Module solo2::pki

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Solo 2 PKI

Each Solo 2 device has a unique identity, its 128 bit UUID, which is set by NXP in read-only memory. Backing this up is a PKI infrastructure, hosted under https://s2pki.net/, and explained in the following.

At the root is R1, an offline RSA-4096 keypair with a self-signed certificate. It can be obtained via http://i.s2pki.net/r1/.

Trussed certificates

Under R1 sit the intermediate Trussed certificate authorities T1 and T2, which have an Ed255 and P256 keypair, respectively. They are signed by R1 with pathlen = 1. The certificates are available via:

We have two since there is use for both NIST-based (P256) and djb-based (Ed255/X255) certificate chains.

Each Solo 2 device then has three embedded certificates, backed by three keypairs which are generated on-device during production, after the device has been locked. In their X509v3 extension with OID 1.3.6.1.4.1.54053.1.1 they contain the UUID of the device. The certificates are as follows:

  • The Ed255 Trussed device leaf certificate (pathlen = 0), signed by T1, with key usages Certificate Sign and CRL Sign.
  • The X255 Trussed device entity certificate, signed by T1, with key usage Key Agreement
  • the P256 Trussed device leaf certificate (pathlen = 0), signed by T2, with key usages Certificate Sign, CRL Sign, and Key Agreement.

Firmware certificates

The NXP bootloader’s secure boot mechanism has space for four certificates, which may be revoked individually. Correspondingly, we have four entity certificates S1, S2, S3, S4, split designated as active/backup and US/CH development centers. They are available from http://i.s2pki.net/s1/, etc. For firmware signing purposes, they are self-signed; from a PKI perspective we additionally cross-certified them via R1.

FIDO certificates

There is an intermediate CA called F1, which signs the batch certificates for FIDO metadata, which are used during device attestation. These batch certificates must be model specific, we have prepared one each for Solo 2A+ (USB-A + NFC), Solo 2C+ (USB-C + NFC), Solo 2A (USB-A only), Solo 2C (USB-C only).

Structs

Certificate
An owned wrapper for x509_parser::certificate::X509Certificate.
X509Certificate
An X.509 v3 Certificate.

Enums

Authority
Certificate authorities for Solo 2 PKI.

Constants

S2PKI_TLD

Functions

authority_information_access
Canonical URI for Authority Information Access (i.e., where to get the certificate in DER format).
fetch_certificate
Download the certificate of an Authority.