1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * eCryptfs: Linux filesystem encryption layer
4 *
5 * Copyright (C) 2008 International Business Machines Corp.
6 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
7 */
8
9#include <linux/fs.h>
10#include <linux/hash.h>
11#include <linux/random.h>
12#include <linux/miscdevice.h>
13#include <linux/poll.h>
14#include <linux/slab.h>
15#include <linux/wait.h>
16#include <linux/module.h>
17#include "ecryptfs_kernel.h"
18
19static atomic_t ecryptfs_num_miscdev_opens;
20
21/**
22 * ecryptfs_miscdev_poll
23 * @file: dev file
24 * @pt: dev poll table (ignored)
25 *
26 * Returns the poll mask
27 */
28static __poll_t
29ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
30{
31	struct ecryptfs_daemon *daemon = file->private_data;
32	__poll_t mask = 0;
33
34	mutex_lock(&daemon->mux);
35	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
36		printk(KERN_WARNING "%s: Attempt to poll on zombified "
37		       "daemon\n", __func__);
38		goto out_unlock_daemon;
39	}
40	if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
41		goto out_unlock_daemon;
42	if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
43		goto out_unlock_daemon;
44	daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
45	mutex_unlock(&daemon->mux);
46	poll_wait(file, &daemon->wait, pt);
47	mutex_lock(&daemon->mux);
48	if (!list_empty(&daemon->msg_ctx_out_queue))
49		mask |= EPOLLIN | EPOLLRDNORM;
50out_unlock_daemon:
51	daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
52	mutex_unlock(&daemon->mux);
53	return mask;
54}
55
56/**
57 * ecryptfs_miscdev_open
58 * @inode: inode of miscdev handle (ignored)
59 * @file: file for miscdev handle
60 *
61 * Returns zero on success; non-zero otherwise
62 */
63static int
64ecryptfs_miscdev_open(struct inode *inode, struct file *file)
65{
66	struct ecryptfs_daemon *daemon = NULL;
67	int rc;
68
69	mutex_lock(&ecryptfs_daemon_hash_mux);
70	rc = ecryptfs_find_daemon_by_euid(&daemon);
71	if (!rc) {
72		rc = -EINVAL;
73		goto out_unlock_daemon_list;
74	}
75	rc = ecryptfs_spawn_daemon(&daemon, file);
76	if (rc) {
77		printk(KERN_ERR "%s: Error attempting to spawn daemon; "
78		       "rc = [%d]\n", __func__, rc);
79		goto out_unlock_daemon_list;
80	}
81	mutex_lock(&daemon->mux);
82	if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
83		rc = -EBUSY;
84		goto out_unlock_daemon;
85	}
86	daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
87	file->private_data = daemon;
88	atomic_inc(&ecryptfs_num_miscdev_opens);
89out_unlock_daemon:
90	mutex_unlock(&daemon->mux);
91out_unlock_daemon_list:
92	mutex_unlock(&ecryptfs_daemon_hash_mux);
93	return rc;
94}
95
96/**
97 * ecryptfs_miscdev_release
98 * @inode: inode of fs/ecryptfs/euid handle (ignored)
99 * @file: file for fs/ecryptfs/euid handle
100 *
101 * This keeps the daemon registered until the daemon sends another
102 * ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
103 *
104 * Returns zero on success; non-zero otherwise
105 */
106static int
107ecryptfs_miscdev_release(struct inode *inode, struct file *file)
108{
109	struct ecryptfs_daemon *daemon = file->private_data;
110	int rc;
111
112	mutex_lock(&daemon->mux);
113	BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
114	daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
115	atomic_dec(&ecryptfs_num_miscdev_opens);
116	mutex_unlock(&daemon->mux);
117
118	mutex_lock(&ecryptfs_daemon_hash_mux);
119	rc = ecryptfs_exorcise_daemon(daemon);
120	mutex_unlock(&ecryptfs_daemon_hash_mux);
121	if (rc) {
122		printk(KERN_CRIT "%s: Fatal error whilst attempting to "
123		       "shut down daemon; rc = [%d]. Please report this "
124		       "bug.\n", __func__, rc);
125		BUG();
126	}
127	return rc;
128}
129
130/**
131 * ecryptfs_send_miscdev
132 * @data: Data to send to daemon; may be NULL
133 * @data_size: Amount of data to send to daemon
134 * @msg_ctx: Message context, which is used to handle the reply. If
135 *           this is NULL, then we do not expect a reply.
