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
|
/*
* Copyright (C) 2011 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.
*/
#include <linux/module.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/magic.h>
#include <linux/ima.h>
#include <linux/evm.h>
#include "ima.h"
static int __init default_appraise_setup(char *str)
{
if (strncmp(str, "off", 3) == 0)
ima_appraise = 0;
else if (strncmp(str, "fix", 3) == 0)
ima_appraise = IMA_APPRAISE_FIX;
return 1;
}
__setup("ima_appraise=", default_appraise_setup);
/*
* ima_must_appraise - set appraise flag
*
* Return 1 to appraise
*/
int ima_must_appraise(struct inode *inode, enum ima_hooks func, int mask)
{
return 0;
}
static void ima_fix_xattr(struct dentry *dentry,
struct integrity_iint_cache *iint)
{
iint->digest[0] = IMA_XATTR_DIGEST;
__vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
iint->digest, IMA_DIGEST_SIZE + 1, 0);
}
/*
* ima_appraise_measurement - appraise file measurement
*
* Call evm_verifyxattr() to verify the integrity of 'security.ima'.
* Assuming success, compare the xattr hash with the collected measurement.
*
* Return 0 on success, error code otherwise
*/
int ima_appraise_measurement(struct integrity_iint_cache *iint,
struct file *file, const unsigned char *filename)
{
struct dentry *dentry = file->f_dentry;
struct inode *inode = dentry->d_inode;
u8 xattr_value[IMA_DIGEST_SIZE];
enum integrity_status status = INTEGRITY_UNKNOWN;
const char *op = "appraise_data";
char *cause = "unknown";
int rc;
if (!ima_appraise)
return 0;
if (!inode->i_op->getxattr)
return INTEGRITY_UNKNOWN;
if (iint->flags & IMA_APPRAISED)
return iint->ima_status;
rc = inode->i_op->getxattr(dentry, XATTR_NAME_IMA, xattr_value,
IMA_DIGEST_SIZE);
if (rc <= 0) {
if (rc && rc != -ENODATA)
goto out;
cause = "missing-hash";
status =
(inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL;
goto out;
}
status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) {
if ((status == INTEGRITY_NOLABEL)
|| (status == INTEGRITY_NOXATTRS))
cause = "missing-HMAC";
else if (status == INTEGRITY_FAIL)
cause = "invalid-HMAC";
goto out;
}
rc = memcmp(xattr_value, iint->digest, IMA_DIGEST_SIZE);
if (rc) {
status = INTEGRITY_FAIL;
cause = "invalid-hash";
print_hex_dump_bytes("security.ima: ", DUMP_PREFIX_NONE,
xattr_value, IMA_DIGEST_SIZE);
print_hex_dump_bytes("collected: ", DUMP_PREFIX_NONE,
iint->digest, IMA_DIGEST_SIZE);
goto out;
}
status = INTEGRITY_PASS;
iint->flags |= IMA_APPRAISED;
out:
if (status != INTEGRITY_PASS) {
if (ima_appraise & IMA_APPRAISE_FIX) {
ima_fix_xattr(dentry, iint);
status = INTEGRITY_PASS;
}
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
op, cause, rc, 0);
}
iint->ima_status = status;
return status;
}
/*
* ima_update_xattr - update 'security.ima' hash value
*/
void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
{
struct dentry *dentry = file->f_dentry;
int rc = 0;
rc = ima_collect_measurement(iint, file);
if (rc < 0)
return;
ima_fix_xattr(dentry, iint);
}
/**
* ima_inode_post_setattr - reflect file metadata changes
* @dentry: pointer to the affected dentry
*
* Changes to a dentry's metadata might result in needing to appraise.
*
* This function is called from notify_change(), which expects the caller
* to lock the inode's i_mutex.
*/
void ima_inode_post_setattr(struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
struct integrity_iint_cache *iint;
int must_appraise, rc;
if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode)
|| !inode->i_op->removexattr)
return;
must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
iint = integrity_iint_find(inode);
if (iint) {
if (must_appraise)
iint->flags |= IMA_APPRAISE;
else
iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED);
}
if (!must_appraise)
rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
return;
}
|
