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Secure software contracting hypothetical case study

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Let's Sue the Idiots -- Security, Software, Contracts, and Lawyers

  • By Jeff Williams (Aspect Security, Inc.)
  • Posted January 13, 2004


What would you do if you outsourced your web application development to a software shop, only to find out years later that the code they produced is full of security holes? What would you do if you were a developer who wrote the code? Sound familiar? In many organizations, the knee-jerk reaction is to sue the developers on a breach of contract or negligence theory, but that's about the biggest mistake you can make. This column discusses how these disputes happen, how the contracts work, some of the arguments on both sides, and suggests a middle ground that will hopefully help guide you through a delicate situation.

What do you do when you realize software you wrote might have vulnerabilities?

Just Another Outsourced Web Application

Imagine the plight of the National Widgets. Two years ago, National contracted with the talented Front End Associates to build a web site for their users. The contract detailed the work to be performed, the schedule, and many functional requirements - but was completely silent on security. Front End built the site and National deployed it about 18 months ago without incident. The site has been working well and National has provided strong references for Front End.

Recently, some National employees raised the possibility of security problems, so National went to Front End and asked them whether the application is secure. The Front End sales team started dancing and said that they were confident that they met their contractual obligation and would be happy to submit a proposal to respond to these 'new' requirements. National was unsure about the original contract and went to their lawyers to see if the original contract required security.

Send In the Lawyers!

The lawyers got very excited about the issue, and started making statements about the standard of care, rights, duties, and res ipsa loquitur. National never did get a clear answer about whether the contract did or didn't require security. So they just went back to Front End and asked them to fix the problems for free. And that's where the situation started to unhinge.

Front End said that they didn't believe that there were any security problems in their code. Before delivery, they had hired a security testing company to do a security audit of their application. The company they hired claimed to specialize in penetration testing to test and prepare a report. Unfortunately, all the company did was to run a few scanning tools like nmap and nessus. They cleaned up the tool output and delivered the report. National laughed when Front End brought up the report, and asked them to produce the application security test results for the application they developed. Confronted with this, Front End rapidly backed down and again claimed that there were no security problems with their code, and even if there were, they weren't required to build secure code.

National responded that the requirement to build secure code is obvious, and that any vendor who knowingly built insecure code is clearly negligent. Then, obviously grasping, they started throwing around terms like implied warrantee, strict liability, and class action. They even called the OWASP Top Ten the de facto standard for web application security and mentioned that even the U.S. Federal Trade Commission is going after companies that don't meet the standard.

Everybody Hires Experts

Quietly, Front End began to worry that their code did have security problems. So they hired their own experts. They found a firm that specialized in web application security to review their code and do some application penetration testing. These experts found quite a lot of problems in the first few days, and called Front End to let them know how it was going. A senior manager at Front End called the experts back after a few days to let them know that they would not require a written report for their findings. Rather they would prefer to receive all the findings orally during teleconferences.

In the meantime, National decided that the first order of business was to prove that there were indeed serious security problems with their code. So they hired their own web application security experts and arranged for an application security review. These experts started with the standard web application vulnerability scanning tools, but only found a few problems. The experts wanted to do a code review, and asked National to send a copy of the source code for the application. But National never asked for, and did not have a copy of the source code for their application. When they asked Front End for a copy, they were delayed and ultimately refused, mentioning trade secret and copyright issues. Fortunately for National, the code was written in Java and was not obfuscated. So the experts thumbed their noses at the Digital Millennium Copyright Act (DMCA), decompiled the code with Jad, and performed their code review anyway. They also did some penetration testing along with the code review to validate their findings.

Unfortunately (but not surprisingly), the review found serious problems in six of the Top Ten categories. Several of the problems were design-level problems and would require quite a few man-months of effort to fix. So, National went back to Front End, showed them the findings, and asked them again to fix the problems for free. Front End, now quite worried, responded that they would take the matter up with their lawyers and left the meeting. Not surprisingly, the lawyers never did respond to National.

