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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.txt
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/crypto.h>
32#include <linux/ctype.h>
33#include <crypto/hash.h>
34#include <crypto/sha.h>
35#include <crypto/aes.h>
36
37#include "encrypted.h"
38#include "ecryptfs_format.h"
39
40static const char KEY_TRUSTED_PREFIX[] = "trusted:";
41static const char KEY_USER_PREFIX[] = "user:";
42static const char hash_alg[] = "sha256";
43static const char hmac_alg[] = "hmac(sha256)";
44static const char blkcipher_alg[] = "cbc(aes)";
45static const char key_format_default[] = "default";
46static const char key_format_ecryptfs[] = "ecryptfs";
47static unsigned int ivsize;
48static int blksize;
49
50#define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
51#define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
52#define KEY_ECRYPTFS_DESC_LEN 16
53#define HASH_SIZE SHA256_DIGEST_SIZE
54#define MAX_DATA_SIZE 4096
55#define MIN_DATA_SIZE 20
56
57struct sdesc {
58 struct shash_desc shash;
59 char ctx[];
60};
61
62static struct crypto_shash *hashalg;
63static struct crypto_shash *hmacalg;
64
65enum {
66 Opt_err = -1, Opt_new, Opt_load, Opt_update
67};
68
69enum {
70 Opt_error = -1, Opt_default, Opt_ecryptfs
71};
72
73static const match_table_t key_format_tokens = {
74 {Opt_default, "default"},
75 {Opt_ecryptfs, "ecryptfs"},
76 {Opt_error, NULL}
77};
78
79static const match_table_t key_tokens = {
80 {Opt_new, "new"},
81 {Opt_load, "load"},
82 {Opt_update, "update"},
83 {Opt_err, NULL}
84};
85
86static int aes_get_sizes(void)
87{
88 struct crypto_blkcipher *tfm;
89
90 tfm = crypto_alloc_blkcipher(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_blkcipher_ivsize(tfm);
97 blksize = crypto_blkcipher_blocksize(tfm);
98 crypto_free_blkcipher(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 if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
145 if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
146 goto out;
147 if (orig_desc)
148 if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
149 goto out;
150 } else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
151 if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
152 goto out;
153 if (orig_desc)
154 if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
155 goto out;
156 } else
157 goto out;
158 return 0;
159out:
160 return -EINVAL;
161}
162
163/*
164 * datablob_parse - parse the keyctl data
165 *
166 * datablob format:
167 * new [<format>] <master-key name> <decrypted data length>
168 * load [<format>] <master-key name> <decrypted data length>
169 * <encrypted iv + data>
170 * update <new-master-key name>
171 *
172 * Tokenizes a copy of the keyctl data, returning a pointer to each token,
173 * which is null terminated.
174 *
175 * On success returns 0, otherwise -EINVAL.
