1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2010 IBM Corporation
4  * Copyright (C) 2010 Politecnico di Torino, Italy
5  *                    TORSEC group -- https://security.polito.it
6  *
7  * Authors:
8  * Mimi Zohar <zohar@us.ibm.com>
9  * Roberto Sassu <roberto.sassu@polito.it>
10  *
11  * See Documentation/security/keys/trusted-encrypted.rst
12  */
13 
14 #include <linux/uaccess.h>
15 #include <linux/module.h>
16 #include <linux/init.h>
17 #include <linux/slab.h>
18 #include <linux/parser.h>
19 #include <linux/string.h>
20 #include <linux/err.h>
21 #include <keys/user-type.h>
22 #include <keys/trusted-type.h>
23 #include <keys/encrypted-type.h>
24 #include <linux/key-type.h>
25 #include <linux/random.h>
26 #include <linux/rcupdate.h>
27 #include <linux/scatterlist.h>
28 #include <linux/ctype.h>
29 #include <crypto/aes.h>
30 #include <crypto/algapi.h>
31 #include <crypto/hash.h>
32 #include <crypto/sha2.h>
33 #include <crypto/skcipher.h>
34 
35 #include "encrypted.h"
36 #include "ecryptfs_format.h"
37 
38 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
39 static const char KEY_USER_PREFIX[] = "user:";
40 static const char hash_alg[] = "sha256";
41 static const char hmac_alg[] = "hmac(sha256)";
42 static const char blkcipher_alg[] = "cbc(aes)";
43 static const char key_format_default[] = "default";
44 static const char key_format_ecryptfs[] = "ecryptfs";
45 static const char key_format_enc32[] = "enc32";
46 static unsigned int ivsize;
47 static int blksize;
48 
49 #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
50 #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
51 #define KEY_ECRYPTFS_DESC_LEN 16
52 #define HASH_SIZE SHA256_DIGEST_SIZE
53 #define MAX_DATA_SIZE 4096
54 #define MIN_DATA_SIZE  20
55 #define KEY_ENC32_PAYLOAD_LEN 32
56 
57 static struct crypto_shash *hash_tfm;
58 
59 enum {
60 	Opt_new, Opt_load, Opt_update, Opt_err
61 };
62 
63 enum {
64 	Opt_default, Opt_ecryptfs, Opt_enc32, Opt_error
65 };
66 
67 static const match_table_t key_format_tokens = {
68 	{Opt_default, "default"},
69 	{Opt_ecryptfs, "ecryptfs"},
70 	{Opt_enc32, "enc32"},
71 	{Opt_error, NULL}
72 };
73 
74 static const match_table_t key_tokens = {
75 	{Opt_new, "new"},
76 	{Opt_load, "load"},
77 	{Opt_update, "update"},
78 	{Opt_err, NULL}
79 };
80 
81 static int aes_get_sizes(void)
82 {
83 	struct crypto_skcipher *tfm;
84 
85 	tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
86 	if (IS_ERR(tfm)) {
87 		pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
88 		       PTR_ERR(tfm));
89 		return PTR_ERR(tfm);
90 	}
91 	ivsize = crypto_skcipher_ivsize(tfm);
92 	blksize = crypto_skcipher_blocksize(tfm);
93 	crypto_free_skcipher(tfm);
94 	return 0;
95 }
96 
97 /*
98  * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
99  *
100  * The description of a encrypted key with format 'ecryptfs' must contain
101  * exactly 16 hexadecimal characters.
102  *
103  */
104 static int valid_ecryptfs_desc(const char *ecryptfs_desc)
105 {
106 	int i;
107 
108 	if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) {
109 		pr_err("encrypted_key: key description must be %d hexadecimal "
110 		       "characters long\n", KEY_ECRYPTFS_DESC_LEN);
111 		return -EINVAL;
112 	}
113 
114 	for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) {
115 		if (!isxdigit(ecryptfs_desc[i])) {
116 			pr_err("encrypted_key: key description must contain "
117 			       "only hexadecimal characters\n");
118 			return -EINVAL;
119 		}
120 	}
121 
122 	return 0;
123 }
124 
125 /*
126  * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
127  *
128  * key-type:= "trusted:" | "user:"
129  * desc:= master-key description
130  *
131  * Verify that 'key-type' is valid and that 'desc' exists. On key update,
132  * only the master key description is permitted to change, not the key-type.
