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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
38static const char KEY_TRUSTED_PREFIX[] = "trusted:";
39static const char KEY_USER_PREFIX[] = "user:";
40static const char hash_alg[] = "sha256";
41static const char hmac_alg[] = "hmac(sha256)";
42static const char blkcipher_alg[] = "cbc(aes)";
43static const char key_format_default[] = "default";
44static const char key_format_ecryptfs[] = "ecryptfs";
45static const char key_format_enc32[] = "enc32";
46static unsigned int ivsize;
47static 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
57static struct crypto_shash *hash_tfm;
58
59enum {
60 Opt_new, Opt_load, Opt_update, Opt_err
61};
62
63enum {
64 Opt_default, Opt_ecryptfs, Opt_enc32, Opt_error
65};
66
67static 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
74static const match_table_t key_tokens = {
75 {Opt_new, "new"},
76 {Opt_load, "load"},
77 {Opt_update, "update"},
78 {Opt_err, NULL}
79};
80
81static bool user_decrypted_data = IS_ENABLED(CONFIG_USER_DECRYPTED_DATA);
82module_param(user_decrypted_data, bool, 0);
83MODULE_PARM_DESC(user_decrypted_data,
84 "Allow instantiation of encrypted keys using provided decrypted data");
85
86static int aes_get_sizes(void)
87{
88 struct crypto_skcipher *tfm;
89
90 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
91 if (IS_ERR(tfm)) {
92 pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
93 PTR_ERR(tfm));
94 return PTR_ERR(tfm);
95 }
96 ivsize = crypto_skcipher_ivsize(tfm);
97 blksize = crypto_skcipher_blocksize(tfm);
98 crypto_free_skcipher(tfm);
99 return 0;
100}
101
102/*
103 * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
104 *
105 * The description of a encrypted key with format 'ecryptfs' must contain
106 * exactly 16 hexadecimal characters.
107 *
108 */
109static int valid_ecryptfs_desc(const char *ecryptfs_desc)
110{
111 int i;
112
113 if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) {
114 pr_err("encrypted_key: key description must be %d hexadecimal "
115 "characters long\n", KEY_ECRYPTFS_DESC_LEN);
116 return -EINVAL;
117 }
118
119 for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) {
120 if (!isxdigit(ecryptfs_desc[i])) {
121 pr_err("encrypted_key: key description must contain "
122 "only hexadecimal characters\n");
123 return -EINVAL;
124 }
125 }
126
127 return 0;
128}
129
130/*
131 * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
132 *
133 * key-type:= "trusted:" | "user:"
134 * desc:= master-key description
135 *
136 * Verify that 'key-type' is valid and that 'desc' exists. On key update,
137 * only the master key description is permitted to change, not the key-type.
138 * The key-type remains constant.
139 *
140 * On success returns 0, otherwise -EINVAL.
141 */
142static int valid_master_desc(const char *new_desc, const char *orig_desc)
143{
144 int prefix_len;
145
146 if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
147 prefix_len = KEY_TRUSTED_PREFIX_LEN;
148 else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
149 prefix_len = KEY_USER_PREFIX_LEN;
150 else
151 return -EINVAL;
152
153 if (!new_desc[prefix_len])
154 return -EINVAL;
155
156 if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
157 return -EINVAL;
158
159 return 0;
160}
161
162/*
163 * datablob_parse - parse the keyctl data
164 *
165 * datablob format:
166 * new [<format>] <master-key name> <decrypted data length> [<decrypted data>]
167 * load [<format>] <master-key name> <decrypted data length>
168 * <encrypted iv + data>
169 * update <new-master-key name>
170 *
171 * Tokenizes a copy of the keyctl data, returning a pointer to each token,
172 * which is null terminated.
173 *
174 * On success returns 0, otherwise -EINVAL.
175 */
176static int datablob_parse(char *datablob, const char **format,
177 char **master_desc, char **decrypted_datalen,
178 char **hex_encoded_iv, char **decrypted_data)
179{
180 substring_t args[MAX_OPT_ARGS];
181 int ret = -EINVAL;
182 int key_cmd;
183 int key_format;
184 char *p, *keyword;
185
186 keyword = strsep(&datablob, " \t");
187 if (!keyword) {
188 pr_info("encrypted_key: insufficient parameters specified\n");
189 return ret;
190 }
191 key_cmd = match_token(keyword, key_tokens, args);
192
193 /* Get optional format: default | ecryptfs */
194 p = strsep(&datablob, " \t");
195 if (!p) {
196 pr_err("encrypted_key: insufficient parameters specified\n");
197 return ret;
198 }
199
200 key_format = match_token(p, key_format_tokens, args);
201 switch (key_format) {
202 case Opt_ecryptfs:
203 case Opt_enc32:
204 case Opt_default:
205 *format = p;
206 *master_desc = strsep(&datablob, " \t");
207 break;
208 case Opt_error:
209 *master_desc = p;
210 break;
211 }
212
213 if (!*master_desc) {
214 pr_info("encrypted_key: master key parameter is missing\n");
215 goto out;
216 }
217
218 if (valid_master_desc(*master_desc, NULL) < 0) {
219 pr_info("encrypted_key: master key parameter \'%s\' "
220 "is invalid\n", *master_desc);
221 goto out;
222 }
223
224 if (decrypted_datalen) {
225 *decrypted_datalen = strsep(&datablob, " \t");
226 if (!*decrypted_datalen) {
227 pr_info("encrypted_key: keylen parameter is missing\n");
228 goto out;
229 }
230 }
231
232 switch (key_cmd) {
233 case Opt_new:
234 if (!decrypted_datalen) {
235 pr_info("encrypted_key: keyword \'%s\' not allowed "
236 "when called from .update method\n", keyword);
237 break;
238 }
239 *decrypted_data = strsep(&datablob, " \t");
240 ret = 0;
241 break;
242 case Opt_load:
243 if (!decrypted_datalen) {
244 pr_info("encrypted_key: keyword \'%s\' not allowed "
245 "when called from .update method\n", keyword);
246 break;
247 }
248 *hex_encoded_iv = strsep(&datablob, " \t");
249 if (!*hex_encoded_iv) {
250 pr_info("encrypted_key: hex blob is missing\n");
251 break;
252 }
253 ret = 0;
254 break;
255 case Opt_update:
256 if (decrypted_datalen) {
257 pr_info("encrypted_key: keyword \'%s\' not allowed "
258 "when called from .instantiate method\n",
259 keyword);
260 break;
261 }
262 ret = 0;
263 break;
264 case Opt_err:
265 pr_info("encrypted_key: keyword \'%s\' not recognized\n",
266 keyword);
267 break;
268 }
269out:
270 return ret;
271}
272
273/*
274 * datablob_format - format as an ascii string, before copying to userspace
275 */
276static char *datablob_format(struct encrypted_key_payload *epayload,
277 size_t asciiblob_len)
278{
279 char *ascii_buf, *bufp;
280 u8 *iv = epayload->iv;
281 int len;
282 int i;
283
284 ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
285 if (!ascii_buf)
286 goto out;
287
288 ascii_buf[asciiblob_len] = '\0';
289
290 /* copy datablob master_desc and datalen strings */
291 len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
292 epayload->master_desc, epayload->datalen);
293
294 /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
295 bufp = &ascii_buf[len];
296 for (i = 0; i < (asciiblob_len - len) / 2; i++)
297 bufp = hex_byte_pack(bufp, iv[i]);
298out:
299 return ascii_buf;
300}
301
302/*
303 * request_user_key - request the user key
304 *
305 * Use a user provided key to encrypt/decrypt an encrypted-key.
