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/hash.h>
31 #include <crypto/sha2.h>
32 #include <crypto/skcipher.h>
33 #include <crypto/utils.h>
34
35 #include "encrypted.h"
36 #include "ecryptfs_format.h"
37
38 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
39 static const char KEY_USER_PREFIX[] = "user:";
40 static const char hash_alg[] = "sha256";
41 static const char hmac_alg[] = "hmac(sha256)";
42 static const char blkcipher_alg[] = "cbc(aes)";
43 static const char key_format_default[] = "default";
44 static const char key_format_ecryptfs[] = "ecryptfs";
45 static const char key_format_enc32[] = "enc32";
46 static unsigned int ivsize;
47 static int blksize;
48
49 #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
50 #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
51 #define KEY_ECRYPTFS_DESC_LEN 16
52 #define HASH_SIZE SHA256_DIGEST_SIZE
53 #define MAX_DATA_SIZE 4096
54 #define MIN_DATA_SIZE 20
55 #define KEY_ENC32_PAYLOAD_LEN 32
56
57 static struct crypto_shash *hash_tfm;
58
59 enum {
60 Opt_new, Opt_load, Opt_update, Opt_err
61 };
62
63 enum {
64 Opt_default, Opt_ecryptfs, Opt_enc32, Opt_error
65 };
66
67 static const match_table_t key_format_tokens = {
68 {Opt_default, "default"},
69 {Opt_ecryptfs, "ecryptfs"},
70 {Opt_enc32, "enc32"},
71 {Opt_error, NULL}
72 };
73
74 static const match_table_t key_tokens = {
75 {Opt_new, "new"},
76 {Opt_load, "load"},
77 {Opt_update, "update"},
78 {Opt_err, NULL}
79 };
80
81 static bool user_decrypted_data = IS_ENABLED(CONFIG_USER_DECRYPTED_DATA);
82 module_param(user_decrypted_data, bool, 0);
83 MODULE_PARM_DESC(user_decrypted_data,
84 "Allow instantiation of encrypted keys using provided decrypted data");
85
aes_get_sizes(void)86 static int aes_get_sizes(void)
87 {
88 struct crypto_skcipher *tfm;
89
90 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
91 if (IS_ERR(tfm)) {
92 pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
93 PTR_ERR(tfm));
94 return PTR_ERR(tfm);
95 }
96 ivsize = crypto_skcipher_ivsize(tfm);
97 blksize = crypto_skcipher_blocksize(tfm);
98 crypto_free_skcipher(tfm);
99 return 0;
100 }
101
102 /*
103 * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
104 *
105 * The description of a encrypted key with format 'ecryptfs' must contain
106 * exactly 16 hexadecimal characters.
107 *
108 */
valid_ecryptfs_desc(const char * ecryptfs_desc)109 static 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 */
valid_master_desc(const char * new_desc,const char * orig_desc)142 static int valid_master_desc(const char *new_desc, const char *orig_desc)
143 {
144 int prefix_len;
145
146 if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
147 prefix_len = KEY_TRUSTED_PREFIX_LEN;
148 else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
149 prefix_len = KEY_USER_PREFIX_LEN;
150 else
151 return -EINVAL;
152
153 if (!new_desc[prefix_len])
154 return -EINVAL;
155
156 if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
157 return -EINVAL;
158
159 return 0;
160 }
161
162 /*
163 * datablob_parse - parse the keyctl data
164 *
165 * datablob format:
166 * new [<format>] <master-key name> <decrypted data length> [<decrypted data>]
167 * load [<format>] <master-key name> <decrypted data length>
168 * <encrypted iv + data>
169 * update <new-master-key name>
170 *
171 * Tokenizes a copy of the keyctl data, returning a pointer to each token,
172 * which is null terminated.
173 *
174 * On success returns 0, otherwise -EINVAL.
