[Chromoting] Implement UpdateConfig() for the Windows host.

remoting/host/elevated_controller_win.cc

Index: remoting/host/elevated_controller_win.cc
diff --git a/remoting/host/elevated_controller_win.cc b/remoting/host/elevated_controller_win.cc
index e5b655e6439a262484ce1fee3f2527a01293b040..e23660ca9a4b667d05f3f45ac53847bc3f56858e 100644
--- a/remoting/host/elevated_controller_win.cc
+++ b/remoting/host/elevated_controller_win.cc
@@ -327,7 +327,39 @@ STDMETHODIMP ElevatedControllerWin::StopDaemon() {
 }
 
 STDMETHODIMP ElevatedControllerWin::UpdateConfig(BSTR config) {
-  return E_NOTIMPL;
+  // Parse the config.
+  std::string config_str = UTF16ToUTF8(
+    string16(static_cast<char16*>(config), ::SysStringLen(config)));
+  scoped_ptr<base::Value> config_value(base::JSONReader::Read(config_str));
+  if (!config_value.get()) {
+    return E_FAIL;
+  }
+  base::DictionaryValue* config_dict = NULL;
+  if (!config_value->GetAsDictionary(&config_dict)) {
+    return E_FAIL;
+  }
+  // The config must not contain host_id or xmpp_login.

[alexeypa (please no reviews), 2012/04/16 22:36:35]

It is better to have an explicit list of banned keys so it would be easier to
add more keys later.

[simonmorris, 2012/04/16 23:20:23]

Done.

+  if (config_dict->HasKey(kHostId) || config_dict->HasKey(kXmppLogin)) {

[Jamie, 2012/04/16 22:26:48]

This is probably not a discussion for this CL (as it's a cross-platform issue),
but might we be better off having a whitelist of things you are allowed to
update (basically just the PIN, I think), rather than a blacklist?

[alexeypa (please no reviews), 2012/04/16 22:36:35]

The last time we discussed this with sergeyu@ the conclusion was to blacklist
rather than to whitelist.

+    return E_FAIL;
+  }
+  // Get the old config.
+  FilePath config_dir = remoting::GetConfigDir();
+  scoped_ptr<base::DictionaryValue> config_old;
+  HRESULT hr = ReadConfig(config_dir.Append(kConfigFileName), &config_old);
+  if (FAILED(hr)) {
+    config_old.reset(new base::DictionaryValue());

[alexeypa (please no reviews), 2012/04/16 22:36:35]

I don't think we should allow to update a non-existing config. It will result in
invalid config anyway.

Also not ignoring the error from ReadConfig will allow to get rid of
CreateDirectory call below.

[simonmorris, 2012/04/16 23:20:23]

Done.

+  }
+  // Merge items from the given config into the old config.
+  config_old->MergeDictionary(config_dict);
+  // Write the updated config.
+  if (!file_util::CreateDirectory(config_dir)) {
+    return HRESULT_FROM_WIN32(ERROR_ACCESS_DENIED);
+  }
+  std::string config_updated_str;
+  base::JSONWriter::Write(config_old.get(), &config_updated_str);
+  return WriteConfig(config_dir.Append(kConfigFileName),
+                     config_updated_str.c_str(),
+                     config_updated_str.size());
 }
 
 HRESULT ElevatedControllerWin::OpenService(ScopedScHandle* service_out) {