| // Copyright (c) 2013 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 <fcntl.h> |
| #include <linux/capability.h> |
| #include <linux/fs.h> |
| #include <sys/ioctl.h> |
| #include <sys/stat.h> |
| #include <sys/types.h> |
| #include <unistd.h> |
| |
| #include <memory> |
| #include <string> |
| #include <utility> |
| |
| #include <base/macros.h> |
| #include <base/bind.h> |
| #include <base/callback_helpers.h> |
| #include <base/files/file.h> |
| #include <base/logging.h> |
| #include <base/strings/stringprintf.h> |
| #include <base/strings/string_util.h> |
| #include <brillo/process_reaper.h> |
| |
| #include "cros-disks/error_logger.h" |
| #include "cros-disks/platform.h" |
| #include "cros-disks/quote.h" |
| #include "cros-disks/sandboxed_process.h" |
| |
| namespace cros_disks { |
| |
| namespace { |
| |
| const mode_t kSourcePathPermissions = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP; |
| |
| const char kFuseDeviceFile[] = "/dev/fuse"; |
| const MountOptions::Flags kRequiredFuseMountFlags = |
| MS_NODEV | MS_NOEXEC | MS_NOSUID; |
| |
| void CleanUpCallback(base::OnceClosure cleanup, |
| const base::FilePath& mount_path, |
| const siginfo_t& info) { |
| CHECK_EQ(SIGCHLD, info.si_signo); |
| if (info.si_code != CLD_EXITED || info.si_status != 0) { |
| LOG(WARNING) << "FUSE daemon for " << quote(mount_path) |
| << " exited with code " << info.si_code << " and status " |
| << info.si_status; |
| } else { |
| LOG(INFO) << "FUSE daemon for " << quote(mount_path) << " exited normally"; |
| } |
| std::move(cleanup).Run(); |
| } |
| |
| MountErrorType ConfigureCommonSandbox(SandboxedProcess* sandbox, |
| const Platform* platform, |
| bool network_ns, |
| const base::FilePath& seccomp) { |
| sandbox->SetCapabilities(0); |
| sandbox->SetNoNewPrivileges(); |
| |
| // The FUSE mount program is put under a new mount namespace, so mounts |
| // inside that namespace don't normally propagate. |
| sandbox->NewMountNamespace(); |
| |
| // TODO(crbug.com/707327): Remove this when we get rid of AVFS. |
| sandbox->SkipRemountPrivate(); |
| |
| // TODO(benchan): Re-enable cgroup namespace when either Chrome OS |
| // kernel 3.8 supports it or no more supported devices use kernel |
| // 3.8. |
| // mount_process.NewCgroupNamespace(); |
| |
| sandbox->NewIpcNamespace(); |
| |
| sandbox->NewPidNamespace(); |
| |
| if (network_ns) { |
| sandbox->NewNetworkNamespace(); |
| } |
| |
| if (!seccomp.empty()) { |
| if (!platform->PathExists(seccomp.value())) { |
| LOG(ERROR) << "Seccomp policy " << quote(seccomp) << " is missing"; |
| return MOUNT_ERROR_INTERNAL; |
| } |
| sandbox->LoadSeccompFilterPolicy(seccomp.value()); |
| } |
| |
| // Prepare mounts for pivot_root. |
| if (!sandbox->SetUpMinimalMounts()) { |
| LOG(ERROR) << "Can't set up minijail mounts"; |
| return MOUNT_ERROR_INTERNAL; |
| } |
| |
| // Data dirs if any are mounted inside /run/fuse. |
| if (!sandbox->Mount("tmpfs", "/run", "tmpfs", "mode=0755,size=10M")) { |
| LOG(ERROR) << "Can't mount /run"; |
| return MOUNT_ERROR_INTERNAL; |
| } |
| if (!sandbox->BindMount("/run/fuse", "/run/fuse", false, false)) { |
| LOG(ERROR) << "Can't bind /run/fuse"; |
| return MOUNT_ERROR_INTERNAL; |
| } |
| |
| if (!network_ns) { |
| // Network DNS configs are in /run/shill. |
| if (!sandbox->BindMount("/run/shill", "/run/shill", false, false)) { |
| LOG(ERROR) << "Can't bind /run/shill"; |
