This requirement was put in place to prevent use of certain older C runtime functions that lead to buffer overrun flaws and have been deprecated. In the Security Development Lifecycle book, an entire chapter is dedicated to the topic of banned function calls. In the book, we also provide a copy of the banned.h header file on the companion CD. This header file allows you to locate any banned functions in your code.

On MSDN, we have document the SDL list of Banned Function Calls, but the header file has not been publicly available outside the SDL book until now. Today, we are providing the banned.h header on the Microsoft Download Center.

Find the banned.h header here

By including this header file, then using #include “banned.h”; you will be able to locate any banned functions in your code. The full list of banned APIs is also included in the header file.

Alternately, if you are using the compiler in Visual Studio 2005 or later, you have a built-in way to check for these banned functions. To catch banned C runtime functions, you can compile with /W4 and then triage all C4996 warnings. In code reviews, you should always remove any code that disables the C4996 warnings - e.g.: #pragma warning(disable:4996). This is one simple way to ensure your code is released without banned functions.

Sanitizing your code to remove potentially insecure APIs is a vital protection. Whether you include the banned.h header file or leverage the /W4-C4996 warnings in the Visual Studio 2005 compiler, you now have two ways to check your code and meet another SDL requirement in your development phase.

Defining Cloud Computing

Cloud computing is a very active community. The Google Group gets 600 posts per month and many bloggers are covering the space. However, “cloud computing” is impossible to define in a way that satisfies everyone (or even most). Cloud computing is not alone in this controversy, consider the definition and meaning of “Web 2.0″, “mashups” or “RESTful architecture”. All of these terms are relatively recent. According to Google Trends, these terms became popular to the general public sometime between 2005 and 2007:

• Web 2.0 - often confused with RIA, AKA Social Computing, Long-Tail Apps, Crowdware (2005 by O’Reilly Media)
• Mashup - made popular by Google Maps, AKA Composite/Situational Apps. (2005)
• REST - Has a strict definition, but many don’t understand it and abuse the term. (2006 by R. Fielding)
• Cloud computing - collides with many other terms, such as SaaS, Grid, Utility, PaaS, etc. (2007)

The definition of cloud computing is in progress:

There’s a Darwinian evolution of the exact definition of cloud computing running around. We’re about a country mile away from “knowing when I see it”, which is excellent progress. The cloud to everyone’s silver-lining has enough material to write a 3 volume desktop reference at this point. - Michael Cote, June 2008

Definition #1 - “Cloud computing is the realisation of Internet (”Cloud”) based development and use of computer technology (”Computing”) delivered by an ecosystem of providers. - Sam Johnston, July 2008

Definition #2 - “Cloud computing = network computing. I love the idea of cloud computing, the next evolution of the most network intensive architecture possible, but one that if it works well, is transparent. It’s all about the transparency.” - Douglas Gourlay, Cisco, May 2008

Definition #3 - “There seems to be a group myopia around so-called “cloud computing” and its definitions. What we’re really talking about are “cloud services” of which, “computing” is only a subset…Cloud services are not SaaS. They are far more akin to web services…” - Randy Bias, neoTactics, May 2008

(Anti-)Definition #4 - “Note that I refer to cloud services, not to the could. I am not interested in defining cloud as a term, because I don’t think it’s very useful. For those of us in the distributed computing’s pace

The Working Definition (Winner!):

“…the notion of providing easily accessible compute and storage resources on a pay-as-you-go, on-demand basis, from a virtually infinite infrastructure managed by someone else. As a customer, you don’t know where the resources are, and for the most part, you don’t care. What’s really important is the capability to access your application anywhere, move it freely and easily, and inexpensively add resources for instant scalability.” - Mitchell Crandell, Rightscale, June 2008

Taxonomies of the Cloud Space

Taxonomies are useful to provide insight into a market. It classifies a multitude of players into a smaller bucket.

Andreessen’s Platforms - September 2007

Provided an early taxonomy model for emerging cloud platforms

Platform being a system that can be programmed

• Access API - platform that provides web service endpoints
• Plug-In API - platform invokes your code, that you have deployed remotely
• Runtime Environment - your code runs inside the platform’s process space.

Mehta 11 Layer Stack, April 2008

1. Facilities (space, power, cooling)
2. Network
3. Hardware (e.g. servers Amazon EC2 runs)
4. Hardware virtualization (e.g. Xen for EC2) - optional
5. O/S (e.g. Linux)
6. Systems Management (e.g., tools to manage EC2 instances)
7. Application Middleware (e.g., MySQL on EC2)
8. Application Code
9. Application APIs / Web Services
10. GUI for Application
11. GUI for Application Development / Customization

Croll Cloud Stack, June 2008

7 layer stack within Turnkey app and Generic Platform.

