Add CreateEncryptedBlob and GetDecryptReader

repository/index_test.go

@@ -3,7 +3,9 @@ package repository_test
 import (
 	"bytes"
 	"crypto/rand"
+	"fmt"
 	"io"
+	"path/filepath"
 	"testing"
 
 	"github.com/restic/restic/backend"

repository/repository.go

@@ -456,44 +456,82 @@ func (r *Repository) SetIndex(i *Index) {
 	r.idx = i
 }
 
-// SaveIndex saves all new packs in the index in the backend, returned is the
-// storage ID.
-func (r *Repository) SaveIndex() (backend.ID, error) {
-	debug.Log("Repo.SaveIndex", "Saving index")
+// BlobWriter encrypts and saves the data written to it in a backend. After
+// Close() was called, ID() returns the backend.ID.
+type BlobWriter struct {
+	id     backend.ID
+	blob   backend.Blob
+	hw     *backend.HashingWriter
+	ewr    io.WriteCloser
+	t      backend.Type
+	closed bool
+}
 
-	// create blob
+// CreateEncryptedBlob returns a BlobWriter that encrypts and saves the data
+// written to it in the backend. After Close() was called, ID() returns the
+// backend.ID.
+func (r *Repository) CreateEncryptedBlob(t backend.Type) (*BlobWriter, error) {
 	blob, err := r.be.Create()
 	if err != nil {
-		return backend.ID{}, err
+		return nil, err
 	}
 
-	debug.Log("Repo.SaveIndex", "create new pack %p", blob)
-
 	// hash
 	hw := backend.NewHashingWriter(blob, sha256.New())
 
 	// encrypt blob
 	ewr := crypto.EncryptTo(r.key, hw)
 
-	err = r.idx.Encode(ewr)
+	return &BlobWriter{t: t, blob: blob, hw: hw, ewr: ewr}, nil
+}
+
+func (bw *BlobWriter) Write(buf []byte) (int, error) {
+	return bw.ewr.Write(buf)
+}
+
+// Close finalizes the blob in the backend, afterwards ID() can be used to retrieve the ID.
+func (bw *BlobWriter) Close() error {
+	if bw.closed {
+		return errors.New("BlobWriter already closed")
+	}
+	bw.closed = true
+
+	err := bw.ewr.Close()
+	if err != nil {
+		return err
+	}
+
+	copy(bw.id[:], bw.hw.Sum(nil))
+	return bw.blob.Finalize(bw.t, bw.id.String())
+}
+
+// ID returns the Id the blob has been written to after Close() was called.
+func (bw *BlobWriter) ID() backend.ID {
+	return bw.id
+}
+
+// SaveIndex saves all new packs in the index in the backend, returned is the
+// storage ID.
+func (r *Repository) SaveIndex() (backend.ID, error) {
+	debug.Log("Repo.SaveIndex", "Saving index")
+
+	blob, err := r.CreateEncryptedBlob(backend.Index)
 	if err != nil {
 		return backend.ID{}, err
 	}
 
-	err = ewr.Close()
+	err = r.idx.Encode(blob)
 	if err != nil {
 		return backend.ID{}, err
 	}
 
-	// finalize blob in the backend
-	sid := backend.ID{}
-	copy(sid[:], hw.Sum(nil))
-
-	err = blob.Finalize(backend.Index, sid.String())
+	err = blob.Close()
 	if err != nil {
 		return backend.ID{}, err
 	}
 
+	sid := blob.ID()
+
 	debug.Log("Repo.SaveIndex", "Saved index as %v", sid.Str())
 
 	return sid, nil
@@ -554,28 +592,61 @@ func LoadIndex(repo *Repository, id string) (*Index, error) {
 	return nil, err
 }
 
+// decryptReadCloser couples an underlying reader with a DecryptReader and
+// implements io.ReadCloser. On Close(), both readers are closed.
+type decryptReadCloser struct {
+	r  io.ReadCloser
+	dr io.ReadCloser
+}
+
+func newDecryptReadCloser(key *crypto.Key, rd io.ReadCloser) (io.ReadCloser, error) {
+	dr, err := crypto.DecryptFrom(key, rd)
+	if err != nil {
+		return nil, err
+	}
+
+	return &decryptReadCloser{r: rd, dr: dr}, nil
+}
+
+func (dr *decryptReadCloser) Read(buf []byte) (int, error) {
+	return dr.dr.Read(buf)
+}
+
+func (dr *decryptReadCloser) Close() error {
+	err := dr.dr.Close()
+	if err != nil {
+		return err
+	}
+
+	return dr.r.Close()
+}
+
+// GetDecryptReader opens the file id stored in the backend and returns a
+// reader that yields the decrypted content. The reader must be closed.
+func (r *Repository) GetDecryptReader(t backend.Type, id string) (io.ReadCloser, error) {
+	rd, err := r.be.Get(t, id)
+	if err != nil {
+		return nil, err
+	}
+
+	return newDecryptReadCloser(r.key, rd)
+}
+
 func loadIndex(repo *Repository, id string, oldFormat bool) (*Index, error) {
 	debug.Log("loadIndex", "Loading index %v", id[:8])
 
-	rd, err := repo.be.Get(backend.Index, id)
+	rd, err := repo.GetDecryptReader(backend.Index, id)
+	if err != nil {
+		return nil, err
+	}
 	defer rd.Close()
-	if err != nil {
-		return nil, err
-	}
-
-	// decrypt
-	decryptRd, err := crypto.DecryptFrom(repo.key, rd)
-	defer decryptRd.Close()
-	if err != nil {
-		return nil, err
-	}
 
 	var idx *Index
 
 	if !oldFormat {
-		idx, _, err = DecodeIndex(decryptRd)
+		idx, _, err = DecodeIndex(rd)
 	} else {
-		idx, _, err = DecodeOldIndex(decryptRd)
+		idx, _, err = DecodeOldIndex(rd)
 	}
 
 	if err != nil {