136 * @msg_type: Type of message
137 * @msg_flags: Flags for message
138 * @daemon: eCryptfs daemon object
139 *
140 * Add msg_ctx to queue and then, if it exists, notify the blocked
141 * miscdevess about the data being available. Must be called with
142 * ecryptfs_daemon_hash_mux held.
143 *
144 * Returns zero on success; non-zero otherwise
145 */
146int ecryptfs_send_miscdev(char *data, size_t data_size,
147			  struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
148			  u16 msg_flags, struct ecryptfs_daemon *daemon)
149{
150	struct ecryptfs_message *msg;
151
152	msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
153	if (!msg)
154		return -ENOMEM;
155
156	mutex_lock(&msg_ctx->mux);
157	msg_ctx->msg = msg;
158	msg_ctx->msg->index = msg_ctx->index;
159	msg_ctx->msg->data_len = data_size;
160	msg_ctx->type = msg_type;
161	memcpy(msg_ctx->msg->data, data, data_size);
162	msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
163	list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
164	mutex_unlock(&msg_ctx->mux);
165
166	mutex_lock(&daemon->mux);
167	daemon->num_queued_msg_ctx++;
168	wake_up_interruptible(&daemon->wait);
169	mutex_unlock(&daemon->mux);
170
171	return 0;
172}
173
174/*
175 * miscdevfs packet format:
176 *  Octet 0: Type
177 *  Octets 1-4: network byte order msg_ctx->counter
178 *  Octets 5-N0: Size of struct ecryptfs_message to follow
179 *  Octets N0-N1: struct ecryptfs_message (including data)
180 *
181 *  Octets 5-N1 not written if the packet type does not include a message
182 */
183#define PKT_TYPE_SIZE		1
184#define PKT_CTR_SIZE		4
185#define MIN_NON_MSG_PKT_SIZE	(PKT_TYPE_SIZE + PKT_CTR_SIZE)
186#define MIN_MSG_PKT_SIZE	(PKT_TYPE_SIZE + PKT_CTR_SIZE \
187				 + ECRYPTFS_MIN_PKT_LEN_SIZE)
188/* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
189#define MAX_MSG_PKT_SIZE	(PKT_TYPE_SIZE + PKT_CTR_SIZE \
190				 + ECRYPTFS_MAX_PKT_LEN_SIZE \
191				 + sizeof(struct ecryptfs_message) \
192				 + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
193#define PKT_TYPE_OFFSET		0
194#define PKT_CTR_OFFSET		PKT_TYPE_SIZE
195#define PKT_LEN_OFFSET		(PKT_TYPE_SIZE + PKT_CTR_SIZE)
196
197/**
198 * ecryptfs_miscdev_read - format and send message from queue
199 * @file: miscdevfs handle
200 * @buf: User buffer into which to copy the next message on the daemon queue
201 * @count: Amount of space available in @buf
202 * @ppos: Offset in file (ignored)
203 *
204 * Pulls the most recent message from the daemon queue, formats it for
205 * being sent via a miscdevfs handle, and copies it into @buf
206 *
207 * Returns the number of bytes copied into the user buffer
208 */
209static ssize_t
210ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
211		      loff_t *ppos)
212{
213	struct ecryptfs_daemon *daemon = file->private_data;
214	struct ecryptfs_msg_ctx *msg_ctx;
215	size_t packet_length_size;
216	char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
217	size_t i;
218	size_t total_length;
219	int rc;
220
221	mutex_lock(&daemon->mux);
222	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
223		rc = 0;
224		printk(KERN_WARNING "%s: Attempt to read from zombified "
225		       "daemon\n", __func__);
226		goto out_unlock_daemon;
227	}
228	if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
229		rc = 0;
230		goto out_unlock_daemon;
231	}
232	/* This daemon will not go away so long as this flag is set */
233	daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
234check_list:
235	if (list_empty(&daemon->msg_ctx_out_queue)) {
236		mutex_unlock(&daemon->mux);
237		rc = wait_event_interruptible(
238			daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
239		mutex_lock(&daemon->mux);
240		if (rc < 0) {
241			rc = 0;
242			goto out_unlock_daemon;
243		}
244	}
245	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
246		rc = 0;
247		goto out_unlock_daemon;
248	}
249	if (list_empty(&daemon->msg_ctx_out_queue)) {
