ima: rename hash calculation functions
[linux-3.10.git] / security / integrity / ima / ima_appraise.c
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
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  */
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
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 */
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
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
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  */
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  */
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  */
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  */
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
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
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
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 }