import { createCipheriv, createDecipheriv, randomBytes } from 'node:crypto';
const AES_ALGO = 'aes-256-gcm';
const IV_LENGTH = 12; // recommended for GCM
class EncryptionError extends Error {
constructor(
message: string,
public readonly cause?: unknown,
) {
super(message);
this.name = 'EncryptionError';
}
}
let cachedKey: Buffer | null = null;
function getEncryptionKey(): Buffer {
if (cachedKey) {
return cachedKey;
}
const rawKey = process.env.ENCRYPTION_KEY;
if (!rawKey) {
throw new EncryptionError(
'Missing ENCRYPTION_KEY environment variable. Provide a base64 encoded 32-byte key.',
);
}
let decoded: Buffer;
try {
decoded = Buffer.from(rawKey, 'base64');
} catch (error) {
throw new EncryptionError('ENCRYPTION_KEY must be base64 encoded.', error);
}
if (decoded.length !== 32) {
throw new EncryptionError('ENCRYPTION_KEY must decode to exactly 32 bytes for AES-256-GCM.');
}
cachedKey = decoded;
return cachedKey;
}
export function encrypt(plainText: string): string {
try {
const key = getEncryptionKey();
const iv = randomBytes(IV_LENGTH);
const cipher = createCipheriv(AES_ALGO, key, iv, {
authTagLength: 16,
});
const ciphertext = Buffer.concat([cipher.update(plainText, 'utf8'), cipher.final()]);
const tag = cipher.getAuthTag();
const payload = `${iv.toString('base64')}|${ciphertext.toString('base64')}|${tag.toString('base64')}`;
return Buffer.from(payload, 'utf8').toString('base64');
} catch (error) {
if (error instanceof EncryptionError) {
throw error;
}
throw new EncryptionError('Failed to encrypt value.', error);
}
}
export function decrypt(payload: string): string {
try {
const key = getEncryptionKey();
const decoded = Buffer.from(payload, 'base64').toString('utf8');
const parts = decoded.split('|');
if (parts.length !== 3) {
throw new EncryptionError('Invalid ciphertext format. Expected iv|ciphertext|tag structure.');
}
const [ivB64, cipherB64, tagB64] = parts;
const iv = Buffer.from(ivB64, 'base64');
const ciphertext = Buffer.from(cipherB64, 'base64');
const tag = Buffer.from(tagB64, 'base64');
const decipher = createDecipheriv(AES_ALGO, key, iv, {
authTagLength: tag.length,
});
decipher.setAuthTag(tag);
const decrypted = Buffer.concat([decipher.update(ciphertext), decipher.final()]);
return decrypted.toString('utf8');
} catch (error) {
if (error instanceof EncryptionError) {
throw error;
}
throw new EncryptionError(
'Unable to decrypt payload. It may be corrupted or the key is invalid.',
error,
);
}
}
export { EncryptionError };
