usb port: "charging only when locked, except first unlock" confusing

missing-root

What does this mean? Is the port completely off BFU? Or on?? Why would that be useful?

Probably9857

missing-root

For people who want to use an external keyboard to enter a long/complex password.

It means charging and data are both enabled in BFU.

In AFU, only charging when locked (like the default)

missing-root

Probably9857 interesting but strange as that would be the most relevant usb attack moment.

With auto-reboot, before attacks over USB will likely happen in BFU mode.

But yes the long password might be a reason.

I would personally prefer ALSO having an option to set the usb port to charging-only or off in BFU

Probably9857

missing-root I would personally prefer ALSO having an option to set the usb port to charging-only or off in BFU

Charging only when locked does exactly that.

KleinesSinchen

missing-root interesting but strange as that would be the most relevant usb attack moment.

My interpretation for this setting:
An exploit BFU has less impact than AFU.

If an attacker can use some exploit via USB after first unlock (resulting for example in lock screen bypass) this is essentially a “game over” for you.
Bypassing lockscreen BFU doesn’t automatically give the attacker access to the data as the encryption key is not available.

Of course the setting charging only when locked removes more attack surface. I went as far as setting it to charging only.

missing-root

Probably9857 true

Protonuser

Also some behaviour I noticed (Unsure if this is helpful security wise)

For anyone using Wasted, the USB wipe option
Set to Charging only Except Before First Unlock

If you sign into a secondary profile, then the wipe will still trigger. It seems the USB port is still detecting a Data connection on the owner profile. Does this mean that the phone considers the Owner profile as BFU when its still active?

Not sure if this is a security issue or just some quirk. But found it interesting that the phone allows a data connection AFU when logged in to a second profile

missing-root

Protonuser isn't your user profile in BFU then?

de0u

Protonuser For anyone using Wasted, the USB wipe option
Set to Charging only Except Before First Unlock

If you sign into a secondary profile, then the wipe will still trigger. It seems the USB port is still detecting a Data connection on the owner profile.

I don't know how Wasted works -- in particular, what it tries to use as triggers. And the report doesn't say what it was that was plugged in that triggered the wipe. Is it possible that Wasted triggered because it saw USB power, not data?

Protonuser

missing-root

I thought that switching out of owner profile, it is always AFU? I could be wrong though.
Just trying to wrap my head around how the charging only except before BFU works with multiple profiles.
Otherwise, would that not mean Data connection is always enabled when using a secondary profile, since it seems the owner profile is picking up a data connection and is considered "BFU"

Protonuser

de0u
Not sure either. It should only wipe when it detects a data connection.
When I set to charging only, it wouldnt wipe. Only when its set to Data when device is BFU did it trigger while testing.

Just wanted to raise it in case it may be helpful to the team
ie Data connections are attempted or allowed somehow when the setting is to only allow it to make a data connection BFU but you are in second profile, owner profile somehow still allows data connection to be detected. Something like that.

No real issue for me, just in case its something that can be exploited in the future