
|
|
akBytes, err := ak.Marshal()
|
|
if err != nil {
|
|
// handle error
|
|
}
|
|
|
|
if err := ioutil.WriteFile("encrypted_aik.json", akBytes, 0600); err != nil {
|
|
// handle error
|
|
}
|
|
|
|
// send TPM version, EK, and attestParams to the server
|
|
```
|
|
|
|
The server uses the EK and AK parameters to generate a challenge encrypted to
|
|
the EK, returning the challenge to the client. During this phase, the server
|
|
determines if it trusts the EK, either by chaining its certificate to a known
|
|
manufacturer and/or querying an inventory system.
|
|
|
|
```go
|
|
// Server validates EK and/or EK certificate
|
|
|
|
params := attest.ActivationParameters{
|
|
TPMVersion: tpmVersion,
|
|
EK: ek.Public,
|
|
AK: attestParams,
|
|
}
|
|
secret, encryptedCredentials, err := params.Generate()
|
|
if err != nil {
|
|
// handle error
|
|
}
|
|
|
|
// return encrypted credentials to client
|
|
```
|
|
|
|
The client proves possession of the AK by decrypting the challenge and
|
|
returning the same secret to the server.
|
|
|
|
```go
|
|
// Client decrypts the credential
|
|
|
|
akBytes, err := ioutil.ReadFile("encrypted_aik.json")
|
|
if err != nil {
|
|
// handle error
|
|
}
|
|
ak, err := tpm.LoadAK(akBytes)
|
|
if err != nil {
|
|
// handle error
|
|
}
|
|
secret, err := ak.ActivateCredential(tpm, encryptedCredentials)
|
|
if err != nil {
|
|
// handle error
|
|
}
|
|
|
|
// return secret to server
|
|
```
|
|
|
|
At this point, the server records the AK and EK association and allows the client
|
|
to use its AK as a credential (e.g. by issuing it a client certificate).
|