xref: /openbmc/linux/fs/ecryptfs/file.c (revision c9661827) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * eCryptfs: Linux filesystem encryption layer
4  *
5  * Copyright (C) 1997-2004 Erez Zadok
6  * Copyright (C) 2001-2004 Stony Brook University
7  * Copyright (C) 2004-2007 International Business Machines Corp.
8  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
9  *   		Michael C. Thompson <mcthomps@us.ibm.com>
10  */
11 
12 #include <linux/file.h>
13 #include <linux/poll.h>
14 #include <linux/slab.h>
15 #include <linux/mount.h>
16 #include <linux/pagemap.h>
17 #include <linux/security.h>
18 #include <linux/compat.h>
19 #include <linux/fs_stack.h>
20 #include "ecryptfs_kernel.h"
21 
22 /*
23  * ecryptfs_read_update_atime
24  *
25  * generic_file_read updates the atime of upper layer inode.  But, it
26  * doesn't give us a chance to update the atime of the lower layer
27  * inode.  This function is a wrapper to generic_file_read.  It
28  * updates the atime of the lower level inode if generic_file_read
29  * returns without any errors. This is to be used only for file reads.
30  * The function to be used for directory reads is ecryptfs_read.
31  */
32 static ssize_t ecryptfs_read_update_atime(struct kiocb *iocb,
33 				struct iov_iter *to)
34 {
35 	ssize_t rc;
36 	const struct path *path;
37 	struct file *file = iocb->ki_filp;
38 
39 	rc = generic_file_read_iter(iocb, to);
40 	if (rc >= 0) {
41 		path = ecryptfs_dentry_to_lower_path(file->f_path.dentry);
42 		touch_atime(path);
43 	}
44 	return rc;
45 }
46 
47 struct ecryptfs_getdents_callback {
48 	struct dir_context ctx;
49 	struct dir_context *caller;
50 	struct super_block *sb;
51 	int filldir_called;
52 	int entries_written;
53 };
54 
55 /* Inspired by generic filldir in fs/readdir.c */
56 static bool
57 ecryptfs_filldir(struct dir_context *ctx, const char *lower_name,
58 		 int lower_namelen, loff_t offset, u64 ino, unsigned int d_type)
59 {
60 	struct ecryptfs_getdents_callback *buf =
61 		container_of(ctx, struct ecryptfs_getdents_callback, ctx);
62 	size_t name_size;
63 	char *name;
64 	int err;
65 	bool res;
66 
67 	buf->filldir_called++;
68 	err = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
69 						   buf->sb, lower_name,
70 						   lower_namelen);
71 	if (err) {
72 		if (err != -EINVAL) {
73 			ecryptfs_printk(KERN_DEBUG,
74 					"%s: Error attempting to decode and decrypt filename [%s]; rc = [%d]\n",
75 					__func__, lower_name, err);
76 			return false;
77 		}
78 
79 		/* Mask -EINVAL errors as these are most likely due a plaintext
80 		 * filename present in the lower filesystem despite filename
81 		 * encryption being enabled. One unavoidable example would be
82 		 * the "lost+found" dentry in the root directory of an Ext4
83 		 * filesystem.
84 		 */
85 		return true;
86 	}
87 
88 	buf->caller->pos = buf->ctx.pos;
89 	res = dir_emit(buf->caller, name, name_size, ino, d_type);
90 	kfree(name);
91 	if (res)
92 		buf->entries_written++;
93 	return res;
94 }
95 
96 /**
97  * ecryptfs_readdir
98  * @file: The eCryptfs directory file
99  * @ctx: The actor to feed the entries to
100  */
101 static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
102 {
103 	int rc;
104 	struct file *lower_file;
105 	struct inode *inode = file_inode(file);
106 	struct ecryptfs_getdents_callback buf = {
107 		.ctx.actor = ecryptfs_filldir,
108 		.caller = ctx,
109 		.sb = inode->i_sb,
110 	};
111 	lower_file = ecryptfs_file_to_lower(file);
112 	rc = iterate_dir(lower_file, &buf.ctx);
113 	ctx->pos = buf.ctx.pos;
114 	if (rc >= 0 && (buf.entries_written || !buf.filldir_called))
115 		fsstack_copy_attr_atime(inode, file_inode(lower_file));
116 	return rc;
117 }
118 
119 struct kmem_cache *ecryptfs_file_info_cache;
120 
121 static int read_or_initialize_metadata(struct dentry *dentry)
122 {
123 	struct inode *inode = d_inode(dentry);
124 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
125 	struct ecryptfs_crypt_stat *crypt_stat;
126 	int rc;
127 
128 	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
129 	mount_crypt_stat = &ecryptfs_superblock_to_private(
130 						inode->i_sb)->mount_crypt_stat;
131 	mutex_lock(&crypt_stat->cs_mutex);
132 
133 	if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
134 	    crypt_stat->flags & ECRYPTFS_KEY_VALID) {
135 		rc = 0;
136 		goto out;
137 	}
138 
139 	rc = ecryptfs_read_metadata(dentry);
140 	if (!rc)
141 		goto out;
142 
143 	if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
144 		crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
145 				       | ECRYPTFS_ENCRYPTED);
146 		rc = 0;
147 		goto out;
148 	}
149 
150 	if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
151 	    !i_size_read(ecryptfs_inode_to_lower(inode))) {
152 		rc = ecryptfs_initialize_file(dentry, inode);
153 		if (!rc)
154 			goto out;
155 	}
156 
157 	rc = -EIO;
158 out:
159 	mutex_unlock(&crypt_stat->cs_mutex);
160 	return rc;
161 }
162 
163 static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
164 {
165 	struct file *lower_file = ecryptfs_file_to_lower(file);
166 	/*
167 	 * Don't allow mmap on top of file systems that don't support it
168 	 * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
169 	 * allows recursive mounting, this will need to be extended.