175 */
datablob_parse(char * datablob,const char ** format,char ** master_desc,char ** decrypted_datalen,char ** hex_encoded_iv,char ** decrypted_data)176 static int datablob_parse(char *datablob, const char **format,
177 char **master_desc, char **decrypted_datalen,
178 char **hex_encoded_iv, char **decrypted_data)
179 {
180 substring_t args[MAX_OPT_ARGS];
181 int ret = -EINVAL;
182 int key_cmd;
183 int key_format;
184 char *p, *keyword;
185
186 keyword = strsep(&datablob, " \t");
187 if (!keyword) {
188 pr_info("encrypted_key: insufficient parameters specified\n");
189 return ret;
190 }
191 key_cmd = match_token(keyword, key_tokens, args);
192
193 /* Get optional format: default | ecryptfs */
194 p = strsep(&datablob, " \t");
195 if (!p) {
196 pr_err("encrypted_key: insufficient parameters specified\n");
197 return ret;
198 }
199
200 key_format = match_token(p, key_format_tokens, args);
201 switch (key_format) {
202 case Opt_ecryptfs:
203 case Opt_enc32:
204 case Opt_default:
205 *format = p;
206 *master_desc = strsep(&datablob, " \t");
207 break;
208 case Opt_error:
209 *master_desc = p;
210 break;
211 }
212
213 if (!*master_desc) {
214 pr_info("encrypted_key: master key parameter is missing\n");
215 goto out;
216 }
217
218 if (valid_master_desc(*master_desc, NULL) < 0) {
219 pr_info("encrypted_key: master key parameter \'%s\' "
220 "is invalid\n", *master_desc);
221 goto out;
222 }
223
224 if (decrypted_datalen) {
225 *decrypted_datalen = strsep(&datablob, " \t");
226 if (!*decrypted_datalen) {
227 pr_info("encrypted_key: keylen parameter is missing\n");
228 goto out;
229 }
230 }
231
232 switch (key_cmd) {
233 case Opt_new:
234 if (!decrypted_datalen) {
235 pr_info("encrypted_key: keyword \'%s\' not allowed "
236 "when called from .update method\n", keyword);
237 break;
238 }
239 *decrypted_data = strsep(&datablob, " \t");
240 ret = 0;
241 break;
242 case Opt_load:
243 if (!decrypted_datalen) {
244 pr_info("encrypted_key: keyword \'%s\' not allowed "
245 "when called from .update method\n", keyword);
246 break;
247 }
248 *hex_encoded_iv = strsep(&datablob, " \t");
249 if (!*hex_encoded_iv) {
250 pr_info("encrypted_key: hex blob is missing\n");
251 break;
252 }
253 ret = 0;
254 break;
255 case Opt_update:
256 if (decrypted_datalen) {
257 pr_info("encrypted_key: keyword \'%s\' not allowed "
258 "when called from .instantiate method\n",
259 keyword);
260 break;
261 }
262 ret = 0;
263 break;
264 case Opt_err:
265 pr_info("encrypted_key: keyword \'%s\' not recognized\n",
266 keyword);
267 break;
268 }
269 out:
270 return ret;
271 }
272
273 /*
274 * datablob_format - format as an ascii string, before copying to userspace
275 */
datablob_format(struct encrypted_key_payload * epayload,size_t asciiblob_len)276 static char *datablob_format(struct encrypted_key_payload *epayload,
277 size_t asciiblob_len)
278 {
279 char *ascii_buf, *bufp;
280 u8 *iv = epayload->iv;
281 int len;
282 int i;
283
284 ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
285 if (!ascii_buf)
286 goto out;
287
288 ascii_buf[asciiblob_len] = '\0';
289
290 /* copy datablob master_desc and datalen strings */
291 len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
292 epayload->master_desc, epayload->datalen);
293
294 /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
295 bufp = &ascii_buf[len];
296 for (i = 0; i < (asciiblob_len - len) / 2; i++)
297 bufp = hex_byte_pack(bufp, iv[i]);
298 out:
299 return ascii_buf;
300 }
301
302 /*
303 * request_user_key - request the user key
304 *
305 * Use a user provided key to encrypt/decrypt an encrypted-key.
