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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Instantiate a public key crypto key from an X.509 Certificate
3 *
4 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#define pr_fmt(fmt) "X.509: "fmt
9#include <linux/module.h>
10#include <linux/kernel.h>
11#include <linux/slab.h>
12#include <keys/asymmetric-subtype.h>
13#include <keys/asymmetric-parser.h>
14#include <keys/system_keyring.h>
15#include <crypto/hash.h>
16#include "asymmetric_keys.h"
17#include "x509_parser.h"
18
19/*
20 * Set up the signature parameters in an X.509 certificate. This involves
21 * digesting the signed data and extracting the signature.
22 */
23int x509_get_sig_params(struct x509_certificate *cert)
24{
25 struct public_key_signature *sig = cert->sig;
26 struct crypto_shash *tfm;
27 struct shash_desc *desc;
28 size_t desc_size;
29 int ret;
30
31 pr_devel("==>%s()\n", __func__);
32
33 if (!cert->pub->pkey_algo)
34 cert->unsupported_key = true;
35
36 if (!sig->pkey_algo)
37 cert->unsupported_sig = true;
38
39 /* We check the hash if we can - even if we can't then verify it */
40 if (!sig->hash_algo) {
41 cert->unsupported_sig = true;
42 return 0;
43 }
44
45 sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
46 if (!sig->s)
47 return -ENOMEM;
48
49 sig->s_size = cert->raw_sig_size;
50
51 /* Allocate the hashing algorithm we're going to need and find out how
52 * big the hash operational data will be.
53 */
54 tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
55 if (IS_ERR(tfm)) {
56 if (PTR_ERR(tfm) == -ENOENT) {
57 cert->unsupported_sig = true;
58 return 0;
59 }
60 return PTR_ERR(tfm);
61 }
62
63 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
64 sig->digest_size = crypto_shash_digestsize(tfm);
65
66 ret = -ENOMEM;
67 sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
68 if (!sig->digest)
69 goto error;
70
71 desc = kzalloc(desc_size, GFP_KERNEL);
72 if (!desc)
73 goto error;
74
75 desc->tfm = tfm;
76
77 ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
78 if (ret < 0)
79 goto error_2;
80
81 ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
82 if (ret == -EKEYREJECTED) {
83 pr_err("Cert %*phN is blacklisted\n",
84 sig->digest_size, sig->digest);
85 cert->blacklisted = true;
86 ret = 0;
87 }
88
89error_2:
90 kfree(desc);
91error:
92 crypto_free_shash(tfm);
93 pr_devel("<==%s() = %d\n", __func__, ret);
94 return ret;
95}
96
97/*
98 * Check for self-signedness in an X.509 cert and if found, check the signature
99 * immediately if we can.
100 */
101int x509_check_for_self_signed(struct x509_certificate *cert)
102{
103 int ret = 0;
104
105 pr_devel("==>%s()\n", __func__);
106
107 if (cert->raw_subject_size != cert->raw_issuer_size ||
108 memcmp(cert->raw_subject, cert->raw_issuer,
109 cert->raw_issuer_size) != 0)
110 goto not_self_signed;
111
112 if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
113 /* If the AKID is present it may have one or two parts. If
114 * both are supplied, both must match.
115 */
116 bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
117 bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
118
119 if (!a && !b)
120 goto not_self_signed;
121
122 ret = -EKEYREJECTED;
123 if (((a && !b) || (b && !a)) &&
124 cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
125 goto out;
126 }
127
128 ret = -EKEYREJECTED;
129 if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
130 goto out;
131
132 ret = public_key_verify_signature(cert->pub, cert->sig);
133 if (ret < 0) {
134 if (ret == -ENOPKG) {
135 cert->unsupported_sig = true;
136 ret = 0;
137 }
138 goto out;
139 }
140
141 pr_devel("Cert Self-signature verified");
142 cert->self_signed = true;
143
144out:
145 pr_devel("<==%s() = %d\n", __func__, ret);
146 return ret;
147
148not_self_signed:
149 pr_devel("<==%s() = 0 [not]\n", __func__);
150 return 0;
151}
152
153/*
154 * Attempt to parse a data blob for a key as an X509 certificate.
