xref: /linux/kernel/crash_dump_dm_crypt.c (revision ba24659b1dbee90d4ce7ffc7577e299f085533a1) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/key.h>
3 #include <linux/keyctl.h>
4 #include <keys/user-type.h>
5 #include <linux/crash_dump.h>
6 #include <linux/cc_platform.h>
7 #include <linux/configfs.h>
8 #include <linux/module.h>
9 #include <linux/sysfs.h>
10 
11 #define KEY_NUM_MAX 128	/* maximum dm crypt keys */
12 #define KEY_SIZE_MAX 256	/* maximum dm crypt key size */
13 #define KEY_DESC_MAX_LEN 128	/* maximum dm crypt key description size */
14 
15 static unsigned int key_count;
16 
17 struct dm_crypt_key {
18 	unsigned int key_size;
19 	char key_desc[KEY_DESC_MAX_LEN];
20 	u8 data[KEY_SIZE_MAX];
21 };
22 
23 static struct keys_header {
24 	unsigned int total_keys;
25 	struct dm_crypt_key keys[] __counted_by(total_keys);
26 } *keys_header;
27 
28 static size_t get_keys_header_size(size_t total_keys)
29 {
30 	return struct_size(keys_header, keys, total_keys);
31 }
32 
33 unsigned long long dm_crypt_keys_addr;
34 EXPORT_SYMBOL_GPL(dm_crypt_keys_addr);
35 
36 static int __init setup_dmcryptkeys(char *arg)
37 {
38 	char *end;
39 
40 	if (!arg)
41 		return -EINVAL;
42 	dm_crypt_keys_addr = memparse(arg, &end);
43 	if (end > arg)
44 		return 0;
45 
46 	dm_crypt_keys_addr = 0;
47 	return -EINVAL;
48 }
49 
50 early_param("dmcryptkeys", setup_dmcryptkeys);
51 
52 /*
53  * Architectures may override this function to read dm crypt keys
54  */
55 ssize_t __weak dm_crypt_keys_read(char *buf, size_t count, u64 *ppos)
56 {
57 	struct kvec kvec = { .iov_base = buf, .iov_len = count };
58 	struct iov_iter iter;
59 
60 	iov_iter_kvec(&iter, READ, &kvec, 1, count);
61 	return read_from_oldmem(&iter, count, ppos, cc_platform_has(CC_ATTR_MEM_ENCRYPT));
62 }
63 
64 static int add_key_to_keyring(struct dm_crypt_key *dm_key,
65 			      key_ref_t keyring_ref)
66 {
67 	key_ref_t key_ref;
68 	int r;
69 
70 	/* create or update the requested key and add it to the target keyring */
71 	key_ref = key_create_or_update(keyring_ref, "user", dm_key->key_desc,
72 				       dm_key->data, dm_key->key_size,
73 				       KEY_USR_ALL, KEY_ALLOC_IN_QUOTA);
74 
75 	if (!IS_ERR(key_ref)) {
76 		r = key_ref_to_ptr(key_ref)->serial;
77 		key_ref_put(key_ref);
78 		kexec_dprintk("Success adding key %s", dm_key->key_desc);
79 	} else {
80 		r = PTR_ERR(key_ref);
81 		kexec_dprintk("Error when adding key");
82 	}
83 
84 	return r;
85 }
86 
87 static void get_keys_from_kdump_reserved_memory(void)
88 {
89 	struct keys_header *keys_header_loaded;
90 
91 	arch_kexec_unprotect_crashkres();
92 
93 	keys_header_loaded = kmap_local_page(pfn_to_page(
94 		kexec_crash_image->dm_crypt_keys_addr >> PAGE_SHIFT));
95 
96 	memcpy(keys_header, keys_header_loaded, get_keys_header_size(key_count));
97 	kunmap_local(keys_header_loaded);
98 	arch_kexec_protect_crashkres();
99 }
100 
101 static int restore_dm_crypt_keys_to_thread_keyring(void)
102 {
103 	struct dm_crypt_key *key;
104 	size_t keys_header_size;
105 	key_ref_t keyring_ref;
106 	int ret = 0;
107 	u64 addr;
108 
109 	/* find the target keyring (which must be writable) */
110 	keyring_ref =
111 		lookup_user_key(KEY_SPEC_USER_KEYRING, 0x01, KEY_NEED_WRITE);
112 	if (IS_ERR(keyring_ref)) {