306 */
request_user_key(const char * master_desc,const u8 ** master_key,size_t * master_keylen)307 static struct key *request_user_key(const char *master_desc, const u8 **master_key,
308 size_t *master_keylen)
309 {
310 const struct user_key_payload *upayload;
311 struct key *ukey;
312
313 ukey = request_key(&key_type_user, master_desc, NULL);
314 if (IS_ERR(ukey))
315 goto error;
316
317 down_read(&ukey->sem);
318 upayload = user_key_payload_locked(ukey);
319 if (!upayload) {
320 /* key was revoked before we acquired its semaphore */
321 up_read(&ukey->sem);
322 key_put(ukey);
323 ukey = ERR_PTR(-EKEYREVOKED);
324 goto error;
325 }
326 *master_key = upayload->data;
327 *master_keylen = upayload->datalen;
328 error:
329 return ukey;
330 }
331
calc_hmac(u8 * digest,const u8 * key,unsigned int keylen,const u8 * buf,unsigned int buflen)332 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
333 const u8 *buf, unsigned int buflen)
334 {
335 struct crypto_shash *tfm;
336 int err;
337
338 tfm = crypto_alloc_shash(hmac_alg, 0, 0);
339 if (IS_ERR(tfm)) {
340 pr_err("encrypted_key: can't alloc %s transform: %ld\n",
341 hmac_alg, PTR_ERR(tfm));
342 return PTR_ERR(tfm);
343 }
344
345 err = crypto_shash_setkey(tfm, key, keylen);
346 if (!err)
347 err = crypto_shash_tfm_digest(tfm, buf, buflen, digest);
348 crypto_free_shash(tfm);
349 return err;
350 }
351
352 enum derived_key_type { ENC_KEY, AUTH_KEY };
353
354 /* Derive authentication/encryption key from trusted key */
get_derived_key(u8 * derived_key,enum derived_key_type key_type,const u8 * master_key,size_t master_keylen)355 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
356 const u8 *master_key, size_t master_keylen)
357 {
358 u8 *derived_buf;
359 unsigned int derived_buf_len;
360 int ret;
361
362 derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
363 if (derived_buf_len < HASH_SIZE)
364 derived_buf_len = HASH_SIZE;
365
366 derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
367 if (!derived_buf)
368 return -ENOMEM;
369
370 if (key_type)
371 strcpy(derived_buf, "AUTH_KEY");
372 else
373 strcpy(derived_buf, "ENC_KEY");
374
375 memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
376 master_keylen);
377 ret = crypto_shash_tfm_digest(hash_tfm, derived_buf, derived_buf_len,
378 derived_key);
379 kfree_sensitive(derived_buf);
380 return ret;
381 }
382
init_skcipher_req(const u8 * key,unsigned int key_len)383 static struct skcipher_request *init_skcipher_req(const u8 *key,
384 unsigned int key_len)
385 {
386 struct skcipher_request *req;
387 struct crypto_skcipher *tfm;
388 int ret;
389
390 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
391 if (IS_ERR(tfm)) {
392 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
393 blkcipher_alg, PTR_ERR(tfm));
394 return ERR_CAST(tfm);
395 }
396
397 ret = crypto_skcipher_setkey(tfm, key, key_len);
398 if (ret < 0) {
399 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
400 crypto_free_skcipher(tfm);
401 return ERR_PTR(ret);
402 }
403
404 req = skcipher_request_alloc(tfm, GFP_KERNEL);
405 if (!req) {
406 pr_err("encrypted_key: failed to allocate request for %s\n",
407 blkcipher_alg);
408 crypto_free_skcipher(tfm);
409 return ERR_PTR(-ENOMEM);
410 }
411
412 skcipher_request_set_callback(req, 0, NULL, NULL);
413 return req;
414 }
415
request_master_key(struct encrypted_key_payload * epayload,const u8 ** master_key,size_t * master_keylen)416 static struct key *request_master_key(struct encrypted_key_payload *epayload,
417 const u8 **master_key, size_t *master_keylen)
418 {
419 struct key *mkey = ERR_PTR(-EINVAL);
420
421 if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
422 KEY_TRUSTED_PREFIX_LEN)) {
423 mkey = request_trusted_key(epayload->master_desc +
424 KEY_TRUSTED_PREFIX_LEN,
425 master_key, master_keylen);
426 } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
427 KEY_USER_PREFIX_LEN)) {
428 mkey = request_user_key(epayload->master_desc +
429 KEY_USER_PREFIX_LEN,
430 master_key, master_keylen);
431 } else
432 goto out;
433
434 if (IS_ERR(mkey)) {
435 int ret = PTR_ERR(mkey);
436
437 if (ret == -ENOTSUPP)
