added fs encryption overlay

pkg/provider/crypto/fs.go

@@ -0,0 +1,129 @@
+package crypto
+
+import (
+	"cachefs/pkg/provider"
+	"encoding/base64"
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+var _ provider.FS = (*FS)(nil)
+
+type FS struct {
+	fs  provider.FS
+	cbc *aesCbc
+	key []byte
+}
+
+func NewFS(fs provider.FS, key []byte) (*FS, error) {
+	if len(key) != 32 {
+		return nil, errors.New("encryption key length must be 32 bytes")
+	}
+	cbc, err := newAesCbc(key)
+	if err != nil {
+		return nil, err
+	}
+	return &FS{
+		fs:  fs,
+		cbc: cbc,
+		key: key,
+	}, nil
+}
+
+func (fs *FS) encPath(path string) (n string, err error) {
+	parts := strings.Split(path, "/")
+	cparts := make([]string, len(parts))
+	for i, p := range parts {
+		if p == "" {
+			continue
+		}
+		cparts[i] = base64.RawURLEncoding.EncodeToString(
+			fs.cbc.encrypt([]byte(p)),
+		)
+	}
+	n = filepath.Join(cparts...)
+	return
+}
+
+func (fs *FS) decPath(path string) (n string, err error) {
+	parts := strings.Split(path, "/")
+	pparts := make([]string, len(parts))
+	for i, p := range parts {
+		pparts[i] = base64.RawURLEncoding.EncodeToString(
+			fs.cbc.decrypt([]byte(p)),
+		)
+	}
+	n = filepath.Join(pparts...)
+	return
+}
+
+func (fs *FS) name(p string) string {
+	return filepath.Join(fs.Root(), p)
+}
+
+func (fs *FS) Stat(p string) (fs.FileInfo, error) {
+	c, err := fs.encPath(p)
+	if err != nil {
+		return nil, err
+	}
+	fi, err := fs.fs.Stat(c)
+	return stat{FileInfo: fi, name: fs.name(p)}, err
+}
+
+func (fs *FS) Remove(p string) error {
+	c, err := fs.encPath(p)
+	if err != nil {
+		return err
+	}
+	return fs.fs.Remove(c)
+}
+
+func (fs *FS) Open(p string) (provider.File, error) {
+	c, err := fs.encPath(p)
+	if err != nil {
+		return nil, err
+	}
+	f, err := fs.fs.Open(c)
+	if err != nil {
+		return nil, err
+	}
+	return newFile(fs.key, p, fs, f)
+}
+
+func (fs *FS) OpenFile(p string, flags int, mode os.FileMode) (provider.File, error) {
+	c, err := fs.encPath(p)
+	if err != nil {
+		return nil, err
+	}
+	f, err := fs.fs.OpenFile(c, flags, mode)
+	if err != nil {
+		return nil, err
+	}
+	return newFile(fs.key, p, fs, f)
+}
+
+func (fs *FS) MkdirAll(p string, mode os.FileMode) error {
+	c, err := fs.encPath(p)
+	if err != nil {
+		return err
+	}
+	return fs.fs.MkdirAll(c, mode)
+}
+
+func (fs *FS) Root() string {
+	return fs.fs.Root()
+}
+
+func (fs *FS) Fstat(_ uintptr) (int64, error) {
+	return 0, provider.ErrFstat
+}
+
+func (fs *FS) Close() error {
+	fs.key = nil
+	runtime.GC()
+	return nil
+}