133  * The key-type remains constant.
134  *
135  * On success returns 0, otherwise -EINVAL.
136  */
137 static int valid_master_desc(const char *new_desc, const char *orig_desc)
138 {
139 	int prefix_len;
140 
141 	if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
142 		prefix_len = KEY_TRUSTED_PREFIX_LEN;
143 	else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
144 		prefix_len = KEY_USER_PREFIX_LEN;
145 	else
146 		return -EINVAL;
147 
148 	if (!new_desc[prefix_len])
149 		return -EINVAL;
150 
151 	if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
152 		return -EINVAL;
153 
154 	return 0;
155 }
156 
157 /*
158  * datablob_parse - parse the keyctl data
159  *
160  * datablob format:
161  * new [<format>] <master-key name> <decrypted data length>
162  * load [<format>] <master-key name> <decrypted data length>
163  *     <encrypted iv + data>
164  * update <new-master-key name>
165  *
166  * Tokenizes a copy of the keyctl data, returning a pointer to each token,
167  * which is null terminated.
168  *
169  * On success returns 0, otherwise -EINVAL.
170  */
171 static int datablob_parse(char *datablob, const char **format,
172 			  char **master_desc, char **decrypted_datalen,
173 			  char **hex_encoded_iv)
174 {
175 	substring_t args[MAX_OPT_ARGS];
176 	int ret = -EINVAL;
177 	int key_cmd;
178 	int key_format;
179 	char *p, *keyword;
180 
181 	keyword = strsep(&datablob, " \t");
182 	if (!keyword) {
183 		pr_info("encrypted_key: insufficient parameters specified\n");
184 		return ret;
185 	}
186 	key_cmd = match_token(keyword, key_tokens, args);
187 
188 	/* Get optional format: default | ecryptfs */
189 	p = strsep(&datablob, " \t");
190 	if (!p) {
191 		pr_err("encrypted_key: insufficient parameters specified\n");
192 		return ret;
193 	}
194 
195 	key_format = match_token(p, key_format_tokens, args);
196 	switch (key_format) {
197 	case Opt_ecryptfs:
198 	case Opt_enc32:
199 	case Opt_default:
200 		*format = p;
201 		*master_desc = strsep(&datablob, " \t");
202 		break;
203 	case Opt_error:
204 		*master_desc = p;
205 		break;
206 	}
207 
208 	if (!*master_desc) {
209 		pr_info("encrypted_key: master key parameter is missing\n");
210 		goto out;
211 	}
212 
213 	if (valid_master_desc(*master_desc, NULL) < 0) {
214 		pr_info("encrypted_key: master key parameter \'%s\' "
215 			"is invalid\n", *master_desc);
216 		goto out;
217 	}
218 
219 	if (decrypted_datalen) {
220 		*decrypted_datalen = strsep(&datablob, " \t");
221 		if (!*decrypted_datalen) {
222 			pr_info("encrypted_key: keylen parameter is missing\n");
223 			goto out;
224 		}
225 	}
226 
227 	switch (key_cmd) {
228 	case Opt_new:
229 		if (!decrypted_datalen) {
230 			pr_info("encrypted_key: keyword \'%s\' not allowed "
231 				"when called from .update method\n", keyword);
232 			break;
233 		}
234 		ret = 0;
235 		break;
236 	case Opt_load:
237 		if (!decrypted_datalen) {
238 			pr_info("encrypted_key: keyword \'%s\' not allowed "
239 				"when called from .update method\n", keyword);
240 			break;
241 		}
242 		*hex_encoded_iv = strsep(&datablob, " \t");
243 		if (!*hex_encoded_iv) {
244 			pr_info("encrypted_key: hex blob is missing\n");
245 			break;
246 		}
247 		ret = 0;
248 		break;
249 	case Opt_update:
250 		if (decrypted_datalen) {
251 			pr_info("encrypted_key: keyword \'%s\' not allowed "
252 				"when called from .instantiate method\n",
253 				keyword);
254 			break;
255 		}
256 		ret = 0;
257 		break;
258 	case Opt_err:
259 		pr_info("encrypted_key: keyword \'%s\' not recognized\n",
260 			keyword);
261 		break;
262 	}
263 out:
264 	return ret;
265 }
266 
267 /*
268  * datablob_format - format as an ascii string, before copying to userspace
