SRP-6a implementation for js

Modular implementation of Secure Remote Password protocol for NodeJS/Browser/React Native environments. This library is inspired by NaCl crypto library and tries to provide same safety and simplicity to the user.

This library is a little bit opioniated about how pefrom authentication process i believe that this process covers all cases and if it doesn't match your project, please, open an issue an i will implement an alternative way or suggest work-around.

Features

• 💪Secure default settings
• 🚀Fast and Safe SRP Engine that conforms to RFC 5054
• 🦺SRP Server and Client that is safe to use without need of a deep knowledge of SRP
• 🧐Customizations for password hashing and proof calculation

Getting Started

Install

yarn add srp6a

Configuration

To use this library you have to configure SRP parameters and provide secure pseudorandom number generator. For simplicity you can pick default parameters and default nodejs random number generator:

import { SRP } from 'srp6a';
import crypto from 'crypto';

const srp = new SRP('default', crypto.randomBytes);

Compute Verifier

For each user you have to generate random salt and store it in the database. Salt is not secret and could be treated the same way as a username.

const username = 'ex3ndr';
const password = '12345678';
const salt = srp.generateSalt();
const verifier = srp.computeVerifier(username, password, salt);

Authentication process

For authentication there are 'SRPClient' and 'SRPServer' classes. Beware: they are can't be reused!. After failed or successful negotiation any function call will result in exception being thrown. If any function return false then 'SRPClient'/'SRPServer' will turn into failed state and could not be used anymore and you have to start new authentication session.

const srpClient = new SRPClient('default', crypto.randomBytes);
const srpServer = new SRPServer('default', crypto.randomBytes);

Set Credentials

First step is setting credentials on client and on server sides:

if (!client.setCredentials(username, password, salt)) {
  throw Error('Unable to set client credentials');
}
if (!server.setCredentials(username, verifier, salt)) {
  throw Error('Unable to set server credentials');
}

Exchange Ephemeral Keys

After setting credentials new ephemeral keys are generated and they became available in publicKey property. This property will throw error if you haven't set credentials.

if (!client.setServerKey(server.publicKey)) {
  throw Error('Unable to set server public key');
}
if (!server.setClientKey(client.publicKey)) {
  throw Error('Unable to set client public key');
}

Validate Proofs

To get an acccess to Session Key you have to validate proofs. Server-side proof is not available untill you successfully validated client one.

if (!server.validateProof(client.proof)) {
    throw Error('Invalid client proof');
}
if (!client.validateProof(server.proof)) {
    throw Error('Invalid server proof');
}

Session Key

After validation you can retreive session key:

const sessionKey = client.sessionKey;

const sessionKey = server.sessionKey;

Advanced Configuration

Presets

There are some built-in presets (please, make a PR for some other well-established parameters). To use a preset simply provide a name to SRP/SRPClient/SRPServer constructors as a first parameter.

• 'default' - Default safe parameters: 2048 bit group from RFC 5054 and SHA-256 for hashing.
• 'homekit' - HomeKit Accessory Protocol parameters: 3072 bit group from RFC 5054 and SHA-512 for hashing.

Manual Configuration

If presets does not work for you, you can specify group and hashing algorithm manually:

{ group: GROUP, hash: HASH }

Where GROUP could be one of:

• RFC 5054 groups:
  • 1024 bit: 'rfc5054_1024'
  • 1536 bit: 'rfc5054_1536'
  • 2048 bit: 'rfc5054_2048'
  • 3072 bit: 'rfc5054_3072'
  • 4096 bit: 'rfc5054_4096'
  • 6144 bit: 'rfc5054_6144'
  • 8192 bit: 'rfc5054_8192'
• Custom Group: { N: string, g: string }. Both numbers are in HEX format with any number of space symbols and formatting. Where HASH could be one of:
• Built-in hashing:
  • SHA-1: 'sha-1'
  • SHA-256: 'sha-256'
  • SHA-512: 'sha-512'
• Custom hashing function of type: (...src: (Buffer)[]) => Buffer

License

MIT