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 if (strncmp(str, "off", 3) == 0)
24 ima_appraise = 0;
25 else if (strncmp(str, "fix", 3) == 0)
26 ima_appraise = IMA_APPRAISE_FIX;
27 return 1;
28 }
29
30 __setup("ima_appraise=", default_appraise_setup);
31
32 /*
33 * ima_must_appraise - set appraise flag
34 *
35 * Return 1 to appraise
36 */
ima_must_appraise(struct inode * inode,int mask,enum ima_hooks func)37 int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
38 {
39 if (!ima_appraise)
40 return 0;
41
42 return ima_match_policy(inode, func, mask, IMA_APPRAISE);
43 }
44
ima_fix_xattr(struct dentry * dentry,struct integrity_iint_cache * iint)45 static int ima_fix_xattr(struct dentry *dentry,
46 struct integrity_iint_cache *iint)
47 {
48 iint->ima_xattr.type = IMA_XATTR_DIGEST;
49 return __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
50 (u8 *)&iint->ima_xattr,
51 sizeof(iint->ima_xattr), 0);
52 }
53
54 /* Return specific func appraised cached result */
ima_get_cache_status(struct integrity_iint_cache * iint,int func)55 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
56 int func)
57 {
58 switch(func) {
59 case MMAP_CHECK:
60 return iint->ima_mmap_status;
61 case BPRM_CHECK:
62 return iint->ima_bprm_status;
63 case MODULE_CHECK:
64 return iint->ima_module_status;
65 case FILE_CHECK:
66 default:
67 return iint->ima_file_status;
68 }
69 }
70
ima_set_cache_status(struct integrity_iint_cache * iint,int func,enum integrity_status status)71 static void ima_set_cache_status(struct integrity_iint_cache *iint,
72 int func, enum integrity_status status)
73 {
74 switch(func) {
75 case MMAP_CHECK:
76 iint->ima_mmap_status = status;
77 break;
78 case BPRM_CHECK:
79 iint->ima_bprm_status = status;
80 break;
81 case MODULE_CHECK:
82 iint->ima_module_status = status;
83 break;
84 case FILE_CHECK:
85 default:
86 iint->ima_file_status = status;
87 break;
88 }
89 }
90
ima_cache_flags(struct integrity_iint_cache * iint,int func)91 static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
92 {
93 switch(func) {
94 case MMAP_CHECK:
95 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
96 break;
97 case BPRM_CHECK:
98 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
99 break;
100 case MODULE_CHECK:
101 iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED);
102 break;
103 case FILE_CHECK:
104 default:
105 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
106 break;
107 }
108 }
109
110 /*
111 * ima_appraise_measurement - appraise file measurement
112 *
113 * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
114 * Assuming success, compare the xattr hash with the collected measurement.
115 *
116 * Return 0 on success, error code otherwise
117 */
ima_appraise_measurement(int func,struct integrity_iint_cache * iint,struct file * file,const unsigned char * filename)118 int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
119 struct file *file, const unsigned char *filename)
120 {
121 struct dentry *dentry = file->f_dentry;
122 struct inode *inode = dentry->d_inode;
123 struct evm_ima_xattr_data *xattr_value = NULL;
124 enum integrity_status status = INTEGRITY_UNKNOWN;
125 const char *op = "appraise_data";
126 char *cause = "unknown";
127 int rc;
128
129 if (!ima_appraise)
130 return 0;
131 if (!inode->i_op->getxattr)
132 return INTEGRITY_UNKNOWN;
133
134 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)&xattr_value,
135 0, GFP_NOFS);
136 if (rc <= 0) {
137 if (rc && rc != -ENODATA)
138 goto out;
139
140 cause = "missing-hash";
141 status =
142 (inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL;
143 goto out;
144 }
145
146 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
147 if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
148 if ((status == INTEGRITY_NOLABEL)
149 || (status == INTEGRITY_NOXATTRS))
150 cause = "missing-HMAC";
151 else if (status == INTEGRITY_FAIL)
152 cause = "invalid-HMAC";
153 goto out;
154 }
155 switch (xattr_value->type) {
156 case IMA_XATTR_DIGEST:
157 if (iint->flags & IMA_DIGSIG_REQUIRED) {
158 cause = "IMA signature required";
159 status = INTEGRITY_FAIL;
160 break;
161 }
162 rc = memcmp(xattr_value->digest, iint->ima_xattr.digest,
163 IMA_DIGEST_SIZE);
164 if (rc) {
165 cause = "invalid-hash";
166 status = INTEGRITY_FAIL;
167 break;
168 }
