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yubigo.go
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package yubigo
import (
"bufio"
"crypto/hmac"
"crypto/sha1"
"crypto/tls"
"encoding/base64"
"errors"
"fmt"
"io"
"log"
"math/rand"
"net/http"
"regexp"
"sort"
"strings"
"sync"
"time"
)
var (
dvorakToQwerty = strings.NewReplacer(
"j", "c", "x", "b", "e", "d", ".", "e", "u", "f", "i", "g", "d", "h", "c", "i",
"h", "j", "t", "k", "n", "l", "b", "n", "p", "r", "y", "t", "g", "u", "k", "v",
"J", "C", "X", "B", "E", "D", ".", "E", "U", "F", "I", "G", "D", "H", "C", "I",
"H", "J", "T", "K", "N", "L", "B", "N", "P", "R", "Y", "T", "G", "U", "K", "V")
matchDvorak = regexp.MustCompile(`^[jxe.uidchtnbpygkJXE.UIDCHTNBPYGK]{32,48}$`)
matchQwerty = regexp.MustCompile(`^[cbdefghijklnrtuvCBDEFGHIJKLNRTUV]{32,48}$`)
signatureUrlFix = regexp.MustCompile(`\+`)
)
// Parse input string into yubikey prefix, ciphertext
func ParseOTP(otp string) (prefix string, ciphertext string, err error) {
if len(otp) < 32 || len(otp) > 48 {
err = errors.New("OTP has wrong length.")
return
}
// When otp matches dvorak-otp, then translate to qwerty.
if matchDvorak.MatchString(otp) {
otp = dvorakToQwerty.Replace(otp)
}
// Verify that otp matches qwerty expectations
if !matchQwerty.MatchString(otp) {
err = errors.New("Given string is not a valid Yubikey OTP. It contains invalid characters and/or the length is wrong.")
return
}
l := len(otp)
prefix = otp[0 : l-32]
ciphertext = otp[l-32 : l]
return
}
type YubiAuth struct {
id string
key []byte
apiServerList []string
protocol string
verifyCertificate bool
workers []*verifyWorker
use sync.Mutex
}
type verifyWorker struct {
client *http.Client
apiServer string
work chan *workRequest
stop chan bool
}
type workRequest struct {
paramString *string
resultChan chan *workResult
}
type workResult struct {
response *http.Response
requestQuery string
err error // indicates a failing server/network. This doesn't mean the OTP is invalid.
}
func (vw *verifyWorker) process() {
log.Println("Started worker...")
for {
select {
case w := <-vw.work:
log.Println("Have work.")
// Create url
url := vw.apiServer + *w.paramString
// Create request
request, err := http.NewRequest("GET", url, nil)
if err != nil {
w.resultChan <- &workResult{
response: nil,
requestQuery: url,
err: errors.New(fmt.Sprintf("Could not create http request. Error: %s\n", err)),
}
continue
}
request.Header.Add("User-Agent", "github.com/GeertJohan/yubigo")
// Call server
response, err := vw.client.Do(request)
// If we received an error from the client, return that (wrapped) on the channel.
if err != nil {
w.resultChan <- &workResult{
response: nil,
requestQuery: url,
err: errors.New(fmt.Sprintf("Fail in client: %s\n", err)),
}
continue
}
// It seems everything is ok! return the response (wrapped) on the channel.
w.resultChan <- &workResult{
response: response,
requestQuery: url,
err: nil,
}
continue
case <-vw.stop:
return
}
}
}
// Create a yubiAuth instance with given API-id and API-key.
// Returns an error when the key could not be base64 decoded.
func NewYubiAuth(id string, key string) (auth *YubiAuth, err error) {
keyBytes, err := base64.StdEncoding.DecodeString(key)
if err != nil {
err = errors.New(fmt.Sprintf("Given key seems to be invalid. Could not base64_decode. Error: %s\n", err))
return
}
auth = &YubiAuth{
id: id,
key: keyBytes,
apiServerList: []string{"api.yubico.com/wsapi/2.0/verify",
"api2.yubico.com/wsapi/2.0/verify",
"api3.yubico.com/wsapi/2.0/verify",
"api4.yubico.com/wsapi/2.0/verify",
"api5.yubico.com/wsapi/2.0/verify"},
protocol: "https://",
verifyCertificate: true,
}
auth.buildWorkers()
return
}
func (ya *YubiAuth) buildWorkers() {
// Unexported (internal) method, so no locking.
// create tls config
tlsConfig := &tls.Config{}
if !ya.verifyCertificate {
tlsConfig.InsecureSkipVerify = true
}
// stop all existing workers
for _, worker := range ya.workers {
worker.stop <- true
}
// create new (empty) slice with exact capacity
ya.workers = make([]*verifyWorker, 0, len(ya.apiServerList))
// start new workers. One for each apiServerString
for _, apiServer := range ya.apiServerList {
// create worker instance with new http.Client instance
worker := &verifyWorker{
client: &http.Client{
Transport: &http.Transport{
TLSClientConfig: tlsConfig,
},
},
apiServer: ya.protocol + apiServer + "?",
work: make(chan *workRequest),
stop: make(chan bool),
}
ya.workers = append(ya.workers, worker)
// start worker process in new goroutine
go worker.process()
}
}
// Use this method to specify a list of servers for verification.
