fs/ecryptfs/miscdev.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  *
   4  * Copyright (C) 2008 International Business Machines Corp.
   5  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License version
   9  * 2 as published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  19  * 02111-1307, USA.
  20  */
  21
  22 #include <linux/fs.h>
  23 #include <linux/hash.h>
  24 #include <linux/random.h>
  25 #include <linux/miscdevice.h>
  26 #include <linux/poll.h>
  27 #include <linux/slab.h>
  28 #include <linux/wait.h>
  29 #include <linux/module.h>
  30 #include "ecryptfs_kernel.h"
  31
  32 static atomic_t ecryptfs_num_miscdev_opens;
  33
  34 /**
  35  * ecryptfs_miscdev_poll
  36  * @file: dev file
  37  * @pt: dev poll table (ignored)
  38  *
  39  * Returns the poll mask
  40  */
  41 static __poll_t
  42 ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
  43 {
  44         struct ecryptfs_daemon *daemon = file->private_data;
  45         __poll_t mask = 0;
  46
  47         mutex_lock(&daemon->mux);
  48         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
  49                 printk(KERN_WARNING "%s: Attempt to poll on zombified "
  50                        "daemon\n", __func__);
  51                 goto out_unlock_daemon;
  52         }
  53         if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
  54                 goto out_unlock_daemon;
  55         if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
  56                 goto out_unlock_daemon;
  57         daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
  58         mutex_unlock(&daemon->mux);
  59         poll_wait(file, &daemon->wait, pt);
  60         mutex_lock(&daemon->mux);
  61         if (!list_empty(&daemon->msg_ctx_out_queue))
  62                 mask |= EPOLLIN | EPOLLRDNORM;
  63 out_unlock_daemon:
  64         daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
  65         mutex_unlock(&daemon->mux);
  66         return mask;
  67 }
  68
  69 /**
  70  * ecryptfs_miscdev_open
  71  * @inode: inode of miscdev handle (ignored)
  72  * @file: file for miscdev handle
  73  *
  74  * Returns zero on success; non-zero otherwise
  75  */
  76 static int
  77 ecryptfs_miscdev_open(struct inode *inode, struct file *file)
  78 {
  79         struct ecryptfs_daemon *daemon = NULL;
  80         int rc;
  81
  82         mutex_lock(&ecryptfs_daemon_hash_mux);
  83         rc = ecryptfs_find_daemon_by_euid(&daemon);
  84         if (!rc) {
  85                 rc = -EINVAL;
  86                 goto out_unlock_daemon_list;
  87         }
  88         rc = ecryptfs_spawn_daemon(&daemon, file);
  89         if (rc) {
  90                 printk(KERN_ERR "%s: Error attempting to spawn daemon; "
  91                        "rc = [%d]\n", __func__, rc);
  92                 goto out_unlock_daemon_list;
  93         }
  94         mutex_lock(&daemon->mux);
  95         if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
  96                 rc = -EBUSY;
  97                 goto out_unlock_daemon;
  98         }
  99         daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
 100         file->private_data = daemon;
 101         atomic_inc(&ecryptfs_num_miscdev_opens);
 102 out_unlock_daemon:
 103         mutex_unlock(&daemon->mux);
 104 out_unlock_daemon_list:
 105         mutex_unlock(&ecryptfs_daemon_hash_mux);
 106         return rc;
 107 }
 108
 109 /**
 110  * ecryptfs_miscdev_release
 111  * @inode: inode of fs/ecryptfs/euid handle (ignored)
 112  * @file: file for fs/ecryptfs/euid handle
 113  *
 114  * This keeps the daemon registered until the daemon sends another
 115  * ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
 116  *
 117  * Returns zero on success; non-zero otherwise
 118  */
 119 static int
 120 ecryptfs_miscdev_release(struct inode *inode, struct file *file)
 121 {
 122         struct ecryptfs_daemon *daemon = file->private_data;
 123         int rc;
 124
 125         mutex_lock(&daemon->mux);
 126         BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
 127         daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
 128         atomic_dec(&ecryptfs_num_miscdev_opens);
 129         mutex_unlock(&daemon->mux);
 130
 131         mutex_lock(&ecryptfs_daemon_hash_mux);
 132         rc = ecryptfs_exorcise_daemon(daemon);
 133         mutex_unlock(&ecryptfs_daemon_hash_mux);
 134         if (rc) {
 135                 printk(KERN_CRIT "%s: Fatal error whilst attempting to "
 136                        "shut down daemon; rc = [%d]. Please report this "
 137                        "bug.\n", __func__, rc);
 138                 BUG();
 139         }
 140         return rc;
 141 }
 142
 143 /**
 144  * ecryptfs_send_miscdev
 145  * @data: Data to send to daemon; may be NULL
 146  * @data_size: Amount of data to send to daemon
 147  * @msg_ctx: Message context, which is used to handle the reply. If
 148  *           this is NULL, then we do not expect a reply.
