[Bluez-devel] Force pairing on single connection?

[Bluez-devel] Force pairing on single connection?

[Nils Faerber]

Hi!
Is it possible to force a pairing process for a single device pair?
The situation is that I have a device that seems to accept non-paired
and paired connections. I would now like to pair with this device and
thus force the pairing, but only for this device - I am quite happy with
not being forced to pair for mostly all other devices ;)
CU
  nils faerber

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Re: [Bluez-devel] Force pairing on single connection?

[Marcel Holtmann]

Hi Nils,

> Is it possible to force a pairing process for a single device pair?
> The situation is that I have a device that seems to accept non-paired
> and paired connections. I would now like to pair with this device and
> thus force the pairing, but only for this device - I am quite happy with
> not being forced to pair for mostly all other devices ;)

you must issue a HCI_Authenticate command on the HCI socket. There is no
other method at the moment. I was thinking about adding an ioctl to the
L2CAP socket so this can also be triggered by normal users.

Other proposals are welcome.

Regards

Marcel




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Re: [Bluez-devel] Force pairing on single connection?

[Marcel Holtmann]

Hi Nils,

> > > Is it possible to force a pairing process for a single device pair?
> > > The situation is that I have a device that seems to accept non-paired
> > > and paired connections. I would now like to pair with this device and
> > > thus force the pairing, but only for this device - I am quite happy with
> > > not being forced to pair for mostly all other devices ;)
> > you must issue a HCI_Authenticate command on the HCI socket. There is no
> > other method at the moment. I was thinking about adding an ioctl to the
> > L2CAP socket so this can also be triggered by normal users.
> > Other proposals are welcome.
> 
> Hmm... maybe as a first quickshot simply add a function to hcitool which
> does exctly this command issue. Hcitool can already issue arbitrary HCI
> commands and adding a function for forcing authentication would simply
> be a convenience thing...
> Something like
> 	hcitool auth <BT-MAC>
> maybe...

sure. Send me a patch for it (including man page update).

> The rest should happen automatically? I.e. PIN input and such would go
> the normal way of PINs I suppose, so either by script or GUI input.

Yes.

Regards

Marcel




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Re: [Bluez-devel] Force pairing on single connection?

[Fred Schättgen]

On Tuesday 10 February 2004 11:05, Marcel Holtmann wrote:
> Hi Nils,
>
> > Is it possible to force a pairing process for a single device pair?
> > The situation is that I have a device that seems to accept non-paired
> > and paired connections. I would now like to pair with this device and
> > thus force the pairing, but only for this device - I am quite happy with
> > not being forced to pair for mostly all other devices ;)
>
> you must issue a HCI_Authenticate command on the HCI socket. There is no
> other method at the moment. I was thinking about adding an ioctl to the
> L2CAP socket so this can also be triggered by normal users.

This would in fact be very useful. With it we could make our obex push server 
accept connections from everyone, while other services require authentication 
(the services don't have root privileges). Did you add that ioctl already? 
If not, do you think it's save for us to use a little suid program to let 
normal users issue HCI_AUTHENTICATION_REQUESTED in the meantime?

> Other proposals are welcome.

I don't understand why there should be an l2cap ioctl for it. Isn't it enough 
to let everybody use HCI_AUTHENTICATION_REQUESTED, just like it's the case 
for HCI_INQUIRY and add a helper function to hci_lib.h?

Btw. there is a related issue where I don't have an answer for..
how can we deal with pairing in a multi-user environment? At the moment, 
whoever is logged in can enter a pin when a device requests authentication. 
What if I don't trust the other users? Someone else may have paired with a 
device with a faked address, so the fact that a connection could be 
authenticated doesn't mean that *I* verified the identity of the other party. 
I don't have an idea how this could be handled with the standard HCI 
functions though - can I pair two devices again while the current link is 
already authenticated? If this is possible, then BlueZ could remember the old 
link key and provide an interface for applications to find out if the 
currently used link key is the "successor" of a key where we checked the 
identity of the other device ourself. 
The other solution - letting only an administrator pair devices - doesn't seem 
to be a nice solution too.  Any ideas?

greetings
Fred

Re: [Bluez-devel] Force pairing on single connection?