269  */
270 static char *datablob_format(struct encrypted_key_payload *epayload,
271 			     size_t asciiblob_len)
272 {
273 	char *ascii_buf, *bufp;
274 	u8 *iv = epayload->iv;
275 	int len;
276 	int i;
277 
278 	ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
279 	if (!ascii_buf)
280 		goto out;
281 
282 	ascii_buf[asciiblob_len] = '\0';
283 
284 	/* copy datablob master_desc and datalen strings */
285 	len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
286 		      epayload->master_desc, epayload->datalen);
287 
288 	/* convert the hex encoded iv, encrypted-data and HMAC to ascii */
289 	bufp = &ascii_buf[len];
290 	for (i = 0; i < (asciiblob_len - len) / 2; i++)
291 		bufp = hex_byte_pack(bufp, iv[i]);
292 out:
293 	return ascii_buf;
294 }
295 
296 /*
297  * request_user_key - request the user key
298  *
299  * Use a user provided key to encrypt/decrypt an encrypted-key.
300  */
301 static struct key *request_user_key(const char *master_desc, const u8 **master_key,
302 				    size_t *master_keylen)
303 {
304 	const struct user_key_payload *upayload;
305 	struct key *ukey;
306 
307 	ukey = request_key(&key_type_user, master_desc, NULL);
308 	if (IS_ERR(ukey))
309 		goto error;
310 
311 	down_read(&ukey->sem);
312 	upayload = user_key_payload_locked(ukey);
313 	if (!upayload) {
314 		/* key was revoked before we acquired its semaphore */
315 		up_read(&ukey->sem);
316 		key_put(ukey);
317 		ukey = ERR_PTR(-EKEYREVOKED);
318 		goto error;
319 	}
320 	*master_key = upayload->data;
321 	*master_keylen = upayload->datalen;
322 error:
323 	return ukey;
324 }
325 
326 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
327 		     const u8 *buf, unsigned int buflen)
328 {
329 	struct crypto_shash *tfm;
330 	int err;
331 
332 	tfm = crypto_alloc_shash(hmac_alg, 0, 0);
333 	if (IS_ERR(tfm)) {
334 		pr_err("encrypted_key: can't alloc %s transform: %ld\n",
335 		       hmac_alg, PTR_ERR(tfm));
336 		return PTR_ERR(tfm);
337 	}
338 
339 	err = crypto_shash_setkey(tfm, key, keylen);
340 	if (!err)
341 		err = crypto_shash_tfm_digest(tfm, buf, buflen, digest);
342 	crypto_free_shash(tfm);
343 	return err;
344 }
345 
346 enum derived_key_type { ENC_KEY, AUTH_KEY };
347 
348 /* Derive authentication/encryption key from trusted key */
349 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
350 			   const u8 *master_key, size_t master_keylen)
351 {
352 	u8 *derived_buf;
353 	unsigned int derived_buf_len;
354 	int ret;
355 
356 	derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
357 	if (derived_buf_len < HASH_SIZE)
358 		derived_buf_len = HASH_SIZE;
359 
360 	derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
361 	if (!derived_buf)
362 		return -ENOMEM;
363 
364 	if (key_type)
365 		strcpy(derived_buf, "AUTH_KEY");
366 	else
367 		strcpy(derived_buf, "ENC_KEY");
368 
369 	memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
370 	       master_keylen);
371 	ret = crypto_shash_tfm_digest(hash_tfm, derived_buf, derived_buf_len,
372 				      derived_key);
373 	kfree_sensitive(derived_buf);
374 	return ret;
375 }
376 
377 static struct skcipher_request *init_skcipher_req(const u8 *key,
378 						  unsigned int key_len)
379 {
380 	struct skcipher_request *req;
381 	struct crypto_skcipher *tfm;
382 	int ret;
383 
384 	tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
385 	if (IS_ERR(tfm)) {
386 		pr_err("encrypted_key: failed to load %s transform (%ld)\n",
387 		       blkcipher_alg, PTR_ERR(tfm));
388 		return ERR_CAST(tfm);
389 	}
390 
391 	ret = crypto_skcipher_setkey(tfm, key, key_len);
392 	if (ret < 0) {
393 		pr_err("encrypted_key: failed to setkey (%d)\n", ret);
394 		crypto_free_skcipher(tfm);
