neopass

Encourage better passwords.

Neopass is a password validation and generation tool kit built on plugins.

• Password generation
• Password validation
• Password strength
• Passphrase support

Under Development

This package is currently under development and the interface is unstable. While the package remains at version 0.x.y, the minor version will be updated when known breaking changes occur.

Contents

• Installation
• Basics
  • Password Generation
  • The Validation Chain
  • The Evaluation Chain
  • Passphrase Detection
• External Generators
  • Memorable Generator
• Built-in Validators
  • ClassesValidator
  • CommonValidator
  • DepthValidator
  • EntropyValidator
  • LengthValidator
  • RunValidator
  • SequenceValidator
  • ShannonValidator
  • TopologyValidator
• Configuring Validators
  • Short Form
  • Long Form
• Custom Validators
• Optional Rules
• Plugins
  • Authoring a Validator Plugin
• Override Configured Chains

Installation

npm install neopass

Basics

Password Generation

Neopass can generate random strings using configured generators. By default, there are three generators available:

random: produces n random characters from a character set of typable characters uppercase, lowercase, digit, and special.

letters-numbers: produces n random characters from a character set of uppercase, lowercase, and digit.

hex: produces n random bytes in hexidecimal form.

import { neopass, INeoConfig } from 'neopass'
 
const config: INeoConfig = {
  useBuiltinGenerators: true, // default
}
 
const neo = neopass(config)
 
const pass1 = neo.generate(12, 'random')
console.log('random:', pass1)
 
const pass2 = neo.generate(12, 'letters-numbers')
console.log('letters-numbers', pass2)
 
const pass3 = neo.generate(12, 'hex')
console.log('hex', pass3)

Output:

random: |6Tc/]>4KY:5
letters-numbers: WIW71lZEuUsN
hex: 9b9ede126e4f2556fe1717dc

Registered Generators

A list of registered generators can be obtained with the following call:

  const generators = neo.generators()
  console.log('generators:', generators)

Output:

generators: [
  { name: 'random', title: 'Random', units: 'char' },
  { name: 'letters-numbers', title: 'Letters & Numbers', units: 'char' },
  { name: 'hex', title: 'Hexidecimal', units: 'byte' }
]

The Validation Chain

The validation chain reports errors from each configured validator.

import { neopass, INeoConfig } from 'neopass'
 
const config: INeoConfig = {
  useBuiltinValidators: true, // default
 
  /**
   * These validators are run when `validate` is called, and
   * reference built-in validators registered automatically.
   *
   * Each validator is called in sequence and any errors produced
   * are returned by the call.
   */
  validators: [
    /**
     * Password must be between 10 and 72 characters.
     */
    'length:min=10,max=72',
    /**
     * Password must contain an uppercase character, a lowercase
     * character, and one of digit or special character.
     */
    'classes:and=ul,or=ds',
  ]
}
 
const neo = neopass(config)
 
// Validate a password.
const errors = neo.validate('spokane')
console.log('errors:', errors)

Output:

errors: [
  {
    name: 'length',
    msg: 'password length should be between 10 and 72 characters, inclusive',
    score: 0.7
  },
  {
    name: 'classes',
    msg: 'missing uppercase character',
    meta: 'u'
  },
  {
    name: 'classes',
    msg: 'missing one of digit, special',
    meta: 'ds'
  }
]

Generator Retries

When generating passwords, it might be important for you to make sure that the generated password will pass your defined validation chain. Depending on how the chain is configured, random strings produced by password generation might occasionally result in a password that fails a validation step. You can specify generator retries to retry generation a number of times to mitigate cases where this may occur.

const neo = neopass({
  validators: ['run:3']
})
 
const pass = neo.generate(10, 'letters-numbers')
console.log(pass) // j47VXGqqq3
// Oops! There are three 'q' together which violates the run validator.
 
// Specify up to five retries to regenerate passwords that fail validation.
const safePass = neo.generate(10, 'letters-numbers', 5)
console.log(safePass) // iUG6r76ecR

If the number of retries is exceeded, generate will throw an error, which would suggest that your validation rules might be too strict, or perhaps the selected generator is not appropriate for your use case.

