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_AUTHOR "Keith Packard, keithp@keithp.com" 46 #define DRIVER_DESC "Altus Metrum ChaosKey driver" 47 #define DRIVER_SHORT "chaoskey" 48 49 MODULE_AUTHOR(DRIVER_AUTHOR); 50 MODULE_DESCRIPTION(DRIVER_DESC); 51 MODULE_LICENSE("GPL"); 52 53 #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */ 54 #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */ 55 56 #define ALEA_VENDOR_ID 0x12d8 /* Araneus */ 57 #define ALEA_PRODUCT_ID 0x0001 /* Alea I */ 58 59 #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */ 60 61 #define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */ 62 #define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */ 63 64 #ifdef CONFIG_USB_DYNAMIC_MINORS 65 #define USB_CHAOSKEY_MINOR_BASE 0 66 #else 67 68 /* IOWARRIOR_MINOR_BASE + 16, not official yet */ 69 #define USB_CHAOSKEY_MINOR_BASE 224 70 #endif 71 72 static const struct usb_device_id chaoskey_table[] = { 73 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) }, 74 { USB_DEVICE(ALEA_VENDOR_ID, ALEA_PRODUCT_ID) }, 75 { }, 76 }; 77 MODULE_DEVICE_TABLE(usb, chaoskey_table); 78 79 static void chaos_read_callback(struct urb *urb); 80 81 /* Driver-local specific stuff */ 82 struct chaoskey { 83 struct usb_interface *interface; 84 char in_ep; 85 struct mutex lock; 86 struct mutex rng_lock; 87 int open; /* open count */ 88 bool present; /* device not disconnected */ 89 bool reading; /* ongoing IO */ 90 bool reads_started; /* track first read for Alea */ 91 int size; /* size of buf */ 92 int valid; /* bytes of buf read */ 93 int used; /* bytes of buf consumed */ 94 char *name; /* product + serial */ 95 struct hwrng hwrng; /* Embedded struct for hwrng */ 96 int hwrng_registered; /* registered with hwrng API */ 97 wait_queue_head_t wait_q; /* for timeouts */ 98 struct urb *urb; /* for performing IO */ 99 char *buf; 100 }; 101 102 static void chaoskey_free(struct chaoskey *dev) 103 { 104 if (dev) { 105 usb_dbg(dev->interface, "free"); 106 usb_free_urb(dev->urb); 107 kfree(dev->name); 108 kfree(dev->buf); 109 kfree(dev); 110 } 111 } 112 113 static int chaoskey_probe(struct usb_interface *interface, 114 const struct usb_device_id *id) 115 { 116 struct usb_device *udev = interface_to_usbdev(interface); 117 struct usb_host_interface *altsetting = interface->cur_altsetting; 118 struct usb_endpoint_descriptor *epd; 119 int in_ep; 120 struct chaoskey *dev; 121 int result = -ENOMEM; 122 int size; 123 int res; 124 125 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial); 126 127 /* Find the first bulk IN endpoint and its packet size */ 128 res = usb_find_bulk_in_endpoint(altsetting, &epd); 129 if (res) { 130 usb_dbg(interface, "no IN endpoint found"); 131 return res; 132 } 133 134 in_ep = usb_endpoint_num(epd); 135 size = usb_endpoint_maxp(epd); 136 137 /* Validate endpoint and size */ 138 if (size <= 0) { 139 usb_dbg(interface, "invalid size (%d)", size); 140 return -ENODEV; 141 } 142 143 if (size > CHAOSKEY_BUF_LEN) { 144 usb_dbg(interface, "size reduced from %d to %d\n", 145 size, CHAOSKEY_BUF_LEN); 146 size = CHAOSKEY_BUF_LEN; 147 } 148 149 /* Looks good, allocate and initialize */ 150 151 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL); 152 153 if (dev == NULL) 154 goto out; 155 156 dev->buf = kmalloc(size, GFP_KERNEL); 157 158 if (dev->buf == NULL) 159 goto out; 160 161 dev->urb = usb_alloc_urb(0, GFP_KERNEL); 162 163 if (!dev->urb) 164 goto out; 165 166 usb_fill_bulk_urb(dev->urb, 167 udev, 168 usb_rcvbulkpipe(udev, in_ep), 169 dev->buf, 170 size, 171 chaos_read_callback, 172 dev); 173 174 /* Construct a name using the product and serial values. Each 175 * device needs a unique name for the hwrng code 176 */ 177 178 if (udev->product && udev->serial) { 179 dev->name = kmalloc(strlen(udev->product) + 1 + 180 strlen(udev->serial) + 1, GFP_KERNEL); 181 if (dev->name == NULL) 182 goto out; 183 184 strcpy(dev->name, udev->product); 