URLs are a cornerstone of the web, and are the basic means by which content and resources are shared and disseminated. People copy and paste URLs into Slack or WhatsApp to share interesting links. Google crawls the web, discovering and indexing such links. But what happens when the page you want to link is not public and requires credentials in order to view or interact with it? Suddenly a URL is no longer sufficient, unless the recipient happens to already have credentials. Sometimes they do, and everything is fine, but often they do not. If we really do want to give them access, the problem becomes how to securely pass along some credentials with the URL so that they can access the page we have linked.
A commonly desired approach to this problem is to encode the credentials into the URL itself. While convenient, this solution is fraught with dangers and frequently results in credentials being exposed in insecure contexts. In this article, we’ll look at various ways to accomplish this, the ways that things can go wrong, and conclude with a set of guidelines for cases where this can be made secure, and actually improve security overall.
Continue reading “Can you ever (safely) include credentials in a URL?”
In the wake of some more recent attacks against popular JSON Web Token (JWT)/JSON Object Signing and Encryption (JOSE) libraries, there has been some renewed criticism of the JWT/JOSE standards themselves (see also discussion on lobste.rs with an excellent comment from Thomas Ptacek summarising some of the problems with the standard). Given these criticisms, should you use JOSE at all? Are articles like my recent “best practices” one just encouraging adoption of bad standards that should be left to die a death?
Certainly, there are lots of potential gotchas in the specs, and it is easy for somebody without experience to shoot themselves in the foot using these standards. I agree with pretty much all of the criticisms levelled against the standards. They are too complicated with too many potentially insecure options. It is far too easy to select insecure combinations or misconfigure them. Indeed, much of the advice in my earlier article can be boiled down to limiting which options you use, understanding what security properties those options do and do not provide, and completely ignoring some of the more troublesome aspects of the spec. If you followed my advice of using “headless” JWTs and direct authenticated encryption with a symmetric key, you’d end up not far off from the advice of just encrypting a JSON object with libsodium or using Fernet.
So in that sense, I am already advocating for not really using the specs as-is, at least not without significant work to understand them and how they fit with your requirements. But there are some cases where using JWTs still makes sense:
- If you need to implement a standard that mandates their use, such as OpenID Connect. In this case you do not have much of a choice.
- If you need to interoperate with third-party software that is already using JWTs. Again, in this case you also do not have a choice.
- You have complex requirements mandating particular algorithms/parameters (e.g. NIST/FIPS-approved algorithms) and don’t want to hand-roll a message format or are required to use something with a “standard”. In this case, JWT/JOSE is not a terrible choice, so long as you know what you are doing (and I hope you do if you are in this position).
If you do have a choice, then you should think hard about whether you need the complexity of JWTs or can use a simpler approach that takes care of most of the choices for you or store state on the server and use opaque cookies. In addition to the options mentioned in the referenced posts, I would also like to mention Macaroons, which can be a good alternative for some authorization token use-cases and the existing libraries tend to build on solid foundations (libsodium/NaCl).
So, should you use JWT/JOSE at all? In many cases the answer is no, and you should use a less error-prone alternative. If you do need to use them, then make sure you know what you are doing.
Now that the dust has settled on the launch of Java 8, we can begin to see the benefits that all these new features will bring to those of us willing to throw off the yoke of corporate oppression and start committing lambda expressions to a “Java 5” code base. The possibilities that lambdas bring, along with default methods, and the startling addition of static methods in interfaces are real game changers. For instance, it is now possible to write an entire Java application in a single interface! Those of us who have long railed against the tyranny of a single-class-per-file can now rejoice at being able to place all of our logic in a single file, and it doesn’t even need to be a class. As you will see from this post, the future is here and it is beautiful.
Continue reading “Single Interface Java 8 Applications”
I’m becoming increasingly confused about what direction the Web is heading in. More precisely, I’m slightly concerned that the direction the Web is heading in is completely different to the direction in which various researchers believe it is heading in.
Continue reading “Where is the Web going?”