From 9237b4f53e13075b595131f68edcfb2c831d684e Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Thu, 25 Aug 2016 00:14:36 +0200
Subject: reverse: add skeleton

Compiles but does not do much else.
---
 internal/fusefrontend_reverse/rfile.go | 27 ++++++++++
 internal/fusefrontend_reverse/rfs.go   | 93 ++++++++++++++++++++++++++++++++++
 internal/fusefrontend_reverse/rpath.go | 56 ++++++++++++++++++++
 3 files changed, 176 insertions(+)
 create mode 100644 internal/fusefrontend_reverse/rfile.go
 create mode 100644 internal/fusefrontend_reverse/rfs.go
 create mode 100644 internal/fusefrontend_reverse/rpath.go

diff --git a/internal/fusefrontend_reverse/rfile.go b/internal/fusefrontend_reverse/rfile.go
new file mode 100644
index 0000000..746a0d6
--- /dev/null
+++ b/internal/fusefrontend_reverse/rfile.go
@@ -0,0 +1,27 @@
+package fusefrontend_reverse
+
+import (
+	"os"
+
+	"github.com/hanwen/go-fuse/fuse"
+	"github.com/hanwen/go-fuse/fuse/nodefs"
+
+	"github.com/rfjakob/gocryptfs/internal/contentenc"
+)
+
+type file struct {
+	fd *os.File
+	// Content encryption helper
+	contentEnc *contentenc.ContentEnc
+
+	// nodefs.defaultFile returns ENOSYS for all operations
+	nodefs.File
+}
+
+func NewFile(fd *os.File, contentEnc *contentenc.ContentEnc) (nodefs.File, fuse.Status) {
+	return &file{
+		fd:         fd,
+		contentEnc: contentEnc,
+		File:       nodefs.NewDefaultFile(),
+	}, fuse.OK
+}
diff --git a/internal/fusefrontend_reverse/rfs.go b/internal/fusefrontend_reverse/rfs.go
new file mode 100644
index 0000000..914dccb
--- /dev/null
+++ b/internal/fusefrontend_reverse/rfs.go
@@ -0,0 +1,93 @@
+package fusefrontend_reverse
+
+import (
+	"os"
+
+	"github.com/hanwen/go-fuse/fuse"
+	"github.com/hanwen/go-fuse/fuse/nodefs"
+	"github.com/hanwen/go-fuse/fuse/pathfs"
+
+	"github.com/rfjakob/gocryptfs/internal/contentenc"
+	"github.com/rfjakob/gocryptfs/internal/cryptocore"
+	"github.com/rfjakob/gocryptfs/internal/fusefrontend"
+	"github.com/rfjakob/gocryptfs/internal/nametransform"
+)
+
+type FS struct {
+	// loopbackFileSystem, see go-fuse/fuse/pathfs/loopback.go
+	pathfs.FileSystem
+	// Stores configuration arguments
+	args fusefrontend.Args
+	// Filename encryption helper
+	nameTransform *nametransform.NameTransform
+	// Content encryption helper
+	contentEnc *contentenc.ContentEnc
+}
+
+// Encrypted FUSE overlay filesystem
+func NewFS(args fusefrontend.Args) *FS {
+	cryptoCore := cryptocore.New(args.Masterkey, args.OpenSSL, true)
+	contentEnc := contentenc.New(cryptoCore, contentenc.DefaultBS)
+	nameTransform := nametransform.New(cryptoCore, args.LongNames)
+
+	return &FS{
+		FileSystem:    pathfs.NewLoopbackFileSystem(args.Cipherdir),
+		args:          args,
+		nameTransform: nameTransform,
+		contentEnc:    contentEnc,
+	}
+}
+
+func (fs *FS) GetAttr(relPath string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
+	if fs.isFiltered(relPath) {
+		return nil, fuse.EPERM
+	}
+	relPath, err := fs.decryptPath(relPath)
+	if err != nil {
+		return nil, fuse.ToStatus(err)
+	}
+	a, status := fs.FileSystem.GetAttr(relPath, context)
+	if a == nil {
+		return a, status
+	}
+	// Calculate encrypted file size
+	if a.IsRegular() {
+		a.Size = fs.contentEnc.PlainSizeToCipherSize(a.Size)
+	}
+	return a, fuse.OK
+}
+
+func (fs *FS) Open(relPath string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) {
+	if fs.isFiltered(relPath) {
+		return nil, fuse.EPERM
+	}
+	absPath, err := fs.abs(fs.decryptPath(relPath))
+	if err != nil {
+		return nil, fuse.ToStatus(err)
+	}
+	f, err := os.OpenFile(absPath, int(flags), 0666)
+	if err != nil {
+		return nil, fuse.ToStatus(err)
+	}
+	return NewFile(f, fs.contentEnc)
+}
+
+func (fs *FS) OpenDir(relPath string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
+	relPath, err := fs.decryptPath(relPath)
+	if err != nil {
+		return nil, fuse.ToStatus(err)
+	}
+	// Read plaintext dir
+	entries, status := fs.FileSystem.OpenDir(relPath, context)
+	if entries == nil {
+		return nil, status
+	}
+	// Encrypt names
+	for i := range entries {
+		entries[i].Name, err = fs.encryptPath(entries[i].Name)
+		if err != nil {
+			return nil, fuse.ToStatus(err)
+		}
+	}
+	return entries, fuse.OK
+}
diff --git a/internal/fusefrontend_reverse/rpath.go b/internal/fusefrontend_reverse/rpath.go
new file mode 100644
index 0000000..9377958
--- /dev/null
+++ b/internal/fusefrontend_reverse/rpath.go
@@ -0,0 +1,56 @@
+package fusefrontend_reverse
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+func (fs *FS) abs(relPath string, err error) (string, error) {
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(fs.args.Cipherdir, relPath), nil
+}
+
+const (
+	ENCRYPT = iota
+	DECRYPT
+)
+
+func (fs *FS) encryptPath(relPath string) (string, error) {
+	return fs.transformPath(relPath, ENCRYPT)
+}
+
+func (fs *FS) decryptPath(relPath string) (string, error) {
+	return fs.transformPath(relPath, DECRYPT)
+}
+
+func (fs *FS) transformPath(relPath string, direction int) (string, error) {
+	if fs.args.PlaintextNames {
+		return relPath, nil
+	}
+	var err error
+	var transformedParts []string
+	iv := make([]byte, 16)
+	parts := strings.Split(relPath, "/")
+	for _, part := range parts {
+		var transformedPart string
+		switch direction {
+		case ENCRYPT:
+			transformedPart = fs.nameTransform.EncryptName(part, iv)
+		case DECRYPT:
+			transformedPart, err = fs.nameTransform.DecryptName(part, iv)
+			if err != nil {
+				return "", err
+			}
+		default:
+			panic("bug: invalid direction value")
+		}
+		transformedParts = append(transformedParts, transformedPart)
+	}
+	return filepath.Join(transformedParts...), nil
+}
+
+func (fs *FS) isFiltered(relPath string) bool {
+	return false
+}
-- 
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