The Evaluation Chain

The evaluation chain reports a password's strength based on configured evaluators.

import { neopass, INeoConfig } from 'neopass'
 
const config: INeoConfig = {
  useBuiltinValidators: true, // default
 
  /**
   * These are run when `evaluate` is called.
   *
   * Each evaluator object can specify weight and a list of validators.
   *
   * weight: multiplies the strength by the weight for every
   * validation failure in the list of `validators`.
   *
   * validators: a list of validators to run. Validators that return
   * a score have that score applied to the strength in addition to
   * whatever `weight` is specified.
   */
  evaluators: [
    {
      weight: 0.9,
      validators: [
        'length:min=10,max=72',
      ],
    },
    {
      weight: 0.7,
      validators: [
        'classes:and=ul,or=ds',
      ],
    },
  ]
}
 
const neo = neopass(config)
 
const result = neo.evaluate('Spokane')
console.log('result:', result)

Output:

result: {
  strength: 0.44099999999999995,
  warnings: [
    {
      name: 'length',
      msg: 'password length should be between 10 and 72 characters, inclusive',
      score: 0.7
    },
    {
      name: 'classes',
      msg: 'missing one of digit, special',
      meta: 'ds'
    }
  ]
}

Assessing password strength is subjective and can be rather arbitrary. A good philosopy is to define evaluators that represent a near-ideal or practically-perfect password, so that there is a good range between low-strength and high-strength passwords, and you're not representing an overly-optimistic strength assessment.

Here's an example that makes some attempt at a reasonable strength evaluation:

const neo = neopass({
  // ...
  evaluators: [
    {
      /**
       * This evaluator doesn't necessarily need 'weight' because
       * these validators return a score, which is used to calculate
       * strength. If weight is present, it's applied to the score.
       */
      validators: [
        'length:min=20,max=72',
        'entropy:64',
      ],
    },
    {
      /**
       * These validators don't return a score, so each
       * error multiplies the strength by 0.75.
       */
      weight: 0.75,
      validators: [
        'run:3',
        'sequence:4',
        'classes:and=ul,or=ds',
        'topology:standard=true',
      ],
    },
  ],
})

Bad:

neo.evaluate('Denver2016')

{ strength: 0.348878690061731,
  warnings:
   [ { name: 'length',
       msg: 'password length should be between 20 and 72 characters, inclusive',
       score: 0.5,
       meta: 'min' },
     { name: 'entropy',
       msg: 'password is either too short or not complex enough',
       score: 0.9303431734979493 },
     { name: 'topology',
       msg: 'password matches vulnerable pattern topology' } ] }

Still bad:

neo.evaluate('Denver2016!')

{ strength: 0.41250000000000003,
  warnings:
   [ { name: 'length',
       msg: 'password length should be between 20 and 72 characters, inclusive',
       score: 0.55,
       meta: 'min' },
     { name: 'topology',
       msg: 'password matches vulnerable pattern topology' } ] }

Not great:

neo.evaluate('D3nv3r2016!')

{ strength: 0.55,
  warnings:
   [ { name: 'length',
       msg: 'password length should be between 20 and 72 characters, inclusive',
       score: 0.55,
       meta: 'min' } ] }

Good:

neo.evaluate('D3nv3r2016!and17$')

{ strength: 0.85,
  warnings:
   [ { name: 'length',
       msg: 'password length should be between 20 and 72 characters, inclusive',
       score: 0.85,
       meta: 'min' } ] }

Great?:

neo.evaluate('correct Horse battery staple')

{ strength: 1, warnings: [] }

Strength assessment is a bit of both art and science, and it won't assure a great password. However it is a good tool to help users to create better passwords in general.

