        function hostbasedCb(buf, cb) {
          var signature = privateKey.sign(buf);
          if (signature instanceof Error) {
            signature.message = 'Error while signing data with privateKey: '
                                + signature.message;
            signature.level = 'client-authentication';
            self.emit('error', signature);
            return tryNextAuth();
          }

          cb(signature);
        }
The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.