Commit | Line | Data |
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b4d0d230 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
08815b62 DH |
2 | /* Validate the trust chain of a PKCS#7 message. |
3 | * | |
4 | * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. | |
5 | * Written by David Howells (dhowells@redhat.com) | |
08815b62 DH |
6 | */ |
7 | ||
8 | #define pr_fmt(fmt) "PKCS7: "fmt | |
9 | #include <linux/kernel.h> | |
10 | #include <linux/export.h> | |
11 | #include <linux/slab.h> | |
12 | #include <linux/err.h> | |
13 | #include <linux/asn1.h> | |
14 | #include <linux/key.h> | |
15 | #include <keys/asymmetric-type.h> | |
db6c43bd | 16 | #include <crypto/public_key.h> |
08815b62 DH |
17 | #include "pkcs7_parser.h" |
18 | ||
d13fc874 | 19 | /* |
08815b62 DH |
20 | * Check the trust on one PKCS#7 SignedInfo block. |
21 | */ | |
15155b9a DH |
22 | static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, |
23 | struct pkcs7_signed_info *sinfo, | |
24 | struct key *trust_keyring) | |
08815b62 | 25 | { |
566a117a | 26 | struct public_key_signature *sig = sinfo->sig; |
08815b62 DH |
27 | struct x509_certificate *x509, *last = NULL, *p; |
28 | struct key *key; | |
08815b62 DH |
29 | int ret; |
30 | ||
31 | kenter(",%u,", sinfo->index); | |
32 | ||
41559420 DH |
33 | if (sinfo->unsupported_crypto) { |
34 | kleave(" = -ENOPKG [cached]"); | |
35 | return -ENOPKG; | |
36 | } | |
37 | ||
08815b62 DH |
38 | for (x509 = sinfo->signer; x509; x509 = x509->signer) { |
39 | if (x509->seen) { | |
bda850cd | 40 | if (x509->verified) |
08815b62 | 41 | goto verified; |
08815b62 DH |
42 | kleave(" = -ENOKEY [cached]"); |
43 | return -ENOKEY; | |
44 | } | |
45 | x509->seen = true; | |
46 | ||
47 | /* Look to see if this certificate is present in the trusted | |
48 | * keys. | |
49 | */ | |
9eb02989 | 50 | key = find_asymmetric_key(trust_keyring, |
7d30198e | 51 | x509->id, x509->skid, NULL, false); |
757932e6 | 52 | if (!IS_ERR(key)) { |
08815b62 DH |
53 | /* One of the X.509 certificates in the PKCS#7 message |
54 | * is apparently the same as one we already trust. | |
55 | * Verify that the trusted variant can also validate | |
56 | * the signature on the descendant. | |
57 | */ | |
757932e6 DH |
58 | pr_devel("sinfo %u: Cert %u as key %x\n", |
59 | sinfo->index, x509->index, key_serial(key)); | |
08815b62 | 60 | goto matched; |
757932e6 | 61 | } |
08815b62 DH |
62 | if (key == ERR_PTR(-ENOMEM)) |
63 | return -ENOMEM; | |
64 | ||
65 | /* Self-signed certificates form roots of their own, and if we | |
66 | * don't know them, then we can't accept them. | |
67 | */ | |
7204eb85 | 68 | if (x509->signer == x509) { |
08815b62 DH |
69 | kleave(" = -ENOKEY [unknown self-signed]"); |
70 | return -ENOKEY; | |
71 | } | |
72 | ||
73 | might_sleep(); | |
74 | last = x509; | |
77d0910d | 75 | sig = last->sig; |
08815b62 DH |
76 | } |
77 | ||
78 | /* No match - see if the root certificate has a signer amongst the | |
79 | * trusted keys. | |
80 | */ | |
77d0910d | 81 | if (last && (last->sig->auth_ids[0] || last->sig->auth_ids[1])) { |
9eb02989 DH |
82 | key = find_asymmetric_key(trust_keyring, |
83 | last->sig->auth_ids[0], | |
84 | last->sig->auth_ids[1], | |
7d30198e | 85 | NULL, false); |
757932e6 DH |
86 | if (!IS_ERR(key)) { |
87 | x509 = last; | |
88 | pr_devel("sinfo %u: Root cert %u signer is key %x\n", | |
