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 #define usb_dbg(usb_if, format, arg...) \
31 dev_dbg(&(usb_if)->dev, format, ## arg)
32
33 #define usb_err(usb_if, format, arg...) \
34 dev_err(&(usb_if)->dev, format, ## arg)
35
36 /* Version Information */
37 #define DRIVER_AUTHOR "Keith Packard, keithp@keithp.com"
38 #define DRIVER_DESC "Altus Metrum ChaosKey driver"
39 #define DRIVER_SHORT "chaoskey"
40
41 MODULE_AUTHOR(DRIVER_AUTHOR);
42 MODULE_DESCRIPTION(DRIVER_DESC);
43 MODULE_LICENSE("GPL");
44
45 #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */
46 #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */
47
48 #define ALEA_VENDOR_ID 0x12d8 /* Araneus */
49 #define ALEA_PRODUCT_ID 0x0001 /* Alea I */
50
51 #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */
52
53 #define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */
54 #define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */
55
56 #ifdef CONFIG_USB_DYNAMIC_MINORS
57 #define USB_CHAOSKEY_MINOR_BASE 0
58 #else
59
60 /* IOWARRIOR_MINOR_BASE + 16, not official yet */
61 #define USB_CHAOSKEY_MINOR_BASE 224
62 #endif
63
64 static const struct usb_device_id chaoskey_table[] = {
65 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) },
66 { USB_DEVICE(ALEA_VENDOR_ID, ALEA_PRODUCT_ID) },
67 { },
68 };
69 MODULE_DEVICE_TABLE(usb, chaoskey_table);
70
71 static void chaos_read_callback(struct urb *urb);
72
73 /* Driver-local specific stuff */
74 struct chaoskey {
75 struct usb_interface *interface;
76 char in_ep;
77 struct mutex lock;
78 struct mutex rng_lock;
79 int open; /* open count */
80 bool present; /* device not disconnected */
81 bool reading; /* ongoing IO */
82 bool reads_started; /* track first read for Alea */
83 int size; /* size of buf */
84 int valid; /* bytes of buf read */
85 int used; /* bytes of buf consumed */
86 char *name; /* product + serial */
87 struct hwrng hwrng; /* Embedded struct for hwrng */
88 int hwrng_registered; /* registered with hwrng API */
89 wait_queue_head_t wait_q; /* for timeouts */
90 struct urb *urb; /* for performing IO */
91 char *buf;
92 };
93
chaoskey_free(struct chaoskey * dev)94 static void chaoskey_free(struct chaoskey *dev)
95 {
96 if (dev) {
97 usb_dbg(dev->interface, "free");
98 usb_free_urb(dev->urb);
99 kfree(dev->name);
100 kfree(dev->buf);
101 kfree(dev);
102 }
103 }
104
chaoskey_probe(struct usb_interface * interface,const struct usb_device_id * id)105 static int chaoskey_probe(struct usb_interface *interface,
106 const struct usb_device_id *id)
107 {
108 struct usb_device *udev = interface_to_usbdev(interface);
109 struct usb_host_interface *altsetting = interface->cur_altsetting;
110 struct usb_endpoint_descriptor *epd;
111 int in_ep;
112 struct chaoskey *dev;
113 int result = -ENOMEM;
114 int size;
115 int res;
116
117 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial);
118
119 /* Find the first bulk IN endpoint and its packet size */
120 res = usb_find_bulk_in_endpoint(altsetting, &epd);
121 if (res) {
122 usb_dbg(interface, "no IN endpoint found");
123 return res;
124 }
125
126 in_ep = usb_endpoint_num(epd);
127 size = usb_endpoint_maxp(epd);
128
129 /* Validate endpoint and size */
130 if (size <= 0) {
131 usb_dbg(interface, "invalid size (%d)", size);
132 return -ENODEV;
133 }
134
135 if (size > CHAOSKEY_BUF_LEN) {
136 usb_dbg(interface, "size reduced from %d to %d\n",
137 size, CHAOSKEY_BUF_LEN);
138 size = CHAOSKEY_BUF_LEN;
139 }
140
141 /* Looks good, allocate and initialize */
142
143 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL);
144
145 if (dev == NULL)
146 goto out;
147
148 dev->buf = kmalloc(size, GFP_KERNEL);
149
150 if (dev->buf == NULL)
151 goto out;
152
153 dev->urb = usb_alloc_urb(0, GFP_KERNEL);
154
155 if (!dev->urb)
156 goto out;
157
158 usb_fill_bulk_urb(dev->urb,
159 udev,
160 usb_rcvbulkpipe(udev, in_ep),
161 dev->buf,
162 size,
163 chaos_read_callback,
164 dev);
165
166 /* Construct a name using the product and serial values. Each
