S/MIME Example Keys and Certificates

Internet-Draft	S/MIME Example Keys and Certificates	February 2021
Gillmor	Expires 21 August 2021	[Page]

Abstract

The S/MIME development community benefits from sharing samples of signed or encrypted data. This document facilitates such collaboration by defining a small set of X.509v3 certificates and keys for use when generating such samples.¶

2. Background

2.1. Certificate Usage

These X.509 certificates ([RFC5280]) are designed for use with S/MIME protections ([RFC8551]) for e-mail ([RFC5322]).¶

In particular, they should be usable with signed and encrypted messages.¶

2.2. Certificate Expiration

The certificates included in this draft expire in 2052. This should be sufficiently far in the future that they will be useful for a few decades. However, when testing tools in the far future (or when playing with clock skew scenarios), care should be taken to consider the certificate validity window.¶

Due to this lengthy expiration window, these certificates will not be particularly useful to test or evaluate the interaction between certificate expiration and protected messages.¶

2.3. Certificate Revocation

Because these are expected to be used in test suites or examples, and we do not expect there to be online network services in these use cases, we do not expect these certificates to produce any revocation artifacts.¶

As a result, there are no OCSP or CRL indicators in any of the certificates.¶

2.4. Using the CA in Test Suites

To use these end-entity certificates in a piece of software (for example, in a test suite or an interoperability matrix), most tools will need to accept the example CA (Section 3) as a legitimate root authority.¶

Note that some tooling behaves differently for certificates validated by "locally-installed root CAs" than for pre-installed "system-level" root CAs). For example, many common implementations of HPKP ([RFC7469]) only applied the designed protections when dealing with a certificate issued by a pre-installed "system-level" root CA, and were disabled when dealing with a certificate issued by a "locally-installed root CA".¶

To test some tooling specifically, it may be necessary to install the root CA as a "system-level" root CA.¶

2.5. Certificate Chains

In most real-world examples, X.509 certificates are deployed with a chain of more than one X.509 certificate. In particular, there is typically a long-lived root CA that users' software knows about upon installation, and the end-entity certificate is issued by an intermediate CA, which is in turn issued by the root CA.¶

The examples presented in this document use a simple two-link certificate chain, and therefore may be unsuitable for simulating some real-world deployments.¶

In particular, testing the use of a "transvalid" certificate (an end-entity certificate that is supplied without its intermediate certificate) is not possible with the configuration here.¶

2.6. Passwords

Each secret key presented in this draft is unprotected (it has no password).¶

As such, the secret key objects are not suitable for verifying interoperable password protection schemes.¶

However, the PKCS#12 [RFC7292] objects do have simple textual passwords, because tooling for dealing with passwordless PKCS#12 objects is underdeveloped at the time of this draft.¶