otp

README

otp

Simple OTP (Time based OTP) implementation in Golang.

Usage

LICENSE

MIT.

Documentation

Index

• Variables
• func ComputeCode(secret string, challenge int64) (code string, err error)
• func NewScratchCode() int
• type OTPConfig
  • func Load(data []byte) (otp *OTPConfig, err error)
  • func New(scratchCodes int) *OTPConfig
  • func (otp *OTPConfig) Authenticate(password string) (bool, error)
  • func (otp *OTPConfig) GC()
  • func (otp *OTPConfig) ProvisionURI(user string, issuer string) string
  • func (otp *OTPConfig) Save() (data []byte, err error)

Variables

var (
	ErrInvalidCode      = errors.New("invalid code")
	ErrInvalidSecret    = errors.New("invalid secret")
	ErrInvalidChallenge = errors.New("invalid secret")
)

ErrInvalidCode indicate the supplied one-time code was not valid

Functions

func ComputeCode

func ComputeCode(secret string, challenge int64) (code string, err error)

ComputeCode computes the response code for a 64-bit challenge 'value' using the secret 'secret'.

func NewScratchCode

func NewScratchCode() int

NewScratchCode generates random scratch code (8 digits)

Types

type OTPConfig

type OTPConfig struct {
	Secret       string // 10 bytes base32 encoded string of the user's secret
	WindowSize   int    // valid range: technically 0..100 or so, but beyond 3-5 is probably bad security
	UsedCodes    []int  // timestamps in the current window unavailable for re-use
	ScratchCodes []int  // an array of 8-digit numeric codes that can be used to log in
}

OTPConfig is a one-time-password configuration. This object will be modified by calls to Authenticate and should be saved to ensure the codes are in fact only used once.

func Load

func Load(data []byte) (otp *OTPConfig, err error)

Load deserializes OTP configuration

func New

func New(scratchCodes int) *OTPConfig

New creates OTP authentincation instance

func (*OTPConfig) Authenticate

func (otp *OTPConfig) Authenticate(password string) (bool, error)

Authenticate a one-time-password against the given OTPConfig Returns true/false if the authentication was successful. Returns error if the password is incorrectly formatted (not a zero-padded 6 or non-zero-padded 8 digit number).

func (*OTPConfig) GC

func (otp *OTPConfig) GC()

GC (Garbage collect) - remove old UsedCodes

func (*OTPConfig) ProvisionURI

func (otp *OTPConfig) ProvisionURI(user string, issuer string) string

ProvisionURI generates a URI that can be turned into a QR code to configure a Authenticator app. It respects the recommendations on how to avoid conflicting accounts. See https://github.com/google/google-authenticator/wiki/Conflicting-Accounts

func (*OTPConfig) Save

func (otp *OTPConfig) Save() (data []byte, err error)

Save serializes OTP configuration