1/*
2 * chaoskey - driver for ChaosKey device from Altus Metrum.
3 *
4 * This device provides true random numbers using a noise source based
5 * on a reverse-biased p-n junction in avalanche breakdown. More
6 * details can be found at http://chaoskey.org
7 *
8 * The driver connects to the kernel hardware RNG interface to provide
9 * entropy for /dev/random and other kernel activities. It also offers
10 * a separate /dev/ entry to allow for direct access to the random
11 * bit stream.
12 *
13 * Copyright © 2015 Keith Packard <keithp@keithp.com>
14 *
15 * This program is free software; you can redistribute it and/or modify
16 * it under the terms of the GNU General Public License as published by
17 * the Free Software Foundation; version 2 of the License.
18 *
19 * This program is distributed in the hope that it will be useful, but
20 * WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
22 * General Public License for more details.
23 */
24
25#include <linux/module.h>
26#include <linux/slab.h>
27#include <linux/usb.h>
28#include <linux/wait.h>
29#include <linux/hw_random.h>
30#include <linux/mutex.h>
31#include <linux/uaccess.h>
32
33static struct usb_driver chaoskey_driver;
34static struct usb_class_driver chaoskey_class;
35static int chaoskey_rng_read(struct hwrng *rng, void *data,
36			     size_t max, bool wait);
37
38#define usb_dbg(usb_if, format, arg...) \
39	dev_dbg(&(usb_if)->dev, format, ## arg)
40
41#define usb_err(usb_if, format, arg...) \
42	dev_err(&(usb_if)->dev, format, ## arg)
43
44/* Version Information */
45#define DRIVER_VERSION	"v0.1"
46#define DRIVER_AUTHOR	"Keith Packard, keithp@keithp.com"
47#define DRIVER_DESC	"Altus Metrum ChaosKey driver"
48#define DRIVER_SHORT	"chaoskey"
49
50MODULE_VERSION(DRIVER_VERSION);
51MODULE_AUTHOR(DRIVER_AUTHOR);
52MODULE_DESCRIPTION(DRIVER_DESC);
53MODULE_LICENSE("GPL");
54
55#define CHAOSKEY_VENDOR_ID	0x1d50	/* OpenMoko */
56#define CHAOSKEY_PRODUCT_ID	0x60c6	/* ChaosKey */
57
58#define CHAOSKEY_BUF_LEN	64	/* max size of USB full speed packet */
59
60#define NAK_TIMEOUT (HZ)		/* stall/wait timeout for device */
61
62#ifdef CONFIG_USB_DYNAMIC_MINORS
63#define USB_CHAOSKEY_MINOR_BASE 0
64#else
65
66/* IOWARRIOR_MINOR_BASE + 16, not official yet */
67#define USB_CHAOSKEY_MINOR_BASE 224
68#endif
69
70static const struct usb_device_id chaoskey_table[] = {
71	{ USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) },
72	{ },
73};
74MODULE_DEVICE_TABLE(usb, chaoskey_table);
75
76/* Driver-local specific stuff */
77struct chaoskey {
78	struct usb_interface *interface;
79	char in_ep;
80	struct mutex lock;
81	struct mutex rng_lock;
82	int open;			/* open count */
83	int present;			/* device not disconnected */
84	int size;			/* size of buf */
85	int valid;			/* bytes of buf read */
86	int used;			/* bytes of buf consumed */
87	char *name;			/* product + serial */
88	struct hwrng hwrng;		/* Embedded struct for hwrng */
89	int hwrng_registered;		/* registered with hwrng API */
90	wait_queue_head_t wait_q;	/* for timeouts */
91	char *buf;
92};
93
94static void chaoskey_free(struct chaoskey *dev)
95{
96	usb_dbg(dev->interface, "free");
