canvas-lti/utils/jwks.js

A Canvas LTI 1.3 integration tool.

const jose = require('node-jose');
const fs = require('fs');
require('dotenv').config();

const PRIVATE_KEY_PATH = 'private.key';
const PUBLIC_KEY_PATH = 'public.key';
const PUBLIC_JWK_PATH = 'public.jwk';

let keystore = jose.JWK.createKeyStore();

async function initializeKeyStore() {
    try {
        // Check if keys already exist
        if (!fs.existsSync(PRIVATE_KEY_PATH) || !fs.existsSync(PUBLIC_KEY_PATH)) {
            // Generate new key pair with properties
            const props = {
                alg: 'RS256',
                use: 'sig',
                kid: 'M9db5159sdPyfFMO-YXDYH_PCmgvcLvwCmumuQqEe7M' // You should generate a unique key ID
            };

            const keyPair = await keystore.generate('RSA', 2048, props);

            // Save private key
            const privatePem = await keyPair.toPEM(true);
            fs.writeFileSync(PRIVATE_KEY_PATH, privatePem);

            // Save public key
            const publicPem = await keyPair.toPEM();
            fs.writeFileSync(PUBLIC_KEY_PATH, publicPem);

            // Save public JWK with 'alg' and 'use' included
            const publicJwk = keyPair.toJSON();
            // Manually add 'alg' and 'use' to the JWK
            publicJwk.alg = props.alg ? props.alg : 'RS256';
            publicJwk.use = props.use ? props.use : 'sig';
            fs.writeFileSync(PUBLIC_JWK_PATH, JSON.stringify(publicJwk, null, 2));
        } else {
            // Load existing private key
            const privatePem = fs.readFileSync(PRIVATE_KEY_PATH, 'utf8');
            await keystore.add(privatePem, 'pem');
        }
    } catch (error) {
        console.error('Error initializing key store:', error);
        throw error;
    }
}

async function getJwks() {
    try {
        if (keystore.all().length === 0) {
            await initializeKeyStore();
        }
        // Map each key to its JSON representation, ensuring 'alg' and 'use' are included
        return {
            keys: keystore.all().map(key => {
                let keyJson = key.toJSON();
                // Explicitly add 'alg' and 'use' fields from the key properties if not present
                if (!keyJson.alg) {
                    keyJson.alg = 'RS256';
                }
                if (!keyJson.use) {
                    keyJson.use = 'sig';
                }
                return keyJson;
            })
        };
    } catch (error) {
        console.error('Error getting JWKS:', error);
        throw error;
    }
}

// Initialize keys when the module loads
initializeKeyStore().catch(console.error);

module.exports = { getJwks };