Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 382 insertions, 0 deletions

diff --git a/pkg/sentry/fs/attr.go b/pkg/sentry/fs/attr.go
new file mode 100644
index 000000000..56a2ad6f7
--- /dev/null
+++ b/pkg/sentry/fs/attr.go
@@ -0,0 +1,382 @@
+// Copyright 2018 Google Inc.
+//
+// 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 fs
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/p9"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
+	ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
+)
+
+// InodeType enumerates types of Inodes.
+type InodeType int
+
+const (
+	// RegularFile is a regular file.
+	RegularFile InodeType = iota
+
+	// SpecialFile is a file that doesn't support SeekEnd. It is used for
+	// things like proc files.
+	SpecialFile
+
+	// Directory is a directory.
+	Directory
+
+	// SpecialDirectory is a directory that *does* support SeekEnd. It's
+	// the opposite of the SpecialFile scenario above. It similarly
+	// supports proc files.
+	SpecialDirectory
+
+	// Symlink is a symbolic link.
+	Symlink
+
+	// Pipe is a pipe (named or regular).
+	Pipe
+
+	// Socket is a socket.
+	Socket
+
+	// CharacterDevice is a character device.
+	CharacterDevice
+
+	// BlockDevice is a block device.
+	BlockDevice
+
+	// Anonymous is an anonymous type when none of the above apply.
+	// Epoll fds and event-driven fds fit this category.
+	Anonymous
+)
+
+// String returns a human-readable representation of the InodeType.
+func (n InodeType) String() string {
+	switch n {
+	case RegularFile, SpecialFile:
+		return "file"
+	case Directory, SpecialDirectory:
+		return "directory"
+	case Symlink:
+		return "symlink"
+	case Pipe:
+		return "pipe"
+	case Socket:
+		return "socket"
+	case CharacterDevice:
+		return "character-device"
+	case BlockDevice:
+		return "block-device"
+	case Anonymous:
+		return "anonymous"
+	default:
+		return "unknown"
+	}
+}
+
+// StableAttr contains Inode attributes that will be stable throughout the
+// lifetime of the Inode.
+type StableAttr struct {
+	// Type is the InodeType of a InodeOperations.
+	Type InodeType
+
+	// DeviceID is the device on which a InodeOperations resides.
+	DeviceID uint64
+
+	// InodeID uniquely identifies InodeOperations on its device.
+	InodeID uint64
+
+	// BlockSize is the block size of data backing this InodeOperations.
+	BlockSize int64
+
+	// DeviceFileMajor is the major device number of this Node, if it is a
+	// device file.
+	DeviceFileMajor uint16
+
+	// DeviceFileMinor is the minor device number of this Node, if it is a
+	// device file.
+	DeviceFileMinor uint32
+}
+
+// IsRegular returns true if StableAttr.Type matches a regular file.
+func IsRegular(s StableAttr) bool {
+	return s.Type == RegularFile
+}
+
+// IsFile returns true if StableAttr.Type matches any type of file.
+func IsFile(s StableAttr) bool {
+	return s.Type == RegularFile || s.Type == SpecialFile
+}
+
+// IsDir returns true if StableAttr.Type matches any type of directory.
+func IsDir(s StableAttr) bool {
+	return s.Type == Directory || s.Type == SpecialDirectory
+}
+
+// IsSymlink returns true if StableAttr.Type matches a symlink.
+func IsSymlink(s StableAttr) bool {
+	return s.Type == Symlink
+}
+
+// IsPipe returns true if StableAttr.Type matches any type of pipe.
+func IsPipe(s StableAttr) bool {
+	return s.Type == Pipe
+}
+
+// IsSocket returns true if StableAttr.Type matches any type of socket.
+func IsSocket(s StableAttr) bool {
+	return s.Type == Socket
+}
+
+// IsCharDevice returns true if StableAttr.Type matches a character device.
+func IsCharDevice(s StableAttr) bool {
+	return s.Type == CharacterDevice
+}
+
+// UnstableAttr contains Inode attributes that may change over the lifetime
+// of the Inode.
