use status.Error instead of status.Errorf (#397)

Use `status.Error` instead of `status.Errorf` when the format string is
non-constant and not actually a format string. In the case of the
validator middleware, the error being supplied as a format string could
potentially contain data supplied by an attacker allowing for format
string injection. This doesn't appear to be an actual problem due to
`fmt` being safe in this regards, but it certainly isn't good practice
to provide a format string that an attacker can control.

Fixes #396

retry/retry.go

@@ -236,7 +236,9 @@ func (s *serverStreamingRetryingStream) receiveMsgAndIndicateRetry(m interface{}
 	return isRetriable(err, s.callOpts), err
 }
 
-func (s *serverStreamingRetryingStream) reestablishStreamAndResendBuffer(callCtx context.Context) (grpc.ClientStream, error) {
+func (s *serverStreamingRetryingStream) reestablishStreamAndResendBuffer(
+	callCtx context.Context,
+) (grpc.ClientStream, error) {
 	s.mu.RLock()
 	bufferedSends := s.bufferedSends
 	s.mu.RUnlock()
@@ -310,11 +312,11 @@ func perCallContext(parentCtx context.Context, callOpts *options, attempt uint)
 func contextErrToGrpcErr(err error) error {
 	switch err {
 	case context.DeadlineExceeded:
-		return status.Errorf(codes.DeadlineExceeded, err.Error())
+		return status.Error(codes.DeadlineExceeded, err.Error())
 	case context.Canceled:
-		return status.Errorf(codes.Canceled, err.Error())
+		return status.Error(codes.Canceled, err.Error())
 	default:
-		return status.Errorf(codes.Unknown, err.Error())
+		return status.Error(codes.Unknown, err.Error())
 	}
 }
 

validator/validator.go

@@ -22,7 +22,7 @@ func UnaryServerInterceptor() grpc.UnaryServerInterceptor {
 	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
 		if v, ok := req.(validator); ok {
 			if err := v.Validate(); err != nil {
-				return nil, status.Errorf(codes.InvalidArgument, err.Error())
+				return nil, status.Error(codes.InvalidArgument, err.Error())
 			}
 		}
 		return handler(ctx, req)
@@ -36,7 +36,7 @@ func UnaryClientInterceptor() grpc.UnaryClientInterceptor {
 	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
 		if v, ok := req.(validator); ok {
 			if err := v.Validate(); err != nil {
-				return status.Errorf(codes.InvalidArgument, err.Error())
+				return status.Error(codes.InvalidArgument, err.Error())
 			}
 		}
 		return invoker(ctx, method, req, reply, cc, opts...)
@@ -66,7 +66,7 @@ func (s *recvWrapper) RecvMsg(m interface{}) error {
 	}
 	if v, ok := m.(validator); ok {
 		if err := v.Validate(); err != nil {
-			return status.Errorf(codes.InvalidArgument, err.Error())
+			return status.Error(codes.InvalidArgument, err.Error())
 		}
 	}
 	return nil