huaweidrive: fix truncated files being uploaded successfully when the source ends early

The multipart upload copied the source into the request buffer without
checking how many bytes it had read, so a source that supplied fewer
bytes than its declared size was accepted by the server and reported as
a success with a truncated file stored.

Count the bytes actually read and fail the upload if they do not match
the declared size.

Signed-off-by: Rohit Behera <126186063+r0h1tb@users.noreply.github.com>

backend/huaweidrive/huaweidrive.go

@@ -33,6 +33,7 @@ import (
 	"github.com/rclone/rclone/lib/encoder"
 	"github.com/rclone/rclone/lib/oauthutil"
 	"github.com/rclone/rclone/lib/pacer"
+	"github.com/rclone/rclone/lib/readers"
 	"github.com/rclone/rclone/lib/rest"
 	"golang.org/x/oauth2"
 )
@@ -1771,11 +1772,18 @@ func (o *Object) uploadMultipart(ctx context.Context, in io.Reader, leaf, direct
 	}
 
 	// Read and write file content
-	_, err = io.Copy(fileWriter, in)
+	counter := readers.NewCountingReader(in)
+	_, err = io.Copy(fileWriter, counter)
 	if err != nil {
 		return fmt.Errorf("failed to copy file content: %w", err)
 	}
 
+	// Check the source supplied the number of bytes it declared
+	// otherwise a truncated file would be stored as a good upload.
+	if int64(counter.BytesRead()) != size {
+		return fmt.Errorf("expected %d bytes in input, but got %d: %w", size, counter.BytesRead(), io.ErrUnexpectedEOF)
+	}
+
 	err = writer.Close()
 	if err != nil {
 		return fmt.Errorf("failed to close multipart writer: %w", err)