2 * chaoskey - driver for ChaosKey device from Altus Metrum.
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
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
13 * Copyright © 2015 Keith Packard <keithp@keithp.com>
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.
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.
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>
33 static struct usb_driver chaoskey_driver;
34 static struct usb_class_driver chaoskey_class;
35 static int chaoskey_rng_read(struct hwrng *rng, void *data,
36 size_t max, bool wait);
38 #define usb_dbg(usb_if, format, arg...) \
39 dev_dbg(&(usb_if)->dev, format, ## arg)
41 #define usb_err(usb_if, format, arg...) \
42 dev_err(&(usb_if)->dev, format, ## arg)
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"
50 MODULE_VERSION(DRIVER_VERSION);
51 MODULE_AUTHOR(DRIVER_AUTHOR);
52 MODULE_DESCRIPTION(DRIVER_DESC);
53 MODULE_LICENSE("GPL");
55 #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */
56 #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */
58 #define ALEA_VENDOR_ID 0x12d8 /* Araneus */
59 #define ALEA_PRODUCT_ID 0x0001 /* Alea I */
61 #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */
63 #define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */
64 #define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */
66 #ifdef CONFIG_USB_DYNAMIC_MINORS
67 #define USB_CHAOSKEY_MINOR_BASE 0
70 /* IOWARRIOR_MINOR_BASE + 16, not official yet */
71 #define USB_CHAOSKEY_MINOR_BASE 224
74 static const struct usb_device_id chaoskey_table[] = {
75 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) },
76 { USB_DEVICE(ALEA_VENDOR_ID, ALEA_PRODUCT_ID) },
79 MODULE_DEVICE_TABLE(usb, chaoskey_table);
81 static void chaos_read_callback(struct urb *urb);
83 /* Driver-local specific stuff */
85 struct usb_interface *interface;
88 struct mutex rng_lock;
89 int open; /* open count */
90 bool present; /* device not disconnected */
91 bool reading; /* ongoing IO */
92 bool reads_started; /* track first read for Alea */
93 int size; /* size of buf */
94 int valid; /* bytes of buf read */
95 int used; /* bytes of buf consumed */
96 char *name; /* product + serial */
97 struct hwrng hwrng; /* Embedded struct for hwrng */
98 int hwrng_registered; /* registered with hwrng API */
99 wait_queue_head_t wait_q; /* for timeouts */
100 struct urb *urb; /* for performing IO */
104 static void chaoskey_free(struct chaoskey *dev)
107 usb_dbg(dev->interface, "free");
108 usb_free_urb(dev->urb);
115 static int chaoskey_probe(struct usb_interface *interface,
116 const struct usb_device_id *id)
118 struct usb_device *udev = interface_to_usbdev(interface);
119 struct usb_host_interface *altsetting = interface->cur_altsetting;
122 struct chaoskey *dev;
123 int result = -ENOMEM;
126 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial);
128 /* Find the first bulk IN endpoint and its packet size */
129 for (i = 0; i < altsetting->desc.bNumEndpoints; i++) {
130 if (usb_endpoint_is_bulk_in(&altsetting->endpoint[i].desc)) {
131 in_ep = usb_endpoint_num(&altsetting->endpoint[i].desc);
132 size = usb_endpoint_maxp(&altsetting->endpoint[i].desc);
137 /* Validate endpoint and size */
139 usb_dbg(interface, "no IN endpoint found");
143 usb_dbg(interface, "invalid size (%d)", size);
147 if (size > CHAOSKEY_BUF_LEN) {
148 usb_dbg(interface, "size reduced from %d to %d\n",
149 size, CHAOSKEY_BUF_LEN);
150 size = CHAOSKEY_BUF_LEN;
153 /* Looks good, allocate and initialize */
155 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL);
160 dev->buf = kmalloc(size, GFP_KERNEL);
162 if (dev->buf == NULL)
165 dev->urb = usb_alloc_urb(0, GFP_KERNEL);
170 usb_fill_bulk_urb(dev->urb,
172 usb_rcvbulkpipe(udev, in_ep),
178 /* Construct a name using the product and serial values. Each
179 * device needs a unique name for the hwrng code
182 if (udev->product && udev->serial) {
183 dev->name = kmalloc(strlen(udev->product) + 1 +
184 strlen(udev->serial) + 1, GFP_KERNEL);
185 if (dev->name == NULL)
188 strcpy(dev->name, udev->product);
189 strcat(dev->name, "-");
190 strcat(dev->name, udev->serial);
193 dev->interface = interface;
197 if (udev->descriptor.idVendor != ALEA_VENDOR_ID)
198 dev->reads_started = 1;
203 init_waitqueue_head(&dev->wait_q);
205 mutex_init(&dev->lock);
206 mutex_init(&dev->rng_lock);
208 usb_set_intfdata(interface, dev);
210 result = usb_register_dev(interface, &chaoskey_class);
212 usb_err(interface, "Unable to allocate minor number.");
216 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
217 dev->hwrng.read = chaoskey_rng_read;
219 /* Set the 'quality' metric. Quality is measured in units of
220 * 1/1024's of a bit ("mills"). This should be set to 1024,
221 * but there is a bug in the hwrng core which masks it with
224 * The patch that has been merged to the crypto development
225 * tree for that bug limits the value to 1024 at most, so by
226 * setting this to 1024 + 1023, we get 1023 before the fix is
227 * merged and 1024 afterwards. We'll patch this driver once
228 * both bits of code are in the same tree.
