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 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); 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 50 MODULE_VERSION(DRIVER_VERSION); 51 MODULE_AUTHOR(DRIVER_AUTHOR); 52 MODULE_DESCRIPTION(DRIVER_DESC); 53 MODULE_LICENSE("GPL"); 54 55 #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */ 56 #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */ 57 58 #define ALEA_VENDOR_ID 0x12d8 /* Araneus */ 59 #define ALEA_PRODUCT_ID 0x0001 /* Alea I */ 60 61 #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */ 62 63 #define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */ 64 #define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */ 65 66 #ifdef CONFIG_USB_DYNAMIC_MINORS 67 #define USB_CHAOSKEY_MINOR_BASE 0 68 #else 69 70 /* IOWARRIOR_MINOR_BASE + 16, not official yet */ 71 #define USB_CHAOSKEY_MINOR_BASE 224 72 #endif 73 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) }, 77 { }, 78 }; 79 MODULE_DEVICE_TABLE(usb, chaoskey_table); 80 81 static void chaos_read_callback(struct urb *urb); 82 83 /* Driver-local specific stuff */ 84 struct chaoskey { 85 struct usb_interface *interface; 86 char in_ep; 87 struct mutex lock; 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 */ 101 char *buf; 102 }; 103 104 static void chaoskey_free(struct chaoskey *dev) 105 { 106 if (dev) { 107 usb_dbg(dev->interface, "free"); 108 usb_free_urb(dev->urb); 109 kfree(dev->name); 110 kfree(dev->buf); 111 kfree(dev); 112 } 113 } 114 115 static int chaoskey_probe(struct usb_interface *interface, 116 const struct usb_device_id *id) 117 { 118 struct usb_device *udev = interface_to_usbdev(interface); 119 struct usb_host_interface *altsetting = interface->cur_altsetting; 120 int i; 121 int in_ep = -1; 122 struct chaoskey *dev; 123 int result = -ENOMEM; 124 int size; 125 126 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial); 127 128 /* 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); 133 break; 134 } 135 } 136 137 /* Validate endpoint and size */ 138 if (in_ep == -1) { 139 usb_dbg(interface, "no IN endpoint found"); 140 return -ENODEV; 141 } 142 if (size <= 0) { 143 usb_dbg(interface, "invalid size (%d)", size); 144 return -ENODEV; 145 } 146 147 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; 151 } 152 153 /* Looks good, allocate and initialize */ 154 155 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL); 156 157 if (dev == NULL) 158 goto out; 159 160 dev->buf = kmalloc(size, GFP_KERNEL); 161 162 if (dev->buf == NULL) 163 goto out; 164 165 dev->urb = usb_alloc_urb(0, GFP_KERNEL); 166 167 if (!dev->urb) 168 goto out; 169 170 usb_fill_bulk_urb(dev->urb, 171 udev, 172 usb_rcvbulkpipe(udev, in_ep), 173 dev->buf, 174 size, 175 chaos_read_callback, 176 dev); 177 178 /* Construct a name using the product and serial values. Each 179 * device needs a unique name for the hwrng code 180 */ 181 182 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) 186 goto out; 187 188 strcpy(dev->name, udev->product); 189 strcat(dev->name, "-"); 190 strcat(dev->name, udev->serial); 191 } 192 193 dev->interface = interface; 194 195 dev->in_ep = in_ep; 196 197 if (udev->descriptor.idVendor != ALEA_VENDOR_ID) 198 dev->reads_started = 1; 199 200 dev->size = size; 201 dev->present = 1; 202 203 init_waitqueue_head(&dev->wait_q); 204 205 mutex_init(&dev->lock); 206 mutex_init(&dev->rng_lock); 207 208 usb_set_intfdata(interface, dev); 209 210 result = usb_register_dev(interface, &chaoskey_class); 211 if (result) { 212 usb_err(interface, "Unable to allocate minor number."); 213 goto out; 214 } 215 216 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name; 217 dev->hwrng.read = chaoskey_rng_read; 218 219 /* 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 222 * 1023. 223 * 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. 