155 */
156static int x509_key_preparse(struct key_preparsed_payload *prep)
157{
158 struct asymmetric_key_ids *kids;
159 struct x509_certificate *cert;
160 const char *q;
161 size_t srlen, sulen;
162 char *desc = NULL, *p;
163 int ret;
164
165 cert = x509_cert_parse(prep->data, prep->datalen);
166 if (IS_ERR(cert))
167 return PTR_ERR(cert);
168
169 pr_devel("Cert Issuer: %s\n", cert->issuer);
170 pr_devel("Cert Subject: %s\n", cert->subject);
171
172 if (cert->unsupported_key) {
173 ret = -ENOPKG;
174 goto error_free_cert;
175 }
176
177 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
178 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
179
180 cert->pub->id_type = "X509";
181
182 if (cert->unsupported_sig) {
183 public_key_signature_free(cert->sig);
184 cert->sig = NULL;
185 } else {
186 pr_devel("Cert Signature: %s + %s\n",
187 cert->sig->pkey_algo, cert->sig->hash_algo);
188 }
189
190 /* Don't permit addition of blacklisted keys */
191 ret = -EKEYREJECTED;
192 if (cert->blacklisted)
193 goto error_free_cert;
194
195 /* Propose a description */
196 sulen = strlen(cert->subject);
197 if (cert->raw_skid) {
198 srlen = cert->raw_skid_size;
199 q = cert->raw_skid;
200 } else {
201 srlen = cert->raw_serial_size;
202 q = cert->raw_serial;
203 }
204
205 ret = -ENOMEM;
206 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
207 if (!desc)
208 goto error_free_cert;
209 p = memcpy(desc, cert->subject, sulen);
210 p += sulen;
211 *p++ = ':';
212 *p++ = ' ';
213 p = bin2hex(p, q, srlen);
214 *p = 0;
215
216 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
217 if (!kids)
218 goto error_free_desc;
219 kids->id[0] = cert->id;
220 kids->id[1] = cert->skid;
221
222 /* We're pinning the module by being linked against it */
223 __module_get(public_key_subtype.owner);
224 prep->payload.data[asym_subtype] = &public_key_subtype;
225 prep->payload.data[asym_key_ids] = kids;
226 prep->payload.data[asym_crypto] = cert->pub;
227 prep->payload.data[asym_auth] = cert->sig;
228 prep->description = desc;
229 prep->quotalen = 100;
230
231 /* We've finished with the certificate */
232 cert->pub = NULL;
233 cert->id = NULL;
234 cert->skid = NULL;
235 cert->sig = NULL;
236 desc = NULL;
237 ret = 0;
238
239error_free_desc:
240 kfree(desc);
241error_free_cert:
242 x509_free_certificate(cert);
243 return ret;
244}
245
246static struct asymmetric_key_parser x509_key_parser = {
247 .owner = THIS_MODULE,
248 .name = "x509",
249 .parse = x509_key_preparse,
250};
251
252/*
253 * Module stuff
254 */
255static int __init x509_key_init(void)
256{
257 return register_asymmetric_key_parser(&x509_key_parser);
258}
259
260static void __exit x509_key_exit(void)
261{
262 unregister_asymmetric_key_parser(&x509_key_parser);
263}
264
265module_init(x509_key_init);
266module_exit(x509_key_exit);
267
268MODULE_DESCRIPTION("X.509 certificate parser");
269MODULE_AUTHOR("Red Hat, Inc.");
270MODULE_LICENSE("GPL");
1/* Instantiate a public key crypto key from an X.509 Certificate
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) "X.509: "fmt
13#include <linux/module.h>
14#include <linux/kernel.h>
15#include <linux/slab.h>
16#include <keys/asymmetric-subtype.h>
17#include <keys/asymmetric-parser.h>
18#include <keys/system_keyring.h>
19#include <crypto/hash.h>
20#include "asymmetric_keys.h"
21#include "x509_parser.h"
