drivers/usb/misc/chaoskey.c

   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
  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                 usb_put_intf(dev->interface);
 102                 kfree(dev);
 103         }
 104 }
 105
 106 static int chaoskey_probe(struct usb_interface *interface,
 107                           const struct usb_device_id *id)
 108 {
 109         struct usb_device *udev = interface_to_usbdev(interface);
 110         struct usb_host_interface *altsetting = interface->cur_altsetting;
 111         struct usb_endpoint_descriptor *epd;
 112         int in_ep;
 113         struct chaoskey *dev;
 114         int result = -ENOMEM;
 115         int size;
 116         int res;
 117
 118         usb_dbg(interface, "probe %s-%s", udev->product, udev->serial);
 119
 120         /* Find the first bulk IN endpoint and its packet size */
 121         res = usb_find_bulk_in_endpoint(altsetting, &epd);
 122         if (res) {
 123                 usb_dbg(interface, "no IN endpoint found");
 124                 return res;
 125         }
 126
 127         in_ep = usb_endpoint_num(epd);
 128         size = usb_endpoint_maxp(epd);
 129
 130         /* Validate endpoint and size */
 131         if (size <= 0) {
 132                 usb_dbg(interface, "invalid size (%d)", size);
 133                 return -ENODEV;
 134         }
 135
 136         if (size > CHAOSKEY_BUF_LEN) {
 137                 usb_dbg(interface, "size reduced from %d to %d\n",
 138                         size, CHAOSKEY_BUF_LEN);
 139                 size = CHAOSKEY_BUF_LEN;
 140         }
 141
 142         /* Looks good, allocate and initialize */
 143
 144         dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL);
 145
 146         if (dev == NULL)
 147                 goto out;
 148
 149         dev->interface = usb_get_intf(interface);
 150
 151         dev->buf = kmalloc(size, GFP_KERNEL);
 152
 153         if (dev->buf == NULL)
 154                 goto out;
 155
 156         dev->urb = usb_alloc_urb(0, GFP_KERNEL);
 157
 158         if (!dev->urb)
 159                 goto out;
 160
 161         usb_fill_bulk_urb(dev->urb,
 162                 udev,
 163                 usb_rcvbulkpipe(udev, in_ep),
 164                 dev->buf,
 165                 size,
 166                 chaos_read_callback,
 167                 dev);
 168
 169         /* Construct a name using the product and serial values. Each
 170          * device needs a unique name for the hwrng code
 171          */
 172
 173         if (udev->product && udev->serial) {
 174                 dev->name = kasprintf(GFP_KERNEL, "%s-%s", udev->product,
 175                                       udev->serial);
 176                 if (dev->name == NULL)
 177                         goto out;
 178         }
 179
 180         dev->in_ep = in_ep;
 181
 182         if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID)
 183                 dev->reads_started = true;
 184
 185         dev->size = size;
 186         dev->present = true;
 187
 188         init_waitqueue_head(&dev->wait_q);
 189
 190         mutex_init(&dev->lock);
 191         mutex_init(&dev->rng_lock);
 192
 193         usb_set_intfdata(interface, dev);
 194
 195         result = usb_register_dev(interface, &chaoskey_class);
 196         if (result) {
 197                 usb_err(interface, "Unable to allocate minor number.");
 198                 goto out;
 199         }
 200
 201         dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
 202         dev->hwrng.read = chaoskey_rng_read;
 203         dev->hwrng.quality = 1024;
 204
 205         dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
 206         if (!dev->hwrng_registered)
 207                 usb_err(interface, "Unable to register with hwrng");
 208
 209         usb_enable_autosuspend(udev);
 210
 211         usb_dbg(interface, "chaoskey probe success, size %d", dev->size);
 212         return 0;
 213
 214 out:
 215         usb_set_intfdata(interface, NULL);
 216         chaoskey_free(dev);
 217         return result;
 218 }
 219
 220 static void chaoskey_disconnect(struct usb_interface *interface)
 221 {
 222         struct chaoskey *dev;
 223
 224         usb_dbg(interface, "disconnect");
 225         dev = usb_get_intfdata(interface);
 226         if (!dev) {
 227                 usb_dbg(interface, "disconnect failed - no dev");
 228                 return;
 229         }
 230
 231         if (dev->hwrng_registered)
 232                 hwrng_unregister(&dev->hwrng);