176 */
177static int datablob_parse(char *datablob, const char **format,
178 char **master_desc, char **decrypted_datalen,
179 char **hex_encoded_iv)
180{
181 substring_t args[MAX_OPT_ARGS];
182 int ret = -EINVAL;
183 int key_cmd;
184 int key_format;
185 char *p, *keyword;
186
187 keyword = strsep(&datablob, " \t");
188 if (!keyword) {
189 pr_info("encrypted_key: insufficient parameters specified\n");
190 return ret;
191 }
192 key_cmd = match_token(keyword, key_tokens, args);
193
194 /* Get optional format: default | ecryptfs */
195 p = strsep(&datablob, " \t");
196 if (!p) {
197 pr_err("encrypted_key: insufficient parameters specified\n");
198 return ret;
199 }
200
201 key_format = match_token(p, key_format_tokens, args);
202 switch (key_format) {
203 case Opt_ecryptfs:
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 ret = 0;
240 break;
241 case Opt_load:
242 if (!decrypted_datalen) {
243 pr_info("encrypted_key: keyword \'%s\' not allowed "
244 "when called from .update method\n", keyword);
245 break;
246 }
247 *hex_encoded_iv = strsep(&datablob, " \t");
248 if (!*hex_encoded_iv) {
249 pr_info("encrypted_key: hex blob is missing\n");
250 break;
251 }
252 ret = 0;
253 break;
254 case Opt_update:
255 if (decrypted_datalen) {
256 pr_info("encrypted_key: keyword \'%s\' not allowed "
257 "when called from .instantiate method\n",
258 keyword);
259 break;
260 }
261 ret = 0;
262 break;
263 case Opt_err:
264 pr_info("encrypted_key: keyword \'%s\' not recognized\n",
265 keyword);
266 break;
267 }
268out:
269 return ret;
270}
271
272/*
273 * datablob_format - format as an ascii string, before copying to userspace
274 */
275static char *datablob_format(struct encrypted_key_payload *epayload,
276 size_t asciiblob_len)
277{
278 char *ascii_buf, *bufp;
279 u8 *iv = epayload->iv;
280 int len;
281 int i;
282
283 ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
284 if (!ascii_buf)
285 goto out;
286
287 ascii_buf[asciiblob_len] = '\0';
288
289 /* copy datablob master_desc and datalen strings */
290 len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
291 epayload->master_desc, epayload->datalen);
292
293 /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
294 bufp = &ascii_buf[len];
295 for (i = 0; i < (asciiblob_len - len) / 2; i++)
296 bufp = hex_byte_pack(bufp, iv[i]);
297out:
298 return ascii_buf;
299}
300
301/*
302 * request_user_key - request the user key
303 *
304 * Use a user provided key to encrypt/decrypt an encrypted-key.
305 */
306static struct key *request_user_key(const char *master_desc, u8 **master_key,
307 size_t *master_keylen)
308{
309 struct user_key_payload *upayload;
310 struct key *ukey;
311
312 ukey = request_key(&key_type_user, master_desc, NULL);
313 if (IS_ERR(ukey))
314 goto error;
315
316 down_read(&ukey->sem);
317 upayload = ukey->payload.data;
318 *master_key = upayload->data;
319 *master_keylen = upayload->datalen;
320error:
321 return ukey;
322}
323
324static struct sdesc *alloc_sdesc(struct crypto_shash *alg)
325{
326 struct sdesc *sdesc;
327 int size;
328
329 size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
330 sdesc = kmalloc(size, GFP_KERNEL);
331 if (!sdesc)
332 return ERR_PTR(-ENOMEM);
333 sdesc->shash.tfm = alg;
334 sdesc->shash.flags = 0x0;
335 return sdesc;
336}
337
338static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
339 const u8 *buf, unsigned int buflen)
340{
341 struct sdesc *sdesc;
342 int ret;
343
344 sdesc = alloc_sdesc(hmacalg);
345 if (IS_ERR(sdesc)) {
346 pr_info("encrypted_key: can't alloc %s\n", hmac_alg);
347 return PTR_ERR(sdesc);
348 }
349
350 ret = crypto_shash_setkey(hmacalg, key, keylen);
351 if (!ret)
352 ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
353 kfree(sdesc);
354 return ret;
355}
356
357static int calc_hash(u8 *digest, const u8 *buf, unsigned int buflen)
358{
359 struct sdesc *sdesc;
360 int ret;
361
362 sdesc = alloc_sdesc(hashalg);
363 if (IS_ERR(sdesc)) {
364 pr_info("encrypted_key: can't alloc %s\n", hash_alg);
