pylego 0.1.42

A python wrapper package for the lego application written in Golang

pylego

pylego is a python extension package to utilize the certificate management application Lego written in Golang in python.

Installation

To install this package, all you need to do is run

pip install .

in your preferred Python venv.

Usage

You can import the lego command and run any function that you can run from the CLI:

from pylego import run_lego_command
test_env = {"NAMECHEAP_API_USER": "user", "NAMECHEAP_API_KEY": "key"}
run_lego_command(
    "[e-mail]",
    "https://localhost/directory",
    b"-----BEGIN CERTIFICATE REQUEST----- ...",
    env=test_env,
    plugin="namecheap",
    private_key="-----BEGIN RSA PRIVATE KEY-----",
)

Argument	Description
email	The provided email will be registered to the ACME server. It may receive some emails notifying the user about certificate expiry.
server	This is the full URL of a server that implements the ACME protocol. While letsencrypt is the most common one, there are other programs that provide this facility like Vault.
csr	This must be a PEM string in bytes that is user generated and valid as according to the ACME server that is being provided above. Many providers have different requirements for what is allowed to be in the fields of the CSR.
plugin	Provider to use: http (HTTP-01), tls (TLS-ALPN-01), or any LEGO DNS provider from here. If no plugin is provided, pylego uses HTTP-01 by default.
env	The env is a dictionary mapping of strings to strings that will be loaded into the environment for LEGO to use. All plugins require some configuration values loaded into the environment. You can find them here
private_key	The provided private key will be used to register the user to the ACME server (not the key that signed the CSR), if not provided pylego will generate a new one

On top of the environment variables that LEGO supports, we have some extra ones that we use to configure the library:

Key	Description
SSL_CERT_FILE	Path to a CA certificate file for pylego to trust. This can be used for trusting the certificate of the ACME server provided.
HTTP01_IFACE	Interface for the HTTP-01 challenge (when no DNS plugin is used or when plugin=http). Any interface by default.
HTTP01_PORT	Port for the HTTP-01 challenge (when no DNS plugin is used or when plugin=http). 80 by default.
TLSALPN01_IFACE	Interface for the TLS-ALPN-01 challenge (when plugin=tls). Any interface by default.
TLSALPN01_PORT	Port for the TLS-ALPN-01 challenge (when plugin=tls). 443 by default.

Error Handling

All errors raised by run_lego_command() are LEGOError exceptions with structured information:

from pylego import run_lego_command, LEGOError

try:
    result = run_lego_command(...)
except LEGOError as e:
    print(f"Error: {e}")              # Includes error code in message
    print(f"Type: {e.type}")          # "acme" (server) or "lego" (client)
    print(f"Code: {e.code}")          # e.g., "invalid_csr", "dns_provider_failed"
    print(f"Detail: {e.detail}")      # Human-readable message

    # ACME-specific fields
    if e.type == "acme":
        print(f"Status: {e.status}")      # HTTP status code
        print(f"Subproblems: {e.subproblems}")  # Validation details per domain

Common error codes: invalid_csr, invalid_private_key, dns_provider_failed, network_error, certificate_obtain_failed. ACME errors include codes like unauthorized, rateLimited, dns.

How does it work?

Golang supports building a shared c library from its CLI build tool. We import and use the LEGO application from GoLang, and provide a stub with C bindings so that the shared C binary we produce exposes a C API for other programs to import and utilize. pylego then uses the ctypes standard library in python to load this binary, and make calls to its methods.

The output binary, lego.so, is installed alongside pylego, and pylego exposes a python function called run_lego_command that will convert the arguments into a JSON message, and send it to LEGO.

On pip install, setuptools attempts to build this binary by running the command

go build -o lego.so -buildmode=c-shared lego.go

If we don't have a .whl that supports your environment, you will need to have Go installed and configured for Python to be able to build this binary.

License

The Lego library used in this project is licensed under the MIT License.

pylego itself is licensed under the Apache License, Version 2.0.