 233
 234         usb_deregister_dev(interface, &chaoskey_class);
 235
 236         usb_set_intfdata(interface, NULL);
 237         mutex_lock(&dev->lock);
 238
 239         dev->present = false;
 240         usb_poison_urb(dev->urb);
 241
 242         if (!dev->open) {
 243                 mutex_unlock(&dev->lock);
 244                 chaoskey_free(dev);
 245         } else
 246                 mutex_unlock(&dev->lock);
 247
 248         usb_dbg(interface, "disconnect done");
 249 }
 250
 251 static int chaoskey_open(struct inode *inode, struct file *file)
 252 {
 253         struct chaoskey *dev;
 254         struct usb_interface *interface;
 255
 256         /* get the interface from minor number and driver information */
 257         interface = usb_find_interface(&chaoskey_driver, iminor(inode));
 258         if (!interface)
 259                 return -ENODEV;
 260
 261         usb_dbg(interface, "open");
 262
 263         dev = usb_get_intfdata(interface);
 264         if (!dev) {
 265                 usb_dbg(interface, "open (dev)");
 266                 return -ENODEV;
 267         }
 268
 269         file->private_data = dev;
 270         mutex_lock(&dev->lock);
 271         ++dev->open;
 272         mutex_unlock(&dev->lock);
 273
 274         usb_dbg(interface, "open success");
 275         return 0;
 276 }
 277
 278 static int chaoskey_release(struct inode *inode, struct file *file)
 279 {
 280         struct chaoskey *dev = file->private_data;
 281         struct usb_interface *interface;
 282
 283         if (dev == NULL)
 284                 return -ENODEV;
 285
 286         interface = dev->interface;
 287
 288         usb_dbg(interface, "release");
 289
 290         mutex_lock(&dev->lock);
 291
 292         usb_dbg(interface, "open count at release is %d", dev->open);
 293
 294         if (dev->open <= 0) {
 295                 usb_dbg(interface, "invalid open count (%d)", dev->open);
 296                 mutex_unlock(&dev->lock);
 297                 return -ENODEV;
 298         }
 299
 300         --dev->open;
 301
 302         if (!dev->present) {
 303                 if (dev->open == 0) {
 304                         mutex_unlock(&dev->lock);
 305                         chaoskey_free(dev);
 306                 } else
 307                         mutex_unlock(&dev->lock);
 308         } else
 309                 mutex_unlock(&dev->lock);
 310
 311         usb_dbg(interface, "release success");
 312         return 0;
 313 }
 314
 315 static void chaos_read_callback(struct urb *urb)
 316 {
 317         struct chaoskey *dev = urb->context;
 318         int status = urb->status;
 319
 320         usb_dbg(dev->interface, "callback status (%d)", status);
 321
 322         if (status == 0)
 323                 dev->valid = urb->actual_length;
 324         else
 325                 dev->valid = 0;
 326
 327         dev->used = 0;
 328
 329         /* must be seen first before validity is announced */
 330         smp_wmb();
 331
 332         dev->reading = false;
 333         wake_up(&dev->wait_q);
 334 }
 335
 336 /* Fill the buffer. Called with dev->lock held
 337  */
 338 static int _chaoskey_fill(struct chaoskey *dev)
 339 {
 340         DEFINE_WAIT(wait);
 341         int result;
 342         bool started;
 343
 344         usb_dbg(dev->interface, "fill");
 345
 346         /* Return immediately if someone called before the buffer was
 347          * empty */
 348         if (dev->valid != dev->used) {
 349                 usb_dbg(dev->interface, "not empty yet (valid %d used %d)",
 350                         dev->valid, dev->used);
 351                 return 0;
 352         }
 353
 354         /* Bail if the device has been removed */
 355         if (!dev->present) {
 356                 usb_dbg(dev->interface, "device not present");
 357                 return -ENODEV;
 358         }
 359
 360         /* Make sure the device is awake */
 361         result = usb_autopm_get_interface(dev->interface);
 362         if (result) {
 363                 usb_dbg(dev->interface, "wakeup failed (result %d)", result);
 364                 return result;
 365         }
 366
 367         dev->reading = true;
 368         result = usb_submit_urb(dev->urb, GFP_KERNEL);
 369         if (result < 0) {
 370                 result = usb_translate_errors(result);
 371                 dev->reading = false;
 372                 goto out;
 373         }
 374
 375         /* The first read on the Alea takes a little under 2 seconds.