170 	 */
171 	if (!lower_file->f_op->mmap)
172 		return -ENODEV;
173 	return generic_file_mmap(file, vma);
174 }
175 
176 /**
177  * ecryptfs_open
178  * @inode: inode specifying file to open
179  * @file: Structure to return filled in
180  *
181  * Opens the file specified by inode.
182  *
183  * Returns zero on success; non-zero otherwise
184  */
185 static int ecryptfs_open(struct inode *inode, struct file *file)
186 {
187 	int rc = 0;
188 	struct ecryptfs_crypt_stat *crypt_stat = NULL;
189 	struct dentry *ecryptfs_dentry = file->f_path.dentry;
190 	/* Private value of ecryptfs_dentry allocated in
191 	 * ecryptfs_lookup() */
192 	struct ecryptfs_file_info *file_info;
193 
194 	/* Released in ecryptfs_release or end of function if failure */
195 	file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
196 	ecryptfs_set_file_private(file, file_info);
197 	if (!file_info) {
198 		ecryptfs_printk(KERN_ERR,
199 				"Error attempting to allocate memory\n");
200 		rc = -ENOMEM;
201 		goto out;
202 	}
203 	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
204 	mutex_lock(&crypt_stat->cs_mutex);
205 	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
206 		ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
207 		/* Policy code enabled in future release */
208 		crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
209 				      | ECRYPTFS_ENCRYPTED);
210 	}
211 	mutex_unlock(&crypt_stat->cs_mutex);
212 	rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
213 	if (rc) {
214 		printk(KERN_ERR "%s: Error attempting to initialize "
215 			"the lower file for the dentry with name "
216 			"[%pd]; rc = [%d]\n", __func__,
217 			ecryptfs_dentry, rc);
218 		goto out_free;
219 	}
220 	if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
221 	    == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
222 		rc = -EPERM;
223 		printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
224 		       "file must hence be opened RO\n", __func__);
225 		goto out_put;
226 	}
227 	ecryptfs_set_file_lower(
228 		file, ecryptfs_inode_to_private(inode)->lower_file);
229 	rc = read_or_initialize_metadata(ecryptfs_dentry);
230 	if (rc)
231 		goto out_put;
232 	ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
233 			"[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
234 			(unsigned long long)i_size_read(inode));
235 	goto out;
236 out_put:
237 	ecryptfs_put_lower_file(inode);
238 out_free:
239 	kmem_cache_free(ecryptfs_file_info_cache,
240 			ecryptfs_file_to_private(file));
241 out:
242 	return rc;
243 }
244 
245 /**
246  * ecryptfs_dir_open
247  * @inode: inode specifying file to open
248  * @file: Structure to return filled in
249  *
250  * Opens the file specified by inode.