Turnkey app

• SaaS
• Extensible app
• Generic IDE
• Constrained APIs
• App Cluster
• Virtual Data Center
• Virtual Servers

Generic Platform

The bottom of Alistair’s stack includes “root access “style compute clouds.

Robert Anderson, July 2008

3 layer stack

• Software (SaaS)
• Platform (PaaS)
• Infrastructure (IaaS)

This is the model taxonomy for this session.

Related Concepts and Terms

• Infrastructure as a Service (IaaS), Hardware as a Service (HaaS) are synonyms to cloud infrastructure.
• Virtualization
• Hosting
• Autonomic computing
• Distributed computing
• Grid computing

Cloud Applications

• SaaS
• S+S (Software+Services)
• Managed Service Provider (MSP)

Introduction

Virtualization is a word used by consumers and also by IT. But, do we all mean the same thing?

A very cool video from Cisco provided answers to “what is virtualization” from an  engineering perspective, data center perspective, IT perspective and the user perspective (virtual world).

Virtualization is about breaking the bonds between applications and server hardware, nodes and networks, applications and operating systems.

Why is this interesting? Virtualization holds the promise to transform the way we work, live, learn and play.

Why virtualize?

The real estate boom over the last 30 years has driven people to the suburbs. People didn’t mind commuting for an hour with lower gas prices. Today, we have a weak economy and gas prices are high. Something has to change.

Many are opting to stay at home. Businesses are trying out telecommuting, some (like Cisco) are even offering telepresence. This helps by reducing carbon footprint. Corporations are breaking free from physical requirements. The global workforce is also having an impact on the network. These changes are having a huge impact on the network.

We are on the cusp of transitioning from virtualization to VIRTUALIZATION.

“One to many….many to one.”

This is Cisco’s idea of virtualization.

Consider the different roles we play in life - one to many. Spouse, executive, friend, parent, gym rat. This would be “one to many”. This is exactly what virtualization does. It allows you to partition resources off that you can use on the fly.

Where do I start?

Virtualization starts with server and storage. But, it’s the network that touches everything - it spans the physical, the virtual, and the cloud. This provides the connectivity to all these resources. The network brings transparency to the picture. It allows you to better monitor performance and better implement security - great benefits!

Why do I need this?

At Cisco, we saw that we were only using 20% of our storage utilization. We wanted to virtualize our datacenters. When we did that, we were able to get 68% storage utilization. For each year that we were able to defer buildup, we saved $40 million.

From a business standpoint, virtualization helps you differentiate and work faster. Provisioning in minutes, improved productivity and competitive differentiation, using less power (environmental impact), and up the ante of business continuity. If VMWare fails? It’s OK. You can reprovision it on the fly.

Is it for everyone?

IT organizations tend to be siloed. You have the IT side and the Operations side. Each has responsibility. For virtualization to work, these walls have to come down. The concept of virtualization depends on shared resources.

Metcalfe’s Law of the Network Effect

Everytime you add a node to the network, you increase the value. This is what happens with virtualization. Every device you virtualize increases the power of each device. More control of environment and more efficiency.

This leads to…

Cloud computing.

Wow, show of hands from the audience when Marie asked “how many are using cloud computing?” and “how many are using your own clouds?” - not a lot of hands were raised. Interesting considering the coverage cloud computing has and the focus of it.

Cloud computing has three possibilities at Cisco:

• Flexible infrastructure (hosting)
• Abstract services (APIs)
• Application services (SaaS)

Automation is going to be key, and will need to integrate virtualization-aware elements.

Can you imagine if you wanted interoperability in the cloud? People haven’t even begun thinking about it.

Conclusion

As you virtualize, your role will change. You will think more about strategy. But keep in mind these “minefields” of virtualization:

• Insufficient planning
• Lack of standards
• Weak security

Security cannot be an afterthought. It has to be planned. We’ve seen new forms of malware, hypervisor attacks, and root kit infections.

As higher expectations from end users evolve, we’re becoming not server oriented, but SERVICE oriented.

