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Subject: Re: [Bluez PATCH v6] bluetooth: secure bluetooth stack from bluedump
 attack
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20200217120454.Bluez.v6.1.Ia71869d2f3e19a76a6a352c61088a085a1d41ba6@changeid>
Date:   Tue, 18 Feb 2020 09:18:12 +0100
Cc:     Bluez mailing list <linux-bluetooth@vger.kernel.org>,
        ChromeOS Bluetooth Upstreaming 
        <chromeos-bluetooth-upstreaming@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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Message-Id: <0B84BD16-9C82-4910-8646-B24BCB152AC2@holtmann.org>
References: <20200217120454.Bluez.v6.1.Ia71869d2f3e19a76a6a352c61088a085a1d41ba6@changeid>
To:     Howard Chung <howardchung@google.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@google.com>
> ---
> 
> 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.

Regards

Marcel