438 pr_info("encrypted_key: key %s not supported",
439 epayload->master_desc);
440 else
441 pr_info("encrypted_key: key %s not found",
442 epayload->master_desc);
443 goto out;
444 }
445
446 dump_master_key(*master_key, *master_keylen);
447 out:
448 return mkey;
449 }
450
451 /* Before returning data to userspace, encrypt decrypted data. */
derived_key_encrypt(struct encrypted_key_payload * epayload,const u8 * derived_key,unsigned int derived_keylen)452 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
453 const u8 *derived_key,
454 unsigned int derived_keylen)
455 {
456 struct scatterlist sg_in[2];
457 struct scatterlist sg_out[1];
458 struct crypto_skcipher *tfm;
459 struct skcipher_request *req;
460 unsigned int encrypted_datalen;
461 u8 iv[AES_BLOCK_SIZE];
462 int ret;
463
464 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
465
466 req = init_skcipher_req(derived_key, derived_keylen);
467 ret = PTR_ERR(req);
468 if (IS_ERR(req))
469 goto out;
470 dump_decrypted_data(epayload);
471
472 sg_init_table(sg_in, 2);
473 sg_set_buf(&sg_in[0], epayload->decrypted_data,
474 epayload->decrypted_datalen);
475 sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
476
477 sg_init_table(sg_out, 1);
478 sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
479
480 memcpy(iv, epayload->iv, sizeof(iv));
481 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
482 ret = crypto_skcipher_encrypt(req);
483 tfm = crypto_skcipher_reqtfm(req);
484 skcipher_request_free(req);
485 crypto_free_skcipher(tfm);
486 if (ret < 0)
487 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
488 else
489 dump_encrypted_data(epayload, encrypted_datalen);
490 out:
491 return ret;
492 }
493
datablob_hmac_append(struct encrypted_key_payload * epayload,const u8 * master_key,size_t master_keylen)494 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
495 const u8 *master_key, size_t master_keylen)
496 {
497 u8 derived_key[HASH_SIZE];
498 u8 *digest;
499 int ret;
500
501 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
502 if (ret < 0)
503 goto out;
504
505 digest = epayload->format + epayload->datablob_len;
506 ret = calc_hmac(digest, derived_key, sizeof derived_key,
507 epayload->format, epayload->datablob_len);
508 if (!ret)
509 dump_hmac(NULL, digest, HASH_SIZE);
510 out:
511 memzero_explicit(derived_key, sizeof(derived_key));
512 return ret;
513 }
514
515 /* verify HMAC before decrypting encrypted key */
datablob_hmac_verify(struct encrypted_key_payload * epayload,const u8 * format,const u8 * master_key,size_t master_keylen)516 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
517 const u8 *format, const u8 *master_key,
518 size_t master_keylen)
519 {
520 u8 derived_key[HASH_SIZE];
521 u8 digest[HASH_SIZE];
522 int ret;
523 char *p;
524 unsigned short len;
525
526 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
527 if (ret < 0)
528 goto out;
529
530 len = epayload->datablob_len;
531 if (!format) {
532 p = epayload->master_desc;
533 len -= strlen(epayload->format) + 1;
534 } else
535 p = epayload->format;
536
537 ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
538 if (ret < 0)
539 goto out;
540 ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
541 sizeof(digest));
542 if (ret) {
543 ret = -EINVAL;
544 dump_hmac("datablob",
545 epayload->format + epayload->datablob_len,
546 HASH_SIZE);
547 dump_hmac("calc", digest, HASH_SIZE);
548 }
549 out:
550 memzero_explicit(derived_key, sizeof(derived_key));
551 return ret;
552 }
553
derived_key_decrypt(struct encrypted_key_payload * epayload,const u8 * derived_key,unsigned int derived_keylen)554 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
555 const u8 *derived_key,
556 unsigned int derived_keylen)
557 {
558 struct scatterlist sg_in[1];
559 struct scatterlist sg_out[2];
560 struct crypto_skcipher *tfm;
561 struct skcipher_request *req;
562 unsigned int encrypted_datalen;
563 u8 iv[AES_BLOCK_SIZE];
564 u8 *pad;
565 int ret;
566
567 /* Throwaway buffer to hold the unused zero padding at the end */
568 pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
569 if (!pad)
570 return -ENOMEM;
