Figure I-2: Shifting/Pushing Left

About This Book

      This book will teach you the foundations of application security (AppSec for short); that is, how to create secure software. This book is for software developers, information security professionals wanting to know more about the security of software, and anyone who wants to work in the field of application security (which includes penetration testing, aka “ethical hacking”).

      If you are a software developer, it is your job to make the most secure software that you know how to make. Your responsibility here cannot be understated; there are hundreds of programmers for every AppSec engineer in the field, and we cannot do it without you. Reading this book is the first step on the right path. After you've read it, you should know enough to make secure software and know where to find answers if you are stuck.

      Notes on format: There will be examples of how security issues can potentially affect real users, with the characters Alice and Bob making several appearances throughout the book. You may recall the characters of Alice and Bob from other security examples; they have been being used to simplify complex topics in our industry since the advent of cryptography and encryption.

Out-of-Scope Topics

      Brief note on topics that are out of scope for this book: incident response (IR), network monitoring and alerting, cloud security, infrastructure security, network security, security operations, identity and access management (IAM), enterprise security, support, anti-phishing, reverse engineering, code obfuscation, and other advanced defense techniques, as well as every other type of security not listed here. Some of these topics will be touched upon but are in no way covered exhaustively in this book. Please consume additional resources to learn more about these important topics.

The Answer Key

      At the end of each chapter are exercises to help you learn and to test your knowledge. There is an answer key at the end of the book; however, it will be incomplete. Many of questions could be an essay, research paper, or online discussion in themselves, while others are personal in nature (only you can answer what roadblocks you may be facing in your workplace). With this in mind, the answer key is made up of answers (when possible), examples (when appropriate), and some skipped questions, left for online discussion.

      In the months following the publication of this book, you will be able to stream recorded discussions answering all of the exercise questions online at youtube.com/shehackspurple under the playlist “Alice and Bob Learn Application Security.” You can subscribe to learn about new videos, watch the previous videos, and explore other free content.

      You can participate live in the discussions by subscribing to the SheHacksPurple newsletter to receive invitations to the streams (plus a lot of other free content) at newsletter.shehackspurple.ca.

      It doesn't cost anything to attend the discussions or watch them afterward, and you can learn a lot by hearing other's opinions, ideas, successes, and failures. Please join us.

CHAPTER 1 Security Fundamentals

      Before learning how to create secure software, you need to understand several key security concepts. There is no point in memorizing how to implement a concept if you don’t understand when or why you need it. Learning these principles will ensure you make secure project decisions and are able to argue for better security when you face opposition. Also, knowing the reason behind security rules makes them a lot easier to live with.

The Security Mandate: CIA

The mandate and purpose of every IT security team is to protect the confidentiality, integrity, and availability of the systems and data of the company, government, or organization that they work for. That is why the security team hassles you about having unnecessary administrator rights on your work machine, won’t let you plug unknown devices into the network, and wants you to do all the other things that feel inconvenient; they want to protect these three things. We call it the “CIA Triad” for short (Figure 1-1).

Let’s examine this with our friends Alice and Bob. Alice has type 1 diabetes and uses a tiny device implanted in her arm to check her insulin several times a day, while Bob has a “smart” pacemaker that regulates his heart, which he accesses via a mobile app on this phone. Both of these devices are referred to as IoT medical device implants in our industry.

Figure 1-1: The CIA Triad is the reason IT Security teams exist.

       NOTE IoT stands for Internet of Things, physical products that are internet connected. A smart toaster or a fridge that talks to the internet are IoT devices.

      Confidentiality

      Alice is the CEO of a large Fortune 500 company, and although she is not ashamed that she is a type 1 diabetic, she does not want this information to become public. She is often interviewed by the media and does public speaking, serving as a role model for many other women in her industry. Alice works hard to keep her personal life private, and this includes her health condition. She believes that some people within her organization are after her job and would do anything to try to portray her as “weak” in an effort to undermine her authority. If her device were to accidentally leak her information, showing itself on public networks, or if her account information became part of a breach, this would be highly embarrassing for her and potentially damaging to her career. Keeping her personal life private is important to Alice.

Bob, on the other hand, is open about his heart condition and happy to tell anyone that he has a pacemaker. He has a great insurance plan with the federal government and is grateful that when he retires he can continue with his plan, despite his pre-existing condition. Confidentiality is not a priority for Bob in this respect (Figure 1-2).

Figure 1-2: Confidentiality: keeping things safe

       NOTE Confidentiality is often undervalued in our personal lives. Many people tell me they “have nothing to hide.” Then I ask, “Do you have curtains on your windows at home? Why? I thought that you had nothing to hide?” I’m a blast at parties.

      Integrity

Integrity in data (Figure 1-3) means that the data is current, correct, and accurate. Integrity also means that your data has not been altered during transmission; the correct value must be maintained during transit. Integrity in a computer system means that the results it gives are precise and factual. For Bob and Alice, this may be the most crucial of the CIA factors: if either of their systems gives them incorrect treatment, it could result in death. For a human being (as opposed to

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