summaryrefslogtreecommitdiff
path: root/security/integrity/ima/ima_main.c
blob: 53cee4c512ce4d39b238b0ba992fa0637cba89b4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
/*
 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
 *
 * Authors:
 * Reiner Sailer <sailer@watson.ibm.com>
 * Serge Hallyn <serue@us.ibm.com>
 * Kylene Hall <kylene@us.ibm.com>
 * Mimi Zohar <zohar@us.ibm.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, version 2 of the
 * License.
 *
 * File: ima_main.c
 *             implements the IMA hooks: ima_bprm_check, ima_file_mmap,
 *             and ima_path_check.
 */
#include <linux/module.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/mount.h>
#include <linux/mman.h>

#include "ima.h"

int ima_initialized;

char *ima_hash = "sha1";
static int __init hash_setup(char *str)
{
	const char *op = "hash_setup";
	const char *hash = "sha1";
	int result = 0;
	int audit_info = 0;

	if (strncmp(str, "md5", 3) == 0) {
		hash = "md5";
		ima_hash = str;
	} else if (strncmp(str, "sha1", 4) != 0) {
		hash = "invalid_hash_type";
		result = 1;
	}
	integrity_audit_msg(AUDIT_INTEGRITY_HASH, NULL, NULL, op, hash,
			    result, audit_info);
	return 1;
}
__setup("ima_hash=", hash_setup);

/**
 * ima_file_free - called on __fput()
 * @file: pointer to file structure being freed
 *
 * Flag files that changed, based on i_version;
 * and decrement the iint readcount/writecount.
 */
void ima_file_free(struct file *file)
{
	struct inode *inode = file->f_dentry->d_inode;
	struct ima_iint_cache *iint;

	if (!ima_initialized || !S_ISREG(inode->i_mode))
		return;
	iint = ima_iint_find_get(inode);
	if (!iint)
		return;

	mutex_lock(&iint->mutex);
	if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
		iint->readcount--;

	if (file->f_mode & FMODE_WRITE) {
		iint->writecount--;
		if (iint->writecount == 0) {
			if (iint->version != inode->i_version)
				iint->flags &= ~IMA_MEASURED;
		}
	}
	mutex_unlock(&iint->mutex);
	kref_put(&iint->refcount, iint_free);
}

/* ima_read_write_check - reflect possible reading/writing errors in the PCR.
 *
 * When opening a file for read, if the file is already open for write,
 * the file could change, resulting in a file measurement error.
 *
 * Opening a file for write, if the file is already open for read, results
 * in a time of measure, time of use (ToMToU) error.
 *
 * In either case invalidate the PCR.
 */
enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
static void ima_read_write_check(enum iint_pcr_error error,
				 struct ima_iint_cache *iint,
				 struct inode *inode,
				 const unsigned char *filename)
{
	switch (error) {
	case TOMTOU:
		if (iint->readcount > 0)
			ima_add_violation(inode, filename, "invalid_pcr",
					  "ToMToU");
		break;
	case OPEN_WRITERS:
		if (iint->writecount > 0)
			ima_add_violation(inode, filename, "invalid_pcr",
					  "open_writers");
		break;
	}
}

static int get_path_measurement(struct ima_iint_cache *iint, struct file *file,
				const unsigned char *filename)
{
	int rc = 0;

	if (IS_ERR(file)) {
		pr_info("%s dentry_open failed\n", filename);
		return rc;
	}
	iint->readcount++;

	rc = ima_collect_measurement(iint, file);
	if (!rc)
		ima_store_measurement(iint, file, filename);
	return rc;
}

