otp

README

otp

otp is an easy-to-use implementation of RFC 4226 (HOTP) and RFC 6238 (TOTP) in Go.

Only base-32 encoded secret-keys are supported.

Supported hash functions: SHA1, SHA256, and SHA512 (the latter two from the SHA-2 family, not SHA-3).

Usage Overview

package main

import (
	"fmt"
	"log"

	"codeberg.org/ar324/otp"
)

func main() {
	// HOTP
	hk := otp.HOTPKey{
		SecretKey:    "GEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQ",
		HashFunction: otp.SHA1,
		Digits:       8,
		Counter:      0x0000000000000001,
	}
	if !hk.Validate() {
		log.Fatalln("invalid HOTP parameters")
	}
	fmt.Println(hk.OTP()) // prints "94287082"

	// TOTP
	tk := otp.TOTPKey{
		SecretKey:    "GEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQ",
		HashFunction: otp.SHA512,
		Digits:       8,
		TimeStep:     60,
	}
	if !tk.Validate() {
		log.Fatalln("invalid TOTP parameters")
	}
	tk.OTP() // "88486101"
}

Documentation

Overview

Package 'otp' is an easy-to-use implementation of RFC 4226 (HOTP) and RFC 6238 (TOTP).

Index

• type HOTPKey
  • func (k *HOTPKey) OTP() string
  • func (k *HOTPKey) Validate() bool
• type HashFunction
• type TOTPKey
  • func (k *TOTPKey) OTP() string
  • func (k *TOTPKey) Validate() bool

Types

type HOTPKey

type HOTPKey struct {
	SecretKey    string       `json:"secret_key"`
	HashFunction HashFunction `json:"hash_function"`
	Digits       byte         `json:"digits"`
	Counter      uint64       `json:"counter"`
}

Represents an HOTP parameter-set. SecretKey must be base-32 encoded.

func (*HOTPKey) OTP

func (k *HOTPKey) OTP() string

Computes and returns an OTP using the HOTP parameter-set. If the receiver HOTPKey is invalid, the program panics.

func (*HOTPKey) Validate

func (k *HOTPKey) Validate() bool

Validates an HOTPKey.

type HashFunction

type HashFunction string

const (
	SHA1   HashFunction = "SHA1"
	SHA256 HashFunction = "SHA256"
	SHA512 HashFunction = "SHA512"

	MinKeySize = 16
	MaxDigits  = 10
)

type TOTPKey

type TOTPKey struct {
	SecretKey    string       `json:"secret_key"`
	HashFunction HashFunction `json:"hash_function"`
	Digits       byte         `json:"digits"`
	TimeStep     uint64       `json:"time_step"`
	T0           uint64       `json:"t0"`
}

Represents a TOTP parameter-set. Like in HOTPKey, SecretKey must be base-32 encoded. Even though T0 not a parameter in virtually all implementations, according to RFC 6238, it is not necessarily always 0—which is why it is a parameter here.

func (*TOTPKey) OTP

func (k *TOTPKey) OTP() string

Computes and returns an OTP using the TOTP parameter-set. If the receiver TOTPKey is invalid, the program panics.

func (*TOTPKey) Validate

func (k *TOTPKey) Validate() bool

Validates a TOTPKey.