I find that legacy code poses a unique challenge for organizations rolling out a new security process.  Often, the resources dedicated to maintaining older code are a small fraction of those devoted to new features or products.  Furthermore, the original developers for such features have often moved on, leaving no subject matter experts to drive reviews.  The astute reader will ask “How do I apply the principles of the Microsoft SDL to legacy code when I have no development resources and nobody knows how it works?”

The answer is “Start small, and build expertise over time.”

A Rising Tide Lifts All Boats

The best thing a security engineering team can do to improve security in the short term is to drive code quality, and the first step in this process is to define and enforce a secure coding standard.  This helps on two fronts: 

1.       It will improve code quality and reduce implementation flaws across the entire code base.  Unlike other security processes, driving a secure coding standard is relatively easy to accomplish across an entire code base, regardless of the code’s age, by a focused security team.  That is not to say that it is easy without qualification – a large batch of spaghetti code will require a lot of work to untangle!  Such an effort can only be called “easy” when compared to, say, comprehensive identification and remediation of design flaws across legacy features.  Even so, improving code quality through the use of secure coding standards offers a unique combination of high impact, applicability to features, and ability to be carried out by a core team that makes it a sensible first step.

2.       The security team might notice that some sections of code have more standards violations or outright flaws than others.  This is an instance of vulnerability clustering, a concept that has been used to predict vulnerability rates and improve quality in the functional realm.  The evidence is anecdotal, but it stands to reason that portions of code that consistently violate secure coding standards are good places to start looking for other classes of security flaw.  These are security hotspots, and should be high on the prioritized list for further review.

Security testing may also be applied to legacy code, but initial activities should be considered on a case-by-case basis based on the expected return on investment.  Such testing ranges from using inexpensive off-the-shelf tools to exercise common interfaces to rather expensive custom testing and formal analysis.  It is worthwhile to begin with off-the-shelf tools, such as those that target file parsers or web applications, and tools created as part of your greater secure development efforts.  These can help identify easily-found flaws and suggest improvements to the coding standards.  Comprehensive security testing, on the other hand, is best tackled after the Legacy Security Push.

The Legacy Security Push

Coding standards and basic testing provide bang for the buck, but formal security processes seek to provide security assurance.  The challenge for legacy code is that it needs to play catch-up.  Security processes that occur early in the development cycle, such as requirements analysis, design review, and threat modeling, are particularly difficult to achieve years after the fact.  The main goal of the Legacy Security Push is to create the deliverables from these efforts, the most important of which are security requirements and a full risk analysis.

It may sound trivial, but security requirements are essential.  Not only do they define proper operation for the system in question, they also define assumptions that are suitable for relying systems.   It is very common to find security flaws in legacy systems that arise from well-intentioned but incorrect assumptions such as “I assume that the Foo authenticates server Bar when initiating a bank transfer.”  It stands to reason that Foo would do so for such an important activity, but this assumption must be validated.  It is very common for older features to have been deployed in and written for different environments where the security assumptions that are "obvious" today just didn't apply at the time.

When reviewing legacy systems, the first step is to identify such requirements.  If the original architects, developers or managers are available, they can provide valuable insight at this stage.  More often than not this is not the case, and analysis must instead rely on what documentation is present and interaction between the software and its consumers.  The goal is the same as in requirements analysis during project inception, except that in this case one must turn the process on its head and reverse engineer requirements from system behavior.  At the conclusion of this effort, requirements can be theorized – “Foo must authenticate its server Bar before initiating a bank transfer.” 

Risk analysis can be performed once a plausible set of requirements have been identified.  Threat modeling is a more structured means of performing such an analysis, with the eventual goal of identifying means by which requirements can be violated by an attacker. 

As with requirements analysis, original developers would be a valuable resource to consult.  With or without such help, the first step is to identify how the software works.  In many cases, help is not available and performing this task requires a great deal of effort.  For features of moderate size, this author has spent upwards of a month reading code, using process profiling tools, and walking through the software with a debugger to identify program flow and security-sensitive functionality.