571
572 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
573 req = init_skcipher_req(derived_key, derived_keylen);
574 ret = PTR_ERR(req);
575 if (IS_ERR(req))
576 goto out;
577 dump_encrypted_data(epayload, encrypted_datalen);
578
579 sg_init_table(sg_in, 1);
580 sg_init_table(sg_out, 2);
581 sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
582 sg_set_buf(&sg_out[0], epayload->decrypted_data,
583 epayload->decrypted_datalen);
584 sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
585
586 memcpy(iv, epayload->iv, sizeof(iv));
587 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
588 ret = crypto_skcipher_decrypt(req);
589 tfm = crypto_skcipher_reqtfm(req);
590 skcipher_request_free(req);
591 crypto_free_skcipher(tfm);
592 if (ret < 0)
593 goto out;
594 dump_decrypted_data(epayload);
595 out:
596 kfree(pad);
597 return ret;
598 }
599
600 /* Allocate memory for decrypted key and datablob. */
encrypted_key_alloc(struct key * key,const char * format,const char * master_desc,const char * datalen,const char * decrypted_data)601 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
602 const char *format,
603 const char *master_desc,
604 const char *datalen,
605 const char *decrypted_data)
606 {
607 struct encrypted_key_payload *epayload = NULL;
608 unsigned short datablob_len;
609 unsigned short decrypted_datalen;
610 unsigned short payload_datalen;
611 unsigned int encrypted_datalen;
612 unsigned int format_len;
613 long dlen;
614 int i;
615 int ret;
616
617 ret = kstrtol(datalen, 10, &dlen);
618 if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
619 return ERR_PTR(-EINVAL);
620
621 format_len = (!format) ? strlen(key_format_default) : strlen(format);
622 decrypted_datalen = dlen;
623 payload_datalen = decrypted_datalen;
624
625 if (decrypted_data) {
626 if (!user_decrypted_data) {
627 pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n");
628 return ERR_PTR(-EINVAL);
629 }
630 if (strlen(decrypted_data) != decrypted_datalen * 2) {
631 pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n");
632 return ERR_PTR(-EINVAL);
633 }
634 for (i = 0; i < strlen(decrypted_data); i++) {
635 if (!isxdigit(decrypted_data[i])) {
636 pr_err("encrypted key: decrypted data provided must contain only hexadecimal characters\n");
637 return ERR_PTR(-EINVAL);
638 }
639 }
640 }
641
642 if (format) {
643 if (!strcmp(format, key_format_ecryptfs)) {
644 if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
645 pr_err("encrypted_key: keylen for the ecryptfs format must be equal to %d bytes\n",
646 ECRYPTFS_MAX_KEY_BYTES);
647 return ERR_PTR(-EINVAL);
648 }
649 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
650 payload_datalen = sizeof(struct ecryptfs_auth_tok);
651 } else if (!strcmp(format, key_format_enc32)) {
652 if (decrypted_datalen != KEY_ENC32_PAYLOAD_LEN) {
653 pr_err("encrypted_key: enc32 key payload incorrect length: %d\n",
654 decrypted_datalen);
655 return ERR_PTR(-EINVAL);
656 }
657 }
658 }
659
660 encrypted_datalen = roundup(decrypted_datalen, blksize);
661
662 datablob_len = format_len + 1 + strlen(master_desc) + 1
663 + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
664
665 ret = key_payload_reserve(key, payload_datalen + datablob_len
666 + HASH_SIZE + 1);
667 if (ret < 0)
668 return ERR_PTR(ret);
669
670 epayload = kzalloc(sizeof(*epayload) + payload_datalen +
671 datablob_len + HASH_SIZE + 1, GFP_KERNEL);
672 if (!epayload)
673 return ERR_PTR(-ENOMEM);
674
675 epayload->payload_datalen = payload_datalen;
676 epayload->decrypted_datalen = decrypted_datalen;
677 epayload->datablob_len = datablob_len;
678 return epayload;
679 }
680
encrypted_key_decrypt(struct encrypted_key_payload * epayload,const char * format,const char * hex_encoded_iv)681 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
682 const char *format, const char *hex_encoded_iv)
683 {
684 struct key *mkey;
685 u8 derived_key[HASH_SIZE];
686 const u8 *master_key;
687 u8 *hmac;
688 const char *hex_encoded_data;
689 unsigned int encrypted_datalen;
690 size_t master_keylen;
691 size_t asciilen;
692 int ret;
693
