xref: /linux/security/integrity/ima/ima_fs.c (revision bd628c1bed7902ec1f24ba0fe70758949146abbe)
1 /*
2  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
3  *
4  * Authors:
5  * Kylene Hall <kjhall@us.ibm.com>
6  * Reiner Sailer <sailer@us.ibm.com>
7  * Mimi Zohar <zohar@us.ibm.com>
8  *
9  * This program is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU General Public License as
11  * published by the Free Software Foundation, version 2 of the
12  * License.
13  *
14  * File: ima_fs.c
15  *	implemenents security file system for reporting
16  *	current measurement list and IMA statistics
17  */
18 
19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
20 
21 #include <linux/fcntl.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/seq_file.h>
25 #include <linux/rculist.h>
26 #include <linux/rcupdate.h>
27 #include <linux/parser.h>
28 #include <linux/vmalloc.h>
29 
30 #include "ima.h"
31 
32 static DEFINE_MUTEX(ima_write_mutex);
33 
34 bool ima_canonical_fmt;
35 static int __init default_canonical_fmt_setup(char *str)
36 {
37 #ifdef __BIG_ENDIAN
38 	ima_canonical_fmt = true;
39 #endif
40 	return 1;
41 }
42 __setup("ima_canonical_fmt", default_canonical_fmt_setup);
43 
44 static int valid_policy = 1;
45 
46 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
47 				     loff_t *ppos, atomic_long_t *val)
48 {
49 	char tmpbuf[32];	/* greater than largest 'long' string value */
50 	ssize_t len;
51 
52 	len = scnprintf(tmpbuf, sizeof(tmpbuf), "%li\n", atomic_long_read(val));
53 	return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
54 }
55 
56 static ssize_t ima_show_htable_violations(struct file *filp,
57 					  char __user *buf,
58 					  size_t count, loff_t *ppos)
59 {
60 	return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
61 }
62 
63 static const struct file_operations ima_htable_violations_ops = {
64 	.read = ima_show_htable_violations,
65 	.llseek = generic_file_llseek,
66 };
67 
68 static ssize_t ima_show_measurements_count(struct file *filp,
69 					   char __user *buf,
70 					   size_t count, loff_t *ppos)
71 {
72 	return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
73 
74 }
75 
76 static const struct file_operations ima_measurements_count_ops = {
77 	.read = ima_show_measurements_count,
78 	.llseek = generic_file_llseek,
79 };
80 
81 /* returns pointer to hlist_node */
82 static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
83 {
84 	loff_t l = *pos;
85 	struct ima_queue_entry *qe;
86 
87 	/* we need a lock since pos could point beyond last element */
88 	rcu_read_lock();
89 	list_for_each_entry_rcu(qe, &ima_measurements, later) {
90 		if (!l--) {
91 			rcu_read_unlock();
92 			return qe;
93 		}
94 	}
95 	rcu_read_unlock();
96 	return NULL;
97 }
98 
99 static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
100 {
101 	struct ima_queue_entry *qe = v;
102 
103 	/* lock protects when reading beyond last element
104 	 * against concurrent list-extension
105 	 */
106 	rcu_read_lock();
107 	qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
108 	rcu_read_unlock();
109 	(*pos)++;
110 
111 	return (&qe->later == &ima_measurements) ? NULL : qe;
112 }
113 
114 static void ima_measurements_stop(struct seq_file *m, void *v)
115 {
116 }
117 
118 void ima_putc(struct seq_file *m, void *data, int datalen)
119 {
120 	while (datalen--)
121 		seq_putc(m, *(char *)data++);
122 }
123 
124 /* print format:
125  *       32bit-le=pcr#
126  *       char[20]=template digest
127  *       32bit-le=template name size
128  *       char[n]=template name
129  *       [eventdata length]
130  *       eventdata[n]=template specific data
131  */
132 int ima_measurements_show(struct seq_file *m, void *v)
133 {
134 	/* the list never shrinks, so we don't need a lock here */
135 	struct ima_queue_entry *qe = v;
136 	struct ima_template_entry *e;
137 	char *template_name;
138 	u32 pcr, namelen, template_data_len; /* temporary fields */
139 	bool is_ima_template = false;
140 	int i;
141 
142 	/* get entry */
143 	e = qe->entry;
144 	if (e == NULL)
145 		return -1;
146 
147 	template_name = (e->template_desc->name[0] != '\0') ?