+type UnstableAttr struct {
+	// Size is the file size in bytes.
+	Size int64
+
+	// Usage is the actual data usage in bytes.
+	Usage int64
+
+	// Perms is the protection (read/write/execute for user/group/other).
+	Perms FilePermissions
+
+	// Owner describes the ownership of this file.
+	Owner FileOwner
+
+	// AccessTime is the time of last access
+	AccessTime ktime.Time
+
+	// ModificationTime is the time of last modification.
+	ModificationTime ktime.Time
+
+	// StatusChangeTime is the time of last attribute modification.
+	StatusChangeTime ktime.Time
+
+	// Links is the number of hard links.
+	Links uint64
+}
+
+// WithCurrentTime returns u with AccessTime == ModificationTime == current time.
+func WithCurrentTime(ctx context.Context, u UnstableAttr) UnstableAttr {
+	t := ktime.NowFromContext(ctx)
+	u.AccessTime = t
+	u.ModificationTime = t
+	u.StatusChangeTime = t
+	return u
+}
+
+// AttrMask contains fields to mask StableAttr and UnstableAttr.
+type AttrMask struct {
+	Type             bool
+	DeviceID         bool
+	InodeID          bool
+	BlockSize        bool
+	Size             bool
+	Usage            bool
+	Perms            bool
+	UID              bool
+	GID              bool
+	AccessTime       bool
+	ModificationTime bool
+	StatusChangeTime bool
+	Links            bool
+}
+
+// Empty returns true if all fields in AttrMask are false.
+func (a AttrMask) Empty() bool {
+	return a == AttrMask{}
+}
+
+// Union returns an AttrMask containing the inclusive disjunction of fields in a and b.
+func (a AttrMask) Union(b AttrMask) AttrMask {
+	return AttrMask{
+		Type:             a.Type || b.Type,
+		DeviceID:         a.DeviceID || b.DeviceID,
+		InodeID:          a.InodeID || b.InodeID,
+		BlockSize:        a.BlockSize || b.BlockSize,
+		Size:             a.Size || b.Size,
+		Usage:            a.Usage || b.Usage,
+		Perms:            a.Perms || b.Perms,
+		UID:              a.UID || b.UID,
+		GID:              a.GID || b.GID,
+		AccessTime:       a.AccessTime || b.AccessTime,
+		ModificationTime: a.ModificationTime || b.ModificationTime,
+		StatusChangeTime: a.StatusChangeTime || b.StatusChangeTime,
+		Links:            a.Links || b.Links,
+	}
+}
+
+// PermMask are file access permissions.
+type PermMask struct {
+	// Read indicates reading is permitted.
+	Read bool
+
+	// Write indicates writing is permitted.
+	Write bool
+
+	// Execute indicates execution is permitted.
+	Execute bool
+}
+
+// OnlyRead returns true when only the read bit is set.
+func (p PermMask) OnlyRead() bool {
+	return p.Read && !p.Write && !p.Execute
+}
+
+// String implements the fmt.Stringer interface for PermMask.
+func (p PermMask) String() string {
+	return fmt.Sprintf("PermMask{Read: %v, Write: %v, Execute: %v}", p.Read, p.Write, p.Execute)
+}
+
+// Mode returns the system mode (syscall.S_IXOTH, etc.) for these permissions
+// in the "other" bits.
+func (p PermMask) Mode() (mode os.FileMode) {
+	if p.Read {
+		mode |= syscall.S_IROTH
+	}
+	if p.Write {
+		mode |= syscall.S_IWOTH
+	}
+	if p.Execute {
+		mode |= syscall.S_IXOTH
+	}
+	return
+}
+
+// SupersetOf returns true iff the permissions in p are a superset of the
+// permissions in other.
+func (p PermMask) SupersetOf(other PermMask) bool {
+	if !p.Read && other.Read {
+		return false
+	}
+	if !p.Write && other.Write {
+		return false
+	}
+	if !p.Execute && other.Execute {
+		return false
+	}
+	return true
+}
+
+// FilePermissions represents the permissions of a file, with
+// Read/Write/Execute bits for user, group, and other.
