1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2010 IBM Corporation
4  * Copyright (c) 2019-2021, Linaro Limited
5  *
6  * See Documentation/security/keys/trusted-encrypted.rst
7  */
8 
9 #include <keys/user-type.h>
10 #include <keys/trusted-type.h>
11 #include <keys/trusted_tee.h>
12 #include <keys/trusted_caam.h>
13 #include <keys/trusted_tpm.h>
14 #include <linux/capability.h>
15 #include <linux/err.h>
16 #include <linux/init.h>
17 #include <linux/key-type.h>
18 #include <linux/module.h>
19 #include <linux/parser.h>
20 #include <linux/random.h>
21 #include <linux/rcupdate.h>
22 #include <linux/slab.h>
23 #include <linux/static_call.h>
24 #include <linux/string.h>
25 #include <linux/uaccess.h>
26 
27 static char *trusted_rng = "default";
28 module_param_named(rng, trusted_rng, charp, 0);
29 MODULE_PARM_DESC(rng, "Select trusted key RNG");
30 
31 static char *trusted_key_source;
32 module_param_named(source, trusted_key_source, charp, 0);
33 MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee or caam)");
34 
35 static const struct trusted_key_source trusted_key_sources[] = {
36 #if defined(CONFIG_TRUSTED_KEYS_TPM)
37 	{ "tpm", &trusted_key_tpm_ops },
38 #endif
39 #if defined(CONFIG_TRUSTED_KEYS_TEE)
40 	{ "tee", &trusted_key_tee_ops },
41 #endif
42 #if defined(CONFIG_TRUSTED_KEYS_CAAM)
43 	{ "caam", &trusted_key_caam_ops },
44 #endif
45 };
46 
47 DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init);
48 DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
49 DEFINE_STATIC_CALL_NULL(trusted_key_unseal,
50 			*trusted_key_sources[0].ops->unseal);
51 DEFINE_STATIC_CALL_NULL(trusted_key_get_random,
52 			*trusted_key_sources[0].ops->get_random);
53 DEFINE_STATIC_CALL_NULL(trusted_key_exit, *trusted_key_sources[0].ops->exit);
54 static unsigned char migratable;
55 
56 enum {
57 	Opt_err,
58 	Opt_new, Opt_load, Opt_update,
59 };
60 
61 static const match_table_t key_tokens = {
62 	{Opt_new, "new"},
63 	{Opt_load, "load"},
64 	{Opt_update, "update"},
65 	{Opt_err, NULL}
66 };
67 
68 /*
69  * datablob_parse - parse the keyctl data and fill in the
70  *                  payload structure
71  *
72  * On success returns 0, otherwise -EINVAL.
73  */
datablob_parse(char ** datablob,struct trusted_key_payload * p)74 static int datablob_parse(char **datablob, struct trusted_key_payload *p)
75 {
76 	substring_t args[MAX_OPT_ARGS];
77 	long keylen;
78 	int ret = -EINVAL;
79 	int key_cmd;
80 	char *c;
81 
82 	/* main command */
83 	c = strsep(datablob, " \t");
84 	if (!c)
85 		return -EINVAL;
86 	key_cmd = match_token(c, key_tokens, args);
87 	switch (key_cmd) {
88 	case Opt_new:
89 		/* first argument is key size */
90 		c = strsep(datablob, " \t");
91 		if (!c)
92 			return -EINVAL;
93 		ret = kstrtol(c, 10, &keylen);
94 		if (ret < 0 || keylen < MIN_KEY_SIZE || keylen > MAX_KEY_SIZE)
95 			return -EINVAL;
96 		p->key_len = keylen;
97 		ret = Opt_new;
98 		break;
99 	case Opt_load:
100 		/* first argument is sealed blob */
101 		c = strsep(datablob, " \t");
102 		if (!c)
103 			return -EINVAL;
104 		p->blob_len = strlen(c) / 2;
105 		if (p->blob_len > MAX_BLOB_SIZE)
106 			return -EINVAL;
107 		ret = hex2bin(p->blob, c, p->blob_len);
108 		if (ret < 0)
109 			return -EINVAL;
110 		ret = Opt_load;
111 		break;
112 	case Opt_update:
113 		ret = Opt_update;
114 		break;
115 	case Opt_err:
116 		return -EINVAL;
117 	}
118 	return ret;
119 }
120 
trusted_payload_alloc(struct key * key)121 static struct trusted_key_payload *trusted_payload_alloc(struct key *key)
122 {
123 	struct trusted_key_payload *p = NULL;
124 	int ret;
125 
126 	ret = key_payload_reserve(key, sizeof(*p));
127 	if (ret < 0)
128 		goto err;
129 	p = kzalloc(sizeof(*p), GFP_KERNEL);
130 	if (!p)
131 		goto err;
132 
133 	p->migratable = migratable;
134 err:
135 	return p;
136 }
137 
138 /*
139  * trusted_instantiate - create a new trusted key
140  *
141  * Unseal an existing trusted blob or, for a new key, get a
142  * random key, then seal and create a trusted key-type key,
143  * adding it to the specified keyring.
