drivers/usb/misc/chaoskey.c

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