Open Source

`step-ca` server

Introduction to `step-ca`

step-ca is an online Certificate Authority (CA) for secure, automated X.509 and SSH certificate management. It's the server counterpart to step CLI. It is secured with TLS, and it offers several configurable certificate provisioners, flexible certificate templating, and pluggable database backends to suit a wide variety of contexts and workflows. It employs sane default algorithms and attributes, so you don't have to be a security engineer to use it securely.

Teams use step-ca to:

Generate TLS certificates for private infrastructure using the ACME protocol

Automate TLS certificate renewal

Add Automated Certificate Management Environment (ACME) support to a legacy subordinate CA

Issue short-lived SSH certificates via OAuth OIDC single sign on

Issue customized X.509 and SSH certificates

and much more ...

Don't want to run your own CA?

To get up and running quickly, or as an alternative to running your own step-ca server, consider creating a free hosted smallstep Certificate Manager authority.

Features

X.509 Certificate Authority

step-ca issues X.509 certificates for use with TLS, mutual TLS (mTLS) authentication, document signing, and X.509 authentication more broadly. With step-ca, you can:

Automate certificate issuance and renewal for clients and servers and Kubernetes workloads.

Issue certificates to humans, eg. using Single Sign-on (OpenID Connect) for authentication.

Choose key types (RSA, ECDSA, EdDSA) and lifetimes to suit your needs

Issue short-lived certificates with automated enrollment, renewal, and passive revocation

Operate an online intermediate CA to an existing root CA, eg. to add support for ACME to an existing PKI

Operate a local Registration Authority (RA) on an internal network or inside a Kubernetes cluster, that authorizes certificate requests for an upstream step-ca server.

Deploy a high availability (HA) Certificate Authority using root federation and/or multiple intermediaries

SSH Certificate Authority

step-ca can issue SSH certificates to users and hosts. Delegate SSH authentication to step-ca and set up a clear chain of trust for authorizing access.

Avoid the risk of trust-on-first-use (TOFU) when connecting to SSH hosts

Issue short-lived SSH user certificate via Single Sign-on.

Provisioners

Provisioners are methods of using the CA to get certificates for humans or machines. They offer different modes of authorization for the CA.

For example, you can have your CA issue certificates in exchange for:

ACME challenge responses from any ACMEv2 client

OAuth OIDC single sign-on tokens, eg:

ID tokens from Okta, G Suite, Azure AD, Auth0.

ID tokens from an OAuth OIDC service that you host, like Keycloak or Dex

Cloud instance identity documents, for VMs on AWS, GCP, and Azure

Single-use, short-lived JWK tokens, eg. issued by your CD tool — Puppet, Chef, Ansible, Terraform, etc.

Templates

X.509 Templates let you customize certificate fields, eg:

Add custom Subject Alternative Names (SANs) or non-standard X.509 Object Identifiers (OIDs) to certificates

Restrict certificates by domain name or key size

Issue CA certificates with longer path lengths for multiple intermediaries

step-ca ships with several built-in templates for everyday operations, and you can use Golang's text/template syntax to create new templates.

Cryptographic Protection

For strong protection of your CA signing keys, we've built step-ca integrations for PKCS #11 HSMs, Google Cloud KMS, AWS KMS, and YubiKey PIV, among others.