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
16  *	implements the IMA hooks: ima_bprm_check, ima_file_mmap,
17  *	and ima_file_check.
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>
24 #include <linux/slab.h>
25 #include <linux/xattr.h>
26 #include <linux/ima.h>
27 #include <crypto/hash_info.h>
28 
29 #include "ima.h"
30 
31 int ima_initialized;
32 
33 #ifdef CONFIG_IMA_APPRAISE
34 int ima_appraise = IMA_APPRAISE_ENFORCE;
35 #else
36 int ima_appraise;
37 #endif
38 
39 int ima_hash_algo = HASH_ALGO_SHA1;
40 static int hash_setup_done;
41 
42 static int __init hash_setup(char *str)
43 {
44 	struct ima_template_desc *template_desc = ima_template_desc_current();
45 	int i;
46 
47 	if (hash_setup_done)
48 		return 1;
49 
50 	if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
51 		if (strncmp(str, "sha1", 4) == 0)
52 			ima_hash_algo = HASH_ALGO_SHA1;
53 		else if (strncmp(str, "md5", 3) == 0)
54 			ima_hash_algo = HASH_ALGO_MD5;
55 		goto out;
56 	}
57 
58 	for (i = 0; i < HASH_ALGO__LAST; i++) {
59 		if (strcmp(str, hash_algo_name[i]) == 0) {
60 			ima_hash_algo = i;
61 			break;
62 		}
63 	}
64 out:
65 	hash_setup_done = 1;
66 	return 1;
67 }
68 __setup("ima_hash=", hash_setup);
69 
70 /*
71  * ima_rdwr_violation_check
72  *
73  * Only invalidate the PCR for measured files:
74  *	- Opening a file for write when already open for read,
75  *	  results in a time of measure, time of use (ToMToU) error.
76  *	- Opening a file for read when already open for write,
77  *	  could result in a file measurement error.
78  *
79  */
80 static void ima_rdwr_violation_check(struct file *file)
81 {
82 	struct inode *inode = file_inode(file);
83 	fmode_t mode = file->f_mode;
84 	bool send_tomtou = false, send_writers = false;
85 	char *pathbuf = NULL;
86 	const char *pathname;
87 
88 	if (!S_ISREG(inode->i_mode) || !ima_initialized)
89 		return;
90 
91 	mutex_lock(&inode->i_mutex);	/* file metadata: permissions, xattr */
92 
93 	if (mode & FMODE_WRITE) {
94 		if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
95 			struct integrity_iint_cache *iint;
96 			iint = integrity_iint_find(inode);
97 			/* IMA_MEASURE is set from reader side */
98 			if (iint && (iint->flags & IMA_MEASURE))
99 				send_tomtou = true;
100 		}
101 	} else {
102 		if ((atomic_read(&inode->i_writecount) > 0) &&
103 		    ima_must_measure(inode, MAY_READ, FILE_CHECK))
104 			send_writers = true;
105 	}
106 
107 	mutex_unlock(&inode->i_mutex);
108 
109 	if (!send_tomtou && !send_writers)
110 		return;
111 
112 	pathname = ima_d_path(&file->f_path, &pathbuf);
113 
114 	if (send_tomtou)
115 		ima_add_violation(file, pathname, "invalid_pcr", "ToMToU");
116 	if (send_writers)
117 		ima_add_violation(file, pathname,
118 				  "invalid_pcr", "open_writers");
119 	kfree(pathbuf);
120 }
121 
122 static void ima_check_last_writer(struct integrity_iint_cache *iint,
123 				  struct inode *inode, struct file *file)
124 {
125 	fmode_t mode = file->f_mode;
126 
127 	if (!(mode & FMODE_WRITE))
128 		return;
129 
130 	mutex_lock(&inode->i_mutex);
131 	if (atomic_read(&inode->i_writecount) == 1 &&
132 	    iint->version != inode->i_version) {
133 		iint->flags &= ~IMA_DONE_MASK;
134 		if (iint->flags & IMA_APPRAISE)
135 			ima_update_xattr(iint, file);
136 	}
137 	mutex_unlock(&inode->i_mutex);
138 }
139 
140 /**
141  * ima_file_free - called on __fput()
142  * @file: pointer to file structure being freed
143  *
144  * Flag files that changed, based on i_version
145  */
146 void ima_file_free(struct file *file)
147 {
148 	struct inode *inode = file_inode(file);
149 	struct integrity_iint_cache *iint;
150 
151 	if (!iint_initialized || !S_ISREG(inode->i_mode))
152 		return;
153 
154 	iint = integrity_iint_find(inode);
155 	if (!iint)
156 		return;
157 
158 	ima_check_last_writer(iint, inode, file);
159 }
160 
161 static int process_measurement(struct file *file, const char *filename,
162 			       int mask, int function)
163 {
164 	struct inode *inode = file_inode(file);
165 	struct integrity_iint_cache *iint;
166 	struct ima_template_desc *template_desc = ima_template_desc_current();
167 	char *pathbuf = NULL;
168 	const char *pathname = NULL;
169 	int rc = -ENOMEM, action, must_appraise, _func;
170 	struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL;
171 	int xattr_len = 0;
172 
173 	if (!ima_initialized || !S_ISREG(inode->i_mode))
174 		return 0;
175 
176 	/* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
177 	 * bitmask based on the appraise/audit/measurement policy.
178 	 * Included is the appraise submask.
