xref: /linux/fs/ecryptfs/file.c (revision cdd5b5a9761fd66d17586e4f4ba6588c70e640ea)
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  */
ecryptfs_read_update_atime(struct kiocb * iocb,struct iov_iter * to)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 /*
48  * ecryptfs_splice_read_update_atime
49  *
50  * filemap_splice_read updates the atime of upper layer inode.  But, it
51  * doesn't give us a chance to update the atime of the lower layer inode.  This
52  * function is a wrapper to generic_file_read.  It updates the atime of the
53  * lower level inode if generic_file_read returns without any errors. This is
54  * to be used only for file reads.  The function to be used for directory reads
55  * is ecryptfs_read.
56  */
ecryptfs_splice_read_update_atime(struct file * in,loff_t * ppos,struct pipe_inode_info * pipe,size_t len,unsigned int flags)57 static ssize_t ecryptfs_splice_read_update_atime(struct file *in, loff_t *ppos,
58 						 struct pipe_inode_info *pipe,
59 						 size_t len, unsigned int flags)
60 {
61 	ssize_t rc;
62 	const struct path *path;
63 
64 	rc = filemap_splice_read(in, ppos, pipe, len, flags);
65 	if (rc >= 0) {
66 		path = ecryptfs_dentry_to_lower_path(in->f_path.dentry);
67 		touch_atime(path);
68 	}
69 	return rc;
70 }
71 
72 struct ecryptfs_getdents_callback {
73 	struct dir_context ctx;
74 	struct dir_context *caller;
75 	struct super_block *sb;
76 	int filldir_called;
77 	int entries_written;
78 };
79 
80 /* Inspired by generic filldir in fs/readdir.c */
81 static bool
ecryptfs_filldir(struct dir_context * ctx,const char * lower_name,int lower_namelen,loff_t offset,u64 ino,unsigned int d_type)82 ecryptfs_filldir(struct dir_context *ctx, const char *lower_name,
83 		 int lower_namelen, loff_t offset, u64 ino, unsigned int d_type)
84 {
85 	struct ecryptfs_getdents_callback *buf =
86 		container_of(ctx, struct ecryptfs_getdents_callback, ctx);
87 	size_t name_size;
88 	char *name;
89 	int err;
90 	bool res;
91 
92 	buf->filldir_called++;
93 	err = ecryptfs_decode_and_decrypt_filename(&name, &name_size,
94 						   buf->sb, lower_name,
95 						   lower_namelen);
96 	if (err) {
97 		if (err != -EINVAL) {
98 			ecryptfs_printk(KERN_DEBUG,
99 					"%s: Error attempting to decode and decrypt filename [%s]; rc = [%d]\n",
100 					__func__, lower_name, err);
101 			return false;
102 		}
103 
104 		/* Mask -EINVAL errors as these are most likely due a plaintext
105 		 * filename present in the lower filesystem despite filename
106 		 * encryption being enabled. One unavoidable example would be
107 		 * the "lost+found" dentry in the root directory of an Ext4
108 		 * filesystem.
