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this post was submitted on 10 Jul 2023
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lemmy.ml meta
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Anything about the lemmy.ml instance and its moderation.
For discussion about the Lemmy software project, go to !lemmy@lemmy.ml.
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I think they're stealing auth tokens, not sure if 2fa would help. It looks like there may be a vulnerability in the markdown editor and being able to insert JavaScript. The JS being able to access your cookies to share them is the second issue.
https://lemmy.sdf.org/comment/850269
Yup. Changing your password or 2FA wouldn’t help here, because they’re not actually logging into your account. Rather, they’re simply telling the server that they’re already logged in, using your auth token as proof. You know that little “Keep me logged in” checkbox that everyone clicks when they log in? That stores an auth token on your browser, which is tied to your account.
The next time the browser starts a session on the site, it sends that auth token instead of going through the regular login process. And since the site knows that auth token belongs to your account, it logs you in automatically without needing to go through the regular login process.
So basically, they’re stealing a cookie from your browser, with your name on it. Then they’re able to tell the server that they’re you, by presenting that cookie as proof.
Proper procedure should be to deauthorize any auth tokens when you change your password. But even big sites get lazy about this sometimes, so it may not be the default. If this is the case for Lemmy, even changing your password won’t help because it doesn’t automatically deauth that token.
Really curious to see how they kill the existing tokens, and whether admins have tools to easily clear all sessions. On one of the Matrix chats someone suggested that the tokens have a one year expiry date!
The servers should theoretically have a way to murder the tokens, but I'm not sure how Lemmy has implemented authentication so I don't know for sure.
Looks like you're right, admins will just need to update the JWT secret.
That makes sense. Of course, updating the secret will log everyone out, but that's a small price to pay to fix an admin breach.
Tokens are signed with a secret string, which basically tells the server that it is legitimate. They could change that secret, and the server would immediately distrust any tokens signed with the old secret. This would be a pretty nuclear option though, because it would require every single user to log back in.
You’re not the first person to say that the expiration time is a year, which is hilariously long if true. A shorter expiration time is more secure (because it specifically limits attacks like this to a specific timeframe) but it also increases server load by requiring token requests more often. For instance, if the expiry was set at 5 minutes, you’d have requests every 5 minutes but an attacker would only have control of an account for a maximum of five minutes. Maybe it was done to help save on server load, since this is all basically run by a few people as a hobby.