1 /*
2 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
3 *
4 * Authors:
5 * Reiner Sailer <sailer@watson.ibm.com>
6 * Serge Hallyn <serue@us.ibm.com>
7 * Kylene Hall <kylene@us.ibm.com>
8 * Mimi Zohar <zohar@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, version 2 of the
13 * License.
14 *
15 * File: ima_main.c
16 * implements the IMA hooks: ima_bprm_check, ima_file_mmap,
17 * and ima_file_check.
18 */
19
20 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21
22 #include <linux/module.h>
23 #include <linux/file.h>
24 #include <linux/binfmts.h>
25 #include <linux/mount.h>
26 #include <linux/mman.h>
27 #include <linux/slab.h>
28 #include <linux/xattr.h>
29 #include <linux/ima.h>
30
31 #include "ima.h"
32
33 int ima_initialized;
34
35 #ifdef CONFIG_IMA_APPRAISE
36 int ima_appraise = IMA_APPRAISE_ENFORCE;
37 #else
38 int ima_appraise;
39 #endif
40
41 int ima_hash_algo = HASH_ALGO_SHA1;
42 static int hash_setup_done;
43
hash_setup(char * str)44 static int __init hash_setup(char *str)
45 {
46 struct ima_template_desc *template_desc = ima_template_desc_current();
47 int i;
48
49 if (hash_setup_done)
50 return 1;
51
52 if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
53 if (strncmp(str, "sha1", 4) == 0)
54 ima_hash_algo = HASH_ALGO_SHA1;
55 else if (strncmp(str, "md5", 3) == 0)
56 ima_hash_algo = HASH_ALGO_MD5;
57 else
58 return 1;
59 goto out;
60 }
61
62 for (i = 0; i < HASH_ALGO__LAST; i++) {
63 if (strcmp(str, hash_algo_name[i]) == 0) {
64 ima_hash_algo = i;
65 break;
66 }
67 }
68 if (i == HASH_ALGO__LAST)
69 return 1;
70 out:
71 hash_setup_done = 1;
72 return 1;
73 }
74 __setup("ima_hash=", hash_setup);
75
76 /*
77 * ima_rdwr_violation_check
78 *
79 * Only invalidate the PCR for measured files:
80 * - Opening a file for write when already open for read,
81 * results in a time of measure, time of use (ToMToU) error.
82 * - Opening a file for read when already open for write,
83 * could result in a file measurement error.
84 *
85 */
ima_rdwr_violation_check(struct file * file,struct integrity_iint_cache * iint,int must_measure,char ** pathbuf,const char ** pathname)86 static void ima_rdwr_violation_check(struct file *file,
87 struct integrity_iint_cache *iint,
88 int must_measure,
89 char **pathbuf,
90 const char **pathname)
91 {
92 struct inode *inode = file_inode(file);
93 char filename[NAME_MAX];
94 fmode_t mode = file->f_mode;
95 bool send_tomtou = false, send_writers = false;
96
97 if (mode & FMODE_WRITE) {
98 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
99 if (!iint)
100 iint = integrity_iint_find(inode);
101 /* IMA_MEASURE is set from reader side */
102 if (iint && test_bit(IMA_MUST_MEASURE,
103 &iint->atomic_flags))
104 send_tomtou = true;
105 }
106 } else {
107 if (must_measure)
108 set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
109 if ((atomic_read(&inode->i_writecount) > 0) && must_measure)
110 send_writers = true;
111 }
112
113 if (!send_tomtou && !send_writers)
114 return;
115
116 *pathname = ima_d_path(&file->f_path, pathbuf, filename);
117
118 if (send_tomtou)
119 ima_add_violation(file, *pathname, iint,
120 "invalid_pcr", "ToMToU");
121 if (send_writers)
122 ima_add_violation(file, *pathname, iint,
123 "invalid_pcr", "open_writers");
124 }
125
ima_check_last_writer(struct integrity_iint_cache * iint,struct inode * inode,struct file * file)126 static void ima_check_last_writer(struct integrity_iint_cache *iint,
127 struct inode *inode, struct file *file)
128 {
129 fmode_t mode = file->f_mode;
130 bool update;
131
132 if (!(mode & FMODE_WRITE))
133 return;
134
135 mutex_lock(&iint->mutex);
136 if (atomic_read(&inode->i_writecount) == 1) {
137 update = test_and_clear_bit(IMA_UPDATE_XATTR,
138 &iint->atomic_flags);