| return MOUNT_ERROR_INTERNAL; |
| } |
| // Hardcoded hosts are mounted into /etc/hosts.d when Crostini is enabled. |
| if (platform->PathExists("/etc/hosts.d") && |
| !sandbox->BindMount("/etc/hosts.d", "/etc/hosts.d", false, false)) { |
| LOG(ERROR) << "Can't bind /etc/hosts.d"; |
| return MOUNT_ERROR_INTERNAL; |
| } |
| } |
| if (!sandbox->EnterPivotRoot()) { |
| LOG(ERROR) << "Can't pivot root"; |
| return MOUNT_ERROR_INTERNAL; |
| } |
| |
| return MOUNT_ERROR_NONE; |
| } |
| |
| bool GetPhysicalBlockSize(const std::string& source, int* size) { |
| base::ScopedFD fd(open(source.c_str(), O_RDONLY | O_CLOEXEC)); |
| |
| *size = 0; |
| if (!fd.is_valid()) { |
| PLOG(WARNING) << "Couldn't open " << source; |
| return false; |
| } |
| |
| if (ioctl(fd.get(), BLKPBSZGET, size) < 0) { |
| PLOG(WARNING) << "Failed to get block size for" << source; |
| return false; |
| } |
| |
| return true; |
| } |
| |
| MountErrorType MountFuseDevice(const Platform* platform, |
| const std::string& source, |
| const std::string& filesystem_type, |
| const base::FilePath& target, |
| const base::File& fuse_file, |
| uid_t mount_user_id, |
| gid_t mount_group_id, |
| const MountOptions& options) { |
| // Mount options for FUSE: |
| // fd - File descriptor for /dev/fuse. |
| // user_id/group_id - user/group for file access control. Essentially |
| // bypassed due to allow_other, but still required to be set. |
| // allow_other - Allows users other than user_id/group_id to access files |
| // on the file system. By default, FUSE prevents any process other than |
| // ones running under user_id/group_id to access files, regardless of |
| // the file's permissions. |
| // default_permissions - Enforce permission checking. |
| // rootmode - Mode bits for the root inode. |
| std::string fuse_mount_options = base::StringPrintf( |
| "fd=%d,user_id=%u,group_id=%u,allow_other,default_permissions," |
| "rootmode=%o", |
| fuse_file.GetPlatformFile(), mount_user_id, mount_group_id, S_IFDIR); |
| |
| // "nosymfollow" is a special mount option that's passed to the Chromium LSM |
| // and not forwarded to the FUSE driver. If it's set, add it as a mount |
| // option. |
| if (options.HasOption(MountOptions::kOptionNoSymFollow)) { |
| fuse_mount_options.append(","); |
| fuse_mount_options.append(MountOptions::kOptionNoSymFollow); |
| } |
| |
| std::string fuse_type = "fuse"; |
| struct stat statbuf = {0}; |
| if (stat(source.c_str(), &statbuf) == 0 && S_ISBLK(statbuf.st_mode)) { |
| int blksize = 0; |
| |
| // TODO(crbug.com/931500): It's possible that specifying a block size equal |
| // to the file system cluster size (which might be larger than the physical |
| // block size) might be more efficient. Data would be needed to see what |
| // kind of performance benefit, if any, could be gained. At the very least, |
| // specify the block size of the underlying device. Without this, UFS cards |
| // with 4k sector size will fail to mount. |
| if (GetPhysicalBlockSize(source, &blksize) && blksize > 0) |
| fuse_mount_options.append(base::StringPrintf(",blksize=%d", blksize)); |
| |
| LOG(INFO) << "Source file " << quote(source) |
| << " is a block device with block size " << blksize; |
| |
| fuse_type = "fuseblk"; |
| } |
| if (!filesystem_type.empty()) { |
| fuse_type += "."; |
| fuse_type += filesystem_type; |
| } |
| |