97	kfree(dev->name);
98	kfree(dev->buf);
99	kfree(dev);
100}
101
102static int chaoskey_probe(struct usb_interface *interface,
103			  const struct usb_device_id *id)
104{
105	struct usb_device *udev = interface_to_usbdev(interface);
106	struct usb_host_interface *altsetting = interface->cur_altsetting;
107	int i;
108	int in_ep = -1;
109	struct chaoskey *dev;
110	int result;
111	int size;
112
113	usb_dbg(interface, "probe %s-%s", udev->product, udev->serial);
114
115	/* Find the first bulk IN endpoint and its packet size */
116	for (i = 0; i < altsetting->desc.bNumEndpoints; i++) {
117		if (usb_endpoint_is_bulk_in(&altsetting->endpoint[i].desc)) {
118			in_ep = usb_endpoint_num(&altsetting->endpoint[i].desc);
119			size = usb_endpoint_maxp(&altsetting->endpoint[i].desc);
120			break;
121		}
122	}
123
124	/* Validate endpoint and size */
125	if (in_ep == -1) {
126		usb_dbg(interface, "no IN endpoint found");
127		return -ENODEV;
128	}
129	if (size <= 0) {
130		usb_dbg(interface, "invalid size (%d)", size);
131		return -ENODEV;
132	}
133
134	if (size > CHAOSKEY_BUF_LEN) {
135		usb_dbg(interface, "size reduced from %d to %d\n",
136			size, CHAOSKEY_BUF_LEN);
137		size = CHAOSKEY_BUF_LEN;
138	}
139
140	/* Looks good, allocate and initialize */
141
142	dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL);
143
144	if (dev == NULL)
145		return -ENOMEM;
146
147	dev->buf = kmalloc(size, GFP_KERNEL);
148
149	if (dev->buf == NULL) {
150		kfree(dev);
151		return -ENOMEM;
152	}
153
154	/* Construct a name using the product and serial values. Each
155	 * device needs a unique name for the hwrng code
156	 */
157
158	if (udev->product && udev->serial) {
159		dev->name = kmalloc(strlen(udev->product) + 1 +
160				    strlen(udev->serial) + 1, GFP_KERNEL);
161		if (dev->name == NULL) {
162			kfree(dev->buf);
163			kfree(dev);
164			return -ENOMEM;
165		}
166
167		strcpy(dev->name, udev->product);
168		strcat(dev->name, "-");
169		strcat(dev->name, udev->serial);
170	}
171
172	dev->interface = interface;
173
174	dev->in_ep = in_ep;
175
176	dev->size = size;
177	dev->present = 1;
178
179	init_waitqueue_head(&dev->wait_q);
180
181	mutex_init(&dev->lock);
182	mutex_init(&dev->rng_lock);
183
184	usb_set_intfdata(interface, dev);
185
186	result = usb_register_dev(interface, &chaoskey_class);
187	if (result) {
188		usb_err(interface, "Unable to allocate minor number.");
189		usb_set_intfdata(interface, NULL);
190		chaoskey_free(dev);
191		return result;
192	}
193
194	dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
195	dev->hwrng.read = chaoskey_rng_read;
196
197	/* Set the 'quality' metric.  Quality is measured in units of
198	 * 1/1024's of a bit ("mills"). This should be set to 1024,
199	 * but there is a bug in the hwrng core which masks it with
200	 * 1023.
201	 *
202	 * The patch that has been merged to the crypto development
203	 * tree for that bug limits the value to 1024 at most, so by
204	 * setting this to 1024 + 1023, we get 1023 before the fix is
205	 * merged and 1024 afterwards. We'll patch this driver once
206	 * both bits of code are in the same tree.
