Commit | Line | Data |
---|---|---|
9f0d3314 DH |
1 | /* Verify the signature on a PKCS#7 message. |
2 | * | |
3 | * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. | |
4 | * Written by David Howells (dhowells@redhat.com) | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU General Public Licence | |
8 | * as published by the Free Software Foundation; either version | |
9 | * 2 of the Licence, or (at your option) any later version. | |
10 | */ | |
11 | ||
12 | #define pr_fmt(fmt) "PKCS7: "fmt | |
13 | #include <linux/kernel.h> | |
14 | #include <linux/export.h> | |
15 | #include <linux/slab.h> | |
16 | #include <linux/err.h> | |
17 | #include <linux/asn1.h> | |
18 | #include <crypto/hash.h> | |
19 | #include "public_key.h" | |
20 | #include "pkcs7_parser.h" | |
21 | ||
22 | /* | |
23 | * Digest the relevant parts of the PKCS#7 data | |
24 | */ | |
25 | static int pkcs7_digest(struct pkcs7_message *pkcs7, | |
26 | struct pkcs7_signed_info *sinfo) | |
27 | { | |
28 | struct crypto_shash *tfm; | |
29 | struct shash_desc *desc; | |
30 | size_t digest_size, desc_size; | |
31 | void *digest; | |
32 | int ret; | |
33 | ||
34 | kenter(",%u,%u", sinfo->index, sinfo->sig.pkey_hash_algo); | |
35 | ||
36 | if (sinfo->sig.pkey_hash_algo >= PKEY_HASH__LAST || | |
37 | !hash_algo_name[sinfo->sig.pkey_hash_algo]) | |
38 | return -ENOPKG; | |
39 | ||
40 | /* Allocate the hashing algorithm we're going to need and find out how | |
41 | * big the hash operational data will be. | |
42 | */ | |
43 | tfm = crypto_alloc_shash(hash_algo_name[sinfo->sig.pkey_hash_algo], | |
44 | 0, 0); | |
45 | if (IS_ERR(tfm)) | |
46 | return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm); | |
47 | ||
48 | desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); | |
49 | sinfo->sig.digest_size = digest_size = crypto_shash_digestsize(tfm); | |
50 | ||
51 | ret = -ENOMEM; | |
52 | digest = kzalloc(digest_size + desc_size, GFP_KERNEL); | |
53 | if (!digest) | |
54 | goto error_no_desc; | |
55 | ||
56 | desc = digest + digest_size; | |
57 | desc->tfm = tfm; | |
58 | desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP; | |
59 | ||
60 | /* Digest the message [RFC2315 9.3] */ | |
61 | ret = crypto_shash_init(desc); | |
62 | if (ret < 0) | |
63 | goto error; | |
64 | ret = crypto_shash_finup(desc, pkcs7->data, pkcs7->data_len, digest); | |
65 | if (ret < 0) | |
66 | goto error; | |
67 | pr_devel("MsgDigest = [%*ph]\n", 8, digest); | |
68 | ||
69 | /* However, if there are authenticated attributes, there must be a | |
70 | * message digest attribute amongst them which corresponds to the | |
71 | * digest we just calculated. | |
72 | */ | |
73 | if (sinfo->msgdigest) { | |
74 | u8 tag; | |
75 | ||
76 | if (sinfo->msgdigest_len != sinfo->sig.digest_size) { | |
77 | pr_debug("Sig %u: Invalid digest size (%u)\n", | |
78 | sinfo->index, sinfo->msgdigest_len); | |
79 | ret = -EBADMSG; | |
80 | goto error; | |
81 | } | |
82 | ||
83 | if (memcmp(digest, sinfo->msgdigest, sinfo->msgdigest_len) != 0) { | |
84 | pr_debug("Sig %u: Message digest doesn't match\n", | |
85 | sinfo->index); | |
86 | ret = -EKEYREJECTED; | |
87 | goto error; | |
88 | } | |
89 | ||
90 | /* We then calculate anew, using the authenticated attributes | |
91 | * as the contents of the digest instead. Note that we need to | |
92 | * convert the attributes from a CONT.0 into a SET before we | |
93 | * hash it. | |
94 | */ | |
95 | memset(digest, 0, sinfo->sig.digest_size); | |
96 | ||
97 | ret = crypto_shash_init(desc); | |
98 | if (ret < 0) | |
99 | goto error; | |
100 | tag = ASN1_CONS_BIT | ASN1_SET; | |
101 | ret = crypto_shash_update(desc, &tag, 1); | |
102 | if (ret < 0) | |
103 | goto error; | |
104 | ret = crypto_shash_finup(desc, sinfo->authattrs, | |
105 | sinfo->authattrs_len, digest); | |
106 | if (ret < 0) | |
107 | goto error; | |
108 | pr_devel("AADigest = [%*ph]\n", 8, digest); | |
109 | } | |
110 | ||
111 | sinfo->sig.digest = digest; | |
112 | digest = NULL; | |
113 | ||
114 | error: | |
115 | kfree(digest); | |
116 | error_no_desc: | |
117 | crypto_free_shash(tfm); | |
118 | kleave(" = %d", ret); | |
