feat(security): add AES-256-GCM encryption for user tokens

src/lib/server/tokenEncryption.ts

@@ -0,0 +1,72 @@
+import crypto from "crypto";
+import { config } from "./config";
+import { logger } from "./logger";
+
+const ALGORITHM = "aes-256-gcm";
+const IV_LENGTH = 16;
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+const AUTH_TAG_LENGTH = 16;
+const KEY_LENGTH = 32;
+
+/**
+ * Gets the encryption key from config or generates a warning
+ */
+function getEncryptionKey(): Buffer {
+	const key = config.HF_TOKEN_ENCRYPTION_KEY;
+	if (!key) {
+		logger.warn(
+			"HF_TOKEN_ENCRYPTION_KEY not set. Tokens will be stored unencrypted. Set this to a 32-byte hex string for production."
+		);
+		// For development, use a default key (not secure, but allows testing)
+		const defaultKey = crypto.randomBytes(KEY_LENGTH).toString("hex");
+		logger.warn(`Using temporary encryption key: ${defaultKey}`);
+		return Buffer.from(defaultKey.slice(0, KEY_LENGTH * 2), "hex");
+	}
+
+	if (key.length !== KEY_LENGTH * 2) {
+		throw new Error(`HF_TOKEN_ENCRYPTION_KEY must be exactly ${KEY_LENGTH * 2} characters`);
+	}
+
+	return Buffer.from(key, "hex");
+}
+
+/**
+ * Encrypts a token using AES-256-GCM with a random IV
+ */
+export function encryptToken(token: string): string {
+	const key = getEncryptionKey();
+	const iv = crypto.randomBytes(IV_LENGTH);
+	const cipher = crypto.createCipheriv(ALGORITHM, key, iv);
+
+	let encrypted = cipher.update(token, "utf8", "hex");
+	encrypted += cipher.final("hex");
+
+	const authTag = cipher.getAuthTag();
+
+	// Combine IV + authTag + encrypted data
+	return iv.toString("hex") + ":" + authTag.toString("hex") + ":" + encrypted;
+}
+
+/**
+ * Decrypts a token that was encrypted with encryptToken
+ */
+export function decryptToken(encryptedToken: string): string {
+	const key = getEncryptionKey();
+	const parts = encryptedToken.split(":");
+
+	if (parts.length !== 3) {
+		throw new Error("Invalid encrypted token format");
+	}
+
+	const iv = Buffer.from(parts[0], "hex");
+	const authTag = Buffer.from(parts[1], "hex");
+	const encrypted = parts[2];
+
+	const decipher = crypto.createDecipheriv(ALGORITHM, key, iv);
+	decipher.setAuthTag(authTag);
+
+	let decrypted = decipher.update(encrypted, "hex", "utf8");
+	decrypted += decipher.final("utf8");
+
+	return decrypted;
+}