// Each server string should contain host + path.
// Example: "api.yubico.com/wsapi/2.0/verify".
func (ya *YubiAuth) SetApiServerList(urls ...string) {
// Lock
ya.use.Lock()
defer ya.use.Unlock()
// change setting
ya.apiServerList = urls
// rebuild workers
ya.buildWorkers()
}
// Retrieve the the ist of servers that are being used for verification.
func (ya *YubiAuth) GetApiServerList() []string {
return ya.apiServerList
}
// Enable or disable the use of https
func (ya *YubiAuth) UseHttps(useHttps bool) {
// Lock
ya.use.Lock()
defer ya.use.Unlock()
// change setting
if useHttps {
ya.protocol = "https://"
} else {
ya.protocol = "http://"
}
// rebuild workers
ya.buildWorkers()
}
// Enable or disable https certificate verification
// Disable this at your own risk.
func (ya *YubiAuth) HttpsVerifyCertificate(verifyCertificate bool) {
// Lock
ya.use.Lock()
defer ya.use.Unlock()
// change setting
ya.verifyCertificate = verifyCertificate
// rebuild workers
ya.buildWorkers()
}
// The verify method calls the API with given OTP and returns if the OTP is valid or not.
// This method will return an error if something unexpected happens
// If no error was returned, the returned 'ok bool' indicates if the OTP is valid
// if the 'ok bool' is true, additional informtion can be found in the returned YubiResponse object
func (ya *YubiAuth) Verify(otp string) (yr *YubiResponse, ok bool, err error) {
// Lock
ya.use.Lock()
defer ya.use.Unlock()
// check the OTP
_, _, err = ParseOTP(otp)
if err != nil {
return nil, false, err
}
// create slice to store parameters for this verification request
paramSlice := make([]string, 0) //++ Add initial len/cap
paramSlice = append(paramSlice, "id="+ya.id)
paramSlice = append(paramSlice, "otp="+otp)
// Create 40 characters nonce
rand.Seed(time.Now().UnixNano())
k := make([]rune, 40)
for i := 0; i < 40; i++ {
c := rand.Intn(35)
if c < 10 {
c += 48 // numbers (0-9) (0+48 == 48 == '0', 9+48 == 57 == '9')
} else {
c += 87 // lower case alphabets (a-z) (10+87 == 97 == 'a', 35+87 == 122 = 'z')
}
k[i] = rune(c)
}
nonce := string(k)
paramSlice = append(paramSlice, "nonce="+nonce)
// These settings are hardcoded in the library for now.
//++ TODO(GeertJohan): add these values to the yubiAuth object and create getters/setters
// paramSlice = append(paramSlice, "timestamp=1")
paramSlice = append(paramSlice, "sl=secure")
//++ TODO(GeertJohan): Add timeout support?
//++ //paramSlice = append(paramSlice, "timeout=")
// sort the slice
sort.Strings(paramSlice)
// create parameter string
paramString := strings.Join(paramSlice, "&")
// generate signature
if len(ya.key) > 0 {
hmacenc := hmac.New(sha1.New, ya.key)
_, err := hmacenc.Write([]byte(paramString))
if err != nil {
return nil, false, errors.New(fmt.Sprintf("Could not calculate signature. Error: %s\n", err))
}
signature := base64.StdEncoding.EncodeToString(hmacenc.Sum([]byte{}))
signature = signatureUrlFix.ReplaceAllString(signature, `%2B`)
paramString = paramString + "&h=" + signature
}
// create result channel, buffersize equals the amount of workers.
resultChan := make(chan *workResult, len(ya.workers))
// create workRequest instance
wr := &workRequest{
paramString: ¶mString,
resultChan: resultChan,
}
// send workRequest to each worker
for _, worker := range ya.workers {
worker.work <- wr
}
// count the errors so we can handle when all servers fail (network fail for instance)
errCount := 0
// local result var, will contain the first result we have
var result *workResult
// keep looping until we have a good result
for {
// listen for result from a worker
result = <-resultChan
// check for error
if result.err != nil {
// increment error counter
errCount++
// development logging
log.Printf("A server (%s) gave error back: %s\n", result.requestQuery, result.err)
if errCount == len(ya.apiServerList) {
// All workers are done, there's nothing left to try. we return an error.
return nil, false, errors.New("None of the servers responded properly.")
}
// we have an error, but not all workers responded yet, so lets wait for the next result.
continue
}
// create a yubiResult from the workers response.
yr, err = newYubiResponse(result)
if err != nil {
return nil, false, err
}
// Check for "REPLAYED_REQUEST" result.
if status, _ := yr.resultParameters["status"]; status == "REPLAYED_REQUEST" {
// The result status is "REPLAYED_REQUEST".
// This means that the server for this request got sync with an other server before our request.
// Lets wait for the result from the other server.
