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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/sha.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 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_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 }
263out:
264 return ret;
265}
266
267/*
268 * datablob_format - format as an ascii string, before copying to userspace
269 */
270static 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]);
292out:
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 */
301static 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;
322error:
323 return ukey;
324}
325
326static 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
346enum derived_key_type { ENC_KEY, AUTH_KEY };
347
348/* Derive authentication/encryption key from trusted key */
349static 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
377static 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
410static 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);
441out:
442 return mkey;
443}
444
445/* Before returning data to userspace, encrypt decrypted data. */
446static 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);
484out:
485 return ret;
486}
487
488static 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);
504out:
505 memzero_explicit(derived_key, sizeof(derived_key));
506 return ret;
507}
508
509/* verify HMAC before decrypting encrypted key */
510static 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 }
543out:
544 memzero_explicit(derived_key, sizeof(derived_key));
545 return ret;
546}
547
548static 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);
589out:
590 kfree(pad);
591 return ret;
592}
593
594/* Allocate memory for decrypted key and datablob. */
595static 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
655static 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);
705out:
706 up_read(&mkey->sem);
707 key_put(mkey);
708 memzero_explicit(derived_key, sizeof(derived_key));
709 return ret;
710}
711
712static 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 */
746static 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 */
781static 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);
820out:
821 kfree_sensitive(datablob);
822 return ret;
823}
824
825static 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 */
842static 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);
887out:
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 */
900static 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;
952out:
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 */
962static void encrypted_destroy(struct key *key)
963{
964 kfree_sensitive(key->payload.data[0]);
965}
966
967struct 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};
975EXPORT_SYMBOL_GPL(key_type_encrypted);
976
977static 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;
995out:
996 crypto_free_shash(hash_tfm);
997 return ret;
998
999}
1000
1001static void __exit cleanup_encrypted(void)
1002{
1003 crypto_free_shash(hash_tfm);
1004 unregister_key_type(&key_type_encrypted);
1005}
1006
1007late_initcall(init_encrypted);
1008module_exit(cleanup_encrypted);
1009
1010MODULE_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");