generate-chrome-extension-key.js

// generate_key.js
// No dependencies! Using only Web Crypto API and Deno built-ins.

async function main() {
	console.log('Generating RSA Key Pair...');

	// 1. Generate RSA Key Pair
	const keyPair = await crypto.subtle.generateKey(
		{
			name: 'RSASSA-PKCS1-v1_5',
			modulusLength: 2048,
			publicExponent: new Uint8Array([0x01, 0x00, 0x01]),
			hash: 'SHA-256',
		},
		true,
		['sign', 'verify'],
	);

	// 2. Export Private Key (PKCS#8) -> Save as key.pem
	const privateKeyDer = await crypto.subtle.exportKey('pkcs8', keyPair.privateKey);
	const privateKeyBytes = new Uint8Array(privateKeyDer);
	let privateKeyString = '';
	for (let i = 0; i < privateKeyBytes.length; i++) 
		privateKeyString += String.fromCharCode(privateKeyBytes[i]);
	
	const privateKeyBase64 = btoa(privateKeyString);
	const pemContent = `-----BEGIN PRIVATE KEY-----\n${privateKeyBase64.match(/.{1,64}/g).join('\n')}\n-----END PRIVATE KEY-----\n`;

	await Deno.writeTextFile('key.pem', pemContent);
	console.log('✅ key.pem generated.');

	// 3. Export Public Key (SubjectPublicKeyInfo)
	const publicKeyDer = await crypto.subtle.exportKey('spki', keyPair.publicKey);
	const publicKeyBytes = new Uint8Array(publicKeyDer);
	let publicKeyString = '';
	for (let i = 0; i < publicKeyBytes.length; i++) 
		publicKeyString += String.fromCharCode(publicKeyBytes[i]);
	
	const publicKeyBase64 = btoa(publicKeyString);

	// This Base64 string is what we need for manifest.json "key" field!
	await Deno.writeTextFile('manifest_key.txt', publicKeyBase64);
	console.log('✅ manifest_key.txt generated.');

	// 4. Calculate Extension ID
	// SHA-256 of SubjectPublicKeyInfo
	const hashBuffer = await crypto.subtle.digest('SHA-256', publicKeyDer);
	const hashArray = new Uint8Array(hashBuffer);

	// Take first 16 bytes (128 bits)
	const idBytes = hashArray.subarray(0, 16);

	// Convert to 'a'-'p' mapped string
	let id = '';
	for (const byte of idBytes) {
		// High nibble
		id += String.fromCharCode(((byte >> 4) & 0x0F) + 97); // 0->a, 15->p
		// Low nibble
		id += String.fromCharCode((byte & 0x0F) + 97); // 0->a, 15->p
	}

	await Deno.writeTextFile('extension_id.txt', id);
	console.log(`✅ Extension ID: ${id}`);
}

main();