lacme

Modern, async-native Python ACME client library for embedding TLS certificate automation.

What is lacme?

lacme fills the gap between full-featured CLI tools like certbot (not designed for embedding) and low-level ACME protocol libraries that leave orchestration to you. It provides a high-level Client.issue() one-liner alongside full access to every step of the ACME workflow. lacme has just two runtime dependencies -- httpx and cryptography -- and supports Python 3.11+.

Features

• Async-native with sync wrapper -- Client for asyncio, SyncClient for blocking code
• HTTP-01 and DNS-01 challenges -- built-in handlers with pluggable DNS providers (Cloudflare, Route 53, shell hooks)
• Built-in Certificate Authority -- CertificateAuthority for issuing private CA certs, ideal for mTLS
• ACME Responder -- ACMEResponder ASGI app backed by the built-in CA for internal PKI
• Framework integrations -- first-class support for Starlette, FastAPI, and Uvicorn
• CLI tool -- lacme issue, lacme renew, lacme revoke from the command line
• Auto-renewal -- RenewalManager runs in the background and re-issues expiring certificates
• Rate limit tracking -- client-side awareness of Let's Encrypt rate limits with warnings and blocking
• Event system + Prometheus metrics -- EventDispatcher with typed events; optional MetricsCollector
• MockACMEServer for testing -- in-process mock ACME server via httpx.MockTransport

Quick Start

pip install lacme

import asyncio
from lacme import Client
from lacme.challenges.http01 import HTTP01Handler

async def main():
    handler = HTTP01Handler()
    async with Client(
        directory_url="https://acme-v02.api.letsencrypt.org/directory",
        contact="mailto:you@example.com",
        challenge_handler=handler,
    ) as client:
        server = await handler.start_server()  # port 80
        bundle = await client.issue("example.com")
        server.close()
        await server.wait_closed()
    print(bundle.fullchain_pem.decode())

asyncio.run(main())

Private CA / mTLS

from lacme import CertificateAuthority, client_ssl_context, server_ssl_context

ca = CertificateAuthority()
ca.init()

server_cert = ca.issue("myservice.internal")
client_cert = ca.issue("worker-1", client=True)

server_ctx = server_ssl_context(
    cert_pem=server_cert.fullchain_pem,
    key_pem=server_cert.key_pem,
    ca_cert_pem=ca.root_cert_pem,  # require client certs
)
client_ctx = client_ssl_context(
    cert_pem=client_cert.cert_pem,
    key_pem=client_cert.key_pem,
    ca_cert_pem=ca.root_cert_pem,
)

CLI

# Issue a certificate via Let's Encrypt staging
lacme --staging --contact you@example.com issue example.com

# Renew all certificates expiring within 30 days
lacme renew --days 30

# Revoke a certificate
lacme revoke example.com

Documentation

Full documentation is available at turnstonelabs.github.io/lacme.

License

Apache-2.0