694 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
695 asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
696 if (strlen(hex_encoded_iv) != asciilen)
697 return -EINVAL;
698
699 hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
700 ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
701 if (ret < 0)
702 return -EINVAL;
703 ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
704 encrypted_datalen);
705 if (ret < 0)
706 return -EINVAL;
707
708 hmac = epayload->format + epayload->datablob_len;
709 ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
710 HASH_SIZE);
711 if (ret < 0)
712 return -EINVAL;
713
714 mkey = request_master_key(epayload, &master_key, &master_keylen);
715 if (IS_ERR(mkey))
716 return PTR_ERR(mkey);
717
718 ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
719 if (ret < 0) {
720 pr_err("encrypted_key: bad hmac (%d)\n", ret);
721 goto out;
722 }
723
724 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
725 if (ret < 0)
726 goto out;
727
728 ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
729 if (ret < 0)
730 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
731 out:
732 up_read(&mkey->sem);
733 key_put(mkey);
734 memzero_explicit(derived_key, sizeof(derived_key));
735 return ret;
736 }
737
__ekey_init(struct encrypted_key_payload * epayload,const char * format,const char * master_desc,const char * datalen)738 static void __ekey_init(struct encrypted_key_payload *epayload,
739 const char *format, const char *master_desc,
740 const char *datalen)
741 {
742 unsigned int format_len;
743
744 format_len = (!format) ? strlen(key_format_default) : strlen(format);
745 epayload->format = epayload->payload_data + epayload->payload_datalen;
746 epayload->master_desc = epayload->format + format_len + 1;
747 epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
748 epayload->iv = epayload->datalen + strlen(datalen) + 1;
749 epayload->encrypted_data = epayload->iv + ivsize + 1;
750 epayload->decrypted_data = epayload->payload_data;
751
752 if (!format)
753 memcpy(epayload->format, key_format_default, format_len);
754 else {
755 if (!strcmp(format, key_format_ecryptfs))
756 epayload->decrypted_data =
757 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
758
759 memcpy(epayload->format, format, format_len);
760 }
761
762 memcpy(epayload->master_desc, master_desc, strlen(master_desc));
763 memcpy(epayload->datalen, datalen, strlen(datalen));
764 }
765
766 /*
767 * encrypted_init - initialize an encrypted key
768 *
769 * For a new key, use either a random number or user-provided decrypted data in
770 * case it is provided. A random number is used for the iv in both cases. For
771 * an old key, decrypt the hex encoded data.
772 */
encrypted_init(struct encrypted_key_payload * epayload,const char * key_desc,const char * format,const char * master_desc,const char * datalen,const char * hex_encoded_iv,const char * decrypted_data)773 static int encrypted_init(struct encrypted_key_payload *epayload,
774 const char *key_desc, const char *format,
775 const char *master_desc, const char *datalen,
776 const char *hex_encoded_iv, const char *decrypted_data)
777 {
778 int ret = 0;
779
780 if (format && !strcmp(format, key_format_ecryptfs)) {
781 ret = valid_ecryptfs_desc(key_desc);
782 if (ret < 0)
783 return ret;
784
785 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
786 key_desc);
787 }
788
789 __ekey_init(epayload, format, master_desc, datalen);
790 if (hex_encoded_iv) {
791 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
792 } else if (decrypted_data) {
793 get_random_bytes(epayload->iv, ivsize);
794 ret = hex2bin(epayload->decrypted_data, decrypted_data,
795 epayload->decrypted_datalen);
796 } else {
797 get_random_bytes(epayload->iv, ivsize);
798 get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen);
799 }
800 return ret;
801 }
802
803 /*
804 * encrypted_instantiate - instantiate an encrypted key
805 *
806 * Instantiates the key:
807 * - by decrypting an existing encrypted datablob, or
808 * - by creating a new encrypted key based on a kernel random number, or
809 * - using provided decrypted data.
