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