2 * Copyright (C) 2010 IBM Corporation
3 * Copyright (C) 2010 Politecnico di Torino, Italy
4 * TORSEC group -- http://security.polito.it
7 * Mimi Zohar <zohar@us.ibm.com>
8 * Roberto Sassu <roberto.sassu@polito.it>
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.
14 * See Documentation/security/keys-trusted-encrypted.txt
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>
38 #include "encrypted.h"
39 #include "ecryptfs_format.h"
41 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
42 static const char KEY_USER_PREFIX[] = "user:";
43 static const char hash_alg[] = "sha256";
44 static const char hmac_alg[] = "hmac(sha256)";
45 static const char blkcipher_alg[] = "cbc(aes)";
46 static const char key_format_default[] = "default";
47 static const char key_format_ecryptfs[] = "ecryptfs";
48 static unsigned int ivsize;
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
58 static struct crypto_shash *hash_tfm;
61 Opt_err = -1, Opt_new, Opt_load, Opt_update
65 Opt_error = -1, Opt_default, Opt_ecryptfs
68 static const match_table_t key_format_tokens = {
69 {Opt_default, "default"},
70 {Opt_ecryptfs, "ecryptfs"},
74 static const match_table_t key_tokens = {
77 {Opt_update, "update"},
81 static int aes_get_sizes(void)
83 struct crypto_skcipher *tfm;
85 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
87 pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
91 ivsize = crypto_skcipher_ivsize(tfm);
92 blksize = crypto_skcipher_blocksize(tfm);
93 crypto_free_skcipher(tfm);
98 * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
100 * The description of a encrypted key with format 'ecryptfs' must contain
101 * exactly 16 hexadecimal characters.
104 static int valid_ecryptfs_desc(const char *ecryptfs_desc)
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);
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");
126 * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
128 * key-type:= "trusted:" | "user:"
129 * desc:= master-key description
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.
135 * On success returns 0, otherwise -EINVAL.
137 static int valid_master_desc(const char *new_desc, const char *orig_desc)
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;
148 if (!new_desc[prefix_len])
151 if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
158 * datablob_parse - parse the keyctl data
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>
166 * Tokenizes a copy of the keyctl data, returning a pointer to each token,
167 * which is null terminated.
169 * On success returns 0, otherwise -EINVAL.
171 static int datablob_parse(char *datablob, const char **format,
172 char **master_desc, char **decrypted_datalen,
173 char **hex_encoded_iv)
175 substring_t args[MAX_OPT_ARGS];
181 keyword = strsep(&datablob, " \t");
183 pr_info("encrypted_key: insufficient parameters specified\n");
186 key_cmd = match_token(keyword, key_tokens, args);
188 /* Get optional format: default | ecryptfs */
189 p = strsep(&datablob, " \t");
191 pr_err("encrypted_key: insufficient parameters specified\n");
195 key_format = match_token(p, key_format_tokens, args);
196 switch (key_format) {
200 *master_desc = strsep(&datablob, " \t");
208 pr_info("encrypted_key: master key parameter is missing\n");
212 if (valid_master_desc(*master_desc, NULL) < 0) {
213 pr_info("encrypted_key: master key parameter \'%s\' "
214 "is invalid\n", *master_desc);
218 if (decrypted_datalen) {
219 *decrypted_datalen = strsep(&datablob, " \t");
220 if (!*decrypted_datalen) {
221 pr_info("encrypted_key: keylen parameter is missing\n");
228 if (!decrypted_datalen) {
229 pr_info("encrypted_key: keyword \'%s\' not allowed "
230 "when called from .update method\n", keyword);
236 if (!decrypted_datalen) {
237 pr_info("encrypted_key: keyword \'%s\' not allowed "
238 "when called from .update method\n", keyword);
241 *hex_encoded_iv = strsep(&datablob, " \t");
242 if (!*hex_encoded_iv) {
243 pr_info("encrypted_key: hex blob is missing\n");
249 if (decrypted_datalen) {
250 pr_info("encrypted_key: keyword \'%s\' not allowed "
251 "when called from .instantiate method\n",
258 pr_info("encrypted_key: keyword \'%s\' not recognized\n",
267 * datablob_format - format as an ascii string, before copying to userspace
269 static char *datablob_format(struct encrypted_key_payload *epayload,
270 size_t asciiblob_len)
272 char *ascii_buf, *bufp;
273 u8 *iv = epayload->iv;
277 ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
281 ascii_buf[asciiblob_len] = '\0';
283 /* copy datablob master_desc and datalen strings */
284 len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
285 epayload->master_desc, epayload->datalen);
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]);
296 * request_user_key - request the user key
298 * Use a user provided key to encrypt/decrypt an encrypted-key.
