attezt

attezt is a suite of remote attestation tools.

It provides several components that allows Linux systems to have hardware backed device certificates over the device-attest-01 ACME challenge. This is useful for environments where you want a strong device identity claim for things like x509 certificates used for mTLS setups.

It currently supports smallstep, but also has it's own client implementation to administer device certificates.

atteztd provides an Attestation Certificate Authority. It has an backend inventory API that is able to query a CMDB setup for device inventory and validate devices.

attezt-agent provides a client agent that can serve the TPM certificate over a PKCS11 agent. This agent can be used for things like mTLS over browsers to certify authenticity.

attezt is the program to manage attezt-agent and atteztd deployments. It allows you to check the enrollment of the device, provision certificates. Or administer the attestation certificate authority.

This entire project is a WIP, unsure how feature complete it will be.

Setup with smallstep-ca

attezt needs a small CA chain. Create this with attezt.

λ » attezt ca create

atteztd runs the attestation server. Note that this will sign any certificates that are capable of solving the challenge.

λ » atteztd
2025/12/22 23:13:31 HTTP server listening on :8080

Add the provider into step-ca.

λ ~ » curl -O http://127.0.0.1:8080/root.pem
λ ~ » step ca provisioner add acme-da \
   --type ACME \
   --challenge device-attest-01 \
   --attestation-format tpm \
   --attestation-roots ./root.pem

Issue device certificates with step ca

To use this service with step ca certificate you can run something similar to the below thing.

# Device certificate attested by ak
λ » step ca certificate \
  --attestation-ca-url 'http://127.0.0.1:8080' \
  --attestation-uri 'tpmkms:name=device' \
  --provisioner acme-da $(hostname) device.crt device.crt

You can also renew a device certificate.

λ » step ca renew --force --kms "tpmkms" ./device.crt 'tpmkms:name=device'

Issue with device certificates with attezt-agent

Run the attezt-agent.

λ » sudo attezt-agent
2026/03/15 16:33:55 p11kit-server is running
2026/03/15 16:33:55 export P11_KIT_SERVER_ADDRESS=unix:path=/run/attezt/p11kit.socket
2026/03/15 16:33:55 varlink service is running
2026/03/15 16:33:55 Running at: /run/attezt/dev.attezt.Agent

enroll runs the enrollment procedure and acquires a device certificate.

λ » attezt status
Status:
    Endorsement Key: 2ea8888a4a935bfd418e6a700785655b0d2711abc52e71f1dbeeee03e9650396
  Enrollment status: false

λ » attezt enroll --acme "https://ca.home.arpa/acme/acme-da" --attestation "http://attezt.local:8080"

λ » attezt status
Status:
    Endorsement Key: 2ea8888a4a935bfd418e6a700785655b0d2711abc52e71f1dbeeee03e9650396
  Enrollment status: true
        ACME Server: https://ca.home.arpa/acme/acme-da
 Attestation Server: http://attezt.local:8080

Certificate chain:
X.509v3 TLS Certificate (RSA 2048) [Serial: 1433...6348]
  Subject:     framework
  Issuer:      Linderud Internal CA Intermediate CA
  Provisioner: acme-da
  Valid from:  2026-03-15T15:35:31Z
          to:  2026-03-16T15:35:31Z

X.509v3 Intermediate CA Certificate (ECDSA P-256) [Serial: 3050...3071]
  Subject:     Linderud Internal CA Intermediate CA
  Issuer:      Linderud Internal CA Root CA
  Valid from:  2026-01-03T15:15:45Z
          to:  2036-01-01T15:15:45Z

To make this visible for a browser, you need to add the p11-kit-client.so into the nss database, and make a browser policy for the domain.

λ » modutil -dbdir ~/.pki/nssdb -add attezt -libfile /usr/lib/pkcs11/p11-kit-client.so
λ » export P11_KIT_SERVER_ADDRESS=unix:path=/run/attezt/p11kit.sock

Example policy.

# cat /etc/chromium/policies/managed/mtls.json
{
  "AutoSelectCertificateForUrls": [
    "{\"pattern\":\"https://example.com\",\"filter\":{\"ISSUER\":{\"O\":\"My Internal CA\"}}}"
  ]
}

Start chromium and enjoy your new client certificates.

λ » chromium