1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * chaoskey - driver for ChaosKey device from Altus Metrum.
4 *
5 * This device provides true random numbers using a noise source based
6 * on a reverse-biased p-n junction in avalanche breakdown. More
7 * details can be found at http://chaoskey.org
8 *
9 * The driver connects to the kernel hardware RNG interface to provide
10 * entropy for /dev/random and other kernel activities. It also offers
11 * a separate /dev/ entry to allow for direct access to the random
12 * bit stream.
13 *
14 * Copyright © 2015 Keith Packard <keithp@keithp.com>
15 */
16
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/usb.h>
20 #include <linux/wait.h>
21 #include <linux/hw_random.h>
22 #include <linux/mutex.h>
23 #include <linux/uaccess.h>
24
25 static struct usb_driver chaoskey_driver;
26 static struct usb_class_driver chaoskey_class;
27 static int chaoskey_rng_read(struct hwrng *rng, void *data,
28 size_t max, bool wait);
29
30 static DEFINE_MUTEX(chaoskey_list_lock);
31
32 #define usb_dbg(usb_if, format, arg...) \
33 dev_dbg(&(usb_if)->dev, format, ## arg)
34
35 #define usb_err(usb_if, format, arg...) \
36 dev_err(&(usb_if)->dev, format, ## arg)
37
38 /* Version Information */
39 #define DRIVER_AUTHOR "Keith Packard, keithp@keithp.com"
40 #define DRIVER_DESC "Altus Metrum ChaosKey driver"
41 #define DRIVER_SHORT "chaoskey"
42
43 MODULE_AUTHOR(DRIVER_AUTHOR);
44 MODULE_DESCRIPTION(DRIVER_DESC);
45 MODULE_LICENSE("GPL");
46
47 #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */
48 #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */
49
50 #define ALEA_VENDOR_ID 0x12d8 /* Araneus */
51 #define ALEA_PRODUCT_ID 0x0001 /* Alea I */
52
53 #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */
54
55 #define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */
56 #define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */
57
58 #ifdef CONFIG_USB_DYNAMIC_MINORS
59 #define USB_CHAOSKEY_MINOR_BASE 0
60 #else
61
62 /* IOWARRIOR_MINOR_BASE + 16, not official yet */
63 #define USB_CHAOSKEY_MINOR_BASE 224
64 #endif
65
66 static const struct usb_device_id chaoskey_table[] = {
67 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) },
68 { USB_DEVICE(ALEA_VENDOR_ID, ALEA_PRODUCT_ID) },
69 { },
70 };
71 MODULE_DEVICE_TABLE(usb, chaoskey_table);
72
73 static void chaos_read_callback(struct urb *urb);
74
75 /* Driver-local specific stuff */
76 struct chaoskey {
77 struct usb_interface *interface;
78 char in_ep;
79 struct mutex lock;
80 struct mutex rng_lock;
81 int open; /* open count */
82 bool present; /* device not disconnected */
83 bool reading; /* ongoing IO */
84 bool reads_started; /* track first read for Alea */
85 int size; /* size of buf */
86 int valid; /* bytes of buf read */
87 int used; /* bytes of buf consumed */
88 char *name; /* product + serial */
89 struct hwrng hwrng; /* Embedded struct for hwrng */
90 int hwrng_registered; /* registered with hwrng API */
91 wait_queue_head_t wait_q; /* for timeouts */
92 struct urb *urb; /* for performing IO */
93 char *buf;
94 };
95
chaoskey_free(struct chaoskey * dev)96 static void chaoskey_free(struct chaoskey *dev)
97 {
98 if (dev) {
99 usb_dbg(dev->interface, "free");
100 usb_free_urb(dev->urb);
101 kfree(dev->name);
102 kfree(dev->buf);
103 usb_put_intf(dev->interface);
104 kfree(dev);
105 }
106 }
107
chaoskey_probe(struct usb_interface * interface,const struct usb_device_id * id)108 static int chaoskey_probe(struct usb_interface *interface,
109 const struct usb_device_id *id)
110 {
111 struct usb_device *udev = interface_to_usbdev(interface);
112 struct usb_host_interface *altsetting = interface->cur_altsetting;
113 struct usb_endpoint_descriptor *epd;
114 int in_ep;
115 struct chaoskey *dev;
116 int result = -ENOMEM;
117 int size;
118 int res;
119
120 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial);
121
122 /* Find the first bulk IN endpoint and its packet size */
123 res = usb_find_bulk_in_endpoint(altsetting, &epd);
124 if (res) {
125 usb_dbg(interface, "no IN endpoint found");