119 | return ret; | |
120 | } | |
121 | ||
122 | /* | |
a4730357 DH |
123 | * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7 |
124 | * uses the issuer's name and the issuing certificate serial number for | |
125 | * matching purposes. These must match the certificate issuer's name (not | |
126 | * subject's name) and the certificate serial number [RFC 2315 6.7]. | |
127 | */ | |
128 | static int pkcs7_find_key(struct pkcs7_message *pkcs7, | |
129 | struct pkcs7_signed_info *sinfo) | |
130 | { | |
131 | struct x509_certificate *x509; | |
132 | unsigned certix = 1; | |
133 | ||
134 | kenter("%u,%u,%u", | |
135 | sinfo->index, sinfo->raw_serial_size, sinfo->raw_issuer_size); | |
136 | ||
137 | for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) { | |
138 | /* I'm _assuming_ that the generator of the PKCS#7 message will | |
139 | * encode the fields from the X.509 cert in the same way in the | |
140 | * PKCS#7 message - but I can't be 100% sure of that. It's | |
141 | * possible this will need element-by-element comparison. | |
142 | */ | |
143 | if (x509->raw_serial_size != sinfo->raw_serial_size || | |
144 | memcmp(x509->raw_serial, sinfo->raw_serial, | |
145 | sinfo->raw_serial_size) != 0) | |
146 | continue; | |
147 | pr_devel("Sig %u: Found cert serial match X.509[%u]\n", | |
148 | sinfo->index, certix); | |
149 | ||
150 | if (x509->raw_issuer_size != sinfo->raw_issuer_size || | |
151 | memcmp(x509->raw_issuer, sinfo->raw_issuer, | |
152 | sinfo->raw_issuer_size) != 0) { | |
153 | pr_warn("Sig %u: X.509 subject and PKCS#7 issuer don't match\n", | |
154 | sinfo->index); | |
155 | continue; | |
156 | } | |
157 | ||
158 | if (x509->pub->pkey_algo != sinfo->sig.pkey_algo) { | |
159 | pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n", | |
160 | sinfo->index); | |
161 | continue; | |
162 | } | |
163 | ||
164 | sinfo->signer = x509; | |
165 | return 0; | |
166 | } | |
167 | pr_warn("Sig %u: Issuing X.509 cert not found (#%*ph)\n", | |
168 | sinfo->index, sinfo->raw_serial_size, sinfo->raw_serial); | |
169 | return -ENOKEY; | |
170 | } | |
171 | ||
9f0d3314 DH |
172 | /* |
173 | * Verify one signed information block from a PKCS#7 message. | |
174 | */ | |
175 | static int pkcs7_verify_one(struct pkcs7_message *pkcs7, | |
176 | struct pkcs7_signed_info *sinfo) | |
177 | { | |
178 | int ret; | |
179 | ||
180 | kenter(",%u", sinfo->index); | |
181 | ||
182 | /* First of all, digest the data in the PKCS#7 message and the | |
183 | * signed information block | |
184 | */ | |
185 | ret = pkcs7_digest(pkcs7, sinfo); | |
186 | if (ret < 0) | |
187 | return ret; | |
188 | ||
a4730357 DH |
189 | /* Find the key for the signature */ |
190 | ret = pkcs7_find_key(pkcs7, sinfo); | |
191 | if (ret < 0) | |
192 | return ret; | |
193 | ||
194 | pr_devel("Using X.509[%u] for sig %u\n", | |
195 | sinfo->signer->index, sinfo->index); | |
196 | ||
197 | /* Verify the PKCS#7 binary against the key */ | |
198 | ret = public_key_verify_signature(sinfo->signer->pub, &sinfo->sig); | |
199 | if (ret < 0) | |
200 | return ret; | |
201 | ||
202 | pr_devel("Verified signature %u\n", sinfo->index); | |
203 | ||
9f0d3314 DH |
204 | return 0; |
205 | } | |
206 | ||
207 | /** | |
208 | * pkcs7_verify - Verify a PKCS#7 message | |
209 | * @pkcs7: The PKCS#7 message to be verified | |
210 | */ | |
211 | int pkcs7_verify(struct pkcs7_message *pkcs7) | |
212 | { | |
213 | struct pkcs7_signed_info *sinfo; | |
214 | struct x509_certificate *x509; | |
215 | int ret, n; | |
216 | ||
217 | kenter(""); | |
218 | ||
219 | for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) { | |
220 | ret = x509_get_sig_params(x509); | |
221 | if (ret < 0) | |
222 | return ret; | |
223 | pr_debug("X.509[%u] %s\n", n, x509->authority); | |
224 | } | |
225 | ||
226 | for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { | |
227 | ret = pkcs7_verify_one(pkcs7, sinfo); | |
228 | if (ret < 0) { | |
229 | kleave(" = %d", ret); | |
230 | return ret; | |
231 | } | |
232 | } | |
233 | ||
234 | kleave(" = 0"); | |
235 | return 0; | |
236 | } | |
237 | EXPORT_SYMBOL_GPL(pkcs7_verify); |