810 *
811 * On success, return 0. Otherwise return errno.
812 */
encrypted_instantiate(struct key * key,struct key_preparsed_payload * prep)813 static int encrypted_instantiate(struct key *key,
814 struct key_preparsed_payload *prep)
815 {
816 struct encrypted_key_payload *epayload = NULL;
817 char *datablob = NULL;
818 const char *format = NULL;
819 char *master_desc = NULL;
820 char *decrypted_datalen = NULL;
821 char *hex_encoded_iv = NULL;
822 char *decrypted_data = NULL;
823 size_t datalen = prep->datalen;
824 int ret;
825
826 if (datalen <= 0 || datalen > 32767 || !prep->data)
827 return -EINVAL;
828
829 datablob = kmalloc(datalen + 1, GFP_KERNEL);
830 if (!datablob)
831 return -ENOMEM;
832 datablob[datalen] = 0;
833 memcpy(datablob, prep->data, datalen);
834 ret = datablob_parse(datablob, &format, &master_desc,
835 &decrypted_datalen, &hex_encoded_iv, &decrypted_data);
836 if (ret < 0)
837 goto out;
838
839 epayload = encrypted_key_alloc(key, format, master_desc,
840 decrypted_datalen, decrypted_data);
841 if (IS_ERR(epayload)) {
842 ret = PTR_ERR(epayload);
843 goto out;
844 }
845 ret = encrypted_init(epayload, key->description, format, master_desc,
846 decrypted_datalen, hex_encoded_iv, decrypted_data);
847 if (ret < 0) {
848 kfree_sensitive(epayload);
849 goto out;
850 }
851
852 rcu_assign_keypointer(key, epayload);
853 out:
854 kfree_sensitive(datablob);
855 return ret;
856 }
857
encrypted_rcu_free(struct rcu_head * rcu)858 static void encrypted_rcu_free(struct rcu_head *rcu)
859 {
860 struct encrypted_key_payload *epayload;
861
862 epayload = container_of(rcu, struct encrypted_key_payload, rcu);
863 kfree_sensitive(epayload);
864 }
865
866 /*
867 * encrypted_update - update the master key description
868 *
869 * Change the master key description for an existing encrypted key.
870 * The next read will return an encrypted datablob using the new
871 * master key description.
872 *
873 * On success, return 0. Otherwise return errno.
874 */
encrypted_update(struct key * key,struct key_preparsed_payload * prep)875 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
876 {
877 struct encrypted_key_payload *epayload = key->payload.data[0];
878 struct encrypted_key_payload *new_epayload;
879 char *buf;
880 char *new_master_desc = NULL;
881 const char *format = NULL;
882 size_t datalen = prep->datalen;
883 int ret = 0;
884
885 if (key_is_negative(key))
886 return -ENOKEY;
887 if (datalen <= 0 || datalen > 32767 || !prep->data)
888 return -EINVAL;
889
890 buf = kmalloc(datalen + 1, GFP_KERNEL);
891 if (!buf)
892 return -ENOMEM;
893
894 buf[datalen] = 0;
895 memcpy(buf, prep->data, datalen);
896 ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL, NULL);
897 if (ret < 0)
898 goto out;
899
900 ret = valid_master_desc(new_master_desc, epayload->master_desc);
901 if (ret < 0)
902 goto out;
903
904 new_epayload = encrypted_key_alloc(key, epayload->format,
905 new_master_desc, epayload->datalen, NULL);
906 if (IS_ERR(new_epayload)) {
907 ret = PTR_ERR(new_epayload);
908 goto out;
909 }
910
911 __ekey_init(new_epayload, epayload->format, new_master_desc,
912 epayload->datalen);
913
914 memcpy(new_epayload->iv, epayload->iv, ivsize);
915 memcpy(new_epayload->payload_data, epayload->payload_data,
916 epayload->payload_datalen);
917
918 rcu_assign_keypointer(key, new_epayload);
919 call_rcu(&epayload->rcu, encrypted_rcu_free);
920 out:
921 kfree_sensitive(buf);
922 return ret;
923 }
924
925 /*
926 * encrypted_read - format and copy out the encrypted data
927 *
928 * The resulting datablob format is:
929 * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
930 *
931 * On success, return to userspace the encrypted key datablob size.