89 | sinfo->index, x509->index, key_serial(key)); | |
90 | goto matched; | |
91 | } | |
92 | if (PTR_ERR(key) != -ENOKEY) | |
93 | return PTR_ERR(key); | |
08815b62 DH |
94 | } |
95 | ||
757932e6 DH |
96 | /* As a last resort, see if we have a trusted public key that matches |
97 | * the signed info directly. | |
98 | */ | |
9eb02989 | 99 | key = find_asymmetric_key(trust_keyring, |
7d30198e | 100 | sinfo->sig->auth_ids[0], NULL, NULL, false); |
757932e6 DH |
101 | if (!IS_ERR(key)) { |
102 | pr_devel("sinfo %u: Direct signer is key %x\n", | |
103 | sinfo->index, key_serial(key)); | |
104 | x509 = NULL; | |
6459ae38 | 105 | sig = sinfo->sig; |
757932e6 DH |
106 | goto matched; |
107 | } | |
108 | if (PTR_ERR(key) != -ENOKEY) | |
109 | return PTR_ERR(key); | |
110 | ||
111 | kleave(" = -ENOKEY [no backref]"); | |
112 | return -ENOKEY; | |
08815b62 DH |
113 | |
114 | matched: | |
115 | ret = verify_signature(key, sig); | |
08815b62 DH |
116 | key_put(key); |
117 | if (ret < 0) { | |
118 | if (ret == -ENOMEM) | |
119 | return ret; | |
120 | kleave(" = -EKEYREJECTED [verify %d]", ret); | |
121 | return -EKEYREJECTED; | |
122 | } | |
123 | ||
124 | verified: | |
757932e6 DH |
125 | if (x509) { |
126 | x509->verified = true; | |
bda850cd | 127 | for (p = sinfo->signer; p != x509; p = p->signer) |
757932e6 | 128 | p->verified = true; |
08815b62 | 129 | } |
08815b62 DH |
130 | kleave(" = 0"); |
131 | return 0; | |
132 | } | |
133 | ||
134 | /** | |
135 | * pkcs7_validate_trust - Validate PKCS#7 trust chain | |
136 | * @pkcs7: The PKCS#7 certificate to validate | |
137 | * @trust_keyring: Signing certificates to use as starting points | |
08815b62 DH |
138 | * |
139 | * Validate that the certificate chain inside the PKCS#7 message intersects | |
140 | * keys we already know and trust. | |
141 | * | |
142 | * Returns, in order of descending priority: | |
143 | * | |
144 | * (*) -EKEYREJECTED if a signature failed to match for which we have a valid | |
145 | * key, or: | |
146 | * | |
147 | * (*) 0 if at least one signature chain intersects with the keys in the trust | |
148 | * keyring, or: | |
149 | * | |
150 | * (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a | |
151 | * chain. | |
152 | * | |
153 | * (*) -ENOKEY if we couldn't find a match for any of the signature chains in | |
154 | * the message. | |
155 | * | |
156 | * May also return -ENOMEM. | |
157 | */ | |
158 | int pkcs7_validate_trust(struct pkcs7_message *pkcs7, | |
bda850cd | 159 | struct key *trust_keyring) |
08815b62 DH |
160 | { |
161 | struct pkcs7_signed_info *sinfo; | |
162 | struct x509_certificate *p; | |
41559420 DH |
163 | int cached_ret = -ENOKEY; |
164 | int ret; | |
08815b62 DH |
165 | |
166 | for (p = pkcs7->certs; p; p = p->next) | |
167 | p->seen = false; | |
168 | ||
169 | for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { | |
170 | ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring); | |
41559420 DH |
171 | switch (ret) { |
172 | case -ENOKEY: | |
173 | continue; | |
174 | case -ENOPKG: | |
175 | if (cached_ret == -ENOKEY) | |
08815b62 | 176 | cached_ret = -ENOPKG; |
41559420 DH |
177 | continue; |
178 | case 0: | |
41559420 DH |
179 | cached_ret = 0; |
180 | continue; | |
181 | default: | |
182 | return ret; | |
08815b62 | 183 | } |
08815b62 DH |
184 | } |
185 | ||
186 | return cached_ret; | |
187 | } | |
188 | EXPORT_SYMBOL_GPL(pkcs7_validate_trust); |