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
|
// SPDX-License-Identifier: GPL-2.0+
/*
* IMA support for appraising module-style appended signatures.
*
* Copyright (C) 2019 IBM Corporation
*
* Author:
* Thiago Jung Bauermann <bauerman@linux.ibm.com>
*/
#include <linux/types.h>
#include <linux/module_signature.h>
#include <keys/asymmetric-type.h>
#include <crypto/pkcs7.h>
#include "ima.h"
struct modsig {
struct pkcs7_message *pkcs7_msg;
enum hash_algo hash_algo;
/* This digest will go in the 'd-modsig' field of the IMA template. */
const u8 *digest;
u32 digest_size;
/*
* This is what will go to the measurement list if the template requires
* storing the signature.
*/
int raw_pkcs7_len;
u8 raw_pkcs7[] __counted_by(raw_pkcs7_len);
};
/*
* ima_read_modsig - Read modsig from buf.
*
* Return: 0 on success, error code otherwise.
*/
int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
struct modsig **modsig)
{
const size_t marker_len = strlen(MODULE_SIG_STRING);
const struct module_signature *sig;
struct modsig *hdr;
size_t sig_len;
const void *p;
int rc;
if (buf_len <= marker_len + sizeof(*sig))
return -ENOENT;
p = buf + buf_len - marker_len;
if (memcmp(p, MODULE_SIG_STRING, marker_len))
return -ENOENT;
buf_len -= marker_len;
sig = (const struct module_signature *)(p - sizeof(*sig));
rc = mod_check_sig(sig, buf_len, func_tokens[func]);
if (rc)
return rc;
sig_len = be32_to_cpu(sig->sig_len);
buf_len -= sig_len + sizeof(*sig);
/* Allocate sig_len additional bytes to hold the raw PKCS#7 data. */
hdr = kzalloc(struct_size(hdr, raw_pkcs7, sig_len), GFP_KERNEL);
if (!hdr)
return -ENOMEM;
hdr->raw_pkcs7_len = sig_len;
hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len);
if (IS_ERR(hdr->pkcs7_msg)) {
rc = PTR_ERR(hdr->pkcs7_msg);
kfree(hdr);
return rc;
}
memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len);
/* We don't know the hash algorithm yet. */
hdr->hash_algo = HASH_ALGO__LAST;
*modsig = hdr;
return 0;
}
/**
* ima_collect_modsig - Calculate the file hash without the appended signature.
* @modsig: parsed module signature
* @buf: data to verify the signature on
* @size: data size
*
* Since the modsig is part of the file contents, the hash used in its signature
* isn't the same one ordinarily calculated by IMA. Therefore PKCS7 code
* calculates a separate one for signature verification.
*/
void ima_collect_modsig(struct modsig *modsig, const void *buf, loff_t size)
{
int rc;
/*
* Provide the file contents (minus the appended sig) so that the PKCS7
* code can calculate the file hash.
*/
size -= modsig->raw_pkcs7_len + strlen(MODULE_SIG_STRING) +
sizeof(struct module_signature);
rc = pkcs7_supply_detached_data(modsig->pkcs7_msg, buf, size);
if (rc)
return;
/* Ask the PKCS7 code to calculate the file hash. */
rc = pkcs7_get_digest(modsig->pkcs7_msg, &modsig->digest,
&modsig->digest_size, &modsig->hash_algo);
}
int ima_modsig_verify(struct key *keyring, const struct modsig *modsig)
{
return verify_pkcs7_message_sig(NULL, 0, modsig->pkcs7_msg, keyring,
VERIFYING_MODULE_SIGNATURE, NULL, NULL);
}
int ima_get_modsig_digest(const struct modsig *modsig, enum hash_algo *algo,
const u8 **digest, u32 *digest_size)
{
*algo = modsig->hash_algo;
*digest = modsig->digest;
*digest_size = modsig->digest_size;
return 0;
}
int ima_get_raw_modsig(const struct modsig *modsig, const void **data,
u32 *data_len)
{
*data = &modsig->raw_pkcs7;
*data_len = modsig->raw_pkcs7_len;
return 0;
}
void ima_free_modsig(struct modsig *modsig)
{
if (!modsig)
return;
pkcs7_free_message(modsig->pkcs7_msg);
kfree(modsig);
}
|