139 if ((iint->version != inode->i_version) ||
140 (iint->flags & IMA_NEW_FILE)) {
141 iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
142 iint->measured_pcrs = 0;
143 if (update)
144 ima_update_xattr(iint, file);
145 }
146 }
147 mutex_unlock(&iint->mutex);
148 }
149
150 /**
151 * ima_file_free - called on __fput()
152 * @file: pointer to file structure being freed
153 *
154 * Flag files that changed, based on i_version
155 */
ima_file_free(struct file * file)156 void ima_file_free(struct file *file)
157 {
158 struct inode *inode = file_inode(file);
159 struct integrity_iint_cache *iint;
160
161 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
162 return;
163
164 iint = integrity_iint_find(inode);
165 if (!iint)
166 return;
167
168 ima_check_last_writer(iint, inode, file);
169 }
170
process_measurement(struct file * file,char * buf,loff_t size,int mask,enum ima_hooks func,int opened)171 static int process_measurement(struct file *file, char *buf, loff_t size,
172 int mask, enum ima_hooks func, int opened)
173 {
174 struct inode *inode = file_inode(file);
175 struct integrity_iint_cache *iint = NULL;
176 struct ima_template_desc *template_desc;
177 char *pathbuf = NULL;
178 char filename[NAME_MAX];
179 const char *pathname = NULL;
180 int rc = 0, action, must_appraise = 0;
181 int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
182 struct evm_ima_xattr_data *xattr_value = NULL;
183 int xattr_len = 0;
184 bool violation_check;
185 enum hash_algo hash_algo;
186
187 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
188 return 0;
189
190 /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
191 * bitmask based on the appraise/audit/measurement policy.
192 * Included is the appraise submask.
193 */
194 action = ima_get_action(inode, mask, func, &pcr);
195 violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
196 (ima_policy_flag & IMA_MEASURE));
197 if (!action && !violation_check)
198 return 0;
199
200 must_appraise = action & IMA_APPRAISE;
201
202 /* Is the appraise rule hook specific? */
203 if (action & IMA_FILE_APPRAISE)
204 func = FILE_CHECK;
205
206 inode_lock(inode);
207
208 if (action) {
209 iint = integrity_inode_get(inode);
210 if (!iint)
211 rc = -ENOMEM;
212 }
213
214 if (!rc && violation_check)
215 ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
216 &pathbuf, &pathname);
217
218 inode_unlock(inode);
219
220 if (rc)
221 goto out;
222 if (!action)
223 goto out;
224
225 mutex_lock(&iint->mutex);
226
227 if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags))
228 /* reset appraisal flags if ima_inode_post_setattr was called */
229 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
230 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
231 IMA_ACTION_FLAGS);
232
233 if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags))
234 /* reset all flags if ima_inode_setxattr was called */
235 iint->flags &= ~IMA_DONE_MASK;
236
237 /* Determine if already appraised/measured based on bitmask
238 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
239 * IMA_AUDIT, IMA_AUDITED)
240 */
241 iint->flags |= action;
242 action &= IMA_DO_MASK;
243 action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);
244
245 /* If target pcr is already measured, unset IMA_MEASURE action */
246 if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
247 action ^= IMA_MEASURE;
248
249 /* Nothing to do, just return existing appraised status */
250 if (!action) {
251 if (must_appraise)
252 rc = ima_get_cache_status(iint, func);
253 goto out_locked;
254 }
255
256 template_desc = ima_template_desc_current();
257 if ((action & IMA_APPRAISE_SUBMASK) ||
258 strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
259 /* read 'security.ima' */