395 		return ERR_PTR(ret);
396 	}
397 
398 	req = skcipher_request_alloc(tfm, GFP_KERNEL);
399 	if (!req) {
400 		pr_err("encrypted_key: failed to allocate request for %s\n",
401 		       blkcipher_alg);
402 		crypto_free_skcipher(tfm);
403 		return ERR_PTR(-ENOMEM);
404 	}
405 
406 	skcipher_request_set_callback(req, 0, NULL, NULL);
407 	return req;
408 }
409 
410 static struct key *request_master_key(struct encrypted_key_payload *epayload,
411 				      const u8 **master_key, size_t *master_keylen)
412 {
413 	struct key *mkey = ERR_PTR(-EINVAL);
414 
415 	if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
416 		     KEY_TRUSTED_PREFIX_LEN)) {
417 		mkey = request_trusted_key(epayload->master_desc +
418 					   KEY_TRUSTED_PREFIX_LEN,
419 					   master_key, master_keylen);
420 	} else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
421 			    KEY_USER_PREFIX_LEN)) {
422 		mkey = request_user_key(epayload->master_desc +
423 					KEY_USER_PREFIX_LEN,
424 					master_key, master_keylen);
425 	} else
426 		goto out;
427 
428 	if (IS_ERR(mkey)) {
429 		int ret = PTR_ERR(mkey);
430 
431 		if (ret == -ENOTSUPP)
432 			pr_info("encrypted_key: key %s not supported",
433 				epayload->master_desc);
434 		else
435 			pr_info("encrypted_key: key %s not found",
436 				epayload->master_desc);
437 		goto out;
438 	}
439 
440 	dump_master_key(*master_key, *master_keylen);
441 out:
442 	return mkey;
443 }
444 
445 /* Before returning data to userspace, encrypt decrypted data. */
446 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
447 			       const u8 *derived_key,
448 			       unsigned int derived_keylen)
449 {
450 	struct scatterlist sg_in[2];
451 	struct scatterlist sg_out[1];
452 	struct crypto_skcipher *tfm;
453 	struct skcipher_request *req;
454 	unsigned int encrypted_datalen;
455 	u8 iv[AES_BLOCK_SIZE];
456 	int ret;
457 
458 	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
459 
460 	req = init_skcipher_req(derived_key, derived_keylen);
461 	ret = PTR_ERR(req);
462 	if (IS_ERR(req))
463 		goto out;
464 	dump_decrypted_data(epayload);
465 
466 	sg_init_table(sg_in, 2);
467 	sg_set_buf(&sg_in[0], epayload->decrypted_data,
468 		   epayload->decrypted_datalen);
469 	sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
470 
471 	sg_init_table(sg_out, 1);
472 	sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
473 
474 	memcpy(iv, epayload->iv, sizeof(iv));
475 	skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
476 	ret = crypto_skcipher_encrypt(req);
477 	tfm = crypto_skcipher_reqtfm(req);
478 	skcipher_request_free(req);
479 	crypto_free_skcipher(tfm);
480 	if (ret < 0)
481 		pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
482 	else
483 		dump_encrypted_data(epayload, encrypted_datalen);
484 out:
485 	return ret;
486 }
487 
488 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
489 				const u8 *master_key, size_t master_keylen)
490 {
491 	u8 derived_key[HASH_SIZE];
492 	u8 *digest;
493 	int ret;
494 
495 	ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
496 	if (ret < 0)
497 		goto out;
498 
499 	digest = epayload->format + epayload->datablob_len;
500 	ret = calc_hmac(digest, derived_key, sizeof derived_key,
501 			epayload->format, epayload->datablob_len);
502 	if (!ret)
503 		dump_hmac(NULL, digest, HASH_SIZE);
504 out:
505 	memzero_explicit(derived_key, sizeof(derived_key));
506 	return ret;
507 }
508 
509 /* verify HMAC before decrypting encrypted key */
510 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
511 				const u8 *format, const u8 *master_key,
512 				size_t master_keylen)
513 {
514 	u8 derived_key[HASH_SIZE];
515 	u8 digest[HASH_SIZE];
516 	int ret;