[Marcel Holtmann]

Hi Fred,

> > you must issue a HCI_Authenticate command on the HCI socket. There is no
> > other method at the moment. I was thinking about adding an ioctl to the
> > L2CAP socket so this can also be triggered by normal users.
> 
> This would in fact be very useful. With it we could make our obex push server 
> accept connections from everyone, while other services require authentication 
> (the services don't have root privileges). Did you add that ioctl already? 
> If not, do you think it's save for us to use a little suid program to let 
> normal users issue HCI_AUTHENTICATION_REQUESTED in the meantime?
> 
> > Other proposals are welcome.
> 
> I don't understand why there should be an l2cap ioctl for it. Isn't it enough 
> to let everybody use HCI_AUTHENTICATION_REQUESTED, just like it's the case 
> for HCI_INQUIRY and add a helper function to hci_lib.h?

the point for an ioctl is to make it easier for the programmer, because
for the HCI command you need to find out the connection handle and the
open L2CAP/RFCOMM socket already knows its handle.

> Btw. there is a related issue where I don't have an answer for..
> how can we deal with pairing in a multi-user environment? At the moment, 
> whoever is logged in can enter a pin when a device requests authentication. 
> What if I don't trust the other users? Someone else may have paired with a 
> device with a faked address, so the fact that a connection could be 
> authenticated doesn't mean that *I* verified the identity of the other party. 
> I don't have an idea how this could be handled with the standard HCI 
> functions though - can I pair two devices again while the current link is 
> already authenticated? If this is possible, then BlueZ could remember the old 
> link key and provide an interface for applications to find out if the 
> currently used link key is the "successor" of a key where we checked the 
> identity of the other device ourself. 
> The other solution - letting only an administrator pair devices - doesn't seem 
> to be a nice solution too.  Any ideas?

In the early days I had a long discussion about multi-user environments
with Max. I hope everything of that is in the archive, but actually none
of us had the right solution for it. The Bluetooth specification don't
really talks about it, as it also don't talks about multiple dongles on
the same host and the interface to the HCI, L2CAP and RFCOMM layers for
userspace applications.

Regards

Marcel




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Re: [Bluez-devel] Force pairing on single connection?

[Fred Schättgen]

On Friday 19 March 2004 01:13, Marcel Holtmann wrote:
> Hi Fred,
..
> > I don't understand why there should be an l2cap ioctl for it. Isn't it
> > enough to let everybody use HCI_AUTHENTICATION_REQUESTED, just like it's
> > the case for HCI_INQUIRY and add a helper function to hci_lib.h?
>
> the point for an ioctl is to make it easier for the programmer, because
> for the HCI command you need to find out the connection handle and the
> open L2CAP/RFCOMM socket already knows its handle.

I don't really care how to do it, if only it can be done as an ordinary 
user :) Otherwise we can't use authentication at all if only one service 
should work without it and if we don't want to bother the users with 
unnecessary PIN-popups.
Or is it a potential security hazard to allow everybody to request 
authentication? I don't think so, since the other device could ask for 
authentication itself.

...
> In the early days I had a long discussion about multi-user environments
> with Max. I hope everything of that is in the archive, but actually none
> of us had the right solution for it. The Bluetooth specification don't
> really talks about it, as it also don't talks about multiple dongles on
> the same host and the interface to the HCI, L2CAP and RFCOMM layers for
> userspace applications.

You're right, it's in the SF archive, sorry. I only searched in the gmane 
archive, but failed to realize that it doesn't contain everything from the 
beginning.
It looks like there is really no good way to associate link keys with users. 
But then it might be a good idea let only a selected group of users answer pin 
requests, because often link level authentication is the only option. Or you 
simply have to trust any other users of your system...

greetings
Fred