365 return PTR_ERR(sdesc);
366 }
367
368 ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
369 kfree(sdesc);
370 return ret;
371}
372
373enum derived_key_type { ENC_KEY, AUTH_KEY };
374
375/* Derive authentication/encryption key from trusted key */
376static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
377 const u8 *master_key, size_t master_keylen)
378{
379 u8 *derived_buf;
380 unsigned int derived_buf_len;
381 int ret;
382
383 derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
384 if (derived_buf_len < HASH_SIZE)
385 derived_buf_len = HASH_SIZE;
386
387 derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
388 if (!derived_buf) {
389 pr_err("encrypted_key: out of memory\n");
390 return -ENOMEM;
391 }
392 if (key_type)
393 strcpy(derived_buf, "AUTH_KEY");
394 else
395 strcpy(derived_buf, "ENC_KEY");
396
397 memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
398 master_keylen);
399 ret = calc_hash(derived_key, derived_buf, derived_buf_len);
400 kfree(derived_buf);
401 return ret;
402}
403
404static int init_blkcipher_desc(struct blkcipher_desc *desc, const u8 *key,
405 unsigned int key_len, const u8 *iv,
406 unsigned int ivsize)
407{
408 int ret;
409
410 desc->tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
411 if (IS_ERR(desc->tfm)) {
412 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
413 blkcipher_alg, PTR_ERR(desc->tfm));
414 return PTR_ERR(desc->tfm);
415 }
416 desc->flags = 0;
417
418 ret = crypto_blkcipher_setkey(desc->tfm, key, key_len);
419 if (ret < 0) {
420 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
421 crypto_free_blkcipher(desc->tfm);
422 return ret;
423 }
424 crypto_blkcipher_set_iv(desc->tfm, iv, ivsize);
425 return 0;
426}
427
428static struct key *request_master_key(struct encrypted_key_payload *epayload,
429 u8 **master_key, size_t *master_keylen)
430{
431 struct key *mkey = NULL;
432
433 if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
434 KEY_TRUSTED_PREFIX_LEN)) {
435 mkey = request_trusted_key(epayload->master_desc +
436 KEY_TRUSTED_PREFIX_LEN,
437 master_key, master_keylen);
438 } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
439 KEY_USER_PREFIX_LEN)) {
440 mkey = request_user_key(epayload->master_desc +
441 KEY_USER_PREFIX_LEN,
442 master_key, master_keylen);
443 } else
444 goto out;
445
446 if (IS_ERR(mkey)) {
447 int ret = PTR_ERR(mkey);
448
449 if (ret == -ENOTSUPP)
450 pr_info("encrypted_key: key %s not supported",
451 epayload->master_desc);
452 else
453 pr_info("encrypted_key: key %s not found",
454 epayload->master_desc);
455 goto out;
456 }
457
458 dump_master_key(*master_key, *master_keylen);
459out:
460 return mkey;
461}
462
463/* Before returning data to userspace, encrypt decrypted data. */
464static int derived_key_encrypt(struct encrypted_key_payload *epayload,
465 const u8 *derived_key,
466 unsigned int derived_keylen)
467{
468 struct scatterlist sg_in[2];
469 struct scatterlist sg_out[1];
470 struct blkcipher_desc desc;
471 unsigned int encrypted_datalen;
472 unsigned int padlen;
473 char pad[16];
474 int ret;
475
476 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
477 padlen = encrypted_datalen - epayload->decrypted_datalen;
478
479 ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
480 epayload->iv, ivsize);
481 if (ret < 0)
482 goto out;
483 dump_decrypted_data(epayload);
484
485 memset(pad, 0, sizeof pad);
486 sg_init_table(sg_in, 2);
487 sg_set_buf(&sg_in[0], epayload->decrypted_data,
488 epayload->decrypted_datalen);
489 sg_set_buf(&sg_in[1], pad, padlen);
490
491 sg_init_table(sg_out, 1);
492 sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
493
494 ret = crypto_blkcipher_encrypt(&desc, sg_out, sg_in, encrypted_datalen);
495 crypto_free_blkcipher(desc.tfm);
496 if (ret < 0)
497 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
498 else
499 dump_encrypted_data(epayload, encrypted_datalen);
500out:
501 return ret;
502}
503
504static int datablob_hmac_append(struct encrypted_key_payload *epayload,
