aiohttp_signer

This is an aiohttp client middleware, see also Client Middleware Cookbook, to add the digest and http message signatures.

Warning: Not all parts of RFC 9421 HTTP Message Signatures are implemented yet.

• pypi
• bovine-actor, uses aiohttp-signer for Fediverse GET/POST

History

This package was created as part of rewriting bovine. My goal with it being to separate the parts that are HTTP from the parts that are Fediverse and the parts that are cryptography.

Usage

The following illustrates the simplest usage of this package

import aiohttp
from aiohttp_signer import DigestMiddleware, Rfc9421Signer

async def make_post_request(
    target_url: str,
    data: dict,
    key_id: str,
    signer: Callable[[bytes], bytes]
):
    async with aiohttp.ClientSession() as session:
        await session.post(
            target_url,
            json=data,
            middlewares=[
                DigestMiddleware(),
                Rfc9421Signer(key_id=key_id, signer=signer),
            ],
        )

This will cause the message to contain the content-digest, signature-input, and signature headers. Where the used signature parameters are @method, @target-uri, and content-digest.

A sample implementation of signer would be

from cryptography.hazmat.primitives.serialization import load_pem_private_key
from cryptography.hazmat.primitives.asymmetric import ed25519

private_key_pem = b"""
-----BEGIN PRIVATE KEY-----
MC4CAQAwBQYDK2VwBCIEIJ+DYvh6SEqVTm50DFtMDoQikTmiCqirVv9mWG9qfSnF
-----END PRIVATE KEY-----
"""

def signer(x: bytes):
    private_key = load_pem_private_key(private_key_pem, password=None)
    assert isinstance(private_key, ed25519.Ed25519PrivateKey)
    return private_key.sign(x)