I spent the last couple hours pouring over the Simplified Implementation of the Microsoft SDL. I started taking notes and making comments, and realized that I have so much to say on the topic it won’t fit in a single post. I have been yanking stuff out of this one and trying to just cover the highlights, but I will have a couple follow-ups as well. But before I jump into the details and point out what I consider are a few weaknesses, let me just say that this is a good outline. In fact, I will go so far as to say that if you perform each of these steps (even half-assed), your applications will more secure. Much more secure, because the average software development shop is not performing these functions. There is a lot to like here but full adoption will be difficult, due to the normal resistance to change of any software development organization. Before I come across as too negative, let’s take a quick look at the outline and what’s good about it.
For the sake of argument, let’s agree that the complexity of MS’s full program is the motivation for this simplified implementation of SDL. Lightweight, agile, simple, and modular are common themes for every development tool, platform, and process that enjoys mainstream success. Security should be no different, and let’s say this process variant meets our criteria.
Microsoft’s Simplified Implementation of Secure Development Lifecycle (SDL) is a set of companion steps to augment software development processes. From Microsoft’s published notes on the subject, it appears they picked the two most effective security tasks from each phase of software development. The steps are clear, and their recommendations align closely with the web application security research we performed last year.
What I like about it:
Phased Approach: Their phases map well to most development processes. Using Microsoft’s recommendations, I can improve every step of the development process, and focus each person’s training on the issues they need to account for.
Appropriate Guidelines: Microsoft’s recommendations on tools and testing are sound and appropriate for each phase.
Education: The single biggest obstacle for most development teams is ignorance of how threats are exploited, and what they are doing wrong. Starting with education covers the biggest problem first.
Leaders and Auditors: Appointing someone as ‘Champion’ or leader tasks someone with the responsibility to improve security, and having an auditor should ensure that the steps are being followed effectively.
Process Updates and Root Cause Analysis: This is a learning effort. No offense intended, but the first cycle through the process is going to be as awkward as a first date. Odds are you will modify, improve, and streamline everything the second time through.
Here’s what needs some work:
Institutional Knowledge: In the implementation phase, how do you define what an unsafe function is? Microsoft knows because they have been tracking and classifying attacks on their applications for a long time. They have deep intelligence on the subject. They understand the specifics and the threat classes. You? You have the OWASP top ten threats, but probably less understanding of your code. Maybe you have someone on your team with great training or practical experience. But this process will work better for Microsoft because they understand what sucks about their code and how attackers operate. Your first code analysis will be a mixed bag. Some companies have great engineers who find enough to keep your entire development organization busy for ten years. Others find very little and are dependent on tools to tell them what to fix. Your effectiveness will come with experience and a few lumps on your forehead.
Style: When do you document safe vs. unsafe style? Following the point above, your code development team, as part of their education, should have a security style guide. It’s not just what you get taught in the classroom, but proper use of the specific tools and platforms you rely on. New developers come on board all the time, and you need to document so they can learn the specifics of your environment and style.
Metrics: What are the metrics to determine accountability and effectiveness? The Simplified Implementation mentions metrics as a way to guide process compliance and retrospective metrics to help gauge what is effective. Metrics are also the way to decide what a risky interface or unsafe function actually is. But the outline only pays lip service to this requirement.
Agile: The people who most need this are web developers using Agile methods, and this process does not necessarily map to those methods. I mentioned this earlier.
And the parts I could take or leave:
Tools: Is the latest tool always the best tool? To simplify their process, Microsoft introduced a couple security oversimplifications that might help or hurt. New versions of linkers & compilers have bugs as well.
Threat Surface: Statistically speaking, if you have twice as many objects and twice as many interfaces, you will generally make more mistakes and have errors. I get the theory. In practice, or at least from my experience, threat surface is an overrated concept. I find that the issue is test coverage of the new APIs and functions, which is why you prioritize tests and manual inspection for new code as opposed to older code.
Prioritization: Microsoft has a bigger budget than you do. You will need to prioritize what you do, which tools to buy first, and how to roll out tools in production. Some analysis is required on what training and products will be most effective.
All in all, a good general guide to improving development process security, and they have reduced the content to a manageable length. This provides a useful structure, but there are some issues regarding how to apply this type of framework to real world programming environments, which I’ll touch on tomorrow.