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/module.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;
default_canonical_fmt_setup(char * str)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 #define TMPBUFLEN 12
ima_show_htable_value(char __user * buf,size_t count,loff_t * ppos,atomic_long_t * val)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[TMPBUFLEN];
50 	ssize_t len;
51 
52 	len = scnprintf(tmpbuf, TMPBUFLEN, "%li\n", atomic_long_read(val));
53 	return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
54 }
55 
ima_show_htable_violations(struct file * filp,char __user * buf,size_t count,loff_t * ppos)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 
ima_show_measurements_count(struct file * filp,char __user * buf,size_t count,loff_t * ppos)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 */
ima_measurements_start(struct seq_file * m,loff_t * pos)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 
ima_measurements_next(struct seq_file * m,void * v,loff_t * pos)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 
ima_measurements_stop(struct seq_file * m,void * v)114 static void ima_measurements_stop(struct seq_file *m, void *v)
115 {
116 }
117 
ima_putc(struct seq_file * m,void * data,int datalen)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  */
ima_measurements_show(struct seq_file * m,void * v)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 		struct ima_template_field *field = e->template_desc->fields[i];
183 
184 		if (is_ima_template && strcmp(field->field_id, "d") == 0)
185 			show = IMA_SHOW_BINARY_NO_FIELD_LEN;
186 		if (is_ima_template && strcmp(field->field_id, "n") == 0)
187 			show = IMA_SHOW_BINARY_OLD_STRING_FMT;
188 		field->field_show(m, show, &e->template_data[i]);
189 	}
190 	return 0;
191 }
192 
193 static const struct seq_operations ima_measurments_seqops = {
194 	.start = ima_measurements_start,
195 	.next = ima_measurements_next,
196 	.stop = ima_measurements_stop,
197 	.show = ima_measurements_show
198 };
199 
ima_measurements_open(struct inode * inode,struct file * file)200 static int ima_measurements_open(struct inode *inode, struct file *file)
201 {
202 	return seq_open(file, &ima_measurments_seqops);
203 }
204 
205 static const struct file_operations ima_measurements_ops = {
206 	.open = ima_measurements_open,
207 	.read = seq_read,
208 	.llseek = seq_lseek,
209 	.release = seq_release,
210 };
211 
ima_print_digest(struct seq_file * m,u8 * digest,u32 size)212 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
213 {
214 	u32 i;
215 
216 	for (i = 0; i < size; i++)
217 		seq_printf(m, "%02x", *(digest + i));
218 }
219 
220 /* print in ascii */
ima_ascii_measurements_show(struct seq_file * m,void * v)221 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
222 {
223 	/* the list never shrinks, so we don't need a lock here */
224 	struct ima_queue_entry *qe = v;
225 	struct ima_template_entry *e;
226 	char *template_name;
227 	int i;
228 
229 	/* get entry */
230 	e = qe->entry;
231 	if (e == NULL)
232 		return -1;
233 
234 	template_name = (e->template_desc->name[0] != '\0') ?
