azure/b2/gs/s3/swift: adapt cloud backend

internal/backend/azure/azure.go

@@ -167,6 +167,20 @@ func (be *Backend) IsNotExist(err error) bool {
 	return bloberror.HasCode(err, bloberror.BlobNotFound)
 }
 
+func (be *Backend) IsPermanentError(err error) bool {
+	if be.IsNotExist(err) {
+		return true
+	}
+
+	var aerr *azcore.ResponseError
+	if errors.As(err, &aerr) {
+		if aerr.StatusCode == http.StatusRequestedRangeNotSatisfiable || aerr.StatusCode == http.StatusUnauthorized || aerr.StatusCode == http.StatusForbidden {
+			return true
+		}
+	}
+	return false
+}
+
 // Join combines path components with slashes.
 func (be *Backend) Join(p ...string) string {
 	return path.Join(p...)
@@ -313,6 +327,11 @@ func (be *Backend) openReader(ctx context.Context, h backend.Handle, length int,
 		return nil, err
 	}
 
+	if length > 0 && (resp.ContentLength == nil || *resp.ContentLength != int64(length)) {
+		_ = resp.Body.Close()
+		return nil, &azcore.ResponseError{ErrorCode: "restic-file-too-short", StatusCode: http.StatusRequestedRangeNotSatisfiable}
+	}
+
 	return resp.Body, err
 }
 

internal/backend/b2/b2.go

@@ -2,6 +2,7 @@ package b2
 
 import (
 	"context"
+	"fmt"
 	"hash"
 	"io"
 	"net/http"
@@ -31,6 +32,8 @@ type b2Backend struct {
 	canDelete bool
 }
 
+var errTooShort = fmt.Errorf("file is too short")
+
 // Billing happens in 1000 item granularity, but we are more interested in reducing the number of network round trips
 const defaultListMaxItems = 10 * 1000
 
@@ -186,13 +189,36 @@ func (be *b2Backend) IsNotExist(err error) bool {
 	return false
 }
 
+func (be *b2Backend) IsPermanentError(err error) bool {
+	// the library unfortunately endlessly retries authentication errors
+	return be.IsNotExist(err) || errors.Is(err, errTooShort)
+}
+
 // Load runs fn with a reader that yields the contents of the file at h at the
 // given offset.
 func (be *b2Backend) Load(ctx context.Context, h backend.Handle, length int, offset int64, fn func(rd io.Reader) error) error {
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
-	return util.DefaultLoad(ctx, h, length, offset, be.openReader, fn)
+	return util.DefaultLoad(ctx, h, length, offset, be.openReader, func(rd io.Reader) error {
+		if length == 0 {
+			return fn(rd)
+		}
+
+		// there is no direct way to efficiently check whether the file is too short
+		// use a LimitedReader to track the number of bytes read
+		limrd := &io.LimitedReader{R: rd, N: int64(length)}
+		err := fn(limrd)
+
+		// check the underlying reader to be agnostic to however fn() handles the returned error
+		_, rderr := rd.Read([]byte{0})
+		if rderr == io.EOF && limrd.N != 0 {
+			// file is too short
+			return fmt.Errorf("%w: %v", errTooShort, err)
+		}
+
+		return err
+	})
 }
 
 func (be *b2Backend) openReader(ctx context.Context, h backend.Handle, length int, offset int64) (io.ReadCloser, error) {

internal/backend/gs/gs.go

@@ -173,6 +173,21 @@ func (be *Backend) IsNotExist(err error) bool {
 	return errors.Is(err, storage.ErrObjectNotExist)
 }
 
+func (be *Backend) IsPermanentError(err error) bool {
+	if be.IsNotExist(err) {
+		return true
+	}
+
+	var gerr *googleapi.Error
+	if errors.As(err, &gerr) {
+		if gerr.Code == http.StatusRequestedRangeNotSatisfiable || gerr.Code == http.StatusUnauthorized || gerr.Code == http.StatusForbidden {
+			return true
+		}
+	}
+
+	return false
+}
+
 // Join combines path components with slashes.
 func (be *Backend) Join(p ...string) string {
 	return path.Join(p...)
@@ -273,6 +288,11 @@ func (be *Backend) openReader(ctx context.Context, h backend.Handle, length int,
 		return nil, err
 	}
 
+	if length > 0 && r.Attrs.Size < offset+int64(length) {
+		_ = r.Close()
+		return nil, &googleapi.Error{Code: http.StatusRequestedRangeNotSatisfiable, Message: "restic-file-too-short"}
+	}
+
 	return r, err
 }
 

internal/backend/s3/s3.go

@@ -229,6 +229,21 @@ func (be *Backend) IsNotExist(err error) bool {
 	return errors.As(err, &e) && e.Code == "NoSuchKey"
 }
 
+func (be *Backend) IsPermanentError(err error) bool {
+	if be.IsNotExist(err) {
+		return true
+	}
+
+	var merr minio.ErrorResponse
+	if errors.As(err, &merr) {
+		if merr.Code == "InvalidRange" || merr.Code == "AccessDenied" {
+			return true
+		}
+	}
+
+	return false
+}
+
 // Join combines path components with slashes.
 func (be *Backend) Join(p ...string) string {
 	return path.Join(p...)
@@ -384,11 +399,18 @@ func (be *Backend) openReader(ctx context.Context, h backend.Handle, length int,
 	}
 
 	coreClient := minio.Core{Client: be.client}
-	rd, _, _, err := coreClient.GetObject(ctx, be.cfg.Bucket, objName, opts)
+	rd, info, _, err := coreClient.GetObject(ctx, be.cfg.Bucket, objName, opts)
 	if err != nil {
 		return nil, err
 	}
 
+	if length > 0 {
+		if info.Size > 0 && info.Size != int64(length) {
+			_ = rd.Close()
+			return nil, minio.ErrorResponse{Code: "InvalidRange", Message: "restic-file-too-short"}
+		}
+	}
+
 	return rd, err
 }
 

internal/backend/swift/swift.go

@@ -153,7 +153,18 @@ func (be *beSwift) openReader(ctx context.Context, h backend.Handle, length int,
 
 	obj, _, err := be.conn.ObjectOpen(ctx, be.container, objName, false, headers)
 	if err != nil {
-		return nil, errors.Wrap(err, "conn.ObjectOpen")
+		return nil, fmt.Errorf("conn.ObjectOpen: %w", err)
+	}
+
+	if length > 0 {
+		// get response length, but don't cause backend calls
+		cctx, cancel := context.WithCancel(context.Background())
+		cancel()
+		objLength, e := obj.Length(cctx)
+		if e == nil && objLength != int64(length) {
+			_ = obj.Close()
+			return nil, &swift.Error{StatusCode: http.StatusRequestedRangeNotSatisfiable, Text: "restic-file-too-short"}
+		}
 	}
 
 	return obj, nil
@@ -242,6 +253,21 @@ func (be *beSwift) IsNotExist(err error) bool {
 	return errors.As(err, &e) && e.StatusCode == http.StatusNotFound
 }
 
+func (be *beSwift) IsPermanentError(err error) bool {
+	if be.IsNotExist(err) {
+		return true
+	}
+
+	var serr *swift.Error
+	if errors.As(err, &serr) {
+		if serr.StatusCode == http.StatusRequestedRangeNotSatisfiable || serr.StatusCode == http.StatusUnauthorized || serr.StatusCode == http.StatusForbidden {
+			return true
+		}
+	}
+
+	return false
+}
+
 // Delete removes all restic objects in the container.
 // It will not remove the container itself.
 func (be *beSwift) Delete(ctx context.Context) error {