Bad to Worse

So, National felt obligated to file suit against Front End, claiming that Front End had not performed the work required under the contract and that they should fix the problems and pay National's legal fees. Front End responded with a motion to dismiss, based on the fact that the code was developed over two years prior, that they had been paid, and that the code had therefore been fully accepted by National. They also argued in the alternative that they could not be held liable for not meeting requirements that did not exist at the time of contracting.

Both sides have now invested many tens of thousands of dollars in legal fees, lost productivity, and reputation damage. In addition to actual litigation costs, both parties spent a significant amount of time answering interrogatories, producing documents, getting ready for depositions, and in trial. Many of the original developers of the National application left Front End as the environment had changed dramatically, and they did not want to be blamed for the debacle.

A Better Way?

This miserable story is a good example of how NOT to handle this issue. There are clearly many companies who are in this situation, and the legal system is not a good way out. There is some right and wrong on both sides, so let's look at a better way to clean up this mess, and then we'll conclude with some ideas about preventing these problems from happening in the future.

First, everyone on both sides needs to understand that building a secure web application takes more effort than just building one that looks pretty. If you're the customer, you should stop feeling ripped off. If you and the builder had discussed the issue, the price would have almost certainly been higher. You should also take into account that the vast majority of developers do not have a strong understanding of security, so it is not reasonable to expect vulnerability-free code without paying for it. At the end of the day, you probably got what you paid for. If you suspect security problems in your applications, don't ignore them.

But, if you're the developer, don't pretend to be innocent here. If the customer had asked whether the code would have vulnerabilities you would have almost certainly said no. And you wouldn't have added very much, if anything, to your bid. You know that you really should have taken the time to do the security requirements and get it built and tested properly. Most of these vulnerabilities have been well understood for many years, and they are not difficult to avoid. If you uncover or even suspect vulnerabilities in code your company wrote, the responsible thing to do is to let your customers know. In fact, you may have a legal obligation to warn your customer - just as if you had sold them a car with faulty brakes. Most buyers will respect the fact that you've come forward with this information and work with you to resolve the issues.

Nobody wins if you end up in court.
Do your homework and work it out.

The only equitable thing for parties in this situation is to figure out a way to share the costs involved with fixing the problems. If you find yourself in this situation, the first thing to do is to meet with the other party to discuss your concerns and suggest a plan for resolving any possible issues. The fact is that there are vulnerabilities in the software that neither party thought of when you were agreeing to do the work. Agree on an independent third party to perform an accurate assessment of what the application is going to take to fix. Sharing the costs of this review is reasonable, since both parties will benefit from the findings. The meeting should also include a careful review of the contract language to see if there are any terms that assign responsibility in this situation.

To ensure completeness, the third party review should include code analysis and some penetration testing. It's reasonable for the review to focus on the OWASP Top Ten, in order to keep the findings grounded in a reasonable minimum standard for web applications. The report should include detailed descriptions of any findings, focused on exactly what is wrong with the code. The reviewers will need access to the code to make these judgments and will need strong code review skills. In addition, the third party should estimate the risk associated with the flaw in the specific context of the customer's enterprise.

Once you have a justifiable list of problems from an independent third party, both parties should meet again to create a plan for getting them fixed. The purpose of the meeting should be to identify which problems the developer will fix, how difficult the fixes will be, and who is going to pay for the fixes. Remember that if you can't find some common ground here, both parties will end up in court and only the lawyers will win.

What Would Happen in Court?

This is a difficult question, since there are so many variables at work. But my best guess is that a court would end up splitting the difference anyway. Most courts are not going to understand the technical issues with these vulnerabilities, so they will look to external standards and industry practice. This will end up as a battle of expert witnesses, some saying that these vulnerabilities have been well understood for 25 years, the others arguing that most developers do not understand security and that there are no standards. Ultimately, the court is not going to be able to decide who is responsible for what. They might decide for the developer, thinking that it is unfair to hold developers to requirements that are not explicitly stated and are not industry practice. On the other hand, they could easily hold for the customer, on the theory that the developer either knew or should have known about these vulnerabilities, and therefore should have taken measures to prevent them in their software.