229 */ 230 dev->hwrng.quality = 1024 + 1023; 231 232 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0); 233 if (!dev->hwrng_registered) 234 usb_err(interface, "Unable to register with hwrng"); 235 236 usb_enable_autosuspend(udev); 237 238 usb_dbg(interface, "chaoskey probe success, size %d", dev->size); 239 return 0; 240 241 out: 242 usb_set_intfdata(interface, NULL); 243 chaoskey_free(dev); 244 return result; 245 } 246 247 static void chaoskey_disconnect(struct usb_interface *interface) 248 { 249 struct chaoskey *dev; 250 251 usb_dbg(interface, "disconnect"); 252 dev = usb_get_intfdata(interface); 253 if (!dev) { 254 usb_dbg(interface, "disconnect failed - no dev"); 255 return; 256 } 257 258 if (dev->hwrng_registered) 259 hwrng_unregister(&dev->hwrng); 260 261 usb_deregister_dev(interface, &chaoskey_class); 262 263 usb_set_intfdata(interface, NULL); 264 mutex_lock(&dev->lock); 265 266 dev->present = 0; 267 usb_poison_urb(dev->urb); 268 269 if (!dev->open) { 270 mutex_unlock(&dev->lock); 271 chaoskey_free(dev); 272 } else 273 mutex_unlock(&dev->lock); 274 275 usb_dbg(interface, "disconnect done"); 276 } 277 278 static int chaoskey_open(struct inode *inode, struct file *file) 279 { 280 struct chaoskey *dev; 281 struct usb_interface *interface; 282 283 /* get the interface from minor number and driver information */ 284 interface = usb_find_interface(&chaoskey_driver, iminor(inode)); 285 if (!interface) 286 return -ENODEV; 287 288 usb_dbg(interface, "open"); 289 290 dev = usb_get_intfdata(interface); 291 if (!dev) { 292 usb_dbg(interface, "open (dev)"); 293 return -ENODEV; 294 } 295 296 file->private_data = dev; 297 mutex_lock(&dev->lock); 298 ++dev->open; 299 mutex_unlock(&dev->lock); 300 301 usb_dbg(interface, "open success"); 302 return 0; 303 } 304 305 static int chaoskey_release(struct inode *inode, struct file *file) 306 { 307 struct chaoskey *dev = file->private_data; 308 struct usb_interface *interface; 309 310 if (dev == NULL) 311 return -ENODEV; 312 313 interface = dev->interface; 314 315 usb_dbg(interface, "release"); 316 317 mutex_lock(&dev->lock); 318 319 usb_dbg(interface, "open count at release is %d", dev->open); 320 321 if (dev->open <= 0) { 322 usb_dbg(interface, "invalid open count (%d)", dev->open); 323 mutex_unlock(&dev->lock); 324 return -ENODEV; 325 } 326 327 --dev->open; 328 329 if (!dev->present) { 330 if (dev->open == 0) { 331 mutex_unlock(&dev->lock); 332 chaoskey_free(dev); 333 } else 334 mutex_unlock(&dev->lock); 335 } else 336 mutex_unlock(&dev->lock); 337 338 usb_dbg(interface, "release success"); 339 return 0; 340 } 341 342 static void chaos_read_callback(struct urb *urb) 343 { 344 struct chaoskey *dev = urb->context; 345 int status = urb->status; 346 347 usb_dbg(dev->interface, "callback status (%d)", status); 348 349 if (status == 0) 350 dev->valid = urb->actual_length; 351 else 352 dev->valid = 0; 353 354 dev->used = 0; 355 356 /* must be seen first before validity is announced */ 357 smp_wmb(); 358 359 dev->reading = false; 360 wake_up(&dev->wait_q); 361 } 362 363 /* Fill the buffer. Called with dev->lock held 364 */ 365 static int _chaoskey_fill(struct chaoskey *dev) 366 { 367 DEFINE_WAIT(wait); 368 int result; 369 bool started; 370 371 usb_dbg(dev->interface, "fill"); 372 373 /* Return immediately if someone called before the buffer was 374 * empty */ 375 if (dev->valid != dev->used) { 376 usb_dbg(dev->interface, "not empty yet (valid %d used %d)", 377 dev->valid, dev->used); 378 return 0; 379 } 380 381 /* Bail if the device has been removed */ 382 if (!dev->present) { 383 usb_dbg(dev->interface, "device not present"); 384 return -ENODEV; 385 } 386 387 /* Make sure the device is awake */ 388 result = usb_autopm_get_interface(dev->interface); 389 if (result) { 390 usb_dbg(dev->interface, "wakeup failed (result %d)", result); 391 return result; 392 } 393 394 dev->reading = true; 395 result = usb_submit_urb(dev->urb, GFP_KERNEL); 396 if (result < 0) { 397 result = usb_translate_errors(result); 398 dev->reading = false; 399 goto out; 400 } 401 402 /* 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. 