230 dev->hwrng.quality = 1024 + 1023;
232 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
233 if (!dev->hwrng_registered)
234 usb_err(interface, "Unable to register with hwrng");
236 usb_enable_autosuspend(udev);
238 usb_dbg(interface, "chaoskey probe success, size %d", dev->size);
242 usb_set_intfdata(interface, NULL);
247 static void chaoskey_disconnect(struct usb_interface *interface)
249 struct chaoskey *dev;
251 usb_dbg(interface, "disconnect");
252 dev = usb_get_intfdata(interface);
254 usb_dbg(interface, "disconnect failed - no dev");
258 if (dev->hwrng_registered)
259 hwrng_unregister(&dev->hwrng);
261 usb_deregister_dev(interface, &chaoskey_class);
263 usb_set_intfdata(interface, NULL);
264 mutex_lock(&dev->lock);
267 usb_poison_urb(dev->urb);
270 mutex_unlock(&dev->lock);
273 mutex_unlock(&dev->lock);
275 usb_dbg(interface, "disconnect done");
278 static int chaoskey_open(struct inode *inode, struct file *file)
280 struct chaoskey *dev;
281 struct usb_interface *interface;
283 /* get the interface from minor number and driver information */
284 interface = usb_find_interface(&chaoskey_driver, iminor(inode));
288 usb_dbg(interface, "open");
290 dev = usb_get_intfdata(interface);
292 usb_dbg(interface, "open (dev)");
296 file->private_data = dev;
297 mutex_lock(&dev->lock);
299 mutex_unlock(&dev->lock);
301 usb_dbg(interface, "open success");
305 static int chaoskey_release(struct inode *inode, struct file *file)
307 struct chaoskey *dev = file->private_data;
308 struct usb_interface *interface;
313 interface = dev->interface;
315 usb_dbg(interface, "release");
317 mutex_lock(&dev->lock);
319 usb_dbg(interface, "open count at release is %d", dev->open);
321 if (dev->open <= 0) {
322 usb_dbg(interface, "invalid open count (%d)", dev->open);
323 mutex_unlock(&dev->lock);
330 if (dev->open == 0) {
331 mutex_unlock(&dev->lock);
334 mutex_unlock(&dev->lock);
336 mutex_unlock(&dev->lock);
338 usb_dbg(interface, "release success");
342 static void chaos_read_callback(struct urb *urb)
344 struct chaoskey *dev = urb->context;
345 int status = urb->status;
347 usb_dbg(dev->interface, "callback status (%d)", status);
350 dev->valid = urb->actual_length;
356 /* must be seen first before validity is announced */
359 dev->reading = false;
360 wake_up(&dev->wait_q);
363 /* Fill the buffer. Called with dev->lock held
365 static int _chaoskey_fill(struct chaoskey *dev)
371 usb_dbg(dev->interface, "fill");
373 /* Return immediately if someone called before the buffer was
375 if (dev->valid != dev->used) {
376 usb_dbg(dev->interface, "not empty yet (valid %d used %d)",
377 dev->valid, dev->used);
381 /* Bail if the device has been removed */
383 usb_dbg(dev->interface, "device not present");
387 /* Make sure the device is awake */
388 result = usb_autopm_get_interface(dev->interface);
390 usb_dbg(dev->interface, "wakeup failed (result %d)", result);
395 result = usb_submit_urb(dev->urb, GFP_KERNEL);
397 result = usb_translate_errors(result);
398 dev->reading = false;
402 /* The first read on the Alea takes a little under 2 seconds.