306 */
307static struct key *request_user_key(const char *master_desc, const u8 **master_key,
308 size_t *master_keylen)
309{
310 const struct user_key_payload *upayload;
311 struct key *ukey;
312
313 ukey = request_key(&key_type_user, master_desc, NULL);
314 if (IS_ERR(ukey))
315 goto error;
316
317 down_read(&ukey->sem);
318 upayload = user_key_payload_locked(ukey);
319 if (!upayload) {
320 /* key was revoked before we acquired its semaphore */
321 up_read(&ukey->sem);
322 key_put(ukey);
323 ukey = ERR_PTR(-EKEYREVOKED);
324 goto error;
325 }
326 *master_key = upayload->data;
327 *master_keylen = upayload->datalen;
328error:
329 return ukey;
330}
331
332static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
333 const u8 *buf, unsigned int buflen)
334{
335 struct crypto_shash *tfm;
336 int err;
337
338 tfm = crypto_alloc_shash(hmac_alg, 0, 0);
339 if (IS_ERR(tfm)) {
340 pr_err("encrypted_key: can't alloc %s transform: %ld\n",
341 hmac_alg, PTR_ERR(tfm));
342 return PTR_ERR(tfm);
343 }
344
345 err = crypto_shash_setkey(tfm, key, keylen);
346 if (!err)
347 err = crypto_shash_tfm_digest(tfm, buf, buflen, digest);
348 crypto_free_shash(tfm);
349 return err;
350}
351
352enum derived_key_type { ENC_KEY, AUTH_KEY };
353
354/* Derive authentication/encryption key from trusted key */
355static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
356 const u8 *master_key, size_t master_keylen)
357{
358 u8 *derived_buf;
359 unsigned int derived_buf_len;
360 int ret;
361
362 derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
363 if (derived_buf_len < HASH_SIZE)
364 derived_buf_len = HASH_SIZE;
365
366 derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
367 if (!derived_buf)
368 return -ENOMEM;
369
370 if (key_type)
371 strcpy(derived_buf, "AUTH_KEY");
372 else
373 strcpy(derived_buf, "ENC_KEY");
374
375 memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
376 master_keylen);
377 ret = crypto_shash_tfm_digest(hash_tfm, derived_buf, derived_buf_len,
378 derived_key);
379 kfree_sensitive(derived_buf);
380 return ret;
381}
382
383static struct skcipher_request *init_skcipher_req(const u8 *key,
384 unsigned int key_len)
385{
386 struct skcipher_request *req;
387 struct crypto_skcipher *tfm;
388 int ret;
389
390 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
391 if (IS_ERR(tfm)) {
392 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
393 blkcipher_alg, PTR_ERR(tfm));
394 return ERR_CAST(tfm);
395 }
396
397 ret = crypto_skcipher_setkey(tfm, key, key_len);
398 if (ret < 0) {
399 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
400 crypto_free_skcipher(tfm);
401 return ERR_PTR(ret);
402 }
403
404 req = skcipher_request_alloc(tfm, GFP_KERNEL);
405 if (!req) {
406 pr_err("encrypted_key: failed to allocate request for %s\n",
407 blkcipher_alg);
408 crypto_free_skcipher(tfm);
409 return ERR_PTR(-ENOMEM);
410 }
411
412 skcipher_request_set_callback(req, 0, NULL, NULL);
413 return req;
414}
415
416static struct key *request_master_key(struct encrypted_key_payload *epayload,
417 const u8 **master_key, size_t *master_keylen)
418{
419 struct key *mkey = ERR_PTR(-EINVAL);
420
421 if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
422 KEY_TRUSTED_PREFIX_LEN)) {
423 mkey = request_trusted_key(epayload->master_desc +
424 KEY_TRUSTED_PREFIX_LEN,
425 master_key, master_keylen);
426 } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
427 KEY_USER_PREFIX_LEN)) {
428 mkey = request_user_key(epayload->master_desc +
429 KEY_USER_PREFIX_LEN,
430 master_key, master_keylen);
431 } else
432 goto out;
433
434 if (IS_ERR(mkey)) {
435 int ret = PTR_ERR(mkey);
436
437 if (ret == -ENOTSUPP)
438 pr_info("encrypted_key: key %s not supported",
439 epayload->master_desc);
440 else
441 pr_info("encrypted_key: key %s not found",
442 epayload->master_desc);
443 goto out;
444 }
445
446 dump_master_key(*master_key, *master_keylen);
447out:
448 return mkey;
449}
450
451/* Before returning data to userspace, encrypt decrypted data. */
452static int derived_key_encrypt(struct encrypted_key_payload *epayload,
453 const u8 *derived_key,
454 unsigned int derived_keylen)
455{
456 struct scatterlist sg_in[2];
457 struct scatterlist sg_out[1];
458 struct crypto_skcipher *tfm;
459 struct skcipher_request *req;
460 unsigned int encrypted_datalen;
461 u8 iv[AES_BLOCK_SIZE];
462 int ret;
463
464 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
465
466 req = init_skcipher_req(derived_key, derived_keylen);
467 ret = PTR_ERR(req);
468 if (IS_ERR(req))
469 goto out;
470 dump_decrypted_data(epayload);
471
472 sg_init_table(sg_in, 2);
473 sg_set_buf(&sg_in[0], epayload->decrypted_data,
474 epayload->decrypted_datalen);
475 sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
476
477 sg_init_table(sg_out, 1);
478 sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
479
480 memcpy(iv, epayload->iv, sizeof(iv));
481 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
482 ret = crypto_skcipher_encrypt(req);
483 tfm = crypto_skcipher_reqtfm(req);
484 skcipher_request_free(req);
485 crypto_free_skcipher(tfm);
486 if (ret < 0)
487 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
488 else
489 dump_encrypted_data(epayload, encrypted_datalen);
490out:
491 return ret;
492}
493
494static int datablob_hmac_append(struct encrypted_key_payload *epayload,
495 const u8 *master_key, size_t master_keylen)
496{
497 u8 derived_key[HASH_SIZE];
498 u8 *digest;
499 int ret;
500
501 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
502 if (ret < 0)
503 goto out;
504
505 digest = epayload->format + epayload->datablob_len;
506 ret = calc_hmac(digest, derived_key, sizeof derived_key,
507 epayload->format, epayload->datablob_len);
508 if (!ret)
509 dump_hmac(NULL, digest, HASH_SIZE);
510out:
511 memzero_explicit(derived_key, sizeof(derived_key));
512 return ret;
513}
514
515/* verify HMAC before decrypting encrypted key */
516static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
517 const u8 *format, const u8 *master_key,
518 size_t master_keylen)
519{
520 u8 derived_key[HASH_SIZE];
521 u8 digest[HASH_SIZE];
522 int ret;
523 char *p;
524 unsigned short len;
525
526 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
527 if (ret < 0)
528 goto out;
529
530 len = epayload->datablob_len;
531 if (!format) {
532 p = epayload->master_desc;
533 len -= strlen(epayload->format) + 1;
534 } else
535 p = epayload->format;
536
537 ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
538 if (ret < 0)
539 goto out;
540 ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
541 sizeof(digest));
542 if (ret) {
543 ret = -EINVAL;
544 dump_hmac("datablob",
545 epayload->format + epayload->datablob_len,
546 HASH_SIZE);
547 dump_hmac("calc", digest, HASH_SIZE);
548 }
549out:
550 memzero_explicit(derived_key, sizeof(derived_key));
551 return ret;
552}
553
554static int derived_key_decrypt(struct encrypted_key_payload *epayload,
