In “Towards a standard for bearer token URLs”, I described a URL scheme that can be safely used to incorporate a bearer token (such as an OAuth access token) into a URL. That blog post concentrated on the technical details of how that would work and the security properties of the scheme. But as Tim Dierks commented on Twitter, it’s not necessarily obvious to people how you’d actually use this in practice. Who creates these URLs? How are they used and shared? In this follow-up post I’ll attempt to answer that question with a few examples of how bearer URLs could be used in practice.Continue reading “How do you use a bearer URL?”
There’s a persistent belief among web security people that cross-site scripting (XSS) is a “game over” event for defence: there is no effective way to recover if an attacker can inject code into your site. Brian Campbell refers to this as “XSS Nihilism”, which is a great description. But is this bleak assessment actually true? For the most part yes, but in this post I want to talk about a faint glimmer on the horizon that might just be a ray of sunshine after all.Continue reading “XSS doesn’t have to be game over”
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.