From 394c8ca3ed6a13f608c452695df6863538a83e60 Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Sun, 12 May 2024 11:55:34 +0200
Subject: [PATCH] rest/rclone/s3/sftp/swift: move short file detection behind
 feature gate

These backends tend to use a large variety of server implementations.
Some of those implementations might prove problematic with the new
checks.
---
 internal/backend/rest/rest.go   | 3 ++-
 internal/backend/s3/s3.go       | 3 ++-
 internal/backend/sftp/sftp.go   | 3 ++-
 internal/backend/swift/swift.go | 3 ++-
 4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/internal/backend/rest/rest.go b/internal/backend/rest/rest.go
index 5b59b8e4f..f743c3e50 100644
--- a/internal/backend/rest/rest.go
+++ b/internal/backend/rest/rest.go
@@ -17,6 +17,7 @@ import (
 	"github.com/restic/restic/internal/backend/util"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/feature"
 )
 
 // make sure the rest backend implements backend.Backend
@@ -245,7 +246,7 @@ func (b *Backend) openReader(ctx context.Context, h backend.Handle, length int,
 		return nil, &restError{h, resp.StatusCode, resp.Status}
 	}
 
-	if length > 0 && resp.ContentLength != int64(length) {
+	if feature.Flag.Enabled(feature.BackendErrorRedesign) && length > 0 && resp.ContentLength != int64(length) {
 		return nil, &restError{h, http.StatusRequestedRangeNotSatisfiable, "partial out of bounds read"}
 	}
 
diff --git a/internal/backend/s3/s3.go b/internal/backend/s3/s3.go
index afe1653f6..a2c95ac32 100644
--- a/internal/backend/s3/s3.go
+++ b/internal/backend/s3/s3.go
@@ -17,6 +17,7 @@ import (
 	"github.com/restic/restic/internal/backend/util"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/feature"
 
 	"github.com/minio/minio-go/v7"
 	"github.com/minio/minio-go/v7/pkg/credentials"
@@ -404,7 +405,7 @@ func (be *Backend) openReader(ctx context.Context, h backend.Handle, length int,
 		return nil, err
 	}
 
-	if length > 0 {
+	if feature.Flag.Enabled(feature.BackendErrorRedesign) && length > 0 {
 		if info.Size > 0 && info.Size != int64(length) {
 			_ = rd.Close()
 			return nil, minio.ErrorResponse{Code: "InvalidRange", Message: "restic-file-too-short"}
diff --git a/internal/backend/sftp/sftp.go b/internal/backend/sftp/sftp.go
index 7bab25bed..b624c5060 100644
--- a/internal/backend/sftp/sftp.go
+++ b/internal/backend/sftp/sftp.go
@@ -20,6 +20,7 @@ import (
 	"github.com/restic/restic/internal/backend/util"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/feature"
 
 	"github.com/cenkalti/backoff/v4"
 	"github.com/pkg/sftp"
@@ -426,7 +427,7 @@ func (r *SFTP) checkNoSpace(dir string, size int64, origErr error) error {
 // given offset.
 func (r *SFTP) Load(ctx context.Context, h backend.Handle, length int, offset int64, fn func(rd io.Reader) error) error {
 	return util.DefaultLoad(ctx, h, length, offset, r.openReader, func(rd io.Reader) error {
-		if length == 0 {
+		if length == 0 || !feature.Flag.Enabled(feature.BackendErrorRedesign) {
 			return fn(rd)
 		}
 
diff --git a/internal/backend/swift/swift.go b/internal/backend/swift/swift.go
index 616fcf3b7..1643af7fc 100644
--- a/internal/backend/swift/swift.go
+++ b/internal/backend/swift/swift.go
@@ -19,6 +19,7 @@ import (
 	"github.com/restic/restic/internal/backend/util"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/feature"
 
 	"github.com/ncw/swift/v2"
 )
@@ -156,7 +157,7 @@ func (be *beSwift) openReader(ctx context.Context, h backend.Handle, length int,
 		return nil, fmt.Errorf("conn.ObjectOpen: %w", err)
 	}
 
-	if length > 0 {
+	if feature.Flag.Enabled(feature.BackendErrorRedesign) && length > 0 {
 		// get response length, but don't cause backend calls
 		cctx, cancel := context.WithCancel(context.Background())
 		cancel()