555 const u8 *derived_key,
556 unsigned int derived_keylen)
557{
558 struct scatterlist sg_in[1];
559 struct scatterlist sg_out[2];
560 struct crypto_skcipher *tfm;
561 struct skcipher_request *req;
562 unsigned int encrypted_datalen;
563 u8 iv[AES_BLOCK_SIZE];
564 u8 *pad;
565 int ret;
566
567 /* Throwaway buffer to hold the unused zero padding at the end */
568 pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
569 if (!pad)
570 return -ENOMEM;
571
572 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
573 req = init_skcipher_req(derived_key, derived_keylen);
574 ret = PTR_ERR(req);
575 if (IS_ERR(req))
576 goto out;
577 dump_encrypted_data(epayload, encrypted_datalen);
578
579 sg_init_table(sg_in, 1);
580 sg_init_table(sg_out, 2);
581 sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
582 sg_set_buf(&sg_out[0], epayload->decrypted_data,
583 epayload->decrypted_datalen);
584 sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
585
586 memcpy(iv, epayload->iv, sizeof(iv));
587 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
588 ret = crypto_skcipher_decrypt(req);
589 tfm = crypto_skcipher_reqtfm(req);
590 skcipher_request_free(req);
591 crypto_free_skcipher(tfm);
592 if (ret < 0)
593 goto out;
594 dump_decrypted_data(epayload);
595out:
596 kfree(pad);
597 return ret;
598}
599
600/* Allocate memory for decrypted key and datablob. */
601static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
602 const char *format,
603 const char *master_desc,
604 const char *datalen,
605 const char *decrypted_data)
606{
607 struct encrypted_key_payload *epayload = NULL;
608 unsigned short datablob_len;
609 unsigned short decrypted_datalen;
610 unsigned short payload_datalen;
611 unsigned int encrypted_datalen;
612 unsigned int format_len;
613 long dlen;
614 int i;
615 int ret;
616
617 ret = kstrtol(datalen, 10, &dlen);
618 if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
619 return ERR_PTR(-EINVAL);
620
621 format_len = (!format) ? strlen(key_format_default) : strlen(format);
622 decrypted_datalen = dlen;
623 payload_datalen = decrypted_datalen;
624
625 if (decrypted_data) {
626 if (!user_decrypted_data) {
627 pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n");
628 return ERR_PTR(-EINVAL);
629 }
630 if (strlen(decrypted_data) != decrypted_datalen * 2) {
631 pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n");
632 return ERR_PTR(-EINVAL);
633 }
634 for (i = 0; i < strlen(decrypted_data); i++) {
635 if (!isxdigit(decrypted_data[i])) {
636 pr_err("encrypted key: decrypted data provided must contain only hexadecimal characters\n");
637 return ERR_PTR(-EINVAL);
638 }
639 }
640 }
641
642 if (format) {
643 if (!strcmp(format, key_format_ecryptfs)) {
644 if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
645 pr_err("encrypted_key: keylen for the ecryptfs format must be equal to %d bytes\n",
646 ECRYPTFS_MAX_KEY_BYTES);
647 return ERR_PTR(-EINVAL);
648 }
649 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
650 payload_datalen = sizeof(struct ecryptfs_auth_tok);
651 } else if (!strcmp(format, key_format_enc32)) {
652 if (decrypted_datalen != KEY_ENC32_PAYLOAD_LEN) {
653 pr_err("encrypted_key: enc32 key payload incorrect length: %d\n",
654 decrypted_datalen);
655 return ERR_PTR(-EINVAL);
656 }
657 }
658 }
659
660 encrypted_datalen = roundup(decrypted_datalen, blksize);
661
662 datablob_len = format_len + 1 + strlen(master_desc) + 1
663 + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
664
665 ret = key_payload_reserve(key, payload_datalen + datablob_len
666 + HASH_SIZE + 1);
667 if (ret < 0)
668 return ERR_PTR(ret);
669
670 epayload = kzalloc(sizeof(*epayload) + payload_datalen +
671 datablob_len + HASH_SIZE + 1, GFP_KERNEL);
672 if (!epayload)
673 return ERR_PTR(-ENOMEM);
674
675 epayload->payload_datalen = payload_datalen;
676 epayload->decrypted_datalen = decrypted_datalen;
677 epayload->datablob_len = datablob_len;
678 return epayload;
679}
680
681static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
682 const char *format, const char *hex_encoded_iv)
683{
684 struct key *mkey;
685 u8 derived_key[HASH_SIZE];
686 const u8 *master_key;
687 u8 *hmac;
688 const char *hex_encoded_data;
689 unsigned int encrypted_datalen;
690 size_t master_keylen;
691 size_t asciilen;
692 int ret;
693
694 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
695 asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
696 if (strlen(hex_encoded_iv) != asciilen)
697 return -EINVAL;
698
699 hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
700 ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
701 if (ret < 0)
702 return -EINVAL;
703 ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
704 encrypted_datalen);
705 if (ret < 0)
706 return -EINVAL;
707
708 hmac = epayload->format + epayload->datablob_len;
709 ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
710 HASH_SIZE);
711 if (ret < 0)
712 return -EINVAL;
713
714 mkey = request_master_key(epayload, &master_key, &master_keylen);
715 if (IS_ERR(mkey))
716 return PTR_ERR(mkey);
717
718 ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
719 if (ret < 0) {
720 pr_err("encrypted_key: bad hmac (%d)\n", ret);
721 goto out;
722 }
723
724 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
725 if (ret < 0)
726 goto out;
727
728 ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
729 if (ret < 0)
730 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
731out:
732 up_read(&mkey->sem);
733 key_put(mkey);
734 memzero_explicit(derived_key, sizeof(derived_key));
735 return ret;
736}
737
738static void __ekey_init(struct encrypted_key_payload *epayload,
739 const char *format, const char *master_desc,
740 const char *datalen)
741{
742 unsigned int format_len;
743
744 format_len = (!format) ? strlen(key_format_default) : strlen(format);
745 epayload->format = epayload->payload_data + epayload->payload_datalen;
746 epayload->master_desc = epayload->format + format_len + 1;
747 epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
748 epayload->iv = epayload->datalen + strlen(datalen) + 1;
749 epayload->encrypted_data = epayload->iv + ivsize + 1;
750 epayload->decrypted_data = epayload->payload_data;
751
752 if (!format)
753 memcpy(epayload->format, key_format_default, format_len);
754 else {
755 if (!strcmp(format, key_format_ecryptfs))
756 epayload->decrypted_data =
757 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
758
759 memcpy(epayload->format, format, format_len);
760 }
761
762 memcpy(epayload->master_desc, master_desc, strlen(master_desc));
763 memcpy(epayload->datalen, datalen, strlen(datalen));
764}
765
766/*
767 * encrypted_init - initialize an encrypted key
768 *
769 * For a new key, use either a random number or user-provided decrypted data in
770 * case it is provided. A random number is used for the iv in both cases. For
771 * an old key, decrypt the hex encoded data.