113 		kexec_dprintk("Failed to get the user keyring\n");
114 		return PTR_ERR(keyring_ref);
115 	}
116 
117 	addr = dm_crypt_keys_addr;
118 	dm_crypt_keys_read((char *)&key_count, sizeof(key_count), &addr);
119 	if (key_count > KEY_NUM_MAX) {
120 		kexec_dprintk("Failed to read the number of dm-crypt keys\n");
121 		ret = -1;
122 		goto out;
123 	}
124 
125 	kexec_dprintk("There are %u keys\n", key_count);
126 	addr = dm_crypt_keys_addr;
127 
128 	keys_header_size = get_keys_header_size(key_count);
129 	keys_header = kzalloc(keys_header_size, GFP_KERNEL);
130 	if (!keys_header) {
131 		ret = -ENOMEM;
132 		goto out;
133 	}
134 
135 	dm_crypt_keys_read((char *)keys_header, keys_header_size, &addr);
136 
137 	for (int i = 0; i < keys_header->total_keys; i++) {
138 		key = &keys_header->keys[i];
139 		kexec_dprintk("Get key (size=%u)\n", key->key_size);
140 		add_key_to_keyring(key, keyring_ref);
141 	}
142 
143 out:
144 	key_ref_put(keyring_ref);
145 	return ret;
146 }
147 
148 static int read_key_from_user_keyring(struct dm_crypt_key *dm_key)
149 {
150 	const struct user_key_payload *ukp;
151 	struct key *key;
152 	int ret = 0;
153 
154 	kexec_dprintk("Requesting logon key %s", dm_key->key_desc);
155 	key = request_key(&key_type_logon, dm_key->key_desc, NULL);
156 
157 	if (IS_ERR(key)) {
158 		pr_warn("No such logon key %s\n", dm_key->key_desc);
159 		return PTR_ERR(key);
160 	}
161 
162 	down_read(&key->sem);
163 	ukp = user_key_payload_locked(key);
164 	if (!ukp) {
165 		ret = -EKEYREVOKED;
166 		goto out;
167 	}
168 
169 	if (ukp->datalen > KEY_SIZE_MAX) {
170 		pr_err("Key size %u exceeds maximum (%u)\n", ukp->datalen, KEY_SIZE_MAX);
171 		ret = -EINVAL;
172 		goto out;
173 	}
174 
175 	memcpy(dm_key->data, ukp->data, ukp->datalen);
176 	dm_key->key_size = ukp->datalen;
177 	kexec_dprintk("Get dm crypt key (size=%u) %s\n", dm_key->key_size,
178 		      dm_key->key_desc);
179 
180 out:
181 	up_read(&key->sem);
182 	key_put(key);
183 	return ret;
184 }
185 
186 struct config_key {
187 	struct config_item item;
188 	const char *description;
189 };
190 
191 static inline struct config_key *to_config_key(struct config_item *item)
192 {
193 	return container_of(item, struct config_key, item);
194 }
195 
196 static ssize_t config_key_description_show(struct config_item *item, char *page)
197 {
198 	return sysfs_emit(page, "%s\n", to_config_key(item)->description);
199 }
200 
201 static ssize_t config_key_description_store(struct config_item *item,
202 					    const char *page, size_t count)
203 {
204 	struct config_key *config_key = to_config_key(item);
205 	size_t len;
206 	int ret;
207 
208 	ret = -EINVAL;
209 	len = strcspn(page, "\n");
210 
211 	if (len > KEY_DESC_MAX_LEN) {
212 		pr_err("The key description shouldn't exceed %u characters", KEY_DESC_MAX_LEN);
213 		return ret;
214 	}
215 
216 	if (!len)
217 		return ret;
218 
219 	kfree(config_key->description);
220 	ret = -ENOMEM;
221 	config_key->description = kmemdup_nul(page, len, GFP_KERNEL);
222 	if (!config_key->description)
223 		return ret;
224 
225 	return count;
226 }
227 
228 CONFIGFS_ATTR(config_key_, description);
229 
230 static struct configfs_attribute *config_key_attrs[] = {
231 	&config_key_attr_description,
232 	NULL,
233 };
234 
