1 /*
2 * Copyright (C) 2011 IBM Corporation
3 *
4 * Author:
5 * Mimi Zohar <zohar@us.ibm.com>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, version 2 of the License.
10 */
11 #include <linux/module.h>
12 #include <linux/file.h>
13 #include <linux/fs.h>
14 #include <linux/xattr.h>
15 #include <linux/magic.h>
16 #include <linux/ima.h>
17 #include <linux/evm.h>
18
19 #include "ima.h"
20
default_appraise_setup(char * str)21 static int __init default_appraise_setup(char *str)
22 {
23 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
24 if (strncmp(str, "off", 3) == 0)
25 ima_appraise = 0;
26 else if (strncmp(str, "log", 3) == 0)
27 ima_appraise = IMA_APPRAISE_LOG;
28 else if (strncmp(str, "fix", 3) == 0)
29 ima_appraise = IMA_APPRAISE_FIX;
30 #endif
31 return 1;
32 }
33
34 __setup("ima_appraise=", default_appraise_setup);
35
36 /*
37 * is_ima_appraise_enabled - return appraise status
38 *
39 * Only return enabled, if not in ima_appraise="fix" or "log" modes.
40 */
is_ima_appraise_enabled(void)41 bool is_ima_appraise_enabled(void)
42 {
43 return (ima_appraise & IMA_APPRAISE_ENFORCE) ? 1 : 0;
44 }
45
46 /*
47 * ima_must_appraise - set appraise flag
48 *
49 * Return 1 to appraise
50 */
ima_must_appraise(struct inode * inode,int mask,enum ima_hooks func)51 int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
52 {
53 if (!ima_appraise)
54 return 0;
55
56 return ima_match_policy(inode, func, mask, IMA_APPRAISE, NULL);
57 }
58
ima_fix_xattr(struct dentry * dentry,struct integrity_iint_cache * iint)59 static int ima_fix_xattr(struct dentry *dentry,
60 struct integrity_iint_cache *iint)
61 {
62 int rc, offset;
63 u8 algo = iint->ima_hash->algo;
64
65 if (algo <= HASH_ALGO_SHA1) {
66 offset = 1;
67 iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
68 } else {
69 offset = 0;
70 iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
71 iint->ima_hash->xattr.ng.algo = algo;
72 }
73 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
74 &iint->ima_hash->xattr.data[offset],
75 (sizeof(iint->ima_hash->xattr) - offset) +
76 iint->ima_hash->length, 0);
77 return rc;
78 }
79
80 /* Return specific func appraised cached result */
ima_get_cache_status(struct integrity_iint_cache * iint,enum ima_hooks func)81 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
82 enum ima_hooks func)
83 {
84 switch (func) {
85 case MMAP_CHECK:
86 return iint->ima_mmap_status;
87 case BPRM_CHECK:
88 return iint->ima_bprm_status;
89 case FILE_CHECK:
90 case POST_SETATTR:
91 return iint->ima_file_status;
92 case MODULE_CHECK ... MAX_CHECK - 1:
93 default:
94 return iint->ima_read_status;
95 }
96 }
97
ima_set_cache_status(struct integrity_iint_cache * iint,enum ima_hooks func,enum integrity_status status)98 static void ima_set_cache_status(struct integrity_iint_cache *iint,
99 enum ima_hooks func,
100 enum integrity_status status)
101 {
102 switch (func) {
103 case MMAP_CHECK:
104 iint->ima_mmap_status = status;
105 break;
106 case BPRM_CHECK:
107 iint->ima_bprm_status = status;
108 break;
109 case FILE_CHECK:
110 case POST_SETATTR:
111 iint->ima_file_status = status;
112 break;
113 case MODULE_CHECK ... MAX_CHECK - 1:
114 default:
115 iint->ima_read_status = status;
116 break;
117 }
118 }
119
ima_cache_flags(struct integrity_iint_cache * iint,enum ima_hooks func)120 static void ima_cache_flags(struct integrity_iint_cache *iint,
121 enum ima_hooks func)
122 {
123 switch (func) {
124 case MMAP_CHECK:
125 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
126 break;
127 case BPRM_CHECK:
128 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
129 break;
130 case FILE_CHECK:
131 case POST_SETATTR:
132 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
133 break;
134 case MODULE_CHECK ... MAX_CHECK - 1:
135 default:
136 iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
137 break;
138 }
139 }
140
ima_get_hash_algo(struct evm_ima_xattr_data * xattr_value,int xattr_len)141 enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
142 int xattr_len)
143 {
144 struct signature_v2_hdr *sig;
145 enum hash_algo ret;
146
147 if (!xattr_value || xattr_len < 2)
148 /* return default hash algo */
149 return ima_hash_algo;
150
151 switch (xattr_value->type) {
152 case EVM_IMA_XATTR_DIGSIG:
153 sig = (typeof(sig))xattr_value;
154 if (sig->version != 2 || xattr_len <= sizeof(*sig))
155 return ima_hash_algo;
156 return sig->hash_algo;
157 break;
158 case IMA_XATTR_DIGEST_NG:
159 ret = xattr_value->digest[0];
160 if (ret < HASH_ALGO__LAST)
161 return ret;
162 break;
163 case IMA_XATTR_DIGEST:
164 /* this is for backward compatibility */
165 if (xattr_len == 21) {
166 unsigned int zero = 0;
167 if (!memcmp(&xattr_value->digest[16], &zero, 4))
168 return HASH_ALGO_MD5;
169 else
170 return HASH_ALGO_SHA1;
171 } else if (xattr_len == 17)
172 return HASH_ALGO_MD5;
173 break;
174 }
175
176 /* return default hash algo */
177 return ima_hash_algo;
178 }
179
ima_read_xattr(struct dentry * dentry,struct evm_ima_xattr_data ** xattr_value)180 int ima_read_xattr(struct dentry *dentry,
181 struct evm_ima_xattr_data **xattr_value)
182 {
183 ssize_t ret;
184
185 ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
186 0, GFP_NOFS);
187 if (ret == -EOPNOTSUPP)
188 ret = 0;
189 return ret;
190 }
191
192 /*
193 * ima_appraise_measurement - appraise file measurement
194 *
195 * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
196 * Assuming success, compare the xattr hash with the collected measurement.
