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
|
/* Validate the trust chain of a PKCS#7 message.
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#define pr_fmt(fmt) "PKCS7: "fmt
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/asn1.h>
#include <linux/key.h>
#include <keys/asymmetric-type.h>
#include "public_key.h"
#include "pkcs7_parser.h"
/**
* Check the trust on one PKCS#7 SignedInfo block.
*/
static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
struct pkcs7_signed_info *sinfo,
struct key *trust_keyring)
{
struct public_key_signature *sig = &sinfo->sig;
struct x509_certificate *x509, *last = NULL, *p;
struct key *key;
bool trusted;
int ret;
kenter(",%u,", sinfo->index);
if (sinfo->unsupported_crypto) {
kleave(" = -ENOPKG [cached]");
return -ENOPKG;
}
for (x509 = sinfo->signer; x509; x509 = x509->signer) {
if (x509->seen) {
if (x509->verified) {
trusted = x509->trusted;
goto verified;
}
kleave(" = -ENOKEY [cached]");
return -ENOKEY;
}
x509->seen = true;
/* Look to see if this certificate is present in the trusted
* keys.
*/
key = x509_request_asymmetric_key(trust_keyring,
x509->id, x509->skid,
false);
if (!IS_ERR(key)) {
/* One of the X.509 certificates in the PKCS#7 message
* is apparently the same as one we already trust.
* Verify that the trusted variant can also validate
* the signature on the descendant.
*/
pr_devel("sinfo %u: Cert %u as key %x\n",
sinfo->index, x509->index, key_serial(key));
goto matched;
}
if (key == ERR_PTR(-ENOMEM))
return -ENOMEM;
/* Self-signed certificates form roots of their own, and if we
* don't know them, then we can't accept them.
*/
if (x509->next == x509) {
kleave(" = -ENOKEY [unknown self-signed]");
return -ENOKEY;
}
might_sleep();
last = x509;
sig = &last->sig;
}
/* No match - see if the root certificate has a signer amongst the
* trusted keys.
*/
if (last && (last->akid_id || last->akid_skid)) {
key = x509_request_asymmetric_key(trust_keyring,
last->akid_id,
last->akid_skid,
false);
if (!IS_ERR(key)) {
x509 = last;
pr_devel("sinfo %u: Root cert %u signer is key %x\n",
sinfo->index, x509->index, key_serial(key));
goto matched;
}
if (PTR_ERR(key) != -ENOKEY)
return PTR_ERR(key);
}
/* As a last resort, see if we have a trusted public key that matches
* the signed info directly.
*/
key = x509_request_asymmetric_key(trust_keyring,
sinfo->signing_cert_id,
NULL,
false);
if (!IS_ERR(key)) {
pr_devel("sinfo %u: Direct signer is key %x\n",
sinfo->index, key_serial(key));
x509 = NULL;
goto matched;
}
if (PTR_ERR(key) != -ENOKEY)
return PTR_ERR(key);
kleave(" = -ENOKEY [no backref]");
return -ENOKEY;
matched:
ret = verify_signature(key, sig);
trusted = test_bit(KEY_FLAG_TRUSTED, &key->flags);
key_put(key);
if (ret < 0) {
if (ret == -ENOMEM)
return ret;
kleave(" = -EKEYREJECTED [verify %d]", ret);
return -EKEYREJECTED;
}
verified:
if (x509) {
x509->verified = true;
for (p = sinfo->signer; p != x509; p = p->signer) {
p->verified = true;
p->trusted = trusted;
}
}
sinfo->trusted = trusted;
kleave(" = 0");
return 0;
}
/**
* pkcs7_validate_trust - Validate PKCS#7 trust chain
* @pkcs7: The PKCS#7 certificate to validate
* @trust_keyring: Signing certificates to use as starting points
* @_trusted: Set to true if trustworth, false otherwise
*
* Validate that the certificate chain inside the PKCS#7 message intersects
* keys we already know and trust.
*
* Returns, in order of descending priority:
*
* (*) -EKEYREJECTED if a signature failed to match for which we have a valid
* key, or:
*
* (*) 0 if at least one signature chain intersects with the keys in the trust
* keyring, or:
*
* (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
* chain.
*
* (*) -ENOKEY if we couldn't find a match for any of the signature chains in
* the message.
*
* May also return -ENOMEM.
*/
int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
struct key *trust_keyring,
bool *_trusted)
{
struct pkcs7_signed_info *sinfo;
struct x509_certificate *p;
int cached_ret = -ENOKEY;
int ret;
*_trusted = false;
for (p = pkcs7->certs; p; p = p->next)
p->seen = false;
for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring);
switch (ret) {
case -ENOKEY:
continue;
case -ENOPKG:
if (cached_ret == -ENOKEY)
cached_ret = -ENOPKG;
continue;
case 0:
*_trusted |= sinfo->trusted;
cached_ret = 0;
continue;
default:
return ret;
}
}
return cached_ret;
}
EXPORT_SYMBOL_GPL(pkcs7_validate_trust);
|
