xref: /linux/fs/ecryptfs/file.c (revision 3b27d13940c3710a1128527c43719cb0bb05d73b) 
1 /**
2  * eCryptfs: Linux filesystem encryption layer
3  *
4  * Copyright (C) 1997-2004 Erez Zadok
5  * Copyright (C) 2001-2004 Stony Brook University
6  * Copyright (C) 2004-2007 International Business Machines Corp.
7  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
8  *   		Michael C. Thompson <mcthomps@us.ibm.com>
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public License as
12  * published by the Free Software Foundation; either version 2 of the
13  * License, or (at your option) any later version.
14  *
15  * This program is distributed in the hope that it will be useful, but
16  * WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18  * General Public License for more details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with this program; if not, write to the Free Software
22  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
23  * 02111-1307, USA.
24  */
25 
26 #include <linux/file.h>
27 #include <linux/poll.h>
28 #include <linux/slab.h>
29 #include <linux/mount.h>
30 #include <linux/pagemap.h>
31 #include <linux/security.h>
32 #include <linux/compat.h>
33 #include <linux/fs_stack.h>
34 #include "ecryptfs_kernel.h"
35 
36 /**
37  * ecryptfs_read_update_atime
38  *
39  * generic_file_read updates the atime of upper layer inode.  But, it
40  * doesn't give us a chance to update the atime of the lower layer
41  * inode.  This function is a wrapper to generic_file_read.  It
42  * updates the atime of the lower level inode if generic_file_read
43  * returns without any errors. This is to be used only for file reads.
44  * The function to be used for directory reads is ecryptfs_read.
45  */
46 static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
47 				struct iov_iter *to)
48 {
49 	ssize_t rc;
50 	struct path *path;
51 	struct file *file = iocb->ki_filp;
52 
53 	rc = generic_file_read_iter(iocb, to);
54 	if (rc >= 0) {
55 		path = ecryptfs_dentry_to_lower_path(file->f_path.dentry);
56 		touch_atime(path);
57 	}
58 	return rc;
59 }
60 
61 struct ecryptfs_getdents_callback {
62 	struct dir_context ctx;
63 	struct dir_context *caller;
64 	struct super_block *sb;
65 	int filldir_called;
66 	int entries_written;
67 };
68 
69 /* Inspired by generic filldir in fs/readdir.c */
70 static int
71 ecryptfs_filldir(struct dir_context *ctx, const char *lower_name,
72 		 int lower_namelen, loff_t offset, u64 ino, unsigned int d_type)
73 {
74 	struct ecryptfs_getdents_callback *buf =
75 		container_of(ctx, struct ecryptfs_getdents_callback, ctx);
76 	size_t name_size;
77 	char *name;
78 	int rc;
79 
80 	buf->filldir_called++;
81 	rc = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
82 						  buf->sb, lower_name,
83 						  lower_namelen);
84 	if (rc) {
85 		printk(KERN_ERR "%s: Error attempting to decode and decrypt "
86 		       "filename [%s]; rc = [%d]\n", __func__, lower_name,
87 		       rc);
88 		goto out;
89 	}
90 	buf->caller->pos = buf->ctx.pos;
91 	rc = !dir_emit(buf->caller, name, name_size, ino, d_type);
92 	kfree(name);
93 	if (!rc)
94 		buf->entries_written++;
95 out:
96 	return rc;
97 }
98 
99 /**
100  * ecryptfs_readdir
101  * @file: The eCryptfs directory file
102  * @ctx: The actor to feed the entries to
103  */
104 static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
105 {
106 	int rc;
107 	struct file *lower_file;
108 	struct inode *inode = file_inode(file);
109 	struct ecryptfs_getdents_callback buf = {
110 		.ctx.actor = ecryptfs_filldir,
111 		.caller = ctx,
112 		.sb = inode->i_sb,
113 	};
114 	lower_file = ecryptfs_file_to_lower(file);
115 	lower_file->f_pos = ctx->pos;
116 	rc = iterate_dir(lower_file, &buf.ctx);
117 	ctx->pos = buf.ctx.pos;
118 	if (rc < 0)
