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3323eec9 MZ |
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 | |
e0d5bd2a | 16 | * implements the IMA hooks: ima_bprm_check, ima_file_mmap, |
9bbb6cad | 17 | * and ima_file_check. |
3323eec9 MZ |
18 | */ |
19 | #include <linux/module.h> | |
20 | #include <linux/file.h> | |
21 | #include <linux/binfmts.h> | |
22 | #include <linux/mount.h> | |
23 | #include <linux/mman.h> | |
5a0e3ad6 | 24 | #include <linux/slab.h> |
3323eec9 MZ |
25 | |
26 | #include "ima.h" | |
27 | ||
28 | int ima_initialized; | |
29 | ||
30 | char *ima_hash = "sha1"; | |
31 | static int __init hash_setup(char *str) | |
32 | { | |
07ff7a0b MZ |
33 | if (strncmp(str, "md5", 3) == 0) |
34 | ima_hash = "md5"; | |
3323eec9 MZ |
35 | return 1; |
36 | } | |
37 | __setup("ima_hash=", hash_setup); | |
38 | ||
d1625436 MZ |
39 | struct ima_imbalance { |
40 | struct hlist_node node; | |
41 | unsigned long fsmagic; | |
42 | }; | |
43 | ||
44 | /* | |
45 | * ima_limit_imbalance - emit one imbalance message per filesystem type | |
46 | * | |
47 | * Maintain list of filesystem types that do not measure files properly. | |
48 | * Return false if unknown, true if known. | |
49 | */ | |
50 | static bool ima_limit_imbalance(struct file *file) | |
51 | { | |
52 | static DEFINE_SPINLOCK(ima_imbalance_lock); | |
53 | static HLIST_HEAD(ima_imbalance_list); | |
54 | ||
55 | struct super_block *sb = file->f_dentry->d_sb; | |
56 | struct ima_imbalance *entry; | |
57 | struct hlist_node *node; | |
58 | bool found = false; | |
59 | ||
60 | rcu_read_lock(); | |
61 | hlist_for_each_entry_rcu(entry, node, &ima_imbalance_list, node) { | |
62 | if (entry->fsmagic == sb->s_magic) { | |
63 | found = true; | |
64 | break; | |
65 | } | |
66 | } | |
67 | rcu_read_unlock(); | |
68 | if (found) | |
69 | goto out; | |
70 | ||
71 | entry = kmalloc(sizeof(*entry), GFP_NOFS); | |
72 | if (!entry) | |
73 | goto out; | |
74 | entry->fsmagic = sb->s_magic; | |
75 | spin_lock(&ima_imbalance_lock); | |
76 | /* | |
77 | * we could have raced and something else might have added this fs | |
78 | * to the list, but we don't really care | |
79 | */ | |
80 | hlist_add_head_rcu(&entry->node, &ima_imbalance_list); | |
81 | spin_unlock(&ima_imbalance_lock); | |
82 | printk(KERN_INFO "IMA: unmeasured files on fsmagic: %lX\n", | |
83 | entry->fsmagic); | |
84 | out: | |
85 | return found; | |
86 | } | |
87 | ||
8eb988c7 MZ |
88 | /* ima_read_write_check - reflect possible reading/writing errors in the PCR. |
89 | * | |
90 | * When opening a file for read, if the file is already open for write, | |
91 | * the file could change, resulting in a file measurement error. | |
92 | * | |
93 | * Opening a file for write, if the file is already open for read, results | |
94 | * in a time of measure, time of use (ToMToU) error. | |
95 | * | |
96 | * In either case invalidate the PCR. | |
97 | */ | |
98 | enum iint_pcr_error { TOMTOU, OPEN_WRITERS }; | |
99 | static void ima_read_write_check(enum iint_pcr_error error, | |
100 | struct ima_iint_cache *iint, | |
101 | struct inode *inode, | |
102 | const unsigned char *filename) | |
103 | { | |
104 | switch (error) { | |
105 | case TOMTOU: | |
106 | if (iint->readcount > 0) | |
107 | ima_add_violation(inode, filename, "invalid_pcr", | |
108 | "ToMToU"); | |
109 | break; | |
110 | case OPEN_WRITERS: | |
111 | if (iint->writecount > 0) | |
112 | ima_add_violation(inode, filename, "invalid_pcr", | |
113 | "open_writers"); | |
114 | break; | |
115 | } | |
116 | } | |
117 | ||
e0d5bd2a EP |
118 | /* |
119 | * Update the counts given an fmode_t | |
120 | */ | |
121 | static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode) | |
122 | { | |
123 | BUG_ON(!mutex_is_locked(&iint->mutex)); | |
124 | ||
e0d5bd2a EP |
125 | if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) |