505 const u8 *master_key, size_t master_keylen)
506{
507 u8 derived_key[HASH_SIZE];
508 u8 *digest;
509 int ret;
510
511 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
512 if (ret < 0)
513 goto out;
514
515 digest = epayload->format + epayload->datablob_len;
516 ret = calc_hmac(digest, derived_key, sizeof derived_key,
517 epayload->format, epayload->datablob_len);
518 if (!ret)
519 dump_hmac(NULL, digest, HASH_SIZE);
520out:
521 return ret;
522}
523
524/* verify HMAC before decrypting encrypted key */
525static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
526 const u8 *format, const u8 *master_key,
527 size_t master_keylen)
528{
529 u8 derived_key[HASH_SIZE];
530 u8 digest[HASH_SIZE];
531 int ret;
532 char *p;
533 unsigned short len;
534
535 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
536 if (ret < 0)
537 goto out;
538
539 len = epayload->datablob_len;
540 if (!format) {
541 p = epayload->master_desc;
542 len -= strlen(epayload->format) + 1;
543 } else
544 p = epayload->format;
545
546 ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
547 if (ret < 0)
548 goto out;
549 ret = memcmp(digest, epayload->format + epayload->datablob_len,
550 sizeof digest);
551 if (ret) {
552 ret = -EINVAL;
553 dump_hmac("datablob",
554 epayload->format + epayload->datablob_len,
555 HASH_SIZE);
556 dump_hmac("calc", digest, HASH_SIZE);
557 }
558out:
559 return ret;
560}
561
562static int derived_key_decrypt(struct encrypted_key_payload *epayload,
563 const u8 *derived_key,
564 unsigned int derived_keylen)
565{
566 struct scatterlist sg_in[1];
567 struct scatterlist sg_out[2];
568 struct blkcipher_desc desc;
569 unsigned int encrypted_datalen;
570 char pad[16];
571 int ret;
572
573 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
574 ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
575 epayload->iv, ivsize);
576 if (ret < 0)
577 goto out;
578 dump_encrypted_data(epayload, encrypted_datalen);
579
580 memset(pad, 0, sizeof pad);
581 sg_init_table(sg_in, 1);
582 sg_init_table(sg_out, 2);
583 sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
584 sg_set_buf(&sg_out[0], epayload->decrypted_data,
585 epayload->decrypted_datalen);
586 sg_set_buf(&sg_out[1], pad, sizeof pad);
587
588 ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in, encrypted_datalen);
589 crypto_free_blkcipher(desc.tfm);
590 if (ret < 0)
591 goto out;
592 dump_decrypted_data(epayload);
593out:
594 return ret;
595}
596
597/* Allocate memory for decrypted key and datablob. */
598static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
599 const char *format,
600 const char *master_desc,
601 const char *datalen)
602{
603 struct encrypted_key_payload *epayload = NULL;
604 unsigned short datablob_len;
605 unsigned short decrypted_datalen;
606 unsigned short payload_datalen;
607 unsigned int encrypted_datalen;
608 unsigned int format_len;
609 long dlen;
610 int ret;
611
612 ret = kstrtol(datalen, 10, &dlen);
613 if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
614 return ERR_PTR(-EINVAL);
615
616 format_len = (!format) ? strlen(key_format_default) : strlen(format);
617 decrypted_datalen = dlen;
618 payload_datalen = decrypted_datalen;
619 if (format && !strcmp(format, key_format_ecryptfs)) {
620 if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
621 pr_err("encrypted_key: keylen for the ecryptfs format "
622 "must be equal to %d bytes\n",
623 ECRYPTFS_MAX_KEY_BYTES);
624 return ERR_PTR(-EINVAL);
625 }
626 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
627 payload_datalen = sizeof(struct ecryptfs_auth_tok);
628 }
629
630 encrypted_datalen = roundup(decrypted_datalen, blksize);
631
632 datablob_len = format_len + 1 + strlen(master_desc) + 1
633 + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
634
635 ret = key_payload_reserve(key, payload_datalen + datablob_len
636 + HASH_SIZE + 1);
637 if (ret < 0)
638 return ERR_PTR(ret);
639
640 epayload = kzalloc(sizeof(*epayload) + payload_datalen +
