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package fusefrontend_reverse
import (
"log"
"os"
"path/filepath"
"strings"
"sync/atomic"
"syscall"
"github.com/rfjakob/gocryptfs/v2/internal/exitcodes"
"github.com/rfjakob/gocryptfs/v2/internal/tlog"
"golang.org/x/sys/unix"
"github.com/hanwen/go-fuse/v2/fs"
"github.com/hanwen/go-fuse/v2/fuse"
"github.com/rfjakob/gocryptfs/v2/internal/contentenc"
"github.com/rfjakob/gocryptfs/v2/internal/fusefrontend"
"github.com/rfjakob/gocryptfs/v2/internal/inomap"
"github.com/rfjakob/gocryptfs/v2/internal/nametransform"
"github.com/rfjakob/gocryptfs/v2/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.NameTransform
// Content encryption helper
contentEnc *contentenc.ContentEnc
// Tests whether a path is excluded (hidden) from the user. Used by -exclude.
excluder ignore.IgnoreParser
// inoMap translates inode numbers from different devices to unique inode
// numbers.
inoMap *inomap.InoMap
// rootDev stores the device number of the backing directory. Used for
// --one-file-system.
rootDev uint64
// If a file name length is shorter than shortNameMax, there is no need to
// hash it.
shortNameMax int
// gen is the node generation number. Normally, it is always set to 1,
// but reverse mode, like -sharestorage, uses an incrementing counter for new nodes.
// This makes each directory entry unique (even hard links),
// makes go-fuse hand out separate FUSE Node IDs for each, and prevents
// bizarre problems when inode numbers are reused behind our back,
// like this one: https://github.com/rfjakob/gocryptfs/issues/802
gen uint64
}
// 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.NameTransform) *RootNode {
var rootDev uint64
var st syscall.Stat_t
var shortNameMax int
if err := syscall.Stat(args.Cipherdir, &st); err != nil {
tlog.Warn.Printf("Could not stat backing directory %q: %v", args.Cipherdir, err)
if args.OneFileSystem {
tlog.Fatal.Printf("This is a fatal error in combination with -one-file-system")
os.Exit(exitcodes.CipherDir)
}
} else {
rootDev = uint64(st.Dev)
}
shortNameMax = n.GetLongNameMax() * 3 / 4
shortNameMax = shortNameMax - shortNameMax%16 - 1
rn := &RootNode{
args: args,
nameTransform: n,
contentEnc: c,
inoMap: inomap.New(rootDev),
rootDev: rootDev,
shortNameMax: shortNameMax,
}
if len(args.Exclude) > 0 || len(args.ExcludeWildcard) > 0 || len(args.ExcludeFrom) > 0 {
rn.excluder = prepareExcluder(args)
}
return rn
}
// 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) {
defer func() {
tlog.Debug.Printf("findLongnameParent: %d %x %q -> %q %q %d\n", fd, diriv, longname, pName, cFullName, 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) <= rn.shortNameMax {
continue
}
cFullName, err = rn.nameTransform.EncryptName(entry.Name, diriv)
if err != nil {
continue
}
if len(cFullName) <= unix.NAME_MAX && len(cFullName) <= rn.nameTransform.GetLongNameMax() {
// Entry should have been skipped by the shortNameMax check above
log.Panic("logic error or wrong shortNameMax?")
}
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 {
// root dir can't be excluded
if pPath == "" {
return false
}
return rn.excluder != nil && rn.excluder.MatchesPath(pPath)
}
// excludeDirEntries filters out directory entries that are "-exclude"d.
// pDir is the relative plaintext path to the directory these entries are
// from. The entries should be plaintext files.
func (rn *RootNode) excludeDirEntries(d *dirfdPlus, entries []fuse.DirEntry) (filtered []fuse.DirEntry) {
if rn.excluder == nil {
return entries
}
filtered = make([]fuse.DirEntry, 0, len(entries))
for _, entry := range entries {
// filepath.Join handles the case of pDir="" correctly:
// Join("", "foo") -> "foo". This does not: pDir + "/" + name"
p := filepath.Join(d.pPath, entry.Name)
if rn.isExcludedPlain(p) {
// Skip file
continue
}
filtered = append(filtered, entry)
}
return filtered
}
// uniqueStableAttr returns a fs.StableAttr struct with a unique generation number,
// preventing files to appear hard-linked, even when they have the same inode number.
//
// This is good because inode numbers can be reused behind our back, which could make
// unrelated files appear hard-linked.
// Example: https://github.com/rfjakob/gocryptfs/issues/802
func (rn *RootNode) uniqueStableAttr(mode uint32, ino uint64) fs.StableAttr {
return fs.StableAttr{
Mode: mode,
Ino: ino,
// Make each directory entry a unique node by using a unique generation
// value. Also see the comment at RootNode.gen for details.
Gen: atomic.AddUint64(&rn.gen, 1),
}
}
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