Subject: Re: [PATCH] HID: add driver for U2F Zero built-in LED and RNG
To: =?UTF-8?B?SmnFmcOtIEtvc2luYQ==?= <jikos@kernel.org>
Cc: linux-input@vger.kernel.org, linux-usb@vger.kernel.org,
        kernel@collabora.com, Vasily Khoruzhick <anarsoul@gmail.com>,
        Nick Kossifidis <mickflemm@gmail.com>,
        linux-crypto@vger.kernel.org
References: <20181023144654.12906-1-andrew.shadura@collabora.co.uk>
 <d848f97e-a9fc-1562-1963-3b608162106d@collabora.co.uk>
 <nycvar.YFH.7.76.1811121217030.27368@cbobk.fhfr.pm>
From: Andrej Shadura <andrew.shadura@collabora.co.uk>
Message-ID: <96148aff-eac8-7e25-dd74-b194b7bae025@collabora.co.uk>
Date: Wed, 14 Nov 2018 10:32:56 -0800
MIME-Version: 1.0
In-Reply-To: <nycvar.YFH.7.76.1811121217030.27368@cbobk.fhfr.pm>
Content-Type: text/plain; charset=utf-8
Content-Language: en-GB
Content-Transfer-Encoding: 8bit
Sender: linux-crypto-owner@vger.kernel.org

On 12/11/2018 03:17, Jiri Kosina wrote:
> On Thu, 1 Nov 2018, Andrej Shadura wrote:
> 
>> Hi everyone,
>>
>> I’ve got a comment from Nick Kossifidis that I probably shouldn’t set
>> RNG’s quality to 1024. Adding linux-crypto@ to the loop.
> 
> So, what was this about? Is there any resolution to it? :)

So far, not really. I talked to Keith Packard regarding a similar
setting in his ChaosKey driver, and I understand his opinion is that it
is appropriate there since he’s convinced about the quality of the
hardware he designed. I’m not sure what exactly I should set it to here.

>>
>> On 23/10/2018 16:46, Andrej Shadura wrote:
>>> U2F Zero supports custom commands for blinking the LED and getting data
>>> from the internal hardware RNG. Expose the blinking function as a LED
>>> device, and the internal hardware RNG as an HWRNG so that it can be used
>>> to feed the enthropy pool.
>>>
>>> Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>
>>> ---
>>>  drivers/hid/Kconfig       |  15 ++
>>>  drivers/hid/Makefile      |   1 +
>>>  drivers/hid/hid-ids.h     |   1 +
>>>  drivers/hid/hid-u2fzero.c | 371 ++++++++++++++++++++++++++++++++++++++
>>>  4 files changed, 388 insertions(+)
>>>  create mode 100644 drivers/hid/hid-u2fzero.c
>>>
>>> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
>>> index 61e1953ff921..3de6bf202f20 100644
>>> --- a/drivers/hid/Kconfig
>>> +++ b/drivers/hid/Kconfig
>>> @@ -975,6 +975,21 @@ config HID_UDRAW_PS3
>>>  	  Say Y here if you want to use the THQ uDraw gaming tablet for
>>>  	  the PS3.
>>>  
>>> +config HID_U2FZERO
>>> +	tristate "U2F Zero LED and RNG support"
>>> +	depends on HID
>>> +	depends on LEDS_CLASS
>>> +	help
>>> +	  Support for the LED of the U2F Zero device.
>>> +
>>> +	  U2F Zero supports custom commands for blinking the LED
>>> +	  and getting data from the internal hardware RNG.
>>> +	  The internal hardware can be used to feed the enthropy pool.
>>> +
>>> +	  U2F Zero only supports blinking its LED, so this driver doesn't
>>> +	  allow setting the brightness to anything but 1, which will
>>> +	  trigger a single blink and immediately reset to back 0.