Once completed, actual system behavior should be documented and compared against the requirements theorized.   It might be that the requirements should be re-evaluated (New requirement:  Do not assume that Foo requires server authentication) or the system may need to be changed (New bug:   Foo does not verify the CN for Bar).  At the end, this information should be sufficient to support a comprehensive threat modeling exercise where security requirements, risks, and their mitigations can be documented.

Next Steps

Bringing a legacy feature up to par with its newer kin requires a relatively small number of items:  improved code quality, clear security requirements, and a thorough threat model.  As we have seen, performing even these tasks is quite the effort!  I am sure that it is little comfort to be reminded that accomplishing these tasks has simply laid the foundation, and that the true benefit is that the newly-reviewed legacy feature is able to participate fully in the security processes that remain: reviewing cross-component security requirements and assumptions, comprehensive testing, and incident planning, to name a few.

Unfortunately, there is no silver bullet in security assurance.  The soundness of the design and implementation of legacy software is just as important as in newer software, which is why any complete secure software development process will look backwards as well as forwards.  Feature by feature, from higher priority to lower, the overall security of the software improves as legacy code receives the full security treatment it deserves.

No doubt you are aware of the out-of-band security bulletin issued by the Microsoft Security Response Center today, and like all security vulnerabilities, this is a vulnerability we can learn from and, if necessary, can use to shape future versions of the Security Development Lifecycle (SDL).

Before I get into some of the details, it's important to understand that the SDL is designed as a multi-pronged security process to help systemically reduce security vulnerabilities. In theory, if one facet of the SDL process fails to prevent or catch a bug, then some other facet should prevent or catch the bug. The SDL also mandates the use of security defenses, because we know full well that the SDL process will never catch all security bugs. As we have said many times, the goal of the SDL is to "Reduce vulnerabilities, and reduce the severity of what's missed."

In this post, I want to focus on the SDL-required code analysis, code review, fuzzing and compiler and operating system defenses and how they fared.

Code Analysis and Review

I want to start by analyzing the code to understand why we did not find this bug through manual code review nor through the use of our static analysis tools. First, the code in question is reasonably complex code to canonicalize path names; for example, strip out ‘..' characters and such to arrive at the simplest possible directory name. The bug is a stack-based buffer overflow inside a loop; finding buffer overruns in loops, especially complex loops, is difficult to detect with a high degree of probability without producing many false positives. At a later date I will publish more of the source code for the function.

The loop inside the function walks along an incoming string to determine if a character in the path might be a dot, dot-dot, slash or backslash and if it is then applies canonicalization algorithms.

The irony of the bug is it occurs while calling a bounded function call:

_tcscpy_s(previousLastSlash, pBufferEnd - previousLastSlash, ptr + 2);

This function is a macro that expands to wcscpy_s(dest, len, source); technically, the bug is not in the call to wcscpy_s, but it's in the way the arguments are calculated. As I alluded to, all three arguments are highly dynamic and constantly updated within the while() loop. There is a great deal of pointer arithmetic in this loop. Without going into all the gory attack details, given a specific path, and after the while() loop has been passed through a few times, the pointer, previousLastSlash, gets clobbered.

In my opinion, hand reviewing this code and successfully finding this bug would require a great deal of skill and luck. So what about tools?  It's very difficult to design an algorithm which can analyze C or C++ code for these sorts of errors.  The possible variable states grows very, very quickly.  It's even more difficult to take such algorithms and scale them to non-trivial code bases. This is made more complex as the function accepts a highly variable argument, it's not like the argument is the value 1, 2 or 3! Our present toolset does not catch this bug.

Ok, now I'm really going out on a limb with this next section.

Over the last year or so I've noticed that the security vulnerabilities across Microsoft, but most noticeably in Windows have become bugs of a class I call "onesey - twosies" in other words, one-off bugs. There is a good side and a bad side to this. First the good news; I think perhaps we have removed a good number of the low-hanging security vulnerabilities from many of our products, especially the newer code. The bad news is, we'll continue to have vulnerabilities because you cannot train a developer to hunt for unique bugs, and creating tools to find such bugs is also hard to do without incurring an incredible volume of false positives. With all that said, I will add detail about one-off bugs to our internal education; I think it's important to make people aware that even with great tools and great security-savvy engineers, there are still bugs that are very hard to find.