185 strcat(dev->name, "-"); 186 strcat(dev->name, udev->serial); 187 } 188 189 dev->interface = interface; 190 191 dev->in_ep = in_ep; 192 193 if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID) 194 dev->reads_started = 1; 195 196 dev->size = size; 197 dev->present = 1; 198 199 init_waitqueue_head(&dev->wait_q); 200 201 mutex_init(&dev->lock); 202 mutex_init(&dev->rng_lock); 203 204 usb_set_intfdata(interface, dev); 205 206 result = usb_register_dev(interface, &chaoskey_class); 207 if (result) { 208 usb_err(interface, "Unable to allocate minor number."); 209 goto out; 210 } 211 212 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name; 213 dev->hwrng.read = chaoskey_rng_read; 214 dev->hwrng.quality = 1024; 215 216 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0); 217 if (!dev->hwrng_registered) 218 usb_err(interface, "Unable to register with hwrng"); 219 220 usb_enable_autosuspend(udev); 221 222 usb_dbg(interface, "chaoskey probe success, size %d", dev->size); 223 return 0; 224 225 out: 226 usb_set_intfdata(interface, NULL); 227 chaoskey_free(dev); 228 return result; 229 } 230 231 static void chaoskey_disconnect(struct usb_interface *interface) 232 { 233 struct chaoskey *dev; 234 235 usb_dbg(interface, "disconnect"); 236 dev = usb_get_intfdata(interface); 237 if (!dev) { 238 usb_dbg(interface, "disconnect failed - no dev"); 239 return; 240 } 241 242 if (dev->hwrng_registered) 243 hwrng_unregister(&dev->hwrng); 244 245 usb_deregister_dev(interface, &chaoskey_class); 246 247 usb_set_intfdata(interface, NULL); 248 mutex_lock(&dev->lock); 249 250 dev->present = 0; 251 usb_poison_urb(dev->urb); 252 253 if (!dev->open) { 254 mutex_unlock(&dev->lock); 255 chaoskey_free(dev); 256 } else 257 mutex_unlock(&dev->lock); 258 259 usb_dbg(interface, "disconnect done"); 260 } 261 262 static int chaoskey_open(struct inode *inode, struct file *file) 263 { 264 struct chaoskey *dev; 265 struct usb_interface *interface; 266 267 /* get the interface from minor number and driver information */ 268 interface = usb_find_interface(&chaoskey_driver, iminor(inode)); 269 if (!interface) 270 return -ENODEV; 271 272 usb_dbg(interface, "open"); 273 274 dev = usb_get_intfdata(interface); 275 if (!dev) { 276 usb_dbg(interface, "open (dev)"); 277 return -ENODEV; 278 } 279 280 file->private_data = dev; 281 mutex_lock(&dev->lock); 282 ++dev->open; 283 mutex_unlock(&dev->lock); 284 285 usb_dbg(interface, "open success"); 286 return 0; 287 } 288 289 static int chaoskey_release(struct inode *inode, struct file *file) 290 { 291 struct chaoskey *dev = file->private_data; 292 struct usb_interface *interface; 293 294 if (dev == NULL) 295 return -ENODEV; 296 297 interface = dev->interface; 298 299 usb_dbg(interface, "release"); 300 301 mutex_lock(&dev->lock); 302 303 usb_dbg(interface, "open count at release is %d", dev->open); 304 305 if (dev->open <= 0) { 306 usb_dbg(interface, "invalid open count (%d)", dev->open); 307 mutex_unlock(&dev->lock); 308 return -ENODEV; 309 } 310 311 --dev->open; 312 313 if (!dev->present) { 314 if (dev->open == 0) { 315 mutex_unlock(&dev->lock); 316 chaoskey_free(dev); 317 } else 318 mutex_unlock(&dev->lock); 319 } else 320 mutex_unlock(&dev->lock); 321 322 usb_dbg(interface, "release success"); 323 return 0; 324 } 325 326 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 */ 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 goto out; 400 401 if (result == 0) 402 result = -ETIMEDOUT; 403 else 404 result = dev->valid; 405 out: 406 /* Let the device go back to sleep eventually */ 407 usb_autopm_put_interface(dev->interface); 408 409 usb_dbg(dev->interface, "read %d bytes", dev->valid); 410 411 return result; 412 } 413 414 static ssize_t chaoskey_read(struct file *file, 415 char __user *buffer, 416 size_t count, 417 loff_t *ppos) 418 { 419 struct chaoskey *dev; 420 ssize_t read_count = 0; 421 int this_time; 422 int result = 