Nasty Bluetooth Bug -- Possible Security Issue

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Level 4

1,412 points

Nasty Bluetooth Bug -- Possible Security Issue

I believe I have found a nasty bug in Mac OS X Lion 10.7.1 that relates to Bluetooth. I have installed Lion on all of our home Macs (specs below), all but one were upgrades from Snow Leopard, yet exhibit this same exact issue.

Problem: Mac Bluetooth remains in "Discoverable Mode" despite the checkbox in System Preferences > Bluetooth being unchecked. Doing a simple search for Bluetooth devices on any open Bluetooth device (Mac or PC) will see the Mac despite the checkbox being unchecked and discoverable mode being turned off.

Workaround: Check the Discoverable box in System Preferences > Bluetooth, click Show All. Go back into System Preferences > Bluetooth and uncheck Discoverable, click Show All. this will turn off Bluetooth discoverability mode for sure.

I found this exact issue on all of our home Macs. In fact, our home iMac (early '08) has had a fresh, clean Mac OS X Lion installation via Recovery HD that installed 10.7.1 by default. This means that this bug is inherent in vanilla 10.7.1.

I discovered this when I was attempting to pair my new Jawbone ERA headset with my Macbook Pro. Coincidentally, all Macs in our home were on, and I saw them all pop-up in "Setup Bluetooth Device" window despite all of them having Discoverable mode turned off (I checked). The only method around this was the workaround I mentioned earlier. I fear that most people who are using their Macs with Bluetooth turned on with Discoverability mode turned on despite it being unchecked in the System Preference window.

MacBook Pro, Mac OS X (10.7), 8GB RAM

Posted on Oct 7, 2011 7:25 PM

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Answer 1

JohnBradshaw Author

Level 4

1,412 points

Oct 7, 2011 7:56 PM in response to JohnBradshaw

PS: If you notice this same issue in your setup, be sure to let Apple know via their feedback form.

http://www.apple.com/feedback/macosx.html

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Answer 2

JohnBradshaw Author

Level 4

1,412 points

Oct 7, 2011 10:42 PM in response to JohnBradshaw

Update. I found that the workaround is only temporary, lasting until the Mac is put into sleep mode then woken up again. However, turning Bluetooth OFF then ON again seems to clear it up.

Discoverable mode setting in System Preferences does not seem to matter.

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Answer 3

thomas_r.

Level 7

31,989 points

Oct 8, 2011 3:16 AM in response to JohnBradshaw

I do not see the same behavior here, unless I'm doing something different than you. Testing with my iPhone and iPad, I can only see my Mac with Bluetooth on and set to be discoverable. If either checkbox is off, the Mac does not show up.

Do you perhaps have something else going on that requires Bluetooth to remain discoverable? For example, do you have Bluetooth Sharing turned on in System Preferences -> Sharing? I've never used that, but it's possible that might override your discoverable setting, since it would be rather useless if you couldn't find the device for sharing.

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Answer 4

JohnBradshaw Author

Level 4

1,412 points

Oct 8, 2011 8:48 AM in response to thomas_r.

Hi Thomas,

I was only able to see the other Macs from other Macs (not from my iOS devices). Sharing was indeed disabled on all Macs, as was Discoverable mode.

Placing two Macbooks beside one another, each running 10.7.1 with Discoverable Mode turned off, I was able to replicate the issue simply by putting the Macbook to sleep then waking it up again. I set one Macbook in Setup Bluetooth Device to search for other Bluetooth (BT) devices. The other Mac was not visible until I slept it and woke it up again. Turning BT off and on again via Menu Bar stopped it from being visible, until the Mac was slept and woken again.

I hope that helps. I've replicated on two Macbooks and an iMac, each replicating the same exact behavior when the Mac was slept and woken. The iMac has a fresh install of Lion (not upgrade) as well.

Cheers,

John

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Answer 5

JohnBradshaw Author

Level 4

1,412 points

Oct 8, 2011 11:12 AM in response to JohnBradshaw

As an update, I tried searching from a Windows PC for open BT devices and the Macs were found despite having Discovery mode disabled. Moreover, when I tried to pair with the Mac that had discovery mode disabled, it still attempted to pair with the passkey and everything.

This is a nasty bug.

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Answer 6

thomas_r.

Level 7

31,989 points

Oct 8, 2011 11:29 AM in response to JohnBradshaw

I'm still not convinced this is a bug, especially since I have tried it with my MBP and iMac now. The MBP is running 10.7.1, and I tried different combinations of Bluetooth settings, sleeping and waking between changes, and the iMac (running 10.5) was never able to see the MBP when Discoverable was off.

Had you ever connected to those Macs from the other devices you were testing with? If so, they might remember the Mac. It may not be discoverable to a device that had never connected to it before, but be visible to devices that have found it in the past.

In fact, I just tested that, and in Bluetooth File Exchange on the iMac, if I try to browse the MBP, even if Bluetooth File Sharing is off and the connection is unsuccessful, the MBP still shows up in Bluetooth File Exchange from then on even if Bluetooth is turned off on the MBP.

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Answer 7

JohnBradshaw Author

Level 4

1,412 points

Oct 8, 2011 1:39 PM in response to thomas_r.

Hi Thomas,

Thanks for your input. That's strange. I've been able to repeat this issue on three different Macs, two of which are notebooks, and each of them are running vanilla 10.7.1. Each Mac has BT Discoverability turned off, even shows it as off in the BT menubar pull-down (Option+Click on BT icon).