235 static void config_key_release(struct config_item *item)
236 {
237 	kfree(to_config_key(item));
238 	key_count--;
239 }
240 
241 static const struct configfs_item_operations config_key_item_ops = {
242 	.release = config_key_release,
243 };
244 
245 static const struct config_item_type config_key_type = {
246 	.ct_item_ops = &config_key_item_ops,
247 	.ct_attrs = config_key_attrs,
248 	.ct_owner = THIS_MODULE,
249 };
250 
251 static struct config_item *config_keys_make_item(struct config_group *group,
252 						 const char *name)
253 {
254 	struct config_key *config_key;
255 
256 	if (key_count > KEY_NUM_MAX) {
257 		pr_err("Only %u keys at maximum to be created\n", KEY_NUM_MAX);
258 		return ERR_PTR(-EINVAL);
259 	}
260 
261 	config_key = kzalloc_obj(struct config_key);
262 	if (!config_key)
263 		return ERR_PTR(-ENOMEM);
264 
265 	config_item_init_type_name(&config_key->item, name, &config_key_type);
266 
267 	key_count++;
268 
269 	return &config_key->item;
270 }
271 
272 static ssize_t config_keys_count_show(struct config_item *item, char *page)
273 {
274 	return sysfs_emit(page, "%d\n", key_count);
275 }
276 
277 CONFIGFS_ATTR_RO(config_keys_, count);
278 
279 static bool is_dm_key_reused;
280 
281 static ssize_t config_keys_reuse_show(struct config_item *item, char *page)
282 {
283 	return sysfs_emit(page, "%d\n", is_dm_key_reused);
284 }
285 
286 static ssize_t config_keys_reuse_store(struct config_item *item,
287 					   const char *page, size_t count)
288 {
289 	if (!kexec_crash_image || !kexec_crash_image->dm_crypt_keys_addr) {
290 		kexec_dprintk(
291 			"dm-crypt keys haven't be saved to crash-reserved memory\n");
292 		return -EINVAL;
293 	}
294 
295 	if (kstrtobool(page, &is_dm_key_reused))
296 		return -EINVAL;
297 
298 	if (is_dm_key_reused)
299 		get_keys_from_kdump_reserved_memory();
300 
301 	return count;
302 }
303 
304 CONFIGFS_ATTR(config_keys_, reuse);
305 
306 static struct configfs_attribute *config_keys_attrs[] = {
307 	&config_keys_attr_count,
308 	&config_keys_attr_reuse,
309 	NULL,
310 };
311 
312 /*
313  * Note that, since no extra work is required on ->drop_item(),
314  * no ->drop_item() is provided.
315  */
316 static const struct configfs_group_operations config_keys_group_ops = {
317 	.make_item = config_keys_make_item,
318 };
319 
320 static const struct config_item_type config_keys_type = {
321 	.ct_group_ops = &config_keys_group_ops,
322 	.ct_attrs = config_keys_attrs,
323 	.ct_owner = THIS_MODULE,
324 };
325 
326 static bool restore;
327 
328 static ssize_t config_keys_restore_show(struct config_item *item, char *page)
329 {
330 	return sysfs_emit(page, "%d\n", restore);
331 }
332 
333 static ssize_t config_keys_restore_store(struct config_item *item,
334 					  const char *page, size_t count)
335 {
336 	if (!restore)
337 		restore_dm_crypt_keys_to_thread_keyring();
338 
339 	if (kstrtobool(page, &restore))
340 		return -EINVAL;
341 
342 	return count;
343 }
344 
345 CONFIGFS_ATTR(config_keys_, restore);
346 
347 static struct configfs_attribute *kdump_config_keys_attrs[] = {
348 	&config_keys_attr_restore,
349 	NULL,
350 };
351 
352 static const struct config_item_type kdump_config_keys_type = {
353 	.ct_attrs = kdump_config_keys_attrs,
354 	.ct_owner = THIS_MODULE,