197 *
198 * Return 0 on success, error code otherwise
199 */
ima_appraise_measurement(enum ima_hooks func,struct integrity_iint_cache * iint,struct file * file,const unsigned char * filename,struct evm_ima_xattr_data * xattr_value,int xattr_len,int opened)200 int ima_appraise_measurement(enum ima_hooks func,
201 struct integrity_iint_cache *iint,
202 struct file *file, const unsigned char *filename,
203 struct evm_ima_xattr_data *xattr_value,
204 int xattr_len, int opened)
205 {
206 static const char op[] = "appraise_data";
207 char *cause = "unknown";
208 struct dentry *dentry = file_dentry(file);
209 struct inode *inode = d_backing_inode(dentry);
210 enum integrity_status status = INTEGRITY_UNKNOWN;
211 int rc = xattr_len, hash_start = 0;
212
213 if (!(inode->i_opflags & IOP_XATTR))
214 return INTEGRITY_UNKNOWN;
215
216 if (rc <= 0) {
217 if (rc && rc != -ENODATA)
218 goto out;
219
220 cause = iint->flags & IMA_DIGSIG_REQUIRED ?
221 "IMA-signature-required" : "missing-hash";
222 status = INTEGRITY_NOLABEL;
223 if (opened & FILE_CREATED)
224 iint->flags |= IMA_NEW_FILE;
225 if ((iint->flags & IMA_NEW_FILE) &&
226 (!(iint->flags & IMA_DIGSIG_REQUIRED) ||
227 (inode->i_size == 0)))
228 status = INTEGRITY_PASS;
229 goto out;
230 }
231
232 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
233 if ((status != INTEGRITY_PASS) &&
234 (status != INTEGRITY_PASS_IMMUTABLE) &&
235 (status != INTEGRITY_UNKNOWN)) {
236 if ((status == INTEGRITY_NOLABEL)
237 || (status == INTEGRITY_NOXATTRS))
238 cause = "missing-HMAC";
239 else if (status == INTEGRITY_FAIL)
240 cause = "invalid-HMAC";
241 goto out;
242 }
243 switch (xattr_value->type) {
244 case IMA_XATTR_DIGEST_NG:
245 /* first byte contains algorithm id */
246 hash_start = 1;
247 /* fall through */
248 case IMA_XATTR_DIGEST:
249 if (iint->flags & IMA_DIGSIG_REQUIRED) {
250 cause = "IMA-signature-required";
251 status = INTEGRITY_FAIL;
252 break;
253 }
254 clear_bit(IMA_DIGSIG, &iint->atomic_flags);
255 if (xattr_len - sizeof(xattr_value->type) - hash_start >=
256 iint->ima_hash->length)
257 /* xattr length may be longer. md5 hash in previous
258 version occupied 20 bytes in xattr, instead of 16
259 */
260 rc = memcmp(&xattr_value->digest[hash_start],
261 iint->ima_hash->digest,
262 iint->ima_hash->length);
263 else
264 rc = -EINVAL;
265 if (rc) {
266 cause = "invalid-hash";
267 status = INTEGRITY_FAIL;
268 break;
269 }
270 status = INTEGRITY_PASS;
271 break;
272 case EVM_IMA_XATTR_DIGSIG:
273 set_bit(IMA_DIGSIG, &iint->atomic_flags);
274 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
275 (const char *)xattr_value, rc,
276 iint->ima_hash->digest,
277 iint->ima_hash->length);
278 if (rc == -EOPNOTSUPP) {
279 status = INTEGRITY_UNKNOWN;
280 } else if (rc) {
281 cause = "invalid-signature";
282 status = INTEGRITY_FAIL;
283 } else {
284 status = INTEGRITY_PASS;
285 }
286 break;
287 default:
288 status = INTEGRITY_UNKNOWN;
289 cause = "unknown-ima-data";
290 break;
291 }
292
293 out:
294 if (status != INTEGRITY_PASS) {
295 if ((ima_appraise & IMA_APPRAISE_FIX) &&
296 (!xattr_value ||
297 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
298 if (!ima_fix_xattr(dentry, iint))
299 status = INTEGRITY_PASS;
300 } else if ((inode->i_size == 0) &&
301 (iint->flags & IMA_NEW_FILE) &&
302 (xattr_value &&
303 xattr_value->type == EVM_IMA_XATTR_DIGSIG)) {
304 status = INTEGRITY_PASS;
305 }
306 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
307 op, cause, rc, 0);
308 } else {
309 ima_cache_flags(iint, func);
310 }
311 ima_set_cache_status(iint, func, status);
312 return status;
313 }
314
315 /*
316 * ima_update_xattr - update 'security.ima' hash value
317 */