250		/* Something else jumped in since the
251		 * wait_event_interruptable() and removed the
252		 * message from the queue; try again */
253		goto check_list;
254	}
255	msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
256				   struct ecryptfs_msg_ctx, daemon_out_list);
257	BUG_ON(!msg_ctx);
258	mutex_lock(&msg_ctx->mux);
259	if (msg_ctx->msg) {
260		rc = ecryptfs_write_packet_length(packet_length,
261						  msg_ctx->msg_size,
262						  &packet_length_size);
263		if (rc) {
264			rc = 0;
265			printk(KERN_WARNING "%s: Error writing packet length; "
266			       "rc = [%d]\n", __func__, rc);
267			goto out_unlock_msg_ctx;
268		}
269	} else {
270		packet_length_size = 0;
271		msg_ctx->msg_size = 0;
272	}
273	total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_length_size
274			+ msg_ctx->msg_size);
275	if (count < total_length) {
276		rc = 0;
277		printk(KERN_WARNING "%s: Only given user buffer of "
278		       "size [%zd], but we need [%zd] to read the "
279		       "pending message\n", __func__, count, total_length);
280		goto out_unlock_msg_ctx;
281	}
282	rc = -EFAULT;
283	if (put_user(msg_ctx->type, buf))
284		goto out_unlock_msg_ctx;
285	if (put_user(cpu_to_be32(msg_ctx->counter),
286		     (__be32 __user *)(&buf[PKT_CTR_OFFSET])))
287		goto out_unlock_msg_ctx;
288	i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
289	if (msg_ctx->msg) {
290		if (copy_to_user(&buf[i], packet_length, packet_length_size))
291			goto out_unlock_msg_ctx;
292		i += packet_length_size;
293		if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
294			goto out_unlock_msg_ctx;
295		i += msg_ctx->msg_size;
296	}
297	rc = i;
298	list_del(&msg_ctx->daemon_out_list);
299	kfree(msg_ctx->msg);
300	msg_ctx->msg = NULL;
301	/* We do not expect a reply from the userspace daemon for any
302	 * message type other than ECRYPTFS_MSG_REQUEST */
303	if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
304		ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
305out_unlock_msg_ctx:
306	mutex_unlock(&msg_ctx->mux);
307out_unlock_daemon:
308	daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
309	mutex_unlock(&daemon->mux);
310	return rc;
311}
312
313/**
314 * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
315 * @daemon: eCryptfs daemon object
316 * @data: Bytes comprising struct ecryptfs_message
317 * @data_size: sizeof(struct ecryptfs_message) + data len
318 * @seq: Sequence number for miscdev response packet
319 *
320 * Returns zero on success; non-zero otherwise
321 */
322static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
323				     size_t data_size, u32 seq)
324{
325	struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
326	int rc;
327
328	if ((sizeof(*msg) + msg->data_len) != data_size) {
329		printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
330		       "[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
331		       (sizeof(*msg) + msg->data_len), data_size);
332		rc = -EINVAL;
333		goto out;
334	}
335	rc = ecryptfs_process_response(daemon, msg, seq);
336	if (rc)
337		printk(KERN_ERR
338		       "Error processing response message; rc = [%d]\n", rc);
339out:
340	return rc;
341}
342
343/**
344 * ecryptfs_miscdev_write - handle write to daemon miscdev handle
345 * @file: File for misc dev handle
346 * @buf: Buffer containing user data
347 * @count: Amount of data in @buf
348 * @ppos: Pointer to offset in file (ignored)
349 *
350 * Returns the number of bytes read from @buf
351 */
352static ssize_t
353ecryptfs_miscdev_write(struct file *file, const char __user *buf,
354		       size_t count, loff_t *ppos)
355{
356	__be32 counter_nbo;
357	u32 seq;
358	size_t packet_size, packet_size_length;
359	char *data;
360	unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
361	ssize_t rc;
362
363	if (count == 0) {
364		return 0;
365	} else if (count == MIN_NON_MSG_PKT_SIZE) {
366		/* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