>>> +
>>>  config HID_WACOM
>>>  	tristate "Wacom Intuos/Graphire tablet support (USB)"
>>>  	depends on USB_HID
>>> diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
>>> index bd7ac53b75c5..617b1a928b6a 100644
>>> --- a/drivers/hid/Makefile
>>> +++ b/drivers/hid/Makefile
>>> @@ -107,6 +107,7 @@ obj-$(CONFIG_HID_THRUSTMASTER)	+= hid-tmff.o
>>>  obj-$(CONFIG_HID_TIVO)		+= hid-tivo.o
>>>  obj-$(CONFIG_HID_TOPSEED)	+= hid-topseed.o
>>>  obj-$(CONFIG_HID_TWINHAN)	+= hid-twinhan.o
>>> +obj-$(CONFIG_HID_U2FZERO)	+= hid-u2fzero.o
>>>  obj-$(CONFIG_HID_UCLOGIC)	+= hid-uclogic.o
>>>  obj-$(CONFIG_HID_UDRAW_PS3)	+= hid-udraw-ps3.o
>>>  obj-$(CONFIG_HID_LED)		+= hid-led.o
>>> diff --git a/drivers/hid/hid-ids.h b/drivers/hid/hid-ids.h
>>> index bc49909aba8e..070a2fcd8a18 100644
>>> --- a/drivers/hid/hid-ids.h
>>> +++ b/drivers/hid/hid-ids.h
>>> @@ -309,6 +309,7 @@
>>>  #define USB_DEVICE_ID_CYGNAL_RADIO_SI470X	0x818a
>>>  #define USB_DEVICE_ID_FOCALTECH_FTXXXX_MULTITOUCH	0x81b9
>>>  #define USB_DEVICE_ID_CYGNAL_CP2112	0xea90
>>> +#define USB_DEVICE_ID_U2F_ZERO		0x8acf
>>>  
>>>  #define USB_DEVICE_ID_CYGNAL_RADIO_SI4713       0x8244
>>>  
>>> diff --git a/drivers/hid/hid-u2fzero.c b/drivers/hid/hid-u2fzero.c
>>> new file mode 100644
>>> index 000000000000..bd4077c93c97
>>> --- /dev/null
>>> +++ b/drivers/hid/hid-u2fzero.c
>>> @@ -0,0 +1,371 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * U2F Zero LED and RNG driver
>>> + *
>>> + * Copyright 2018 Andrej Shadura <andrew@shadura.me>
>>> + * Loosely based on drivers/hid/hid-led.c
>>> + *              and drivers/usb/misc/chaoskey.c
>>> + *
>>> + * This program is free software; you can redistribute it and/or
>>> + * modify it under the terms of the GNU General Public License as
>>> + * published by the Free Software Foundation, version 2.
>>> + */
>>> +
>>> +#include <linux/hid.h>
>>> +#include <linux/hidraw.h>
>>> +#include <linux/hw_random.h>
>>> +#include <linux/leds.h>
>>> +#include <linux/module.h>
>>> +#include <linux/mutex.h>
>>> +#include <linux/usb.h>
>>> +
>>> +#include "usbhid/usbhid.h"
>>> +#include "hid-ids.h"
>>> +
>>> +#define DRIVER_SHORT		"u2fzero"
>>> +
>>> +#define HID_REPORT_SIZE		64
>>> +
>>> +/* We only use broadcast (CID-less) messages */
>>> +#define CID_BROADCAST		0xffffffff
>>> +
>>> +struct u2f_hid_msg {
>>> +	u32 cid;
>>> +	union {
>>> +		struct {
>>> +			u8 cmd;
>>> +			u8 bcnth;
>>> +			u8 bcntl;
>>> +			u8 data[HID_REPORT_SIZE - 7];
>>> +		} init;
>>> +		struct {
>>> +			u8 seq;
>>> +			u8 data[HID_REPORT_SIZE - 5];
>>> +		} cont;
>>> +	};
>>> +} __packed;
>>> +
>>> +struct u2f_hid_report {
>>> +	u8 report_type;
>>> +	struct u2f_hid_msg msg;
>>> +} __packed;
>>> +
>>> +#define U2F_HID_MSG_LEN(f)	(size_t)(((f).init.bcnth << 8) + (f).init.bcntl)
>>> +
>>> +/* Custom extensions to the U2FHID protocol */