641 datablob_len + HASH_SIZE + 1, GFP_KERNEL);
642 if (!epayload)
643 return ERR_PTR(-ENOMEM);
644
645 epayload->payload_datalen = payload_datalen;
646 epayload->decrypted_datalen = decrypted_datalen;
647 epayload->datablob_len = datablob_len;
648 return epayload;
649}
650
651static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
652 const char *format, const char *hex_encoded_iv)
653{
654 struct key *mkey;
655 u8 derived_key[HASH_SIZE];
656 u8 *master_key;
657 u8 *hmac;
658 const char *hex_encoded_data;
659 unsigned int encrypted_datalen;
660 size_t master_keylen;
661 size_t asciilen;
662 int ret;
663
664 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
665 asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
666 if (strlen(hex_encoded_iv) != asciilen)
667 return -EINVAL;
668
669 hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
670 ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
671 if (ret < 0)
672 return -EINVAL;
673 ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
674 encrypted_datalen);
675 if (ret < 0)
676 return -EINVAL;
677
678 hmac = epayload->format + epayload->datablob_len;
679 ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
680 HASH_SIZE);
681 if (ret < 0)
682 return -EINVAL;
683
684 mkey = request_master_key(epayload, &master_key, &master_keylen);
685 if (IS_ERR(mkey))
686 return PTR_ERR(mkey);
687
688 ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
689 if (ret < 0) {
690 pr_err("encrypted_key: bad hmac (%d)\n", ret);
691 goto out;
692 }
693
694 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
695 if (ret < 0)
696 goto out;
697
698 ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
699 if (ret < 0)
700 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
701out:
702 up_read(&mkey->sem);
703 key_put(mkey);
704 return ret;
705}
706
707static void __ekey_init(struct encrypted_key_payload *epayload,
708 const char *format, const char *master_desc,
709 const char *datalen)
710{
711 unsigned int format_len;
712
713 format_len = (!format) ? strlen(key_format_default) : strlen(format);
714 epayload->format = epayload->payload_data + epayload->payload_datalen;
715 epayload->master_desc = epayload->format + format_len + 1;
716 epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
717 epayload->iv = epayload->datalen + strlen(datalen) + 1;
718 epayload->encrypted_data = epayload->iv + ivsize + 1;
719 epayload->decrypted_data = epayload->payload_data;
720
721 if (!format)
722 memcpy(epayload->format, key_format_default, format_len);
723 else {
724 if (!strcmp(format, key_format_ecryptfs))
725 epayload->decrypted_data =
726 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
727
728 memcpy(epayload->format, format, format_len);
729 }
730
731 memcpy(epayload->master_desc, master_desc, strlen(master_desc));
732 memcpy(epayload->datalen, datalen, strlen(datalen));
733}
734
735/*
736 * encrypted_init - initialize an encrypted key
737 *
738 * For a new key, use a random number for both the iv and data
739 * itself. For an old key, decrypt the hex encoded data.
740 */
741static int encrypted_init(struct encrypted_key_payload *epayload,
742 const char *key_desc, const char *format,
743 const char *master_desc, const char *datalen,
744 const char *hex_encoded_iv)
745{
746 int ret = 0;
747
748 if (format && !strcmp(format, key_format_ecryptfs)) {
749 ret = valid_ecryptfs_desc(key_desc);
750 if (ret < 0)
751 return ret;
752
753 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
754 key_desc);
755 }
756
757 __ekey_init(epayload, format, master_desc, datalen);
758 if (!hex_encoded_iv) {
759 get_random_bytes(epayload->iv, ivsize);
760
761 get_random_bytes(epayload->decrypted_data,
762 epayload->decrypted_datalen);
763 } else
764 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
765 return ret;
766}
767
768/*
769 * encrypted_instantiate - instantiate an encrypted key
770 *
771 * Decrypt an existing encrypted datablob or create a new encrypted key
772 * based on a kernel random number.