| auto flags = options.ToMountFlagsAndData().first; |
| |
| return platform->Mount(source.empty() ? filesystem_type : source, |
| target.value(), fuse_type, |
| flags | kRequiredFuseMountFlags, fuse_mount_options); |
| } |
| |
| } // namespace |
| |
| FUSEMounter::FUSEMounter(const std::string& source_path, |
| const std::string& target_path, |
| const std::string& filesystem_type, |
| const MountOptions& mount_options, |
| const Platform* platform, |
| brillo::ProcessReaper* process_reaper, |
| const std::string& mount_program_path, |
| const std::string& mount_user, |
| const std::string& seccomp_policy, |
| const std::vector<BindPath>& accessible_paths, |
| bool permit_network_access, |
| const std::string& mount_group) |
| : MounterCompat(filesystem_type, |
| source_path, |
| base::FilePath(target_path), |
| mount_options), |
| platform_(platform), |
| process_reaper_(process_reaper), |
| mount_program_path_(mount_program_path), |
| mount_user_(mount_user), |
| mount_group_(mount_group), |
| seccomp_policy_(seccomp_policy), |
| accessible_paths_(accessible_paths), |
| permit_network_access_(permit_network_access) {} |
| |
| MountErrorType FUSEMounter::MountImpl() const { |
| auto mount_process = CreateSandboxedProcess(); |
| MountErrorType error = ConfigureCommonSandbox( |
| mount_process.get(), platform_, !permit_network_access_, |
| base::FilePath(seccomp_policy_)); |
| if (error != MOUNT_ERROR_NONE) { |
| return error; |
| } |
| |
| uid_t mount_user_id; |
| gid_t mount_group_id; |
| if (!platform_->GetUserAndGroupId(mount_user_, &mount_user_id, |
| &mount_group_id)) { |
| LOG(ERROR) << "Cannot resolve user " << quote(mount_user_); |
| return MOUNT_ERROR_INTERNAL; |
| } |
| if (!mount_group_.empty() && |
| !platform_->GetGroupId(mount_group_, &mount_group_id)) { |
| return MOUNT_ERROR_INTERNAL; |
| } |
| |
| mount_process->SetUserId(mount_user_id); |
| mount_process->SetGroupId(mount_group_id); |
| |
| if (!platform_->PathExists(mount_program_path_)) { |
| LOG(ERROR) << "Cannot find mount program " << quote(mount_program_path_); |
| return MOUNT_ERROR_MOUNT_PROGRAM_NOT_FOUND; |
| } |
| mount_process->AddArgument(mount_program_path_); |
| |
| const base::File fuse_file = base::File( |
| base::FilePath(kFuseDeviceFile), |
| base::File::FLAG_OPEN | base::File::FLAG_READ | base::File::FLAG_WRITE); |
| if (!fuse_file.IsValid()) { |
| LOG(ERROR) << "Unable to open FUSE device file. Error: " |
| << fuse_file.error_details() << " " |
| << base::File::ErrorToString(fuse_file.error_details()); |
| return MOUNT_ERROR_INTERNAL; |
| } |
| |
| error = MountFuseDevice(platform_, source(), filesystem_type(), |
| base::FilePath(target_path()), fuse_file, |
| mount_user_id, mount_group_id, mount_options()); |
| if (error != MOUNT_ERROR_NONE) { |
| LOG(ERROR) << "Can't perform unprivileged FUSE mount: " << error; |
| return error; |
| } |
| |
| // The |fuse_failure_unmounter| closure runner is used to unmount the FUSE |
| // filesystem if any part of starting the FUSE helper process fails. |
| // TODO(crbug.com/993857): Use base::BindOnce(). |
| base::ScopedClosureRunner fuse_cleanup_runner(base::Bind( |
| [](const Platform* platform, const std::string& target_path) { |
| if (!platform->DirectoryExists(target_path)) { |
| // If the mount directory doesn't exist, don't try to unmount and |
| // remove it. This will happen when the browser requests to unmount |