207	 */
208	dev->hwrng.quality = 1024 + 1023;
209
210	dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
211	if (!dev->hwrng_registered)
212		usb_err(interface, "Unable to register with hwrng");
213
214	usb_enable_autosuspend(udev);
215
216	usb_dbg(interface, "chaoskey probe success, size %d", dev->size);
217	return 0;
218}
219
220static void chaoskey_disconnect(struct usb_interface *interface)
221{
222	struct chaoskey	*dev;
223
224	usb_dbg(interface, "disconnect");
225	dev = usb_get_intfdata(interface);
226	if (!dev) {
227		usb_dbg(interface, "disconnect failed - no dev");
228		return;
229	}
230
231	if (dev->hwrng_registered)
232		hwrng_unregister(&dev->hwrng);
233
234	usb_deregister_dev(interface, &chaoskey_class);
235
236	usb_set_intfdata(interface, NULL);
237	mutex_lock(&dev->lock);
238
239	dev->present = 0;
240
241	if (!dev->open) {
242		mutex_unlock(&dev->lock);
243		chaoskey_free(dev);
244	} else
245		mutex_unlock(&dev->lock);
246
247	usb_dbg(interface, "disconnect done");
248}
249
250static int chaoskey_open(struct inode *inode, struct file *file)
251{
252	struct chaoskey *dev;
253	struct usb_interface *interface;
254
255	/* get the interface from minor number and driver information */
256	interface = usb_find_interface(&chaoskey_driver, iminor(inode));
257	if (!interface)
258		return -ENODEV;
259
260	usb_dbg(interface, "open");
261
262	dev = usb_get_intfdata(interface);
263	if (!dev) {
264		usb_dbg(interface, "open (dev)");
265		return -ENODEV;
266	}
267
268	file->private_data = dev;
269	mutex_lock(&dev->lock);
270	++dev->open;
271	mutex_unlock(&dev->lock);
272
273	usb_dbg(interface, "open success");
274	return 0;
275}
276
277static int chaoskey_release(struct inode *inode, struct file *file)
278{
279	struct chaoskey *dev = file->private_data;
280	struct usb_interface *interface;
281
282	if (dev == NULL)
283		return -ENODEV;
284
285	interface = dev->interface;
286
287	usb_dbg(interface, "release");
288
289	mutex_lock(&dev->lock);
290
291	usb_dbg(interface, "open count at release is %d", dev->open);
292
293	if (dev->open <= 0) {
294		usb_dbg(interface, "invalid open count (%d)", dev->open);
295		mutex_unlock(&dev->lock);
296		return -ENODEV;
297	}
298
299	--dev->open;
300
301	if (!dev->present) {
302		if (dev->open == 0) {
303			mutex_unlock(&dev->lock);
304			chaoskey_free(dev);
305		} else
306			mutex_unlock(&dev->lock);
307	} else
308		mutex_unlock(&dev->lock);
309
310	usb_dbg(interface, "release success");
311	return 0;
312}
313
314/* Fill the buffer. Called with dev->lock held
315 */
316static int _chaoskey_fill(struct chaoskey *dev)
317{
318	DEFINE_WAIT(wait);
319	int result;
320	int this_read;
321	struct usb_device *udev = interface_to_usbdev(dev->interface);
322
323	usb_dbg(dev->interface, "fill");
324
325	/* Return immediately if someone called before the buffer was
326	 * empty */
327	if (dev->valid != dev->used) {
328		usb_dbg(dev->interface, "not empty yet (valid %d used %d)",
329			dev->valid, dev->used);
330		return 0;
331	}
332
333	/* Bail if the device has been removed */
334	if (!dev->present) {
335		usb_dbg(dev->interface, "device not present");
336		return -ENODEV;
337	}
338
339	/* Make sure the device is awake */
340	result = usb_autopm_get_interface(dev->interface);
341	if (result) {
342		usb_dbg(dev->interface, "wakeup failed (result %d)", result);
343		return result;
344	}
345
346	result = usb_bulk_msg(udev,
347			      usb_rcvbulkpipe(udev, dev->in_ep),
348			      dev->buf, dev->size, &this_read,
349			      NAK_TIMEOUT);
350
351	/* Let the device go back to sleep eventually */
352	usb_autopm_put_interface(dev->interface);
353
354	if (result == 0) {
355		dev->valid = this_read;
356		dev->used = 0;
357	}
358
359	usb_dbg(dev->interface, "bulk_msg result %d this_read %d",
360		result, this_read);
361
362	return result;
363}
364
365static ssize_t chaoskey_read(struct file *file,
366			     char __user *buffer,
367			     size_t count,
368			     loff_t *ppos)
369{
370	struct chaoskey *dev;
371	ssize_t read_count = 0;
372	int this_time;
373	int result = 0;