 149  * @msg_type: Type of message
 150  * @msg_flags: Flags for message
 151  * @daemon: eCryptfs daemon object
 152  *
 153  * Add msg_ctx to queue and then, if it exists, notify the blocked
 154  * miscdevess about the data being available. Must be called with
 155  * ecryptfs_daemon_hash_mux held.
 156  *
 157  * Returns zero on success; non-zero otherwise
 158  */
 159 int ecryptfs_send_miscdev(char *data, size_t data_size,
 160                           struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
 161                           u16 msg_flags, struct ecryptfs_daemon *daemon)
 162 {
 163         struct ecryptfs_message *msg;
 164
 165         msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
 166         if (!msg)
 167                 return -ENOMEM;
 168
 169         mutex_lock(&msg_ctx->mux);
 170         msg_ctx->msg = msg;
 171         msg_ctx->msg->index = msg_ctx->index;
 172         msg_ctx->msg->data_len = data_size;
 173         msg_ctx->type = msg_type;
 174         memcpy(msg_ctx->msg->data, data, data_size);
 175         msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
 176         list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
 177         mutex_unlock(&msg_ctx->mux);
 178
 179         mutex_lock(&daemon->mux);
 180         daemon->num_queued_msg_ctx++;
 181         wake_up_interruptible(&daemon->wait);
 182         mutex_unlock(&daemon->mux);
 183
 184         return 0;
 185 }
 186
 187 /*
 188  * miscdevfs packet format:
 189  *  Octet 0: Type
 190  *  Octets 1-4: network byte order msg_ctx->counter
 191  *  Octets 5-N0: Size of struct ecryptfs_message to follow
 192  *  Octets N0-N1: struct ecryptfs_message (including data)
 193  *
 194  *  Octets 5-N1 not written if the packet type does not include a message
 195  */
 196 #define PKT_TYPE_SIZE           1
 197 #define PKT_CTR_SIZE            4
 198 #define MIN_NON_MSG_PKT_SIZE    (PKT_TYPE_SIZE + PKT_CTR_SIZE)
 199 #define MIN_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
 200                                  + ECRYPTFS_MIN_PKT_LEN_SIZE)
 201 /* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
 202 #define MAX_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
 203                                  + ECRYPTFS_MAX_PKT_LEN_SIZE \
 204                                  + sizeof(struct ecryptfs_message) \
 205                                  + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
 206 #define PKT_TYPE_OFFSET         0
 207 #define PKT_CTR_OFFSET          PKT_TYPE_SIZE
 208 #define PKT_LEN_OFFSET          (PKT_TYPE_SIZE + PKT_CTR_SIZE)
 209
 210 /**
 211  * ecryptfs_miscdev_read - format and send message from queue
 212  * @file: miscdevfs handle
 213  * @buf: User buffer into which to copy the next message on the daemon queue
 214  * @count: Amount of space available in @buf
 215  * @ppos: Offset in file (ignored)
 216  *
 217  * Pulls the most recent message from the daemon queue, formats it for
 218  * being sent via a miscdevfs handle, and copies it into @buf
 219  *
 220  * Returns the number of bytes copied into the user buffer
 221  */
 222 static ssize_t
 223 ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
 224                       loff_t *ppos)
 225 {
 226         struct ecryptfs_daemon *daemon = file->private_data;
 227         struct ecryptfs_msg_ctx *msg_ctx;
 228         size_t packet_length_size;
 229         char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
 230         size_t i;
 231         size_t total_length;
 232         int rc;
 233
 234         mutex_lock(&daemon->mux);
 235         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
 236                 rc = 0;
 237                 printk(KERN_WARNING "%s: Attempt to read from zombified "
 238                        "daemon\n", __func__);
 239                 goto out_unlock_daemon;
 240         }
 241         if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
 242                 rc = 0;
 243                 goto out_unlock_daemon;
 244         }
 245         /* This daemon will not go away so long as this flag is set */
 246         daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
 247 check_list:
 248         if (list_empty(&daemon->msg_ctx_out_queue)) {
 249                 mutex_unlock(&daemon->mux);
 250                 rc = wait_event_interruptible(
 251                         daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
 252                 mutex_lock(&daemon->mux);
 253                 if (rc < 0) {
 254                         rc = 0;
 255                         goto out_unlock_daemon;
 256                 }
 257         }
 258         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
 259                 rc = 0;
 260                 goto out_unlock_daemon;
 261         }
 262         if (list_empty(&daemon->msg_ctx_out_queue)) {
 263                 /* Something else jumped in since the
 264                  * wait_event_interruptable() and removed the
 265                  * message from the queue; try again */
 266                 goto check_list;
 267         }