167 * device needs a unique name for the hwrng code
168 */
169
170 if (udev->product && udev->serial) {
171 dev->name = kasprintf(GFP_KERNEL, "%s-%s", udev->product,
172 udev->serial);
173 if (dev->name == NULL)
174 goto out;
175 }
176
177 dev->interface = interface;
178
179 dev->in_ep = in_ep;
180
181 if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID)
182 dev->reads_started = true;
183
184 dev->size = size;
185 dev->present = true;
186
187 init_waitqueue_head(&dev->wait_q);
188
189 mutex_init(&dev->lock);
190 mutex_init(&dev->rng_lock);
191
192 usb_set_intfdata(interface, dev);
193
194 result = usb_register_dev(interface, &chaoskey_class);
195 if (result) {
196 usb_err(interface, "Unable to allocate minor number.");
197 goto out;
198 }
199
200 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
201 dev->hwrng.read = chaoskey_rng_read;
202 dev->hwrng.quality = 1024;
203
204 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
205 if (!dev->hwrng_registered)
206 usb_err(interface, "Unable to register with hwrng");
207
208 usb_enable_autosuspend(udev);
209
210 usb_dbg(interface, "chaoskey probe success, size %d", dev->size);
211 return 0;
212
213 out:
214 usb_set_intfdata(interface, NULL);
215 chaoskey_free(dev);
216 return result;
217 }
218
chaoskey_disconnect(struct usb_interface * interface)219 static void chaoskey_disconnect(struct usb_interface *interface)
220 {
221 struct chaoskey *dev;
222
223 usb_dbg(interface, "disconnect");
224 dev = usb_get_intfdata(interface);
225 if (!dev) {
226 usb_dbg(interface, "disconnect failed - no dev");
227 return;
228 }
229
230 if (dev->hwrng_registered)
231 hwrng_unregister(&dev->hwrng);
232
233 usb_deregister_dev(interface, &chaoskey_class);
234
235 usb_set_intfdata(interface, NULL);
236 mutex_lock(&dev->lock);
237
238 dev->present = false;
239 usb_poison_urb(dev->urb);
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
chaoskey_open(struct inode * inode,struct file * file)250 static 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
chaoskey_release(struct inode * inode,struct file * file)277 static 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
chaos_read_callback(struct urb * urb)314 static void chaos_read_callback(struct urb *urb)
315 {
316 struct chaoskey *dev = urb->context;
317 int status = urb->status;
318
319 usb_dbg(dev->interface, "callback status (%d)", status);
320
321 if (status == 0)
322 dev->valid = urb->actual_length;
323 else
324 dev->valid = 0;
325
326 dev->used = 0;
327
328 /* must be seen first before validity is announced */
329 smp_wmb();
330
331 dev->reading = false;
332 wake_up(&dev->wait_q);
333 }
334
335 /* Fill the buffer. Called with dev->lock held
336 */
_chaoskey_fill(struct chaoskey * dev)337 static int _chaoskey_fill(struct chaoskey *dev)
338 {
339 DEFINE_WAIT(wait);
340 int result;
341 bool started;
342
343 usb_dbg(dev->interface, "fill");
344
345 /* Return immediately if someone called before the buffer was
346 * empty */
347 if (dev->valid != dev->used) {
348 usb_dbg(dev->interface, "not empty yet (valid %d used %d)",
349 dev->valid, dev->used);
350 return 0;
351 }
352
353 /* Bail if the device has been removed */
354 if (!dev->present) {
355 usb_dbg(dev->interface, "device not present");
356 return -ENODEV;
357 }
358
359 /* Make sure the device is awake */
360 result = usb_autopm_get_interface(dev->interface);
361 if (result) {
362 usb_dbg(dev->interface, "wakeup failed (result %d)", result);
363 return result;
364 }
365
366 dev->reading = true;
367 result = usb_submit_urb(dev->urb, GFP_KERNEL);
368 if (result < 0) {
369 result = usb_translate_errors(result);
370 dev->reading = false;
371 goto out;
372 }
373
374 /* The first read on the Alea takes a little under 2 seconds.
375 * Reads after the first read take only a few microseconds
376 * though. Presumably the entropy-generating circuit needs
377 * time to ramp up. So, we wait longer on the first read.