235 	    e->template_desc->name : e->template_desc->fmt;
236 
237 	/* 1st: PCR used (config option) */
238 	seq_printf(m, "%2d ", e->pcr);
239 
240 	/* 2nd: SHA1 template hash */
241 	ima_print_digest(m, e->digest, TPM_DIGEST_SIZE);
242 
243 	/* 3th:  template name */
244 	seq_printf(m, " %s", template_name);
245 
246 	/* 4th:  template specific data */
247 	for (i = 0; i < e->template_desc->num_fields; i++) {
248 		seq_puts(m, " ");
249 		if (e->template_data[i].len == 0)
250 			continue;
251 
252 		e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
253 							&e->template_data[i]);
254 	}
255 	seq_puts(m, "\n");
256 	return 0;
257 }
258 
259 static const struct seq_operations ima_ascii_measurements_seqops = {
260 	.start = ima_measurements_start,
261 	.next = ima_measurements_next,
262 	.stop = ima_measurements_stop,
263 	.show = ima_ascii_measurements_show
264 };
265 
ima_ascii_measurements_open(struct inode * inode,struct file * file)266 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
267 {
268 	return seq_open(file, &ima_ascii_measurements_seqops);
269 }
270 
271 static const struct file_operations ima_ascii_measurements_ops = {
272 	.open = ima_ascii_measurements_open,
273 	.read = seq_read,
274 	.llseek = seq_lseek,
275 	.release = seq_release,
276 };
277 
ima_read_policy(char * path)278 static ssize_t ima_read_policy(char *path)
279 {
280 	void *data;
281 	char *datap;
282 	loff_t size;
283 	int rc, pathlen = strlen(path);
284 
285 	char *p;
286 
287 	/* remove \n */
288 	datap = path;
289 	strsep(&datap, "\n");
290 
291 	rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
292 	if (rc < 0) {
293 		pr_err("Unable to open file: %s (%d)", path, rc);
294 		return rc;
295 	}
296 
297 	datap = data;
298 	while (size > 0 && (p = strsep(&datap, "\n"))) {
299 		pr_debug("rule: %s\n", p);
300 		rc = ima_parse_add_rule(p);
301 		if (rc < 0)
302 			break;
303 		size -= rc;
304 	}
305 
306 	vfree(data);
307 	if (rc < 0)
308 		return rc;
309 	else if (size)
310 		return -EINVAL;
311 	else
312 		return pathlen;
313 }
314 
ima_write_policy(struct file * file,const char __user * buf,size_t datalen,loff_t * ppos)315 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
316 				size_t datalen, loff_t *ppos)
317 {
318 	char *data;
319 	ssize_t result;
320 
321 	if (datalen >= PAGE_SIZE)
322 		datalen = PAGE_SIZE - 1;
323 
324 	/* No partial writes. */
325 	result = -EINVAL;
326 	if (*ppos != 0)
327 		goto out;
328 
329 	data = memdup_user_nul(buf, datalen);
330 	if (IS_ERR(data)) {
331 		result = PTR_ERR(data);
332 		goto out;
333 	}
334 
335 	result = mutex_lock_interruptible(&ima_write_mutex);
336 	if (result < 0)
337 		goto out_free;
338 
339 	if (data[0] == '/') {
340 		result = ima_read_policy(data);
341 	} else if (ima_appraise & IMA_APPRAISE_POLICY) {
342 		pr_err("signed policy file (specified as an absolute pathname) required\n");
343 		integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
344 				    "policy_update", "signed policy required",
345 				    1, 0);
346 		if (ima_appraise & IMA_APPRAISE_ENFORCE)
347 			result = -EACCES;
348 	} else {
349 		result = ima_parse_add_rule(data);
350 	}
351 	mutex_unlock(&ima_write_mutex);
352 out_free:
353 	kfree(data);
354 out:
355 	if (result < 0)
356 		valid_policy = 0;
357 
358 	return result;
359 }
360 
361 static struct dentry *ima_dir;
362 static struct dentry *ima_symlink;
363 static struct dentry *binary_runtime_measurements;
364 static struct dentry *ascii_runtime_measurements;
365 static struct dentry *runtime_measurements_count;
366 static struct dentry *violations;
367 static struct dentry *ima_policy;
368 
369 enum ima_fs_flags {
370 	IMA_FS_BUSY,
371 };
372 
373 static unsigned long ima_fs_flags;
374 
375 #ifdef	CONFIG_IMA_READ_POLICY
376 static const struct seq_operations ima_policy_seqops = {
377 		.start = ima_policy_start,
378 		.next = ima_policy_next,
379 		.stop = ima_policy_stop,
380 		.show = ima_policy_show,
381 };
382 #endif
383 
384 /*
385  * ima_open_policy: sequentialize access to the policy file
386  */
ima_open_policy(struct inode * inode,struct file * filp)387 static int ima_open_policy(struct inode *inode, struct file *filp)
388 {
389 	if (!(filp->f_flags & O_WRONLY)) {
390 #ifndef	CONFIG_IMA_READ_POLICY
391 		return -EACCES;
392 #else
393 		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
394 			return -EACCES;
395 		if (!capable(CAP_SYS_ADMIN))
396 			return -EPERM;
397 		return seq_open(filp, &ima_policy_seqops);
398 #endif
399 	}
400 	if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
401 		return -EBUSY;
402 	return 0;
403 }
404 
405 /*
406  * ima_release_policy - start using the new measure policy rules.
