[Node.js Security] How to Build Secure Node.js Applications?

When you are developing an application, no matter which tools and platforms you are using in the process, the matter of application security is one of the primary concerns. In one way or another, your solution will contain your company’s sensitive data and provide access to your customers’ data which can be even more disastrous in the event of a breach. So, securing your application is one of the things you should think about at the very early stages of custom mobile or web app development planning.

Yes, you need to think through all the security system before you actually start the development process, thus security is in many ways defined by the tools you use. Programming languages, development platforms, third-party components have inherent security measures and, regrettably, security vulnerabilities which must be taken into account. Revolving around the security aspects, you will make the most of your development environment while not compromising the safety and security of both your business and clients.

Many JavaScript developers now opt for Node.js as their environment. Node.js provides a platform for executing JavaScript code and is the first platform supporting JavaScript code on the server side. With Node.js, you will be able to use the same programming language both for the frontend and backend, which is a huge advantage. So, the reasons for Node.js popularity in the web application development field are quite obvious, but how relevant are they in terms of security?

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Authentication in Node.js

Authentication is one of the primary security stages at which user is identified as permitted to access the application at all. Authentication verifies the user’s identity through one or several checks. In Node.js, authentication can be either session-based or token-based. In session-based authentication, the user’s credentials are compared to the user account stored on the server and, in the event of successful validation, a session is started for the user. Whenever the session expires, the user needs to log in again. In token-based authentication, the user’s credentials are applied to generate a string called a token which is then associated with the user’s requests to the server.

Related story: Python vs Node.js: Which is Better for Your Project

In both cases, the strength of the authentication mechanism and, consequently, the security level can largely depend on the rules used in the programming of the authentication flow. For example, a developer can use a very long, or even infinite, expiration period for sessions while working on the application. This is convenient, as there is no need to log in often and the work process can go uninterrupted for a long time. However, if an infinite session period is then committed to the production, this can become a serious security threat, as user sessions will remain active creating more possibilities for breach. The same concerns tokens which can also be set to never expire. Thus, the obvious recommendation here would be either not to use infinite expiration periods at all or, if you do use them, make sure they are not getting to production. A very simple prevention measure which could mean a lot.

This example clearly shows that many Node.js security issues can be prevented by using common sense and exercising attentiveness to detail.

And, of course, use well-tried reliable authentication tools. The following ones are among the recommended:

Error Handling

Whenever an error occurs in the application, the user is informed through an error message. This is OK, as this is the expected behavior of the application. However, while error messages are intended to improve app usability, they sometimes can be a potential security vulnerability.

Usually, the error message contains the explanation of what’s actually gone wrong for the user to understand the reason and, in certain cases, to change the request in order to obtain the desired response. At the same time, when the error is related to the application code syntax, it can be set to display the entire log content on the frontend. For an experienced hacker, the log content can reveal a lot of sensitive internal information about the application code structure and tools used within the software.

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So, if you are going to develop a secure Node.js application, make sure your logs are not displayed openly. Run logs in the background and replace them with a neutral error message on the frontend.

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Request Validation

Another aspect which has to be considered, while building a secure Node.js application, is a validation of requests or, in other words, a check of the incoming data for possible inconsistencies. It may seem that invalid requests do not directly affect the security of a Node.js application, however, they may influence its performance and robustness. Validating the incoming data types and formats and rejecting requests not conforming to the set rules can be an additional measure of securing your Node.js application.

Request validation can include multiple criteria against which the data is compared:

  • Data type – a certain parameter can be set to accept only numeric values, for example. In this case, an alpha-numeric value will be rejected
  • Data formats – even if you have already defined a parameter as numeric, you can go further and specify that the value must always be an integer. With such condition, no decimal values will pass the validation
  • Mandatory and optional parameters – a properly set validation mechanism is able to check whether the request contains all mandatory fields. This can be considered a direct security measure – imagine an authentication flow which does not validate whether the user has entered the password or not.

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Of course, the Node.js community has developed quite a number of tools and libraries to help with building secure applications with Node.js. They are available as open-source projects, and you are free to use them when creating the next JavaScript application:

Securing Your Dependencies

Obviously, the most secure and reliable code is the one you wrote yourself. However, nowadays, applications written from scratch are quite rare, as developers tend to use third-party modules in their projects more and more often. On one hand, third-party components are a great boost, as employing them significantly reduces the man-hours required to create an application, and, consequently, shortens the time-to-market. On the other hand, when you find a well-rated module which seems perfect for your purposes, do you really look inside? Do you check everything it does? Can you be sure that, while running your tasks, it is not doing anything behind your back?

We are not trying to imply that third-party components should be avoided. On the contrary, use them to optimize your development process, but do not take anything at face value. Use dependency scanning tools to identify possible vulnerabilities:

These tools can show where you can eventually have security issues and suggest measures to take.

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At the same time, if you are looking for ways to make your Node.js application secure, remember that applications requiring enhanced security do not use third-party modules at all.

Open-Source – Better Safe Than Sorry

Today, open-sourcing is one of the hottest trends in the global development community. Its initial idea is brilliant – use of joint efforts to create and improve various software products. While many Node.js developers work on the same thing they can look at it from different perspectives and focus on different features. In many cases, the result is a reliable product which is constantly being improved and developed to make it even better.

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However, some code contributors may be not as experienced as their colleagues and some of them may be downright ill-meaning. The fundamental principle of open-source is that anyone can contribute, and this, unfortunately, includes developers with criminal ideas, as well. As with third-party components, using open-source products also requires great care, as you never know what hidden features contributors have included.

Node.js Security Tools and Best Practices

Node.js is a truly powerful development environment, and it can become a reliable foundation for your projects if you enhance it with tools allowing to improve its security. We recommend trying the following tools which can reduce your Node.js application security vulnerability:

  • helmet protects your application by setting HTTP headers. In short, helmet can be used to filter the URLs and IP addresses through which your application can be accessed. By defining the list of “safe” URLs, you will shut the door to the potentially harmful ones
  • csurf validates tokens in incoming requests and rejects the invalid ones
  • node rate limiter controls the rate of repeated requests. This function can protect you from brute force attacks
  • cors enables cross-origin resource sharing

In view of the above, we can put together a kind of a Node.js security checklist which you can use in your everyday work:

  • Do not weaken your authentication or, if you do use some “relaxed” authentication to save time for development, make sure it does not get into production
  • Do not trust third-party modules completely. Use them wisely and check their functionality carefully, even with high community ratings
  • Use validation tools to filter all incoming data
  • Limit access to your application by defining “white lists” of URLs and IP addresses

As the conclusion, if we talk about security, the fundamental principle is that it should never be ignored, neglected or implemented on the leftover basis. Security is too important to be considered at the last minute. Whenever you come across a security rule or requirement – be it in software programming or in your everyday life – remember that there is a tragic story behind most of them. Small and seemingly unimportant security precautions can save money, businesses, and reputations in the long run. Use security measures to stay safe and protect your company, your customers, your partners and your unique products. 

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