Tips:

• Think holistically
• Consider IT culture - equipment and people

For those of you who aren’t familiar with XSS Filter, a brief summary is that it is a client-side defense against reflected cross-site scripting (XSS) attacks.  It works by recognizing that reflected XSS attacks inject script into the string that the browser sends to the targeted web server.  If the server doesn’t neuter or strip out the injected script, it gets sent back to the browser and executed in the context of the target web page.  Bad things then happen.  At a high level, XSS Filter remembers the string that the browser sent to the server, and looks at the server’s response to see if any of the script was actually in that string.  If it was, then XSS Filter decides that it got there because it was injected by an XSS attack and blocks the script from executing.  The rest of the web page renders as usual.  This is a vastly oversimplified sketch of XSS Filter – for details, see the post by David Ross, inventor of XSS Filter on the Security Vulnerability Research and Defense blog.

So what does XSS Filter have to do with the SDL?  Well, for almost nine years, since XSS was first discovered at Microsoft, we’ve been trying to figure out effective ways to reduce vulnerability to XSS attacks.  Our focus has been on improving the ways that web page developers code their pages, and we’ve developed a lot of tools and techniques for making web content safer from XSS attacks and for detecting XSS vulnerabilities in live pages.  The SDL requires the use of many of these tools and techniques, and we’re sure we’ve prevented a lot of XSS vulnerabilities from being introduced into Microsoft web pages as a result. 

But while we identify (and the SDL requires) measures that allow developers to avoid classes of vulnerabilities, we also look to identify more sweeping solutions that can either 1) eliminate classes of vulnerabilities, 2) reduce their severity, or 3) reduce the likelihood of attacks being successful.  The process usually starts from deep understanding of a class of vulnerabilities and attacks, and then we broaden defenses from there.  In the case of XSS Filter, David’s years of work researching XSS led him to come up with an approach that blocks many of the most common vulnerabilities to reflected attacks found on the web today.  The solution is compatible with existing web pages (doesn’t “break the web”) and thus we were able to enable it by default for users of Internet Explorer 8.  Because it’s a client-side mitigation, it will help protect users from attacks even though the sites they visit may be vulnerable to XSS. 

Our work on buffer overrun defenses follows a somewhat similar pattern – we started by prescribing coding techniques, banning the use of some APIs, and building tools that detect coding constructs that look like buffer overruns.  As we gained a deeper understanding of how buffer overruns can be exploited, we enhanced the /GS compiler flag and added ASLR in a quest to cause classes of exploits to fail even if a buffer overrun remains.  We’re not yet close to eliminating the SDL requirements for use of tools and coding techniques, but the SDL also requires the use of the mitigations to reduce the severity of vulnerabilities that slip past.  Will we ever get to the point where the mitigating technologies are so strong that we can relax the coding requirements?  Maybe not, but we will continue to introduce technologies that reduce the chances of a successful attack.

Similarly, in the case of XSS, even after IE8 ships, the SDL will continue to require the use of safe web site coding practices and tools such as the Anti-XSS library both to protect users of browsers other than IE8 and to provide protection in recognition of the fact that XSS Filter is a mitigation or defense in depth rather than a complete solution.  But we’ll also be keeping our eyes open (and doing active research) in the quest for an even more effective defense – whether client or server side – that eliminates XSS for good.

This post is a little far afield from the normal content of the SDL blog, but I thought it was important to provide a picture of the role of security science and security research in defining SDL requirements and in making major improvements in software security.  You can read more about our work in security science in the Security Vulnerability Research and Defense blog.

During the presentation I mentioned in some depth how to perform fuzz testing, and what parts of an application should be fuzz testing targets. I also introduced an idea (that's not new) to help people who have never performed fuzz testing begin fuzz testing with very little cost and friction. The idea is to add a small layer of code to an application to automatically mutate untrusted data as it comes into an application; I called that code layer "a layer of hurt."

Before I continue, I want to point out that fuzzing is an SDL requirement, but the idea in this blog post is not an SDL requirement, it's just another way to help meet SDL fuzzing requirements.

Adding a layer of hurt, as shown in the picture below, is pretty simple as it involves adding code to an application to tweak data as it comes into an application. You can work out where to place the fuzzing code by looking at your threat models to see where data crosses trust boundaries. You could also simply grep the code looking for APIs that read data, for example:

• Read from files: fread, ReadFile
• Reading from sockets: recv, recvfrom
• For .NET code, any stream.Read

You get the picture.

The fuzzing code should appear right after the API that reads that data.

For example, C or C++ code that reads from a UDP socket and then fuzzes the data before it's consumed by the rest of the application might look like this:

Or, in C#, code that reads from an untrusted file:

In both code examples, Fuzz() mutates the incoming data. In the C++ case, the fuzzing code looks like this:

The sample C# and C++ fuzzing code is available as a ZIP file at the end of this post.