 268         msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
 269                                    struct ecryptfs_msg_ctx, daemon_out_list);
 270         BUG_ON(!msg_ctx);
 271         mutex_lock(&msg_ctx->mux);
 272         if (msg_ctx->msg) {
 273                 rc = ecryptfs_write_packet_length(packet_length,
 274                                                   msg_ctx->msg_size,
 275                                                   &packet_length_size);
 276                 if (rc) {
 277                         rc = 0;
 278                         printk(KERN_WARNING "%s: Error writing packet length; "
 279                                "rc = [%d]\n", __func__, rc);
 280                         goto out_unlock_msg_ctx;
 281                 }
 282         } else {
 283                 packet_length_size = 0;
 284                 msg_ctx->msg_size = 0;
 285         }
 286         total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_length_size
 287                         + msg_ctx->msg_size);
 288         if (count < total_length) {
 289                 rc = 0;
 290                 printk(KERN_WARNING "%s: Only given user buffer of "
 291                        "size [%zd], but we need [%zd] to read the "
 292                        "pending message\n", __func__, count, total_length);
 293                 goto out_unlock_msg_ctx;
 294         }
 295         rc = -EFAULT;
 296         if (put_user(msg_ctx->type, buf))
 297                 goto out_unlock_msg_ctx;
 298         if (put_user(cpu_to_be32(msg_ctx->counter),
 299                      (__be32 __user *)(&buf[PKT_CTR_OFFSET])))
 300                 goto out_unlock_msg_ctx;
 301         i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
 302         if (msg_ctx->msg) {
 303                 if (copy_to_user(&buf[i], packet_length, packet_length_size))
 304                         goto out_unlock_msg_ctx;
 305                 i += packet_length_size;
 306                 if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
 307                         goto out_unlock_msg_ctx;
 308                 i += msg_ctx->msg_size;
 309         }
 310         rc = i;
 311         list_del(&msg_ctx->daemon_out_list);
 312         kfree(msg_ctx->msg);
 313         msg_ctx->msg = NULL;
 314         /* We do not expect a reply from the userspace daemon for any
 315          * message type other than ECRYPTFS_MSG_REQUEST */
 316         if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
 317                 ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 318 out_unlock_msg_ctx:
 319         mutex_unlock(&msg_ctx->mux);
 320 out_unlock_daemon:
 321         daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
 322         mutex_unlock(&daemon->mux);
 323         return rc;
 324 }
 325
 326 /**
 327  * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
 328  * @data: Bytes comprising struct ecryptfs_message
 329  * @data_size: sizeof(struct ecryptfs_message) + data len
 330  * @seq: Sequence number for miscdev response packet
 331  *
 332  * Returns zero on success; non-zero otherwise
 333  */
 334 static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
 335                                      size_t data_size, u32 seq)
 336 {
 337         struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
 338         int rc;
 339
 340         if ((sizeof(*msg) + msg->data_len) != data_size) {
 341                 printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
 342                        "[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
 343                        (sizeof(*msg) + msg->data_len), data_size);
 344                 rc = -EINVAL;
 345                 goto out;
 346         }
 347         rc = ecryptfs_process_response(daemon, msg, seq);
 348         if (rc)
 349                 printk(KERN_ERR
 350                        "Error processing response message; rc = [%d]\n", rc);
 351 out:
 352         return rc;
 353 }
 354
 355 /**
 356  * ecryptfs_miscdev_write - handle write to daemon miscdev handle
 357  * @file: File for misc dev handle
 358  * @buf: Buffer containing user data
 359  * @count: Amount of data in @buf
 360  * @ppos: Pointer to offset in file (ignored)
 361  *
 362  * Returns the number of bytes read from @buf
 363  */
 364 static ssize_t
 365 ecryptfs_miscdev_write(struct file *file, const char __user *buf,
 366                        size_t count, loff_t *ppos)
 367 {
 368         __be32 counter_nbo;
 369         u32 seq;
 370         size_t packet_size, packet_size_length;
 371         char *data;
 372         unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
 373         ssize_t rc;
 374
 375         if (count == 0) {
 376                 return 0;
 377         } else if (count == MIN_NON_MSG_PKT_SIZE) {
 378                 /* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
 379                 goto memdup;
 380         } else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
 381                 printk(KERN_WARNING "%s: Acceptable packet size range is "
