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 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 70 static const struct usb_device_id chaoskey_table[] = { 71 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) }, 72 { }, 73 }; 74 MODULE_DEVICE_TABLE(usb, chaoskey_table); 75 76 static void chaos_read_callback(struct urb *urb); 77 78 /* Driver-local specific stuff */ 79 struct chaoskey { 80 struct usb_interface *interface; 81 char in_ep; 82 struct mutex lock; 83 struct mutex rng_lock; 84 int open; /* open count */ 85 bool present; /* device not disconnected */ 86 bool reading; /* ongoing IO */ 87 int size; /* size of buf */ 88 int valid; /* bytes of buf read */ 89 int used; /* bytes of buf consumed */ 90 char *name; /* product + serial */ 91 struct hwrng hwrng; /* Embedded struct for hwrng */ 92 int hwrng_registered; /* registered with hwrng API */ 93 wait_queue_head_t wait_q; /* for timeouts */ 94 struct urb *urb; /* for performing IO */ 95 char *buf; 96 }; 97 98 static void chaoskey_free(struct chaoskey *dev) 99 { 100 if (dev) { 101 usb_dbg(dev->interface, "free"); 102 usb_free_urb(dev->urb); 103 kfree(dev->name); 104 kfree(dev->buf); 105 kfree(dev); 106 } 107 } 108 109 static int chaoskey_probe(struct usb_interface *interface, 110 const struct usb_device_id *id) 111 { 112 struct usb_device *udev = interface_to_usbdev(interface); 113 struct usb_host_interface *altsetting = interface->cur_altsetting; 114 int i; 115 int in_ep = -1; 116 struct chaoskey *dev; 117 int result = -ENOMEM; 118 int size; 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 for (i = 0; i < altsetting->desc.bNumEndpoints; i++) { 124 if (usb_endpoint_is_bulk_in(&altsetting->endpoint[i].desc)) { 125 in_ep = usb_endpoint_num(&altsetting->endpoint[i].desc); 126 size = usb_endpoint_maxp(&altsetting->endpoint[i].desc); 127 break; 128 } 129 } 130 131 /* Validate endpoint and size */ 132 if (in_ep == -1) { 133 usb_dbg(interface, "no IN endpoint found"); 134 return -ENODEV; 135 } 136 if (size <= 0) { 137 usb_dbg(interface, "invalid size (%d)", size); 138 return -ENODEV; 139 } 140 141 if (size > CHAOSKEY_BUF_LEN) { 142 usb_dbg(interface, "size reduced from %d to %d\n", 143 size, CHAOSKEY_BUF_LEN); 144 size = CHAOSKEY_BUF_LEN; 145 } 146 147 /* Looks good, allocate and initialize */ 148 149 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL); 150 151 if (dev == NULL) 152 goto out; 153 154 dev->buf = kmalloc(size, GFP_KERNEL); 155 156 if (dev->buf == NULL) 157 goto out; 158 159 dev->urb = usb_alloc_urb(0, GFP_KERNEL); 160 161 if (!dev->urb) 162 goto out; 163 164 usb_fill_bulk_urb(dev->urb, 165 udev, 166 usb_rcvbulkpipe(udev, in_ep), 167 dev->buf, 168 size, 169 chaos_read_callback, 170 dev); 171 172 /* Construct a name using the product and serial values. Each 173 * device needs a unique name for the hwrng code 174 */ 175 176 if (udev->product && udev->serial) { 177 dev->name = kmalloc(strlen(udev->product) + 1 + 178 strlen(udev->serial) + 1, GFP_KERNEL); 179 if (dev->name == NULL) 180 goto out; 181 182 strcpy(dev->name, udev->product); 183 strcat(dev->name, "-"); 184 strcat(dev->name, udev->serial); 185 } 186 187 dev->interface = interface; 188 189 dev->in_ep = in_ep; 190 191 dev->size = size; 192 dev->present = 1; 193 194 init_waitqueue_head(&dev->wait_q); 195 196 mutex_init(&dev->lock); 197 mutex_init(&dev->rng_lock); 198 199 usb_set_intfdata(interface, dev); 200 201 result = usb_register_dev(interface, &chaoskey_class); 202 if (result) { 203 usb_err(interface, "Unable to allocate minor number."); 204 goto out; 205 } 206 207 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name; 208 dev->hwrng.read = chaoskey_rng_read; 209 210 /* Set the 'quality' metric. Quality is measured in units of 211 * 1/1024's of a bit ("mills"). This should be set to 1024, 212 * but there is a bug in the hwrng core which masks it with 213 * 1023. 