355 };
356 
357 static struct configfs_subsystem config_keys_subsys = {
358 	.su_group = {
359 		.cg_item = {
360 			.ci_namebuf = "crash_dm_crypt_keys",
361 			.ci_type = &config_keys_type,
362 		},
363 	},
364 };
365 
366 static int build_keys_header(void)
367 {
368 	struct config_item *item = NULL;
369 	struct config_key *key;
370 	int i, r;
371 
372 	if (keys_header != NULL)
373 		kvfree(keys_header);
374 
375 	keys_header = kzalloc(get_keys_header_size(key_count), GFP_KERNEL);
376 	if (!keys_header)
377 		return -ENOMEM;
378 
379 	keys_header->total_keys = key_count;
380 
381 	i = 0;
382 	list_for_each_entry(item, &config_keys_subsys.su_group.cg_children,
383 			    ci_entry) {
384 		if (item->ci_type != &config_key_type)
385 			continue;
386 
387 		key = to_config_key(item);
388 
389 		if (!key->description) {
390 			pr_warn("No key description for key %s\n", item->ci_name);
391 			return -EINVAL;
392 		}
393 
394 		strscpy(keys_header->keys[i].key_desc, key->description,
395 			KEY_DESC_MAX_LEN);
396 		r = read_key_from_user_keyring(&keys_header->keys[i]);
397 		if (r != 0) {
398 			kexec_dprintk("Failed to read key %s\n",
399 				      keys_header->keys[i].key_desc);
400 			return r;
401 		}
402 		i++;
403 		kexec_dprintk("Found key: %s\n", item->ci_name);
404 	}
405 
406 	return 0;
407 }
408 
409 int crash_load_dm_crypt_keys(struct kimage *image)
410 {
411 	struct kexec_buf kbuf = {
412 		.image = image,
413 		.buf_min = 0,
414 		.buf_max = ULONG_MAX,
415 		.top_down = false,
416 		.random = true,
417 	};
418 	int r;
419 
420 
421 	if (key_count <= 0) {
422 		kexec_dprintk("No dm-crypt keys\n");
423 		return 0;
424 	}
425 
426 	if (!is_dm_key_reused) {
427 		image->dm_crypt_keys_addr = 0;
428 		r = build_keys_header();
429 		if (r) {
430 			pr_err("Failed to build dm-crypt keys header, ret=%d\n", r);
431 			return r;
432 		}
433 	}
434 
435 	kbuf.buffer = keys_header;
436 	kbuf.bufsz = get_keys_header_size(key_count);
437 
438 	kbuf.memsz = kbuf.bufsz;
439 	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
440 	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
441 	r = kexec_add_buffer(&kbuf);
442 	if (r) {
443 		pr_err("Failed to call kexec_add_buffer, ret=%d\n", r);
444 		kvfree((void *)kbuf.buffer);
445 		return r;
446 	}
447 	image->dm_crypt_keys_addr = kbuf.mem;
448 	image->dm_crypt_keys_sz = kbuf.bufsz;
449 	kexec_dprintk(
450 		"Loaded dm crypt keys to kexec_buffer bufsz=0x%lx memsz=0x%lx\n",
451 		kbuf.bufsz, kbuf.memsz);
452 
453 	return r;
454 }
455 
456 static int __init configfs_dmcrypt_keys_init(void)
457 {
458 	int ret;
459 
460 	if (is_kdump_kernel()) {
461 		config_keys_subsys.su_group.cg_item.ci_type =
462 			&kdump_config_keys_type;
463 	}
464 
465 	config_group_init(&config_keys_subsys.su_group);
466 	mutex_init(&config_keys_subsys.su_mutex);
467 	ret = configfs_register_subsystem(&config_keys_subsys);
468 	if (ret) {
469 		pr_err("Error %d while registering subsystem %s\n", ret,
470 		       config_keys_subsys.su_group.cg_item.ci_namebuf);
471 		goto out_unregister;
472 	}
473 
474 	return 0;
475 
476 out_unregister:
477 	configfs_unregister_subsystem(&config_keys_subsys);
478 
479 	return ret;
480 }
481 
482 module_init(configfs_dmcrypt_keys_init);
483