126 | iint->readcount++; | |
127 | if (mode & FMODE_WRITE) | |
128 | iint->writecount++; | |
129 | } | |
130 | ||
8eb988c7 MZ |
131 | /* |
132 | * ima_counts_get - increment file counts | |
133 | * | |
134 | * Maintain read/write counters for all files, but only | |
135 | * invalidate the PCR for measured files: | |
136 | * - Opening a file for write when already open for read, | |
137 | * results in a time of measure, time of use (ToMToU) error. | |
138 | * - Opening a file for read when already open for write, | |
139 | * could result in a file measurement error. | |
140 | * | |
141 | */ | |
142 | void ima_counts_get(struct file *file) | |
143 | { | |
144 | struct dentry *dentry = file->f_path.dentry; | |
145 | struct inode *inode = dentry->d_inode; | |
146 | fmode_t mode = file->f_mode; | |
147 | struct ima_iint_cache *iint; | |
148 | int rc; | |
149 | ||
e950598d | 150 | if (!iint_initialized || !S_ISREG(inode->i_mode)) |
8eb988c7 MZ |
151 | return; |
152 | iint = ima_iint_find_get(inode); | |
153 | if (!iint) | |
154 | return; | |
155 | mutex_lock(&iint->mutex); | |
e950598d MZ |
156 | if (!ima_initialized) |
157 | goto out; | |
1e93d005 | 158 | rc = ima_must_measure(iint, inode, MAY_READ, FILE_CHECK); |
8eb988c7 MZ |
159 | if (rc < 0) |
160 | goto out; | |
161 | ||
162 | if (mode & FMODE_WRITE) { | |
163 | ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name); | |
164 | goto out; | |
165 | } | |
166 | ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name); | |
167 | out: | |
168 | ima_inc_counts(iint, file->f_mode); | |
169 | mutex_unlock(&iint->mutex); | |
170 | ||
171 | kref_put(&iint->refcount, iint_free); | |
172 | } | |
173 | ||
e0d5bd2a EP |
174 | /* |
175 | * Decrement ima counts | |
176 | */ | |
177 | static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode, | |
1429b3ec | 178 | struct file *file) |
e0d5bd2a | 179 | { |
1429b3ec | 180 | mode_t mode = file->f_mode; |
497f3233 EP |
181 | bool dump = false; |
182 | ||
e0d5bd2a EP |
183 | BUG_ON(!mutex_is_locked(&iint->mutex)); |
184 | ||
497f3233 EP |
185 | if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) { |
186 | if (unlikely(iint->readcount == 0)) | |
187 | dump = true; | |
e0d5bd2a | 188 | iint->readcount--; |
497f3233 | 189 | } |
e0d5bd2a | 190 | if (mode & FMODE_WRITE) { |
497f3233 EP |
191 | if (unlikely(iint->writecount == 0)) |
192 | dump = true; | |
e0d5bd2a EP |
193 | iint->writecount--; |
194 | if (iint->writecount == 0) { | |
195 | if (iint->version != inode->i_version) | |
196 | iint->flags &= ~IMA_MEASURED; | |
197 | } | |
198 | } | |
199 | ||
497f3233 EP |
200 | if (dump && !ima_limit_imbalance(file)) { |
201 | printk(KERN_INFO "%s: open/free imbalance (r:%u w:%u)\n", | |
b575156d | 202 | __func__, iint->readcount, iint->writecount); |
e0d5bd2a EP |
203 | dump_stack(); |
204 | } | |
205 | } | |
206 | ||
3323eec9 MZ |
207 | /** |
208 | * ima_file_free - called on __fput() | |
209 | * @file: pointer to file structure being freed | |
210 | * | |
211 | * Flag files that changed, based on i_version; | |
212 | * and decrement the iint readcount/writecount. | |
213 | */ | |
214 | void ima_file_free(struct file *file) | |
215 | { | |
216 | struct inode *inode = file->f_dentry->d_inode; | |
217 | struct ima_iint_cache *iint; | |
218 | ||
e950598d | 219 | if (!iint_initialized || !S_ISREG(inode->i_mode)) |
3323eec9 MZ |
220 | return; |
221 | iint = ima_iint_find_get(inode); | |
222 | if (!iint) | |
223 | return; | |
224 | ||
225 | mutex_lock(&iint->mutex); | |
1429b3ec | 226 | ima_dec_counts(iint, inode, file); |
3323eec9 MZ |
227 | mutex_unlock(&iint->mutex); |
228 | kref_put(&iint->refcount, iint_free); | |
229 | } | |
230 | ||
3323eec9 MZ |
231 | static int process_measurement(struct file *file, const unsigned char *filename, |
232 | int mask, int function) | |
233 | { | |
