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

[Marek Vasut]

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.