126 return res;
127 }
128
129 in_ep = usb_endpoint_num(epd);
130 size = usb_endpoint_maxp(epd);
131
132 /* Validate endpoint and size */
133 if (size <= 0) {
134 usb_dbg(interface, "invalid size (%d)", size);
135 return -ENODEV;
136 }
137
138 if (size > CHAOSKEY_BUF_LEN) {
139 usb_dbg(interface, "size reduced from %d to %d\n",
140 size, CHAOSKEY_BUF_LEN);
141 size = CHAOSKEY_BUF_LEN;
142 }
143
144 /* Looks good, allocate and initialize */
145
146 dev = kzalloc_obj(struct chaoskey);
147
148 if (dev == NULL)
149 goto out;
150
151 dev->interface = usb_get_intf(interface);
152
153 dev->buf = kmalloc(size, GFP_KERNEL);
154
155 if (dev->buf == NULL)
156 goto out;
157
158 dev->urb = usb_alloc_urb(0, GFP_KERNEL);
159
160 if (!dev->urb)
161 goto out;
162
163 usb_fill_bulk_urb(dev->urb,
164 udev,
165 usb_rcvbulkpipe(udev, in_ep),
166 dev->buf,
167 size,
168 chaos_read_callback,
169 dev);
170
171 /* Construct a name using the product and serial values. Each
172 * device needs a unique name for the hwrng code
173 */
174
175 if (udev->product && udev->serial) {
176 dev->name = kasprintf(GFP_KERNEL, "%s-%s", udev->product,
177 udev->serial);
178 if (dev->name == NULL)
179 goto out;
180 }
181
182 dev->in_ep = in_ep;
183
184 if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID)
185 dev->reads_started = true;
186
187 dev->size = size;
188 dev->present = true;
189
190 init_waitqueue_head(&dev->wait_q);
191
192 mutex_init(&dev->lock);
193 mutex_init(&dev->rng_lock);
194
195 usb_set_intfdata(interface, dev);
196
197 result = usb_register_dev(interface, &chaoskey_class);
198 if (result) {
199 usb_err(interface, "Unable to allocate minor number.");
200 goto out;
201 }
202
203 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
204 dev->hwrng.read = chaoskey_rng_read;
205
206 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
207 if (!dev->hwrng_registered)
208 usb_err(interface, "Unable to register with hwrng");
209
210 usb_enable_autosuspend(udev);
211
212 usb_dbg(interface, "chaoskey probe success, size %d", dev->size);
213 return 0;
214
215 out:
216 usb_set_intfdata(interface, NULL);
217 chaoskey_free(dev);
218 return result;
219 }
220
chaoskey_disconnect(struct usb_interface * interface)221 static void chaoskey_disconnect(struct usb_interface *interface)
222 {
223 struct chaoskey *dev;
224
225 usb_dbg(interface, "disconnect");
226 dev = usb_get_intfdata(interface);
227 if (!dev) {
228 usb_dbg(interface, "disconnect failed - no dev");
229 return;
230 }
231
232 if (dev->hwrng_registered)
233 hwrng_unregister(&dev->hwrng);
234
235 usb_deregister_dev(interface, &chaoskey_class);
236
237 usb_set_intfdata(interface, NULL);
238 mutex_lock(&chaoskey_list_lock);
239 mutex_lock(&dev->lock);
240
241 dev->present = false;
242 usb_poison_urb(dev->urb);
243
244 if (!dev->open) {
245 mutex_unlock(&dev->lock);
246 chaoskey_free(dev);
247 } else
248 mutex_unlock(&dev->lock);
249
250 mutex_unlock(&chaoskey_list_lock);
251 usb_dbg(interface, "disconnect done");
252 }
253
chaoskey_open(struct inode * inode,struct file * file)254 static int chaoskey_open(struct inode *inode, struct file *file)
255 {
256 struct chaoskey *dev;
257 struct usb_interface *interface;
258 int rv = 0;
259
260 /* get the interface from minor number and driver information */
261 interface = usb_find_interface(&chaoskey_driver, iminor(inode));
262 if (!interface)
263 return -ENODEV;
264
265 usb_dbg(interface, "open");
266
267 dev = usb_get_intfdata(interface);
268 if (!dev) {
269 usb_dbg(interface, "open (dev)");
270 return -ENODEV;
271 }
272
273 file->private_data = dev;
274 mutex_lock(&chaoskey_list_lock);
275 mutex_lock(&dev->lock);
276 if (dev->present)
277 ++dev->open;
278 else
279 rv = -ENODEV;
280 mutex_unlock(&dev->lock);
281 mutex_unlock(&chaoskey_list_lock);
282
283 return rv;
284 }
285
chaoskey_release(struct inode * inode,struct file * file)286 static int chaoskey_release(struct inode *inode, struct file *file)
287 {
288 struct chaoskey *dev = file->private_data;
289 struct usb_interface *interface;