109 		 */
110 		return true;
111 	}
112 
113 	buf->caller->pos = buf->ctx.pos;
114 	res = dir_emit(buf->caller, name, name_size, ino, d_type);
115 	kfree(name);
116 	if (res)
117 		buf->entries_written++;
118 	return res;
119 }
120 
121 /**
122  * ecryptfs_readdir
123  * @file: The eCryptfs directory file
124  * @ctx: The actor to feed the entries to
125  */
ecryptfs_readdir(struct file * file,struct dir_context * ctx)126 static int ecryptfs_readdir(struct file *file, struct dir_context *ctx)
127 {
128 	int rc;
129 	struct file *lower_file;
130 	struct inode *inode = file_inode(file);
131 	struct ecryptfs_getdents_callback buf = {
132 		.ctx.actor = ecryptfs_filldir,
133 		.caller = ctx,
134 		.sb = inode->i_sb,
135 	};
136 	lower_file = ecryptfs_file_to_lower(file);
137 	rc = iterate_dir(lower_file, &buf.ctx);
138 	ctx->pos = buf.ctx.pos;
139 	if (rc >= 0 && (buf.entries_written || !buf.filldir_called))
140 		fsstack_copy_attr_atime(inode, file_inode(lower_file));
141 	return rc;
142 }
143 
144 struct kmem_cache *ecryptfs_file_info_cache;
145 
read_or_initialize_metadata(struct dentry * dentry)146 static int read_or_initialize_metadata(struct dentry *dentry)
147 {
148 	struct inode *inode = d_inode(dentry);
149 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
150 	struct ecryptfs_crypt_stat *crypt_stat;
151 	int rc;
152 
153 	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
154 	mount_crypt_stat = &ecryptfs_superblock_to_private(
155 						inode->i_sb)->mount_crypt_stat;
156 	mutex_lock(&crypt_stat->cs_mutex);
157 
158 	if (crypt_stat->flags & ECRYPTFS_POLICY_APPLIED &&
159 	    crypt_stat->flags & ECRYPTFS_KEY_VALID) {
160 		rc = 0;
161 		goto out;
162 	}
163 
164 	rc = ecryptfs_read_metadata(dentry);
165 	if (!rc)
166 		goto out;
167 
168 	if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED) {
169 		crypt_stat->flags &= ~(ECRYPTFS_I_SIZE_INITIALIZED
170 				       | ECRYPTFS_ENCRYPTED);
171 		rc = 0;
172 		goto out;
173 	}
174 
175 	if (!(mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED) &&
176 	    !i_size_read(ecryptfs_inode_to_lower(inode))) {
177 		rc = ecryptfs_initialize_file(dentry, inode);
178 		if (!rc)
179 			goto out;
180 	}
181 
182 	rc = -EIO;
183 out:
184 	mutex_unlock(&crypt_stat->cs_mutex);
185 	return rc;
186 }
187 
ecryptfs_mmap(struct file * file,struct vm_area_struct * vma)188 static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
189 {
190 	struct file *lower_file = ecryptfs_file_to_lower(file);
191 	/*
192 	 * Don't allow mmap on top of file systems that don't support it
193 	 * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
194 	 * allows recursive mounting, this will need to be extended.
195 	 */
196 	if (!lower_file->f_op->mmap)
197 		return -ENODEV;
198 	return generic_file_mmap(file, vma);
199 }
200 
201 /**
202  * ecryptfs_open
203  * @inode: inode specifying file to open
204  * @file: Structure to return filled in
205  *
206  * Opens the file specified by inode.
207  *
208  * Returns zero on success; non-zero otherwise
209  */
ecryptfs_open(struct inode * inode,struct file * file)210 static int ecryptfs_open(struct inode *inode, struct file *file)
211 {
212 	int rc = 0;
213 	struct ecryptfs_crypt_stat *crypt_stat = NULL;
214 	struct dentry *ecryptfs_dentry = file->f_path.dentry;
215 	/* Private value of ecryptfs_dentry allocated in
216 	 * ecryptfs_lookup() */
217 	struct ecryptfs_file_info *file_info;
218 
219 	/* Released in ecryptfs_release or end of function if failure */
220 	file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
221 	ecryptfs_set_file_private(file, file_info);