148 	    e->template_desc->name : e->template_desc->fmt;
149 
150 	/*
151 	 * 1st: PCRIndex
152 	 * PCR used defaults to the same (config option) in
153 	 * little-endian format, unless set in policy
154 	 */
155 	pcr = !ima_canonical_fmt ? e->pcr : cpu_to_le32(e->pcr);
156 	ima_putc(m, &pcr, sizeof(e->pcr));
157 
158 	/* 2nd: template digest */
159 	ima_putc(m, e->digest, TPM_DIGEST_SIZE);
160 
161 	/* 3rd: template name size */
162 	namelen = !ima_canonical_fmt ? strlen(template_name) :
163 		cpu_to_le32(strlen(template_name));
164 	ima_putc(m, &namelen, sizeof(namelen));
165 
166 	/* 4th:  template name */
167 	ima_putc(m, template_name, strlen(template_name));
168 
169 	/* 5th:  template length (except for 'ima' template) */
170 	if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
171 		is_ima_template = true;
172 
173 	if (!is_ima_template) {
174 		template_data_len = !ima_canonical_fmt ? e->template_data_len :
175 			cpu_to_le32(e->template_data_len);
176 		ima_putc(m, &template_data_len, sizeof(e->template_data_len));
177 	}
178 
179 	/* 6th:  template specific data */
180 	for (i = 0; i < e->template_desc->num_fields; i++) {
181 		enum ima_show_type show = IMA_SHOW_BINARY;
182 		const struct ima_template_field *field =
183 			e->template_desc->fields[i];
184 
185 		if (is_ima_template && strcmp(field->field_id, "d") == 0)
186 			show = IMA_SHOW_BINARY_NO_FIELD_LEN;
187 		if (is_ima_template && strcmp(field->field_id, "n") == 0)
188 			show = IMA_SHOW_BINARY_OLD_STRING_FMT;
189 		field->field_show(m, show, &e->template_data[i]);
190 	}
191 	return 0;
192 }
193 
194 static const struct seq_operations ima_measurments_seqops = {
195 	.start = ima_measurements_start,
196 	.next = ima_measurements_next,
197 	.stop = ima_measurements_stop,
198 	.show = ima_measurements_show
199 };
200 
201 static int ima_measurements_open(struct inode *inode, struct file *file)
202 {
203 	return seq_open(file, &ima_measurments_seqops);
204 }
205 
206 static const struct file_operations ima_measurements_ops = {
207 	.open = ima_measurements_open,
208 	.read = seq_read,
209 	.llseek = seq_lseek,
210 	.release = seq_release,
211 };
212 
213 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
214 {
215 	u32 i;
216 
217 	for (i = 0; i < size; i++)
218 		seq_printf(m, "%02x", *(digest + i));
219 }
220 
221 /* print in ascii */
222 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
223 {
224 	/* the list never shrinks, so we don't need a lock here */
225 	struct ima_queue_entry *qe = v;
226 	struct ima_template_entry *e;
227 	char *template_name;
228 	int i;
229 
230 	/* get entry */
231 	e = qe->entry;
232 	if (e == NULL)
233 		return -1;
234 
235 	template_name = (e->template_desc->name[0] != '\0') ?
