otp

README

This package is an implementation of RFC 4226: HOTP: An HMAC-Based One-Time Password Algorithm and RFC 6238: TOTP: Time-Based One-Time Password Algorithm with slight deviations from the RFC based on the algorithmic reference implementation and tested using the RFC test values to ensure comaptibility with other HOTP and TOTP systems.

Installation

Clone this repository into your Go src directory or pull it automatically with:

$ go get github.com/jonfriesen/otp

Usage

import "github.com/jonfriesen/otp"
...
// To generate and checking a Time base OTP
totpToken := NewTOTP("secret", Time, 8, 30, 2, sha1.New)
totp := totpToken.Generate()
isValid := totp == totpToken.Check("12345678")
...
// To generate and checking a HMAC OTP 
hotpToken := NewHOTP("secret", 0, 6, 5, sha1.New)
hotp := hotpToken.Generate()
isValid := hotp == hotpToken.Check("123456")

Considerations and Variations from RFC

Checksum

The checksum option is not included in this implementation as I feel most real world implementations don't use it or account for it.

Truncation Offset

The truncation offset is intended to give the entire hash digest the opportunity to contribute to the truncated portion of the hash. Removing this section does not make the algorithm more or less secure.

Motivation

The OTP package was created to offer a simple, close implementation of RFC 4226 and RFC 6238 for easy consumption in Go.

Contributions

Pull Requests are welcome, please include tests covering your contributions.

_{MIT License Copyright (c) 2022 Jonathan Friesen}

Documentation

Index

• func Secret(isBase32 bool) string
• type Hotp
  • func NewHOTP(c *HotpConfig) *Hotp
  • func (h Hotp) Check(otp string) (bool, int)
  • func (h Hotp) Generate() string
  • func (h Hotp) Sync(otp1 string, otp2 string) (bool, int)
• type HotpConfig
• type Totp
  • func NewTOTP(c *TotpConfig) *Totp
  • func (t Totp) Check(otp string) bool
  • func (t Totp) Generate() string
• type TotpConfig

Functions

func Secret

func Secret(isBase32 bool) string

Secret Quickly Generates a Secret of 20 characters

Types

type Hotp

type Hotp struct {
	Secret   string
	Count    int
	Length   int
	Window   int
	IsBase32 bool
	Hasher   func() hash.Hash
}

Hotp is a struct holding the details for a hmac-sha1 otp

func NewHOTP

func NewHOTP(c *HotpConfig) *Hotp

NewHOTP constructor for hotp object

func (Hotp) Check

func (h Hotp) Check(otp string) (bool, int)

Check validates an HOTP accepts secret, count, length to generate the OTP's to validate an incoming OTP, and how many times to increase the validation count

func (Hotp) Generate

func (h Hotp) Generate() string

Generate Generates an HOTP Note: HOTP recommended length is 6 as per RFC 4226

func (Hotp) Sync

func (h Hotp) Sync(otp1 string, otp2 string) (bool, int)

Sync checks next OTP until it finds two sequential matches max of 100 checks returns success and new count location

type HotpConfig

type HotpConfig struct {
	Secret    string
	Count     int
	Length    int
	Window    int
	UseBase32 bool
	Crypto    string
}

HotpConfig holds user friendly configurations for creating tokens using the NewHOTP function otherwise the Hotp object can be created independantly.

type Totp

type Totp struct {
	Secret     string
	TimeBox    time.Time
	Length     int
	Window     int
	WindowSize int
	IsBase32   bool
	Hasher     func() hash.Hash
}

Totp is a struct holding the details for a time based hmac-sha1 otp

func NewTOTP

func NewTOTP(c *TotpConfig) *Totp

NewTOTP constructor for hotp object func NewTOTP(secret string, TimeBox time.Time, length int, window int, windowSize int, isBase32 bool, hasher func() hash.Hash) *Totp {

func (Totp) Check

func (t Totp) Check(otp string) bool

Check validates an TOTP accepts secret, time, length to generate the OTP's to validate an incoming OTP, and how many times to increase the validation count

func (Totp) Generate

func (t Totp) Generate() string

Generate Generates an TOTP Note: TOTP recommended length is 8 as per RFC 6238

type TotpConfig

type TotpConfig struct {
	Secret     string
	Time       time.Time
	Length     int
	Window     int
	WindowSize int
	UseBase32  bool
	Crypto     string
}

TotpConfig holds user friendly configurations for creating tokens using the NewTOTP function otherwise the Hotp object can be created independantly.