222 	if (!file_info) {
223 		ecryptfs_printk(KERN_ERR,
224 				"Error attempting to allocate memory\n");
225 		rc = -ENOMEM;
226 		goto out;
227 	}
228 	crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
229 	mutex_lock(&crypt_stat->cs_mutex);
230 	if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)) {
231 		ecryptfs_printk(KERN_DEBUG, "Setting flags for stat...\n");
232 		/* Policy code enabled in future release */
233 		crypt_stat->flags |= (ECRYPTFS_POLICY_APPLIED
234 				      | ECRYPTFS_ENCRYPTED);
235 	}
236 	mutex_unlock(&crypt_stat->cs_mutex);
237 	rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
238 	if (rc) {
239 		printk(KERN_ERR "%s: Error attempting to initialize "
240 			"the lower file for the dentry with name "
241 			"[%pd]; rc = [%d]\n", __func__,
242 			ecryptfs_dentry, rc);
243 		goto out_free;
244 	}
245 	if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_ACCMODE)
246 	    == O_RDONLY && (file->f_flags & O_ACCMODE) != O_RDONLY) {
247 		rc = -EPERM;
248 		printk(KERN_WARNING "%s: Lower file is RO; eCryptfs "
249 		       "file must hence be opened RO\n", __func__);
250 		goto out_put;
251 	}
252 	ecryptfs_set_file_lower(
253 		file, ecryptfs_inode_to_private(inode)->lower_file);
254 	rc = read_or_initialize_metadata(ecryptfs_dentry);
255 	if (rc)
256 		goto out_put;
257 	ecryptfs_printk(KERN_DEBUG, "inode w/ addr = [0x%p], i_ino = "
258 			"[0x%.16lx] size: [0x%.16llx]\n", inode, inode->i_ino,
259 			(unsigned long long)i_size_read(inode));
260 	goto out;
261 out_put:
262 	ecryptfs_put_lower_file(inode);
263 out_free:
264 	kmem_cache_free(ecryptfs_file_info_cache,
265 			ecryptfs_file_to_private(file));
266 out:
267 	return rc;
268 }
269 
270 /**
271  * ecryptfs_dir_open
272  * @inode: inode specifying file to open
273  * @file: Structure to return filled in
274  *
275  * Opens the file specified by inode.
276  *
277  * Returns zero on success; non-zero otherwise
278  */
ecryptfs_dir_open(struct inode * inode,struct file * file)279 static int ecryptfs_dir_open(struct inode *inode, struct file *file)
280 {
281 	struct dentry *ecryptfs_dentry = file->f_path.dentry;
282 	/* Private value of ecryptfs_dentry allocated in
283 	 * ecryptfs_lookup() */
284 	struct ecryptfs_file_info *file_info;
285 	struct file *lower_file;
286 
287 	/* Released in ecryptfs_release or end of function if failure */
288 	file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
289 	ecryptfs_set_file_private(file, file_info);
290 	if (unlikely(!file_info)) {
291 		ecryptfs_printk(KERN_ERR,
292 				"Error attempting to allocate memory\n");
293 		return -ENOMEM;
294 	}
295 	lower_file = dentry_open(ecryptfs_dentry_to_lower_path(ecryptfs_dentry),
296 				 file->f_flags, current_cred());
297 	if (IS_ERR(lower_file)) {
298 		printk(KERN_ERR "%s: Error attempting to initialize "
299 			"the lower file for the dentry with name "
300 			"[%pd]; rc = [%ld]\n", __func__,
301 			ecryptfs_dentry, PTR_ERR(lower_file));
302 		kmem_cache_free(ecryptfs_file_info_cache, file_info);
303 		return PTR_ERR(lower_file);
304 	}
305 	ecryptfs_set_file_lower(file, lower_file);
306 	return 0;
307 }
308 
ecryptfs_flush(struct file * file,fl_owner_t td)309 static int ecryptfs_flush(struct file *file, fl_owner_t td)
310 {
311 	struct file *lower_file = ecryptfs_file_to_lower(file);
312 
313 	if (lower_file->f_op->flush) {
314 		filemap_write_and_wait(file->f_mapping);
315 		return lower_file->f_op->flush(lower_file, td);
316 	}
317 
318 	return 0;
319 }
320 
ecryptfs_release(struct inode * inode,struct file * file)321 static int ecryptfs_release(struct inode *inode, struct file *file)