214 * 215 * The patch that has been merged to the crypto development 216 * tree for that bug limits the value to 1024 at most, so by 217 * setting this to 1024 + 1023, we get 1023 before the fix is 218 * merged and 1024 afterwards. We'll patch this driver once 219 * both bits of code are in the same tree. 220 */ 221 dev->hwrng.quality = 1024 + 1023; 222 223 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0); 224 if (!dev->hwrng_registered) 225 usb_err(interface, "Unable to register with hwrng"); 226 227 usb_enable_autosuspend(udev); 228 229 usb_dbg(interface, "chaoskey probe success, size %d", dev->size); 230 return 0; 231 232 out: 233 usb_set_intfdata(interface, NULL); 234 chaoskey_free(dev); 235 return result; 236 } 237 238 static void chaoskey_disconnect(struct usb_interface *interface) 239 { 240 struct chaoskey *dev; 241 242 usb_dbg(interface, "disconnect"); 243 dev = usb_get_intfdata(interface); 244 if (!dev) { 245 usb_dbg(interface, "disconnect failed - no dev"); 246 return; 247 } 248 249 if (dev->hwrng_registered) 250 hwrng_unregister(&dev->hwrng); 251 252 usb_deregister_dev(interface, &chaoskey_class); 253 254 usb_set_intfdata(interface, NULL); 255 mutex_lock(&dev->lock); 256 257 dev->present = 0; 258 usb_poison_urb(dev->urb); 259 260 if (!dev->open) { 261 mutex_unlock(&dev->lock); 262 chaoskey_free(dev); 263 } else 264 mutex_unlock(&dev->lock); 265 266 usb_dbg(interface, "disconnect done"); 267 } 268 269 static int chaoskey_open(struct inode *inode, struct file *file) 270 { 271 struct chaoskey *dev; 272 struct usb_interface *interface; 273 274 /* get the interface from minor number and driver information */ 275 interface = usb_find_interface(&chaoskey_driver, iminor(inode)); 276 if (!interface) 277 return -ENODEV; 278 279 usb_dbg(interface, "open"); 280 281 dev = usb_get_intfdata(interface); 282 if (!dev) { 283 usb_dbg(interface, "open (dev)"); 284 return -ENODEV; 285 } 286 287 file->private_data = dev; 288 mutex_lock(&dev->lock); 289 ++dev->open; 290 mutex_unlock(&dev->lock); 291 292 usb_dbg(interface, "open success"); 293 return 0; 294 } 295 296 static int chaoskey_release(struct inode *inode, struct file *file) 297 { 298 struct chaoskey *dev = file->private_data; 299 struct usb_interface *interface; 300 301 if (dev == NULL) 302 return -ENODEV; 303 304 interface = dev->interface; 305 306 usb_dbg(interface, "release"); 307 308 mutex_lock(&dev->lock); 309 310 usb_dbg(interface, "open count at release is %d", dev->open); 311 312 if (dev->open <= 0) { 313 usb_dbg(interface, "invalid open count (%d)", dev->open); 314 mutex_unlock(&dev->lock); 315 return -ENODEV; 316 } 317 318 --dev->open; 319 320 if (!dev->present) { 321 if (dev->open == 0) { 322 mutex_unlock(&dev->lock); 323 chaoskey_free(dev); 324 } else 325 mutex_unlock(&dev->lock); 326 } else 327 mutex_unlock(&dev->lock); 328 329 usb_dbg(interface, "release success"); 330 return 0; 331 } 332 333 static void chaos_read_callback(struct urb *urb) 334 { 335 struct chaoskey *dev = urb->context; 336 int status = urb->status; 337 338 usb_dbg(dev->interface, "callback status (%d)", status); 339 340 if (status == 0) 341 dev->valid = urb->actual_length; 342 else 343 dev->valid = 0; 344 345 dev->used = 0; 346 347 /* must be seen first before validity is announced */ 348 smp_wmb(); 349 350 dev->reading = false; 351 wake_up(&dev->wait_q); 352 } 353 354 /* Fill the buffer. Called with dev->lock held 355 */ 356 static int _chaoskey_fill(struct chaoskey *dev) 357 { 358 DEFINE_WAIT(wait); 359 int result; 360 361 usb_dbg(dev->interface, "fill"); 362 363 /* Return immediately if someone called before the buffer was 364 * empty */ 365 if (dev->valid != dev->used) { 366 usb_dbg(dev->interface, "not empty yet (valid %d used %d)", 367 dev->valid, dev->used); 368 return 0; 369 } 370 371 /* Bail if the device has been removed */ 372 if (!dev->present) { 373 usb_dbg(dev->interface, "device not present"); 374 return -ENODEV; 375 } 376 377 /* Make sure the device is awake */ 378 result = usb_autopm_get_interface(dev->interface); 379 if (result) { 380 usb_dbg(dev->interface, "wakeup failed (result %d)", result); 381 return result; 382 } 383 384 dev->reading = true; 385 result = usb_submit_urb(dev->urb, GFP_KERNEL); 386 if (result < 0) { 387 result = usb_translate_errors(result); 388 dev->reading = false; 389 goto out; 390 } 391 392 result = wait_event_interruptible_timeout( 393 dev->wait_q, 394 !dev->reading, 395 NAK_TIMEOUT); 396 397 if (result < 0) 398 goto out; 399 400 if (result == 0) 401 result = -ETIMEDOUT; 402 else 403 result = dev->valid; 404 out: 405 /* Let the device go back to sleep eventually */ 406 