Tag: security

“Web Security Basics” on Martin Fowler’s Site

Security should be at the heart of our profession, but I’m not sure it ever has been. Job interview preparation for developer jobs is largely focused on algorithms, API’s and problem-solving. It’s probably happened somewhere, but I’ve never heard of an interviewer asking a candidate for a typical developer job about how to prevent SQL injection or XSS attacks. I’ve never seen a job posting for an ordinary developer job which mentioned OWASP in the list of desired buzzwords.

That may be changing slowly. The value created by software development has attracted the attention of a lot of thieves who would be happy to steal it. The software craftsperson has a duty to produce software which will discourage and repel those thieves, but good learning materials in the field of security have been scarce. The OWASP site has a great deal of info about security best practices, but it’s not organized in a way which makes it easy to learn.

Martin Fowler’s blog is now hosting an evolving document written by two software security experts which gives a lot of good advice which is also well-organized and well-explained. It’s a bit presumptious for them to call the document “Web Security Basics”, since most web sites do not yet follow all of their recommended practices (such as using only https for all connections), but the article may move a lot of companies to better protect their users’ data and information security. It should be required reading for software craftspeople.


Are you sure you’ve sanitized your inputs?

This boggles the mind. Using an alphabet of just 6 non-alphanumeric characters, anyone can write any javascript code. The problem of how to allow some friendly javascript code while blocking anything unfriendly might be a subject worthy of computer science research.

In the meantime, eBay (and others) really should do something to reduce this vulnerability. I have a quick-and-dirty solution in Java based on detecting significantly long runs of the 6 characters in question. The weakness of the attack in question is of course that you need a lot of characters to do anything evil in the obfuscated javascript, so there should be long runs containing only  the 6 characters. It’s possible to include spaces and line breaks and even comments to break up the runs – I took this into account in my solution.  I chose 10 as the run length threshold for detecting the obfuscation, because I don’t know of something legitimate you can do in javascript using 10 of these characters in a row that you couldn’t do another way using some alphabetic characters, and if I saw code with 10 of those characters in a row, I would suspect it right away.

Here’s some of the code in my solution. First, the implementation of containsSneakyJavascript:

public static boolean containsSneakyJavascriptCode(final String userInput) {
	SneakyJSDetectionContext ctx = new SneakyJSDetectionContext(userInput);
	while (ctx.notDone()) {
	return ctx.detectedSneakyJS();

That’s code at a pretty high level of abstraction, so here’s more detail with the implementation of the processCurrentChar() call that you see in the code above. It ignores whitespace and characters inside comments and otherwise checks whether the current character adds to or ends the current run of suspect characters and whether it starts a comment:

void processCurrentChar() {
	if (insideAComment()) {
	} else if (isNotWhiteSpace()) {
		if (isInSneakyAlphabet(currentChar())) {
		} else {
			if (isStartOfComment()) {
			} else {

The full implementation code is here, and for good measure here are the unit tests for it.

You’re welcome, eBay.

Quick thoughts about Seth Godin’s article “Our Software must get better”

I’m a long-time Seth Godin fan, so I read with interest his recent article about software quality.

With the examples he gives of inadequacy in software – iTunes user experience, the Macintosh’s built-in address book’s slowness and difficulty with importing and exporting data, and general unreliability and lack of Macintosh-compatibility of stamps.com – he’s focused mostly on the user experience aspects of software, which I think misses a key point. I think the biggest problems for software users these days are not slowness, confusion, frustration and extra clicks – though these can be real problems. The big issue for software users today, IMHO, is in the realm of data security, transparency and privacy.

Software in general is getting really good at collecting data profiles of the people who use it. I think this can be done in an ethical, transparent and generally secure way which generates value for the software’s creator in a fair and honest exchange for the user experience that consumers want. Is that what’s happening now? Not enough to satisfy European governments, who are taking action on this issue.

Seth Godin is smart enough and experienced enough to set up a kickstarter for a better Mac address book that is fast and can handle imports. But he would like software users to take ownership of the quality of the software that they use, by explicitly paying for what they use and by insisting on a user experience that meets their needs. On a large scale, that would be a pretty radical change, which would surely have a positive impact.

For the moment, most users either don’t know what “better” is or don’t care enough to pay for it. The trend among the giants of the software industry landscape seems to be that better means “smarter”, which means “knows what you want”, which is a problem in the aforementioned realm of data security, transparency and privacy. If you collect personal information, you must protect it forever and use it in a way which is ethical and transparent. If your smart assistant in the cloud knows that you have an appointment next Tuesday with Doctor So-and-so and the Such-and-such Clinic, who else will know that? The only data which is 100% guaranteed to be private is data which is never collected.

Ironically, the respect for privacy seems to be better in free software (Mozilla, Linux, etc.) than in software which people pay for. Godin alludes to this in his point “C” as to why software is mediocre.

Seth Godin would obviously like us, the software craftspeople of the world, to insist on better user experience, and, ideally, he’s right. It should be part of the software craftsperson’s ethics to improve the user experience. It’s not always clear, though, who should be responsible for defining what constitutes improvement or deciding what time and resources should be allocated for it.

At a minimum, we as developers can strive to create software which is easy enough to change that the user experience can be improved easily once we understand what improvements need to be made. We can also strive to treat the users’ personal data as a precious commodity to be protected, we can sanitize our inputs, and we can use the best encryption techniques available for passwords and other sensitive data.