Passphrase Detection

Passphrases are long passwords typically comprised of multiple words. These are considered to be more secure than shorter, mixed-class passwords. If configured, neopass will detect a passphrase and bypass additional validation in the validation chain.

import { neopass, INeoConfig } from 'neopass'
 
const config: INeoConfig = {
  validators: [
    // Passwords with 20 or more characters will be treated as passphrases.
    'passphrase:20',
    'length:min=10,max=72',
    'classes:and=ul,or=ds',
  ]
}
 
const neo = neopass(config)
 
/**
 * The below password would normally fail the 'classes' validator
 * as configured because there is no digit/special character.
 */
const errors = neo.validate('Lemme get this smooth')
console.log('errors:', errors)

Output:

errors: []

External Generators

Memorable Generator

The Memorable Generator generates an easy-to-remember password:

npm install @neopass/memorable-generator @neopass/words-by-length-view

Optional:

npm install @neopass/wordlist

const { neopass } = require('neopass')
const { WordsByLengthView } = require('@neopass/words-by-length-view')
const { MemorableGenerator } = require('@neopass/memorable-generator')
const { wordListSync } = require('@neopass/wordlist')
 
/**
 * We're using @neopass/wordlist to feed the view, but any
 * word list of sufficient size will do.
 */
const view = new WordsByLengthView(wordListSync())
 
const neo = neopass({
  plugins: [new MemorableGenerator(view)]
})
 
const pass = neo.generate(16, 'memorable')
console.log('password:', pass)

Output:

password: smugly$Luminous7

See Memorable Generator on npm.

Built-in Validators

ClassesValidator

Validates a password based on its character classes, mainly u (uppercase), l (lowercase), d (digit), and s (special character).

const { neopass } = require('neopass')
 
const config = {
  /**
   * Configure the classes validator to require an uppercase
   * and a lowercase character, plus one of either a digit
   * or a special character (!@#$%^&, etc).
   */
  validators: ['classes:and=ul,or=ds']
}
 
const neo = neopass(config)
 
const errors = neo.validate('abcdefg')
console.log(errors)

Output:

[ { name: 'classes',
    msg: 'missing uppercase character',
    meta: 'u' },
  { name: 'classes',
    msg: 'missing one of digit, special',
    meta: 'ds' } ]

CommonValidator

Validates a password based on whether it's included in a common passwords list.

Note that CommonValidator requires a password list to be given in its options, so it is not short-form configurable.

const { neopass } = require('neopass')
 
const config = {
  /**
   * Configure the common validator with a list of common passwords.
   */
  validators: [
    {
      plugin: 'common',
      options: {
        list: [
          '0123456789',
          'password',
          'superman',
        ]
      }
    }
  ]
}
 
const neo = neopass(config)
 
const errors = neo.validate('superman')
console.log(errors)

Output:

[ { name: 'common',
    msg: 'password found in a common vulnerable password list' } ]

DepthValidator

Validates a password based on its character depth, derived from its classes. For example, a password Simple32 has the classes u, l, and d, which means its depth is u=26 + l=26 + d=10 = 62.

const { neopass } = require('neopass')
 
const config = {
  /**
   * Configure the depth validator to require a class depth of 62.
   * This equates to a minimum of upper, lower, and digit characters.
   */
  validators: ['depth:62']
}
 
const neo = neopass(config)
 
const errors = neo.validate('shadow')
console.log(errors)

Output:

[ { name: 'depth',
    msg: 'password needs more class complexity (uppercase, lowercase, digit, special)',
    score: 0.41935483870967744 } ]

EntropyValidator

Validates a password based on its class entropy, derived from its character depth. The entropy is calculated as Math.log2(depth) * length, resulting in a number of bits for the entire password string. The class entropy differs from shannon entropy in that the bits per symbol is assumed based on which character classes are represented in the password. This validator is similar to the DepthValidator in that its value is based on which classes are present in the password, but adds the effect of having awareness of password length. In other words, a password may have several character classes represented, yet still be too short to pass validation.

const { neopass } = require('neopass')
 
const config = {
  /**
   * Require 64 bits of character entropy for the password.
   */
  validators: ['entropy:64']
}
 
const neo = neopass(config)
 
const errors = neo.validate('Shadow@26') // ulds
console.log(errors)

Output:

[ { name: 'entropy',
    msg: 'password is either too short or not complex enough',
    score: 0.9238859449215395 } ]

LengthValidator

Validates a password based on its length.

