chattr.go

/*
Credits to :
  - Dániel Görbe <https://github.com/g0rbe>
  - Canonical Ltd. <https://github.com/snapcore/snapd/blob/8fcab0dd4e20e28fc68f129e6680b17bff70a37c/osutil/chattr.go>
*/
package core

import (
	"os"
	"os/exec"
	"syscall"
	"unsafe"
)

/*
File attributes.
*/
const (
	// from /usr/include/linux/fs.h
	FS_SECRM_FL        = 0x00000001 /* Secure deletion */
	FS_UNRM_FL         = 0x00000002 /* Undelete */
	FS_COMPR_FL        = 0x00000004 /* Compress file */
	FS_SYNC_FL         = 0x00000008 /* Synchronous updates */
	FS_IMMUTABLE_FL    = 0x00000010 /* Immutable file */
	FS_APPEND_FL       = 0x00000020 /* writes to file may only append */
	FS_NODUMP_FL       = 0x00000040 /* do not dump file */
	FS_NOATIME_FL      = 0x00000080 /* do not update atime */
	FS_DIRTY_FL        = 0x00000100
	FS_COMPRBLK_FL     = 0x00000200 /* One or more compressed clusters */
	FS_NOCOMP_FL       = 0x00000400 /* Don't compress */
	FS_ENCRYPT_FL      = 0x00000800 /* Encrypted file */
	FS_BTREE_FL        = 0x00001000 /* btree format dir */
	FS_INDEX_FL        = 0x00001000 /* hash-indexed directory */
	FS_IMAGIC_FL       = 0x00002000 /* AFS directory */
	FS_JOURNAL_DATA_FL = 0x00004000 /* Reserved for ext3 */
	FS_NOTAIL_FL       = 0x00008000 /* file tail should not be merged */
	FS_DIRSYNC_FL      = 0x00010000 /* dirsync behaviour (directories only) */
	FS_TOPDIR_FL       = 0x00020000 /* Top of directory hierarchies*/
	FS_HUGE_FILE_FL    = 0x00040000 /* Reserved for ext4 */
	FS_EXTENT_FL       = 0x00080000 /* Extents */
	FS_EA_INODE_FL     = 0x00200000 /* Inode used for large EA */
	FS_EOFBLOCKS_FL    = 0x00400000 /* Reserved for ext4 */
	FS_NOCOW_FL        = 0x00800000 /* Do not cow file */
	FS_INLINE_DATA_FL  = 0x10000000 /* Reserved for ext4 */
	FS_PROJINHERIT_FL  = 0x20000000 /* Create with parents projid */
	FS_RESERVED_FL     = 0x80000000 /* reserved for ext2 lib */

)

/*
Request flags.
*/
const (
	// from ioctl_list manpage
	FS_IOC_GETFLAGS uintptr = 0x80086601
	FS_IOC_SETFLAGS uintptr = 0x40086602
)

func ioctl(f *os.File, request uintptr, attrp *int32) error {

	argp := uintptr(unsafe.Pointer(attrp))

	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), request, argp)

	if errno != 0 {
		return os.NewSyscallError("ioctl", errno)
	}

	return nil
}

/*
GetAttr retrieves the attributes of a file.
*/
func GetAttrs(f *os.File) (int32, error) {

	attr := int32(-1)

	err := ioctl(f, FS_IOC_GETFLAGS, &attr)

	return attr, err
}

/*
SetAttr sets the given attribute.
*/
func SetAttr(f *os.File, attr int32) error {

	attrs, err := GetAttrs(f)

	if err != nil {
		return err
	}

	attrs |= attr

	return ioctl(f, FS_IOC_SETFLAGS, &attrs)

}

/*
UnsetAttr unsets the given attribute.
*/
func UnsetAttr(f *os.File, attr int32) error {

	attrs, err := GetAttrs(f)

	if err != nil {
		return err
	}

	attrs ^= (attrs & attr)

	return ioctl(f, FS_IOC_SETFLAGS, &attrs)
}

/*
IsAttr checks whether the given attribute is set.
*/
func IsAttr(f *os.File, attr int32) (bool, error) {

	attrs, err := GetAttrs(f)

	if err != nil {
		return false, err
	}

	if (attrs & attr) != 0 {
		return true, nil
	} else {
		return false, nil
	}

}

/*
Legacy functions using the chattr utility.
*/
func LegacySetAttr(path string, attr string) error {

	cmd := exec.Command("chattr", "+"+attr, path)

	return cmd.Run()
}

func LegacyUnsetAttr(path string, attr string) error {

	cmd := exec.Command("chattr", "-"+attr, path)

	return cmd.Run()
}