119 		goto out;
120 	if (buf.filldir_called && !buf.entries_written)
121 		goto out;
122 	if (rc >= 0)
123 		fsstack_copy_attr_atime(inode,
124 					file_inode(lower_file));
125 out:
126 	return rc;
127 }
128 
129 struct kmem_cache *ecryptfs_file_info_cache;
130 
131 static int read_or_initialize_metadata(struct dentry *dentry)
132 {
133 	struct inode *inode = d_inode(dentry);
134 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
135 	struct ecryptfs_crypt_stat *crypt_stat;
136 	int rc;
137 
138 	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
139 	mount_crypt_stat = &ecryptfs_superblock_to_private(
140 						inode->i_sb)->mount_crypt_stat;
141 	mutex_lock(&crypt_stat->cs_mutex);
142 
143 	if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
144 	    crypt_stat->flags & ECRYPTFS_KEY_VALID) {
145 		rc = 0;
146 		goto out;
147 	}
148 
149 	rc = ecryptfs_read_metadata(dentry);
150 	if (!rc)
151 		goto out;
152 
153 	if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
154 		crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
155 				       | ECRYPTFS_ENCRYPTED);
156 		rc = 0;
157 		goto out;
158 	}
159 
160 	if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
161 	    !i_size_read(ecryptfs_inode_to_lower(inode))) {
162 		rc = ecryptfs_initialize_file(dentry, inode);
163 		if (!rc)
164 			goto out;
165 	}
166 
167 	rc = -EIO;
168 out:
169 	mutex_unlock(&crypt_stat->cs_mutex);
170 	return rc;
171 }
172 
173 /**
174  * ecryptfs_open
175  * @inode: inode speciying file to open
176  * @file: Structure to return filled in
177  *
178  * Opens the file specified by inode.
179  *
180  * Returns zero on success; non-zero otherwise
181  */
182 static int ecryptfs_open(struct inode *inode, struct file *file)
183 {
184 	int rc = 0;
185 	struct ecryptfs_crypt_stat *crypt_stat = NULL;
186 	struct dentry *ecryptfs_dentry = file->f_path.dentry;
187 	/* Private value of ecryptfs_dentry allocated in
188 	 * ecryptfs_lookup() */
189 	struct ecryptfs_file_info *file_info;
190 
191 	/* Released in ecryptfs_release or end of function if failure */
192 	file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
193 	ecryptfs_set_file_private(file, file_info);
194 	if (!file_info) {
195 		ecryptfs_printk(KERN_ERR,
196 				"Error attempting to allocate memory\n");
197 		rc = -ENOMEM;
198 		goto out;
199 	}
200 	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
201 	mutex_lock(&crypt_stat->cs_mutex);
202 	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
203 		ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
204 		/* Policy code enabled in future release */
205 		crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
206 				      | ECRYPTFS_ENCRYPTED);
207 	}
208 	mutex_unlock(&crypt_stat->cs_mutex);
209 	rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
210 	if (rc) {
211 		printk(KERN_ERR "%s: Error attempting to initialize "
212 			"the lower file for the dentry with name "
213 			"[%pd]; rc = [%d]\n", __func__,
214 			ecryptfs_dentry, rc);
215 		goto out_free;
216 	}
217 	if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
218 	    == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
219 		rc = -EPERM;
220 		printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
221 		       "file must hence be opened RO\n", __func__);
222 		goto out_put;
223 	}
224 	ecryptfs_set_file_lower(
225 		file, ecryptfs_inode_to_private(inode)->lower_file);
226 	if (d_is_dir(ecryptfs_dentry)) {
227 		ecryptfs_printk(KERN_DEBUG, "This is a directory\n");
228 		mutex_lock(&crypt_stat->cs_mutex);
229 		crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
230 		mutex_unlock(&crypt_stat->cs_mutex);
231 		rc = 0;
232 		goto out;
233 	}
234 	rc = read_or_initialize_metadata(ecryptfs_dentry);
235 	if (rc)