Either way, the cost of fixing these problems will
be dwarfed by the cost of litigating the issue.
So get with your partner and work it out. 

What Should Happen When the Contract Is Silent

When contracts are silent on an issue, the law fills in the missing terms with what it thinks the parties would have intended. These "default" terms come from statutes, the UCC, trade practices, and many other sources. But application security is new enough and moving fast enough that it's anybody's guess what sources a court might lean on to decide a case. So just for a moment, let's put on a lawmaker hat and try to decide what ought to happen.

Would the world be a better place if the default contractual term were zero security? No, this can't be the right answer. This would mean that unless you specifically call it out, developers have no responsibility to make their code secure. Developers would have no responsibility to avoid well understood vulnerabilities. This puts all the burden on the buyer, who is not in a very good position to know what vulnerabilities might occur. So this approach would be extremely economically inefficient.

But imagine the opposite extreme, where the developer is required to produce a perfectly secure application if the contract is silent. This can't be the right answer either. In general, putting liability on the party in the best position to avoid the problem will produce the most efficient results. However, since creating perfectly secure code is virtually impossible, this would create unlimited liability for software builders. Obviously, this would have a dramatic effect on the ability of software makers to practice their craft. Therefore, courts should read in some basic security requirements into contracts that are silent on the issue. The list should include requirements that both parties would have agreed to if the topic had been discussed. Well understood security vulnerabilities like those in the OWASP Top Ten are a reasonable starting point. But it would be far better if the buyer and builder work out the real security requirements for the project and capture them in the contract, rather than relying on what a court might dream up if you ignore the issue.

Next Time?

Hopefully, most readers are not currently in this situation, and would just like to prevent it from happening in the future. The right way is to set up specific contractual terms about how good the security needs to be for the project.

Dave Thomas has written that quality should be a part of the requirements that you negotiate with the customer up front. NASA spends something like $1,000 per line of code. For you non-math majors, that's a million dollars for even a trivial 1000 line program. And although they have a fantastic record on software quality, they still occasionally lose a probe or crash a rocket because of software problems.

Security, like quality, is something that software builders and buyers should discuss, as there are legitimate business reasons for web applications with differing levels of security. Buyers, of course, are initially going to expect software without any vulnerabilities. This, of course, is not realistic. Builders, at least if history is any guide, are going to want to build software that meets the functional requirements and not worry about security at all. Leaving security out of the negotiation entirely is also not appropriate, as the default legal rules are quite unclear.

The software builder and buyer need to have a frank discussion that addresses questions like:

  • What types of incidents would be considered serious (e.g. disclosure, corruption, denial of service)?
  • Do all the developers have to be trained in security?
  • Do you want a documented security policy and/or security requirements for the application?
  • Do you want detailed documentation of the security design and mechanisms?
  • Do you want a security review of the design?
  • Do you want penetration testing done before deployment?
  • Do you want the code reviewed by security experts?
  • Who takes the risk on fixing security problems discovered down the road?

Buyers should expect that there will be some additional charges for increased security, and that they can get a cheaper price if they decline these security services. As a contractual starting point, you may want to consider the draconian Code Integrity Warranty that puts all the burden on the developers for any bug of any kind that affects security. At least the terms are very clear, but the potential liability for developers is staggering.


So, if you're outsourcing software development, talk with your developers. Make sure they understand your security needs. Make sure it gets in the contract. You may have to answer some hard questions about just how much security you're willing to pay for. If you're a software developer, be clear about what security you are providing, then do it. Make sure you understand whose responsibility it will be if a security vulnerability is uncovered after the software is in production.