 376          * Reads after the first read take only a few microseconds
 377          * though.  Presumably the entropy-generating circuit needs
 378          * time to ramp up.  So, we wait longer on the first read.
 379          */
 380         started = dev->reads_started;
 381         dev->reads_started = true;
 382         result = wait_event_interruptible_timeout(
 383                 dev->wait_q,
 384                 !dev->reading,
 385                 (started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) );
 386
 387         if (result < 0) {
 388                 usb_kill_urb(dev->urb);
 389                 goto out;
 390         }
 391
 392         if (result == 0) {
 393                 result = -ETIMEDOUT;
 394                 usb_kill_urb(dev->urb);
 395         } else {
 396                 result = dev->valid;
 397         }
 398 out:
 399         /* Let the device go back to sleep eventually */
 400         usb_autopm_put_interface(dev->interface);
 401
 402         usb_dbg(dev->interface, "read %d bytes", dev->valid);
 403
 404         return result;
 405 }
 406
 407 static ssize_t chaoskey_read(struct file *file,
 408                              char __user *buffer,
 409                              size_t count,
 410                              loff_t *ppos)
 411 {
 412         struct chaoskey *dev;
 413         ssize_t read_count = 0;
 414         int this_time;
 415         int result = 0;
 416         unsigned long remain;
 417
 418         dev = file->private_data;
 419
 420         if (dev == NULL || !dev->present)
 421                 return -ENODEV;
 422
 423         usb_dbg(dev->interface, "read %zu", count);
 424
 425         while (count > 0) {
 426
 427                 /* Grab the rng_lock briefly to ensure that the hwrng interface
 428                  * gets priority over other user access
 429                  */
 430                 result = mutex_lock_interruptible(&dev->rng_lock);
 431                 if (result)
 432                         goto bail;
 433                 mutex_unlock(&dev->rng_lock);
 434
 435                 result = mutex_lock_interruptible(&dev->lock);
 436                 if (result)
 437                         goto bail;
 438                 if (dev->valid == dev->used) {
 439                         result = _chaoskey_fill(dev);
 440                         if (result < 0) {
 441                                 mutex_unlock(&dev->lock);
 442                                 goto bail;
 443                         }
 444                 }
 445
 446                 this_time = dev->valid - dev->used;
 447                 if (this_time > count)
 448                         this_time = count;
 449
 450                 remain = copy_to_user(buffer, dev->buf + dev->used, this_time);
 451                 if (remain) {
 452                         result = -EFAULT;
 453
 454                         /* Consume the bytes that were copied so we don't leak
 455                          * data to user space
 456                          */
 457                         dev->used += this_time - remain;
 458                         mutex_unlock(&dev->lock);
 459                         goto bail;
 460                 }
 461
 462                 count -= this_time;
 463                 read_count += this_time;
 464                 buffer += this_time;
 465                 dev->used += this_time;
 466                 mutex_unlock(&dev->lock);
 467         }
 468 bail:
 469         if (read_count) {
 470                 usb_dbg(dev->interface, "read %zu bytes", read_count);
 471                 return read_count;
 472         }
 473         usb_dbg(dev->interface, "empty read, result %d", result);
