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