Configuration:

const { neopass } = require('neopass')
 
const config = {
  /**
   * Password length must fall within [min, max].
   */
  validators: ['length:min=10,max=72']
}
 
const neo = neopass(config)
const errors = neo.validate('shorty')
console.log(errors)

Output:

[ { name: 'length',
    msg: 'password length should be between 10 and 72 characters, inclusive',
    score: 0.6,
    meta: 'min' } ]

RunValidator

Validates whether a password has runs of a single character, such as in pAAAsword.

const { neopass } = require('neopass')
 
const config = {
  /**
   * Fail if password contains three or more of the same character together.
   */
  validators: ['run:3']
}
 
const neo = neopass(config)
 
const errors = neo.validate('pAAAsword')
console.log(errors)

Output:

[ { name: 'run',
    msg: 'password contains at least 1 character run(s)',
    meta: 1 } ]

SequenceValidator

Validates whether a password has sequences of characters, such as in ABCDlmnop.

const { neopass } = require('neopass')
 
const config = {
  /**
   * Fail if password contains four or more characters in sequence.
   */
  validators: ['sequence:4']
}
 
const neo = neopass(config)
 
const errors = neo.validate('ABCDlmnop')
console.log(errors)

Output:

[ { name: 'sequence',
    msg: 'password contains at least 2 character sequence(s)',
    meta: 2 } ]

ShannonValidator

Validates a password based on its Shannon entropy. Shannon entropy is given in raw bits per symbol. The validator multiplies this by the password length resulting in a number representing the entropy for the entire string: shannon(password) * length. Shannon entropy differs from class entropy in that no assumption is made about which character classes are represented by the password; only the symbols in the password itself count toward the bits per symbol calculation.

shannon('aaaa') // 0 bits per symbol

shannon('ab') // 1 bit per symbol

shannon('abcd') // 2 bits per symbol

shannon('01234567') // 3 bits per symbol

shannon('0123456789abcdef') // 4 bits per symbol

const { neopass } = require('neopass')
 
const config = {
  /**
   * The password must contain 32 or more bits of Shannon entropy.
   */
  validators: [ 'shannon:32' ]
}
 
const neo = neopass(config)
const errors1 = neo.validate('1111111111')
const errors2 = neo.validate('shannon')
const errors3 = neo.validate('E for Effort')
 
console.log('errors1:', errors1)
console.log('errors2:', errors2)
console.log('errors3:', errors3)

Output:

errors1: [ { name: 'shannon', msg: 'password is too simple', score: 0 } ]
errors2: [ { name: 'shannon', msg: 'password is too simple', score: 0.4655 } ]
errors3: [ { name: 'shannon', msg: 'password is too simple', score: 0.9457 } ]

TopologyValidator

Validates a password according to whether it conforms to certain common topology patterns.

const { neopass } = require('neopass')
 
const config = {
  /**
   * Configure the topology validator to use its standard patterns.
   */
  // validators: ['topology:standard=true']
 
  /**
   * Add some patterns to the standard ones.
   */
  validators: [
    {
      plugin: 'topology',
      options: {
        standard: true,
        patterns: [
          /^u+l+u+l+s+$/,   // ululs
          /^u+l+u+l+d+$/,   // ululd
          /^u+l+u+l+d+s+$/, // ululds
        ]
      }
    }
  ]
}
 
const neo = neopass(config)
 
const errors = neo.validate('Denver2016') // uld
console.log(errors)

Output:

[ { name: 'topology',
    msg: 'password matches vulnerable pattern topology' } ]

Configuring Validators

Short Form

The short-form configuration uses a string to reference the plugin and its options/arguments. In this case, options and arguments can be primitive types such as number, string, boolean, etc.

const config = {
  validators: ['length:min=10,max=72']
}

const config = {
  validators: ['entropy:64']
}

const config = {
  validators: ['topology:standard=true']
}

Long Form

The long-form configuration uses an object to reference the plugin and its options/arguments. Options and arguments can be objects and arrays, in addition to other types, such as RegExp.

const config = {
  validators: [{
    plugin: 'length',
    options: {
      min: 10,
      max: 72,
    },
  }]
}

const config = {
  validators: [{
    plugin: 'entropy',
    args: [ 64 ],
  }]
}

const config = {
  validators: [{
    plugin: 'topology',
    options: {
      patterns: [
        /^u+l+d+$/,
        /^u+l+s+$/,
        /^l+d+s+$/,
        ...
      ],
    },
  }]
}

Custom Validators

Custom validators can be used by either authoring a validator plugin or using in-line custom function validators:

