[PATCH 4/6] usb: kbd: Ignore Yubikeys

[Janne Grunau]

Hej,

On Mon, Feb 26, 2024, at 21:47, Mark Kettenis wrote:
>> Date: Sun, 25 Feb 2024 22:57:23 +0100
>> From: Marek Vasut <marex at denx.de>
>> 
>> On 2/25/24 5:07 PM, Janne Grunau wrote:
>> > Hej,
>> > 
>> > On Wed, Feb 21, 2024, at 13:41, Marek Vasut wrote:
>> >> On 2/21/24 08:25, Janne Grunau via B4 Relay wrote:
>> >>> From: Hector Martin <marcan at marcan.st>
>> >>>
>> >>> We currently only support one USB keyboard device, but some devices
>> >>> emulate keyboards for other purposes. Most commonly, people run into
>> >>> this with Yubikeys, so let's ignore those.
>> >>>
>> >>> Even if we end up supporting multiple keyboards in the future, it's
>> >>> safer to ignore known non-keyboard devices.
>> >>>
>> >>> Signed-off-by: Hector Martin <marcan at marcan.st>
>> >>> ---
>> >>>    common/usb_kbd.c | 19 +++++++++++++++++++
>> >>>    1 file changed, 19 insertions(+)
>> >>>
>> >>> diff --git a/common/usb_kbd.c b/common/usb_kbd.c
>> >>> index 4cbc9acb73..774d3555d9 100644
>> >>> --- a/common/usb_kbd.c
>> >>> +++ b/common/usb_kbd.c
>> >>> @@ -120,6 +120,15 @@ struct usb_kbd_pdata {
>> >>>    
>> >>>    extern int __maybe_unused net_busy_flag;
>> >>>    
>> >>> +/*
>> >>> + * Since we only support one usbkbd device in the iomux,
>> >>> + * ignore common keyboard-emulating devices that aren't
>> >>> + * real keyboards.
>> >>> + */
>> >>> +const uint16_t vid_blocklist[] = {
>> >>> +	0x1050, /* Yubico */
>> >>> +};
>> >>> +
>> >>>    /* The period of time between two calls of usb_kbd_testc(). */
>> >>>    static unsigned long kbd_testc_tms;
>> >>>    
>> >>> @@ -465,6 +474,7 @@ static int usb_kbd_probe_dev(struct usb_device *dev, unsigned int ifnum)
>> >>>    	struct usb_endpoint_descriptor *ep;
>> >>>    	struct usb_kbd_pdata *data;
>> >>>    	int epNum;
>> >>> +	int i;
>> >>>    
>> >>>    	if (dev->descriptor.bNumConfigurations != 1)
>> >>>    		return 0;
>> >>> @@ -480,6 +490,15 @@ static int usb_kbd_probe_dev(struct usb_device *dev, unsigned int ifnum)
>> >>>    	if (iface->desc.bInterfaceProtocol != USB_PROT_HID_KEYBOARD)
>> >>>    		return 0;
>> >>>    
>> >>> +	for (i = 0; i < ARRAY_SIZE(vid_blocklist); i++) {
>> >>> +		if (dev->descriptor.idVendor == vid_blocklist[i]) {
>> >>> +			printf("Ignoring keyboard device 0x%x:0x%x\n",
>> >>> +			       dev->descriptor.idVendor,
>> >>> +			       dev->descriptor.idProduct);
>> >>> +			return 0;
>> >>> +		}
>> >>> +	}
>> >>
>> >> I vaguely recall a discussion about previous version of this, I think
>> >> the suggestion was to make the list of ignored devices configurable via
>> >> environment variable, so users can add to that list from U-Boot shell.
>> >> Would it be possible to make it work this way ?
>> > 
>> > oh, I completely forgot that this patch was already submitted. I briefly looked through asahi tree for related patches and did not check whether this was previously submitted.
>> > I've added environment based blocking as separate patch with blocking either complete vendor IDs or vendor, product ID combinations. A separate patch to simplify authorship tracking and the implementation doesn't share any code.
>> 
>> It would be better to have only one patch which does not hard-code any 
>> USB IDs, and then add those blocked IDs via U-Boot default environment 
>> for this specific machine. We cannot predict what yubico will do in the 
>> future, whether they might make a device that shouldn't be blocked for 
>> example. If they do, the user should be able to unblock their device by 
>> running e.g. '=> setenv usb_blocklist' instead of updating their bootloader.
>> 
>> I think a simple list of blocked VID:PID pairs, maybe with wildcards, 
>> would be nice, i.e. something like 'usb_blocklist=1234:5678,1050:*' to 
>> block device 0x1234:0x5678 and all devices with VID 0x1050 . That should 
>> be easy to parse with strtok()/strtol() or some such and the code should 
>> not be too complex.
>
> I do like the idea of having a configurable list of usb devices to
> ignore.  The U-Boot USB stack is still not perfect and there are still
> USB devices that will prevent us from booting when connected.  The
> list will provide a nice workaround for that issue.

That sounds like we should ignore USB devices in usb_scan_device() and not in the keyboard driver.

> But the yubikeys will cause the same problem on other boards as well.
> So I think it makes sense to put those in a default list.

We could move the list to a CONFIG symbol which has Yubikey's vendor ID as default value now that we do string parsing anyway.

Janne