932 */
encrypted_read(const struct key * key,char * buffer,size_t buflen)933 static long encrypted_read(const struct key *key, char *buffer,
934 size_t buflen)
935 {
936 struct encrypted_key_payload *epayload;
937 struct key *mkey;
938 const u8 *master_key;
939 size_t master_keylen;
940 char derived_key[HASH_SIZE];
941 char *ascii_buf;
942 size_t asciiblob_len;
943 int ret;
944
945 epayload = dereference_key_locked(key);
946
947 /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
948 asciiblob_len = epayload->datablob_len + ivsize + 1
949 + roundup(epayload->decrypted_datalen, blksize)
950 + (HASH_SIZE * 2);
951
952 if (!buffer || buflen < asciiblob_len)
953 return asciiblob_len;
954
955 mkey = request_master_key(epayload, &master_key, &master_keylen);
956 if (IS_ERR(mkey))
957 return PTR_ERR(mkey);
958
959 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
960 if (ret < 0)
961 goto out;
962
963 ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
964 if (ret < 0)
965 goto out;
966
967 ret = datablob_hmac_append(epayload, master_key, master_keylen);
968 if (ret < 0)
969 goto out;
970
971 ascii_buf = datablob_format(epayload, asciiblob_len);
972 if (!ascii_buf) {
973 ret = -ENOMEM;
974 goto out;
975 }
976
977 up_read(&mkey->sem);
978 key_put(mkey);
979 memzero_explicit(derived_key, sizeof(derived_key));
980
981 memcpy(buffer, ascii_buf, asciiblob_len);
982 kfree_sensitive(ascii_buf);
983
984 return asciiblob_len;
985 out:
986 up_read(&mkey->sem);
987 key_put(mkey);
988 memzero_explicit(derived_key, sizeof(derived_key));
989 return ret;
990 }
991
992 /*
993 * encrypted_destroy - clear and free the key's payload
994 */
encrypted_destroy(struct key * key)995 static void encrypted_destroy(struct key *key)
996 {
997 kfree_sensitive(key->payload.data[0]);
998 }
999
1000 struct key_type key_type_encrypted = {
1001 .name = "encrypted",
1002 .instantiate = encrypted_instantiate,
1003 .update = encrypted_update,
1004 .destroy = encrypted_destroy,
1005 .describe = user_describe,
1006 .read = encrypted_read,
1007 };
1008 EXPORT_SYMBOL_GPL(key_type_encrypted);
1009
init_encrypted(void)1010 static int __init init_encrypted(void)
1011 {
1012 int ret;
1013
1014 hash_tfm = crypto_alloc_shash(hash_alg, 0, 0);
1015 if (IS_ERR(hash_tfm)) {
1016 pr_err("encrypted_key: can't allocate %s transform: %ld\n",
1017 hash_alg, PTR_ERR(hash_tfm));
1018 return PTR_ERR(hash_tfm);
1019 }
1020
1021 ret = aes_get_sizes();
1022 if (ret < 0)
1023 goto out;
1024 ret = register_key_type(&key_type_encrypted);
1025 if (ret < 0)
1026 goto out;
1027 return 0;
1028 out:
1029 crypto_free_shash(hash_tfm);
1030 return ret;
1031
1032 }
1033
cleanup_encrypted(void)1034 static void __exit cleanup_encrypted(void)
1035 {
1036 crypto_free_shash(hash_tfm);
1037 unregister_key_type(&key_type_encrypted);
1038 }
1039
1040 late_initcall(init_encrypted);
1041 module_exit(cleanup_encrypted);
1042
1043 MODULE_DESCRIPTION("Encrypted key type");
1044 MODULE_LICENSE("GPL");
1045