517 	char *p;
518 	unsigned short len;
519 
520 	ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
521 	if (ret < 0)
522 		goto out;
523 
524 	len = epayload->datablob_len;
525 	if (!format) {
526 		p = epayload->master_desc;
527 		len -= strlen(epayload->format) + 1;
528 	} else
529 		p = epayload->format;
530 
531 	ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
532 	if (ret < 0)
533 		goto out;
534 	ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
535 			    sizeof(digest));
536 	if (ret) {
537 		ret = -EINVAL;
538 		dump_hmac("datablob",
539 			  epayload->format + epayload->datablob_len,
540 			  HASH_SIZE);
541 		dump_hmac("calc", digest, HASH_SIZE);
542 	}
543 out:
544 	memzero_explicit(derived_key, sizeof(derived_key));
545 	return ret;
546 }
547 
548 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
549 			       const u8 *derived_key,
550 			       unsigned int derived_keylen)
551 {
552 	struct scatterlist sg_in[1];
553 	struct scatterlist sg_out[2];
554 	struct crypto_skcipher *tfm;
555 	struct skcipher_request *req;
556 	unsigned int encrypted_datalen;
557 	u8 iv[AES_BLOCK_SIZE];
558 	u8 *pad;
559 	int ret;
560 
561 	/* Throwaway buffer to hold the unused zero padding at the end */
562 	pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
563 	if (!pad)
564 		return -ENOMEM;
565 
566 	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
567 	req = init_skcipher_req(derived_key, derived_keylen);
568 	ret = PTR_ERR(req);
569 	if (IS_ERR(req))
570 		goto out;
571 	dump_encrypted_data(epayload, encrypted_datalen);
572 
573 	sg_init_table(sg_in, 1);
574 	sg_init_table(sg_out, 2);
575 	sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
576 	sg_set_buf(&sg_out[0], epayload->decrypted_data,
577 		   epayload->decrypted_datalen);
578 	sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
579 
580 	memcpy(iv, epayload->iv, sizeof(iv));
581 	skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
582 	ret = crypto_skcipher_decrypt(req);
583 	tfm = crypto_skcipher_reqtfm(req);
584 	skcipher_request_free(req);
585 	crypto_free_skcipher(tfm);
586 	if (ret < 0)
587 		goto out;
588 	dump_decrypted_data(epayload);
589 out:
590 	kfree(pad);
591 	return ret;
592 }
593 
594 /* Allocate memory for decrypted key and datablob. */
595 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
596 							 const char *format,
597 							 const char *master_desc,
598 							 const char *datalen)
599 {
600 	struct encrypted_key_payload *epayload = NULL;
601 	unsigned short datablob_len;
602 	unsigned short decrypted_datalen;
603 	unsigned short payload_datalen;
604 	unsigned int encrypted_datalen;
605 	unsigned int format_len;
606 	long dlen;
607 	int ret;
608 
609 	ret = kstrtol(datalen, 10, &dlen);
610 	if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
611 		return ERR_PTR(-EINVAL);
612 
613 	format_len = (!format) ? strlen(key_format_default) : strlen(format);
614 	decrypted_datalen = dlen;
615 	payload_datalen = decrypted_datalen;
616 	if (format) {
617 		if (!strcmp(format, key_format_ecryptfs)) {
618 			if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
619 				pr_err("encrypted_key: keylen for the ecryptfs format must be equal to %d bytes\n",
620 					ECRYPTFS_MAX_KEY_BYTES);
621 				return ERR_PTR(-EINVAL);
622 			}
623 			decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
624 			payload_datalen = sizeof(struct ecryptfs_auth_tok);
625 		} else if (!strcmp(format, key_format_enc32)) {
626 			if (decrypted_datalen != KEY_ENC32_PAYLOAD_LEN) {
627 				pr_err("encrypted_key: enc32 key payload incorrect length: %d\n",
628 						decrypted_datalen);
629 				return ERR_PTR(-EINVAL);
630 			}