22
23static bool use_builtin_keys;
24static struct asymmetric_key_id *ca_keyid;
25
26#ifndef MODULE
27static struct {
28 struct asymmetric_key_id id;
29 unsigned char data[10];
30} cakey;
31
32static int __init ca_keys_setup(char *str)
33{
34 if (!str) /* default system keyring */
35 return 1;
36
37 if (strncmp(str, "id:", 3) == 0) {
38 struct asymmetric_key_id *p = &cakey.id;
39 size_t hexlen = (strlen(str) - 3) / 2;
40 int ret;
41
42 if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
43 pr_err("Missing or invalid ca_keys id\n");
44 return 1;
45 }
46
47 ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
48 if (ret < 0)
49 pr_err("Unparsable ca_keys id hex string\n");
50 else
51 ca_keyid = p; /* owner key 'id:xxxxxx' */
52 } else if (strcmp(str, "builtin") == 0) {
53 use_builtin_keys = true;
54 }
55
56 return 1;
57}
58__setup("ca_keys=", ca_keys_setup);
59#endif
60
61/**
62 * x509_request_asymmetric_key - Request a key by X.509 certificate params.
63 * @keyring: The keys to search.
64 * @id: The issuer & serialNumber to look for or NULL.
65 * @skid: The subjectKeyIdentifier to look for or NULL.
66 * @partial: Use partial match if true, exact if false.
67 *
68 * Find a key in the given keyring by identifier. The preferred identifier is
69 * the issuer + serialNumber and the fallback identifier is the
70 * subjectKeyIdentifier. If both are given, the lookup is by the former, but
71 * the latter must also match.
72 */
73struct key *x509_request_asymmetric_key(struct key *keyring,
74 const struct asymmetric_key_id *id,
75 const struct asymmetric_key_id *skid,
76 bool partial)
77{
78 struct key *key;
79 key_ref_t ref;
80 const char *lookup;
81 char *req, *p;
82 int len;
83
84 if (id) {
85 lookup = id->data;
86 len = id->len;
87 } else {
88 lookup = skid->data;
89 len = skid->len;
90 }
91
92 /* Construct an identifier "id:<keyid>". */
93 p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
94 if (!req)
95 return ERR_PTR(-ENOMEM);
96
97 if (partial) {
98 *p++ = 'i';
99 *p++ = 'd';
100 } else {
101 *p++ = 'e';
102 *p++ = 'x';
103 }
104 *p++ = ':';
105 p = bin2hex(p, lookup, len);
106 *p = 0;
107
108 pr_debug("Look up: \"%s\"\n", req);
109
110 ref = keyring_search(make_key_ref(keyring, 1),
111 &key_type_asymmetric, req);
112 if (IS_ERR(ref))
113 pr_debug("Request for key '%s' err %ld\n", req, PTR_ERR(ref));
114 kfree(req);
115
116 if (IS_ERR(ref)) {
117 switch (PTR_ERR(ref)) {
118 /* Hide some search errors */
119 case -EACCES:
120 case -ENOTDIR:
121 case -EAGAIN:
122 return ERR_PTR(-ENOKEY);
123 default:
124 return ERR_CAST(ref);
125 }
126 }
127
128 key = key_ref_to_ptr(ref);
129 if (id && skid) {
130 const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
131 if (!kids->id[1]) {
132 pr_debug("issuer+serial match, but expected SKID missing\n");
133 goto reject;
134 }
135 if (!asymmetric_key_id_same(skid, kids->id[1])) {
136 pr_debug("issuer+serial match, but SKID does not\n");
137 goto reject;
138 }
139 }
140
141 pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
142 return key;
143
144reject:
145 key_put(key);
146 return ERR_PTR(-EKEYREJECTED);
147}
148EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);
149
150/*
151 * Set up the signature parameters in an X.509 certificate. This involves
152 * digesting the signed data and extracting the signature.