144  *
145  * On success, return 0. Otherwise return errno.
146  */
trusted_instantiate(struct key * key,struct key_preparsed_payload * prep)147 static int trusted_instantiate(struct key *key,
148 			       struct key_preparsed_payload *prep)
149 {
150 	struct trusted_key_payload *payload = NULL;
151 	size_t datalen = prep->datalen;
152 	char *datablob, *orig_datablob;
153 	int ret = 0;
154 	int key_cmd;
155 	size_t key_len;
156 
157 	if (datalen <= 0 || datalen > 32767 || !prep->data)
158 		return -EINVAL;
159 
160 	orig_datablob = datablob = kmalloc(datalen + 1, GFP_KERNEL);
161 	if (!datablob)
162 		return -ENOMEM;
163 	memcpy(datablob, prep->data, datalen);
164 	datablob[datalen] = '\0';
165 
166 	payload = trusted_payload_alloc(key);
167 	if (!payload) {
168 		ret = -ENOMEM;
169 		goto out;
170 	}
171 
172 	key_cmd = datablob_parse(&datablob, payload);
173 	if (key_cmd < 0) {
174 		ret = key_cmd;
175 		goto out;
176 	}
177 
178 	dump_payload(payload);
179 
180 	switch (key_cmd) {
181 	case Opt_load:
182 		ret = static_call(trusted_key_unseal)(payload, datablob);
183 		dump_payload(payload);
184 		if (ret < 0)
185 			pr_info("key_unseal failed (%d)\n", ret);
186 		break;
187 	case Opt_new:
188 		key_len = payload->key_len;
189 		ret = static_call(trusted_key_get_random)(payload->key,
190 							  key_len);
191 		if (ret < 0)
192 			goto out;
193 
194 		if (ret != key_len) {
195 			pr_info("key_create failed (%d)\n", ret);
196 			ret = -EIO;
197 			goto out;
198 		}
199 
200 		ret = static_call(trusted_key_seal)(payload, datablob);
201 		if (ret < 0)
202 			pr_info("key_seal failed (%d)\n", ret);
203 		break;
204 	default:
205 		ret = -EINVAL;
206 	}
207 out:
208 	kfree_sensitive(orig_datablob);
209 	if (!ret)
210 		rcu_assign_keypointer(key, payload);
211 	else
212 		kfree_sensitive(payload);
213 	return ret;
214 }
215 
trusted_rcu_free(struct rcu_head * rcu)216 static void trusted_rcu_free(struct rcu_head *rcu)
217 {
218 	struct trusted_key_payload *p;
219 
220 	p = container_of(rcu, struct trusted_key_payload, rcu);
221 	kfree_sensitive(p);
222 }
223 
224 /*
225  * trusted_update - reseal an existing key with new PCR values
226  */
trusted_update(struct key * key,struct key_preparsed_payload * prep)227 static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
228 {
229 	struct trusted_key_payload *p;
230 	struct trusted_key_payload *new_p;
231 	size_t datalen = prep->datalen;
232 	char *datablob, *orig_datablob;
233 	int ret = 0;
234 
235 	if (key_is_negative(key))
236 		return -ENOKEY;
237 	p = key->payload.data[0];
238 	if (!p->migratable)
239 		return -EPERM;
240 	if (datalen <= 0 || datalen > 32767 || !prep->data)
241 		return -EINVAL;
242 
243 	orig_datablob = datablob = kmalloc(datalen + 1, GFP_KERNEL);
244 	if (!datablob)
245 		return -ENOMEM;
246 
247 	new_p = trusted_payload_alloc(key);
248 	if (!new_p) {
249 		ret = -ENOMEM;
250 		goto out;
251 	}
252 
253 	memcpy(datablob, prep->data, datalen);
254 	datablob[datalen] = '\0';
255 	ret = datablob_parse(&datablob, new_p);
256 	if (ret != Opt_update) {
257 		ret = -EINVAL;
258 		kfree_sensitive(new_p);
259 		goto out;
260 	}
261 
262 	/* copy old key values, and reseal with new pcrs */
263 	new_p->migratable = p->migratable;
264 	new_p->key_len = p->key_len;
265 	memcpy(new_p->key, p->key, p->key_len);
266 	dump_payload(p);
267 	dump_payload(new_p);
268 
269 	ret = static_call(trusted_key_seal)(new_p, datablob);
270 	if (ret < 0) {
271 		pr_info("key_seal failed (%d)\n", ret);
272 		kfree_sensitive(new_p);
273 		goto out;
274 	}
275 
276 	rcu_assign_keypointer(key, new_p);
277 	call_rcu(&p->rcu, trusted_rcu_free);
278 out:
279 	kfree_sensitive(orig_datablob);
280 	return ret;
281 }
282 
283 /*
284  * trusted_read - copy the sealed blob data to userspace in hex.
