Re: [Bluez PATCH v6] bluetooth: secure bluetooth stack from bluedump attack

From: Marcel Holtmann
Date: Tue Feb 18 2020 - 03:18:19 EST

Hi Howard,

> Attack scenario:
> 1. A Chromebook (let's call this device A) is paired to a legitimate
> Bluetooth classic device (e.g. a speaker) (let's call this device
> B).
> 2. A malicious device (let's call this device C) pretends to be the
> Bluetooth speaker by using the same BT address.
> 3. If device A is not currently connected to device B, device A will
> be ready to accept connection from device B in the background
> (technically, doing Page Scan).
> 4. Therefore, device C can initiate connection to device A
> (because device A is doing Page Scan) and device A will accept the
> connection because device A trusts device C's address which is the
> same as device B's address.
> 5. Device C won't be able to communicate at any high level Bluetooth
> profile with device A because device A enforces that device C is
> encrypted with their common Link Key, which device C doesn't have.
> But device C can initiate pairing with device A with just-works
> model without requiring user interaction (there is only pairing
> notification). After pairing, device A now trusts device C with a
> new different link key, common between device A and C.
> 6. From now on, device A trusts device C, so device C can at anytime
> connect to device A to do any kind of high-level hijacking, e.g.
> speaker hijack or mouse/keyboard hijack.
> Since we don't know whether the repairing is legitimate or not,
> leave the decision to user space if all the conditions below are met.
> - the pairing is initialized by peer
> - the authorization method is just-work
> - host already had the link key to the peer
> Signed-off-by: Howard Chung <howardchung@xxxxxxxxxx>
> ---
> Changes in v6:
> - Fix passkey uninitialized issue

since I already applied v5, can you send a delta-patch. And please add a comment for using 0 as passkey and why that is correct.