773 *
774 * On success, return 0. Otherwise return errno.
775 */
776static int encrypted_instantiate(struct key *key,
777 struct key_preparsed_payload *prep)
778{
779 struct encrypted_key_payload *epayload = NULL;
780 char *datablob = NULL;
781 const char *format = NULL;
782 char *master_desc = NULL;
783 char *decrypted_datalen = NULL;
784 char *hex_encoded_iv = NULL;
785 size_t datalen = prep->datalen;
786 int ret;
787
788 if (datalen <= 0 || datalen > 32767 || !prep->data)
789 return -EINVAL;
790
791 datablob = kmalloc(datalen + 1, GFP_KERNEL);
792 if (!datablob)
793 return -ENOMEM;
794 datablob[datalen] = 0;
795 memcpy(datablob, prep->data, datalen);
796 ret = datablob_parse(datablob, &format, &master_desc,
797 &decrypted_datalen, &hex_encoded_iv);
798 if (ret < 0)
799 goto out;
800
801 epayload = encrypted_key_alloc(key, format, master_desc,
802 decrypted_datalen);
803 if (IS_ERR(epayload)) {
804 ret = PTR_ERR(epayload);
805 goto out;
806 }
807 ret = encrypted_init(epayload, key->description, format, master_desc,
808 decrypted_datalen, hex_encoded_iv);
809 if (ret < 0) {
810 kfree(epayload);
811 goto out;
812 }
813
814 rcu_assign_keypointer(key, epayload);
815out:
816 kfree(datablob);
817 return ret;
818}
819
820static void encrypted_rcu_free(struct rcu_head *rcu)
821{
822 struct encrypted_key_payload *epayload;
823
824 epayload = container_of(rcu, struct encrypted_key_payload, rcu);
825 memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
826 kfree(epayload);
827}
828
829/*
830 * encrypted_update - update the master key description
831 *
832 * Change the master key description for an existing encrypted key.
833 * The next read will return an encrypted datablob using the new
834 * master key description.
835 *
836 * On success, return 0. Otherwise return errno.
837 */
838static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
839{
840 struct encrypted_key_payload *epayload = key->payload.data;
841 struct encrypted_key_payload *new_epayload;
842 char *buf;
843 char *new_master_desc = NULL;
844 const char *format = NULL;
845 size_t datalen = prep->datalen;
846 int ret = 0;
847
848 if (datalen <= 0 || datalen > 32767 || !prep->data)
849 return -EINVAL;
850
851 buf = kmalloc(datalen + 1, GFP_KERNEL);
852 if (!buf)
853 return -ENOMEM;
854
855 buf[datalen] = 0;
856 memcpy(buf, prep->data, datalen);
857 ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
858 if (ret < 0)
859 goto out;
860
861 ret = valid_master_desc(new_master_desc, epayload->master_desc);
862 if (ret < 0)
863 goto out;
864
865 new_epayload = encrypted_key_alloc(key, epayload->format,
866 new_master_desc, epayload->datalen);
867 if (IS_ERR(new_epayload)) {
868 ret = PTR_ERR(new_epayload);
869 goto out;
870 }
871
872 __ekey_init(new_epayload, epayload->format, new_master_desc,
873 epayload->datalen);
874
875 memcpy(new_epayload->iv, epayload->iv, ivsize);
876 memcpy(new_epayload->payload_data, epayload->payload_data,
877 epayload->payload_datalen);
878
879 rcu_assign_keypointer(key, new_epayload);
880 call_rcu(&epayload->rcu, encrypted_rcu_free);
881out:
882 kfree(buf);
883 return ret;
884}
885
886/*
887 * encrypted_read - format and copy the encrypted data to userspace
888 *
889 * The resulting datablob format is:
890 * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
891 *
892 * On success, return to userspace the encrypted key datablob size.
