Mastodon ActivityPub

create-hello-world.json

{
    "@context": "https://www.w3.org/ns/activitystreams",

    "id": "https://my-example.com/create-hello-world",
    "type": "Create",
    "actor": "https://my-example.com/actor",

    "object": {
        "id": "https://my-example.com/hello-world",
        "type": "Note",
        "published": "2018-06-23T17:17:11Z",
        "attributedTo": "https://my-example.com/actor",
        "inReplyTo": "https://mastodon.social/@Gargron/100254678717223630",
        "content": "<p>Hello world</p>",
        "to": "https://www.w3.org/ns/activitystreams#Public"
    }
}

deliver.py

# https://blog.joinmastodon.org/2018/06/how-to-implement-a-basic-activitypub-server/

import base64
import requests

from datetime import datetime
from time import mktime
from wsgiref.handlers import format_date_time
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import rsa, padding


private_key = rsa.generate_private_key(
    public_exponent=65537,
    key_size=2048,
    backend=default_backend()
)
public_key = private_key.public_key()
pem = private_key.private_bytes(
   encoding=serialization.Encoding.PEM,
   format=serialization.PrivateFormat.PKCS8,
   encryption_algorithm=serialization.BestAvailableEncryption(b'1234')
)
with open('private.pem', 'wb') as f:
    f.write(pem)

del private_key, pem


document = open('create-hello-world.json').readlines()
date = format_date_time(mktime(datetime.utcnow().timetuple()))

with open('private.pem', 'rb') as key_file:
    private_key = serialization.load_pem_private_key(
         key_file.read(),
         password='1234',
         backend=default_backend()
     )

signed_string = "(request-target): post /inbox\nhost: mastodon.social\ndate: %s" % date
signature = base64.encodestring(private_key.sign(
    signed_string,
    padding.PSS(
        mgf=padding.MGF1(hashes.SHA256()),
        salt_length=padding.PSS.MAX_LENGTH
    ),
    hashes.SHA256()
))
header = 'keyId="https://my-example.com/actor",headers="(request-target) host date",signature="' + signature.replace('\n', '\\n') + '"'


requests.post('https://mastodon.social/inbox', document, headers={
    'Host': 'mastodon.social',
    'Date': date,
    'Signature': header
})