aboutsummaryrefslogtreecommitdiff
path: root/security/integrity/ima/ima_api.c
blob: b356884fb3ef9c17dbc3d71396ac01c98e20a400 (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
/*
 * Copyright (C) 2008 IBM Corporation
 *
 * Author: 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_api.c
 *	Implements must_appraise_or_measure, collect_measurement,
 *	appraise_measurement, store_measurement and store_template.
 */
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/evm.h>
#include "ima.h"

static const char *IMA_TEMPLATE_NAME = "ima";

/*
 * ima_store_template - store ima template measurements
 *
 * Calculate the hash of a template entry, add the template entry
 * to an ordered list of measurement entries maintained inside the kernel,
 * and also update the aggregate integrity value (maintained inside the
 * configured TPM PCR) over the hashes of the current list of measurement
 * entries.
 *
 * Applications retrieve the current kernel-held measurement list through
 * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
 * TPM PCR (called quote) can be retrieved using a TPM user space library
 * and is used to validate the measurement list.
 *
 * Returns 0 on success, error code otherwise
 */
int ima_store_template(struct ima_template_entry *entry,
		       int violation, struct inode *inode)
{
	const char *op = "add_template_measure";
	const char *audit_cause = "hashing_error";
	int result;

	memset(entry->digest, 0, sizeof(entry->digest));
	entry->template_name = IMA_TEMPLATE_NAME;
	entry->template_len = sizeof(entry->template);

	if (!violation) {
		result = ima_calc_template_hash(entry->template_len,
						&entry->template,
						entry->digest);
		if (result < 0) {
			integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
					    entry->template_name, op,
					    audit_cause, result, 0);
			return result;
		}
	}
	result = ima_add_template_entry(entry, violation, op, inode);
	return result;
}

/*
 * ima_add_violation - add violation to measurement list.
 *
 * Violations are flagged in the measurement list with zero hash values.
 * By extending the PCR with 0xFF's instead of with zeroes, the PCR
 * value is invalidated.
 */
void ima_add_violation(struct inode *inode, const unsigned char *filename,
		       const char *op, const char *cause)
{
	struct ima_template_entry *entry;
	int violation = 1;
	int result;

	/* can overflow, only indicator */
	atomic_long_inc(&ima_htable.violations);

	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
	if (!entry) {
		result = -ENOMEM;
		goto err_out;
	}
	memset(&entry->template, 0, sizeof(entry->template));
	strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
	result = ima_store_template(entry, violation, inode);
	if (result < 0)
		kfree(entry);
err_out:
	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
			    op, cause, result, 0);
}

/**
 * ima_get_action - appraise & measure decision based on policy.
 * @inode: pointer to inode to measure
 * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
 * @function: calling function (FILE_CHECK, BPRM_CHECK, FILE_MMAP)
 *
 * The policy is defined in terms of keypairs:
 * 		subj=, obj=, type=, func=, mask=, fsmagic=
 *	subj,obj, and type: are LSM specific.
 * 	func: FILE_CHECK | BPRM_CHECK | FILE_MMAP
 * 	mask: contains the permission mask
 *	fsmagic: hex value
 *
 * Returns IMA_MEASURE, IMA_APPRAISE mask.
 *
 */
int ima_get_action(struct inode *inode, int mask, int function)
{
	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;

	if (!ima_appraise)
		flags &= ~IMA_APPRAISE;

	return ima_match_policy(inode, function, mask, flags);
}

int ima_must_measure(struct inode *inode, int mask, int function)
{
	return ima_match_policy(inode, function, mask, IMA_MEASURE);
}

/*
 * ima_collect_measurement - collect file measurement
 *
 * Calculate the file hash, if it doesn't already exist,
 * storing the measurement and i_version in the iint.
 *
 * Must be called with iint->mutex held.
 *
 * Return 0 on success, error code otherwise
 */
int ima_collect_measurement(struct integrity_iint_cache *iint,
			    struct file *file)
{
	struct inode *inode = file->f_dentry->d_inode;
	const char *filename = file->f_dentry->d_name.name;
	int result = 0;

	if (!(iint->flags & IMA_COLLECTED)) {
		u64 i_version = file->f_dentry->d_inode->i_version;

		iint->ima_xattr.type = IMA_XATTR_DIGEST;
		result = ima_calc_hash(file, iint->ima_xattr.digest);
		if (!result) {
			iint->version = i_version;
			iint->flags |= IMA_COLLECTED;
		}
	}
	if (result)
		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
				    filename, "collect_data", "failed",
				    result, 0);
	return result;
}

/*
 * ima_store_measurement - store file measurement
 *
 * Create an "ima" template and then store the template by calling
 * ima_store_template.
 *
 * We only get here if the inode has not already been measured,
 * but the measurement could already exist:
 * 	- multiple copies of the same file on either the same or
 *	  different filesystems.
 *	- the inode was previously flushed as well as the iint info,
 *	  containing the hashing info.
 *
 * Must be called with iint->mutex held.
 */
void ima_store_measurement(struct integrity_iint_cache *iint,
			   struct file *file, const unsigned char *filename)
{
	const char *op = "add_template_measure";
	const char *audit_cause = "ENOMEM";
	int result = -ENOMEM;
	struct inode *inode = file->f_dentry->d_inode;
	struct ima_template_entry *entry;
	int violation = 0;

	if (iint->flags & IMA_MEASURED)
		return;

	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
	if (!entry) {
		integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
				    op, audit_cause, result, 0);
		return;
	}
	memset(&entry->template, 0, sizeof(entry->template));
	memcpy(entry->template.digest, iint->ima_xattr.digest, IMA_DIGEST_SIZE);
	strcpy(entry->template.file_name,
	       (strlen(filename) > IMA_EVENT_NAME_LEN_MAX) ?
	       file->f_dentry->d_name.name : filename);

	result = ima_store_template(entry, violation, inode);
	if (!result || result == -EEXIST)
		iint->flags |= IMA_MEASURED;
	if (result < 0)
		kfree(entry);
}

void ima_audit_measurement(struct integrity_iint_cache *iint,
			   const unsigned char *filename)
{
	struct audit_buffer *ab;
	char hash[(IMA_DIGEST_SIZE * 2) + 1];
	int i;

	if (iint->flags & IMA_AUDITED)
		return;

	for (i = 0; i < IMA_DIGEST_SIZE; i++)
		hex_byte_pack(hash + (i * 2), iint->ima_xattr.digest[i]);
	hash[i * 2] = '\0';

	ab = audit_log_start(current->audit_context, GFP_KERNEL,
			     AUDIT_INTEGRITY_RULE);
	if (!ab)
		return;

	audit_log_format(ab, "file=");
	audit_log_untrustedstring(ab, filename);
	audit_log_format(ab, " hash=");
	audit_log_untrustedstring(ab, hash);

	audit_log_task_info(ab, current);
	audit_log_end(ab);

	iint->flags |= IMA_AUDITED;
}