ima_update_xattr(struct integrity_iint_cache * iint,struct file * file)318 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
319 {
320 struct dentry *dentry = file_dentry(file);
321 int rc = 0;
322
323 /* do not collect and update hash for digital signatures */
324 if (test_bit(IMA_DIGSIG, &iint->atomic_flags))
325 return;
326
327 if (iint->ima_file_status != INTEGRITY_PASS)
328 return;
329
330 rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
331 if (rc < 0)
332 return;
333
334 inode_lock(file_inode(file));
335 ima_fix_xattr(dentry, iint);
336 inode_unlock(file_inode(file));
337 }
338
339 /**
340 * ima_inode_post_setattr - reflect file metadata changes
341 * @dentry: pointer to the affected dentry
342 *
343 * Changes to a dentry's metadata might result in needing to appraise.
344 *
345 * This function is called from notify_change(), which expects the caller
346 * to lock the inode's i_mutex.
347 */
ima_inode_post_setattr(struct dentry * dentry)348 void ima_inode_post_setattr(struct dentry *dentry)
349 {
350 struct inode *inode = d_backing_inode(dentry);
351 struct integrity_iint_cache *iint;
352 int must_appraise;
353
354 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
355 || !(inode->i_opflags & IOP_XATTR))
356 return;
357
358 must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
359 if (!must_appraise)
360 __vfs_removexattr(dentry, XATTR_NAME_IMA);
361 iint = integrity_iint_find(inode);
362 if (iint) {
363 set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags);
364 if (!must_appraise)
365 clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
366 }
367 }
368
369 /*
370 * ima_protect_xattr - protect 'security.ima'
371 *
372 * Ensure that not just anyone can modify or remove 'security.ima'.
373 */
ima_protect_xattr(struct dentry * dentry,const char * xattr_name,const void * xattr_value,size_t xattr_value_len)374 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
375 const void *xattr_value, size_t xattr_value_len)
376 {
377 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
378 if (!capable(CAP_SYS_ADMIN))
379 return -EPERM;
380 return 1;
381 }
382 return 0;
383 }
384
ima_reset_appraise_flags(struct inode * inode,int digsig)385 static void ima_reset_appraise_flags(struct inode *inode, int digsig)
386 {
387 struct integrity_iint_cache *iint;
388
389 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
390 return;
391
392 iint = integrity_iint_find(inode);
393 if (!iint)
394 return;
395 iint->measured_pcrs = 0;
396 set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags);
397 if (digsig)
398 set_bit(IMA_DIGSIG, &iint->atomic_flags);
399 else
400 clear_bit(IMA_DIGSIG, &iint->atomic_flags);
401 }
402
ima_inode_setxattr(struct dentry * dentry,const char * xattr_name,const void * xattr_value,size_t xattr_value_len)403 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
404 const void *xattr_value, size_t xattr_value_len)
405 {
406 const struct evm_ima_xattr_data *xvalue = xattr_value;
407 int result;
408
409 result = ima_protect_xattr(dentry, xattr_name, xattr_value,
410 xattr_value_len);
411 if (result == 1) {
412 if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
413 return -EINVAL;
414 ima_reset_appraise_flags(d_backing_inode(dentry),
415 (xvalue->type == EVM_IMA_XATTR_DIGSIG) ? 1 : 0);
416 result = 0;
417 }
418 return result;
419 }
420
ima_inode_removexattr(struct dentry * dentry,const char * xattr_name)421 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
422 {
423 int result;
424
425 result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
426 if (result == 1) {
427 ima_reset_appraise_flags(d_backing_inode(dentry), 0);
428 result = 0;
429 }
430 return result;
431 }
432