Fuzz Testing

I'll be blunt; our fuzz tests did not catch this and they should have. So we are going back to our fuzzing algorithms and libraries to update them accordingly. For what it's worth, we constantly update our fuzz testing heuristics and rules, so this bug is not unique.

Defenses

If you want the full details of the defenses, and how they come into play on Windows Vista and Windows Server 2008, I urge you to read teh SVRD team's in-depth analysis once it is posted.

A big focus of the SDL is to define and require defenses because we have no allusions about finding or preventing all security vulnerabilities by attempting to get the code right all the time, because no-one can do that. No one.  See my comment above about one-off bugs!

Let's look at each SDL mandated requirement and how they fared in light of this vulnerability.

-GS

The -GS story is not so simple. A lot of code is executed before a cookie check is made and the attacker can control the overflow because the overflow starts at an offset before the stack buffer, rather than at the stack buffer itself. So the attacker can overwrite other frames on the call stack, corresponding to functions that return before a cookie check is made. That's a long way of saying that -GS was not meant to prevent this type of scenarios.

ASLR and NX

The code fully complies with the SDL, and is linked with /DYNAMICBASE and /NXCOMPAT on Windows Vista and Windows Server 2008. There are great defenses when used together, and reduce the chance of a successful attack substantially. Also, the stack offset is randomized too, making a deterministic attack even more unlikely.

Service Restart Policy

By default the affected service is marked to restart only twice after a crash on Windows Vista and Windows Server 2008, which means the attacker has only two attempts to get the attack right. Prior to Windows Vista, the attacker has unlimited attempts because the service restarts indefinitely.

Authentication

Thanks to mandatory integrity control (MIC) settings (which comes courtesy of UAC) the networking endpoint that leads to the vulnerable code requires authentication on Windows Vista and Windows Server 2008 by default. Prior to Windows Vista, the end point is always anonymous, so anyone can attack it, so long as the attacker can traverse the firewall. This is a great example of SDL's focus on attack surface reduction; requiring authentication means the number of attackers that can access the entry point is dramatically reduced.

Firewall

We enabled the firewall by default in Windows XP SP2 and later, this was a direct learning from the Blaster worm. By default, ports 139 and 445 are not opened to the Internet on Windows XP SP2, Windows Vista and Windows Server 2008.

Summary

The $64,000 question we ask ourselves when we issue any bulletin is "did SDL fail?" and the answer in this case is categorically "No!" No because as I said earlier the goal of the SDL is "Reduce vulnerabilities, and reduce the severity of what you miss." Windows Vista and Windows Server 2008 customers are protected by the defenses in the operating system that have been crafted in part by the SDL. The development team who built the affected component compiled and linked with the appropriate settings as described in "Windows Vista ISV Security" and Writing Secure Code for Windows Vista so that their service is protected by the operating system.

The team did not poke holes through the firewall unnecessarily, in accordance with the SDL.

The team reduced their attack surface, in accordance with the SDL, by requiring authenticated connections rather than anonymous connections by default.

We know that the SDL-mandated -GS has very strict heuristics so some functions are not protected by a stack cookie, but in this case, there is no buffer on the stack, so there will be no cookie. We know this. There are no plans to remedy this in the short term.

Fuzzing missed the bug, so we will update our fuzz testing heuristics, but we continually update our fuzzing heuristics anyway.

In short, based on what we know right now, Windows Vista and Windows Server 2008 customers are protected because of the SDL-mandated defenses in the operating system, and because the development team adhered to the letter of the SDL to take advantage of those defenses.

Chalk one up for Windows Vista and later and the SDL!

As usual, questions and comments are very welcome.

