Export a D-Bus service used to bootstrap Mojo IPC for SmbFs.

When mounting SmbFs through cros-disks, there is currently no ability to
pass a file descriptor (eg. for a socket) over the D-Bus Mount() method.
Instead, a random string is generated and provided to SmbFs as part of
the mount source path. SmbFs will then generate a socket pair and pass
one end back to Chrome, along with the random string as an identifier,
through this D-Bus service.

This service is an exact duplicate of org.chromium.DriveFileStream.

Bug: 939235
Change-Id: Ideaec725a50ab7a1dba6e11b152fb08280c3a75b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1890378Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Commit-Queue: Anand Mistry <amistry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714124}

chrome/browser/chromeos/BUILD.gn

@@ -884,6 +884,8 @@ source_set("chromeos") {
     "dbus/proxy_resolution_service_provider.h",
     "dbus/screen_lock_service_provider.cc",
     "dbus/screen_lock_service_provider.h",
+    "dbus/smb_fs_service_provider.cc",
+    "dbus/smb_fs_service_provider.h",
     "dbus/virtual_file_request_service_provider.cc",
     "dbus/virtual_file_request_service_provider.h",
     "dbus/vm_applications_service_provider.cc",
@@ -2354,6 +2356,7 @@ action("dbus_service_files") {
     "dbus/org.chromium.NetworkProxyService.conf",
     "dbus/org.chromium.PluginVmService.conf",
     "dbus/org.chromium.ScreenLockService.conf",
+    "dbus/org.chromium.SmbFsService.conf",
     "dbus/org.chromium.VirtualFileRequestService.conf",
     "dbus/org.chromium.VmApplicationsService.conf",
   ]

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

@@ -57,6 +57,7 @@
 #include "chrome/browser/chromeos/dbus/plugin_vm_service_provider.h"
 #include "chrome/browser/chromeos/dbus/proxy_resolution_service_provider.h"
 #include "chrome/browser/chromeos/dbus/screen_lock_service_provider.h"
+#include "chrome/browser/chromeos/dbus/smb_fs_service_provider.h"
 #include "chrome/browser/chromeos/dbus/virtual_file_request_service_provider.h"
 #include "chrome/browser/chromeos/dbus/vm_applications_service_provider.h"
 #include "chrome/browser/chromeos/display/quirks_manager_delegate_impl.h"
@@ -315,6 +316,12 @@ class DBusServices {
         CrosDBusService::CreateServiceProviderList(
             std::make_unique<CryptohomeKeyDelegateServiceProvider>()));
 
+    smb_fs_service_ =
+        CrosDBusService::Create(system_bus, smbfs::kSmbFsServiceName,
+                                dbus::ObjectPath(smbfs::kSmbFsServicePath),
+                                CrosDBusService::CreateServiceProviderList(
+                                    std::make_unique<SmbFsServiceProvider>()));
+
     if (arc::IsArcVmEnabled()) {
       libvda_service_ = CrosDBusService::Create(
           system_bus, libvda::kLibvdaServiceName,
@@ -401,6 +408,7 @@ class DBusServices {
   std::unique_ptr<CrosDBusService> cryptohome_key_delegate_service_;
   std::unique_ptr<CrosDBusService> libvda_service_;
   std::unique_ptr<CrosDBusService> machine_learning_decision_service_;
+  std::unique_ptr<CrosDBusService> smb_fs_service_;
 
   DISALLOW_COPY_AND_ASSIGN(DBusServices);
 };

chrome/browser/chromeos/dbus/org.chromium.SmbFsService.conf

+<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
+  "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
+<!--
+  Copyright 2019 The Chromium Authors. All rights reserved.
+  Use of this source code is governed by a BSD-style license that can be
+  found in the LICENSE file.
+-->
+<busconfig>
+  <policy user="chronos">
+    <allow own="org.chromium.SmbFs"/>
+  </policy>
+
+  <policy user="fuse-smbfs">
+    <allow send_destination="org.chromium.SmbFs"
+           send_interface="org.chromium.SmbFs"/>
+  </policy>
+</busconfig>

