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2.0.1 • Public • Published

Blackcube Aurelia 2 powshield toolkit

This toolkit allows easy setup of Powshield.


Package is available on npm

Then you can install the package:

npm install @blackcube/aurelia2-powshield


Process is simple:

  1. Fetch a new challenge from the API
  2. Solve the challenge to get a solution
  3. Verify the solution with the API
  4. If the solution is correct, you can submit your form
  5. Check the solution serverside to avoid any issue


In order to be mst robust, you should limit the use of a challenge For example, you can limit the use of a challenge to 2 times:

  • First time to allow validation by the JS (frontend)
  • Second time to allow validation by the server (backend)

encrypt and decrypt functions should be symmetric to allow the server to encrypt/decrypt the timestamp and validate the challenge

PseudoCode to generate a challenge

// app constants
key = 'your-secret'

// generate a random string of 12 characters
salt = generateRandomString(12)

// generate a random number between 0 and 50000
// values 0 and 50000 can be tuned to your needs
secretNumber = random_int(0, 50000)

algorithm = 'SHA-256'
// algorithm can be SHA-1, SHA-256, SHA-512

timestamp = time()
cypheredTimestamp = base64_encode(encrypt(timestamp, key))

challenge = hash(algorithm, concat(salt, secretNumber, cypheredTimestamp)
signature = hash_hmac(algorithm, challenge, key);

result = base64_encode(json_encode({
    'algorithm': algorithm,
    'timestamp': cypheredTimestamp,
    'challenge': challenge,
    'salt': salt,
    'signature': $signature,
    'start': 0,
    'max': maxIterations,
// return the result as a base64 encoded JSON object

PseudoCode to verify a solution

// app constants
key = 'your-secret'
timeValidity = 300 // 5 minutes

// received payload
payload = json_decode(base64_decode($payload))

algorithm = payload.algorithm
cypheredTimestamp = base64_decode(payload.timestamp)
challenge = payload.challenge
number = payload.number
salt = payload.salt
signature = payload.signature

checkChallenge = hash(algorithm, concat(salt, secretNumber, cypheredTimestamp)
checkSignature = hash_hmac(algorithm, challenge, key)

timestamp = decrypt(base64_decode(cypheredTimestamp), key)

validityOk = time < timestamp + timeValidity
challengeOk = hash_equals(checkChallenge, challenge)
signatureOk = hash_equals(checkSignature, signature)

verfied = challengeOk and signatureOk;

Registering it in app

import Aurelia, { ConsoleSink, LoggerConfiguration, LogLevel} from 'aurelia';
import { PowshieldConfiguration } from "@blackcube/aurelia2-powshield";
import { MyApp } from './my-app';
        level: LogLevel.trace,
        colorOptions: 'colors',
        sinks: [ConsoleSink]

Additional configuration if needed

You can configure the toolkit by passing a configuration object to the configure method:

import Aurelia, { ConsoleSink, LoggerConfiguration, LogLevel} from 'aurelia';
import { PowshieldConfiguration } from "@blackcube/aurelia2-powshield";
import { MyApp } from './my-app';
        generateChallengeUrl: '/powshield/generate-challenge',
        verifySolutionUrl: '/powshield/verify-solution',
        solutionInputSelector: '#powshieldSolution'
        level: LogLevel.trace,
        colorOptions: 'colors',
        sinks: [ConsoleSink]

Default values are:

  • generateChallengeUrl: '/powshield/generate-challenge',

  • verifySolutionUrl: '/powshield/verify-solution',

  • solutionInputSelector: '#powshieldSolution'

  • generateChallengeUrl URL used to generate a new challenge

  • verifySolutionUrl URL used to verify a solution

  • solutionInputSelector selector used to get the solution input element which will be used to send the solution to the server

Usage in HTML

    <form bc-powshield="#powshieldSolution">

        <input type="hidden" id="powshieldSolution" name="powshieldSolution" />
            <label for="email">EMail</label>
            <input type="email" id="email" name="email" />
            <button type="submit">Submit</button>

Form will be protected by Powshield. When the form is submitted, the toolkit will generate a new challenge, and will add the solution to the hidden input field. The form will be submitted with the solution. The server will be able to verify the solution.




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npm i @blackcube/aurelia2-powshield

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