236 	    e->template_desc->name : e->template_desc->fmt;
237 
238 	/* 1st: PCR used (config option) */
239 	seq_printf(m, "%2d ", e->pcr);
240 
241 	/* 2nd: SHA1 template hash */
242 	ima_print_digest(m, e->digest, TPM_DIGEST_SIZE);
243 
244 	/* 3th:  template name */
245 	seq_printf(m, " %s", template_name);
246 
247 	/* 4th:  template specific data */
248 	for (i = 0; i < e->template_desc->num_fields; i++) {
249 		seq_puts(m, " ");
250 		if (e->template_data[i].len == 0)
251 			continue;
252 
253 		e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
254 							&e->template_data[i]);
255 	}
256 	seq_puts(m, "\n");
257 	return 0;
258 }
259 
260 static const struct seq_operations ima_ascii_measurements_seqops = {
261 	.start = ima_measurements_start,
262 	.next = ima_measurements_next,
263 	.stop = ima_measurements_stop,
264 	.show = ima_ascii_measurements_show
265 };
266 
267 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
268 {
269 	return seq_open(file, &ima_ascii_measurements_seqops);
270 }
271 
272 static const struct file_operations ima_ascii_measurements_ops = {
273 	.open = ima_ascii_measurements_open,
274 	.read = seq_read,
275 	.llseek = seq_lseek,
276 	.release = seq_release,
277 };
278 
279 static ssize_t ima_read_policy(char *path)
280 {
281 	void *data;
282 	char *datap;
283 	loff_t size;
284 	int rc, pathlen = strlen(path);
285 
286 	char *p;
287 
288 	/* remove \n */
289 	datap = path;
290 	strsep(&datap, "\n");
291 
292 	rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
293 	if (rc < 0) {
294 		pr_err("Unable to open file: %s (%d)", path, rc);
295 		return rc;
296 	}
297 
298 	datap = data;
299 	while (size > 0 && (p = strsep(&datap, "\n"))) {
300 		pr_debug("rule: %s\n", p);
301 		rc = ima_parse_add_rule(p);
302 		if (rc < 0)
303 			break;
304 		size -= rc;
305 	}
306 
307 	vfree(data);
308 	if (rc < 0)
309 		return rc;
310 	else if (size)
311 		return -EINVAL;
312 	else
313 		return pathlen;
314 }
315 
316 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
317 				size_t datalen, loff_t *ppos)
318 {
319 	char *data;
320 	ssize_t result;
321 
322 	if (datalen >= PAGE_SIZE)
323 		datalen = PAGE_SIZE - 1;
324 
325 	/* No partial writes. */
326 	result = -EINVAL;
327 	if (*ppos != 0)
328 		goto out;
329 
330 	data = memdup_user_nul(buf, datalen);
331 	if (IS_ERR(data)) {
332 		result = PTR_ERR(data);
333 		goto out;
334 	}
335 
336 	result = mutex_lock_interruptible(&ima_write_mutex);
337 	if (result < 0)
338 		goto out_free;
339 
340 	if (data[0] == '/') {
341 		result = ima_read_policy(data);
342 	} else if (ima_appraise & IMA_APPRAISE_POLICY) {
343 		pr_err("signed policy file (specified as an absolute pathname) required\n");
344 		integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
345 				    "policy_update", "signed policy required",
346 				    1, 0);
347 		if (ima_appraise & IMA_APPRAISE_ENFORCE)
348 			result = -EACCES;
349 	} else {
350 		result = ima_parse_add_rule(data);
351 	}
352 	mutex_unlock(&ima_write_mutex);
353 out_free:
354 	kfree(data);
355 out:
356 	if (result < 0)
357 		valid_policy = 0;
358 
359 	return result;
360 }
361 
362 static struct dentry *ima_dir;
363 static struct dentry *ima_symlink;
364 static struct dentry *binary_runtime_measurements;
365 static struct dentry *ascii_runtime_measurements;
366 static struct dentry *runtime_measurements_count;
367 static struct dentry *violations;
368 static struct dentry *ima_policy;
369 
370 enum ima_fs_flags {
371 	IMA_FS_BUSY,
372 };
373 
374 static unsigned long ima_fs_flags;
375 
376 #ifdef	CONFIG_IMA_READ_POLICY
377 static const struct seq_operations ima_policy_seqops = {
378 		.start = ima_policy_start,
379 		.next = ima_policy_next,
380 		.stop = ima_policy_stop,
381 		.show = ima_policy_show,
382 };
383 #endif
384 
385 /*
386  * ima_open_policy: sequentialize access to the policy file
387  */
388 static int ima_open_policy(struct inode *inode, struct file *filp)
389 {
390 	if (!(filp->f_flags & O_WRONLY)) {
391 #ifndef	CONFIG_IMA_READ_POLICY
392 		return -EACCES;
393 #else
394 		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
395 			return -EACCES;
396 		if (!capable(CAP_SYS_ADMIN))
397 			return -EPERM;
398 		return seq_open(filp, &ima_policy_seqops);
399 #endif
400 	}
401 	if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
402 		return -EBUSY;
403 	return 0;
404 }
405 
406 /*
407  * ima_release_policy - start using the new measure policy rules.
