openvpn-mgt/otp.go

package main

import (
	"time"
)

func (s *OpenVpnMgt) GenerateOTP(user string) ([]string, error) {
	return s.GenerateOTPGeneric(user, 30, "sha1", 10, 6)
}

// alternative OTP generator, not used at the moment
// func (s *OpenVpnMgt) GenerateSlackOTP(user string) ([]string, error) {
// 	return s.GenerateOTPGeneric(user, 60, "sha256", 30, 8)
// }

func (s *OpenVpnMgt) GenerateOTPGeneric(user string, period int, algo string, secretLen int, digits int) ([]string, error) {
	codes := []string{}
	now := time.Now()

	secret := encodeSecret(ComputeHmac256(user, s.otpMasterSecrets[0])[:secretLen])
	code, err := GenericTotpCode(secret, now, algo, digits, period)
	if err != nil {
		return codes, err
	}
	// the first code is the generic one
	codes = append(codes, code)

	for i := 1; i < 3; i++ {
		code, _ = GenericTotpCode(secret, now.Add(-1*time.Second*time.Duration(period*i)), algo, digits, period)
		codes = append(codes, code)
	}

	for j := 1; j < len(s.otpMasterSecrets); j++ {
		secret = encodeSecret(ComputeHmac256(user, s.otpMasterSecrets[j])[:secretLen])
		for i := 0; i < 3; i++ {
			code, _ = GenericTotpCode(secret, now.Add(-1*time.Second*time.Duration(period*i)), algo, digits, period)
			codes = append(codes, code)
		}
	}
	return codes, nil
}