/**
 * Create a custom validator function.
 */
function customDepth(): IValidator {
  // Create a validator object.
  const validator = {
    // Request depth from password info.
    request: ['depth'],
    // The core validator function.
    exec(depth: number) {
      if (depth < 62) {
        // Validation failure.
        const score = depth / 62
        return [{name: 'custom-depth', msg: 'password not complex enough', score}]
      }
    }
  }
 
  // Return the validator object.
  return validator
}
 
// Configure neopass.
const neo = neopass({
  validators: [
    customDepth
  ]
})
 
const errors = neo.validate('abcdefg')
console.log('errors:', errors)

Output:

errors: [
  {
    name: 'custom-depth',
    msg: 'password not complex enough',
    score: 0.41935483870967744
  }
]

Custom validators can also be used in the evaluation chain.

Optional Rules

If you want optional rules - that is, rules where some errors are treated as warnings - use the verify method which joins validation and evaluation. Validation failures are returned as errors and evaluation failures are returned as warnings.

import { neopass, INeoConfig } from 'neopass'
 
const config: INeoConfig = {
  validators: [
    'length:min=10,max=72',
    'classes:and=ul,or=ds',
  ],
 
  evaluators: [
    {
      validators: [
        'shannon:32',
        'entropy:64',
        'topology:standard=true',
      ],
    },
  ],
}
 
const neo = neopass(config)
 
const result = neo.verify('Denver2016')
console.log(result)

Output:

{
  errors: [],
  warnings: [
    {
      name: 'shannon',
      msg: 'password is too simple',
      score: 0.9756025296523007
    },
    {
      name: 'entropy',
      msg: 'password is either too short or not complex enough',
      score: 0.9303431734979493
    },
    {
      name: 'topology',
      message: 'password matches vulnerable pattern topology'
    }
  ]
}

Plugins

neopass runs on plugins. Generators and validators are all plugins and can be specified as part of the configuration.

Config:

import { neopass, INeoConfig } from 'neopass'
 
import {
  // Generators
  HexGenerator,
  LettersNumbersGenerator,
  RandomGenerator,
  // Validators
  ClassesValidator,
  CommonValidator,
  DepthValidator,
  EntropyValidator,
  LengthValidator,
  RunValidator,
  PassphraseDetector,
  SequenceValidator,
  ShannonValidator,
  TopologyValidator,
} from 'neopass/plugins'
 
/**
 * Configuration
 */
const config: INeoConfig = {
  // We'll specify our own list of plugins.
  useBuiltinGenerators: false,
  useBuiltinValidators: false,
 
  // Specify plugins to be registered.
  plugins: [
    new LettersNumbersGenerator(),
    new EntropyValidator(),
    new ShannonValidator(),
    new SequenceValidator(),
    new RunValidator(),
    new TopologyValidator(),
  ],
 
  // Configure the validation chain.
  validators: [
    'entropy:64',
    'shannon:32',
    'sequence:4',
    'run:3',
    'topology:standard=true',
  ]
}
 
const neo = neopass(config)

Generate

const pass = neo.generate(12, 'letters-numbers')
console.log('password:', pass)

Output:

password: v2mQsx6SKZ3s

Validate

Validate the generated password:

const errors = neo.validate('v2mQsx6SKZ3s')
console.log('errors:', errors)

Output:

errors: []

Validate some other password:

const errors = neo.validate('abcdefg777')
console.log('errors:', errors)

Output:

errors: [
  {
    name: 'entropy',
    msg: 'password is either too short or not complex enough',
    score: 0.8078007814753613
  },
  {
    name: 'shannon',
    msg: 'password is too simple',
    score: 0.8895122952096924
  },
  {
    name: 'sequence',
    message: 'password contains at least 2 character sequence(s)'
  },
  {
    name: 'run',
    message: 'password contains at least 1 character run(s)',
    meta: 1
  },
  {
    name: 'topology',
    message: 'password matches vulnerable pattern topology'
  }
]

Authoring a Validator Plugin

import { IValidator, ValidatorPlugin, IValidatorError } from 'neopass'
 
/**
 * A simplified version of the LengthValidator plugin
 */
export class SimpleLengthValidator extends ValidatorPlugin {
  // Implement required plugin name as a getter.
  get name() { return 'simple-length' }
 