236 		goto out_put;
237 	ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
238 			"[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
239 			(unsigned long long)i_size_read(inode));
240 	goto out;
241 out_put:
242 	ecryptfs_put_lower_file(inode);
243 out_free:
244 	kmem_cache_free(ecryptfs_file_info_cache,
245 			ecryptfs_file_to_private(file));
246 out:
247 	return rc;
248 }
249 
250 static int ecryptfs_flush(struct file *file, fl_owner_t td)
251 {
252 	struct file *lower_file = ecryptfs_file_to_lower(file);
253 
254 	if (lower_file->f_op->flush) {
255 		filemap_write_and_wait(file->f_mapping);
256 		return lower_file->f_op->flush(lower_file, td);
257 	}
258 
259 	return 0;
260 }
261 
262 static int ecryptfs_release(struct inode *inode, struct file *file)
263 {
264 	ecryptfs_put_lower_file(inode);
265 	kmem_cache_free(ecryptfs_file_info_cache,
266 			ecryptfs_file_to_private(file));
267 	return 0;
268 }
269 
270 static int
271 ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
272 {
273 	int rc;
274 
275 	rc = filemap_write_and_wait(file->f_mapping);
276 	if (rc)
277 		return rc;
278 
279 	return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
280 }
281 
282 static int ecryptfs_fasync(int fd, struct file *file, int flag)
283 {
284 	int rc = 0;
285 	struct file *lower_file = NULL;
286 
287 	lower_file = ecryptfs_file_to_lower(file);
288 	if (lower_file->f_op->fasync)
289 		rc = lower_file->f_op->fasync(fd, lower_file, flag);
290 	return rc;
291 }
292 
293 static long
294 ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
295 {
296 	struct file *lower_file = ecryptfs_file_to_lower(file);
297 	long rc = -ENOTTY;
298 
299 	if (!lower_file->f_op->unlocked_ioctl)
300 		return rc;
301 
302 	switch (cmd) {
303 	case FITRIM:
304 	case FS_IOC_GETFLAGS:
305 	case FS_IOC_SETFLAGS:
306 	case FS_IOC_GETVERSION:
307 	case FS_IOC_SETVERSION:
308 		rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
309 		fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
310 
311 		return rc;
312 	default:
313 		return rc;
314 	}
315 }
316 
317 #ifdef CONFIG_COMPAT
318 static long
319 ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
320 {
321 	struct file *lower_file = ecryptfs_file_to_lower(file);
322 	long rc = -ENOIOCTLCMD;
323 
324 	if (!lower_file->f_op->compat_ioctl)
325 		return rc;
326 
327 	switch (cmd) {
328 	case FS_IOC32_GETFLAGS:
329 	case FS_IOC32_SETFLAGS:
330 	case FS_IOC32_GETVERSION:
331 	case FS_IOC32_SETVERSION:
332 		rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
333 		fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
334 
335 		return rc;
336 	default:
337 		return rc;
338 	}
339 }
340 #endif
341 
342 const struct file_operations ecryptfs_dir_fops = {
343 	.iterate = ecryptfs_readdir,
344 	.read = generic_read_dir,
345 	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
346 #ifdef CONFIG_COMPAT
347 	.compat_ioctl = ecryptfs_compat_ioctl,
348 #endif
349 	.open = ecryptfs_open,
350 	.flush = ecryptfs_flush,
351 	.release = ecryptfs_release,
352 	.fsync = ecryptfs_fsync,
353 	.fasync = ecryptfs_fasync,
354 	.splice_read = generic_file_splice_read,
355 	.llseek = default_llseek,
356 };
357 
358 const struct file_operations ecryptfs_main_fops = {
359 	.llseek = generic_file_llseek,
360 	.read_iter = ecryptfs_read_update_atime,
361 	.write_iter = generic_file_write_iter,
362 	.iterate = ecryptfs_readdir,
363 	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
364 #ifdef CONFIG_COMPAT
365 	.compat_ioctl = ecryptfs_compat_ioctl,
366 #endif
367 	.mmap = generic_file_mmap,
368 	.open = ecryptfs_open,
369 	.flush = ecryptfs_flush,
370 	.release = ecryptfs_release,
371 	.fsync = ecryptfs_fsync,
372 	.fasync = ecryptfs_fasync,
373 	.splice_read = generic_file_splice_read,
374 };
375