Partial Disclosure - The Good

The responsible disclosure process tends to break down in rare occasions where the vendor doesn’t want to fix the issue. When this occurs, the researcher is put into a difficult position whereby full disclosure could put users’ systems at high risk of compromise. The other case where partial disclosure becomes an alternative is when the researcher has discovered a design flaw in a protocol or underlying multiple vendor component. Examples of this case include the DNS flaws published this past summer by Dan Kaminsky and the TCP denial of service condition discovered by Robert E. Lee and Jack Louis that is currently in the disclosure process. When the flaw affects a very large number of vendors and the actual problem is located within the underlying protocols that support the communications of the Internet as a whole, one possible solution is to follow a partial disclosure model where phasing the details to the general public can be used to encourage adoption and creation of patches throughout the enormous target audience.

Partial Disclosure - The Bad

What is driving the fear surrounding partial disclosure is the potential for abuse. When a major flaw is partially disclosed, a number of potential issues may occur. First and foremost, the further along the partial disclosure path we are, the more details will be released to the public, and the higher the probability that someone (either good or bad intentioned) will figure out the exploit and disclose the details. Second, when partially disclosing, the vendor’s hand is being forced into a situation that could speed up fixes, reduce testing, and cause ripple problems elsewhere within the infrastructure. It is difficult enough to dance the fine time line when doing responsible disclosure, but if we are escalated to the point of partial disclosure, additional fuel is added to the fire.

The Ugly

The real ugly part of partial disclosure is when we add to the equation the ability to spread fear, uncertainty, and doubt into the normal user community. It is generally well accepted that FUD can be used to drive additional revenue. If it is possible to increase the perceived magnitude of the “problem” that your product or service solves, it is possible to directly impact the demand for that product or service. That is the major fear imposed by the growing trend of partial disclosure. By releasing just enough information to trigger wide scale speculation into the flaw, it is possible to create buzz and garner media attention resulting in a lot of speculation and very little hard facts around the issue. The potential for abuse by the security industry at large is enormous.

The Fix

Some have suggested a group of security researchers be convened to vet the requirement of partial disclosure and to allow for independent peer review of any security research that requires the partial disclosure process. This suggestion leaves questions regarding who would stand on this group and who would be impartial enough to ensure that the right thing was always done regardless of profit potential. It also leaves open the opportunity for member researchers to utilize the information gathered during the vetting process to position themselves to profit from the data upon release. It might be wiser to rely on a higher level authority or government entity to manage this process and use the services of security researchers as required for subject matter expertise. While a group of this type wouldn’t ensure that all partial disclosure is appropriate, it would hopefully limit the potential for abuse and the ever present chance that people try to profit from the FUD that surrounds the current partial disclosure process.

TECHNOLOGY AREAS: Air Platform, Information Systems, Space Platforms, Human Systems

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Develop visualization techniques for planning and execution of Cyberspace operations.

DESCRIPTION: Fulfilling the Air Force mission “… to fly and fight in Air, Space, and Cyberspace” requires effective C2 tools for the observation, planning and execution of cyberspace operations. Conventional battlespace visualization tools were developed for the physical world (i.e., geospatially oriented), where the battlespace, weapons and effects are concrete, often observable entities. Cyberspace and its critical electronic infrastructures are an artificial world that must be created, modified and sustained by the warfighter. This artificial world of cyberspace has concrete links back to the physical world that shape the information landscape, affect the decision-making process, and control the communication channels crucial to C2.

Standard, geospatially oriented C2 tools are not suitable for providing cyber combatants with comparable situation awareness to understand events, evaluate options, and make decisions in the electromagnetic domain. The combatants in the cyber domain needs to be able to quickly see and understand not just the physical relationships of the traditional battlespace, but also the logical relationships and information dependencies in the abstract landscape of cyberspace. Cyber C2 visualizations need to provide information for strategy, tactics and execution of effects that may, or may not, have physical correlates. Examples of these cyber events include network attack detection, attack identification, damage assessment, denial of service (DOS) warnings, and information warfare or cyber-attack operations.

For example, a commander may be planning to intentionally disrupt a portion of his network to investigate a cyber-attack. He will need to understand what ripple effects will occur across the functionally diverse and geographically distributed network. These ripple effects will have both a cyber component (e.g., locations that will lose connectivity or suffer degraded performance characteristics) and a real-world component (e.g., information about enemy forces may be unavailable or delayed, reducing blue force effectiveness) that must be visualized, explored and tasked from within his C2 tools.