0; 423 unsigned long remain; 424 425 dev = file->private_data; 426 427 if (dev == NULL || !dev->present) 428 return -ENODEV; 429 430 usb_dbg(dev->interface, "read %zu", count); 431 432 while (count > 0) { 433 434 /* Grab the rng_lock briefly to ensure that the hwrng interface 435 * gets priority over other user access 436 */ 437 result = mutex_lock_interruptible(&dev->rng_lock); 438 if (result) 439 goto bail; 440 mutex_unlock(&dev->rng_lock); 441 442 result = mutex_lock_interruptible(&dev->lock); 443 if (result) 444 goto bail; 445 if (dev->valid == dev->used) { 446 result = _chaoskey_fill(dev); 447 if (result < 0) { 448 mutex_unlock(&dev->lock); 449 goto bail; 450 } 451 } 452 453 this_time = dev->valid - dev->used; 454 if (this_time > count) 455 this_time = count; 456 457 remain = copy_to_user(buffer, dev->buf + dev->used, this_time); 458 if (remain) { 459 result = -EFAULT; 460 461 /* Consume the bytes that were copied so we don't leak 462 * data to user space 463 */ 464 dev->used += this_time - remain; 465 mutex_unlock(&dev->lock); 466 goto bail; 467 } 468 469 count -= this_time; 470 read_count += this_time; 471 buffer += this_time; 472 dev->used += this_time; 473 mutex_unlock(&dev->lock); 474 } 475 bail: 476 if (read_count) { 477 usb_dbg(dev->interface, "read %zu bytes", read_count); 478 return read_count; 479 } 480 usb_dbg(dev->interface, "empty read, result %d", result); 481 if (result == -ETIMEDOUT) 482 result = -EAGAIN; 483 return result; 484 } 485 486 static int chaoskey_rng_read(struct hwrng *rng, void *data, 487 size_t max, bool wait) 488 { 489 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng); 490 int this_time; 491 492 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait); 493 494 if (!dev->present) { 495 usb_dbg(dev->interface, "device not present"); 496 return 0; 497 } 498 499 /* Hold the rng_lock until we acquire the device lock so that 500 * this operation gets priority over other user access to the 501 * device 502 */ 503 mutex_lock(&dev->rng_lock); 504 505 mutex_lock(&dev->lock); 506 507 mutex_unlock(&dev->rng_lock); 508 509 /* Try to fill the buffer if empty. It doesn't actually matter 510 * if _chaoskey_fill works; we'll just return zero bytes as 511 * the buffer will still be empty 512 */ 513 if (dev->valid == dev->used) 514 (void) _chaoskey_fill(dev); 515 516 this_time = dev->valid - dev->used; 517 if (this_time > max) 518 this_time = max; 519 520 memcpy(data, dev->buf + dev->used, this_time); 521 522 dev->used += this_time; 523 524 mutex_unlock(&dev->lock); 525 526 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time); 527 return this_time; 528 } 529 530 #ifdef CONFIG_PM 531 static int chaoskey_suspend(struct usb_interface *interface, 532 pm_message_t message) 533 { 534 usb_dbg(interface, "suspend"); 535 return 0; 536 } 537 538 static int chaoskey_resume(struct usb_interface *interface) 539 { 540 usb_dbg(interface, "resume"); 541 return 0; 542 } 543 #else 544 #define chaoskey_suspend NULL 545 #define chaoskey_resume NULL 546 #endif 547 548 /* file operation pointers */ 549 static const struct file_operations chaoskey_fops = { 550 .owner = THIS_MODULE, 551 .read = chaoskey_read, 552 .open = chaoskey_open, 553 .release = chaoskey_release, 554 .llseek = default_llseek, 555 }; 556 557 /* class driver information */ 558 static struct usb_class_driver chaoskey_class = { 559 .name = "chaoskey%d", 560 .fops = &chaoskey_fops, 561 .minor_base = USB_CHAOSKEY_MINOR_BASE, 562 }; 563 564 /* usb specific object needed to register this driver with the usb subsystem */ 565 static struct usb_driver chaoskey_driver = { 566 .name = DRIVER_SHORT, 567 .probe = chaoskey_probe, 568 .disconnect = chaoskey_disconnect, 569 .suspend = chaoskey_suspend, 570 .resume = chaoskey_resume, 571 .reset_resume = chaoskey_resume, 572 .id_table = chaoskey_table, 573 .supports_autosuspend = 1, 574 }; 575 576 module_usb_driver(chaoskey_driver); 577 578