300 static struct key *request_user_key(const char *master_desc, const u8 **master_key,
301 size_t *master_keylen)
303 const struct user_key_payload *upayload;
306 ukey = request_key(&key_type_user, master_desc, NULL);
310 down_read(&ukey->sem);
311 upayload = user_key_payload_locked(ukey);
312 *master_key = upayload->data;
313 *master_keylen = upayload->datalen;
318 static int calc_hash(struct crypto_shash *tfm, u8 *digest,
319 const u8 *buf, unsigned int buflen)
321 SHASH_DESC_ON_STACK(desc, tfm);
327 err = crypto_shash_digest(desc, buf, buflen, digest);
328 shash_desc_zero(desc);
332 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
333 const u8 *buf, unsigned int buflen)
335 struct crypto_shash *tfm;
338 tfm = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
340 pr_err("encrypted_key: can't alloc %s transform: %ld\n",
341 hmac_alg, PTR_ERR(tfm));
345 err = crypto_shash_setkey(tfm, key, keylen);
347 err = calc_hash(tfm, digest, buf, buflen);
348 crypto_free_shash(tfm);
352 enum derived_key_type { ENC_KEY, AUTH_KEY };
354 /* Derive authentication/encryption key from trusted key */
355 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
356 const u8 *master_key, size_t master_keylen)
359 unsigned int derived_buf_len;
362 derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
363 if (derived_buf_len < HASH_SIZE)
364 derived_buf_len = HASH_SIZE;
366 derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
371 strcpy(derived_buf, "AUTH_KEY");
373 strcpy(derived_buf, "ENC_KEY");
375 memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
377 ret = calc_hash(hash_tfm, derived_key, derived_buf, derived_buf_len);
382 static struct skcipher_request *init_skcipher_req(const u8 *key,
383 unsigned int key_len)
385 struct skcipher_request *req;
386 struct crypto_skcipher *tfm;
389 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
391 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
392 blkcipher_alg, PTR_ERR(tfm));
393 return ERR_CAST(tfm);
396 ret = crypto_skcipher_setkey(tfm, key, key_len);
398 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
399 crypto_free_skcipher(tfm);
403 req = skcipher_request_alloc(tfm, GFP_KERNEL);
405 pr_err("encrypted_key: failed to allocate request for %s\n",
407 crypto_free_skcipher(tfm);
408 return ERR_PTR(-ENOMEM);
411 skcipher_request_set_callback(req, 0, NULL, NULL);
415 static struct key *request_master_key(struct encrypted_key_payload *epayload,
416 const u8 **master_key, size_t *master_keylen)
418 struct key *mkey = ERR_PTR(-EINVAL);
420 if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
421 KEY_TRUSTED_PREFIX_LEN)) {
422 mkey = request_trusted_key(epayload->master_desc +
423 KEY_TRUSTED_PREFIX_LEN,
424 master_key, master_keylen);
425 } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
426 KEY_USER_PREFIX_LEN)) {
427 mkey = request_user_key(epayload->master_desc +
429 master_key, master_keylen);
434 int ret = PTR_ERR(mkey);
436 if (ret == -ENOTSUPP)
437 pr_info("encrypted_key: key %s not supported",
438 epayload->master_desc);
440 pr_info("encrypted_key: key %s not found",
441 epayload->master_desc);
445 dump_master_key(*master_key, *master_keylen);
450 /* Before returning data to userspace, encrypt decrypted data. */
451 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
452 const u8 *derived_key,
453 unsigned int derived_keylen)
455 struct scatterlist sg_in[2];
456 struct scatterlist sg_out[1];
457 struct crypto_skcipher *tfm;
458 struct skcipher_request *req;
459 unsigned int encrypted_datalen;
460 u8 iv[AES_BLOCK_SIZE];
463 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
465 req = init_skcipher_req(derived_key, derived_keylen);
469 dump_decrypted_data(epayload);
471 sg_init_table(sg_in, 2);
472 sg_set_buf(&sg_in[0], epayload->decrypted_data,
473 epayload->decrypted_datalen);
474 sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
476 sg_init_table(sg_out, 1);
477 sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
479 memcpy(iv, epayload->iv, sizeof(iv));
480 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
481 ret = crypto_skcipher_encrypt(req);
482 tfm = crypto_skcipher_reqtfm(req);
483 skcipher_request_free(req);
484 crypto_free_skcipher(tfm);
486 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
488 dump_encrypted_data(epayload, encrypted_datalen);
493 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
494 const u8 *master_key, size_t master_keylen)
496 u8 derived_key[HASH_SIZE];
500 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
504 digest = epayload->format + epayload->datablob_len;
505 ret = calc_hmac(digest, derived_key, sizeof derived_key,
506 epayload->format, epayload->datablob_len);
508 dump_hmac(NULL, digest, HASH_SIZE);
513 /* verify HMAC before decrypting encrypted key */
514 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
515 const u8 *format, const u8 *master_key,
516 size_t master_keylen)
518 u8 derived_key[HASH_SIZE];
519 u8 digest[HASH_SIZE];
524 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
528 len = epayload->datablob_len;
530 p = epayload->master_desc;
531 len -= strlen(epayload->format) + 1;
533 p = epayload->format;
535 ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
538 ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
542 dump_hmac("datablob",
543 epayload->format + epayload->datablob_len,
545 dump_hmac("calc", digest, HASH_SIZE);