+type FilePermissions struct {
+	User  PermMask
+	Group PermMask
+	Other PermMask
+
+	// Sticky, if set on directories, restricts renaming and deletion of
+	// files in those directories to the directory owner, file owner, or
+	// CAP_FOWNER. The sticky bit is ignored when set on other files.
+	Sticky bool
+
+	// SetUID executables can call UID-setting syscalls without CAP_SETUID.
+	SetUID bool
+
+	// SetGID executables can call GID-setting syscalls without CAP_SETGID.
+	SetGID bool
+}
+
+// PermsFromMode takes the Other permissions (last 3 bits) of a FileMode and
+// returns a set of PermMask.
+func PermsFromMode(mode linux.FileMode) (perms PermMask) {
+	perms.Read = mode&linux.ModeOtherRead != 0
+	perms.Write = mode&linux.ModeOtherWrite != 0
+	perms.Execute = mode&linux.ModeOtherExec != 0
+	return
+}
+
+// FilePermsFromP9 converts a p9.FileMode to a FilePermissions struct.
+func FilePermsFromP9(mode p9.FileMode) FilePermissions {
+	return FilePermsFromMode(linux.FileMode(mode))
+}
+
+// FilePermsFromMode converts a system file mode to a FilePermissions struct.
+func FilePermsFromMode(mode linux.FileMode) (fp FilePermissions) {
+	perm := mode.Permissions()
+	fp.Other = PermsFromMode(perm)
+	fp.Group = PermsFromMode(perm >> 3)
+	fp.User = PermsFromMode(perm >> 6)
+	fp.Sticky = mode&linux.ModeSticky == linux.ModeSticky
+	fp.SetUID = mode&linux.ModeSetUID == linux.ModeSetUID
+	fp.SetGID = mode&linux.ModeSetGID == linux.ModeSetGID
+	return
+}
+
+// LinuxMode returns the linux mode_t representation of these permissions.
+func (f FilePermissions) LinuxMode() linux.FileMode {
+	m := linux.FileMode(f.User.Mode()<<6 | f.Group.Mode()<<3 | f.Other.Mode())
+	if f.SetUID {
+		m |= linux.ModeSetUID
+	}
+	if f.SetGID {
+		m |= linux.ModeSetGID
+	}
+	if f.Sticky {
+		m |= linux.ModeSticky
+	}
+	return m
+}
+
+// OSMode returns the Go runtime's OS independent os.FileMode representation of
+// these permissions.
+func (f FilePermissions) OSMode() os.FileMode {
+	m := os.FileMode(f.User.Mode()<<6 | f.Group.Mode()<<3 | f.Other.Mode())
+	if f.SetUID {
+		m |= os.ModeSetuid
+	}
+	if f.SetGID {
+		m |= os.ModeSetgid
+	}
+	if f.Sticky {
+		m |= os.ModeSticky
+	}
+	return m
+}
+
+// AnyExecute returns true if any of U/G/O have the execute bit set.
+func (f FilePermissions) AnyExecute() bool {
+	return f.User.Execute || f.Group.Execute || f.Other.Execute
+}
+
+// AnyWrite returns true if any of U/G/O have the write bit set.
+func (f FilePermissions) AnyWrite() bool {
+	return f.User.Write || f.Group.Write || f.Other.Write
+}
+
+// AnyRead returns true if any of U/G/O have the read bit set.
+func (f FilePermissions) AnyRead() bool {
+	return f.User.Read || f.Group.Read || f.Other.Read
+}
+
+// FileOwner represents ownership of a file.
+type FileOwner struct {
+	UID auth.KUID
+	GID auth.KGID
+}
+
+// RootOwner corresponds to KUID/KGID 0/0.
+var RootOwner = FileOwner{
+	UID: auth.RootKUID,
+	GID: auth.RootKGID,
+}