>>> +#define U2F_CUSTOM_GET_RNG	0x21
>>> +#define U2F_CUSTOM_WINK		0x24
>>> +
>>> +struct u2fzero_device {
>>> +	struct hid_device	*hdev;
>>> +	struct urb		*urb;	    /* URB for the RNG data */
>>> +	struct led_classdev	ldev;	    /* Embedded struct for led */
>>> +	struct hwrng		hwrng;	    /* Embedded struct for hwrng */
>>> +	char			*led_name;
>>> +	char			*rng_name;
>>> +	u8			*buf_out;
>>> +	u8			*buf_in;
>>> +	struct mutex		lock;
>>> +	bool			present;
>>> +};
>>> +
>>> +static int u2fzero_send(struct u2fzero_device *dev, struct u2f_hid_report *req)
>>> +{
>>> +	int ret;
>>> +
>>> +	mutex_lock(&dev->lock);
>>> +
>>> +	memcpy(dev->buf_out, req, sizeof(struct u2f_hid_report));
>>> +
>>> +	ret = hid_hw_output_report(dev->hdev, dev->buf_out,
>>> +				   sizeof(struct u2f_hid_msg));
>>> +
>>> +	mutex_unlock(&dev->lock);
>>> +
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	return ret == sizeof(struct u2f_hid_msg) ? 0 : -EMSGSIZE;
>>> +}
>>> +
>>> +struct u2fzero_transfer_context {
>>> +	struct completion done;
>>> +	int status;
>>> +};
>>> +
>>> +static void u2fzero_read_callback(struct urb *urb)
>>> +{
>>> +	struct u2fzero_transfer_context *ctx = urb->context;
>>> +
>>> +	ctx->status = urb->status;
>>> +	complete(&ctx->done);
>>> +}
>>> +
>>> +static int u2fzero_recv(struct u2fzero_device *dev,
>>> +			struct u2f_hid_report *req,
>>> +			struct u2f_hid_msg *resp)
>>> +{
>>> +	int ret;
>>> +	struct hid_device *hdev = dev->hdev;
>>> +	struct u2fzero_transfer_context ctx;
>>> +
>>> +	mutex_lock(&dev->lock);
>>> +
>>> +	memcpy(dev->buf_out, req, sizeof(struct u2f_hid_report));
>>> +
>>> +	dev->urb->context = &ctx;
>>> +	init_completion(&ctx.done);
>>> +
>>> +	ret = usb_submit_urb(dev->urb, GFP_NOIO);
>>> +	if (unlikely(ret)) {
>>> +		hid_err(hdev, "usb_submit_urb failed: %d", ret);
>>> +		goto err;
>>> +	}
>>> +
>>> +	ret = hid_hw_output_report(dev->hdev, dev->buf_out,
>>> +				   sizeof(struct u2f_hid_msg));
>>> +
>>> +	if (ret < 0) {
>>> +		hid_err(hdev, "hid_hw_output_report failed: %d", ret);
>>> +		goto err;
>>> +	}
>>> +
>>> +	ret = (wait_for_completion_timeout(
>>> +		&ctx.done, msecs_to_jiffies(USB_CTRL_SET_TIMEOUT)));
>>> +	if (ret < 0) {
>>> +		usb_kill_urb(dev->urb);
>>> +		hid_err(hdev, "urb submission timed out");
>>> +	} else {
>>> +		ret = dev->urb->actual_length;
>>> +		memcpy(resp, dev->buf_in, ret);
>>> +	}
>>> +
>>> +err:
>>> +	mutex_unlock(&dev->lock);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +static int u2fzero_blink(struct led_classdev *ldev)
>>> +{
>>> +	struct u2fzero_device *dev = container_of(ldev,
>>> +		struct u2fzero_device, ldev);
>>> +	struct u2f_hid_report req = {
>>> +		.report_type = 0,
>>> +		.msg.cid = CID_BROADCAST,
>>> +		.msg.init = {
>>> +			.cmd = U2F_CUSTOM_WINK,
>>> +			.bcnth = 0,
>>> +			.bcntl = 0,
>>> +			.data  = {0},