631 		}
632 	}
633 
634 	encrypted_datalen = roundup(decrypted_datalen, blksize);
635 
636 	datablob_len = format_len + 1 + strlen(master_desc) + 1
637 	    + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
638 
639 	ret = key_payload_reserve(key, payload_datalen + datablob_len
640 				  + HASH_SIZE + 1);
641 	if (ret < 0)
642 		return ERR_PTR(ret);
643 
644 	epayload = kzalloc(sizeof(*epayload) + payload_datalen +
645 			   datablob_len + HASH_SIZE + 1, GFP_KERNEL);
646 	if (!epayload)
647 		return ERR_PTR(-ENOMEM);
648 
649 	epayload->payload_datalen = payload_datalen;
650 	epayload->decrypted_datalen = decrypted_datalen;
651 	epayload->datablob_len = datablob_len;
652 	return epayload;
653 }
654 
655 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
656 				 const char *format, const char *hex_encoded_iv)
657 {
658 	struct key *mkey;
659 	u8 derived_key[HASH_SIZE];
660 	const u8 *master_key;
661 	u8 *hmac;
662 	const char *hex_encoded_data;
663 	unsigned int encrypted_datalen;
664 	size_t master_keylen;
665 	size_t asciilen;
666 	int ret;
667 
668 	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
669 	asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
670 	if (strlen(hex_encoded_iv) != asciilen)
671 		return -EINVAL;
672 
673 	hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
674 	ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
675 	if (ret < 0)
676 		return -EINVAL;
677 	ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
678 		      encrypted_datalen);
679 	if (ret < 0)
680 		return -EINVAL;
681 
682 	hmac = epayload->format + epayload->datablob_len;
683 	ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
684 		      HASH_SIZE);
685 	if (ret < 0)
686 		return -EINVAL;
687 
688 	mkey = request_master_key(epayload, &master_key, &master_keylen);
689 	if (IS_ERR(mkey))
690 		return PTR_ERR(mkey);
691 
692 	ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
693 	if (ret < 0) {
694 		pr_err("encrypted_key: bad hmac (%d)\n", ret);
695 		goto out;
696 	}
697 
698 	ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
699 	if (ret < 0)
700 		goto out;
701 
702 	ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
703 	if (ret < 0)
704 		pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
705 out:
706 	up_read(&mkey->sem);
707 	key_put(mkey);
708 	memzero_explicit(derived_key, sizeof(derived_key));
709 	return ret;
710 }
711 
712 static void __ekey_init(struct encrypted_key_payload *epayload,
713 			const char *format, const char *master_desc,
714 			const char *datalen)
715 {
716 	unsigned int format_len;
717 
718 	format_len = (!format) ? strlen(key_format_default) : strlen(format);
719 	epayload->format = epayload->payload_data + epayload->payload_datalen;
720 	epayload->master_desc = epayload->format + format_len + 1;
721 	epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
722 	epayload->iv = epayload->datalen + strlen(datalen) + 1;
723 	epayload->encrypted_data = epayload->iv + ivsize + 1;
724 	epayload->decrypted_data = epayload->payload_data;
725 
726 	if (!format)
727 		memcpy(epayload->format, key_format_default, format_len);
728 	else {
729 		if (!strcmp(format, key_format_ecryptfs))
730 			epayload->decrypted_data =
731 				ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
732 
733 		memcpy(epayload->format, format, format_len);
734 	}
735 
736 	memcpy(epayload->master_desc, master_desc, strlen(master_desc));
737 	memcpy(epayload->datalen, datalen, strlen(datalen));
738 }
739 
740 /*
741  * encrypted_init - initialize an encrypted key
742  *
743  * For a new key, use a random number for both the iv and data
744  * itself.  For an old key, decrypt the hex encoded data.
