E2EE-Appkit-Browser

The browser side of a kit for end-to-end-encrypted (e2ee) apps in Typescript. Server side utilities for authentication are provided by @cyphercider/e2ee-appkit-node.

Installation

npm i -S @cyphercider/e2ee-{appkit-browser,appkit-shared-models}

Overall Design

This libary makes it easy to:

• Generate keys (asymmetric signing, asymmetric encrypting, and symmetric ecrypting)
• Wrap text (including serialized keys) with a password.
• Encrypt, decrypt, and sign content
• Manage key storage in the browser using, powered by Session Keystore
• User signup and login functions, calling backend APIs for obtaining and submitting signing challenges
• Session token (jwt) storage and decoding functionality

Crypto Service Usage

Crypto Service Initialization

import { CryptoService } from './crypto.service'

const cryptoService = new CryptoService()

Asymmetric keypair generation, signing, and verification

// Generate an asymmetric signing keypair
const keypair = await cryptoService.generateKeyPair(KeypairAlgorithm.Signing)

// Sign text with a private key
const signed = await cryptoService.signContent('text to sign', keypair.privateKey)

// Verify signature with a public key.  This function will throw an exception if the signature is invalid
await cryptoService.verifySignature(
  signed.signature,
  signed.protected,
  keypair.publicKey,
  challengeText,
)

Asymmetric keypair generation, encryption, and decryption

// Generate a asymmetric encrypting keypair
const keypair = await cryptoService.generateKeyPair(KeypairAlgorithm.Encrypting)

// Encrypt content with a public key 
const encryptedContent = await cryptoService.encryptWithPublicKey(
  challengeContent,
  userKey.publicKey,
)

// Decrypt content with a private key
const decrypted = await cryptoService.decryptWithPrivateKey(encryptedJwe, userKey.privateKey)

Symmetric key generation, encryption, and decryptiton

// Generate a symmetric key
const key = await cryptoService.generateSymmetricKey()
const initVector = 'random string' // A non-secret random string required in symmetric encryption with AES-GCM 
const secret = 'thesecret'


// Encrypt with symmetric key
const encrypted = await cryptoService.encryptWithSymmetricKey(key, secret, initVector)

// Decrypt with symmetric key
const decrypted = await cryptoService.decryptWithSymmetricKey(key, encrypted, initVector)

Encryption with key derived from a password

// The init vector is a non-secret string and must be the same for wrap / unwrap operations.  
const INIT_VECTOR = 'same for encrypt and decrypt' 

// Encrypt text with a password
const encryptedText = await cryptoService.encryptTextWithPassword(
  'the password',
  'text to encrypt',
  INIT_VECTOR, 
  'salt', // A string used as a salt for PKBDF2.  You could use a user's username for this.
)

// Decrypt text with a password
const decryptedText = await cryptoService.decryptTextWithPassword(
  'the password',
  encryptedText,
  INIT_VECTOR, // This is a random string and must be the same for wrap / unwrap operations.
  'salt', // A string used as a salt for PKBDF2.  You could use a user's username for this.
)

Key storage via session-keystore

The param optionalHoursUntilExpiry is the number of hours until the key expires. The default setting is 24 hours.

// Set user keys
cryptoService.setPublicEncryptionKey(pubEncrypting, optionalHoursUntilExpiry)
cryptoService.setPrivateEncryptionKey(privEncrypting, optionalHoursUntilExpiry)
cryptoService.setPublicSigningKey(pubSigning, optionalHoursUntilExpiry)
cryptoService.setPrivateSigningKey(privSigning, optionalHoursUntilExpiry)

// Get user keys
const pubEncr = cryptoService.getPublicEncryptionKey()
const privEncr = cryptoService.getPrivateEncryptionKey()
const pubSign = cryptoService.getPublicSigningKey()
const privSign = cryptoService.getPrivateSigningKey()

// Clear user keys
cryptoService.clearEncryptionKeys()

// Determine if all keys are present
const allArePresent = cryptoService.allKeysArePresent

User Service Usage

Initialization

import {
  ConfigService,
  CryptoService,
  CryptoVerificationService,
  UserAuthenticationService,
} from '@cyphercider/e2ee-appkit-browser'

const cryptoService = new CryptoService()
/**
 *  ConfigService Initialization
 * 
 *  See additional (optional) params for AuthN routes for ConfigService initialization. Defaults are:
 * 
 *  challengeSubmitRoute = '/authn/submit-challenge',
 *  challengeRetrieveRoute = '/authn/get-challenge',
 *  loginSubmitRoute = '/login',
 *  signupRoute = '/authn/signup',
 *  loginFrontendRoute = '/login',
 */
const config = new ConfigService('http://your-backend-base-url') 
const verificationService = new CryptoVerificationService(cryptoService)
const userAuthService = new UserAuthenticationService(
  config,
  cryptoService,
  verificationService,
)

Log in and log out

// Log in with a given username and password
await userAuthService.login(username, password)

// Log out. Clears session token and all user keys from the browser.
await userAuthService.logout()

Get current session information

// Get current user.  Returns the decoded JWT contents following the most recent user login.  Contains at least the attribute `sub: string`
userAuthService.currentUser

// Get session token.  Returns token in local storage `session_token`.
const token = userAuthService.getSessionToken()

// Get session token payload.  Gets token from storage, decodes, and returns.
const payload = userAuthService.getSessionTokenPayload()

// A boolean of whether the user is logged in.  Returns true if session token is in local storage and all keys are present in `session_keystore`.
const isLoggedIn = userAuthService.isLoggedIn

Signup user

// Optional extra attributes you want to store about this user at signup time that will get passed in the payload to the login endpoint.
const extraAttributes = {
  attributeIWantInUserDetail: 'attribute value'
  ...
}

/**
 * Will attempt to create a user on the server and log in.  If successful, it will will return an object containing user keys and the user session token.  
 * 
 * The signup process will set the session token as well as `currentUser` if successful.
 * 
 * @username - Username for the user.  Will be used along with password to wrap the user's keys.
 * @password - Password for the user.  Will be used along with username to wrap the user's keys.
 * @extraAttributes - Optional extra attributes that will be included in the generated token
 * @signingKeypair - Optional signing keypair. Useful if you need to use a known keypair at the time of signup.
 * @encryptingKeypair - Optional signing keypair. Useful if you need to use a known keypair at the time of signup.
 * 
 */
await userAuthService.signupUser(username, password, extraAttributes?, encryptingKeypair?, signingKeypair?)
const user = userAuthService.currentUser // Get cached / decoded token with user information (including any additional token attributes added by your server logic)

Login user

Similar to signup, but without the extra attributes.

await userAuthService.login(username, password)
const user = userAuthService.currentUser // Get cached / decoded token with user information (including any additional token attributes added by your server logic)

Log out user

userAuthService.logout()

Redirect user to frontend login page

userAuthService.redirectToLogin()

Algorithms used

These are the encryption algorithmns used by this library:

• Asymmetric signing - RS256
• Asymmetric encryption - RSA-OAEP-256
• Symmetric encryption - AES-GCM (length 256)
• Key derivation from password - PBKDF2