usb_autopm_put_interface(dev->interface); 407 408 usb_dbg(dev->interface, "read %d bytes", dev->valid); 409 410 return result; 411 } 412 413 static ssize_t chaoskey_read(struct file *file, 414 char __user *buffer, 415 size_t count, 416 loff_t *ppos) 417 { 418 struct chaoskey *dev; 419 ssize_t read_count = 0; 420 int this_time; 421 int result = 0; 422 unsigned long remain; 423 424 dev = file->private_data; 425 426 if (dev == NULL || !dev->present) 427 return -ENODEV; 428 429 usb_dbg(dev->interface, "read %zu", count); 430 431 while (count > 0) { 432 433 /* Grab the rng_lock briefly to ensure that the hwrng interface 434 * gets priority over other user access 435 */ 436 result = mutex_lock_interruptible(&dev->rng_lock); 437 if (result) 438 goto bail; 439 mutex_unlock(&dev->rng_lock); 440 441 result = mutex_lock_interruptible(&dev->lock); 442 if (result) 443 goto bail; 444 if (dev->valid == dev->used) { 445 result = _chaoskey_fill(dev); 446 if (result < 0) { 447 mutex_unlock(&dev->lock); 448 goto bail; 449 } 450 } 451 452 this_time = dev->valid - dev->used; 453 if (this_time > count) 454 this_time = count; 455 456 remain = copy_to_user(buffer, dev->buf + dev->used, this_time); 457 if (remain) { 458 result = -EFAULT; 459 460 /* Consume the bytes that were copied so we don't leak 461 * data to user space 462 */ 463 dev->used += this_time - remain; 464 mutex_unlock(&dev->lock); 465 goto bail; 466 } 467 468 count -= this_time; 469 read_count += this_time; 470 buffer += this_time; 471 dev->used += this_time; 472 mutex_unlock(&dev->lock); 473 } 474 bail: 475 if (read_count) { 476 usb_dbg(dev->interface, "read %zu bytes", read_count); 477 return read_count; 478 } 479 usb_dbg(dev->interface, "empty read, result %d", result); 480 if (result == -ETIMEDOUT) 481 result = -EAGAIN; 482 return result; 483 } 484 485 static int chaoskey_rng_read(struct hwrng *rng, void *data, 486 size_t max, bool wait) 487 { 488 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng); 489 int this_time; 490 491 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait); 492 493 if (!dev->present) { 494 usb_dbg(dev->interface, "device not present"); 495 return 0; 496 } 497 498 /* Hold the rng_lock until we acquire the device lock so that 499 * this operation gets priority over other user access to the 500 * device 501 */ 502 mutex_lock(&dev->rng_lock); 503 504 mutex_lock(&dev->lock); 505 506 mutex_unlock(&dev->rng_lock); 507 508 /* Try to fill the buffer if empty. It doesn't actually matter 509 * if _chaoskey_fill works; we'll just return zero bytes as 510 * the buffer will still be empty 511 */ 512 if (dev->valid == dev->used) 513 (void) _chaoskey_fill(dev); 514 515 this_time = dev->valid - dev->used; 516 if (this_time > max) 517 this_time = max; 518 519 memcpy(data, dev->buf + dev->used, this_time); 520 521 dev->used += this_time; 522 523 mutex_unlock(&dev->lock); 524 525 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time); 526 return this_time; 527 } 528 529 #ifdef CONFIG_PM 530 static int chaoskey_suspend(struct usb_interface *interface, 531 pm_message_t message) 532 { 533 usb_dbg(interface, "suspend"); 534 return 0; 535 } 536 537 static int chaoskey_resume(struct usb_interface *interface) 538 { 539 usb_dbg(interface, "resume"); 540 return 0; 541 } 542 #else 543 #define chaoskey_suspend NULL 544 #define chaoskey_resume NULL 545 #endif 546 547 /* file operation pointers */ 548 static const struct file_operations chaoskey_fops = { 549 .owner = THIS_MODULE, 550 .read = chaoskey_read, 551 .open = chaoskey_open, 552 .release = chaoskey_release, 553 .llseek = default_llseek, 554 }; 555 556 /* class driver information */ 557 static struct usb_class_driver chaoskey_class = { 558 .name = "chaoskey%d", 559 .fops = &chaoskey_fops, 560 .minor_base = USB_CHAOSKEY_MINOR_BASE, 561 }; 562 563 /* usb specific object needed to register this driver with the usb subsystem */ 564 static struct usb_driver chaoskey_driver = { 565 .name = DRIVER_SHORT, 566 .probe = chaoskey_probe, 567 .disconnect = chaoskey_disconnect, 568 .suspend = chaoskey_suspend, 569 .resume = chaoskey_resume, 570 .reset_resume = chaoskey_resume, 571 .id_table = chaoskey_table, 572 .supports_autosuspend = 1, 573 }; 574 575 module_usb_driver(chaoskey_driver); 576 577