/**
 * ima_path_check - based on policy, collect/store measurement.
 * @path: contains a pointer to the path to be measured
 * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 *
 * Measure the file being open for readonly, based on the
 * ima_must_measure() policy decision.
 *
 * Keep read/write counters for all files, but only
 * invalidate the PCR for measured files:
 * 	- Opening a file for write when already open for read,
 *	  results in a time of measure, time of use (ToMToU) error.
 *	- Opening a file for read when already open for write,
 * 	  could result in a file measurement error.
 *
 * Return 0 on success, an error code on failure.
 * (Based on the results of appraise_measurement().)
 */
int ima_path_check(struct path *path, int mask)
{
	struct inode *inode = path->dentry->d_inode;
	struct ima_iint_cache *iint;
	struct file *file = NULL;
	int rc;

	if (!ima_initialized || !S_ISREG(inode->i_mode))
		return 0;
	iint = ima_iint_find_insert_get(inode);
	if (!iint)
		return 0;

	mutex_lock(&iint->mutex);
	if ((mask & MAY_WRITE) || (mask == 0))
		iint->writecount++;
	else if (mask & (MAY_READ | MAY_EXEC))
		iint->readcount++;

	rc = ima_must_measure(iint, inode, MAY_READ, PATH_CHECK);
	if (rc < 0)
		goto out;

	if ((mask & MAY_WRITE) || (mask == 0))
		ima_read_write_check(TOMTOU, iint, inode,
				     path->dentry->d_name.name);

	if ((mask & (MAY_WRITE | MAY_READ | MAY_EXEC)) != MAY_READ)
		goto out;

	ima_read_write_check(OPEN_WRITERS, iint, inode,
			     path->dentry->d_name.name);
	if (!(iint->flags & IMA_MEASURED)) {
		struct dentry *dentry = dget(path->dentry);
		struct vfsmount *mnt = mntget(path->mnt);

		file = dentry_open(dentry, mnt, O_RDONLY, current->cred);
		rc = get_path_measurement(iint, file, dentry->d_name.name);
	}
out:
	mutex_unlock(&iint->mutex);
	if (file)
		fput(file);
	kref_put(&iint->refcount, iint_free);
	return 0;
}

static int process_measurement(struct file *file, const unsigned char *filename,
			       int mask, int function)
{
	struct inode *inode = file->f_dentry->d_inode;
	struct ima_iint_cache *iint;
	int rc;

	if (!ima_initialized || !S_ISREG(inode->i_mode))
		return 0;
	iint = ima_iint_find_insert_get(inode);
	if (!iint)
		return -ENOMEM;

	mutex_lock(&iint->mutex);
	rc = ima_must_measure(iint, inode, mask, function);
	if (rc != 0)
		goto out;

	rc = ima_collect_measurement(iint, file);
	if (!rc)
		ima_store_measurement(iint, file, filename);
out:
	mutex_unlock(&iint->mutex);
	kref_put(&iint->refcount, iint_free);
	return rc;
}

/**
 * ima_file_mmap - based on policy, collect/store measurement.
 * @file: pointer to the file to be measured (May be NULL)
 * @prot: contains the protection that will be applied by the kernel.
 *
 * Measure files being mmapped executable based on the ima_must_measure()
 * policy decision.
 *
 * Return 0 on success, an error code on failure.
 * (Based on the results of appraise_measurement().)
 */
int ima_file_mmap(struct file *file, unsigned long prot)
{
	int rc;

	if (!file)
		return 0;
	if (prot & PROT_EXEC)
		rc = process_measurement(file, file->f_dentry->d_name.name,
					 MAY_EXEC, FILE_MMAP);
	return 0;
}

/**
 * ima_bprm_check - based on policy, collect/store measurement.
 * @bprm: contains the linux_binprm structure
 *
 * The OS protects against an executable file, already open for write,
 * from being executed in deny_write_access() and an executable file,
 * already open for execute, from being modified in get_write_access().
 * So we can be certain that what we verify and measure here is actually
 * what is being executed.
 *
 * Return 0 on success, an error code on failure.
 * (Based on the results of appraise_measurement().)
 */
int ima_bprm_check(struct linux_binprm *bprm)
{
	int rc;

	rc = process_measurement(bprm->file, bprm->filename,
				 MAY_EXEC, BPRM_CHECK);
	return 0;
}

static int __init init_ima(void)
{
	int error;

	ima_iintcache_init();
	error = ima_init();
	ima_initialized = 1;
	return error;
}

late_initcall(init_ima);	/* Start IMA after the TPM is available */

MODULE_DESCRIPTION("Integrity Measurement Architecture");
MODULE_LICENSE("GPL");