>>> +		}
>>> +	};
>>> +	return u2fzero_send(dev, &req);
>>> +}
>>> +
>>> +static int u2fzero_brightness_set(struct led_classdev *ldev,
>>> +				  enum led_brightness brightness)
>>> +{
>>> +	ldev->brightness = LED_OFF;
>>> +	if (brightness)
>>> +		return u2fzero_blink(ldev);
>>> +	else
>>> +		return 0;
>>> +}
>>> +
>>> +static int u2fzero_rng_read(struct hwrng *rng, void *data,
>>> +			    size_t max, bool wait)
>>> +{
>>> +	struct u2fzero_device *dev = container_of(rng,
>>> +		struct u2fzero_device, hwrng);
>>> +	struct u2f_hid_report req = {
>>> +		.report_type = 0,
>>> +		.msg.cid = CID_BROADCAST,
>>> +		.msg.init = {
>>> +			.cmd = U2F_CUSTOM_GET_RNG,
>>> +			.bcnth = 0,
>>> +			.bcntl = 0,
>>> +			.data  = {0},
>>> +		}
>>> +	};
>>> +	struct u2f_hid_msg resp;
>>> +	int ret;
>>> +	size_t actual_length;
>>> +
>>> +	if (!dev->present) {
>>> +		hid_dbg(dev->hdev, "device not present");
>>> +		return 0;
>>> +	}
>>> +
>>> +	ret = u2fzero_recv(dev, &req, &resp);
>>> +	if (ret < 0)
>>> +		return 0;
>>> +
>>> +	/* only take the minimum amount of data it is safe to take */
>>> +	actual_length = min3((size_t)ret - offsetof(struct u2f_hid_msg,
>>> +		init.data), U2F_HID_MSG_LEN(resp), max);
>>> +
>>> +	memcpy(data, resp.init.data, actual_length);
>>> +
>>> +	return actual_length;
>>> +}
>>> +
>>> +static int u2fzero_init_led(struct u2fzero_device *dev,
>>> +			    unsigned int minor)
>>> +{
>>> +	dev->led_name = devm_kasprintf(&dev->hdev->dev, GFP_KERNEL,
>>> +		"%s%u", DRIVER_SHORT, minor);
>>> +	if (dev->led_name == NULL)
>>> +		return -ENOMEM;
>>> +
>>> +	dev->ldev.name = dev->led_name;
>>> +	dev->ldev.max_brightness = LED_ON;
>>> +	dev->ldev.flags = LED_HW_PLUGGABLE;
>>> +	dev->ldev.brightness_set_blocking = u2fzero_brightness_set;
>>> +
>>> +	return devm_led_classdev_register(&dev->hdev->dev, &dev->ldev);
>>> +}
>>> +
>>> +static int u2fzero_init_hwrng(struct u2fzero_device *dev,
>>> +			      unsigned int minor)
>>> +{
>>> +	dev->rng_name = devm_kasprintf(&dev->hdev->dev, GFP_KERNEL,
>>> +		"%s-rng%u", DRIVER_SHORT, minor);
>>> +	if (dev->rng_name == NULL)
>>> +		return -ENOMEM;
>>> +
>>> +	dev->hwrng.name = dev->rng_name;
>>> +	dev->hwrng.read = u2fzero_rng_read;
>>> +	dev->hwrng.quality = 1024;
>>> +
>>> +	return devm_hwrng_register(&dev->hdev->dev, &dev->hwrng);
>>> +}
>>> +
>>> +static int u2fzero_fill_in_urb(struct u2fzero_device *dev)
>>> +{
>>> +	struct hid_device *hdev = dev->hdev;
>>> +	struct usb_device *udev;
>>> +	struct usbhid_device *usbhid = hdev->driver_data;
>>> +	unsigned int pipe_in;
>>> +	struct usb_host_endpoint *ep;
>>> +
>>> +	if (dev->hdev->bus != BUS_USB)
>>> +		return -EINVAL;
>>> +
>>> +	udev = hid_to_usb_dev(hdev);
>>> +
>>> +	if (!usbhid->urbout || !usbhid->urbin)
>>> +		return -ENODEV;
>>> +
>>> +	ep = usb_pipe_endpoint(udev, usbhid->urbin->pipe);