403 * Reads after the first read take only a few microseconds
404 * though. Presumably the entropy-generating circuit needs
405 * time to ramp up. So, we wait longer on the first read.
407 started = dev->reads_started;
408 dev->reads_started = true;
409 result = wait_event_interruptible_timeout(
412 (started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) );
422 /* Let the device go back to sleep eventually */
423 usb_autopm_put_interface(dev->interface);
425 usb_dbg(dev->interface, "read %d bytes", dev->valid);
430 static ssize_t chaoskey_read(struct file *file,
435 struct chaoskey *dev;
436 ssize_t read_count = 0;
439 unsigned long remain;
441 dev = file->private_data;
443 if (dev == NULL || !dev->present)
446 usb_dbg(dev->interface, "read %zu", count);
450 /* Grab the rng_lock briefly to ensure that the hwrng interface
451 * gets priority over other user access
453 result = mutex_lock_interruptible(&dev->rng_lock);
456 mutex_unlock(&dev->rng_lock);
458 result = mutex_lock_interruptible(&dev->lock);
461 if (dev->valid == dev->used) {
462 result = _chaoskey_fill(dev);
464 mutex_unlock(&dev->lock);
469 this_time = dev->valid - dev->used;
470 if (this_time > count)
473 remain = copy_to_user(buffer, dev->buf + dev->used, this_time);
477 /* Consume the bytes that were copied so we don't leak
480 dev->used += this_time - remain;
481 mutex_unlock(&dev->lock);
486 read_count += this_time;
488 dev->used += this_time;
489 mutex_unlock(&dev->lock);
493 usb_dbg(dev->interface, "read %zu bytes", read_count);
496 usb_dbg(dev->interface, "empty read, result %d", result);
497 if (result == -ETIMEDOUT)
502 static int chaoskey_rng_read(struct hwrng *rng, void *data,
503 size_t max, bool wait)
505 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
508 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait);
511 usb_dbg(dev->interface, "device not present");
515 /* Hold the rng_lock until we acquire the device lock so that
516 * this operation gets priority over other user access to the
519 mutex_lock(&dev->rng_lock);
521 mutex_lock(&dev->lock);
523 mutex_unlock(&dev->rng_lock);
525 /* Try to fill the buffer if empty. It doesn't actually matter
526 * if _chaoskey_fill works; we'll just return zero bytes as
527 * the buffer will still be empty
529 if (dev->valid == dev->used)
530 (void) _chaoskey_fill(dev);
532 this_time = dev->valid - dev->used;
536 memcpy(data, dev->buf + dev->used, this_time);
538 dev->used += this_time;
540 mutex_unlock(&dev->lock);
542 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time);
547 static int chaoskey_suspend(struct usb_interface *interface,
548 pm_message_t message)
550 usb_dbg(interface, "suspend");
554 static int chaoskey_resume(struct usb_interface *interface)
556 usb_dbg(interface, "resume");
560 #define chaoskey_suspend NULL
561 #define chaoskey_resume NULL
564 /* file operation pointers */
565 static const struct file_operations chaoskey_fops = {
566 .owner = THIS_MODULE,
567 .read = chaoskey_read,
568 .open = chaoskey_open,
569 .release = chaoskey_release,
570 .llseek = default_llseek,
573 /* class driver information */
574 static struct usb_class_driver chaoskey_class = {
575 .name = "chaoskey%d",
576 .fops = &chaoskey_fops,
577 .minor_base = USB_CHAOSKEY_MINOR_BASE,
580 /* usb specific object needed to register this driver with the usb subsystem */
581 static struct usb_driver chaoskey_driver = {
582 .name = DRIVER_SHORT,
583 .probe = chaoskey_probe,
584 .disconnect = chaoskey_disconnect,
585 .suspend = chaoskey_suspend,
586 .resume = chaoskey_resume,
587 .reset_resume = chaoskey_resume,
588 .id_table = chaoskey_table,
589 .supports_autosuspend = 1,
592 module_usb_driver(chaoskey_driver);