package otp

import "code.soquee.net/otp"

Package otp implemnts HOTP and TOTP one-time passwords.

package main

import (
	"crypto/sha256"
	"fmt"
	"time"

	"code.soquee.net/otp"
)

func main() {
	const secret = "12345678901234567890123456789012"

	o := otp.NewOTP([]byte(secret), 8, sha256.New, otp.TOTP(30*time.Second, func() time.Time {
		// You would normally pass in time.Now, or possibly a time function that
		// subtracts some multiple of the period to correct for clock-drift.
		tt, _ := time.Parse("2006-01-02 15:04:05", "1970-01-01 00:00:59")
		return tt
	}))
	fmt.Println(o(0, nil))
}

46119246

Index ¶

• func NewOTP(key []byte, l int, h func() hash.Hash, c CounterFunc) func(offset int, dst []byte) int32
• func URL(key []byte, step time.Duration, l int, hash crypto.Hash, domain, email string) *url.URL
• type CounterFunc
• func TOTP(step time.Duration, t func() time.Time) CounterFunc

Examples ¶

• package (Totp)

Functions ¶

func NewOTP ¶

func NewOTP(key []byte, l int, h func() hash.Hash, c CounterFunc) func(offset int, dst []byte) int32

NewOTP returns a function that generates hmac-based one-time. Each time the returned function is called it calls c and appends the one-time password to dst. It also returns a 31-bit representation of the value. The key is the shared secret, l is the length of the output number (if l is less than or equal to 0, NewOTP panics), h is a function that returns the inner and outer hash mechanisms for the HMAC, and c returns the seed used to generate the key.

func URL ¶

func URL(key []byte, step time.Duration, l int, hash crypto.Hash, domain, email string) *url.URL

URL returns a URL that is compatible with many popular OTP apps such as FreeOTP, Yubico Authenticator, and Google Authenticator.

Supported hashes are SHA1, SHA256, and SHA512. Anything else will default to SHA1.

Types ¶

type CounterFunc ¶

type CounterFunc func(offset int) uint64

CounterFunc is a function that is called when generating a one-time password and returns a seed value. In HOTP this will be an incrementing counter, in TOTP it is a function of the current time. Offset indicates that we want the token relative to the current token by offset (eg. -1 for the previous token).

func TOTP ¶

func TOTP(step time.Duration, t func() time.Time) CounterFunc

TOTP returns a counter function that can be used to generate HOTP tokens compatible with the Time-Based One-Time Password Algorithm (TOTP) defined in RFC 6238.

If a zero duration is provided, a default of 30 seconds is used. If no time function is provided, time.Now is used.

Source Files ¶

otp.go