367		goto memdup;
368	} else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
369		printk(KERN_WARNING "%s: Acceptable packet size range is "
370		       "[%d-%zu], but amount of data written is [%zu].\n",
371		       __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
372		return -EINVAL;
373	}
374
375	if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
376			   sizeof(packet_size_peek))) {
377		printk(KERN_WARNING "%s: Error while inspecting packet size\n",
378		       __func__);
379		return -EFAULT;
380	}
381
382	rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
383					  &packet_size_length);
384	if (rc) {
385		printk(KERN_WARNING "%s: Error parsing packet length; "
386		       "rc = [%zd]\n", __func__, rc);
387		return rc;
388	}
389
390	if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size)
391	    != count) {
392		printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
393		       packet_size);
394		return -EINVAL;
395	}
396
397memdup:
398	data = memdup_user(buf, count);
399	if (IS_ERR(data)) {
400		printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
401		       __func__, PTR_ERR(data));
402		return PTR_ERR(data);
403	}
404	switch (data[PKT_TYPE_OFFSET]) {
405	case ECRYPTFS_MSG_RESPONSE:
406		if (count < (MIN_MSG_PKT_SIZE
407			     + sizeof(struct ecryptfs_message))) {
408			printk(KERN_WARNING "%s: Minimum acceptable packet "
409			       "size is [%zd], but amount of data written is "
410			       "only [%zd]. Discarding response packet.\n",
411			       __func__,
412			       (MIN_MSG_PKT_SIZE
413				+ sizeof(struct ecryptfs_message)), count);
414			rc = -EINVAL;
415			goto out_free;
416		}
417		memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
418		seq = be32_to_cpu(counter_nbo);
419		rc = ecryptfs_miscdev_response(file->private_data,
420				&data[PKT_LEN_OFFSET + packet_size_length],
421				packet_size, seq);
422		if (rc) {
423			printk(KERN_WARNING "%s: Failed to deliver miscdev "
424			       "response to requesting operation; rc = [%zd]\n",
425			       __func__, rc);
426			goto out_free;
427		}
428		break;
429	case ECRYPTFS_MSG_HELO:
430	case ECRYPTFS_MSG_QUIT:
431		break;
432	default:
433		ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
434				"message of unrecognized type [%d]\n",
435				data[0]);
436		rc = -EINVAL;
437		goto out_free;
438	}
439	rc = count;
440out_free:
441	kfree(data);
442	return rc;
443}
444
445
446static const struct file_operations ecryptfs_miscdev_fops = {
447	.owner   = THIS_MODULE,
448	.open    = ecryptfs_miscdev_open,
449	.poll    = ecryptfs_miscdev_poll,
450	.read    = ecryptfs_miscdev_read,
451	.write   = ecryptfs_miscdev_write,
452	.release = ecryptfs_miscdev_release,
453	.llseek  = noop_llseek,
454};
455
456static struct miscdevice ecryptfs_miscdev = {
457	.minor = MISC_DYNAMIC_MINOR,
458	.name  = "ecryptfs",
459	.fops  = &ecryptfs_miscdev_fops
460};
461
462/**
463 * ecryptfs_init_ecryptfs_miscdev
464 *
465 * Messages sent to the userspace daemon from the kernel are placed on
466 * a queue associated with the daemon. The next read against the
467 * miscdev handle by that daemon will return the oldest message placed
468 * on the message queue for the daemon.
469 *
470 * Returns zero on success; non-zero otherwise
471 */
472int __init ecryptfs_init_ecryptfs_miscdev(void)
473{
474	int rc;
475
476	atomic_set(&ecryptfs_num_miscdev_opens, 0);
477	rc = misc_register(&ecryptfs_miscdev);
478	if (rc)
479		printk(KERN_ERR "%s: Failed to register miscellaneous device "
480		       "for communications with userspace daemons; rc = [%d]\n",
481		       __func__, rc);
482	return rc;
483}
484
485/**
486 * ecryptfs_destroy_ecryptfs_miscdev
487 *
488 * All of the daemons must be exorcised prior to calling this
489 * function.
490 */
491void ecryptfs_destroy_ecryptfs_miscdev(void)
492{
493	BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
494	misc_deregister(&ecryptfs_miscdev);
495}
496