// See: http://forum.yubico.com/viewtopic.php?f=3&t=701
// increment error counter
errCount++
// development logging
log.Println("Got replayed request: ", result.response.Body)
if errCount == len(ya.apiServerList) {
// All workers are done, there' is nothing left to try. We return an error.
return nil, false, errors.New("None of the servers responded properly.")
}
// We have a replayed request, but not all workers responded yet, so lets wait for the next result.
continue
}
// No error or REPLAYED_REQUEST. Seems like we have a proper result.
break
}
// check status
status, ok := yr.resultParameters["status"]
if !ok || status != "OK" {
switch status {
case "BAD_OTP":
return yr, false, nil
case "REPLAYED_OTP":
return yr, false, errors.New("The OTP is valid, but has been used before. If you receive this error, you might be the victim of a man-in-the-middle attack.")
case "BAD_SIGNATURE":
return yr, false, errors.New("Signature verification at the api server failed. The used id/key combination could be invalid or is not activated (yet).")
case "NO_SUCH_CLIENT":
return yr, false, errors.New("The api server does not accept the given id. It might be invalid or is not activated (yet).")
case "OPERATION_NOT_ALLOWED":
return yr, false, errors.New("The api server does not allow the given api id to verify OTPs.")
case "BACKEND_ERROR":
return yr, false, errors.New("The api server seems to be broken. Please contact the api servers system administration (yubico servers? contact yubico).")
case "NOT_ENOUGH_ANSWERS":
return yr, false, errors.New("The api server could not get requested number of syncs during before timeout")
case "REPLAYED_REQUEST":
panic("Unexpected. This status should've been catched in the worker response loop.")
return yr, false, errors.New("The api server has seen this unique request before. If you receive this error, you might be the victim of a man-in-the-middle attack.")
default:
return yr, false, errors.New(fmt.Sprintf("Unknown status parameter (%s) sent by api server.", status))
}
}
// check otp
otpCheck, ok := yr.resultParameters["otp"]
if !ok || otp != otpCheck {
return nil, false, errors.New("Could not validate otp value from server response.")
}
// check nonce
nonceCheck, ok := yr.resultParameters["nonce"]
if !ok || nonce != nonceCheck {
return nil, false, errors.New("Could not validate nonce value from server response.")
}
// check attached signature with remake of that signature, if key is actually in use.
if len(ya.key) > 0 {
receivedSignature, ok := yr.resultParameters["h"]
if !ok || len(receivedSignature) == 0 {
return nil, false, errors.New("No signature hash was attached by the api server, we do expect one though. This might be a hacking attempt.")
}
// create a slice with the same size-1 as the parameters map (we're leaving the hash itself out of it's replica calculation)
receivedValuesSlice := make([]string, 0, len(yr.resultParameters)-1)
for key, value := range yr.resultParameters {
if key != "h" {
receivedValuesSlice = append(receivedValuesSlice, key+"="+value)
}
}
sort.Strings(receivedValuesSlice)
receivedValuesString := strings.Join(receivedValuesSlice, "&")
hmacenc := hmac.New(sha1.New, ya.key)
_, err := hmacenc.Write([]byte(receivedValuesString))
if err != nil {
return nil, false, errors.New(fmt.Sprintf("Could not calculate signature replica. Error: %s\n", err))
}
recievedSignatureReplica := base64.StdEncoding.EncodeToString(hmacenc.Sum([]byte{}))
if receivedSignature != recievedSignatureReplica {
return nil, false, errors.New("The received signature hash is not valid. This might be a hacking attempt.")
}
}
// we're done!
yr.validOTP = true
return yr, true, nil
}
// Contains details about yubikey OTP verification.
type YubiResponse struct {
requestQuery string //++ rename to requestQuery
resultParameters map[string]string //++ rename to resultParameters
validOTP bool //++ rename to validOTP
}
func newYubiResponse(result *workResult) (*YubiResponse, error) {
bodyReader := bufio.NewReader(result.response.Body)
yr := &YubiResponse{}
yr.resultParameters = make(map[string]string)
yr.requestQuery = result.requestQuery
for {
// read through the response lines
line, err := bodyReader.ReadString('\n')
fmt.Println(line)
// handle error, which at one point should be an expected io.EOF (end of file)
if err != nil {
if err == io.EOF {
break // successfully done with reading lines, lets break this for loop
}
return nil, errors.New(fmt.Sprintf("Could not read result body from the server. Error: %s\n", err))
}
// parse result lines, split on first '=', trim \n and \r
keyvalue := strings.SplitN(line, "=", 2)
if len(keyvalue) == 2 {
yr.resultParameters[keyvalue[0]] = strings.Trim(keyvalue[1], "\n\r")
}
}
return yr, nil
}
// Returns wether the verification was successful
func (yr *YubiResponse) IsValidOTP() bool {
return yr.validOTP
}
// Get the requestQuery that was used during verification.
func (yr *YubiResponse) GetRequestQuery() string {
return yr.requestQuery
}
// Retrieve a parameter from the api's response
func (yr *YubiResponse) GetResultParameter(key string) (value string) {
value, ok := yr.resultParameters[key]
if !ok {
value = ""
}
return value
}