772 */
773static int encrypted_init(struct encrypted_key_payload *epayload,
774 const char *key_desc, const char *format,
775 const char *master_desc, const char *datalen,
776 const char *hex_encoded_iv, const char *decrypted_data)
777{
778 int ret = 0;
779
780 if (format && !strcmp(format, key_format_ecryptfs)) {
781 ret = valid_ecryptfs_desc(key_desc);
782 if (ret < 0)
783 return ret;
784
785 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
786 key_desc);
787 }
788
789 __ekey_init(epayload, format, master_desc, datalen);
790 if (hex_encoded_iv) {
791 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
792 } else if (decrypted_data) {
793 get_random_bytes(epayload->iv, ivsize);
794 ret = hex2bin(epayload->decrypted_data, decrypted_data,
795 epayload->decrypted_datalen);
796 } else {
797 get_random_bytes(epayload->iv, ivsize);
798 get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen);
799 }
800 return ret;
801}
802
803/*
804 * encrypted_instantiate - instantiate an encrypted key
805 *
806 * Instantiates the key:
807 * - by decrypting an existing encrypted datablob, or
808 * - by creating a new encrypted key based on a kernel random number, or
809 * - using provided decrypted data.
810 *
811 * On success, return 0. Otherwise return errno.
812 */
813static int encrypted_instantiate(struct key *key,
814 struct key_preparsed_payload *prep)
815{
816 struct encrypted_key_payload *epayload = NULL;
817 char *datablob = NULL;
818 const char *format = NULL;
819 char *master_desc = NULL;
820 char *decrypted_datalen = NULL;
821 char *hex_encoded_iv = NULL;
822 char *decrypted_data = NULL;
823 size_t datalen = prep->datalen;
824 int ret;
825
826 if (datalen <= 0 || datalen > 32767 || !prep->data)
827 return -EINVAL;
828
829 datablob = kmalloc(datalen + 1, GFP_KERNEL);
830 if (!datablob)
831 return -ENOMEM;
832 datablob[datalen] = 0;
833 memcpy(datablob, prep->data, datalen);
834 ret = datablob_parse(datablob, &format, &master_desc,
835 &decrypted_datalen, &hex_encoded_iv, &decrypted_data);
836 if (ret < 0)
837 goto out;
838
839 epayload = encrypted_key_alloc(key, format, master_desc,
840 decrypted_datalen, decrypted_data);
841 if (IS_ERR(epayload)) {
842 ret = PTR_ERR(epayload);
843 goto out;
844 }
845 ret = encrypted_init(epayload, key->description, format, master_desc,
846 decrypted_datalen, hex_encoded_iv, decrypted_data);
847 if (ret < 0) {
848 kfree_sensitive(epayload);
849 goto out;
850 }
851
852 rcu_assign_keypointer(key, epayload);
853out:
854 kfree_sensitive(datablob);
855 return ret;
856}
857
858static void encrypted_rcu_free(struct rcu_head *rcu)
859{
860 struct encrypted_key_payload *epayload;
861
862 epayload = container_of(rcu, struct encrypted_key_payload, rcu);
863 kfree_sensitive(epayload);
864}
865
866/*
867 * encrypted_update - update the master key description
868 *
869 * Change the master key description for an existing encrypted key.
870 * The next read will return an encrypted datablob using the new
871 * master key description.
872 *
873 * On success, return 0. Otherwise return errno.
874 */
875static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
876{
877 struct encrypted_key_payload *epayload = key->payload.data[0];
878 struct encrypted_key_payload *new_epayload;
879 char *buf;
880 char *new_master_desc = NULL;
881 const char *format = NULL;
882 size_t datalen = prep->datalen;
883 int ret = 0;
884
885 if (key_is_negative(key))
886 return -ENOKEY;
887 if (datalen <= 0 || datalen > 32767 || !prep->data)
888 return -EINVAL;
889
890 buf = kmalloc(datalen + 1, GFP_KERNEL);
891 if (!buf)
892 return -ENOMEM;
893
894 buf[datalen] = 0;
895 memcpy(buf, prep->data, datalen);
896 ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL, NULL);
897 if (ret < 0)
898 goto out;
899
900 ret = valid_master_desc(new_master_desc, epayload->master_desc);
901 if (ret < 0)
902 goto out;
903
904 new_epayload = encrypted_key_alloc(key, epayload->format,
905 new_master_desc, epayload->datalen, NULL);
906 if (IS_ERR(new_epayload)) {
907 ret = PTR_ERR(new_epayload);
908 goto out;
909 }
910
911 __ekey_init(new_epayload, epayload->format, new_master_desc,
912 epayload->datalen);
913
914 memcpy(new_epayload->iv, epayload->iv, ivsize);
915 memcpy(new_epayload->payload_data, epayload->payload_data,
916 epayload->payload_datalen);
917
918 rcu_assign_keypointer(key, new_epayload);
919 call_rcu(&epayload->rcu, encrypted_rcu_free);
920out:
921 kfree_sensitive(buf);
922 return ret;
923}
924
925/*
926 * encrypted_read - format and copy out the encrypted data
927 *
928 * The resulting datablob format is:
929 * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
930 *
931 * On success, return to userspace the encrypted key datablob size.