322 {
323 	ecryptfs_put_lower_file(inode);
324 	kmem_cache_free(ecryptfs_file_info_cache,
325 			ecryptfs_file_to_private(file));
326 	return 0;
327 }
328 
ecryptfs_dir_release(struct inode * inode,struct file * file)329 static int ecryptfs_dir_release(struct inode *inode, struct file *file)
330 {
331 	fput(ecryptfs_file_to_lower(file));
332 	kmem_cache_free(ecryptfs_file_info_cache,
333 			ecryptfs_file_to_private(file));
334 	return 0;
335 }
336 
ecryptfs_dir_llseek(struct file * file,loff_t offset,int whence)337 static loff_t ecryptfs_dir_llseek(struct file *file, loff_t offset, int whence)
338 {
339 	return vfs_llseek(ecryptfs_file_to_lower(file), offset, whence);
340 }
341 
342 static int
ecryptfs_fsync(struct file * file,loff_t start,loff_t end,int datasync)343 ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
344 {
345 	int rc;
346 
347 	rc = file_write_and_wait(file);
348 	if (rc)
349 		return rc;
350 
351 	return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
352 }
353 
ecryptfs_fasync(int fd,struct file * file,int flag)354 static int ecryptfs_fasync(int fd, struct file *file, int flag)
355 {
356 	int rc = 0;
357 	struct file *lower_file = NULL;
358 
359 	lower_file = ecryptfs_file_to_lower(file);
360 	if (lower_file->f_op->fasync)
361 		rc = lower_file->f_op->fasync(fd, lower_file, flag);
362 	return rc;
363 }
364 
365 static long
ecryptfs_unlocked_ioctl(struct file * file,unsigned int cmd,unsigned long arg)366 ecryptfs_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
367 {
368 	struct file *lower_file = ecryptfs_file_to_lower(file);
369 	long rc = -ENOTTY;
370 
371 	if (!lower_file->f_op->unlocked_ioctl)
372 		return rc;
373 
374 	switch (cmd) {
375 	case FITRIM:
376 	case FS_IOC_GETFLAGS:
377 	case FS_IOC_SETFLAGS:
378 	case FS_IOC_GETVERSION:
379 	case FS_IOC_SETVERSION:
380 		rc = lower_file->f_op->unlocked_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 
389 #ifdef CONFIG_COMPAT
390 static long
ecryptfs_compat_ioctl(struct file * file,unsigned int cmd,unsigned long arg)391 ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
392 {
393 	struct file *lower_file = ecryptfs_file_to_lower(file);
394 	long rc = -ENOIOCTLCMD;
395 
396 	if (!lower_file->f_op->compat_ioctl)
397 		return rc;
398 
399 	switch (cmd) {
400 	case FITRIM:
401 	case FS_IOC32_GETFLAGS:
402 	case FS_IOC32_SETFLAGS:
403 	case FS_IOC32_GETVERSION:
404 	case FS_IOC32_SETVERSION:
405 		rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
406 		fsstack_copy_attr_all(file_inode(file), file_inode(lower_file));
407 
408 		return rc;
409 	default:
410 		return rc;
411 	}
412 }
413 #endif
414 
415 const struct file_operations ecryptfs_dir_fops = {
416 	.iterate_shared = ecryptfs_readdir,
417 	.read = generic_read_dir,
418 	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
419 #ifdef CONFIG_COMPAT
420 	.compat_ioctl = ecryptfs_compat_ioctl,
421 #endif
422 	.open = ecryptfs_dir_open,
423 	.release = ecryptfs_dir_release,
424 	.fsync = ecryptfs_fsync,
425 	.llseek = ecryptfs_dir_llseek,
426 };
427 
428 const struct file_operations ecryptfs_main_fops = {
429 	.llseek = generic_file_llseek,
430 	.read_iter = ecryptfs_read_update_atime,
431 	.write_iter = generic_file_write_iter,
432 	.unlocked_ioctl = ecryptfs_unlocked_ioctl,
433 #ifdef CONFIG_COMPAT
434 	.compat_ioctl = ecryptfs_compat_ioctl,
435 #endif
436 	.mmap = ecryptfs_mmap,
437 	.open = ecryptfs_open,
438 	.flush = ecryptfs_flush,
439 	.release = ecryptfs_release,
440 	.fsync = ecryptfs_fsync,
441 	.fasync = ecryptfs_fasync,
442 	.splice_read = ecryptfs_splice_read_update_atime,
443 };
444