chrome/browser/chromeos/dbus/smb_fs_service_provider.cc

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/chromeos/dbus/smb_fs_service_provider.h"
+
+#include <string>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/files/scoped_file.h"
+#include "base/logging.h"
+#include "chromeos/components/mojo_bootstrap/pending_connection_manager.h"
+#include "dbus/message.h"
+#include "third_party/cros_system_api/dbus/service_constants.h"
+
+namespace chromeos {
+
+SmbFsServiceProvider::SmbFsServiceProvider() = default;
+
+SmbFsServiceProvider::~SmbFsServiceProvider() = default;
+
+void SmbFsServiceProvider::Start(
+    scoped_refptr<dbus::ExportedObject> exported_object) {
+  exported_object->ExportMethod(
+      smbfs::kSmbFsInterface, smbfs::kOpenIpcChannelMethod,
+      base::BindRepeating(&SmbFsServiceProvider::HandleOpenIpcChannel,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::BindRepeating([](const std::string& interface_name,
+                             const std::string& method_name, bool success) {
+        LOG_IF(ERROR, !success)
+            << "Failed to export " << interface_name << "." << method_name;
+      }));
+}
+
+void SmbFsServiceProvider::HandleOpenIpcChannel(
+    dbus::MethodCall* method_call,
+    dbus::ExportedObject::ResponseSender response_sender) {
+  std::string id;
+  base::ScopedFD fd;
+  dbus::MessageReader reader(method_call);
+  if (!reader.PopString(&id)) {
+    response_sender.Run(dbus::ErrorResponse::FromMethodCall(
+        method_call, DBUS_ERROR_INVALID_ARGS, "First argument is not string."));
+    return;
+  }
+  if (!reader.PopFileDescriptor(&fd)) {
+    response_sender.Run(dbus::ErrorResponse::FromMethodCall(
+        method_call, DBUS_ERROR_INVALID_ARGS, "Second argument is not FD."));
+    return;
+  }
+  if (!mojo_bootstrap::PendingConnectionManager::Get().OpenIpcChannel(
+          id, std::move(fd))) {
+    response_sender.Run(dbus::ErrorResponse::FromMethodCall(
+        method_call, DBUS_ERROR_FAILED, "Failed to open IPC"));
+    return;
+  }
+  response_sender.Run(dbus::Response::FromMethodCall(method_call));
+}
+
+}  // namespace chromeos

chrome/browser/chromeos/dbus/smb_fs_service_provider.h

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_CHROMEOS_DBUS_SMB_FS_SERVICE_PROVIDER_H_
+#define CHROME_BROWSER_CHROMEOS_DBUS_SMB_FS_SERVICE_PROVIDER_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "chromeos/dbus/services/cros_dbus_service.h"
+#include "dbus/exported_object.h"
+
+namespace dbus {
+class MethodCall;
+}
+
+namespace chromeos {
+
+// SmbFsServiceProvider exposes a D-Bus method which is used by instances of
+// SmbFs to bootstrap a Mojo IPC connection. The method by which SmbFs is
+// started cannot be passed a file descriptor, therefore this D-Bus method is
+// used to asynchronously associate a FD with an identified SmbFs instance.
+class SmbFsServiceProvider : public CrosDBusService::ServiceProviderInterface {
+ public:
+  SmbFsServiceProvider();
+  ~SmbFsServiceProvider() override;
+
+  // CrosDBusService::ServiceProviderInterface overrides:
+  void Start(scoped_refptr<dbus::ExportedObject> exported_object) override;
+
+ private:
+  // Handler for the OpenIpcChannel() D-Bus method.
+  void HandleOpenIpcChannel(
+      dbus::MethodCall* method_call,
+      dbus::ExportedObject::ResponseSender response_sender);
+
+  base::WeakPtrFactory<SmbFsServiceProvider> weak_ptr_factory_{this};
+
+  DISALLOW_COPY_AND_ASSIGN(SmbFsServiceProvider);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_DBUS_SMB_FS_SERVICE_PROVIDER_H_