179 	 */
180 	action = ima_get_action(inode, mask, function);
181 	if (!action)
182 		return 0;
183 
184 	must_appraise = action & IMA_APPRAISE;
185 
186 	/*  Is the appraise rule hook specific?  */
187 	_func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function;
188 
189 	mutex_lock(&inode->i_mutex);
190 
191 	iint = integrity_inode_get(inode);
192 	if (!iint)
193 		goto out;
194 
195 	/* Determine if already appraised/measured based on bitmask
196 	 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
197 	 *  IMA_AUDIT, IMA_AUDITED)
198 	 */
199 	iint->flags |= action;
200 	action &= IMA_DO_MASK;
201 	action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
202 
203 	/* Nothing to do, just return existing appraised status */
204 	if (!action) {
205 		if (must_appraise)
206 			rc = ima_get_cache_status(iint, _func);
207 		goto out_digsig;
208 	}
209 
210 	if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
211 		if (action & IMA_APPRAISE_SUBMASK)
212 			xattr_ptr = &xattr_value;
213 	} else
214 		xattr_ptr = &xattr_value;
215 
216 	rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len);
217 	if (rc != 0) {
218 		if (file->f_flags & O_DIRECT)
219 			rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
220 		goto out_digsig;
221 	}
222 
223 	pathname = filename ?: ima_d_path(&file->f_path, &pathbuf);
224 
225 	if (action & IMA_MEASURE)
226 		ima_store_measurement(iint, file, pathname,
227 				      xattr_value, xattr_len);
228 	if (action & IMA_APPRAISE_SUBMASK)
229 		rc = ima_appraise_measurement(_func, iint, file, pathname,
230 					      xattr_value, xattr_len);
231 	if (action & IMA_AUDIT)
232 		ima_audit_measurement(iint, pathname);
233 	kfree(pathbuf);
234 out_digsig:
235 	if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
236 		rc = -EACCES;
237 out:
238 	mutex_unlock(&inode->i_mutex);
239 	kfree(xattr_value);
240 	if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
241 		return -EACCES;
242 	return 0;
243 }
244 
245 /**
246  * ima_file_mmap - based on policy, collect/store measurement.
247  * @file: pointer to the file to be measured (May be NULL)
248  * @prot: contains the protection that will be applied by the kernel.
249  *
250  * Measure files being mmapped executable based on the ima_must_measure()
251  * policy decision.
252  *
253  * On success return 0.  On integrity appraisal error, assuming the file
254  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
255  */
256 int ima_file_mmap(struct file *file, unsigned long prot)
257 {
258 	if (file && (prot & PROT_EXEC))
259 		return process_measurement(file, NULL, MAY_EXEC, MMAP_CHECK);
260 	return 0;
261 }
262 
263 /**
264  * ima_bprm_check - based on policy, collect/store measurement.
265  * @bprm: contains the linux_binprm structure
266  *
267  * The OS protects against an executable file, already open for write,
268  * from being executed in deny_write_access() and an executable file,
269  * already open for execute, from being modified in get_write_access().
270  * So we can be certain that what we verify and measure here is actually
271  * what is being executed.
272  *
273  * On success return 0.  On integrity appraisal error, assuming the file
274  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
275  */
276 int ima_bprm_check(struct linux_binprm *bprm)
277 {
278 	return process_measurement(bprm->file,
279 				   (strcmp(bprm->filename, bprm->interp) == 0) ?
280 				   bprm->filename : bprm->interp,
281 				   MAY_EXEC, BPRM_CHECK);
282 }
283 
284 /**
285  * ima_path_check - based on policy, collect/store measurement.
286  * @file: pointer to the file to be measured
287  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
288  *
289  * Measure files based on the ima_must_measure() policy decision.
290  *
291  * On success return 0.  On integrity appraisal error, assuming the file
292  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
293  */
294 int ima_file_check(struct file *file, int mask)
295 {
296 	ima_rdwr_violation_check(file);
297 	return process_measurement(file, NULL,
298 				   mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
299 				   FILE_CHECK);
300 }
301 EXPORT_SYMBOL_GPL(ima_file_check);
302 
303 /**
304  * ima_module_check - based on policy, collect/store/appraise measurement.
305  * @file: pointer to the file to be measured/appraised
306  *
307  * Measure/appraise kernel modules based on policy.
308  *
309  * On success return 0.  On integrity appraisal error, assuming the file
310  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
311  */
312 int ima_module_check(struct file *file)
313 {
314 	if (!file) {
315 #ifndef CONFIG_MODULE_SIG_FORCE
316 		if ((ima_appraise & IMA_APPRAISE_MODULES) &&
317 		    (ima_appraise & IMA_APPRAISE_ENFORCE))
318 			return -EACCES;	/* INTEGRITY_UNKNOWN */
319 #endif
320 		return 0;	/* We rely on module signature checking */
321 	}
322 	return process_measurement(file, NULL, MAY_EXEC, MODULE_CHECK);
323 }
324 
325 static int __init init_ima(void)
326 {
327 	int error;
328 
329 	hash_setup(CONFIG_IMA_DEFAULT_HASH);
330 	error = ima_init();
331 	if (!error)
332 		ima_initialized = 1;
333 	return error;
334 }
335 
336 late_initcall(init_ima);	/* Start IMA after the TPM is available */
337 
338 MODULE_DESCRIPTION("Integrity Measurement Architecture");
339 MODULE_LICENSE("GPL");
340