Month: August 2024

Mixing Secure Coding with Programming Lessons

On August 30, 2024

Learning about programming first and then learning secure coding afterwards is a mistake. Even if you are new to a programming language or its concepts, you need to know what can go wrong. You need to know how to handle errors. You need to do some basic checks of data received, no matter what your toolchain looks like. This is part of the learning process. So instead of learning how to use code constructs or language features twice, take the shortcut and address security and understanding of the concepts at once. An example method of classes and their behaviour. If you think in instances, then you will have to deal with the occasional exception. No one would learn the methods first, ignore all error conditions, and then get back to learn about errors.

Another example are variables with numerical values. Numbers are notorious. Even the integer data types stay in the Top 25 CWE list since 2019. Integer overflow or underflow simply happens with the standard arithmetic operators. There is no fancy bug involved, just basic counting. You have to implement range checks. There is no way around this. Even Rust requires you to do extra bound checks by using the checked_add() methods. Secure coding always means more code, not less. This starts with basic data types and operators. You can add these logical pitfalls to exercises and examples. By using this approach, you can convey new techniques and how a mind in the security mindset improves the code. There is also the possibility of switching between “normal” exercises and security lessons with a focus on how things go wrong. It’s not helpful to pretend that code won’t run into bugs or security weaknesses. Put the examples of failure and how to deal with it right into your course from the start.

If you don’t know where to start, then consult the secure coding guidelines and top lists of well-known vulnerabilities. Here are some good pointers to get started:

The Ghost of Legacy Code and its Relation to Security

By René Pfeiffer

On August 19, 2024

In Development, Security

The words legacy and old carry a negative meaning when used with code or software development. Marketing has ingrained in us the belief that everything new is good and everything old should be replaced to ensure people spend money and time. Let me tell you that this is not the case, and that age is not always a suitable metric. Would you rather have your brain surgery from a surgeon with 20+ years of experience or a freshly graduated surgeon on his or her first day at the hospital?

So what is old code? In my dictionary, the label “not maintained anymore” is assigned to legacy and old code. This is where the mainstream definition fails. You can have legacy code which is still maintained. There is a sound reason for using code like this: stability and fewer errors introduced by creating code from scratch. Reimplementing code always means that you start from nothing. Computer science basic courses teach everyone to reuse code in order to avoid these situations. Basically, reusing code means that you allow code to age. Just don’t forget to maintain parts of your application that work and experience few changes. This is the sane version of old code. There is another one.

An old codebase can serve as a showstopper for changes. If you took some poor design decisions in the past, then parts of your code will resist fresh development and features. Prototypes often exhibit this behaviour (a prototype usually never sees the production phase unaltered). When you see this in your application, then it is time to think about refactoring. Refactoring has fewer restrictions if you can do this in your own code. Once components or your platform is part of the legacy code, then you are in for a major upgrade. Operating systems and run-time environments can push changes to your application by requiring a refactoring. Certifications can do the same. Certain environments only allow certified components. Your configuration becomes frozen once applications or run-time get the certification. All changes may require a re-certification. Voilà, here is your stasis, and your code ages.

Legacy code is not a burden per se. It all depends if the code is still subject to maintenance, patches, and security checks. Besides, older code usually has fewer bugs.

Code, Development, Agile, and the Waterfall – Dynamics

By René Pfeiffer

On August 16, 2024

In Development

Code requires a process to create it. The collection of processes, tasks, requirements, and checks is called software development. The big question is how to do it right. Frankly, the answer to this question does not exist. First, not all code is equal. A web server, a filesystem, a database, and a kernel module for network communication contain distinct code, with only a few functions that can be shared. For adding secure coding practices, some attendees of my courses question the application of checklists and cleaning of suspicious data. Security is old-fashioned, because you have to think of risks, how to address them, and how to improve sections of your code that connect to the outside world. People like to term agile where small teams bathe in outbursts of creativity and sprint to implementing requested features. You can achieve anything you set your mind to. Tear down code, write it new, deliver the features. This is not how secure coding works, and this is not how your software development process should look like (regardless what type of paradigm you follow).

It is easy to drift into a rant about the agile manifesto. Condensing the entire development process into 68 words, all done during three days of skiing in Colorado, is bound to create very general statements whose implementation wildly differs. This is not the point I want to make. You can shorten secure coding to 10 to 13 principles. The SEI CERT secure coding documents feature a list with the top 10 methods. It’s still incomplete, and you still have to actually integrate security into your writing-code-process. So you can interpret secure coding as a manifesto, too. Neglecting the implementation has advantages. You can use secure coding with all existing and future programming languages. You can use it on all platforms, also current and yet to be invented. The principles are always true. Secure coding is a model that you can use to improve how your team creates, tests, and deploys code. This also means that adopting a security stance requires you to alter your toolbox. All of us have a favourite development environment. This is the first place where you can get started with secure coding. It’s not all about having the right plugins, but it is important to see what code does while it is being developed.

The title features the words agile and waterfall. Please do yourself a favour and stop thinking about buzzwords. It doesn’t matter how your development process produces code. It matters that the code has next to none security vulnerabilities, shows no undefined behaviour and cannot be abused by third parties. Secure code is possible with any development process provided you follow the principles. Use the principle’s freedoms to your advantage and integrate what works best.