engineering

Language-based security

Language-based security is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Language-based security rather than just read about it. In short: In computer science, language-based security (LBS) is a set of techniques that may be used to strengthen the security of applications on a high level by using the properties of programming languages. LBS is considered to enforce computer security on an application-level, making it possible to prevent vulnerabilities which traditional operating system security is unable to handle.

Key takeaways

Language-based security belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Language-based security to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Language-based security from memory before moving on to harder problems.

Reference excerpt

In computer science, language-based security (LBS) is a set of techniques that may be used to strengthen the security of applications on a high level by using the properties of programming languages. LBS is considered to enforce computer security on an application-level, making it possible to prevent vulnerabilities which traditional operating system security is unable to handle. Software applications are typically specified and implemented in certain programming languages, and in order to protect against attacks, flaws and bugs an application's source code might be vulnerable to, there is a need for application-level security; security evaluating the applications behavior with respect to the programming language. This area is generally known as language-based security.

Motivation The use of large software systems, such as SCADA, is taking place all around the world and computer systems constitute the core of many infrastructures. The society relies greatly on infrastructure such as water, energy, communication and transportation, which again all rely on fully functionally working computer systems. There are several well known examples of when critical systems fail due to bugs or errors in software, such as when shortage of computer memory caused LAX computers to crash and hundreds of flights to be delayed (April 30, 2014). Traditionally, the mechanisms used to control the correct behavior of software are implemented at the operating system level. The operating system handles several possible security violations such as memory access violations, stack overflow violations, access control violations, and many others. This is a crucial part of security in computer systems, however by securing the behavior of software on a more specific level, even stronger security can be achieved. Since a lot of properties and behavior of the software is lost in compilation, it is significantly more difficult to detect vulnerabilities in machine code. By evaluating the source code, before the compilation, the theory and implementation of the programming language can also be considered, and more vulnerabilities can be uncovered.

"So why do developers keep making the same mistakes? Instead of relying on programmers' memories, we should strive to produce tools that codify what is known about common security vulnerabilities and integrate it directly into the development process." — D. Evans and D. Larochelle, 2002

Objective of Language-based security By using LBS, the security of software can be increased in several areas, depending on the techniques used. Common programming errors such as allowing buffer overflows and illegal information flows to occur, can be detected and disallowed in the software used by the consumer. It is also desirable to provide some proof to the consumer about the security properties of the software, making the consumer able to trust the software without having to receive the source code and self checking it for errors. A compiler, taking source code as input, performs several language specific operations on the code in order to translate it into machine readable code. Lexical analysis, preprocessing, parsing, semantic analysis, code generation, and code optimization are all commonly used operations in compilers. By analyzing the source code and using the theory and implementation of the language, the compiler will attempt to correctly translate the high-level code into low-level code, preserving the behavior of the program.

During compilation of programs written in a type-safe language, such as Java, the source code must type-check successfully before compilation. If the type-check fails, the compilation will not be performed, and the source code needs to be modified. This means that, given a correct compiler, any code compiled from a successfully type-checked source program should be clear of invalid assignment errors. This is information which can be of value to the code consumer, as it provides some degree of guarantee that the program will not crash due to some specific error. A goal of LBS is to ensure the presence of certain properties in the source code corresponding to the safety policy of the software. Information gathered during the compilation can be used to create a certificate that can be provided to the consumer as a proof of safety in the given program. Such a proof must imply that the consumer can trust the compiler used by the supplier and that the certificate, the information about the source code, can be verified. The figure illustrates how certification and verification of low-level code could be established by the use of a certifying compiler. The software supplier gains the advantage of not having to reveal the source code, and the consumer is left with the task of verifying the certificate, which is an easy task compared to evaluation and compilation of the source code itself. Verifying the certificate only requires a limited trusted code base containing the compiler and the verifier.

Techniques

Program analysis

The main applications of program analysis are program optimization (running time, space requirements, power consumption etc.) and program correctness (bugs, security vulnerabilities etc.). Program analysis can be applied to compilation (static analysis), run-time (dynamic analysis), or both. In language-based security, program analysis can provide several useful features, such as: type checking (static and dynamic), monitoring, taint checking and control-flow analysis.

Information flow analysis

Information flow analysis can be described as a set of tools used to analyze the information flow control in a program, in order to preserve confidentiality and integrity where regular access control mechanisms come short.

"By decoupling the right to access information from the right to disseminate it, the flow model goes beyond the access matrix model in its ability to specify secure information flow. A practical system needs both access and flow control to satisfy all security requirements." — D. Denning, 1976

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Language-based security

Start with the simplest possible case. Write down what Language-based security claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Language-based security before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Language-based security ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Language-based security

In research: Language-based security appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Language-based security in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Language-based security is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cybersecurity engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Language-based security outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Language-based security in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Language-based security means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Language-based security out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Language-based security in simple terms?

Why does Language-based security matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Language-based security?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Language-based security.