path: root/pkg/sentry/vfs/options.go

// Copyright 2019 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package vfs

import (
	"gvisor.dev/gvisor/pkg/abi/linux"
	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
)

// GetDentryOptions contains options to VirtualFilesystem.GetDentryAt() and
// FilesystemImpl.GetDentryAt().
type GetDentryOptions struct {
	// If CheckSearchable is true, FilesystemImpl.GetDentryAt() must check that
	// the returned Dentry is a directory for which creds has search
	// permission.
	CheckSearchable bool
}

// MkdirOptions contains options to VirtualFilesystem.MkdirAt() and
// FilesystemImpl.MkdirAt().
type MkdirOptions struct {
	// Mode is the file mode bits for the created directory.
	Mode linux.FileMode

	// If ForSyntheticMountpoint is true, FilesystemImpl.MkdirAt() may create
	// the given directory in memory only (as opposed to persistent storage).
	// The created directory should be able to support the creation of
	// subdirectories with ForSyntheticMountpoint == true. It does not need to
	// support the creation of subdirectories with ForSyntheticMountpoint ==
	// false, or files of other types.
	//
	// FilesystemImpls are permitted to ignore the ForSyntheticMountpoint
	// option.
	//
	// The ForSyntheticMountpoint option exists because, unlike mount(2), the
	// OCI Runtime Specification permits the specification of mount points that
	// do not exist, under the expectation that container runtimes will create
	// them. (More accurately, the OCI Runtime Specification completely fails
	// to document this feature, but it's implemented by runc.)
	// ForSyntheticMountpoint allows such mount points to be created even when
	// the underlying persistent filesystem is immutable.
	ForSyntheticMountpoint bool
}

// MknodOptions contains options to VirtualFilesystem.MknodAt() and
// FilesystemImpl.MknodAt().
type MknodOptions struct {
	// Mode is the file type and mode bits for the created file.
	Mode linux.FileMode

	// If Mode specifies a character or block device special file, DevMajor and
	// DevMinor are the major and minor device numbers for the created device.
	DevMajor uint32
	DevMinor uint32

	// Endpoint is the endpoint to bind to the created file, if a socket file is
	// being created for bind(2) on a Unix domain socket.
	Endpoint transport.BoundEndpoint
}

// MountFlags contains flags as specified for mount(2), e.g. MS_NOEXEC.
// MS_RDONLY is not part of MountFlags because it's tracked in Mount.writers.
type MountFlags struct {
	// NoExec is equivalent to MS_NOEXEC.
	NoExec bool

	// NoATime is equivalent to MS_NOATIME and indicates that the
	// filesystem should not update access time in-place.
	NoATime bool

	// NoDev is equivalent to MS_NODEV and indicates that the
	// filesystem should not allow access to devices (special files).
	// TODO(gVisor.dev/issue/3186): respect this flag in non FUSE
	// filesystems.
	NoDev bool

	// NoSUID is equivalent to MS_NOSUID and indicates that the
	// filesystem should not honor set-user-ID and set-group-ID bits or
	// file capabilities when executing programs.
	NoSUID bool
}

// MountOptions contains options to VirtualFilesystem.MountAt().
type MountOptions struct {
	// Flags contains flags as specified for mount(2), e.g. MS_NOEXEC.
	Flags MountFlags

	// ReadOnly is equivalent to MS_RDONLY.
	ReadOnly bool

	// GetFilesystemOptions contains options to FilesystemType.GetFilesystem().
	GetFilesystemOptions GetFilesystemOptions

	// If InternalMount is true, allow the use of filesystem types for which
	// RegisterFilesystemTypeOptions.AllowUserMount == false.
	InternalMount bool
}

// OpenOptions contains options to VirtualFilesystem.OpenAt() and
// FilesystemImpl.OpenAt().
type OpenOptions struct {
	// Flags contains access mode and flags as specified for open(2).
	//
	// FilesystemImpls are responsible for implementing the following flags:
	// O_RDONLY, O_WRONLY, O_RDWR, O_APPEND, O_CREAT, O_DIRECT, O_DSYNC,
	// O_EXCL, O_NOATIME, O_NOCTTY, O_NONBLOCK, O_PATH, O_SYNC, O_TMPFILE, and
	// O_TRUNC. VFS is responsible for handling O_DIRECTORY, O_LARGEFILE, and
	// O_NOFOLLOW. VFS users are responsible for handling O_CLOEXEC, since file
	// descriptors are mostly outside the scope of VFS.
	Flags uint32

	// If FilesystemImpl.OpenAt() creates a file, Mode is the file mode for the
	// created file.
	Mode linux.FileMode

	// FileExec is set when the file is being opened to be executed.
	// VirtualFilesystem.OpenAt() checks that the caller has execute permissions
	// on the file, that the file is a regular file, and that the mount doesn't
	// have MS_NOEXEC set.
	FileExec bool
}