408  *
409  * Initially, ima_measure points to the default policy rules, now
410  * point to the new policy rules, and remove the securityfs policy file,
411  * assuming a valid policy.
412  */
413 static int ima_release_policy(struct inode *inode, struct file *file)
414 {
415 	const char *cause = valid_policy ? "completed" : "failed";
416 
417 	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
418 		return seq_release(inode, file);
419 
420 	if (valid_policy && ima_check_policy() < 0) {
421 		cause = "failed";
422 		valid_policy = 0;
423 	}
424 
425 	pr_info("policy update %s\n", cause);
426 	integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
427 			    "policy_update", cause, !valid_policy, 0);
428 
429 	if (!valid_policy) {
430 		ima_delete_rules();
431 		valid_policy = 1;
432 		clear_bit(IMA_FS_BUSY, &ima_fs_flags);
433 		return 0;
434 	}
435 
436 	ima_update_policy();
437 #if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
438 	securityfs_remove(ima_policy);
439 	ima_policy = NULL;
440 #elif defined(CONFIG_IMA_WRITE_POLICY)
441 	clear_bit(IMA_FS_BUSY, &ima_fs_flags);
442 #elif defined(CONFIG_IMA_READ_POLICY)
443 	inode->i_mode &= ~S_IWUSR;
444 #endif
445 	return 0;
446 }
447 
448 static const struct file_operations ima_measure_policy_ops = {
449 	.open = ima_open_policy,
450 	.write = ima_write_policy,
451 	.read = seq_read,
452 	.release = ima_release_policy,
453 	.llseek = generic_file_llseek,
454 };
455 
456 int __init ima_fs_init(void)
457 {
458 	ima_dir = securityfs_create_dir("ima", integrity_dir);
459 	if (IS_ERR(ima_dir))
460 		return -1;
461 
462 	ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
463 						NULL);
464 	if (IS_ERR(ima_symlink))
465 		goto out;
466 
467 	binary_runtime_measurements =
468 	    securityfs_create_file("binary_runtime_measurements",
469 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
470 				   &ima_measurements_ops);
471 	if (IS_ERR(binary_runtime_measurements))
472 		goto out;
473 
474 	ascii_runtime_measurements =
475 	    securityfs_create_file("ascii_runtime_measurements",
476 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
477 				   &ima_ascii_measurements_ops);
478 	if (IS_ERR(ascii_runtime_measurements))
479 		goto out;
480 
481 	runtime_measurements_count =
482 	    securityfs_create_file("runtime_measurements_count",
483 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
484 				   &ima_measurements_count_ops);
485 	if (IS_ERR(runtime_measurements_count))
486 		goto out;
487 
488 	violations =
489 	    securityfs_create_file("violations", S_IRUSR | S_IRGRP,
490 				   ima_dir, NULL, &ima_htable_violations_ops);
491 	if (IS_ERR(violations))
492 		goto out;
493 
494 	ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
495 					    ima_dir, NULL,
496 					    &ima_measure_policy_ops);
497 	if (IS_ERR(ima_policy))
498 		goto out;
499 
500 	return 0;
501 out:
502 	securityfs_remove(violations);
503 	securityfs_remove(runtime_measurements_count);
504 	securityfs_remove(ascii_runtime_measurements);
505 	securityfs_remove(binary_runtime_measurements);
506 	securityfs_remove(ima_symlink);
507 	securityfs_remove(ima_dir);
508 	securityfs_remove(ima_policy);
509 	return -1;
510 }
511