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Go Over and Practice Secure Coding

And round it off with our Secure Code Review

By Felipe Ruiz | November 22, 2022 | Category: Philosophy

It never ceases to be glaringly evident how insecure the software used by individuals and organizations in almost every industry on the planet tends to be. Just look at the news in The Record over the last month, and you'll find cyberattacks targeting the aviation, space and education industries (as we saw recently, the latter is among the most attractive to threat actors today). While it is true that many attacks are often successful thanks to social engineering (e.g., phishing campaigns), many others achieve their goal through another major attack vector: the exploitation of security vulnerabilities in software.

Here we are not discussing something that affects only the small and the feeble. Large companies that provide software as a product or service (recent examples: Google, Siemens, and Microsoft), as well as well-known organizations that make use of software (recent examples: a federal agency, Aurubis, and Mitel), continue to be seriously impacted by cyberattacks. Many vulnerabilities exploited by malicious hackers to steal information or disrupt operations are found in the applications' source code (i.e., those instructions that define their structure and functionality and are interpreted by devices). This is why one of the best ways to prevent cyberattacks and their impacts is to develop software products correctly, writing secure source code from the beginning of the software development lifecycle (SDLC).

What is secure coding?

Secure coding or secure programming is the software development practice in which the occurrence of programming errors that give rise to security vulnerabilities is avoided. This activity implies a high knowledge of the programming language in use and the judicious following of conventions and principles or secure coding standards. This is why the development teams of any company interested in its cybersecurity must be trained in this regard.

It is problematic that many developers see the inclusion of security principles in software development as a hindrance. One of the causes of this is the continuous demand for rapid delivery of products and new features within them. In their rush to respond quickly to customer or user requests, sometimes led by managers apathetic about a cybersecurity culture, developers brush aside risk exposure. In other cases, they may be asked or compelled to pay attention to security, but simple factors such as lack of focus or unfamiliarity can also impede secure coding. Software developers' lack of cybersecurity knowledge is commonplace today, so much so that they can ignore, for instance, the existence of public standards such as OWASP. Actually, a first step to prevent security vulnerabilities may be to keep standardized vulnerability databases such as CWE, CERT, CVE, OWASP and PA-DSS, among others, at hand and under review. (Check also our set of vulnerability types.)

Organizations that develop and offer software as a product or service, and have not yet done so, must begin to create or reinforce a security-based culture within their units. This is where the now celebrated DevSecOps approach comes in, where security should be the responsibility of all team members and not just something for a security team. Although it can be a complex and time-consuming change, it is a worthwhile effort in terms of costs and chances of success, and in which the so-called Security Champions (of which we've already spoken about) can step in. As we'll see below, the work of developers can be significantly assisted by security testing. However, it's still essential they understand what they're doing in terms of risks and threats, know where they are making mistakes, and begin to keep practices that enable them to avoid these failures and, consequently, the appearance of vulnerabilities in their products.

Some secure coding practices

It's easy to find secure coding best practices or guidelines on the Internet (e.g., OWASP DevGuide, Microsoft Writing Secure Code, Red Hat Secure Coding Tutorials). For this post, we partly took as a basis Secure Coding Practices - Quick Reference Guide from OWASP (we recommend you check it for more details) and added other considerations and some valuable tips worth mentioning. (Check also our set of security requirements.)

Security from the first line of code

It's imperative to start with the idea of not leaving security for the end of the SDLC. Thinking about and acting in favor of a secure software product from the first line of code makes it possible to avoid subsequent high costs. Not only costs in the remediation of vulnerabilities (these are much lower in the development phases than in the final ones or in production) but also those arising from their exploitation, in other words, security breaches. Developers shouldn't have as their sole objective the rapid release to production of a product with optimal functionality. Among their main purposes, they should include delivering high-quality software that guarantees security.

Thinking like threat actors

Developers should try to look at their creations as if they were malicious hackers themselves. (We once wrote a post entitled Think Like a Hacker! which may serve as a reference in this regard). They should not only focus on the purposes and use cases of the product but also on how criminals could exploit it in case of having vulnerabilities. Developers should be clear about which assets and operations would be attractive to threat actors. They should be aware of potential threats and risk levels and keep in mind and practice preventive measures.

Input validation

The mere use of the developed application or software, specifically the input of data, usually represents a risk. For example, attacks known as SQL injection and cross-site scripting (XSS) can occur due to vulnerabilities arising from trusting external data sources and user input, whereby the software does not distinguish between commands and data. In other words, certain characters can enter the application functioning as malicious code and cause it to behave abnormally or in a way that deviates from its intended operation. Hence the need to continuously validate what enters the software product.