153 */
154int x509_get_sig_params(struct x509_certificate *cert)
155{
156 struct crypto_shash *tfm;
157 struct shash_desc *desc;
158 size_t digest_size, desc_size;
159 void *digest;
160 int ret;
161
162 pr_devel("==>%s()\n", __func__);
163
164 if (cert->unsupported_crypto)
165 return -ENOPKG;
166 if (cert->sig.s)
167 return 0;
168
169 cert->sig.s = kmemdup(cert->raw_sig, cert->raw_sig_size,
170 GFP_KERNEL);
171 if (!cert->sig.s)
172 return -ENOMEM;
173
174 cert->sig.s_size = cert->raw_sig_size;
175
176 /* Allocate the hashing algorithm we're going to need and find out how
177 * big the hash operational data will be.
178 */
179 tfm = crypto_alloc_shash(cert->sig.hash_algo, 0, 0);
180 if (IS_ERR(tfm)) {
181 if (PTR_ERR(tfm) == -ENOENT) {
182 cert->unsupported_crypto = true;
183 return -ENOPKG;
184 }
185 return PTR_ERR(tfm);
186 }
187
188 desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
189 digest_size = crypto_shash_digestsize(tfm);
190
191 /* We allocate the hash operational data storage on the end of the
192 * digest storage space.
193 */
194 ret = -ENOMEM;
195 digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
196 GFP_KERNEL);
197 if (!digest)
198 goto error;
199
200 cert->sig.digest = digest;
201 cert->sig.digest_size = digest_size;
202
203 desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
204 desc->tfm = tfm;
205 desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
206
207 ret = crypto_shash_init(desc);
208 if (ret < 0)
209 goto error;
210 might_sleep();
211 ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
212error:
213 crypto_free_shash(tfm);
214 pr_devel("<==%s() = %d\n", __func__, ret);
215 return ret;
216}
217EXPORT_SYMBOL_GPL(x509_get_sig_params);
218
219/*
220 * Check the signature on a certificate using the provided public key
221 */
222int x509_check_signature(const struct public_key *pub,
223 struct x509_certificate *cert)
224{
225 int ret;
226
227 pr_devel("==>%s()\n", __func__);
228
229 ret = x509_get_sig_params(cert);
230 if (ret < 0)
231 return ret;
232
233 ret = public_key_verify_signature(pub, &cert->sig);
234 if (ret == -ENOPKG)
235 cert->unsupported_crypto = true;
236 pr_debug("Cert Verification: %d\n", ret);
237 return ret;
238}
239EXPORT_SYMBOL_GPL(x509_check_signature);
240
241/*
242 * Check the new certificate against the ones in the trust keyring. If one of
243 * those is the signing key and validates the new certificate, then mark the
244 * new certificate as being trusted.
245 *
246 * Return 0 if the new certificate was successfully validated, 1 if we couldn't
247 * find a matching parent certificate in the trusted list and an error if there
248 * is a matching certificate but the signature check fails.
249 */
250static int x509_validate_trust(struct x509_certificate *cert,
251 struct key *trust_keyring)
252{
253 struct key *key;
254 int ret = 1;
255
256 if (!trust_keyring)
257 return -EOPNOTSUPP;
258
259 if (ca_keyid && !asymmetric_key_id_partial(cert->akid_skid, ca_keyid))
260 return -EPERM;
261
262 key = x509_request_asymmetric_key(trust_keyring,
263 cert->akid_id, cert->akid_skid,
264 false);
265 if (!IS_ERR(key)) {
266 if (!use_builtin_keys
267 || test_bit(KEY_FLAG_BUILTIN, &key->flags))
268 ret = x509_check_signature(key->payload.data[asym_crypto],
269 cert);
270 key_put(key);
271 }
272 return ret;
273}
274
275/*
276 * Attempt to parse a data blob for a key as an X509 certificate.