 382                        "[%d-%zu], but amount of data written is [%zu].\n",
 383                        __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
 384                 return -EINVAL;
 385         }
 386
 387         if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
 388                            sizeof(packet_size_peek))) {
 389                 printk(KERN_WARNING "%s: Error while inspecting packet size\n",
 390                        __func__);
 391                 return -EFAULT;
 392         }
 393
 394         rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
 395                                           &packet_size_length);
 396         if (rc) {
 397                 printk(KERN_WARNING "%s: Error parsing packet length; "
 398                        "rc = [%zd]\n", __func__, rc);
 399                 return rc;
 400         }
 401
 402         if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size)
 403             != count) {
 404                 printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
 405                        packet_size);
 406                 return -EINVAL;
 407         }
 408
 409 memdup:
 410         data = memdup_user(buf, count);
 411         if (IS_ERR(data)) {
 412                 printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
 413                        __func__, PTR_ERR(data));
 414                 return PTR_ERR(data);
 415         }
 416         switch (data[PKT_TYPE_OFFSET]) {
 417         case ECRYPTFS_MSG_RESPONSE:
 418                 if (count < (MIN_MSG_PKT_SIZE
 419                              + sizeof(struct ecryptfs_message))) {
 420                         printk(KERN_WARNING "%s: Minimum acceptable packet "
 421                                "size is [%zd], but amount of data written is "
 422                                "only [%zd]. Discarding response packet.\n",
 423                                __func__,
 424                                (MIN_MSG_PKT_SIZE
 425                                 + sizeof(struct ecryptfs_message)), count);
 426                         rc = -EINVAL;
 427                         goto out_free;
 428                 }
 429                 memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
 430                 seq = be32_to_cpu(counter_nbo);
 431                 rc = ecryptfs_miscdev_response(file->private_data,
 432                                 &data[PKT_LEN_OFFSET + packet_size_length],
 433                                 packet_size, seq);
 434                 if (rc) {
 435                         printk(KERN_WARNING "%s: Failed to deliver miscdev "
 436                                "response to requesting operation; rc = [%zd]\n",
 437                                __func__, rc);
 438                         goto out_free;
 439                 }
 440                 break;
 441         case ECRYPTFS_MSG_HELO:
 442         case ECRYPTFS_MSG_QUIT:
 443                 break;
 444         default:
 445                 ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
 446                                 "message of unrecognized type [%d]\n",
 447                                 data[0]);
 448                 rc = -EINVAL;
 449                 goto out_free;
 450         }
 451         rc = count;
 452 out_free:
 453         kfree(data);
 454         return rc;
 455 }
 456
 457
 458 static const struct file_operations ecryptfs_miscdev_fops = {
 459         .owner   = THIS_MODULE,
 460         .open    = ecryptfs_miscdev_open,
 461         .poll    = ecryptfs_miscdev_poll,
 462         .read    = ecryptfs_miscdev_read,
 463         .write   = ecryptfs_miscdev_write,
 464         .release = ecryptfs_miscdev_release,
 465         .llseek  = noop_llseek,
 466 };
 467
 468 static struct miscdevice ecryptfs_miscdev = {
 469         .minor = MISC_DYNAMIC_MINOR,
 470         .name  = "ecryptfs",
 471         .fops  = &ecryptfs_miscdev_fops
 472 };
 473
 474 /**
 475  * ecryptfs_init_ecryptfs_miscdev
 476  *
 477  * Messages sent to the userspace daemon from the kernel are placed on
 478  * a queue associated with the daemon. The next read against the
 479  * miscdev handle by that daemon will return the oldest message placed
 480  * on the message queue for the daemon.
 481  *
 482  * Returns zero on success; non-zero otherwise
 483  */
 484 int __init ecryptfs_init_ecryptfs_miscdev(void)
 485 {
 486         int rc;
 487
 488         atomic_set(&ecryptfs_num_miscdev_opens, 0);
 489         rc = misc_register(&ecryptfs_miscdev);
 490         if (rc)
 491                 printk(KERN_ERR "%s: Failed to register miscellaneous device "
 492                        "for communications with userspace daemons; rc = [%d]\n",
 493                        __func__, rc);
 494         return rc;
 495 }
 496
 497 /**
 498  * ecryptfs_destroy_ecryptfs_miscdev
 499  *
 500  * All of the daemons must be exorcised prior to calling this
 501  * function.
 502  */
 503 void ecryptfs_destroy_ecryptfs_miscdev(void)
 504 {
 505         BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
 506         misc_deregister(&ecryptfs_miscdev);
 507 }