>>> +	if (!ep)
>>> +		return -ENODEV;
>>> +
>>> +	dev->urb = usb_alloc_urb(0, GFP_KERNEL);
>>> +	if (!dev->urb)
>>> +		return -ENOMEM;
>>> +
>>> +	pipe_in = (usbhid->urbin->pipe & ~(3 << 30)) | (PIPE_INTERRUPT << 30);
>>> +
>>> +	usb_fill_int_urb(dev->urb,
>>> +		udev,
>>> +		pipe_in,
>>> +		dev->buf_in,
>>> +		HID_REPORT_SIZE,
>>> +		u2fzero_read_callback,
>>> +		NULL,
>>> +		ep->desc.bInterval);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int u2fzero_probe(struct hid_device *hdev,
>>> +			 const struct hid_device_id *id)
>>> +{
>>> +	struct u2fzero_device *dev;
>>> +	unsigned int minor;
>>> +	int ret;
>>> +
>>> +	dev = devm_kzalloc(&hdev->dev, sizeof(*dev), GFP_KERNEL);
>>> +	if (dev == NULL)
>>> +		return -ENOMEM;
>>> +
>>> +	dev->buf_out = devm_kmalloc(&hdev->dev,
>>> +		sizeof(struct u2f_hid_report), GFP_KERNEL);
>>> +	if (dev->buf_out == NULL)
>>> +		return -ENOMEM;
>>> +
>>> +	dev->buf_in = devm_kmalloc(&hdev->dev,
>>> +		sizeof(struct u2f_hid_msg), GFP_KERNEL);
>>> +	if (dev->buf_in == NULL)
>>> +		return -ENOMEM;
>>> +
>>> +	ret = hid_parse(hdev);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	dev->hdev = hdev;
>>> +	hid_set_drvdata(hdev, dev);
>>> +	mutex_init(&dev->lock);
>>> +
>>> +	ret = hid_hw_start(hdev, HID_CONNECT_HIDRAW);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	u2fzero_fill_in_urb(dev);
>>> +
>>> +	dev->present = true;
>>> +
>>> +	minor = ((struct hidraw *) hdev->hidraw)->minor;
>>> +
>>> +	ret = u2fzero_init_led(dev, minor);
>>> +	if (ret) {
>>> +		hid_hw_stop(hdev);
>>> +		return ret;
>>> +	}
>>> +
>>> +	hid_info(hdev, "U2F Zero LED initialised\n");
>>> +
>>> +	ret = u2fzero_init_hwrng(dev, minor);
>>> +	if (ret) {
>>> +		hid_hw_stop(hdev);
>>> +		return ret;
>>> +	}
>>> +
>>> +	hid_info(hdev, "U2F Zero RNG initialised\n");
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static void u2fzero_remove(struct hid_device *hdev)
>>> +{
>>> +	struct u2fzero_device *dev = hid_get_drvdata(hdev);
>>> +
>>> +	mutex_lock(&dev->lock);
>>> +	dev->present = false;
>>> +	mutex_unlock(&dev->lock);
>>> +
>>> +	hid_hw_stop(hdev);
>>> +	usb_poison_urb(dev->urb);
>>> +	usb_free_urb(dev->urb);
>>> +}
>>> +
>>> +static const struct hid_device_id u2fzero_table[] = {
>>> +	{ HID_USB_DEVICE(USB_VENDOR_ID_CYGNAL,
>>> +	  USB_DEVICE_ID_U2F_ZERO) },
>>> +	{ }
>>> +};
>>> +MODULE_DEVICE_TABLE(hid, u2fzero_table);
>>> +
>>> +static struct hid_driver u2fzero_driver = {
>>> +	.name = "hid-" DRIVER_SHORT,
>>> +	.probe = u2fzero_probe,
>>> +	.remove = u2fzero_remove,
>>> +	.id_table = u2fzero_table,
>>> +};
>>> +
>>> +module_hid_driver(u2fzero_driver);
>>> +
>>> +MODULE_LICENSE("GPL");
>>> +MODULE_AUTHOR("Andrej Shadura <andrew@shadura.me>");
>>> +MODULE_DESCRIPTION("U2F Zero LED and RNG driver");
>>>
>>
>>
>> -- 
>> Cheers,
>>   Andrej
>>
> 


-- 
Cheers,
  Andrej