The only separate device I have tested with that isn't a Mac computer is a PC notebook running Windows XP SP3. I was able to successfully view and attempt to pair with a Mac that had Discoverability turned off. I am not able to see any of the Macs from an iPhone or iPad (iOS 4.3)

I have not tried to use BT File Exchange, only tried to view and pair with the other Mac that has Discovery turned off. The only way to avoid any of the Macs from showing up as a discoverable device it is to turn BT off then on again in the menu bar, or turn Discovery on and off again.

Incidentally, I have never tried to pair any of the Macs with each other, or with the PC before this issue was noticed. They all ran Snow Leopard before Lion, however, the desktop was recently re-formatted and installed with Lion only, no migration.

Hope that helps. I've been able to predictably replicate this issue over and over again so I know I'm not crazy. 😉

The basic recipe for seeing this issue seems to be if BT is left on with discoverability mode turned off on Mac #1, then Mac #1 is slept (to the point the sleep light pulsates) and woken up, it will be seen as a discoverable device from Mac #2 (or PC) when searching for discoverable BT devices. It may take several seconds but it wille ventually show up.

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Answer 8

JohnBradshaw Author

Level 4

1,412 points

Oct 8, 2011 6:51 PM in response to JohnBradshaw

Just an update. I contacted AppleCare about this issue this afternoon. After some brief troubleshooting, I was transferred to a Senior Advisor. The senior advisor with whom I spoke asked for a data capture and is sending it to engineering. I will post back when I have more information on this.

In the meantime, has anyone else replicated it on their end?

PS: Apple is nothing if not awesome about customer service. All support agents are friendly, polite, and (best of all) in North America. After my spat with HP a few weeks ago over a dead external HDD (3+ phone calls and a BBB complaint to get it resolved), I strongly appreciate good customer service when it's available.

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Answer 9

JohnBradshaw Author

Level 4

1,412 points

Oct 19, 2011 1:09 PM in response to JohnBradshaw

Update.

I haven't heard back from Apple yet but I did find the culprit.

"Allow Bluetooth devices to wake computer" -- having this checked is what causes it, I imagine necessary for the BT stack to remain alive while the machine is sleeping. I tested it on all of my Macs and this is precisely what causes it. I turned it off on all Macs and the issue disappeared.

Anyway, it looks to be a false alarm but hopefully if anyone comes across this, they can see what the cause is.

Adios.

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Answer 10

Csound1

Level 9

59,973 points

Oct 19, 2011 1:36 PM in response to JohnBradshaw

John P. wrote:

Update. I found that the workaround is only temporary, lasting until the Mac is put into sleep mode then woken up again. However, turning Bluetooth OFF then ON again seems to clear it up.

Discoverable mode setting in System Preferences does not seem to matter.

I can not replicate this behaviour, turning discoverable off in System Preferences>Bluetooth makes both of my Macs invisible to other Bluetooth devices.

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Answer 11

JohnBradshaw Author

Level 4

1,412 points

Oct 20, 2011 8:04 AM in response to Csound1

Csound1 wrote:

John P. wrote:

Update. I found that the workaround is only temporary, lasting until the Mac is put into sleep mode then woken up again. However, turning Bluetooth OFF then ON again seems to clear it up.

Discoverable mode setting in System Preferences does not seem to matter.

I can not replicate this behaviour, turning discoverable off in System Preferences>Bluetooth makes both of my Macs invisible to other Bluetooth devices.

If you put the Mac to sleep, then wake it, the Mac will show as discoverable even if the option is turned off.

"Allow Bluetooth devices to wake this computer" needs to be checked and is apparently the reason for this issue.

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Answer 12

Jan 14, 2012 6:00 AM in response to JohnBradshaw

I'm experiencing the same over here (Mac Mini, Mac OS X 10.7.2).

I found out about the bug in a quite unpleasant way: someone with a Galaxy Tab was trying to pair with my Mac.

Unchecking "Discoverable" doesn't work. If I go back to the "Show All" SysPrefs view and then back into the BT pane, 'Discoverable' is checked again.

I managed to shut it down by unchecking it, then turning bluetooth OFF, then quitting SysPrefs, then turning bluetooth back ON. After those steps "Discoverable" remains unchecked.

I haven't been able to verify if the computer is in fact invisible to other BT devices, but as far as the checkbox goes, there's definetly a bug there.

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Answer 13

JohnBradshaw Author

Level 4

1,412 points

Jan 14, 2012 8:44 AM in response to santiagofromrichfield

There is a workaround: Turn off "Allow Bluetooth devices to wake this computer" in Bluetooth preferences. Apparently, the two are necessarily related. My guess this is by design so that the BT module stays awake during system sleep.

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Answer 14

Jan 14, 2012 8:53 AM in response to JohnBradshaw

Yeah but the "Discoverable" flag shouldn't affect devices already paired, ie. there should be no reason for making the computer "Discoverable" in order to wake it up, or to keep it that way after it has already woken.

Also, this bug hasn't always been there, but the ability to wake the computer through BT devices goes way back.

Unfortunately both my input devices are BT, so I depend on that particular option to wake the computer up. Thanks for the tip though !

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Answer 15

JohnBradshaw Author

Level 4

1,412 points

Jan 14, 2012 9:03 AM in response to santiagofromrichfield

I agree yet after testing it on three separate Macs (two laptops and an iMac), the behavior is the same on all of them. The issue only appears if Wake from Sleep is checked, and my guess is that it has more to do with Apple's new BT devices (Keyboard, Magic Trackpad, Magic Mouse, etc.) to maintain connections with the Mac even after sleep.

I do not recall if this was replicable under Snow Leopard or not. I, like you, came upon it by accident so hopefully by sending Apple feedback they will address or explain it.

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