290 int rv = 0;
291
292 if (dev == NULL)
293 return -ENODEV;
294
295 interface = dev->interface;
296
297 usb_dbg(interface, "release");
298
299 mutex_lock(&chaoskey_list_lock);
300 mutex_lock(&dev->lock);
301
302 usb_dbg(interface, "open count at release is %d", dev->open);
303
304 if (dev->open <= 0) {
305 usb_dbg(interface, "invalid open count (%d)", dev->open);
306 rv = -ENODEV;
307 goto bail;
308 }
309
310 --dev->open;
311
312 if (!dev->present) {
313 if (dev->open == 0) {
314 mutex_unlock(&dev->lock);
315 chaoskey_free(dev);
316 goto destruction;
317 }
318 }
319 bail:
320 mutex_unlock(&dev->lock);
321 destruction:
322 mutex_unlock(&chaoskey_list_lock);
323 return rv;
324 }
325
chaos_read_callback(struct urb * urb)326 static void chaos_read_callback(struct urb *urb)
327 {
328 struct chaoskey *dev = urb->context;
329 int status = urb->status;
330
331 usb_dbg(dev->interface, "callback status (%d)", status);
332
333 if (status == 0)
334 dev->valid = urb->actual_length;
335 else
336 dev->valid = 0;
337
338 dev->used = 0;
339
340 /* must be seen first before validity is announced */
341 smp_wmb();
342
343 dev->reading = false;
344 wake_up(&dev->wait_q);
345 }
346
347 /* Fill the buffer. Called with dev->lock held
348 */
_chaoskey_fill(struct chaoskey * dev)349 static int _chaoskey_fill(struct chaoskey *dev)
350 {
351 DEFINE_WAIT(wait);
352 int result;
353 bool started;
354
355 usb_dbg(dev->interface, "fill");
356
357 /* Return immediately if someone called before the buffer was
358 * empty */
359 if (dev->valid != dev->used) {
360 usb_dbg(dev->interface, "not empty yet (valid %d used %d)",
361 dev->valid, dev->used);
362 return 0;
363 }
364
365 /* Bail if the device has been removed */
366 if (!dev->present) {
367 usb_dbg(dev->interface, "device not present");
368 return -ENODEV;
369 }
370
371 /* Make sure the device is awake */
372 result = usb_autopm_get_interface(dev->interface);
373 if (result) {
374 usb_dbg(dev->interface, "wakeup failed (result %d)", result);
375 return result;
376 }
377
378 dev->reading = true;
379 result = usb_submit_urb(dev->urb, GFP_KERNEL);
380 if (result < 0) {
381 result = usb_translate_errors(result);
382 dev->reading = false;
383 goto out;
384 }
385
386 /* The first read on the Alea takes a little under 2 seconds.
387 * Reads after the first read take only a few microseconds
388 * though. Presumably the entropy-generating circuit needs
389 * time to ramp up. So, we wait longer on the first read.
390 */
391 started = dev->reads_started;
392 dev->reads_started = true;
393 result = wait_event_interruptible_timeout(
394 dev->wait_q,
395 !dev->reading,
396 (started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) );
397
398 if (result < 0) {
399 usb_kill_urb(dev->urb);
400 goto out;
401 }
402
403 if (result == 0) {
404 result = -ETIMEDOUT;
405 usb_kill_urb(dev->urb);
406 } else {
407 result = dev->valid;
408 }
409 out:
410 /* Let the device go back to sleep eventually */
411 usb_autopm_put_interface(dev->interface);
412
413 usb_dbg(dev->interface, "read %d bytes", dev->valid);
414
415 return result;
416 }
417
chaoskey_read(struct file * file,char __user * buffer,size_t count,loff_t * ppos)418 static ssize_t chaoskey_read(struct file *file,
419 char __user *buffer,
420 size_t count,
421 loff_t *ppos)
422 {
423 struct chaoskey *dev;
424 ssize_t read_count = 0;
425 int this_time;
426 int result = 0;
427 unsigned long remain;
428
429 dev = file->private_data;
430
431 if (dev == NULL || !dev->present)
432 return -ENODEV;
433
434 usb_dbg(dev->interface, "read %zu", count);
435
436 while (count > 0) {
437
438 /* Grab the rng_lock briefly to ensure that the hwrng interface
439 * gets priority over other user access
440 */
441 result = mutex_lock_interruptible(&dev->rng_lock);
442 if (result)
443 goto bail;
444 mutex_unlock(&dev->rng_lock);
445
446 if (file->f_flags & O_NONBLOCK) {
447 result = mutex_trylock(&dev->lock);
448 if (result == 0) {
449 result = -EAGAIN;
450 goto bail;
451 } else {
452 result = 0;
453 }
454 } else {
