identity/asset-api/index.js

import { readFile } from "node:fs/promises";
import { createWriteStream, readFileSync, writeFileSync } from "node:fs";
import { createSign, generateKeyPairSync, randomUUID } from "node:crypto";
import Fastify from "fastify";
import multipart from "@fastify/multipart";
import { join } from "node:path";
import mime from "mime";
import { promisify } from "node:util";
import { pipeline } from "node:stream";

const M2M_ALGORITHM = "RSA-SHA512";
const { private: M2M_PRIVATE_KEY, public: M2M_PUBLIC_KEY } = loadM2MKeys();
if (M2M_PRIVATE_KEY == null || M2M_PUBLIC_KEY == null) {
    console.error("Couldn't load keys");
    process.exit(1);
}

const ASSETS_FOLDER = "./.assets/";
const ASSET_API_LANDING_MESSAGE = "asset-api v1.0.0";

const IDENTITY_API_ENDPOINT = "http://localhost:3000";

const fastify = new Fastify({
    logger: true,
});

fastify.register(multipart);

fastify.get("/", async () => {
    return signString(ASSET_API_LANDING_MESSAGE);
});

fastify.get("/crypto/cert", async () => {
    return M2M_PUBLIC_KEY;
});

fastify.get("/crypto/algo", () => {
    return M2M_ALGORITHM;
});

fastify.put("/asset", {
    async handler(request, reply) {
        let user = await userFromSessionKey(request.query.session_key);
        if (user.assets.length >= user.limits.assetCount) {
            reply.code(403);
            return "Max asset count reached. Contact support or upgrade your plan";
        }

        let file = await request.file();

        let id = randomUUID().toString();
        let extension = mime.getExtension(file.mimetype) || ".bin";
        let full_id = `${id}.${extension}`;

        let url = new URL(IDENTITY_API_ENDPOINT);
        url.pathname = "/m2m/asset";

        await fetch(url, {
            method: "PUT",
            body: signObject({
                session_key: request.query.session_key,
                asset_id: full_id,
            }),
        });

        promisify(pipeline)(file.file, createWriteStream(`.assets/${full_id}`));
    },
    schema: {
        query: {
            type: "object",
            properties: {
                session_key: { type: "string" },
            },
            required: ["session_key"],
        },
    },
});

fastify.get("/asset", {
    async handler(request, reply) {
        let user = await userFromSessionKey(request.query.session_key);

        if ('statusCode' in user) {
            reply.code(500);
            return "Something failed, please try again later"
        }

        if (user.assets.includes(request.query.asset_id)) {
            let path = join(ASSETS_FOLDER, request.query.asset_id);

            reply.type(mime.getType(path));
            reply.send(await readFile(path));
        } else {
            reply.code(401);
            return "Not authorized";
        }
    },
    schema: {
        query: {
            type: "object",
            properties: {
                asset_id: { type: "string" },
                session_key: { type: "string" },
            },
            required: ["asset_id", "session_key"],
        },
    },
});

fastify.listen({ port: 3001 });

function loadM2MKeys() {
    try {
        return {
            private: readFileSync("./.keys/m2m.pem").toString("ascii"),
            public: readFileSync("./.keys/m2m.pub").toString("ascii"),
        };
    } catch {
        console.warn("Generating M2M key pair!");

        let { publicKey, privateKey } = generateKeyPairSync("rsa", {
            modulusLength: 4096,
            publicKeyEncoding: {
                type: "spki",
                format: "pem",
            },
            privateKeyEncoding: {
                type: "pkcs8",
                format: "pem",
            },
        });

        writeFileSync("./.keys/m2m.pem", privateKey);
        writeFileSync("./.keys/m2m.pub", publicKey);

        return loadM2MKeys();
    }
}

function signString(content) {
    let sign = createSign(M2M_ALGORITHM);
    sign.update(content);
    return `-----BEGIN SIGNED MESSAGE-----\n\n${content}\n\n-----BEGIN SIGNATURE-----\n\n${sign.sign(M2M_PRIVATE_KEY, "base64")}\n-----END SIGNATURE-----`;
}

function signObject(content) {
    return signString(JSON.stringify(content));
}

async function userFromSessionKey(session_key) {
    let url = new URL(IDENTITY_API_ENDPOINT);
    url.pathname = "/m2m/account";

    let res1 = await fetch(url, {
        method: "POST",
        body: signObject({
            session_key,
        }),
    });

    return await res1.json();
}