407  *
408  * Initially, ima_measure points to the default policy rules, now
409  * point to the new policy rules, and remove the securityfs policy file,
410  * assuming a valid policy.
411  */
ima_release_policy(struct inode * inode,struct file * file)412 static int ima_release_policy(struct inode *inode, struct file *file)
413 {
414 	const char *cause = valid_policy ? "completed" : "failed";
415 
416 	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
417 		return seq_release(inode, file);
418 
419 	if (valid_policy && ima_check_policy() < 0) {
420 		cause = "failed";
421 		valid_policy = 0;
422 	}
423 
424 	pr_info("policy update %s\n", cause);
425 	integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
426 			    "policy_update", cause, !valid_policy, 0);
427 
428 	if (!valid_policy) {
429 		ima_delete_rules();
430 		valid_policy = 1;
431 		clear_bit(IMA_FS_BUSY, &ima_fs_flags);
432 		return 0;
433 	}
434 
435 	ima_update_policy();
436 #if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
437 	securityfs_remove(ima_policy);
438 	ima_policy = NULL;
439 #elif defined(CONFIG_IMA_WRITE_POLICY)
440 	clear_bit(IMA_FS_BUSY, &ima_fs_flags);
441 #elif defined(CONFIG_IMA_READ_POLICY)
442 	inode->i_mode &= ~S_IWUSR;
443 #endif
444 	return 0;
445 }
446 
447 static const struct file_operations ima_measure_policy_ops = {
448 	.open = ima_open_policy,
449 	.write = ima_write_policy,
450 	.read = seq_read,
451 	.release = ima_release_policy,
452 	.llseek = generic_file_llseek,
453 };
454 
ima_fs_init(void)455 int __init ima_fs_init(void)
456 {
457 	ima_dir = securityfs_create_dir("ima", integrity_dir);
458 	if (IS_ERR(ima_dir))
459 		return -1;
460 
461 	ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
462 						NULL);
463 	if (IS_ERR(ima_symlink))
464 		goto out;
465 
466 	binary_runtime_measurements =
467 	    securityfs_create_file("binary_runtime_measurements",
468 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
469 				   &ima_measurements_ops);
470 	if (IS_ERR(binary_runtime_measurements))
471 		goto out;
472 
473 	ascii_runtime_measurements =
474 	    securityfs_create_file("ascii_runtime_measurements",
475 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
476 				   &ima_ascii_measurements_ops);
477 	if (IS_ERR(ascii_runtime_measurements))
478 		goto out;
479 
480 	runtime_measurements_count =
481 	    securityfs_create_file("runtime_measurements_count",
482 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
483 				   &ima_measurements_count_ops);
484 	if (IS_ERR(runtime_measurements_count))
485 		goto out;
486 
487 	violations =
488 	    securityfs_create_file("violations", S_IRUSR | S_IRGRP,
489 				   ima_dir, NULL, &ima_htable_violations_ops);
490 	if (IS_ERR(violations))
491 		goto out;
492 
493 	ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
494 					    ima_dir, NULL,
495 					    &ima_measure_policy_ops);
496 	if (IS_ERR(ima_policy))
497 		goto out;
498 
499 	return 0;
500 out:
501 	securityfs_remove(violations);
502 	securityfs_remove(runtime_measurements_count);
503 	securityfs_remove(ascii_runtime_measurements);
504 	securityfs_remove(binary_runtime_measurements);
505 	securityfs_remove(ima_symlink);
506 	securityfs_remove(ima_dir);
507 	securityfs_remove(ima_policy);
508 	return -1;
509 }
510