cros-disks/fuse_mounter_test.cc

// Copyright 2019 The Chromium OS 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 "cros-disks/fuse_mounter.h"

#include <memory>
#include <string>
#include <vector>

#include <gmock/gmock.h>
#include <gtest/gtest.h>

#include "cros-disks/mount_options.h"
#include "cros-disks/platform.h"
#include "cros-disks/sandboxed_process.h"

namespace cros_disks {

namespace {

using testing::_;
using testing::ElementsAre;
using testing::Invoke;
using testing::Return;
using testing::StartsWith;

const uid_t kMountUID = 200;
const gid_t kMountGID = 201;
const uid_t kFilesUID = 700;
const uid_t kFilesGID = 701;
const uid_t kFilesAccessGID = 1501;
const char kMountUser[] = "fuse-fuse";
const char kFUSEType[] = "fuse";
const char kMountProgram[] = "dummy";
const char kSomeSource[] = "/some/src";
const char kMountDir[] = "/mnt";

// Mock Platform implementation for testing.
class MockFUSEPlatform : public Platform {
 public:
  MockFUSEPlatform() {
    ON_CALL(*this, GetUserAndGroupId(_, _, _))
        .WillByDefault(Invoke(this, &MockFUSEPlatform::GetUserAndGroupIdImpl));
    ON_CALL(*this, GetGroupId(_, _))
        .WillByDefault(Invoke(this, &MockFUSEPlatform::GetGroupIdImpl));
    ON_CALL(*this, PathExists(_)).WillByDefault(Return(true));
    ON_CALL(*this, SetOwnership(_, _, _)).WillByDefault(Return(true));
    ON_CALL(*this, SetPermissions(_, _)).WillByDefault(Return(true));
  }

  MOCK_CONST_METHOD3(GetUserAndGroupId,
                     bool(const std::string&, uid_t* user_id, gid_t* group_id));
  MOCK_CONST_METHOD2(GetGroupId, bool(const std::string&, gid_t* group_id));
  MOCK_CONST_METHOD5(Mount,
                     MountErrorType(const std::string&,
                                    const std::string&,
                                    const std::string&,
                                    uint64_t flags,
                                    const std::string&));
  MOCK_CONST_METHOD2(Unmount, MountErrorType(const std::string&, int flags));
  MOCK_CONST_METHOD1(PathExists, bool(const std::string& path));
  MOCK_CONST_METHOD3(SetOwnership,
                     bool(const std::string& path,
                          uid_t user_id,
                          gid_t group_id));
  MOCK_CONST_METHOD3(GetOwnership,
                     bool(const std::string& path,
                          uid_t* user_id,
                          gid_t* group_id));
  MOCK_CONST_METHOD2(SetPermissions,
                     bool(const std::string& path, mode_t mode));

 private:
  bool GetUserAndGroupIdImpl(const std::string& user,
                             uid_t* user_id,
                             gid_t* group_id) const {
    if (user == "chronos") {
      if (user_id)
        *user_id = kFilesUID;
      if (group_id)
        *group_id = kFilesGID;
      return true;
    }
    if (user == kMountUser) {
      if (user_id)
        *user_id = kMountUID;
      if (group_id)
        *group_id = kMountGID;
      return true;
    }
    return false;
  }

  bool GetGroupIdImpl(const std::string& group, gid_t* group_id) const {
    if (group == "chronos-access") {
      if (group_id)
        *group_id = kFilesAccessGID;
      return true;
    }
    return false;
  }
};

class MockSandboxedProcess : public SandboxedProcess {
 public:
  MockSandboxedProcess() = default;
  MOCK_METHOD0(Start, bool());
  MOCK_METHOD0(Wait, int());
};

class FUSEMounterForTesting : public FUSEMounter {
 public:
  FUSEMounterForTesting(const Platform* platform, bool unprivileged)
      : FUSEMounter(kSomeSource,
                    kMountDir,
                    kFUSEType,
                    MountOptions(),
                    platform,
                    kMountProgram,
                    kMountUser,
                    {},
                    {},
                    false,
                    unprivileged) {}

