You receive a call on your phone. The polite call centre worker on the line asks for you by name, and gives the name of your bank. They say they're calling from your bank's fraud department. "Yeah, right!" You think. Obvious scam, isn't it? You tell the caller to do unmentionable things to a goat. They sigh. "I can assure you I'm calling from Chase bank. I understand you're sceptical. I'll send a push notification through the app so you can see this is a genuine call." Your phone buzzes.…
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It is tempting to think that users are to blame for their own misfortune. If only they'd had a stronger password! If only they didn't re-use credentials! If only they had perfect OpSec! If only...! Yes, users should probably take better care of their digital credentials and bury them in a digital vault. But there are some things which are simply impossible for a user to protect against. Take, for example, a SIM-swap attack. You probably have your phone-number tied to all sorts of important…
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It's never great to find out you're wrong, but that's how learning and personal growth happens. HTTP Message Signatures are hard. There are lots of complex parts and getting any aspect wrong means certain death. In a previous post, I wrote A simple(ish) guide to verifying HTTP Message Signatures in PHP. It turns out that it was too simple. And far too trusting. An HTTP Message Signature is a header which is separate to the message it signs. You might receive a JSON message like this: { …
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It's always fun keeping your network inspector tab open. While looking around the O2 UK website, I found this page all about eSIMs. For some reason, it wants to know the user's phone number. I put in a random number, and it refused to let me in. Putting in a genuine O2 number let me through. So what is it doing to validate numbers? It is making an API call to this URl: https://www.o2.co.uk/o/customer/mods/lookup/447700900123 After a bit of testing, this is how I think it works. If you …
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I'm trying to get my head round HTTP Signatures as they're used extensively in the Fediverse. Conceptually, they're relatively straightforward. You send me a normal HTTP request. For example, you want to POST something to https://example.com/data You send me these headers: POST /data Host: example.com Date: Sat, 24 Feb 2024 14:43:48 GMT Accept-Encoding: gzip Digest: SHA-256=aaC57TDzM0Wq+50We2TkCsdMDvdqON92edg7KI+Hk8M= Content-Type: application/activity+json Signature:…
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You type in to your browser's address bar example.com and it automatically redirects you to the https:// version. How does your browser know that it needed to request the more secure version of a website? The answer is... A big list. The HTTP Strict Transport Security (HSTS) list is a list of domain names which have told Google that they always want their website served over https. If the user tries to manually request the insecure version, the browser won't let them. This means that a…
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I've responsibly disclosed a small security issue with Mastodon (GHSA-8982-p7pm-7mqw). It allows a sufficiently determined attacker to use any Mastodon instance to redirect unwary users to a malicious site. What do you think happens if you visit: https://mastodon.social/@PasswordReset/111285045683598517/admin? If you aren't logged in to that instance, it will redirect you to a 3rd party site. Try opening it in a private browser window. Here's another, less convincing, demo: …
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Quite often websites will encourage you to copy and paste commands into your terminal. There are a variety of reasons why this is bad - not least because someone could hide malicious code. That's usually done with a bit of CSS to make the evil command invisible, or using Javascript to inject something unwanted into your keyboard. Here's method that I hadn't seen before. Copy this code and paste it into your terminal to see your external IP address: Notice anything weird about it? Depending …
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The other day, my HP M140w printer stopped working. The day before, it printed fine. This time, nothing. I rebooted, reset, updated, and performed all the modern rituals associated with uncooperative hardware. I logged into to the printer's webserver and clicked around the admin panel. On one page, I found an error message. So, like any self-respecting geek, I ignored what it said and Googled the text. The first result on Google looked hopeful. I clicked on it and, somehow, ended up back on…
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Should my bank be able to block me from using their Android app, just because my phone is rooted? I'm reluctantly coming to the conclusion that... yeah, it's fair that they get to decide their own risk tolerance. Sage of the Internet, and general Sooth Sayer, Cory Doctorow once gave an impassioned speech on "The Coming War on General Computation". I'll let you read the whole thing but, I think, the salient point is that some people want to restrict the maths we're allowed to do on our…
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I used to work in a call centre for a Very Big Company. Every week, without exception, we'd get a bunch of new starters to train. And every week, without exception, a newbie would be fired after looking up a famous person's data. This was in the days before GDPR. There was a lot less general awareness of data protection issues. It didn't matter how often will drilled it into trainees' heads - someone would breach privacy within 5 minutes of getting on the system. It seemed to be an almost…
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Suppose you are sent a link to a website - e.g. https://example.com/page/1234 But, before you can access it, you need to log in. So the website redirects you to: https://example.com/login?on_success=/page/1234 If you get the password right, you go to the original page you requested. Nice! But what happens if someone manipulates that query string? Suppose an adversary sends you a link like this: https://example.com/login?on_success=https://evil.com A sensible redirection system should say…
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