260 xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
261
262 hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
263
264 rc = ima_collect_measurement(iint, file, buf, size, hash_algo);
265 if (rc != 0 && rc != -EBADF && rc != -EINVAL)
266 goto out_locked;
267
268 if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
269 pathname = ima_d_path(&file->f_path, &pathbuf, filename);
270
271 if (action & IMA_MEASURE)
272 ima_store_measurement(iint, file, pathname,
273 xattr_value, xattr_len, pcr);
274 if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
275 inode_lock(inode);
276 rc = ima_appraise_measurement(func, iint, file, pathname,
277 xattr_value, xattr_len, opened);
278 inode_unlock(inode);
279 }
280 if (action & IMA_AUDIT)
281 ima_audit_measurement(iint, pathname);
282
283 if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
284 rc = 0;
285 out_locked:
286 if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
287 !(iint->flags & IMA_NEW_FILE))
288 rc = -EACCES;
289 mutex_unlock(&iint->mutex);
290 kfree(xattr_value);
291 out:
292 if (pathbuf)
293 __putname(pathbuf);
294 if (must_appraise) {
295 if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
296 return -EACCES;
297 if (file->f_mode & FMODE_WRITE)
298 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
299 }
300 return 0;
301 }
302
303 /**
304 * ima_file_mmap - based on policy, collect/store measurement.
305 * @file: pointer to the file to be measured (May be NULL)
306 * @prot: contains the protection that will be applied by the kernel.
307 *
308 * Measure files being mmapped executable based on the ima_must_measure()
309 * policy decision.
310 *
311 * On success return 0. On integrity appraisal error, assuming the file
312 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
313 */
ima_file_mmap(struct file * file,unsigned long prot)314 int ima_file_mmap(struct file *file, unsigned long prot)
315 {
316 if (file && (prot & PROT_EXEC))
317 return process_measurement(file, NULL, 0, MAY_EXEC,
318 MMAP_CHECK, 0);
319 return 0;
320 }
321
322 /**
323 * ima_bprm_check - based on policy, collect/store measurement.
324 * @bprm: contains the linux_binprm structure
325 *
326 * The OS protects against an executable file, already open for write,
327 * from being executed in deny_write_access() and an executable file,
328 * already open for execute, from being modified in get_write_access().
329 * So we can be certain that what we verify and measure here is actually
330 * what is being executed.
331 *
332 * On success return 0. On integrity appraisal error, assuming the file
333 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
334 */
ima_bprm_check(struct linux_binprm * bprm)335 int ima_bprm_check(struct linux_binprm *bprm)
336 {
337 return process_measurement(bprm->file, NULL, 0, MAY_EXEC,
338 BPRM_CHECK, 0);
339 }
340
341 /**
342 * ima_path_check - based on policy, collect/store measurement.
343 * @file: pointer to the file to be measured
344 * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND
345 *
346 * Measure files based on the ima_must_measure() policy decision.
347 *
348 * On success return 0. On integrity appraisal error, assuming the file
349 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
350 */
ima_file_check(struct file * file,int mask,int opened)351 int ima_file_check(struct file *file, int mask, int opened)
352 {
353 return process_measurement(file, NULL, 0,
354 mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
355 MAY_APPEND), FILE_CHECK, opened);
356 }
357 EXPORT_SYMBOL_GPL(ima_file_check);
358
359 /**
360 * ima_post_path_mknod - mark as a new inode
361 * @dentry: newly created dentry
362 *
363 * Mark files created via the mknodat syscall as new, so that the
364 * file data can be written later.
