1 files changed, 110 insertions, 0 deletions
diff --git a/internal/fusefrontend_reverse_v1api/virtualfile.go b/internal/fusefrontend_reverse_v1api/virtualfile.go
new file mode 100644
index 0000000..f258e7f
--- /dev/null
+++ b/internal/fusefrontend_reverse_v1api/virtualfile.go
@@ -0,0 +1,110 @@
+package fusefrontend_reverse
+
+import (
+	"log"
+	"path/filepath"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+
+	"github.com/hanwen/go-fuse/v2/fuse"
+	"github.com/hanwen/go-fuse/v2/fuse/nodefs"
+
+	"github.com/rfjakob/gocryptfs/internal/inomap"
+	"github.com/rfjakob/gocryptfs/internal/nametransform"
+	"github.com/rfjakob/gocryptfs/internal/pathiv"
+	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
+	"github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+const (
+	// virtualFileMode is the mode to use for virtual files (gocryptfs.diriv and
+	// *.name). They are always readable, as stated in func Access
+	virtualFileMode = syscall.S_IFREG | 0444
+	// We use inomap's `Tag` feature to generate unique inode numbers for
+	// virtual files. These are the tags we use.
+	inoTagDirIV    = 1
+	inoTagNameFile = 2
+)
+
+func (rfs *ReverseFS) newDirIVFile(cRelPath string) (nodefs.File, fuse.Status) {
+	cDir := nametransform.Dir(cRelPath)
+	dir, err := rfs.decryptPath(cDir)
+	if err != nil {
+		return nil, fuse.ToStatus(err)
+	}
+	iv := pathiv.Derive(cDir, pathiv.PurposeDirIV)
+	return rfs.newVirtualFile(iv, rfs.args.Cipherdir, dir, inoTagDirIV)
+}
+
+type virtualFile struct {
+	// Embed nodefs.defaultFile for a ENOSYS implementation of all methods
+	nodefs.File
+	// pointer to parent filesystem
+	rfs *ReverseFS
+	// file content
+	content []byte
+	// backing directory
+	cipherdir string
+	// path to a parent file (relative to cipherdir)
+	parentFile string
+	// inomap `Tag`.
+	// Depending on the file type, either `inoTagDirIV` or `inoTagNameFile`.
+	inoTag uint8
+}
+
+// newVirtualFile creates a new in-memory file that does not have a representation
+// on disk. "content" is the file content. Timestamps and file owner are copied
+// from "parentFile" (plaintext path relative to "cipherdir").
+// For a "gocryptfs.diriv" file, you would use the parent directory as
+// "parentFile".
+func (rfs *ReverseFS) newVirtualFile(content []byte, cipherdir string, parentFile string, inoTag uint8) (nodefs.File, fuse.Status) {
+	if inoTag == 0 {
+		log.Panicf("BUG: inoTag for virtual file is zero - this will cause ino collisions!")
+	}
+	return &virtualFile{
+		File:       nodefs.NewDefaultFile(),
+		rfs:        rfs,
+		content:    content,
+		cipherdir:  cipherdir,
+		parentFile: parentFile,
+		inoTag:     inoTag,
+	}, fuse.OK
+}
+
+// Read - FUSE call
+func (f *virtualFile) Read(buf []byte, off int64) (resultData fuse.ReadResult, status fuse.Status) {
+	if off >= int64(len(f.content)) {
+		return nil, fuse.OK
+	}
+	end := int(off) + len(buf)
+	if end > len(f.content) {
+		end = len(f.content)
+	}
+	return fuse.ReadResultData(f.content[off:end]), fuse.OK
+}
+
+// GetAttr - FUSE call
+func (f *virtualFile) GetAttr(a *fuse.Attr) fuse.Status {
+	dir := filepath.Dir(f.parentFile)
+	dirfd, err := syscallcompat.OpenDirNofollow(f.cipherdir, dir)
+	if err != nil {
+		return fuse.ToStatus(err)
+	}
+	defer syscall.Close(dirfd)
+	name := filepath.Base(f.parentFile)
+	var st2 unix.Stat_t
+	err = syscallcompat.Fstatat(dirfd, name, &st2, unix.AT_SYMLINK_NOFOLLOW)
+	if err != nil {
+		tlog.Debug.Printf("GetAttr: Fstatat %q: %v\n", f.parentFile, err)
+		return fuse.ToStatus(err)
+	}
+	st := syscallcompat.Unix2syscall(st2)
+	q := inomap.NewQIno(uint64(st.Dev), f.inoTag, uint64(st.Ino))
+	st.Ino = f.rfs.inoMap.Translate(q)
+	st.Size = int64(len(f.content))
+	st.Mode = virtualFileMode
+	st.Nlink = 1
+	a.FromStat(&st)
+	return fuse.OK
+}