milo: Enable Swarming LogDog log loading.

milo/appengine/logdog/http.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package logdog
 
 import (
         "net/http"
         "strings"
 
@@ skipping 52 matching lines @@
         if _, err := as.Load(c); err != nil {
                 return nil, err
         }
 
         // Convert the Milo Annotation protobuf to Milo objects.
         return &templates.Args{
                 "Build": as.toMiloBuild(c),
         }, nil
 }
 
+func resolveHost(host string) (string, error) {
+        // Resolveour our Host, and validate it against a host whitelist.
+        switch host {
+        case "":
+                return defaultLogDogHost, nil
+        case defaultLogDogHost, "luci-logdog-dev.appspot.com":
+                return host, nil
+        default:
+                return "", errors.Reason("host %(host)q is not whitelisted").
+                        D("host", host).
+                        Err()
+        }
+}
+
 // NewClient generates a new LogDog client that issues requests on behalf of the
 // current user.
 func NewClient(c context.Context, host string) (*coordinator.Client, error) {
-        if host == "" {
-                host = defaultLogDogHost
+        var err error
+        if host, err = resolveHost(host); err != nil {
+                return nil, err
         }
 
         // Initialize the LogDog client authentication.
         t, err := auth.GetRPCTransport(c, auth.AsUser)
         if err != nil {
                 return nil, errors.New("failed to get transport for LogDog server")
         }
 
         // Setup our LogDog client.
         return coordinator.NewClient(&prpc.Client{
                 C: &http.Client{
                         Transport: t,
                 },
                 Host: host,
         }), nil
 }