365 */
ima_post_path_mknod(struct dentry * dentry)366 void ima_post_path_mknod(struct dentry *dentry)
367 {
368 struct integrity_iint_cache *iint;
369 struct inode *inode = dentry->d_inode;
370 int must_appraise;
371
372 must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
373 if (!must_appraise)
374 return;
375
376 iint = integrity_inode_get(inode);
377 if (iint)
378 iint->flags |= IMA_NEW_FILE;
379 }
380
381 /**
382 * ima_read_file - pre-measure/appraise hook decision based on policy
383 * @file: pointer to the file to be measured/appraised/audit
384 * @read_id: caller identifier
385 *
386 * Permit reading a file based on policy. The policy rules are written
387 * in terms of the policy identifier. Appraising the integrity of
388 * a file requires a file descriptor.
389 *
390 * For permission return 0, otherwise return -EACCES.
391 */
ima_read_file(struct file * file,enum kernel_read_file_id read_id)392 int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
393 {
394 if (!file && read_id == READING_MODULE) {
395 #ifndef CONFIG_MODULE_SIG_FORCE
396 if ((ima_appraise & IMA_APPRAISE_MODULES) &&
397 (ima_appraise & IMA_APPRAISE_ENFORCE))
398 return -EACCES; /* INTEGRITY_UNKNOWN */
399 #endif
400 return 0; /* We rely on module signature checking */
401 }
402 return 0;
403 }
404
405 static int read_idmap[READING_MAX_ID] = {
406 [READING_FIRMWARE] = FIRMWARE_CHECK,
407 [READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK,
408 [READING_MODULE] = MODULE_CHECK,
409 [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
410 [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
411 [READING_POLICY] = POLICY_CHECK
412 };
413
414 /**
415 * ima_post_read_file - in memory collect/appraise/audit measurement
416 * @file: pointer to the file to be measured/appraised/audit
417 * @buf: pointer to in memory file contents
418 * @size: size of in memory file contents
419 * @read_id: caller identifier
420 *
421 * Measure/appraise/audit in memory file based on policy. Policy rules
422 * are written in terms of a policy identifier.
423 *
424 * On success return 0. On integrity appraisal error, assuming the file
425 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
426 */
ima_post_read_file(struct file * file,void * buf,loff_t size,enum kernel_read_file_id read_id)427 int ima_post_read_file(struct file *file, void *buf, loff_t size,
428 enum kernel_read_file_id read_id)
429 {
430 enum ima_hooks func;
431
432 if (!file && read_id == READING_FIRMWARE) {
433 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
434 (ima_appraise & IMA_APPRAISE_ENFORCE))
435 return -EACCES; /* INTEGRITY_UNKNOWN */
436 return 0;
437 }
438
439 if (!file && read_id == READING_MODULE) /* MODULE_SIG_FORCE enabled */
440 return 0;
441
442 if (!file || !buf || size == 0) { /* should never happen */
443 if (ima_appraise & IMA_APPRAISE_ENFORCE)
444 return -EACCES;
445 return 0;
446 }
447
448 func = read_idmap[read_id] ?: FILE_CHECK;
449 return process_measurement(file, buf, size, MAY_READ, func, 0);
450 }
451
init_ima(void)452 static int __init init_ima(void)
453 {
454 int error;
455
456 ima_init_template_list();
457 hash_setup(CONFIG_IMA_DEFAULT_HASH);
458 error = ima_init();
459
460 if (error && strcmp(hash_algo_name[ima_hash_algo],
461 CONFIG_IMA_DEFAULT_HASH) != 0) {
462 pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
463 hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
464 hash_setup_done = 0;
465 hash_setup(CONFIG_IMA_DEFAULT_HASH);
466 error = ima_init();
467 }
468
469 if (!error) {
470 ima_initialized = 1;
471 ima_update_policy_flag();
472 }
473 return error;
474 }
475
476 late_initcall(init_ima); /* Start IMA after the TPM is available */
477
478 MODULE_DESCRIPTION("Integrity Measurement Architecture");
479 MODULE_LICENSE("GPL");
480