This code is an example of dumb-fuzzing, which is fuzzing with little or no regard for the data structure being manipulated. If you've never performed any kind of fuzz testing in the past, then you will probably find bugs with this simple fuzzing technique. Once you have weeded out the low-hanging bugs, you may need to turn your attention to smarter fuzzers. For example, in theory, this code would find few if any bugs in a PNG parser, because PNG files have a built in check-sum, so if you fuzz a PNG file, you'd have to recalculate the checksum to get decent code coverage.

When I showed this code during my presentation, I urged people to add it to their applications today if they currently don't do fuzz testing, and simply run their applications through their normal testing processes. Within three days of my presentation I received emails from people saying they had found bugs. I have no doubt others did too.

One of the comments I made during the session was,"If you can't spend the time on great fuzzing, fuzz anyway" and adding a "layer of hurt" is a reasonable start.

Please feel free to sound off if you have ideas to help improve the code and let us know what you think, either through email or comments to this post.

This blog gives us a place to talk about our experiences from using the SDL here at Microsoft and hopefully provide useful information that will help you implement it more effectively at your company.  So, I would encourage you to use the Comments section at the bottom of each post to ask questions, give us feedback, or request other topics for us to cover.

Some quick definitions before we dive in. I’ve been using the imagery of learning to “crawl, walk and run” as a way to provide some basic starting points that would move your organization toward implementing the Security Development Lifecycle (SDL).  “Walking” is the point where your security development practices become a lifecycle – a repeatable, reusable process that makes security a part of your development culture. To relate the analogy to SDL a bit more closely, think of crawling as the “SD” in SDL. For this post, we’ll continue to talk about walking – or adding the “L” in SDL.

Let’s jump into another component for adopting the Microsoft SDL to expand your own Security Development Lifecycle.

Expand Security Training

Once you have management approval, it is necessary to gain grassroots acceptance of the changes – at the developer, QA/test, and PM levels. If you have been “crawling”, you have probably already implemented some sort of discipline-specific training around things like threat modeling, using compiler defenses, and fuzz testing. Now that you are building a lifecycle, your goal for security training should expand. Security training should be about creating an environment where writing secure software is everyone’s mission. While security training should be undertaken with the goal of understanding security issues and how to address them, good training (and instructors) will also explain why solving security problems is in their best interests and create an environment where they know voicing security concerns is encouraged.

Training has been one of the earliest and most important elements of the SDL at Microsoft. From our experience, we learned that the most effective approach is to divide your training into two tracks: general security principles and role-specific security practices. Before I jump into the details, I want to encourage you to also read Shawn Hernan’s very good post about SDL training that highlights some of the ways to make security training effective.

The general security principles should explain why security is important, how you define security requirements, the process you will use for writing and validating secure code, and how security relates to each phase of the lifecycle or unique roles contributing to the development process. A key factor for building a development lifecycle is educating your individual contributors on the value of investing in security. Of course changing culture takes time, but using the opportunity of structured training to explain your principles will be one of your most effective platforms for influencing change.

At this point in your organizational maturity, you are also beginning to expand your security thinking by focusing on each role in the development process. Discipline-specific security training is where you dig into the details of implementing a Security Development Lifecycle.

·         The developer needs to understand the practical details of how to write code securely, how to set compiler flags, what a security code review means, how to avoid using banned APIs, and what tools are available for them to perform security analysis before checking in their code.

·         The QA/tester needs to know how to set security rules in test tools, how to perform penetration testing, and what the security quality criteria is for your product, or how to file a security bug.

·         The PM needs to understand how to define measurable goals or how security policies can be factored into feature design.

·         The business decision maker of your organization should understand how to track security metrics alongside other product measurements or how security policy plays a critical role in the overall quality and value of your product.

·         Finally, it is critical for the employees occupying all job roles to understand the value of threat modeling – both as a tool for understanding threats early in the design phase and throughout the development process as a key barometer to the security pulse of your product.

Discipline-specific training will be the place to address these issues for your organization. In case you were wondering, all job roles should be required to attend both types of security training before working on your product.

Our new SDL website [http://www.microsoft.com/sdl] will be a very good place to watch for future training materials. The SDL Training and Resources page has some useful material up now and more will be coming in the future.

That’s Part Two. In Part Three, I will discuss the important “walk” components of formalizing security requirements and reusing threat models and attack surface reviews. Then we will close with the discussions on conducting final security reviews, and managing post-release documentation.

I’d like to hear if anyone is using the concept of “crawling” and “walking” to implement SDL in your company.

?        Do you provide security training to your employees today?

?        Do these additional training topics make sense in your organization?

?        What would you add to this that is unique to your application or company?