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Building A Secure Software Development Life Cycle: Beginner’s Guide to Success

SDLC
27Aug, 2018

A conventional software development lifecycle (SDLC) often overlooks security testing and the testing efforts and security verification are delayed till the software product has been completely developed. However, Threats are a fledgling property in the process of software development that appears throughout the cycles of design and execution. Gradually, Uncovering a bug at the initial phase can help fix it at a cheaper expense, which makes it important to employ many processes throughout the lifecycle.

This article discusses the importance of incorporating and addressing security issues early on in the lifecycle through a process called Secure Software Development Life Cycle, which ensures software quality from the early stages of the testing process. Such efforts engage the stakeholders early on as well as throughout analysis, design, and development of each software build, which is done in an incremental fashion.

The SSDL is geared towards assuring a successful application of secure software. It has six major components:

1. Security Guidelines, Rules, and Regulations

It is important to note that security guidelines and basic rules and regulations should be taken into account at the time of the Project’s inception phase. This component of SSDL is the primary requirement. At this phase, a system-wide specification (defining the security needs which apply to the system) is generally based upon certain government regulations. In India, various corporate governance norms ensure that internal controls are put in place to curtail fraud and abuse. It is also important not only to document the security policy but also to continuously enforce it by tracking and evaluating it on an ongoing basis.

2. Document Security Requirements, Develop Attack Use Cases

One of the most common mistakes that testers usually make is omitting the security needs from the given requirement documentation. However, it is important to consider the security needs always as they aid in the development of test case, software design, and implementation. Apart from that, they even help in determining the technology choices as well as risk areas.

The security tester must make sure that the necessary security requirements are documented and described along with all the functional requirements. When you define a quality measure that is based on the requirements, you get a chance to rationalize the system’s fuzzy requirements.

Attack use cases showing unauthorized behavioural flows can also be developed. This can help in understanding and analyzing the security implications arising before and after the condition.

Some of the sample security requirements are as follows:

  • Private data is sent by the application over the net; hence, encrypting the communication is a basic requirement.
  • The application takes the input given by the user and makes use of SQL. SQL injection mitigation is a fundamental requirement.
  • The application interfaces with other trusted applications, and these connections must be validated and protected.
  • The application helps in managing the sessions for logged-in users; hence, session hijacking mitigation is one of the basic requirements.

3. Perform Architectural and Design Reviews; Identify and Define Threat Models

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The design and architectural threat and review modelling showcase the third stage of the software development lifecycle. For devising better and fully completed security plans, strategies, procedures, designs and techniques, the security practitioners often need in-depth knowledge about the design and architecture of the product. An earlier involvement of the security team can help in preventing low-security designs and insecure architectures and ensuring the elimination of misperception related to the behaviour of the application in the later phases of the project development lifecycle. Apart from that, an earlier involvement can also help the security engineers in learning about the most important and high-risk aspects of the software application.

The advantages of threat modelling are, it figures out different problems than code reviewing and test performing, and can also detect the higher-level design problems versus implementation errors. You can detect the security issues early, before coding them into product. This helps in determining the ‘highest-vulnerability parts of the application— basically those that require the most monitoring during the entire software development process.

4. Secure Coding Guidelines

Design threats are basically defects in the design that prevent the program from operating securely regardless of how perfectly it is implemented. The implementation threats are usually the result of security flaws that are caused during the coding process. Static analysis tools are used for the detection of a lot of implementation defects. These tools work by checking the program source code. They are mostly used to detect problems like buffer overflows. The results offered by these tools help the developers in learning to avoid such flaws at the very first place itself.

The software testers and developers should undertake training sessions teaching about the methods for developing secure code abiding by the general standards of secure coding. By considering the general standards of secure coding as a baseline, the testers can create test cases for verifying whether that standard is actually being followed.

5. Black/Gray/White Testing

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Setting up the test environment is a very critical aspect of the security test plan. It helps in planning, tracking and managing the activities related to setting up a test environment, where the material processes may consume a lot of time. The testing team should take care of tracking and scheduling environment setup tasks; installation of the test environment, network resources, software, and hardware; integration and installation of environment resources; refining/obtaining the testing database; and development of the scripts for environment setup.

All these include execution and refinement of the security testing scripts, implementation of evaluation tasks for avoiding both false positives as well as false negatives, documentation of security issues through system issue reports, facilitating developer learning of the software issues, the performance of regression tests, and detection of issues to closure.

6. Determining Exploitability

Ideally, all the vulnerabilities detected during the software testing process can be fixed easily. However, the effort needed for addressing them can largely vary depending on whether a particular vulnerability is a design defect or an implementation error. The exploitability of a particular vulnerability is a critical aspect of measuring the threat it avoids. This information can be used for prioritizing the remediation of the vulnerability amongst the other development needs, including implementing new functionalities and taking care of other security issues.

Conclusion

Focusing on application security throughout the software development lifecycle is most efficient and is just as important as the focus on infrastructure security. After the process is completed, the process of deploying and maintaining the application securely occurs at the end of the lifecycle. Following these steps is important to ensure secure software.