251  *
252  * Returns zero on success; non-zero otherwise
253  */
254 static int ecryptfs_dir_open(struct inode *inode, struct file *file)
255 {
256 	struct dentry *ecryptfs_dentry = file->f_path.dentry;
257 	/* Private value of ecryptfs_dentry allocated in
258 	 * ecryptfs_lookup() */
259 	struct ecryptfs_file_info *file_info;
260 	struct file *lower_file;
261 
262 	/* Released in ecryptfs_release or end of function if failure */
263 	file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
264 	ecryptfs_set_file_private(file, file_info);
265 	if (unlikely(!file_info)) {
266 		ecryptfs_printk(KERN_ERR,
267 				"Error attempting to allocate memory\n");
268 		return -ENOMEM;
269 	}
270 	lower_file = dentry_open(ecryptfs_dentry_to_lower_path(ecryptfs_dentry),
271 				 file->f_flags, current_cred());
272 	if (IS_ERR(lower_file)) {
273 		printk(KERN_ERR "%s: Error attempting to initialize "
274 			"the lower file for the dentry with name "
275 			"[%pd]; rc = [%ld]\n", __func__,
276 			ecryptfs_dentry, PTR_ERR(lower_file));
277 		kmem_cache_free(ecryptfs_file_info_cache, file_info);
278 		return PTR_ERR(lower_file);
279 	}
280 	ecryptfs_set_file_lower(file, lower_file);
281 	return 0;
282 }
283 
284 static int ecryptfs_flush(struct file *file, fl_owner_t td)
285 {
286 	struct file *lower_file = ecryptfs_file_to_lower(file);
287 
288 	if (lower_file->f_op->flush) {
289 		filemap_write_and_wait(file->f_mapping);
290 		return lower_file->f_op->flush(lower_file, td);
291 	}
292 
293 	return 0;
294 }
295 
296 static int ecryptfs_release(struct inode *inode, struct file *file)
297 {
298 	ecryptfs_put_lower_file(inode);
299 	kmem_cache_free(ecryptfs_file_info_cache,
300 			ecryptfs_file_to_private(file));
301 	return 0;
302 }
303 
304 static int ecryptfs_dir_release(struct inode *inode, struct file *file)
305 {
306 	fput(ecryptfs_file_to_lower(file));
307 	kmem_cache_free(ecryptfs_file_info_cache,
308 			ecryptfs_file_to_private(file));
309 	return 0;
310 }
311 
312 static loff_t ecryptfs_dir_llseek(struct file *file, loff_t offset, int whence)
313 {
314 	return vfs_llseek(ecryptfs_file_to_lower(file), offset, whence);
315 }
316 
317 static int
318 ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
319 {
320 	int rc;
321 
322 	rc = file_write_and_wait(file);
323 	if (rc)
324 		return rc;
325 
326 	return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
327 }
328 
329 static int ecryptfs_fasync(int fd, struct file *file, int flag)
330 {
331 	int rc = 0;
332 	struct file *lower_file = NULL;
333 
334 	lower_file = ecryptfs_file_to_lower(file);
335 	if (lower_file->f_op->fasync)
336 		rc = lower_file->f_op->fasync(fd, lower_file, flag);
337 	return rc;
338 }
339 
340 static long
341 ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
342 {
343 	struct file *lower_file = ecryptfs_file_to_lower(file);
344 	long rc = -ENOTTY;
345 
346 	if (!lower_file->f_op->unlocked_ioctl)
347 		return rc;
348 
349 	switch (cmd) {
350 	case FITRIM:
351 	case FS_IOC_GETFLAGS:
352 	case FS_IOC_SETFLAGS:
353 	case FS_IOC_GETVERSION:
354 	case FS_IOC_SETVERSION:
355 		rc = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
356 		fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
357 
358 		return rc;
359 	default:
360 		return rc;
361 	}
362 }
363 
364 #ifdef CONFIG_COMPAT
365 static long
366 ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
367 {
368 	struct file *lower_file = ecryptfs_file_to_lower(file);
369 	long rc = -ENOIOCTLCMD;
370 
371 	if (!lower_file->f_op->compat_ioctl)
372 		return rc;
373 
374 	switch (cmd) {
375 	case FITRIM:
376 	case FS_IOC32_GETFLAGS:
377 	case FS_IOC32_SETFLAGS:
378 	case FS_IOC32_GETVERSION:
379 	case FS_IOC32_SETVERSION:
380 		rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
381 		fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
382 
383 		return rc;
384 	default:
385 		return rc;
386 	}
387 }
388 #endif
389 
390 const struct file_operations ecryptfs_dir_fops = {
391 	.iterate_shared = ecryptfs_readdir,
392 	.read = generic_read_dir,
393 	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
394 #ifdef CONFIG_COMPAT
395 	.compat_ioctl = ecryptfs_compat_ioctl,
396 #endif
397 	.open = ecryptfs_dir_open,
398 	.release = ecryptfs_dir_release,
399 	.fsync = ecryptfs_fsync,
400 	.llseek = ecryptfs_dir_llseek,
401 };
402 
403 const struct file_operations ecryptfs_main_fops = {
404 	.llseek = generic_file_llseek,
405 	.read_iter = ecryptfs_read_update_atime,
406 	.write_iter = generic_file_write_iter,
407 	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
408 #ifdef CONFIG_COMPAT
409 	.compat_ioctl = ecryptfs_compat_ioctl,
410 #endif
411 	.mmap = ecryptfs_mmap,
412 	.open = ecryptfs_open,
413 	.flush = ecryptfs_flush,
414 	.release = ecryptfs_release,
415 	.fsync = ecryptfs_fsync,
416 	.fasync = ecryptfs_fasync,
417 	.splice_read = generic_file_splice_read,
418 };
419