Am I misreading this, or is this the Signal version of the bug bounty classic "user impersonation vulnerability: if I steal this session token, I can impersonate the user who it belongs to"?
Valid Signal privacy issues shrugged off while patches quietly rolled out
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Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#12Related question… How can an app developer guarantee end to end encryption when the main entry point is almost always a virtual keyboard? Seems like the weakest part of the chain.
Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#13(via mobile quickly, same as my tweet replies on this one)
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hi there! signal did not start silently rolling out patches because there is nothing here to patch. friday’s releases were part of our regular cadence of shipping features and improvements to the apps.
by design, SNs don't change when doing a signal device transfer or when making a linked device change, because the key material doesn't change. we explained this several times and even added to our support article/FAQ. no behavior here has changed.
Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#14Related question… How can an app developer guarantee end to end encryption when the main entry point is almost always a virtual keyboard? Seems like the weakest part of the chain.
How can they guarantee end-to-end encryption when someone could be looking over your shoulder as you type your message?
Same answer. They don’t control the input, they just keep it safe once it’s in transit.
Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#15Am I misreading this, or is this the Signal version of the bug bounty classic "user impersonation vulnerability: if I steal this session token, I can impersonate the user who it belongs to"?
No, you're absolutely right. The author complains that with physical possession of the device that it's possible to transfer Signal's private key material to a new device, leaving the old safety number intact.
The author apparently expects the safety number to change in order to alert the person on the other end that there "might be a hostage situation," evidently not realizing that the attacker could just, well, use the unlocked phone right in front of them.
Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#16I fail to understand why you would want your security numbers to refresh if there's no known risk of your private key having been leaked or stolen. Every time your keys change and you don't manually verify the new ones you risk a mitm attack. Signal just opts to trade off that risk in favor of convenience and more people using end to end encryption for every day communication. I guess OP is saying the fact that they were transferred to a new phone means they might have been stolen? I disagree.
Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#17It would be nice if there was a notification saying the person transferred to a new phone but kept the safety number. This way you can choose your level of paranoia. And there could be a setting to suppress this message (on the receiver).
But in general, if the migration is done securely then migrating the key material seems fine too. By cutting down on benign cases where something changes, this makes the safety number change warning something that warrants more attention.
Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#18Am I misreading this, or is this the Signal version of the bug bounty classic "user impersonation vulnerability: if I steal this session token, I can impersonate the user who it belongs to"?
No, you're absolutely right. The author complains that with physical possession of the device that it's possible to transfer Signal's private key material to a new device, leaving the old safety number intact. The author apparently expects the safety number to change in order to alert the person on the other end that there "might be a hostage situation," evidently not realizing that the attacker could just, well, use…
Well, if I assume that I just got temporary access to someone’s unlocked device, then it would probably be a lot more convenient for me to quickly transfer the account to one of my own devices and then access it from there instead of accessing it from my targets device which I might lose access to any moment.
So from that point of view it would be legitimate to argue that I might want to get notified if one of my contacts transfers his account. I can then double check : “Did you just transfer your signal account to a new device or was that an attacker?”
That might only be interesting for high-risk users though and could impair the UX. Why not make it optional?
Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#19I was expecting to hear about someone who got a new phone, set up Signal using the phone number, and then communicated with contacts without any more authentication. This doesn't appear to be anything of the kind. Signal has implemented a migration system so that people can move to a new phone without changing the safety number. Then a bunch of references to the promises Signal makes about re-verifying if the safety…
I imagine there is a human factors tradeoff here. If signal notified on each migration, users with even medium sized contact lists would likely be getting constant notifications - making the alert useless. See medical device or aviaton alerts experiences.
The problem is that there's no one size fits all solution. Security is all about making tradeoffs based on your threat models.
I think this is probably a sensible default for many people engaging in casual conversations.
However, this notification should probably be configurable. That way you can be notified when communicating with high risk individuals.
Re: Valid Signal privacy issues shrugged off while patches quietly rolled out
#20Related question… How can an app developer guarantee end to end encryption when the main entry point is almost always a virtual keyboard? Seems like the weakest part of the chain.
How can they guarantee E2EE when the message is converted to analog light waves? What about in your brain?
The end of end-to-end is the two messaging devices. That is all and in almost every case, it’s enough.