 474         if (result == -ETIMEDOUT)
 475                 result = -EAGAIN;
 476         return result;
 477 }
 478
 479 static int chaoskey_rng_read(struct hwrng *rng, void *data,
 480                              size_t max, bool wait)
 481 {
 482         struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
 483         int this_time;
 484
 485         usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait);
 486
 487         if (!dev->present) {
 488                 usb_dbg(dev->interface, "device not present");
 489                 return 0;
 490         }
 491
 492         /* Hold the rng_lock until we acquire the device lock so that
 493          * this operation gets priority over other user access to the
 494          * device
 495          */
 496         mutex_lock(&dev->rng_lock);
 497
 498         mutex_lock(&dev->lock);
 499
 500         mutex_unlock(&dev->rng_lock);
 501
 502         /* Try to fill the buffer if empty. It doesn't actually matter
 503          * if _chaoskey_fill works; we'll just return zero bytes as
 504          * the buffer will still be empty
 505          */
 506         if (dev->valid == dev->used)
 507                 (void) _chaoskey_fill(dev);
 508
 509         this_time = dev->valid - dev->used;
 510         if (this_time > max)
 511                 this_time = max;
 512
 513         memcpy(data, dev->buf + dev->used, this_time);
 514
 515         dev->used += this_time;
 516
 517         mutex_unlock(&dev->lock);
 518
 519         usb_dbg(dev->interface, "rng_read this_time %d\n", this_time);
 520         return this_time;
 521 }
 522
 523 #ifdef CONFIG_PM
 524 static int chaoskey_suspend(struct usb_interface *interface,
 525                             pm_message_t message)
 526 {
 527         usb_dbg(interface, "suspend");
 528         return 0;
 529 }
 530
 531 static int chaoskey_resume(struct usb_interface *interface)
 532 {
 533         struct chaoskey *dev;
 534         struct usb_device *udev = interface_to_usbdev(interface);
 535
 536         usb_dbg(interface, "resume");
 537         dev = usb_get_intfdata(interface);
 538
 539         /*
 540          * We may have lost power.
 541          * In that case the device that needs a long time
 542          * for the first requests needs an extended timeout
 543          * again
 544          */
 545         if (le16_to_cpu(udev->descriptor.idVendor) == ALEA_VENDOR_ID)
 546                 dev->reads_started = false;
 547
 548         return 0;
 549 }
 550 #else
 551 #define chaoskey_suspend NULL
 552 #define chaoskey_resume NULL
 553 #endif
 554
 555 /* file operation pointers */
 556 static const struct file_operations chaoskey_fops = {
 557         .owner = THIS_MODULE,
 558         .read = chaoskey_read,
 559         .open = chaoskey_open,
 560         .release = chaoskey_release,
 561         .llseek = default_llseek,
 562 };
 563
 564 /* class driver information */
 565 static struct usb_class_driver chaoskey_class = {
 566         .name = "chaoskey%d",
 567         .fops = &chaoskey_fops,
 568         .minor_base = USB_CHAOSKEY_MINOR_BASE,
 569 };
 570
 571 /* usb specific object needed to register this driver with the usb subsystem */
 572 static struct usb_driver chaoskey_driver = {
 573         .name = DRIVER_SHORT,
 574         .probe = chaoskey_probe,
 575         .disconnect = chaoskey_disconnect,
 576         .suspend = chaoskey_suspend,
 577         .resume = chaoskey_resume,
 578         .reset_resume = chaoskey_resume,
 579         .id_table = chaoskey_table,
 580         .supports_autosuspend = 1,
 581 };
 582
 583 module_usb_driver(chaoskey_driver);
 584