745  */
746 static int encrypted_init(struct encrypted_key_payload *epayload,
747 			  const char *key_desc, const char *format,
748 			  const char *master_desc, const char *datalen,
749 			  const char *hex_encoded_iv)
750 {
751 	int ret = 0;
752 
753 	if (format && !strcmp(format, key_format_ecryptfs)) {
754 		ret = valid_ecryptfs_desc(key_desc);
755 		if (ret < 0)
756 			return ret;
757 
758 		ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
759 				       key_desc);
760 	}
761 
762 	__ekey_init(epayload, format, master_desc, datalen);
763 	if (!hex_encoded_iv) {
764 		get_random_bytes(epayload->iv, ivsize);
765 
766 		get_random_bytes(epayload->decrypted_data,
767 				 epayload->decrypted_datalen);
768 	} else
769 		ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
770 	return ret;
771 }
772 
773 /*
774  * encrypted_instantiate - instantiate an encrypted key
775  *
776  * Decrypt an existing encrypted datablob or create a new encrypted key
777  * based on a kernel random number.
778  *
779  * On success, return 0. Otherwise return errno.
780  */
781 static int encrypted_instantiate(struct key *key,
782 				 struct key_preparsed_payload *prep)
783 {
784 	struct encrypted_key_payload *epayload = NULL;
785 	char *datablob = NULL;
786 	const char *format = NULL;
787 	char *master_desc = NULL;
788 	char *decrypted_datalen = NULL;
789 	char *hex_encoded_iv = NULL;
790 	size_t datalen = prep->datalen;
791 	int ret;
792 
793 	if (datalen <= 0 || datalen > 32767 || !prep->data)
794 		return -EINVAL;
795 
796 	datablob = kmalloc(datalen + 1, GFP_KERNEL);
797 	if (!datablob)
798 		return -ENOMEM;
799 	datablob[datalen] = 0;
800 	memcpy(datablob, prep->data, datalen);
801 	ret = datablob_parse(datablob, &format, &master_desc,
802 			     &decrypted_datalen, &hex_encoded_iv);
803 	if (ret < 0)
804 		goto out;
805 
806 	epayload = encrypted_key_alloc(key, format, master_desc,
807 				       decrypted_datalen);
808 	if (IS_ERR(epayload)) {
809 		ret = PTR_ERR(epayload);
810 		goto out;
811 	}
812 	ret = encrypted_init(epayload, key->description, format, master_desc,
813 			     decrypted_datalen, hex_encoded_iv);
814 	if (ret < 0) {
815 		kfree_sensitive(epayload);
816 		goto out;
817 	}
818 
819 	rcu_assign_keypointer(key, epayload);
820 out:
821 	kfree_sensitive(datablob);
822 	return ret;
823 }
824 
825 static void encrypted_rcu_free(struct rcu_head *rcu)
826 {
827 	struct encrypted_key_payload *epayload;
828 
829 	epayload = container_of(rcu, struct encrypted_key_payload, rcu);
830 	kfree_sensitive(epayload);
831 }
832 
833 /*
834  * encrypted_update - update the master key description
835  *
836  * Change the master key description for an existing encrypted key.
837  * The next read will return an encrypted datablob using the new
838  * master key description.
839  *
840  * On success, return 0. Otherwise return errno.
841  */
842 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
843 {
844 	struct encrypted_key_payload *epayload = key->payload.data[0];
845 	struct encrypted_key_payload *new_epayload;
846 	char *buf;
847 	char *new_master_desc = NULL;
848 	const char *format = NULL;
849 	size_t datalen = prep->datalen;
850 	int ret = 0;
851 
852 	if (key_is_negative(key))
853 		return -ENOKEY;
854 	if (datalen <= 0 || datalen > 32767 || !prep->data)
855 		return -EINVAL;
856 
857 	buf = kmalloc(datalen + 1, GFP_KERNEL);
858 	if (!buf)
859 		return -ENOMEM;
860 
861 	buf[datalen] = 0;
862 	memcpy(buf, prep->data, datalen);
863 	ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
864 	if (ret < 0)
865 		goto out;
866 
867 	ret = valid_master_desc(new_master_desc, epayload->master_desc);
868 	if (ret < 0)
869 		goto out;
870 
871 	new_epayload = encrypted_key_alloc(key, epayload->format,
872 					   new_master_desc, epayload->datalen);
873 	if (IS_ERR(new_epayload)) {
874 		ret = PTR_ERR(new_epayload);
875 		goto out;
876 	}
877 
878 	__ekey_init(new_epayload, epayload->format, new_master_desc,
879 		    epayload->datalen);
880 
881 	memcpy(new_epayload->iv, epayload->iv, ivsize);
882 	memcpy(new_epayload->payload_data, epayload->payload_data,
883 	       epayload->payload_datalen);
884 
885 	rcu_assign_keypointer(key, new_epayload);
886 	call_rcu(&epayload->rcu, encrypted_rcu_free);
887 out:
888 	kfree_sensitive(buf);
889 	return ret;
890 }
891 
892 /*
893  * encrypted_read - format and copy out the encrypted data
894  *
895  * The resulting datablob format is:
896  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
897  *
898  * On success, return to userspace the encrypted key datablob size.