932 */
933static long encrypted_read(const struct key *key, char *buffer,
934 size_t buflen)
935{
936 struct encrypted_key_payload *epayload;
937 struct key *mkey;
938 const u8 *master_key;
939 size_t master_keylen;
940 char derived_key[HASH_SIZE];
941 char *ascii_buf;
942 size_t asciiblob_len;
943 int ret;
944
945 epayload = dereference_key_locked(key);
946
947 /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
948 asciiblob_len = epayload->datablob_len + ivsize + 1
949 + roundup(epayload->decrypted_datalen, blksize)
950 + (HASH_SIZE * 2);
951
952 if (!buffer || buflen < asciiblob_len)
953 return asciiblob_len;
954
955 mkey = request_master_key(epayload, &master_key, &master_keylen);
956 if (IS_ERR(mkey))
957 return PTR_ERR(mkey);
958
959 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
960 if (ret < 0)
961 goto out;
962
963 ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
964 if (ret < 0)
965 goto out;
966
967 ret = datablob_hmac_append(epayload, master_key, master_keylen);
968 if (ret < 0)
969 goto out;
970
971 ascii_buf = datablob_format(epayload, asciiblob_len);
972 if (!ascii_buf) {
973 ret = -ENOMEM;
974 goto out;
975 }
976
977 up_read(&mkey->sem);
978 key_put(mkey);
979 memzero_explicit(derived_key, sizeof(derived_key));
980
981 memcpy(buffer, ascii_buf, asciiblob_len);
982 kfree_sensitive(ascii_buf);
983
984 return asciiblob_len;
985out:
986 up_read(&mkey->sem);
987 key_put(mkey);
988 memzero_explicit(derived_key, sizeof(derived_key));
989 return ret;
990}
991
992/*
993 * encrypted_destroy - clear and free the key's payload
994 */
995static void encrypted_destroy(struct key *key)
996{
997 kfree_sensitive(key->payload.data[0]);
998}
999
1000struct key_type key_type_encrypted = {
1001 .name = "encrypted",
1002 .instantiate = encrypted_instantiate,
1003 .update = encrypted_update,
1004 .destroy = encrypted_destroy,
1005 .describe = user_describe,
1006 .read = encrypted_read,
1007};
1008EXPORT_SYMBOL_GPL(key_type_encrypted);
1009
1010static int __init init_encrypted(void)
1011{
1012 int ret;
1013
1014 hash_tfm = crypto_alloc_shash(hash_alg, 0, 0);
1015 if (IS_ERR(hash_tfm)) {
1016 pr_err("encrypted_key: can't allocate %s transform: %ld\n",
1017 hash_alg, PTR_ERR(hash_tfm));
1018 return PTR_ERR(hash_tfm);
1019 }
1020
1021 ret = aes_get_sizes();
1022 if (ret < 0)
1023 goto out;
1024 ret = register_key_type(&key_type_encrypted);
1025 if (ret < 0)
1026 goto out;
1027 return 0;
1028out:
1029 crypto_free_shash(hash_tfm);
1030 return ret;
1031
1032}
1033
1034static void __exit cleanup_encrypted(void)
1035{
1036 crypto_free_shash(hash_tfm);
1037 unregister_key_type(&key_type_encrypted);
1038}
1039
1040late_initcall(init_encrypted);
1041module_exit(cleanup_encrypted);
1042
1043MODULE_LICENSE("GPL");
1/*
2 * Copyright (C) 2010 IBM Corporation
3 * Copyright (C) 2010 Politecnico di Torino, Italy
4 * TORSEC group -- http://security.polito.it
5 *
6 * Authors:
7 * Mimi Zohar <zohar@us.ibm.com>
8 * Roberto Sassu <roberto.sassu@polito.it>
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation, version 2 of the License.
13 *
14 * See Documentation/security/keys/trusted-encrypted.rst
15 */
16
17#include <linux/uaccess.h>
18#include <linux/module.h>
19#include <linux/init.h>
20#include <linux/slab.h>
21#include <linux/parser.h>
22#include <linux/string.h>
23#include <linux/err.h>
24#include <keys/user-type.h>
25#include <keys/trusted-type.h>
26#include <keys/encrypted-type.h>
27#include <linux/key-type.h>
28#include <linux/random.h>
29#include <linux/rcupdate.h>
30#include <linux/scatterlist.h>
31#include <linux/ctype.h>
32#include <crypto/aes.h>
33#include <crypto/algapi.h>
34#include <crypto/hash.h>
35#include <crypto/sha.h>
36#include <crypto/skcipher.h>
37
38#include "encrypted.h"
39#include "ecryptfs_format.h"
40
41static const char KEY_TRUSTED_PREFIX[] = "trusted:";
42static const char KEY_USER_PREFIX[] = "user:";
43static const char hash_alg[] = "sha256";
44static const char hmac_alg[] = "hmac(sha256)";
45static const char blkcipher_alg[] = "cbc(aes)";
46static const char key_format_default[] = "default";
47static const char key_format_ecryptfs[] = "ecryptfs";
48static unsigned int ivsize;
49static int blksize;
50
51#define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
52#define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
53#define KEY_ECRYPTFS_DESC_LEN 16
54#define HASH_SIZE SHA256_DIGEST_SIZE
55#define MAX_DATA_SIZE 4096
56#define MIN_DATA_SIZE 20
57
58static struct crypto_shash *hash_tfm;
59
60enum {
61 Opt_err = -1, Opt_new, Opt_load, Opt_update
62};
63
64enum {
65 Opt_error = -1, Opt_default, Opt_ecryptfs
66};
67
68static const match_table_t key_format_tokens = {
69 {Opt_default, "default"},
70 {Opt_ecryptfs, "ecryptfs"},
71 {Opt_error, NULL}
72};
73
74static const match_table_t key_tokens = {
75 {Opt_new, "new"},
76 {Opt_load, "load"},
77 {Opt_update, "update"},
78 {Opt_err, NULL}
79};
80
81static 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 */
104static 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 */
137static 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 */
171static 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_default:
199 *format = p;
200 *master_desc = strsep(&datablob, " \t");
201 break;
202 case Opt_error:
203 *master_desc = p;
204 break;
205 }
206
207 if (!*master_desc) {
208 pr_info("encrypted_key: master key parameter is missing\n");
209 goto out;
210 }
211
212 if (valid_master_desc(*master_desc, NULL) < 0) {
213 pr_info("encrypted_key: master key parameter \'%s\' "
214 "is invalid\n", *master_desc);
215 goto out;
216 }
217
218 if (decrypted_datalen) {
219 *decrypted_datalen = strsep(&datablob, " \t");
220 if (!*decrypted_datalen) {
221 pr_info("encrypted_key: keylen parameter is missing\n");
222 goto out;
223 }
224 }
225
226 switch (key_cmd) {
227 case Opt_new:
228 if (!decrypted_datalen) {
229 pr_info("encrypted_key: keyword \'%s\' not allowed "
230 "when called from .update method\n", keyword);
231 break;
232 }
233 ret = 0;
234 break;
235 case Opt_load:
236 if (!decrypted_datalen) {
237 pr_info("encrypted_key: keyword \'%s\' not allowed "
238 "when called from .update method\n", keyword);
239 break;
240 }
241 *hex_encoded_iv = strsep(&datablob, " \t");
242 if (!*hex_encoded_iv) {
243 pr_info("encrypted_key: hex blob is missing\n");
244 break;
245 }
246 ret = 0;
247 break;
248 case Opt_update:
249 if (decrypted_datalen) {
250 pr_info("encrypted_key: keyword \'%s\' not allowed "
251 "when called from .instantiate method\n",
252 keyword);
253 break;
254 }
255 ret = 0;
256 break;
257 case Opt_err:
258 pr_info("encrypted_key: keyword \'%s\' not recognized\n",
259 keyword);
260 break;
261 }
262out:
263 return ret;
264}
265
266/*
267 * datablob_format - format as an ascii string, before copying to userspace
268 */
269static char *datablob_format(struct encrypted_key_payload *epayload,
270 size_t asciiblob_len)
271{
272 char *ascii_buf, *bufp;
273 u8 *iv = epayload->iv;
274 int len;
275 int i;
276
277 ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
278 if (!ascii_buf)
279 goto out;
280
281 ascii_buf[asciiblob_len] = '\0';
282
283 /* copy datablob master_desc and datalen strings */
284 len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
285 epayload->master_desc, epayload->datalen);
286
287 /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
288 bufp = &ascii_buf[len];
289 for (i = 0; i < (asciiblob_len - len) / 2; i++)
290 bufp = hex_byte_pack(bufp, iv[i]);
291out:
292 return ascii_buf;
293}
294
295/*
296 * request_user_key - request the user key
297 *
298 * Use a user provided key to encrypt/decrypt an encrypted-key.