406 */ 407 started = dev->reads_started; 408 dev->reads_started = true; 409 result = wait_event_interruptible_timeout( 410 dev->wait_q, 411 !dev->reading, 412 (started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) ); 413 414 if (result < 0) 415 goto out; 416 417 if (result == 0) 418 result = -ETIMEDOUT; 419 else 420 result = dev->valid; 421 out: 422 /* Let the device go back to sleep eventually */ 423 usb_autopm_put_interface(dev->interface); 424 425 usb_dbg(dev->interface, "read %d bytes", dev->valid); 426 427 return result; 428 } 429 430 static ssize_t chaoskey_read(struct file *file, 431 char __user *buffer, 432 size_t count, 433 loff_t *ppos) 434 { 435 struct chaoskey *dev; 436 ssize_t read_count = 0; 437 int this_time; 438 int result = 0; 439 unsigned long remain; 440 441 dev = file->private_data; 442 443 if (dev == NULL || !dev->present) 444 return -ENODEV; 445 446 usb_dbg(dev->interface, "read %zu", count); 447 448 while (count > 0) { 449 450 /* Grab the rng_lock briefly to ensure that the hwrng interface 451 * gets priority over other user access 452 */ 453 result = mutex_lock_interruptible(&dev->rng_lock); 454 if (result) 455 goto bail; 456 mutex_unlock(&dev->rng_lock); 457 458 result = mutex_lock_interruptible(&dev->lock); 459 if (result) 460 goto bail; 461 if (dev->valid == dev->used) { 462 result = _chaoskey_fill(dev); 463 if (result < 0) { 464 mutex_unlock(&dev->lock); 465 goto bail; 466 } 467 } 468 469 this_time = dev->valid - dev->used; 470 if (this_time > count) 471 this_time = count; 472 473 remain = copy_to_user(buffer, dev->buf + dev->used, this_time); 474 if (remain) { 475 result = -EFAULT; 476 477 /* Consume the bytes that were copied so we don't leak 478 * data to user space 479 */ 480 dev->used += this_time - remain; 481 mutex_unlock(&dev->lock); 482 goto bail; 483 } 484 485 count -= this_time; 486 read_count += this_time; 487 buffer += this_time; 488 dev->used += this_time; 489 mutex_unlock(&dev->lock); 490 } 491 bail: 492 if (read_count) { 493 usb_dbg(dev->interface, "read %zu bytes", read_count); 494 return read_count; 495 } 496 usb_dbg(dev->interface, "empty read, result %d", result); 497 if (result == -ETIMEDOUT) 498 result = -EAGAIN; 499 return result; 500 } 501 502 static int chaoskey_rng_read(struct hwrng *rng, void *data, 503 size_t max, bool wait) 504 { 505 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng); 506 int this_time; 507 508 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait); 509 510 if (!dev->present) { 511 usb_dbg(dev->interface, "device not present"); 512 return 0; 513 } 514 515 /* Hold the rng_lock until we acquire the device lock so that 516 * this operation gets priority over other user access to the 517 * device 518 */ 519 mutex_lock(&dev->rng_lock); 520 521 mutex_lock(&dev->lock); 522 523 mutex_unlock(&dev->rng_lock); 524 525 /* 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 528 */ 529 if (dev->valid == dev->used) 530 (void) _chaoskey_fill(dev); 531 532 this_time = dev->valid - dev->used; 533 if (this_time > max) 534 this_time = max; 535 536 memcpy(data, dev->buf + dev->used, this_time); 537 538 dev->used += this_time; 539 540 mutex_unlock(&dev->lock); 541 542 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time); 543 return this_time; 544 } 545 546 #ifdef CONFIG_PM 547 static int chaoskey_suspend(struct usb_interface *interface, 548 pm_message_t message) 549 { 550 usb_dbg(interface, "suspend"); 551 return 0; 552 } 553 554 static int chaoskey_resume(struct usb_interface *interface) 555 { 556 usb_dbg(interface, "resume"); 557 return 0; 558 } 559 #else 560 #define chaoskey_suspend NULL 561 #define chaoskey_resume NULL 562 #endif 563 564 /* 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, 571 }; 572 573 /* 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, 578 }; 579 580 /* 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, 590 }; 591 592 module_usb_driver(chaoskey_driver); 593 594