285  * On success, return to userspace the trusted key datablob size.
286  */
trusted_read(const struct key * key,char * buffer,size_t buflen)287 static long trusted_read(const struct key *key, char *buffer,
288 			 size_t buflen)
289 {
290 	const struct trusted_key_payload *p;
291 	char *bufp;
292 	int i;
293 
294 	p = dereference_key_locked(key);
295 	if (!p)
296 		return -EINVAL;
297 
298 	if (buffer && buflen >= 2 * p->blob_len) {
299 		bufp = buffer;
300 		for (i = 0; i < p->blob_len; i++)
301 			bufp = hex_byte_pack(bufp, p->blob[i]);
302 	}
303 	return 2 * p->blob_len;
304 }
305 
306 /*
307  * trusted_destroy - clear and free the key's payload
308  */
trusted_destroy(struct key * key)309 static void trusted_destroy(struct key *key)
310 {
311 	kfree_sensitive(key->payload.data[0]);
312 }
313 
314 struct key_type key_type_trusted = {
315 	.name = "trusted",
316 	.instantiate = trusted_instantiate,
317 	.update = trusted_update,
318 	.destroy = trusted_destroy,
319 	.describe = user_describe,
320 	.read = trusted_read,
321 };
322 EXPORT_SYMBOL_GPL(key_type_trusted);
323 
kernel_get_random(unsigned char * key,size_t key_len)324 static int kernel_get_random(unsigned char *key, size_t key_len)
325 {
326 	return get_random_bytes_wait(key, key_len) ?: key_len;
327 }
328 
init_trusted(void)329 static int __init init_trusted(void)
330 {
331 	int (*get_random)(unsigned char *key, size_t key_len);
332 	int i, ret = 0;
333 
334 	for (i = 0; i < ARRAY_SIZE(trusted_key_sources); i++) {
335 		if (trusted_key_source &&
336 		    strncmp(trusted_key_source, trusted_key_sources[i].name,
337 			    strlen(trusted_key_sources[i].name)))
338 			continue;
339 
340 		/*
341 		 * We always support trusted.rng="kernel" and "default" as
342 		 * well as trusted.rng=$trusted.source if the trust source
343 		 * defines its own get_random callback.
344 		 */
345 		get_random = trusted_key_sources[i].ops->get_random;
346 		if (trusted_rng && strcmp(trusted_rng, "default")) {
347 			if (!strcmp(trusted_rng, "kernel")) {
348 				get_random = kernel_get_random;
349 			} else if (strcmp(trusted_rng, trusted_key_sources[i].name) ||
350 				   !get_random) {
351 				pr_warn("Unsupported RNG. Supported: kernel");
352 				if (get_random)
353 					pr_cont(", %s", trusted_key_sources[i].name);
354 				pr_cont(", default\n");
355 				return -EINVAL;
356 			}
357 		}
358 
359 		if (!get_random)
360 			get_random = kernel_get_random;
361 
362 		static_call_update(trusted_key_init,
363 				   trusted_key_sources[i].ops->init);
364 		static_call_update(trusted_key_seal,
365 				   trusted_key_sources[i].ops->seal);
366 		static_call_update(trusted_key_unseal,
367 				   trusted_key_sources[i].ops->unseal);
368 		static_call_update(trusted_key_get_random,
369 				   get_random);
370 		static_call_update(trusted_key_exit,
371 				   trusted_key_sources[i].ops->exit);
372 		migratable = trusted_key_sources[i].ops->migratable;
373 
374 		ret = static_call(trusted_key_init)();
375 		if (!ret)
376 			break;
377 	}
378 
379 	/*
380 	 * encrypted_keys.ko depends on successful load of this module even if
381 	 * trusted key implementation is not found.
382 	 */
383 	if (ret == -ENODEV)
384 		return 0;
385 
386 	return ret;
387 }
388 
cleanup_trusted(void)389 static void __exit cleanup_trusted(void)
390 {
391 	static_call_cond(trusted_key_exit)();
392 }
393 
394 late_initcall(init_trusted);
395 module_exit(cleanup_trusted);
396 
397 MODULE_LICENSE("GPL");
398