277 */
278static int x509_key_preparse(struct key_preparsed_payload *prep)
279{
280 struct asymmetric_key_ids *kids;
281 struct x509_certificate *cert;
282 const char *q;
283 size_t srlen, sulen;
284 char *desc = NULL, *p;
285 int ret;
286
287 cert = x509_cert_parse(prep->data, prep->datalen);
288 if (IS_ERR(cert))
289 return PTR_ERR(cert);
290
291 pr_devel("Cert Issuer: %s\n", cert->issuer);
292 pr_devel("Cert Subject: %s\n", cert->subject);
293
294 if (!cert->pub->pkey_algo ||
295 !cert->sig.pkey_algo ||
296 !cert->sig.hash_algo) {
297 ret = -ENOPKG;
298 goto error_free_cert;
299 }
300
301 pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
302 pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
303 pr_devel("Cert Signature: %s + %s\n",
304 cert->sig.pkey_algo,
305 cert->sig.hash_algo);
306
307 cert->pub->id_type = "X509";
308
309 /* Check the signature on the key if it appears to be self-signed */
310 if ((!cert->akid_skid && !cert->akid_id) ||
311 asymmetric_key_id_same(cert->skid, cert->akid_skid) ||
312 asymmetric_key_id_same(cert->id, cert->akid_id)) {
313 ret = x509_check_signature(cert->pub, cert); /* self-signed */
314 if (ret < 0)
315 goto error_free_cert;
316 } else if (!prep->trusted) {
317 ret = x509_validate_trust(cert, get_system_trusted_keyring());
318 if (ret)
319 ret = x509_validate_trust(cert, get_ima_mok_keyring());
320 if (!ret)
321 prep->trusted = 1;
322 }
323
324 /* Propose a description */
325 sulen = strlen(cert->subject);
326 if (cert->raw_skid) {
327 srlen = cert->raw_skid_size;
328 q = cert->raw_skid;
329 } else {
330 srlen = cert->raw_serial_size;
331 q = cert->raw_serial;
332 }
333
334 ret = -ENOMEM;
335 desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
336 if (!desc)
337 goto error_free_cert;
338 p = memcpy(desc, cert->subject, sulen);
339 p += sulen;
340 *p++ = ':';
341 *p++ = ' ';
342 p = bin2hex(p, q, srlen);
343 *p = 0;
344
345 kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
346 if (!kids)
347 goto error_free_desc;
348 kids->id[0] = cert->id;
349 kids->id[1] = cert->skid;
350
351 /* We're pinning the module by being linked against it */
352 __module_get(public_key_subtype.owner);
353 prep->payload.data[asym_subtype] = &public_key_subtype;
354 prep->payload.data[asym_key_ids] = kids;
355 prep->payload.data[asym_crypto] = cert->pub;
356 prep->description = desc;
357 prep->quotalen = 100;
358
359 /* We've finished with the certificate */
360 cert->pub = NULL;
361 cert->id = NULL;
362 cert->skid = NULL;
363 desc = NULL;
364 ret = 0;
365
366error_free_desc:
367 kfree(desc);
368error_free_cert:
369 x509_free_certificate(cert);
370 return ret;
371}
372
373static struct asymmetric_key_parser x509_key_parser = {
374 .owner = THIS_MODULE,
375 .name = "x509",
376 .parse = x509_key_preparse,
377};
378
379/*
380 * Module stuff
381 */
382static int __init x509_key_init(void)
383{
384 return register_asymmetric_key_parser(&x509_key_parser);
385}
386
387static void __exit x509_key_exit(void)
388{
389 unregister_asymmetric_key_parser(&x509_key_parser);
390}
391
392module_init(x509_key_init);
393module_exit(x509_key_exit);
394
395MODULE_DESCRIPTION("X.509 certificate parser");
396MODULE_LICENSE("GPL");