234 | struct inode *inode = file->f_dentry->d_inode; | |
235 | struct ima_iint_cache *iint; | |
e950598d | 236 | int rc = 0; |
3323eec9 MZ |
237 | |
238 | if (!ima_initialized || !S_ISREG(inode->i_mode)) | |
239 | return 0; | |
9353384e | 240 | iint = ima_iint_find_get(inode); |
3323eec9 MZ |
241 | if (!iint) |
242 | return -ENOMEM; | |
243 | ||
244 | mutex_lock(&iint->mutex); | |
245 | rc = ima_must_measure(iint, inode, mask, function); | |
246 | if (rc != 0) | |
247 | goto out; | |
248 | ||
249 | rc = ima_collect_measurement(iint, file); | |
250 | if (!rc) | |
251 | ima_store_measurement(iint, file, filename); | |
252 | out: | |
253 | mutex_unlock(&iint->mutex); | |
254 | kref_put(&iint->refcount, iint_free); | |
255 | return rc; | |
256 | } | |
257 | ||
258 | /** | |
259 | * ima_file_mmap - based on policy, collect/store measurement. | |
260 | * @file: pointer to the file to be measured (May be NULL) | |
261 | * @prot: contains the protection that will be applied by the kernel. | |
262 | * | |
263 | * Measure files being mmapped executable based on the ima_must_measure() | |
264 | * policy decision. | |
265 | * | |
266 | * Return 0 on success, an error code on failure. | |
267 | * (Based on the results of appraise_measurement().) | |
268 | */ | |
269 | int ima_file_mmap(struct file *file, unsigned long prot) | |
270 | { | |
271 | int rc; | |
272 | ||
273 | if (!file) | |
274 | return 0; | |
275 | if (prot & PROT_EXEC) | |
276 | rc = process_measurement(file, file->f_dentry->d_name.name, | |
277 | MAY_EXEC, FILE_MMAP); | |
278 | return 0; | |
279 | } | |
280 | ||
281 | /** | |
282 | * ima_bprm_check - based on policy, collect/store measurement. | |
283 | * @bprm: contains the linux_binprm structure | |
284 | * | |
285 | * The OS protects against an executable file, already open for write, | |
286 | * from being executed in deny_write_access() and an executable file, | |
287 | * already open for execute, from being modified in get_write_access(). | |
288 | * So we can be certain that what we verify and measure here is actually | |
289 | * what is being executed. | |
290 | * | |
291 | * Return 0 on success, an error code on failure. | |
292 | * (Based on the results of appraise_measurement().) | |
293 | */ | |
294 | int ima_bprm_check(struct linux_binprm *bprm) | |
295 | { | |
296 | int rc; | |
297 | ||
298 | rc = process_measurement(bprm->file, bprm->filename, | |
299 | MAY_EXEC, BPRM_CHECK); | |
300 | return 0; | |
301 | } | |
302 | ||
8eb988c7 MZ |
303 | /** |
304 | * ima_path_check - based on policy, collect/store measurement. | |
305 | * @file: pointer to the file to be measured | |
306 | * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE | |
307 | * | |
308 | * Measure files based on the ima_must_measure() policy decision. | |
309 | * | |
310 | * Always return 0 and audit dentry_open failures. | |
311 | * (Return code will be based upon measurement appraisal.) | |
312 | */ | |
9bbb6cad | 313 | int ima_file_check(struct file *file, int mask) |
8eb988c7 MZ |
314 | { |
315 | int rc; | |
316 | ||
317 | rc = process_measurement(file, file->f_dentry->d_name.name, | |
318 | mask & (MAY_READ | MAY_WRITE | MAY_EXEC), | |
1e93d005 | 319 | FILE_CHECK); |
8eb988c7 MZ |
320 | return 0; |
321 | } | |
9bbb6cad | 322 | EXPORT_SYMBOL_GPL(ima_file_check); |
8eb988c7 | 323 | |
3323eec9 MZ |
324 | static int __init init_ima(void) |
325 | { | |
326 | int error; | |
327 | ||
3323eec9 MZ |
328 | error = ima_init(); |
329 | ima_initialized = 1; | |
330 | return error; | |
331 | } | |
332 | ||
bab73937 MZ |
333 | static void __exit cleanup_ima(void) |
334 | { | |
335 | ima_cleanup(); | |
336 | } | |
337 | ||
3323eec9 MZ |
338 | late_initcall(init_ima); /* Start IMA after the TPM is available */ |
339 | ||
340 | MODULE_DESCRIPTION("Integrity Measurement Architecture"); | |
341 | MODULE_LICENSE("GPL"); |