Base64 encode the service ID in the webhook path

We don't put any restrictions on the format of the Service ID so we need to
base64 it to prevent potentially losing data when it is inserted as a path
parameter (e.g. due to weird escaping rules).

Also, only remove webhooks if there was an old service to begin with.

src/github.com/matrix-org/go-neb/api.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"database/sql"
+	"encoding/base64"
 	"encoding/json"
 	log "github.com/Sirupsen/logrus"
 	"github.com/matrix-org/go-neb/clients"
@@ -126,8 +127,19 @@ type webhookHandler struct {
 
 func (wh *webhookHandler) handle(w http.ResponseWriter, req *http.Request) {
 	segments := strings.Split(req.URL.Path, "/")
-	// last path segment is the service ID which we will pass the incoming request to
-	srvID := segments[len(segments)-1]
+	// last path segment is the service ID which we will pass the incoming request to,
+	// but we've base64d it.
+	base64srvID := segments[len(segments)-1]
+	bytesSrvID, err := base64.StdEncoding.DecodeString(base64srvID)
+	srvID := string(bytesSrvID)
+	if err != nil {
+		log.WithError(err).WithField("base64_service_id", base64srvID).Print(
+			"Not a b64 encoded string",
+		)
+		w.WriteHeader(400)
+		return
+	}
+
 	service, err := wh.db.LoadService(srvID)
 	if err != nil {
 		log.WithError(err).WithField("service_id", srvID).Print("Failed to load service")

src/github.com/matrix-org/go-neb/services/github/github.go

@@ -221,6 +221,7 @@ func (s *githubService) PostRegister(oldService types.Service) {
 		log.Errorf("PostRegister: %s does not have a github session", s.ClientUserID)
 		return
 	}
+	if oldService != nil {
 		old, ok := oldService.(*githubService)
 		if !ok {
 			log.Error("PostRegister: Provided old service is not of type GithubService")
@@ -235,6 +236,7 @@ func (s *githubService) PostRegister(oldService types.Service) {
 
 		// remove any existing webhooks this service created on the user's behalf
 		modifyWebhooks(old, cli, true)
+	}
 
 	// make new webhooks according to service config
 	modifyWebhooks(s, cli, false)

src/github.com/matrix-org/go-neb/types/types.go

@@ -1,6 +1,7 @@
 package types
 
 import (
+	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"github.com/matrix-org/go-neb/matrix"
@@ -72,7 +73,9 @@ func CreateService(serviceID, serviceType string, serviceJSON []byte) (Service,
 	if f == nil {
 		return nil, errors.New("Unknown service type: " + serviceType)
 	}
-	webhookEndpointURL := baseURL + "services/hooks/" + serviceID
+
+	base64ServiceID := base64.StdEncoding.EncodeToString([]byte(serviceID))
+	webhookEndpointURL := baseURL + "services/hooks/" + base64ServiceID
 	service := f(serviceID, webhookEndpointURL)
 	if err := json.Unmarshal(serviceJSON, service); err != nil {
 		return nil, err