169 status = INTEGRITY_PASS;
170 break;
171 case EVM_IMA_XATTR_DIGSIG:
172 iint->flags |= IMA_DIGSIG;
173 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
174 xattr_value->digest, rc - 1,
175 iint->ima_xattr.digest,
176 IMA_DIGEST_SIZE);
177 if (rc == -EOPNOTSUPP) {
178 status = INTEGRITY_UNKNOWN;
179 } else if (rc) {
180 cause = "invalid-signature";
181 status = INTEGRITY_FAIL;
182 } else {
183 status = INTEGRITY_PASS;
184 }
185 break;
186 default:
187 status = INTEGRITY_UNKNOWN;
188 cause = "unknown-ima-data";
189 break;
190 }
191
192 out:
193 if (status != INTEGRITY_PASS) {
194 if ((ima_appraise & IMA_APPRAISE_FIX) &&
195 (!xattr_value ||
196 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
197 if (!ima_fix_xattr(dentry, iint))
198 status = INTEGRITY_PASS;
199 }
200 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
201 op, cause, rc, 0);
202 } else {
203 ima_cache_flags(iint, func);
204 }
205 ima_set_cache_status(iint, func, status);
206 kfree(xattr_value);
207 return status;
208 }
209
210 /*
211 * ima_update_xattr - update 'security.ima' hash value
212 */
ima_update_xattr(struct integrity_iint_cache * iint,struct file * file)213 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
214 {
215 struct dentry *dentry = file->f_dentry;
216 int rc = 0;
217
218 /* do not collect and update hash for digital signatures */
219 if (iint->flags & IMA_DIGSIG)
220 return;
221
222 rc = ima_collect_measurement(iint, file);
223 if (rc < 0)
224 return;
225
226 ima_fix_xattr(dentry, iint);
227 }
228
229 /**
230 * ima_inode_post_setattr - reflect file metadata changes
231 * @dentry: pointer to the affected dentry
232 *
233 * Changes to a dentry's metadata might result in needing to appraise.
234 *
235 * This function is called from notify_change(), which expects the caller
236 * to lock the inode's i_mutex.
237 */
ima_inode_post_setattr(struct dentry * dentry)238 void ima_inode_post_setattr(struct dentry *dentry)
239 {
240 struct inode *inode = dentry->d_inode;
241 struct integrity_iint_cache *iint;
242 int must_appraise, rc;
243
244 if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode)
245 || !inode->i_op->removexattr)
246 return;
247
248 must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
249 iint = integrity_iint_find(inode);
250 if (iint) {
251 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
252 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
253 IMA_ACTION_FLAGS);
254 if (must_appraise)
255 iint->flags |= IMA_APPRAISE;
256 }
257 if (!must_appraise)
258 rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
259 return;
260 }
261
262 /*
263 * ima_protect_xattr - protect 'security.ima'
264 *
265 * Ensure that not just anyone can modify or remove 'security.ima'.
266 */
ima_protect_xattr(struct dentry * dentry,const char * xattr_name,const void * xattr_value,size_t xattr_value_len)267 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
268 const void *xattr_value, size_t xattr_value_len)
269 {
270 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
271 if (!capable(CAP_SYS_ADMIN))
272 return -EPERM;
273 return 1;
274 }
275 return 0;
276 }
277
ima_reset_appraise_flags(struct inode * inode)278 static void ima_reset_appraise_flags(struct inode *inode)
279 {
280 struct integrity_iint_cache *iint;
281
282 if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode))
283 return;
284
285 iint = integrity_iint_find(inode);
286 if (!iint)
287 return;
288
289 iint->flags &= ~IMA_DONE_MASK;
290 return;
291 }
292
ima_inode_setxattr(struct dentry * dentry,const char * xattr_name,const void * xattr_value,size_t xattr_value_len)293 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
294 const void *xattr_value, size_t xattr_value_len)
295 {
296 int result;
297
298 result = ima_protect_xattr(dentry, xattr_name, xattr_value,
299 xattr_value_len);
300 if (result == 1) {
301 ima_reset_appraise_flags(dentry->d_inode);
302 result = 0;
303 }
304 return result;
305 }
306
ima_inode_removexattr(struct dentry * dentry,const char * xattr_name)307 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
308 {
309 int result;
310
311 result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
312 if (result == 1) {
313 ima_reset_appraise_flags(dentry->d_inode);
314 result = 0;
315 }
316 return result;
317 }
318