libgocryptfs/internal/fusefrontend_reverse/root_node.go

package fusefrontend_reverse

import (
	"log"
	"strings"
	"syscall"

	"golang.org/x/sys/unix"

	"github.com/hanwen/go-fuse/v2/fs"

	"github.com/rfjakob/gocryptfs/internal/contentenc"
	"github.com/rfjakob/gocryptfs/internal/fusefrontend"
	"github.com/rfjakob/gocryptfs/internal/inomap"
	"github.com/rfjakob/gocryptfs/internal/nametransform"
	"github.com/rfjakob/gocryptfs/internal/syscallcompat"

	"github.com/sabhiram/go-gitignore"
)

// RootNode is the root directory in a `gocryptfs -reverse` mount
type RootNode struct {
	Node
	// Stores configuration arguments
	args fusefrontend.Args
	// Filename encryption helper
	nameTransform nametransform.NameTransformer
	// Content encryption helper
	contentEnc *contentenc.ContentEnc
	// Tests whether a path is excluded (hidden) from the user. Used by -exclude.
	excluder *ignore.GitIgnore
	// inoMap translates inode numbers from different devices to unique inode
	// numbers.
	inoMap *inomap.InoMap
}

// NewRootNode returns an encrypted FUSE overlay filesystem.
// In this case (reverse mode) the backing directory is plain-text and
// ReverseFS provides an encrypted view.
func NewRootNode(args fusefrontend.Args, c *contentenc.ContentEnc, n nametransform.NameTransformer) *RootNode {
	return &RootNode{
		args:          args,
		nameTransform: n,
		contentEnc:    c,
		inoMap:        inomap.New(),
		excluder:      prepareExcluder(args),
	}
}

// You can pass either gocryptfs.longname.XYZ.name or gocryptfs.longname.XYZ.
func (rn *RootNode) findLongnameParent(fd int, diriv []byte, longname string) (pName string, cFullName string, errno syscall.Errno) {
	if strings.HasSuffix(longname, nametransform.LongNameSuffix) {
		longname = nametransform.RemoveLongNameSuffix(longname)
	}
	entries, err := syscallcompat.Getdents(fd)
	if err != nil {
		errno = fs.ToErrno(err)
		return
	}
	for _, entry := range entries {
		if len(entry.Name) <= shortNameMax {
			continue
		}
		cFullName = rn.nameTransform.EncryptName(entry.Name, diriv)
		if len(cFullName) <= unix.NAME_MAX {
			// Entry should have been skipped by the "continue" above
			log.Panic("logic error or wrong shortNameMax constant?")
		}
		hName := rn.nameTransform.HashLongName(cFullName)
		if longname == hName {
			pName = entry.Name
			break
		}
	}
	if pName == "" {
		errno = syscall.ENOENT
		return
	}
	return
}

// isExcludedPlain finds out if the plaintext path "pPath" is
// excluded (used when -exclude is passed by the user).
func (rn *RootNode) isExcludedPlain(pPath string) bool {
	return rn.excluder != nil && rn.excluder.MatchesPath(pPath)
}