893 */
894static long encrypted_read(const struct key *key, char __user *buffer,
895 size_t buflen)
896{
897 struct encrypted_key_payload *epayload;
898 struct key *mkey;
899 u8 *master_key;
900 size_t master_keylen;
901 char derived_key[HASH_SIZE];
902 char *ascii_buf;
903 size_t asciiblob_len;
904 int ret;
905
906 epayload = rcu_dereference_key(key);
907
908 /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
909 asciiblob_len = epayload->datablob_len + ivsize + 1
910 + roundup(epayload->decrypted_datalen, blksize)
911 + (HASH_SIZE * 2);
912
913 if (!buffer || buflen < asciiblob_len)
914 return asciiblob_len;
915
916 mkey = request_master_key(epayload, &master_key, &master_keylen);
917 if (IS_ERR(mkey))
918 return PTR_ERR(mkey);
919
920 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
921 if (ret < 0)
922 goto out;
923
924 ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
925 if (ret < 0)
926 goto out;
927
928 ret = datablob_hmac_append(epayload, master_key, master_keylen);
929 if (ret < 0)
930 goto out;
931
932 ascii_buf = datablob_format(epayload, asciiblob_len);
933 if (!ascii_buf) {
934 ret = -ENOMEM;
935 goto out;
936 }
937
938 up_read(&mkey->sem);
939 key_put(mkey);
940
941 if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
942 ret = -EFAULT;
943 kfree(ascii_buf);
944
945 return asciiblob_len;
946out:
947 up_read(&mkey->sem);
948 key_put(mkey);
949 return ret;
950}
951
952/*
953 * encrypted_destroy - before freeing the key, clear the decrypted data
954 *
955 * Before freeing the key, clear the memory containing the decrypted
956 * key data.
957 */
958static void encrypted_destroy(struct key *key)
959{
960 struct encrypted_key_payload *epayload = key->payload.data;
961
962 if (!epayload)
963 return;
964
965 memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
966 kfree(key->payload.data);
967}
968
969struct key_type key_type_encrypted = {
970 .name = "encrypted",
971 .instantiate = encrypted_instantiate,
972 .update = encrypted_update,
973 .match = user_match,
974 .destroy = encrypted_destroy,
975 .describe = user_describe,
976 .read = encrypted_read,
977};
978EXPORT_SYMBOL_GPL(key_type_encrypted);
979
980static void encrypted_shash_release(void)
981{
982 if (hashalg)
983 crypto_free_shash(hashalg);
984 if (hmacalg)
985 crypto_free_shash(hmacalg);
986}
987
988static int __init encrypted_shash_alloc(void)
989{
990 int ret;
991
992 hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
993 if (IS_ERR(hmacalg)) {
994 pr_info("encrypted_key: could not allocate crypto %s\n",
995 hmac_alg);
996 return PTR_ERR(hmacalg);
997 }
998
999 hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
1000 if (IS_ERR(hashalg)) {
1001 pr_info("encrypted_key: could not allocate crypto %s\n",
1002 hash_alg);
1003 ret = PTR_ERR(hashalg);
1004 goto hashalg_fail;
1005 }
1006
1007 return 0;
1008
1009hashalg_fail:
1010 crypto_free_shash(hmacalg);
1011 return ret;
1012}
1013
1014static int __init init_encrypted(void)
1015{
1016 int ret;
1017
1018 ret = encrypted_shash_alloc();
1019 if (ret < 0)
1020 return ret;
1021 ret = register_key_type(&key_type_encrypted);
1022 if (ret < 0)
1023 goto out;
1024 return aes_get_sizes();
1025out:
1026 encrypted_shash_release();
1027 return ret;
1028
1029}
1030
1031static void __exit cleanup_encrypted(void)
1032{
1033 encrypted_shash_release();
1034 unregister_key_type(&key_type_encrypted);
1035}
1036
1037late_initcall(init_encrypted);
1038module_exit(cleanup_encrypted);
1039
1040MODULE_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");