374	unsigned long remain;
375
376	dev = file->private_data;
377
378	if (dev == NULL || !dev->present)
379		return -ENODEV;
380
381	usb_dbg(dev->interface, "read %zu", count);
382
383	while (count > 0) {
384
385		/* Grab the rng_lock briefly to ensure that the hwrng interface
386		 * gets priority over other user access
387		 */
388		result = mutex_lock_interruptible(&dev->rng_lock);
389		if (result)
390			goto bail;
391		mutex_unlock(&dev->rng_lock);
392
393		result = mutex_lock_interruptible(&dev->lock);
394		if (result)
395			goto bail;
396		if (dev->valid == dev->used) {
397			result = _chaoskey_fill(dev);
398			if (result) {
399				mutex_unlock(&dev->lock);
400				goto bail;
401			}
402
403			/* Read returned zero bytes */
404			if (dev->used == dev->valid) {
405				mutex_unlock(&dev->lock);
406				goto bail;
407			}
408		}
409
410		this_time = dev->valid - dev->used;
411		if (this_time > count)
412			this_time = count;
413
414		remain = copy_to_user(buffer, dev->buf + dev->used, this_time);
415		if (remain) {
416			result = -EFAULT;
417
418			/* Consume the bytes that were copied so we don't leak
419			 * data to user space
420			 */
421			dev->used += this_time - remain;
422			mutex_unlock(&dev->lock);
423			goto bail;
424		}
425
426		count -= this_time;
427		read_count += this_time;
428		buffer += this_time;
429		dev->used += this_time;
430		mutex_unlock(&dev->lock);
431	}
432bail:
433	if (read_count) {
434		usb_dbg(dev->interface, "read %zu bytes", read_count);
435		return read_count;
436	}
437	usb_dbg(dev->interface, "empty read, result %d", result);
438	return result;
439}
440
441static int chaoskey_rng_read(struct hwrng *rng, void *data,
442			     size_t max, bool wait)
443{
444	struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
445	int this_time;
446
447	usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait);
448
449	if (!dev->present) {
450		usb_dbg(dev->interface, "device not present");
451		return 0;
452	}
453
454	/* Hold the rng_lock until we acquire the device lock so that
455	 * this operation gets priority over other user access to the
456	 * device
457	 */
458	mutex_lock(&dev->rng_lock);
459
460	mutex_lock(&dev->lock);
461
462	mutex_unlock(&dev->rng_lock);
463
464	/* Try to fill the buffer if empty. It doesn't actually matter
465	 * if _chaoskey_fill works; we'll just return zero bytes as
466	 * the buffer will still be empty
467	 */
468	if (dev->valid == dev->used)
469		(void) _chaoskey_fill(dev);
470
471	this_time = dev->valid - dev->used;
472	if (this_time > max)
473		this_time = max;
474
475	memcpy(data, dev->buf + dev->used, this_time);
476
477	dev->used += this_time;
478
479	mutex_unlock(&dev->lock);
480
481	usb_dbg(dev->interface, "rng_read this_time %d\n", this_time);
482	return this_time;
483}
484
485#ifdef CONFIG_PM
486static int chaoskey_suspend(struct usb_interface *interface,
487			    pm_message_t message)
488{
489	usb_dbg(interface, "suspend");
490	return 0;
491}
492
493static int chaoskey_resume(struct usb_interface *interface)
494{
495	usb_dbg(interface, "resume");
496	return 0;
497}
498#else
499#define chaoskey_suspend NULL
500#define chaoskey_resume NULL
501#endif
502
503/* file operation pointers */
504static const struct file_operations chaoskey_fops = {
505	.owner = THIS_MODULE,
506	.read = chaoskey_read,
507	.open = chaoskey_open,
508	.release = chaoskey_release,
509	.llseek = default_llseek,
510};
511
512/* class driver information */
513static struct usb_class_driver chaoskey_class = {
514	.name = "chaoskey%d",
515	.fops = &chaoskey_fops,
516	.minor_base = USB_CHAOSKEY_MINOR_BASE,
517};
518
519/* usb specific object needed to register this driver with the usb subsystem */
520static struct usb_driver chaoskey_driver = {
521	.name = DRIVER_SHORT,
522	.probe = chaoskey_probe,
523	.disconnect = chaoskey_disconnect,
524	.suspend = chaoskey_suspend,
525	.resume = chaoskey_resume,
526	.reset_resume = chaoskey_resume,
527	.id_table = chaoskey_table,
528	.supports_autosuspend = 1,
529};
530
531module_usb_driver(chaoskey_driver);
532
533