Decision makers will greatly benefit from innovative visualization tools that can improve their understanding of all aspects of the Cyber domain. These aspects include 1) the current state of the information environment, the physical and virtual battlespace and enemy and friendly capabilities and vulnerabilities; 2) the scope and scale of courses of action that affect information or information networks; 3) the primary effects and ripple effects of an operation in both the physical and cyber battlespaces, and 4) the risks for collateral damage associated with cyber warfare activities.

PHASE I: Identify cyberspace characteristics relevant to C2 visualization. Identify correlation methods and visualization techniques to understand battlespace, operations, and effects. Define metrics to evaluate efficacy. Document results in a written report, including mockups of proposed visualizations.

PHASE II: Construct a working prototype to demonstrate integrated visualization of cyber data showing 1) the status of information environment, 2) its effect on the conventional battlespace, and 3) the status of information operations. Evaluate effectiveness using metrics defined in Phase I.

PHASE III / DUAL USE: Military application: Additional military applications include command and control environments, like the Air Operations Centers (AOCs). Commercial application: Monitoring and defending infrastructures (e.g., financial and energy) against cyber-attacks. Visualization cyberspace is beneficial for security of commercial communication and information networks.

REFERENCES:

1. ‘Air Force leaders to discuss new ‘Cyber Command’

2. Laura S. Tinnel, O. Sami Saydjari, and Joshua W. Haines, An Integrated Cyber Panel System, IEEE Computer Society,

3. Anita D’Amico and Stephen Salas, Visualization as an Aid for Assessing the Mission Impact of Information Security Breaches, IEEE 2003.

4. Tim Bass, “Cyberspace Situational Awareness Demands Mimic Traditional Command Requirements,” AFCEA Signal Magazine, February 2000.

KEYWORDS: visualization, cyber, human factors, planning, situation awareness, command and control, HCI

Reference. SITIS Topic Details, Visualization for Command and Control of Cyberspace Operations

See also:  http://www.dodsbir.net/solicitation/sbir083/af083.doc

Here we talk to John Proctor, who started out as one of our first customers (and the first MSP customer). And he believed in it so much, he eventually became part of the ScienceLogic team. (Remember “I’m not only the President, I’m also a client” from the Hair Club for Men?)

John shares his perspectives about the service provider world and why he took a chance on a little-known product called EM7.

ScienceLogic: What is your background? How many years have you worked as a service provider and for what types of companies?

John Proctor: I have been working with Service providers for over twelve years. I worked at a major regional service provider for six years and before that I designed and built national and international networks for ISP’s and Fortune 500 companies as a consultant for PriceWaterhouseCoopers and WorldComm.

ScienceLogic: You were one of the first customers of EM7 – why did you choose it and how did you get over the hurdles associated with using a start-up company’s product?

John Proctor: We were actually customer number five. Back in 2004 when we evaluated and purchased EM7 we could see that EM7 provided about 80% of what we were looking for in one integrated solution right out of the box. One of the things that sold us on EM7 was that the ScienceLogic founders had all previously worked for a service provider, so we knew they understood our business and our challenges. But in the end, it comes down to features. Once we compared EM7 functionality to the alternatives, it was clearly a “no brainer.”

ScienceLogic: What other alternatives were being considered?

John Proctor: Well, we had started with a few point solutions, but as our business and product offerings matured, this resulted in a growing number of point solutions. What started with 3 or 4 ended up as 14 separate tools. They all had strengths but what they didn’t have was integration and because of this they could not scale. And, if the tools could not scale, our business could not grow.

So, naturally we started looking at framework solutions, but they are expensive to buy, expensive to implement, and expensive to maintain. At one point, we even considered some open source projects. There were several that showed promise, but we would still be stuck with tools that were not integrated. So then we considered hiring developers to cobble something together that would work for our business. The only problem with this alternative was that we felt it would take 6 to 8 months before we could have something viable to work with.

ScienceLogic: What products were you using before EM7? What were your goals?