299 */
300static struct key *request_user_key(const char *master_desc, const u8 **master_key,
301 size_t *master_keylen)
302{
303 const struct user_key_payload *upayload;
304 struct key *ukey;
305
306 ukey = request_key(&key_type_user, master_desc, NULL);
307 if (IS_ERR(ukey))
308 goto error;
309
310 down_read(&ukey->sem);
311 upayload = user_key_payload_locked(ukey);
312 if (!upayload) {
313 /* key was revoked before we acquired its semaphore */
314 up_read(&ukey->sem);
315 key_put(ukey);
316 ukey = ERR_PTR(-EKEYREVOKED);
317 goto error;
318 }
319 *master_key = upayload->data;
320 *master_keylen = upayload->datalen;
321error:
322 return ukey;
323}
324
325static int calc_hash(struct crypto_shash *tfm, u8 *digest,
326 const u8 *buf, unsigned int buflen)
327{
328 SHASH_DESC_ON_STACK(desc, tfm);
329 int err;
330
331 desc->tfm = tfm;
332 desc->flags = 0;
333
334 err = crypto_shash_digest(desc, buf, buflen, digest);
335 shash_desc_zero(desc);
336 return err;
337}
338
339static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
340 const u8 *buf, unsigned int buflen)
341{
342 struct crypto_shash *tfm;
343 int err;
344
345 tfm = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
346 if (IS_ERR(tfm)) {
347 pr_err("encrypted_key: can't alloc %s transform: %ld\n",
348 hmac_alg, PTR_ERR(tfm));
349 return PTR_ERR(tfm);
350 }
351
352 err = crypto_shash_setkey(tfm, key, keylen);
353 if (!err)
354 err = calc_hash(tfm, digest, buf, buflen);
355 crypto_free_shash(tfm);
356 return err;
357}
358
359enum derived_key_type { ENC_KEY, AUTH_KEY };
360
361/* Derive authentication/encryption key from trusted key */
362static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
363 const u8 *master_key, size_t master_keylen)
364{
365 u8 *derived_buf;
366 unsigned int derived_buf_len;
367 int ret;
368
369 derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
370 if (derived_buf_len < HASH_SIZE)
371 derived_buf_len = HASH_SIZE;
372
373 derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
374 if (!derived_buf)
375 return -ENOMEM;
376
377 if (key_type)
378 strcpy(derived_buf, "AUTH_KEY");
379 else
380 strcpy(derived_buf, "ENC_KEY");
381
382 memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
383 master_keylen);
384 ret = calc_hash(hash_tfm, derived_key, derived_buf, derived_buf_len);
385 kzfree(derived_buf);
386 return ret;
387}
388
389static struct skcipher_request *init_skcipher_req(const u8 *key,
390 unsigned int key_len)
391{
392 struct skcipher_request *req;
393 struct crypto_skcipher *tfm;
394 int ret;
395
396 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
397 if (IS_ERR(tfm)) {
398 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
399 blkcipher_alg, PTR_ERR(tfm));
400 return ERR_CAST(tfm);
401 }
402
403 ret = crypto_skcipher_setkey(tfm, key, key_len);
404 if (ret < 0) {
405 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
406 crypto_free_skcipher(tfm);
407 return ERR_PTR(ret);
408 }
409
410 req = skcipher_request_alloc(tfm, GFP_KERNEL);
411 if (!req) {
412 pr_err("encrypted_key: failed to allocate request for %s\n",
413 blkcipher_alg);
414 crypto_free_skcipher(tfm);
415 return ERR_PTR(-ENOMEM);
416 }
417
418 skcipher_request_set_callback(req, 0, NULL, NULL);
419 return req;
420}
421
422static struct key *request_master_key(struct encrypted_key_payload *epayload,
423 const u8 **master_key, size_t *master_keylen)
424{
425 struct key *mkey = ERR_PTR(-EINVAL);
426
427 if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
428 KEY_TRUSTED_PREFIX_LEN)) {
429 mkey = request_trusted_key(epayload->master_desc +
430 KEY_TRUSTED_PREFIX_LEN,
431 master_key, master_keylen);
432 } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
433 KEY_USER_PREFIX_LEN)) {
434 mkey = request_user_key(epayload->master_desc +
435 KEY_USER_PREFIX_LEN,
436 master_key, master_keylen);
437 } else
438 goto out;
439
440 if (IS_ERR(mkey)) {
441 int ret = PTR_ERR(mkey);
442
443 if (ret == -ENOTSUPP)
444 pr_info("encrypted_key: key %s not supported",
445 epayload->master_desc);
446 else
447 pr_info("encrypted_key: key %s not found",
448 epayload->master_desc);
449 goto out;
450 }
451
452 dump_master_key(*master_key, *master_keylen);
453out:
454 return mkey;
455}
456
457/* Before returning data to userspace, encrypt decrypted data. */
458static int derived_key_encrypt(struct encrypted_key_payload *epayload,
459 const u8 *derived_key,
460 unsigned int derived_keylen)
461{
462 struct scatterlist sg_in[2];
463 struct scatterlist sg_out[1];
464 struct crypto_skcipher *tfm;
465 struct skcipher_request *req;
466 unsigned int encrypted_datalen;
467 u8 iv[AES_BLOCK_SIZE];
468 int ret;
469
470 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
471
472 req = init_skcipher_req(derived_key, derived_keylen);
473 ret = PTR_ERR(req);
474 if (IS_ERR(req))
475 goto out;
476 dump_decrypted_data(epayload);
477
478 sg_init_table(sg_in, 2);
479 sg_set_buf(&sg_in[0], epayload->decrypted_data,
480 epayload->decrypted_datalen);
481 sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
482
483 sg_init_table(sg_out, 1);
484 sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
485
486 memcpy(iv, epayload->iv, sizeof(iv));
487 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
488 ret = crypto_skcipher_encrypt(req);
489 tfm = crypto_skcipher_reqtfm(req);
490 skcipher_request_free(req);
491 crypto_free_skcipher(tfm);
492 if (ret < 0)
493 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
494 else
495 dump_encrypted_data(epayload, encrypted_datalen);
496out:
497 return ret;
498}
499
500static int datablob_hmac_append(struct encrypted_key_payload *epayload,
501 const u8 *master_key, size_t master_keylen)
502{
503 u8 derived_key[HASH_SIZE];
504 u8 *digest;
505 int ret;
506
507 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
508 if (ret < 0)
509 goto out;
510
511 digest = epayload->format + epayload->datablob_len;
512 ret = calc_hmac(digest, derived_key, sizeof derived_key,
513 epayload->format, epayload->datablob_len);
514 if (!ret)
515 dump_hmac(NULL, digest, HASH_SIZE);
516out:
517 memzero_explicit(derived_key, sizeof(derived_key));
518 return ret;
519}
520
521/* verify HMAC before decrypting encrypted key */
522static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
523 const u8 *format, const u8 *master_key,
524 size_t master_keylen)
525{
526 u8 derived_key[HASH_SIZE];
527 u8 digest[HASH_SIZE];
528 int ret;
529 char *p;
530 unsigned short len;
531
532 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
533 if (ret < 0)
534 goto out;
535
536 len = epayload->datablob_len;
537 if (!format) {
538 p = epayload->master_desc;
539 len -= strlen(epayload->format) + 1;
540 } else
541 p = epayload->format;
542
543 ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
544 if (ret < 0)
545 goto out;
546 ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
547 sizeof(digest));
548 if (ret) {
549 ret = -EINVAL;
550 dump_hmac("datablob",
551 epayload->format + epayload->datablob_len,
552 HASH_SIZE);
553 dump_hmac("calc", digest, HASH_SIZE);
554 }
555out:
556 memzero_explicit(derived_key, sizeof(derived_key));
557 return ret;
558}
559
560static int derived_key_decrypt(struct encrypted_key_payload *epayload,
561 const u8 *derived_key,
562 unsigned int derived_keylen)
563{
564 struct scatterlist sg_in[1];
565 struct scatterlist sg_out[2];
566 struct crypto_skcipher *tfm;
567 struct skcipher_request *req;
568 unsigned int encrypted_datalen;
569 u8 iv[AES_BLOCK_SIZE];
570 u8 *pad;
571 int ret;
572
573 /* Throwaway buffer to hold the unused zero padding at the end */
574 pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
575 if (!pad)
576 return -ENOMEM;
577
578 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
579 req = init_skcipher_req(derived_key, derived_keylen);
580 ret = PTR_ERR(req);
581 if (IS_ERR(req))
582 goto out;
583 dump_encrypted_data(epayload, encrypted_datalen);
584
585 sg_init_table(sg_in, 1);
586 sg_init_table(sg_out, 2);
587 sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
588 sg_set_buf(&sg_out[0], epayload->decrypted_data,
589 epayload->decrypted_datalen);
590 sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
591
592 memcpy(iv, epayload->iv, sizeof(iv));
593 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
594 ret = crypto_skcipher_decrypt(req);
595 tfm = crypto_skcipher_reqtfm(req);
596 skcipher_request_free(req);
597 crypto_free_skcipher(tfm);
598 if (ret < 0)
599 goto out;
600 dump_decrypted_data(epayload);
601out:
602 kfree(pad);
603 return ret;
604}
605
606/* Allocate memory for decrypted key and datablob. */
607static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
608 const char *format,
609 const char *master_desc,
610 const char *datalen)
611{
612 struct encrypted_key_payload *epayload = NULL;
613 unsigned short datablob_len;
614 unsigned short decrypted_datalen;
615 unsigned short payload_datalen;
616 unsigned int encrypted_datalen;
617 unsigned int format_len;
618 long dlen;
619 int ret;
620
621 ret = kstrtol(datalen, 10, &dlen);
622 if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
623 return ERR_PTR(-EINVAL);
624
625 format_len = (!format) ? strlen(key_format_default) : strlen(format);
626 decrypted_datalen = dlen;
627 payload_datalen = decrypted_datalen;
628 if (format && !strcmp(format, key_format_ecryptfs)) {
629 if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
630 pr_err("encrypted_key: keylen for the ecryptfs format "
631 "must be equal to %d bytes\n",
632 ECRYPTFS_MAX_KEY_BYTES);
633 return ERR_PTR(-EINVAL);
634 }
635 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
636 payload_datalen = sizeof(struct ecryptfs_auth_tok);
637 }
638
639 encrypted_datalen = roundup(decrypted_datalen, blksize);
640
641 datablob_len = format_len + 1 + strlen(master_desc) + 1
642 + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
643
644 ret = key_payload_reserve(key, payload_datalen + datablob_len
645 + HASH_SIZE + 1);
646 if (ret < 0)
647 return ERR_PTR(ret);
648
649 epayload = kzalloc(sizeof(*epayload) + payload_datalen +
650 datablob_len + HASH_SIZE + 1, GFP_KERNEL);
651 if (!epayload)
652 return ERR_PTR(-ENOMEM);
653
654 epayload->payload_datalen = payload_datalen;
655 epayload->decrypted_datalen = decrypted_datalen;
656 epayload->datablob_len = datablob_len;
657 return epayload;
658}
659
660static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
661 const char *format, const char *hex_encoded_iv)
662{
663 struct key *mkey;
664 u8 derived_key[HASH_SIZE];
665 const u8 *master_key;
666 u8 *hmac;
667 const char *hex_encoded_data;
668 unsigned int encrypted_datalen;
669 size_t master_keylen;
670 size_t asciilen;
671 int ret;
672
673 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
674 asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
675 if (strlen(hex_encoded_iv) != asciilen)
676 return -EINVAL;
677
678 hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
679 ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
680 if (ret < 0)
681 return -EINVAL;
682 ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
683 encrypted_datalen);
684 if (ret < 0)
685 return -EINVAL;
686
687 hmac = epayload->format + epayload->datablob_len;
688 ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
689 HASH_SIZE);
690 if (ret < 0)
691 return -EINVAL;
692
693 mkey = request_master_key(epayload, &master_key, &master_keylen);
694 if (IS_ERR(mkey))
695 return PTR_ERR(mkey);
696
697 ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
698 if (ret < 0) {
699 pr_err("encrypted_key: bad hmac (%d)\n", ret);
700 goto out;
701 }
702
703 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
704 if (ret < 0)
705 goto out;
706
707 ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
708 if (ret < 0)
709 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
710out:
711 up_read(&mkey->sem);
712 key_put(mkey);
713 memzero_explicit(derived_key, sizeof(derived_key));
714 return ret;
715}
716
717static void __ekey_init(struct encrypted_key_payload *epayload,
718 const char *format, const char *master_desc,
719 const char *datalen)
720{
721 unsigned int format_len;
722
723 format_len = (!format) ? strlen(key_format_default) : strlen(format);
724 epayload->format = epayload->payload_data + epayload->payload_datalen;
725 epayload->master_desc = epayload->format + format_len + 1;
726 epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
727 epayload->iv = epayload->datalen + strlen(datalen) + 1;
728 epayload->encrypted_data = epayload->iv + ivsize + 1;
729 epayload->decrypted_data = epayload->payload_data;
730
731 if (!format)
732 memcpy(epayload->format, key_format_default, format_len);
733 else {
734 if (!strcmp(format, key_format_ecryptfs))
735 epayload->decrypted_data =
736 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
737
738 memcpy(epayload->format, format, format_len);
739 }
740
741 memcpy(epayload->master_desc, master_desc, strlen(master_desc));
742 memcpy(epayload->datalen, datalen, strlen(datalen));
743}
744
745/*
746 * encrypted_init - initialize an encrypted key
747 *
748 * For a new key, use a random number for both the iv and data
749 * itself. For an old key, decrypt the hex encoded data.
750 */
751static int encrypted_init(struct encrypted_key_payload *epayload,
752 const char *key_desc, const char *format,
753 const char *master_desc, const char *datalen,
754 const char *hex_encoded_iv)
755{
756 int ret = 0;
757
758 if (format && !strcmp(format, key_format_ecryptfs)) {
759 ret = valid_ecryptfs_desc(key_desc);
760 if (ret < 0)
761 return ret;
762
763 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
764 key_desc);
765 }
766
767 __ekey_init(epayload, format, master_desc, datalen);
768 if (!hex_encoded_iv) {
769 get_random_bytes(epayload->iv, ivsize);
770
771 get_random_bytes(epayload->decrypted_data,
772 epayload->decrypted_datalen);
773 } else
774 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
775 return ret;
776}
777
778/*
779 * encrypted_instantiate - instantiate an encrypted key
780 *
781 * Decrypt an existing encrypted datablob or create a new encrypted key
782 * based on a kernel random number.