899  */
900 static long encrypted_read(const struct key *key, char *buffer,
901 			   size_t buflen)
902 {
903 	struct encrypted_key_payload *epayload;
904 	struct key *mkey;
905 	const u8 *master_key;
906 	size_t master_keylen;
907 	char derived_key[HASH_SIZE];
908 	char *ascii_buf;
909 	size_t asciiblob_len;
910 	int ret;
911 
912 	epayload = dereference_key_locked(key);
913 
914 	/* returns the hex encoded iv, encrypted-data, and hmac as ascii */
915 	asciiblob_len = epayload->datablob_len + ivsize + 1
916 	    + roundup(epayload->decrypted_datalen, blksize)
917 	    + (HASH_SIZE * 2);
918 
919 	if (!buffer || buflen < asciiblob_len)
920 		return asciiblob_len;
921 
922 	mkey = request_master_key(epayload, &master_key, &master_keylen);
923 	if (IS_ERR(mkey))
924 		return PTR_ERR(mkey);
925 
926 	ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
927 	if (ret < 0)
928 		goto out;
929 
930 	ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
931 	if (ret < 0)
932 		goto out;
933 
934 	ret = datablob_hmac_append(epayload, master_key, master_keylen);
935 	if (ret < 0)
936 		goto out;
937 
938 	ascii_buf = datablob_format(epayload, asciiblob_len);
939 	if (!ascii_buf) {
940 		ret = -ENOMEM;
941 		goto out;
942 	}
943 
944 	up_read(&mkey->sem);
945 	key_put(mkey);
946 	memzero_explicit(derived_key, sizeof(derived_key));
947 
948 	memcpy(buffer, ascii_buf, asciiblob_len);
949 	kfree_sensitive(ascii_buf);
950 
951 	return asciiblob_len;
952 out:
953 	up_read(&mkey->sem);
954 	key_put(mkey);
955 	memzero_explicit(derived_key, sizeof(derived_key));
956 	return ret;
957 }
958 
959 /*
960  * encrypted_destroy - clear and free the key's payload
961  */
962 static void encrypted_destroy(struct key *key)
963 {
964 	kfree_sensitive(key->payload.data[0]);
965 }
966 
967 struct key_type key_type_encrypted = {
968 	.name = "encrypted",
969 	.instantiate = encrypted_instantiate,
970 	.update = encrypted_update,
971 	.destroy = encrypted_destroy,
972 	.describe = user_describe,
973 	.read = encrypted_read,
974 };
975 EXPORT_SYMBOL_GPL(key_type_encrypted);
976 
977 static int __init init_encrypted(void)
978 {
979 	int ret;
980 
981 	hash_tfm = crypto_alloc_shash(hash_alg, 0, 0);
982 	if (IS_ERR(hash_tfm)) {
983 		pr_err("encrypted_key: can't allocate %s transform: %ld\n",
984 		       hash_alg, PTR_ERR(hash_tfm));
985 		return PTR_ERR(hash_tfm);
986 	}
987 
988 	ret = aes_get_sizes();
989 	if (ret < 0)
990 		goto out;
991 	ret = register_key_type(&key_type_encrypted);
992 	if (ret < 0)
993 		goto out;
994 	return 0;
995 out:
996 	crypto_free_shash(hash_tfm);
997 	return ret;
998 
999 }
1000 
1001 static void __exit cleanup_encrypted(void)
1002 {
1003 	crypto_free_shash(hash_tfm);
1004 	unregister_key_type(&key_type_encrypted);
1005 }
1006 
1007 late_initcall(init_encrypted);
1008 module_exit(cleanup_encrypted);
1009 
1010 MODULE_LICENSE("GPL");
1011