Code Review Approach
When planning to execute a security code review, there are multiple factors to consider since every code review is unique to its context. Some of these elements are further discussed in the following sections. In addition, consider also unique factors that might impact the analysis. These factors among others, might ultimately decide the course of the code review and the most effective way to execute it. Some are technical but others are related to business decisions such as deadlines and resources
It is impossible to secure everything at a 100 percent, furthermore it is essential to prioritize what features and components must be reviewed. In addition, we need to assess the kind of risks and the business priorities. Code review based on risk based assessments provides effectiveness to the analysis
Purpose & Context: focusing on risks
Computer Programs have different purposes, consequently the grade of security will vary depending for what it was built. A payment web application will have higher security standards than a promotional website. One must ask: what do we want to protect? In the case of a payment application, data such as credit cards has the highest priority however in the case of a promotional website, one of the most important things to protect, for example, is the connection credentials to the web servers. This is another way to place context into a risk based approach.
Are we reviewing Spaghetti code or a properly created Object Oriented Program? Is the program using a clear defined pattern or is it necessary to spend time to understand what the developer built? Complexity comes in many forms, the more difficult is to understand the program the more difficult it becomes to spot issues in it. Therefore, try to determine the grade of difficulty involved and especially, how much time it will take to clearly define the duration of the review. The next item increases the complexity ratio in software development.
Lines of Code
In order to properly asses the amount of work, an indicator of this property is the number of lines of code that must be reviewed. IDEs (Interface Development Environments) such as Visual Studio or Eclipse contain features which allows us to verify the amount of lines a class has. Programs written in high level languages are divided in classes and each class is equivalent to ‘pages’ full of code. Also the exact line number helps us to pinpoint the exact location of the code that must be corrected and it is very useful when reviewing corrections done by a developer, such as the history in a repository. The more lines of code a program contains, the more are the chances that errors are present in the code. A calculation based on statistics is to take the value of 5 to 50 bugs per KLOC (Thousand lines of code). Most commercial software will contain 50 bugs per KLOC (Hoglund and McGraw, 2004) When doing a code review, keep in mind this factor which can help determine the potential amounts of bugs present in the program
Programs written in typed safe languages (such as C# or Java) are less vulnerable to certain security bugs such as buffer overflows than others that are not, like C and C++. When executing code review, the kind of language will determine the types of expected bugs. Throughout this guide, you can find the most common issues surrounding the specific programming language code to be reviewed, use this as a reference to spot specific security issues in the code.
Resources: Time & Deadlines
This is a fundamental factor. A proper code review for a complex program might take longer and it will need higher analysis skills than a simple one. System owners might expect to finish and use less time to execute the code review than it actually needs. The risks involved if resources are not properly provided are high. Make sure that this is clearly asses when executing a review.
Hoglund & McGraw, 2004 “Exploiting Software How to Break Code” –Addison Wesley