@misskey-dev/node-http-message-signatures

@misskey-dev/node-http-message-signatures

(WIP) Implementation of HTTP Signatures "Draft", RFC 9421, RFC 3230 and RFC 9530 for JavaScript.

It is created for Misskey's ActivityPub implementation.

We initially started working on it with the intention of using it in Node.js, but since we rewrote it to Web Crypto API, it may also work in browsers and edge workers.

Context

HTTP Signatures "Draft" and RFC 9421

RFC 9421 is the standard used for signing HTTP communications, but has been used since draft in the world of ActivityPub server-to-server communications with Misskey, Mastodon, and others. The title "HTTP Signatures" in the draft was changed to "HTTP Message Signatures" in the RFC.

This library allows both the draft and RFC to be used.

RFC 3230 and RFC 9530

RFC 3230 and RFC 9530 are standards used for expressing the digest of the body of an HTTP communication. RFC 9530 was released at the same time as RFC 9421 and obsoletes RFC 3230.

Since ActivityPub also needs digest validation, this library also implements functions to create and validate digests.

Comparison

With http-signature

Previously, we used http-signature (@peertube/http-signature to be exact) to parse and verify (Draft) signatures, and this library replaces those implementations as well.

This is because TritonDataCenter/node-sshpk (formerly joient/node-sshpk), on which http-signature depends, is slower than crypto.

ActivityPub Compatibility

One of the motivations for creating this package is to make Misskey compatible with the Ed25519 signature instead of RSA. In doing so, there is a need to ensure compatibility.

HTTP Message Signatures Implementation Level

As a way of expressing the HTTP Message Signatures support status of software, I propose to express it as an implementation level (string of two-digit numbers).

Newer versions of Misskey have this string in metadata.httpMessageSignaturesImplementationLevel of nodeinfo.

Level	Definition
00	"Draft", RFC 3230, RSA-SHA256 Only
01	"Draft", RFC 3230, Supports multiple public keys and Ed25519
10	RFC 9421, RFC 9530, RSA-SHA256 Only
11	RFC 9421, RFC 9530, Supports multiple public keys and Ed25519

additionalPublicKeys

Misskey added the additionalPublicKeys property to Actor to allow it to have multiple public keys. This is an array of publicKeys.

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    "https://w3id.org/security/v1",
		{
			"Key": "sec:Key",
			"additionalPublicKeys": "misskey:additionalPublicKeys"
		}
  ],
  "id": "https://misskey.io/users/7rkrarq81i",
  "type": "Person",
  "publicKey": {
    "id": "https://misskey.io/users/7rkrarq81i#main-key",
		"type": "Key",
    "owner": "https://misskey.io/users/7rkrarq81i",
    "publicKeyPem": "-----BEGIN PUBLIC KEY-----..."
  },
	"additionalPublicKeys": [{
    "id": "https://misskey.io/users/7rkrarq81i#ed25519-key",
		"type": "Key",
    "owner": "https://misskey.io/users/7rkrarq81i",
    "publicKeyPem": "-----BEGIN PUBLIC KEY-----..."
	}]
}

Usage

Installation

npm install @misskey-dev/node-http-message-signatures

Parse and verify

Parse and verify in fastify web server, implements ActivityPub inbox

import Fastify from 'fastify';
import fastifyRawBody from 'fastify-raw-body';
import {
	verifyDigestHeader,
	parseRequestSignature,
	verifyDraftSignature,
} from '@misskey-dev/node-http-message-signatures';

/**
 * Prepare keyId-publicKeyPem Map
 */
const publicKeyMap = new Map([
	[ 'test', '-----BEGIN PUBLIC KEY...' ],
	...
]);

const fastify = Fastify({
	logger: true,
});
await fastify.register(fastifyRawBody, {
	global: false,
	encoding: null,
	runFirst: true,
});
fastify.post('/inbox', { config: { rawBody: true } }, async (request, reply) => {
	const verifyDigest = await verifyDigestHeader(request.raw, request.rawBody, true);
	if (verifyDigest !== true) {
		reply.code(401);
		return;
	}

	// Parse raw request
	const parsedSignature = parseRequestSignature(request.raw);

	if (parsedSignature && parsedSignature.version === 'draft') {
		// Get public key by keyId
		const publicKeyPem = publicKeyMap.get(parsedSignature.keyId)
		if (!publicKeyPem) {
			reply.code(401);
			return;
		}

		// Verify Signature
		const verifyResult = await verifyDraftSignature(parsed!.value, publicKeyPem);
		if (verifyResult !== true) {
			reply.code(401);
			return;
		}
	}

	reply.code(202);
});

Sign and Post

import {
	genDigestHeaderBothRFC3230AndRFC9530,
	signAsDraftToRequest,
	RequestLike,
} from '@misskey-dev/node-http-message-signatures';

/**
 * Prepare keyId-privateKeyPem Map
 */
const privateKeyMap = new Map([
	['https://sender.example.com/users/0001#ed25519-key', '-----BEGIN PRIVATE KEY...' ],
	...
]);

function targetSupportsRFC9421(url) {
	return true;
}

const includeHeaders = ['(request-target)', 'date', 'host', 'digest'];

export async function send(url: string | URL, body: string, keyId: string) {
	const privateKeyPem = privateKeyMap.get(keyId);
	const u = new URL(url);

	const request: RequestLike = {
		headers: {
			Date: (new Date()).toUTCString(),
			Host: u.host,
		},
		method: 'POST',
		url: u.href,
		body,
	};

	await genDigestHeaderBothRFC3230AndRFC9530(request, body, 'SHA-256');

	if (targetSupportsRFC9421(url)) {
		// TODO
	} else {
		await signAsDraftToRequest(request, { keyId, privateKeyPem }, includeHeaders);

		fetch(u, {
			method: request.method,
			headers: request.headers,
			body,
		});
	}
}