378 */
379 started = dev->reads_started;
380 dev->reads_started = true;
381 result = wait_event_interruptible_timeout(
382 dev->wait_q,
383 !dev->reading,
384 (started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) );
385
386 if (result < 0)
387 goto out;
388
389 if (result == 0)
390 result = -ETIMEDOUT;
391 else
392 result = dev->valid;
393 out:
394 /* Let the device go back to sleep eventually */
395 usb_autopm_put_interface(dev->interface);
396
397 usb_dbg(dev->interface, "read %d bytes", dev->valid);
398
399 return result;
400 }
401
chaoskey_read(struct file * file,char __user * buffer,size_t count,loff_t * ppos)402 static ssize_t chaoskey_read(struct file *file,
403 char __user *buffer,
404 size_t count,
405 loff_t *ppos)
406 {
407 struct chaoskey *dev;
408 ssize_t read_count = 0;
409 int this_time;
410 int result = 0;
411 unsigned long remain;
412
413 dev = file->private_data;
414
415 if (dev == NULL || !dev->present)
416 return -ENODEV;
417
418 usb_dbg(dev->interface, "read %zu", count);
419
420 while (count > 0) {
421
422 /* Grab the rng_lock briefly to ensure that the hwrng interface
423 * gets priority over other user access
424 */
425 result = mutex_lock_interruptible(&dev->rng_lock);
426 if (result)
427 goto bail;
428 mutex_unlock(&dev->rng_lock);
429
430 result = mutex_lock_interruptible(&dev->lock);
431 if (result)
432 goto bail;
433 if (dev->valid == dev->used) {
434 result = _chaoskey_fill(dev);
435 if (result < 0) {
436 mutex_unlock(&dev->lock);
437 goto bail;
438 }
439 }
440
441 this_time = dev->valid - dev->used;
442 if (this_time > count)
443 this_time = count;
444
445 remain = copy_to_user(buffer, dev->buf + dev->used, this_time);
446 if (remain) {
447 result = -EFAULT;
448
449 /* Consume the bytes that were copied so we don't leak
450 * data to user space
451 */
452 dev->used += this_time - remain;
453 mutex_unlock(&dev->lock);
454 goto bail;
455 }
456
457 count -= this_time;
458 read_count += this_time;
459 buffer += this_time;
460 dev->used += this_time;
461 mutex_unlock(&dev->lock);
462 }
463 bail:
464 if (read_count) {
465 usb_dbg(dev->interface, "read %zu bytes", read_count);
466 return read_count;
467 }
468 usb_dbg(dev->interface, "empty read, result %d", result);
469 if (result == -ETIMEDOUT)
470 result = -EAGAIN;
471 return result;
472 }
473
chaoskey_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)474 static int chaoskey_rng_read(struct hwrng *rng, void *data,
475 size_t max, bool wait)
476 {
477 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
478 int this_time;
479
480 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait);
481
482 if (!dev->present) {
483 usb_dbg(dev->interface, "device not present");
484 return 0;
485 }
486
487 /* Hold the rng_lock until we acquire the device lock so that
488 * this operation gets priority over other user access to the
489 * device
490 */
491 mutex_lock(&dev->rng_lock);
492
493 mutex_lock(&dev->lock);
494
495 mutex_unlock(&dev->rng_lock);
496
497 /* Try to fill the buffer if empty. It doesn't actually matter
498 * if _chaoskey_fill works; we'll just return zero bytes as
499 * the buffer will still be empty
500 */
501 if (dev->valid == dev->used)
502 (void) _chaoskey_fill(dev);
503
504 this_time = dev->valid - dev->used;
505 if (this_time > max)
506 this_time = max;
507
508 memcpy(data, dev->buf + dev->used, this_time);
509
510 dev->used += this_time;
511
512 mutex_unlock(&dev->lock);
513
514 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time);
515 return this_time;
516 }
517
518 #ifdef CONFIG_PM
chaoskey_suspend(struct usb_interface * interface,pm_message_t message)519 static int chaoskey_suspend(struct usb_interface *interface,
520 pm_message_t message)
521 {
522 usb_dbg(interface, "suspend");
523 return 0;
524 }
525
chaoskey_resume(struct usb_interface * interface)526 static int chaoskey_resume(struct usb_interface *interface)
527 {
528 usb_dbg(interface, "resume");
529 return 0;
530 }
531 #else
532 #define chaoskey_suspend NULL
533 #define chaoskey_resume NULL
534 #endif
535
536 /* file operation pointers */
537 static const struct file_operations chaoskey_fops = {
538 .owner = THIS_MODULE,
539 .read = chaoskey_read,
540 .open = chaoskey_open,
541 .release = chaoskey_release,
542 .llseek = default_llseek,
543 };
544
545 /* class driver information */
546 static struct usb_class_driver chaoskey_class = {
547 .name = "chaoskey%d",
548 .fops = &chaoskey_fops,
549 .minor_base = USB_CHAOSKEY_MINOR_BASE,
550 };
551
552 /* usb specific object needed to register this driver with the usb subsystem */
553 static struct usb_driver chaoskey_driver = {
554 .name = DRIVER_SHORT,
555 .probe = chaoskey_probe,
556 .disconnect = chaoskey_disconnect,
557 .suspend = chaoskey_suspend,
558 .resume = chaoskey_resume,
559 .reset_resume = chaoskey_resume,
560 .id_table = chaoskey_table,
561 .supports_autosuspend = 1,
562 };
563
564 module_usb_driver(chaoskey_driver);
565
566