// ReadOptions contains options to FileDescription.PRead(),
// FileDescriptionImpl.PRead(), FileDescription.Read(), and
// FileDescriptionImpl.Read().
type ReadOptions struct {
	// Flags contains flags as specified for preadv2(2).
	Flags uint32
}

// RenameOptions contains options to VirtualFilesystem.RenameAt() and
// FilesystemImpl.RenameAt().
type RenameOptions struct {
	// Flags contains flags as specified for renameat2(2).
	Flags uint32

	// If MustBeDir is true, the renamed file must be a directory.
	MustBeDir bool
}

// SetStatOptions contains options to VirtualFilesystem.SetStatAt(),
// FilesystemImpl.SetStatAt(), FileDescription.SetStat(), and
// FileDescriptionImpl.SetStat().
type SetStatOptions struct {
	// Stat is the metadata that should be set. Only fields indicated by
	// Stat.Mask should be set.
	//
	// If Stat specifies that a timestamp should be set,
	// FilesystemImpl.SetStatAt() and FileDescriptionImpl.SetStat() must
	// special-case StatxTimestamp.Nsec == UTIME_NOW as described by
	// utimensat(2); however, they do not need to check for StatxTimestamp.Nsec
	// == UTIME_OMIT (VFS users must unset the corresponding bit in Stat.Mask
	// instead).
	Stat linux.Statx

	// NeedWritePerm indicates that write permission on the file is needed for
	// this operation. This is needed for truncate(2) (note that ftruncate(2)
	// does not require the same check--instead, it checks that the fd is
	// writable).
	NeedWritePerm bool
}

// BoundEndpointOptions contains options to VirtualFilesystem.BoundEndpointAt()
// and FilesystemImpl.BoundEndpointAt().
type BoundEndpointOptions struct {
	// Addr is the path of the file whose socket endpoint is being retrieved.
	// It is generally irrelevant: most endpoints are stored at a dentry that
	// was created through a bind syscall, so the path can be stored on creation.
	// However, if the endpoint was created in FilesystemImpl.BoundEndpointAt(),
	// then we may not know what the original bind address was.
	//
	// For example, if connect(2) is called with address "foo" which corresponds
	// a remote named socket in goferfs, we need to generate an endpoint wrapping
	// that file. In this case, we can use Addr to set the endpoint address to
	// "foo". Note that Addr is only a best-effort attempt--we still do not know
	// the exact address that was used on the remote fs to bind the socket (it
	// may have been "foo", "./foo", etc.).
	Addr string
}

// GetXattrOptions contains options to VirtualFilesystem.GetXattrAt(),
// FilesystemImpl.GetXattrAt(), FileDescription.GetXattr(), and
// FileDescriptionImpl.GetXattr().
type GetXattrOptions struct {
	// Name is the name of the extended attribute to retrieve.
	Name string

	// Size is the maximum value size that the caller will tolerate. If the value
	// is larger than size, getxattr methods may return ERANGE, but they are also
	// free to ignore the hint entirely (i.e. the value returned may be larger
	// than size). All size checking is done independently at the syscall layer.
	Size uint64
}

// SetXattrOptions contains options to VirtualFilesystem.SetXattrAt(),
// FilesystemImpl.SetXattrAt(), FileDescription.SetXattr(), and
// FileDescriptionImpl.SetXattr().
type SetXattrOptions struct {
	// Name is the name of the extended attribute being mutated.
	Name string

	// Value is the extended attribute's new value.
	Value string

	// Flags contains flags as specified for setxattr/lsetxattr/fsetxattr(2).
	Flags uint32
}

// StatOptions contains options to VirtualFilesystem.StatAt(),
// FilesystemImpl.StatAt(), FileDescription.Stat(), and
// FileDescriptionImpl.Stat().
type StatOptions struct {
	// Mask is the set of fields in the returned Statx that the FilesystemImpl
	// or FileDescriptionImpl should provide. Bits are as in linux.Statx.Mask.
	//
	// The FilesystemImpl or FileDescriptionImpl may return fields not
	// requested in Mask, and may fail to return fields requested in Mask that
	// are not supported by the underlying filesystem implementation, without
	// returning an error.
	Mask uint32

	// Sync specifies the synchronization required, and is one of
	// linux.AT_STATX_SYNC_AS_STAT (which is 0, and therefore the default),
	// linux.AT_STATX_SYNC_FORCE_SYNC, or linux.AT_STATX_SYNC_DONT_SYNC.
	Sync uint32
}

// UmountOptions contains options to VirtualFilesystem.UmountAt().
type UmountOptions struct {
	// Flags contains flags as specified for umount2(2).
	Flags uint32
}

// WriteOptions contains options to FileDescription.PWrite(),
// FileDescriptionImpl.PWrite(), FileDescription.Write(), and
// FileDescriptionImpl.Write().
type WriteOptions struct {
	// Flags contains flags as specified for pwritev2(2).
	Flags uint32
}