netbird/management/server/turncredentials.go

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package server
import (
"crypto/hmac"
"crypto/sha1"
"encoding/base64"
"fmt"
"github.com/netbirdio/netbird/management/proto"
log "github.com/sirupsen/logrus"
"sync"
"time"
)
// TURNCredentialsManager used to manage TURN credentials
type TURNCredentialsManager interface {
GenerateCredentials() TURNCredentials
SetupRefresh(peerKey string)
CancelRefresh(peerKey string)
}
// TimeBasedAuthSecretsManager generates credentials with TTL and using pre-shared secret known to TURN server
type TimeBasedAuthSecretsManager struct {
mux sync.Mutex
config *TURNConfig
updateManager *PeersUpdateManager
cancelMap map[string]chan struct{}
}
type TURNCredentials struct {
Username string
Password string
}
func NewTimeBasedAuthSecretsManager(updateManager *PeersUpdateManager, config *TURNConfig) *TimeBasedAuthSecretsManager {
return &TimeBasedAuthSecretsManager{
mux: sync.Mutex{},
config: config,
updateManager: updateManager,
cancelMap: make(map[string]chan struct{}),
}
}
// GenerateCredentials generates new time-based secret credentials - basically username is a unix timestamp and password is a HMAC hash of a timestamp with a preshared TURN secret
func (m *TimeBasedAuthSecretsManager) GenerateCredentials() TURNCredentials {
mac := hmac.New(sha1.New, []byte(m.config.Secret))
timeAuth := time.Now().Add(m.config.CredentialsTTL.Duration).Unix()
username := fmt.Sprint(timeAuth)
_, err := mac.Write([]byte(username))
if err != nil {
log.Errorln("Generating turn password failed with error: ", err)
}
bytePassword := mac.Sum(nil)
password := base64.StdEncoding.EncodeToString(bytePassword)
return TURNCredentials{
Username: username,
Password: password,
}
}
func (m *TimeBasedAuthSecretsManager) cancel(peerID string) {
if channel, ok := m.cancelMap[peerID]; ok {
close(channel)
delete(m.cancelMap, peerID)
}
}
// CancelRefresh cancels scheduled peer credentials refresh
func (m *TimeBasedAuthSecretsManager) CancelRefresh(peerID string) {
m.mux.Lock()
defer m.mux.Unlock()
m.cancel(peerID)
}
// SetupRefresh starts peer credentials refresh. Since credentials are expiring (TTL) it is necessary to always generate them and send to the peer.
// A goroutine is created and put into TimeBasedAuthSecretsManager.cancelMap. This routine should be cancelled if peer is gone.
func (m *TimeBasedAuthSecretsManager) SetupRefresh(peerID string) {
m.mux.Lock()
defer m.mux.Unlock()
m.cancel(peerID)
cancel := make(chan struct{}, 1)
m.cancelMap[peerID] = cancel
log.Debugf("starting turn refresh for %s", peerID)
go func() {
//we don't want to regenerate credentials right on expiration, so we do it slightly before (at 3/4 of TTL)
ticker := time.NewTicker(m.config.CredentialsTTL.Duration / 4 * 3)
for {
select {
case <-cancel:
log.Debugf("stopping turn refresh for %s", peerID)
return
case <-ticker.C:
c := m.GenerateCredentials()
var turns []*proto.ProtectedHostConfig
for _, host := range m.config.Turns {
turns = append(turns, &proto.ProtectedHostConfig{
HostConfig: &proto.HostConfig{
Uri: host.URI,
Protocol: ToResponseProto(host.Proto),
},
User: c.Username,
Password: c.Password,
})
}
update := &proto.SyncResponse{
WiretrusteeConfig: &proto.WiretrusteeConfig{
Turns: turns,
},
}
log.Debugf("sending new TURN credentials to peer %s", peerID)
err := m.updateManager.SendUpdate(peerID, &UpdateMessage{Update: update})
if err != nil {
log.Errorf("error while sending TURN update to peer %s %v", peerID, err)
// todo maybe continue trying?
}
}
}
}()
}