455 result = mutex_lock_interruptible(&dev->lock);
456 if (result)
457 goto bail;
458 }
459 if (dev->valid == dev->used) {
460 result = _chaoskey_fill(dev);
461 if (result < 0) {
462 mutex_unlock(&dev->lock);
463 goto bail;
464 }
465 }
466
467 this_time = dev->valid - dev->used;
468 if (this_time > count)
469 this_time = count;
470
471 remain = copy_to_user(buffer, dev->buf + dev->used, this_time);
472 if (remain) {
473 result = -EFAULT;
474
475 /* Consume the bytes that were copied so we don't leak
476 * data to user space
477 */
478 dev->used += this_time - remain;
479 mutex_unlock(&dev->lock);
480 goto bail;
481 }
482
483 count -= this_time;
484 read_count += this_time;
485 buffer += this_time;
486 dev->used += this_time;
487 mutex_unlock(&dev->lock);
488 }
489 bail:
490 if (read_count) {
491 usb_dbg(dev->interface, "read %zu bytes", read_count);
492 return read_count;
493 }
494 usb_dbg(dev->interface, "empty read, result %d", result);
495 if (result == -ETIMEDOUT)
496 result = -EAGAIN;
497 return result;
498 }
499
chaoskey_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)500 static int chaoskey_rng_read(struct hwrng *rng, void *data,
501 size_t max, bool wait)
502 {
503 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
504 int this_time;
505
506 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait);
507
508 if (!dev->present) {
509 usb_dbg(dev->interface, "device not present");
510 return 0;
511 }
512
513 /* Hold the rng_lock until we acquire the device lock so that
514 * this operation gets priority over other user access to the
515 * device
516 */
517 mutex_lock(&dev->rng_lock);
518
519 mutex_lock(&dev->lock);
520
521 mutex_unlock(&dev->rng_lock);
522
523 /* Try to fill the buffer if empty. It doesn't actually matter
524 * if _chaoskey_fill works; we'll just return zero bytes as
525 * the buffer will still be empty
526 */
527 if (dev->valid == dev->used)
528 (void) _chaoskey_fill(dev);
529
530 this_time = dev->valid - dev->used;
531 if (this_time > max)
532 this_time = max;
533
534 memcpy(data, dev->buf + dev->used, this_time);
535
536 dev->used += this_time;
537
538 mutex_unlock(&dev->lock);
539
540 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time);
541 return this_time;
542 }
543
544 #ifdef CONFIG_PM
chaoskey_suspend(struct usb_interface * interface,pm_message_t message)545 static int chaoskey_suspend(struct usb_interface *interface,
546 pm_message_t message)
547 {
548 usb_dbg(interface, "suspend");
549 return 0;
550 }
551
chaoskey_resume(struct usb_interface * interface)552 static int chaoskey_resume(struct usb_interface *interface)
553 {
554 struct chaoskey *dev;
555 struct usb_device *udev = interface_to_usbdev(interface);
556
557 usb_dbg(interface, "resume");
558 dev = usb_get_intfdata(interface);
559
560 /*
561 * We may have lost power.
562 * In that case the device that needs a long time
563 * for the first requests needs an extended timeout
564 * again
565 */
566 if (le16_to_cpu(udev->descriptor.idVendor) == ALEA_VENDOR_ID)
567 dev->reads_started = false;
568
569 return 0;
570 }
571 #else
572 #define chaoskey_suspend NULL
573 #define chaoskey_resume NULL
574 #endif
575
576 /* file operation pointers */
577 static const struct file_operations chaoskey_fops = {
578 .owner = THIS_MODULE,
579 .read = chaoskey_read,
580 .open = chaoskey_open,
581 .release = chaoskey_release,
582 .llseek = default_llseek,
583 };
584
585 /* class driver information */
586 static struct usb_class_driver chaoskey_class = {
587 .name = "chaoskey%d",
588 .fops = &chaoskey_fops,
589 .minor_base = USB_CHAOSKEY_MINOR_BASE,
590 };
591
592 /* usb specific object needed to register this driver with the usb subsystem */
593 static struct usb_driver chaoskey_driver = {
594 .name = DRIVER_SHORT,
595 .probe = chaoskey_probe,
596 .disconnect = chaoskey_disconnect,
597 .suspend = chaoskey_suspend,
598 .resume = chaoskey_resume,
599 .reset_resume = chaoskey_resume,
600 .id_table = chaoskey_table,
601 .supports_autosuspend = 1,
602 };
603
604 module_usb_driver(chaoskey_driver);
605
606