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totp.go
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totp.go
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package otp
import "time"
// TOTP is used to generate tokens based on RFC-6238.
//
// Example:
//
// totp := &TOTP{Secret: "your-secret", IsBase32Secret: true}
// token := totp.Get()
//
// TOTP assumes a set of default values for Secret, Length, Time, Period, WindowBack, WindowForward and IsBase32Secret
//
// If no Secret is informed, TOTP will generate a random one that you need to store with the Counter, for future token
// verifications.
//
// Check this package constants to see the current default values.
type TOTP struct {
Secret string // The secret used to generate a token
Length uint8 // The token length
Time time.Time // The time used to generate the token
IsBase32Secret bool //
Period uint8 // The step size to slice time, in seconds
WindowBack uint8 // How many steps HOTP will go backwards to validate a token
WindowForward uint8 // How many steps HOTP will go forward to validate a token
}
func (t *TOTP) setDefaults() {
if len(t.Secret) == 0 {
t.Secret = generateRandomSecret(DefaultRandomSecretLength, t.IsBase32Secret)
}
if t.Length == 0 {
t.Length = DefaultLength
}
if t.Time.IsZero() {
t.Time = time.Now()
}
if t.Period == 0 {
t.Period = DefaultPeriod
}
if t.WindowBack == 0 {
t.WindowBack = DefaultWindowBack
}
if t.WindowForward == 0 {
t.WindowForward = DefaultWindowForward
}
}
func (t *TOTP) normalize() {
if t.Length > MaxLength {
t.Length = MaxLength
}
}
// Get a time-based token
func (t *TOTP) Get() string {
t.setDefaults()
t.normalize()
ts := uint64(t.Time.Unix() / int64(t.Period))
hotp := &HOTP{Secret: t.Secret, Counter: ts, Length: t.Length, IsBase32Secret: t.IsBase32Secret}
return hotp.Get()
}
// Now is a fluent interface to set the TOTP generator's time to the current date/time
func (t *TOTP) Now() *TOTP {
t.Time = time.Now()
return t
}
// Verify a token with the current settings, including the WindowBack and WindowForward
func (t TOTP) Verify(token string) bool {
t.setDefaults()
t.normalize()
givenTime := t.Time
for i := int(t.WindowBack) * -1; i <= int(t.WindowForward); i++ {
t.Time = givenTime.Add(time.Second * time.Duration(int(t.Period)*i))
if t.Get() == token {
return true
}
}
return false
}