| // the filesystem. In this case, both the following operations are |
| // unnecessary and will fail, resulting in log spam. |
| return; |
| } |
| |
| MountErrorType unmount_error = platform->Unmount(target_path, 0); |
| LOG_IF(ERROR, unmount_error != MOUNT_ERROR_NONE) |
| << "Cannot unmount FUSE mount point " << quote(target_path) << ": " |
| << unmount_error; |
| |
| if (!platform->RemoveEmptyDirectory(target_path)) { |
| PLOG(ERROR) << "Cannot remove FUSE mount point " |
| << quote(target_path); |
| } |
| }, |
| platform_, target_path().value())); |
| |
| // Source might be an URI. Only try to re-own source if it looks like |
| // an existing path. |
| if (!source().empty() && platform_->PathExists(source())) { |
| if (!platform_->SetOwnership(source(), getuid(), mount_group_id) || |
| !platform_->SetPermissions(source(), kSourcePathPermissions)) { |
| LOG(ERROR) << "Can't set up permissions on the source"; |
| return MOUNT_ERROR_INSUFFICIENT_PERMISSIONS; |
| } |
| } |
| |
| // If a block device is being mounted, bind mount it into the sandbox. |
| if (base::StartsWith(source(), "/dev/", base::CompareCase::SENSITIVE)) { |
| if (!mount_process->BindMount(source(), source(), true, false)) { |
| LOG(ERROR) << "Cannot bind mount device " << quote(source()); |
| return MOUNT_ERROR_INVALID_ARGUMENT; |
| } |
| } |
| |
| // TODO(crbug.com/933018): Remove when DriveFS helper is refactored. |
| if (!mount_process->Mount("tmpfs", "/home", "tmpfs", "mode=0755,size=10M")) { |
| LOG(ERROR) << "Can't mount /home"; |
| return MOUNT_ERROR_INTERNAL; |
| } |
| |
| // This is for additional data dirs. |
| for (const auto& path : accessible_paths_) { |
| if (!mount_process->BindMount(path.path, path.path, path.writable, |
| path.recursive)) { |
| LOG(ERROR) << "Can't bind " << path.path; |
| return MOUNT_ERROR_INVALID_ARGUMENT; |
| } |
| } |
| |
| std::string options_string = mount_options().ToString(); |
| if (!options_string.empty()) { |
| mount_process->AddArgument("-o"); |
| mount_process->AddArgument(options_string); |
| } |
| if (!source().empty()) { |
| mount_process->AddArgument(source()); |
| } |
| mount_process->AddArgument( |
| base::StringPrintf("/dev/fd/%d", fuse_file.GetPlatformFile())); |
| |
| std::vector<std::string> output; |
| int return_code = mount_process->Run(&output); |
| if (return_code != 0) { |
| LOG(ERROR) << "FUSE mount program failed with return code " << return_code; |
| if (!output.empty()) { |
| LOG(ERROR) << "FUSE mount program outputted " << output.size() |
| << " lines:"; |
| for (const std::string& line : output) { |
| LOG(ERROR) << line; |
| } |
| } |
| return MOUNT_ERROR_MOUNT_PROGRAM_FAILED; |
| } |
| |
| // At this point, the FUSE daemon has successfully started, so repurpose |
| // the FUSE cleanup closure runner to run on daemon quitting. |
| // This is defined as in-jail "init" process, denoted by pid(), |
| // terminates, which happens only when the last process in the jailed PID |
| // namespace terminates. |
| process_reaper_->WatchForChild( |
| FROM_HERE, mount_process->pid(), |
| base::BindOnce(CleanUpCallback, fuse_cleanup_runner.Release(), |
| target_path())); |
| |
| return MOUNT_ERROR_NONE; |
| } |
| |
| std::unique_ptr<SandboxedProcess> FUSEMounter::CreateSandboxedProcess() const { |
| return std::make_unique<SandboxedProcess>(); |
| } |
| |
| } // namespace cros_disks |
