client

client/src/lib/crypto.ts

@@ -0,0 +1,71 @@
+export class Hex {
+	static encode(buffer: ArrayBuffer): string {
+		let s = ''
+		for (const i of new Uint8Array(buffer)) {
+			s += i.toString(16).padStart(2, '0')
+		}
+		return s
+	}
+
+	static decode(s: string): ArrayBuffer {
+		const size = s.length / 2
+		const buffer = new Uint8Array(size)
+		for (let i = 0; i < size; i++) {
+			const idx = i * 2
+			const segment = s.slice(idx, idx + 2)
+			buffer[i] = parseInt(segment, 16)
+		}
+		return buffer
+	}
+}
+
+const ALG = 'AES-GCM'
+
+export function getRandomBytes(size = 16): Uint8Array {
+	return window.crypto.getRandomValues(new Uint8Array(size))
+}
+
+export function getKeyFromString(password: string) {
+	return window.crypto.subtle.importKey(
+		'raw',
+		new TextEncoder().encode(password),
+		'PBKDF2',
+		false,
+		['deriveBits', 'deriveKey']
+	)
+}
+
+export async function getDerivedForKey(key: CryptoKey, salt: ArrayBuffer) {
+	const iterations = 1_000
+	return window.crypto.subtle.deriveKey(
+		{
+			name: 'PBKDF2',
+			salt,
+			iterations,
+			hash: 'SHA-512',
+		},
+		key,
+		{ name: ALG, length: 256 },
+		true,
+		['encrypt', 'decrypt']
+	)
+}
+
+export async function encrypt(plaintext: string, key: CryptoKey) {
+	const salt = getRandomBytes(16)
+	const derived = await getDerivedForKey(key, salt)
+	const iv = getRandomBytes(16)
+	const encrypted = await window.crypto.subtle.encrypt(
+		{ name: ALG, iv },
+		derived,
+		new TextEncoder().encode(plaintext)
+	)
+	return [salt, iv, encrypted].map(Hex.encode).join(':')
+}
+
+export async function decrypt(ciphertext: string, key: CryptoKey) {
+	const [salt, iv, encrypted] = ciphertext.split(':').map(Hex.decode)
+	const derived = await getDerivedForKey(key, salt)
+	const plaintext = await window.crypto.subtle.decrypt({ name: ALG, iv }, derived, encrypted)
+	return new TextDecoder().decode(plaintext)
+}