Developers must ensure that data sources are classified as trusted and untrusted. Their product must validate the input (mainly) from untrusted sources appropriately. It must verify the properties of the incoming data and accept only those inputs that comply with specific characteristics (e.g., type, range, length, allowed characters). If the inputs do not comply with them, the application must reject them. To this process, developers should add output encoding, in which all untrusted input is transformed to a safe form, remains as data, and is not executed as code.

Authentication and password management

The software must verify through a standardized process the identity of the user or entity that interacts with it, especially when trying to access resources that are not intended to be public or external systems with confidential material. Authentication failures should generate responses that do not specify which of the requested data were erroneous or invalid. Critical operations such as money transfers, for example, should request re-authentication or multi-factor authentication.

If the application stores credentials, developers should ensure they are always cryptographically one-way solid hashes of passwords. To strengthen the complexity of passwords (preferably passphrases), the application should require users to include numbers and special characters in addition to lowercase and uppercase letters in them. After a few unsuccessful login attempts by a user, the software should deactivate that account for a specific period. Additionally, password modification should be properly controlled, and the application should notify the user each time it occurs.

Access control and session management

In addition to user identity verification, the product must have a process that allows or denies access to resources. Developers should restrict access to certain resources (including protected URLs, functions, services, files, and critical data) to only a few authorized users. They should always apply the principle of least privilege. By default, access must be denied, and the system must maintain and verify conditions or characteristics (beyond role verification) to allow it. Ideally, the software should restrict users to access only the resources necessary to accomplish their tasks or jobs. In a given period, the number of transactions by a user or entity should be limited and unused accounts should be deleted. Moreover, developers should set session inactivity timeouts to be as short as possible, not allow simultaneous logins with the same account and generate new session IDs to replace the old ones periodically.

Cryptography and data protection

Data protection or confidentiality depends heavily on the use of well-known, well-vetted and up-to-date encryption algorithms for sensitive data in transit and at rest. In line with what was mentioned above for passwords, they and no other sensitive information should be stored in clear text or any other form that doesn't involve cryptography. In code that may be accessible to users (server-side source code should not be allowed to be downloaded by users), developers should remove comments that reveal confidential information. The same should be done with unnecessary documentation about the application. The software product must also support removing sensitive data when it's no longer useful. This same kind of information shouldn't be present in cookies, and handling such data shouldn't lead to the generation of cached copies.

Error handling and logging

Related to what we mentioned for authentication failures, invalid activities in the application or product may generate error messages. The idea is that these messages should not reveal information that could be useful to potential attackers (e.g., session identifiers, system details or account information). This same information should not be stored in logs. Logging of events that occur in the code allows the identification of errors. Actions that cause application failures (e.g., input validation, authentication, access control, administrative functions, cryptographic modules) should be logged and blocked. Developers should restrict access to all logs only to a group of authorized users.

System configuration and control

Developers must ensure that servers, frameworks and other system components are at their latest verified versions with all relevant security patches applied. In addition, all unnecessary application files and components (e.g., from third-party code) should be removed. This is somewhat connected to the idea of keeping the code and systems as clean and simple as possible. By reducing the complexity of the product, including only what is really necessary, developers reduce the likelihood of security vulnerabilities emerging. Additionally, it is recommended that they maintain the use of systems for source code control and careful tracking of changes.

Secure code review

The above are just a few recommended practices for secure coding. For them, there is an almost indispensable complement that allows developers to guarantee the high quality of their software products. This is security testing, especially in secure code review mode. In a recent blog post, we described this type of test and the benefits it can bring to an organization that develops software. Essentially, it is a contribution by an external provider, such as Fluid Attacks, in which automated tools and humans (some providers mistakenly restrict themselves to the use of tools) have the mission to detect security vulnerabilities in the source code.

While groups of developers can educate themselves or receive training on practices such as those outlined above, it is not surprising that bugs and vulnerabilities continue to appear in their work over time. Through Fluid Attacks' Secure Code Review, which involves our tools and our team of ethical hackers with techniques such as SAST and SCA, and in which we support around 40 programming languages and use more than 60 international security standards as a basis for assessment, we report to your development teams such security issues that arise in their constructions. As we've said before, these reports serve as feedback to them, and the practice of remediating identified vulnerabilities nurtures their knowledge of secure coding. Although the occurrence of errors will indeed not cease, they will be able to notice and fix them more easily.

As software tends to evolve at an incredible pace to meet users' needs, we offer Secure Code Review as part of our Continuous Hacking service. In this constant process, we are attentive to all the changes in your repositories, and we add techniques beyond the secure code review, such as dynamic application security testing (DAST). Contact us if you want to find out what your development teams are overlooking and what is putting your organization at risk. Register here if you want to start with a 21-day free trial of continuous security testing by our automated tools.

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