  MOCK_CONST_METHOD1(InvokeMountTool,
                     int(const std::vector<std::string>& args));

 private:
  std::unique_ptr<SandboxedProcess> CreateSandboxedProcess() const override {
    auto mock = std::make_unique<MockSandboxedProcess>();
    auto* raw_ptr = mock.get();
    ON_CALL(*mock, Start()).WillByDefault(Return(true));
    ON_CALL(*mock, Wait()).WillByDefault(Invoke([raw_ptr, this]() {
      return InvokeMountTool(raw_ptr->arguments());
    }));
    return mock;
  }
};

}  // namespace

TEST(FUSEMounterTest, Sandboxing) {
  MockFUSEPlatform platform;
  FUSEMounterForTesting mounter(&platform, false);
  EXPECT_CALL(mounter, InvokeMountTool(ElementsAre(kMountProgram, "-o",
                                                   MountOptions().ToString(),
                                                   kSomeSource, kMountDir)))
      .WillOnce(Return(0));

  // Expectations for sandbox setup.
  EXPECT_CALL(platform, Mount(_, _, _, _, _)).Times(0);
  EXPECT_CALL(platform, PathExists(kMountProgram)).WillOnce(Return(true));
  EXPECT_CALL(platform, PathExists(kSomeSource)).WillOnce(Return(true));

  EXPECT_CALL(platform, SetOwnership(kSomeSource, getuid(), kMountGID))
      .WillOnce(Return(true));
  EXPECT_CALL(platform, SetPermissions(kSomeSource,
                                       S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP))
      .WillOnce(Return(true));
  EXPECT_CALL(platform, SetOwnership(kMountDir, getuid(), kMountGID))
      .WillOnce(Return(true));
  EXPECT_CALL(platform, SetPermissions(kMountDir, S_IRWXU | S_IRWXG))
      .WillOnce(Return(true));

  EXPECT_EQ(MOUNT_ERROR_NONE, mounter.Mount());
}

TEST(FUSEMounterTest, Sandboxing_Unprivileged) {
  MockFUSEPlatform platform;
  FUSEMounterForTesting mounter(&platform, true);
  EXPECT_CALL(mounter, InvokeMountTool(ElementsAre(
                           kMountProgram, "-o", MountOptions().ToString(),
                           kSomeSource, StartsWith("/dev/fd/"))))
      .WillOnce(Return(0));

  // Expectations for sandbox setup.
  EXPECT_CALL(platform, Mount(kSomeSource, kMountDir, _, _, _))
      .WillOnce(Return(MOUNT_ERROR_NONE));

  EXPECT_CALL(platform, PathExists(kMountProgram)).WillOnce(Return(true));
  EXPECT_CALL(platform, PathExists(kSomeSource)).WillOnce(Return(true));
  EXPECT_CALL(platform, SetOwnership(kSomeSource, getuid(), kMountGID))
      .WillOnce(Return(true));
  EXPECT_CALL(platform, SetPermissions(kSomeSource,
                                       S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP))
      .WillOnce(Return(true));
  EXPECT_CALL(platform, SetOwnership(kMountDir, _, _)).Times(0);
  EXPECT_CALL(platform, SetPermissions(kMountDir, _)).Times(0);

  EXPECT_EQ(MOUNT_ERROR_NONE, mounter.Mount());
}

TEST(FUSEMounterTest, Sandboxing_PermissionDenied) {
  MockFUSEPlatform platform;
  FUSEMounterForTesting mounter(&platform, false);

  EXPECT_CALL(platform, SetOwnership(kMountDir, getuid(), kMountGID))
      .WillOnce(Return(false));
  EXPECT_CALL(mounter, InvokeMountTool(_)).Times(0);

  EXPECT_EQ(MOUNT_ERROR_INSUFFICIENT_PERMISSIONS, mounter.Mount());
}

TEST(FUSEMounterTest, AppFailed) {
  MockFUSEPlatform platform;
  FUSEMounterForTesting mounter(&platform, false);
  EXPECT_CALL(mounter, InvokeMountTool(_)).WillOnce(Return(1));

  EXPECT_EQ(MOUNT_ERROR_MOUNT_PROGRAM_FAILED, mounter.Mount());
}

}  // namespace cros_disks