John Proctor: Before we purchased EM7 we used 14 different point solutions to deliver our products and services to the marketplace. Tools like NetCool, Openview, Argent, Heat, What’s Up Gold as well as several other point solutions, vendor specific applications and manually updated spreadsheets. And, as I mentioned before, this does not scale. This also adds a great deal of complexity when you begin to consider business continuity and disaster recovery. All these tools were vital to the delivery of our products and services. Any service provider will tell you it is all about uptime. So if the product is uptime, the tools used to deliver it have to be available 24×7x365.

Our goals were simple: scale and redundancy. As it turns out, the solution was simple as well. EM7 provided a tool that could replace the functionality of almost half of the existing point solutions and the applications that could not be replaced were integrated with EM7 to provide our staff with a “single pane of glass” to see the status and performance of each area of the business from one application. We had visibility into everything from facility systems to applications using EM7.

ScienceLogic also delivers an extensible configuration that addressed uptime and redundancy. We deployed collectors throughout our network that reported back to a central pair of redundant database servers and with this configuration we were able to perform backups and add capacity without taking the system down.

ScienceLogic: Why are service providers different from enterprises? How are their needs different?

John Proctor: First and foremost, service providers face the same challenges that only the largest enterprises ever face and they also have many unique challenges that only service providers experience.

One challenge we faced was that we had multiple datacenters in different states. They were all interconnected with plenty of bandwidth between each site, but the tools were not designed to be used across the WAN. Our staff in our remote data center did not have the same access as our staff in the corporate office. Since EM7 is web-based, it immediately eliminated this problem.

Another challenge is that service providers must manage systems across multiple domains. Back in the early version of a specific tool we were using before EM7, the only way you could implement it across multiple domains was to put the same username and password on every computer that you monitored. Beyond the security concerns, maintenance was a nightmare. Anytime we had to change the password, we would get locked out of dozens upon dozens of systems. When the password was changed on the monitoring server, it would attempt to login to the remote machines and fail. Repeated attempts would result in the account getting locked. I think that vendor eventually addressed this issue, but service providers seldom find tools that were designed for their unique situations.

ScienceLogic: How is EM7 geared to service providers?

John Proctor: Enterprise IT is a trusted part of the business; they are one of the team. Service providers are outsiders that must earn trust by showing the customer exactly what they are doing.

EM7 provides a multi-tenant environment that allows service providers to manage systems across many different customers while at the same time providing the customer access to see the same information but only what’s relevant to them.

EM7 was built by service providers and even includes a few features just for them. Two of my favorites are bandwidth billing and the emergency notification system. Take bandwidth billing, for instance. EM7 provides a way to collect bandwidth utilization, store subscription information, and calculate a bill from any one of about 10 different methodologies. And at the end of the billing period, EM7 sends the completed report out to whomever you chose via email.

Another unique service provider feature is the emergency notification system. EM7 allows the provider to track what customers used their unique infrastructure components. If they have to perform maintenance on the infrastructure component or have a problem they can send an email to all of the impacted customers in a matter of minutes.

ScienceLogic: What trends do you see for service providers? What about big trends such as virtualization and cloud computing – how will they impact service providers?

John Proctor: Virtualization is really hot for service providers right now and for the same reasons as in the enterprise. Service providers run data centers and data centers must be powered and cooled. So, anytime they can use a virtual server instead of adding physical equipment it is a good thing. But then you add the complexity that multiple customers reside on the same host and you must track things like bandwidth utilizations by guest OS, and it all gets a little harder. Lucky for us this is not a problem for EM7.

I still think it’s early days for cloud computing. Depending on who you talk to, much of what service providers (especially the big ones) have already been doing with SAAS offerings and hosted applications could be described as cloud computing already. In which case, service providers are ahead of the game. But whatever the “final” definition, cloud computing actually shares many similarities with virtualization – in that service providers (or enterprises) will need to be able to manage far more “devices” in real-time with “zero downtime” expectations by customers. What this really means is that you’re going to see much more automation in provisioning and IT monitoring tools to handle the scale and speed with which things can change in the data center given vm migration and the talked-about switching between “clouds” that can be used for high availability.