  // Message helper.
  get msg() { return 'password too short!' }
 
  /**
   * This gets called to pass arguments to the plugin. For example,
   *
   *   validators: [ 'simple-length:10' ]
   *
   * will pass `10` to the configure method as the first
   * argument following `options`.
   */
  configure(options: any, min: number): IValidator {
    const validator: IValidator = {
      // Any requested password info will be passed to exec, in order.
      request: ['length'],
      // The validation logic.
      exec: (length: number) => {
        if (length < min) {
          const score = length / min
          // Return one or more error objects.
          return [{ name: this.name, msg: this.msg, score }]
        }
        // No errors! Can be null or undefined.
        return null
      }
    }
 
    return validator
  }
}

Configuration:

import { SimpleLengthValidator } from './somewhere'
 
const neo = neopass({
  plugins: [
    new SimpleLengthValidator()
  ],
 
  validators: [
    'simple-length:10'
  ]
})
 
neo.validate('abc')

Output:

[ { name: 'simple-length',
    msg: 'password too short!',
    score: 0.3 } ]

Plugins don't have to be subclasses of ValidatorPlugin or instances of classes at all. Any object that conforms to IPlugin will do:

/**
 * Create an object that implements IPlugin to act as
 * a validator plugin.
 */
const customLength: IPlugin<IValidator> = {
  type: 'validator',
  name: 'custom-length',
  configure(options: any, min: number) {
    const validator = {
      request: ['length'],
      exec(length: number) {
        if (length < min) {
          const score = length / min
          return [{name: 'custom-length', msg: 'password too short!', score}]
        }
      }
    }
    return validator
  }
}
 
const neo = neopass({
  plugins: [
    customLength,
  ],
  validators: [
    'custom-length:10',
  ]
})
 
neo.validate('abcdefg')

Output:

[ { name: 'custom-length',
    msg: 'password too short!',
    score: 0.7 } ]

Password Info

A validator plugin can request any of the following password info items:

interface IPasswordInfo {
  readonly password: string   // the password
  readonly length: number     // the length
  readonly depth: number      // the class depth
  readonly topology: string   // the password topology
  readonly classes: string    // the represented character classes
  readonly entropy: number    // the simple entropy
  readonly shannon: number    // the shannon entropy
}

password: the original password as given for validation. Scrutinize any plugin that requests this attribute!

length: the number of characters in the password.

depth: the per-character search space of the password, based on which character classes are present.

topology: the per-character classes of the password, e.g., topology('Abcd1$') => 'ulllds'. Scrutinize any plugin that requests this attribute!

classes: a reduction of the topology; that is, the character classes represented in the password, e.g., classes('Abcdefg') => 'ul'.

entropy: the base-2 logarithm of the depth, as bits per symbol/character.

shannon: the Shannon Entropy of the password in bits per symbol. Shannon entropy can be thought of as the overall complexity of the password, based on the diversity of symbols it contains.

As a rule, always request the minimum amount of information required to fulfill proper validation. For example:

• if you want to know what the password length is, request length and not password or topology.
• if you want to know which classes are represented, request classes and not topology.

There are legitimate reasons for a validator to request password. For instance, both the RunValidator and the SequenceValidator use password to determine if a password has runs of the same character or multiple characters in sequence. Most of the other validators request length, shannon, entropy and/or depth. The TopologyValidator requests topology. However it's dangerous to blindly trust plugins that request password or topology. It's safest to only use validators and generators that you author yourself.

Override Configured Chains

The validation and/or evaluation chain defined in the configuration can be overridden by passing a chain definition to validate or evaluate:

const config = {
  // Default validators.
  validators: [
    'length:min=10,max=72',
    'classes:and=ul,or=ds',
  ]
}
 
const neo = neopass(config)
 
// Create a custom validation chain.
const customValidators = [
  'entropy:64',
  'run:3',
  'sequence:4',
]
 
// Overide default validators.
const errors = neo.validate('skookum49', customValidators)
console.log('errors:', errors)

Output:

errors: [ { name: 'entropy',
    msg: 'password is either too short or not complex enough',
    score: 0.7270207033278251 } ]

The above also works with the evaluation chain.