783 *
784 * On success, return 0. Otherwise return errno.
785 */
786static int encrypted_instantiate(struct key *key,
787 struct key_preparsed_payload *prep)
788{
789 struct encrypted_key_payload *epayload = NULL;
790 char *datablob = NULL;
791 const char *format = NULL;
792 char *master_desc = NULL;
793 char *decrypted_datalen = NULL;
794 char *hex_encoded_iv = NULL;
795 size_t datalen = prep->datalen;
796 int ret;
797
798 if (datalen <= 0 || datalen > 32767 || !prep->data)
799 return -EINVAL;
800
801 datablob = kmalloc(datalen + 1, GFP_KERNEL);
802 if (!datablob)
803 return -ENOMEM;
804 datablob[datalen] = 0;
805 memcpy(datablob, prep->data, datalen);
806 ret = datablob_parse(datablob, &format, &master_desc,
807 &decrypted_datalen, &hex_encoded_iv);
808 if (ret < 0)
809 goto out;
810
811 epayload = encrypted_key_alloc(key, format, master_desc,
812 decrypted_datalen);
813 if (IS_ERR(epayload)) {
814 ret = PTR_ERR(epayload);
815 goto out;
816 }
817 ret = encrypted_init(epayload, key->description, format, master_desc,
818 decrypted_datalen, hex_encoded_iv);
819 if (ret < 0) {
820 kzfree(epayload);
821 goto out;
822 }
823
824 rcu_assign_keypointer(key, epayload);
825out:
826 kzfree(datablob);
827 return ret;
828}
829
830static void encrypted_rcu_free(struct rcu_head *rcu)
831{
832 struct encrypted_key_payload *epayload;
833
834 epayload = container_of(rcu, struct encrypted_key_payload, rcu);
835 kzfree(epayload);
836}
837
838/*
839 * encrypted_update - update the master key description
840 *
841 * Change the master key description for an existing encrypted key.
842 * The next read will return an encrypted datablob using the new
843 * master key description.
844 *
845 * On success, return 0. Otherwise return errno.
846 */
847static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
848{
849 struct encrypted_key_payload *epayload = key->payload.data[0];
850 struct encrypted_key_payload *new_epayload;
851 char *buf;
852 char *new_master_desc = NULL;
853 const char *format = NULL;
854 size_t datalen = prep->datalen;
855 int ret = 0;
856
857 if (key_is_negative(key))
858 return -ENOKEY;
859 if (datalen <= 0 || datalen > 32767 || !prep->data)
860 return -EINVAL;
861
862 buf = kmalloc(datalen + 1, GFP_KERNEL);
863 if (!buf)
864 return -ENOMEM;
865
866 buf[datalen] = 0;
867 memcpy(buf, prep->data, datalen);
868 ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
869 if (ret < 0)
870 goto out;
871
872 ret = valid_master_desc(new_master_desc, epayload->master_desc);
873 if (ret < 0)
874 goto out;
875
876 new_epayload = encrypted_key_alloc(key, epayload->format,
877 new_master_desc, epayload->datalen);
878 if (IS_ERR(new_epayload)) {
879 ret = PTR_ERR(new_epayload);
880 goto out;
881 }
882
883 __ekey_init(new_epayload, epayload->format, new_master_desc,
884 epayload->datalen);
885
886 memcpy(new_epayload->iv, epayload->iv, ivsize);
887 memcpy(new_epayload->payload_data, epayload->payload_data,
888 epayload->payload_datalen);
889
890 rcu_assign_keypointer(key, new_epayload);
891 call_rcu(&epayload->rcu, encrypted_rcu_free);
892out:
893 kzfree(buf);
894 return ret;
895}
896
897/*
898 * encrypted_read - format and copy the encrypted data to userspace
899 *
900 * The resulting datablob format is:
901 * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
902 *
903 * On success, return to userspace the encrypted key datablob size.
904 */
905static long encrypted_read(const struct key *key, char __user *buffer,
906 size_t buflen)
907{
908 struct encrypted_key_payload *epayload;
909 struct key *mkey;
910 const u8 *master_key;
911 size_t master_keylen;
912 char derived_key[HASH_SIZE];
913 char *ascii_buf;
914 size_t asciiblob_len;
915 int ret;
916
917 epayload = dereference_key_locked(key);
918
919 /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
920 asciiblob_len = epayload->datablob_len + ivsize + 1
921 + roundup(epayload->decrypted_datalen, blksize)
922 + (HASH_SIZE * 2);
923
924 if (!buffer || buflen < asciiblob_len)
925 return asciiblob_len;
926
927 mkey = request_master_key(epayload, &master_key, &master_keylen);
928 if (IS_ERR(mkey))
929 return PTR_ERR(mkey);
930
931 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
932 if (ret < 0)
933 goto out;
934
935 ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
936 if (ret < 0)
937 goto out;
938
939 ret = datablob_hmac_append(epayload, master_key, master_keylen);
940 if (ret < 0)
941 goto out;
942
943 ascii_buf = datablob_format(epayload, asciiblob_len);
944 if (!ascii_buf) {
945 ret = -ENOMEM;
946 goto out;
947 }
948
949 up_read(&mkey->sem);
950 key_put(mkey);
951 memzero_explicit(derived_key, sizeof(derived_key));
952
953 if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
954 ret = -EFAULT;
955 kzfree(ascii_buf);
956
957 return asciiblob_len;
958out:
959 up_read(&mkey->sem);
960 key_put(mkey);
961 memzero_explicit(derived_key, sizeof(derived_key));
962 return ret;
963}
964
965/*
966 * encrypted_destroy - clear and free the key's payload
967 */
968static void encrypted_destroy(struct key *key)
969{
970 kzfree(key->payload.data[0]);
971}
972
973struct key_type key_type_encrypted = {
974 .name = "encrypted",
975 .instantiate = encrypted_instantiate,
976 .update = encrypted_update,
977 .destroy = encrypted_destroy,
978 .describe = user_describe,
979 .read = encrypted_read,
980};
981EXPORT_SYMBOL_GPL(key_type_encrypted);
982
983static int __init init_encrypted(void)
984{
985 int ret;
986
987 hash_tfm = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
988 if (IS_ERR(hash_tfm)) {
989 pr_err("encrypted_key: can't allocate %s transform: %ld\n",
990 hash_alg, PTR_ERR(hash_tfm));
991 return PTR_ERR(hash_tfm);
992 }
993
994 ret = aes_get_sizes();
995 if (ret < 0)
996 goto out;
997 ret = register_key_type(&key_type_encrypted);
998 if (ret < 0)
999 goto out;
1000 return 0;
1001out:
1002 crypto_free_shash(hash_tfm);
1003 return ret;
1004
1005}
1006
1007static void __exit cleanup_encrypted(void)
1008{
1009 crypto_free_shash(hash_tfm);
1010 unregister_key_type(&key_type_encrypted);
1011}
1012
1013late_initcall(init_encrypted);
1014module_exit(cleanup_encrypted);
1015
1016MODULE_LICENSE("GPL");