551 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
552 const u8 *derived_key,
553 unsigned int derived_keylen)
555 struct scatterlist sg_in[1];
556 struct scatterlist sg_out[2];
557 struct crypto_skcipher *tfm;
558 struct skcipher_request *req;
559 unsigned int encrypted_datalen;
560 u8 iv[AES_BLOCK_SIZE];
564 /* Throwaway buffer to hold the unused zero padding at the end */
565 pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
569 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
570 req = init_skcipher_req(derived_key, derived_keylen);
574 dump_encrypted_data(epayload, encrypted_datalen);
576 sg_init_table(sg_in, 1);
577 sg_init_table(sg_out, 2);
578 sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
579 sg_set_buf(&sg_out[0], epayload->decrypted_data,
580 epayload->decrypted_datalen);
581 sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
583 memcpy(iv, epayload->iv, sizeof(iv));
584 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
585 ret = crypto_skcipher_decrypt(req);
586 tfm = crypto_skcipher_reqtfm(req);
587 skcipher_request_free(req);
588 crypto_free_skcipher(tfm);
591 dump_decrypted_data(epayload);
597 /* Allocate memory for decrypted key and datablob. */
598 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
600 const char *master_desc,
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;
612 ret = kstrtol(datalen, 10, &dlen);
613 if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
614 return ERR_PTR(-EINVAL);
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);
626 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
627 payload_datalen = sizeof(struct ecryptfs_auth_tok);
630 encrypted_datalen = roundup(decrypted_datalen, blksize);
632 datablob_len = format_len + 1 + strlen(master_desc) + 1
633 + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
635 ret = key_payload_reserve(key, payload_datalen + datablob_len
640 epayload = kzalloc(sizeof(*epayload) + payload_datalen +
641 datablob_len + HASH_SIZE + 1, GFP_KERNEL);
643 return ERR_PTR(-ENOMEM);
645 epayload->payload_datalen = payload_datalen;
646 epayload->decrypted_datalen = decrypted_datalen;
647 epayload->datablob_len = datablob_len;
651 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
652 const char *format, const char *hex_encoded_iv)
655 u8 derived_key[HASH_SIZE];
656 const u8 *master_key;
658 const char *hex_encoded_data;
659 unsigned int encrypted_datalen;
660 size_t master_keylen;
664 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
665 asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
666 if (strlen(hex_encoded_iv) != asciilen)
669 hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
670 ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
673 ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
678 hmac = epayload->format + epayload->datablob_len;
679 ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
684 mkey = request_master_key(epayload, &master_key, &master_keylen);
686 return PTR_ERR(mkey);
688 ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
690 pr_err("encrypted_key: bad hmac (%d)\n", ret);
694 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
698 ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
700 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
707 static void __ekey_init(struct encrypted_key_payload *epayload,
708 const char *format, const char *master_desc,
711 unsigned int format_len;
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;
722 memcpy(epayload->format, key_format_default, format_len);
724 if (!strcmp(format, key_format_ecryptfs))
725 epayload->decrypted_data =
726 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
728 memcpy(epayload->format, format, format_len);
731 memcpy(epayload->master_desc, master_desc, strlen(master_desc));
732 memcpy(epayload->datalen, datalen, strlen(datalen));
736 * encrypted_init - initialize an encrypted key
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.
741 static 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)
748 if (format && !strcmp(format, key_format_ecryptfs)) {
749 ret = valid_ecryptfs_desc(key_desc);
753 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
757 __ekey_init(epayload, format, master_desc, datalen);
758 if (!hex_encoded_iv) {
759 get_random_bytes(epayload->iv, ivsize);
761 get_random_bytes(epayload->decrypted_data,
762 epayload->decrypted_datalen);
764 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
769 * encrypted_instantiate - instantiate an encrypted key
771 * Decrypt an existing encrypted datablob or create a new encrypted key
772 * based on a kernel random number.
774 * On success, return 0. Otherwise return errno.
776 static int encrypted_instantiate(struct key *key,
777 struct key_preparsed_payload *prep)
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;
788 if (datalen <= 0 || datalen > 32767 || !prep->data)
791 datablob = kmalloc(datalen + 1, GFP_KERNEL);
794 datablob[datalen] = 0;
795 memcpy(datablob, prep->data, datalen);
796 ret = datablob_parse(datablob, &format, &master_desc,
797 &decrypted_datalen, &hex_encoded_iv);
801 epayload = encrypted_key_alloc(key, format, master_desc,
803 if (IS_ERR(epayload)) {
804 ret = PTR_ERR(epayload);
807 ret = encrypted_init(epayload, key->description, format, master_desc,
808 decrypted_datalen, hex_encoded_iv);
814 rcu_assign_keypointer(key, epayload);
820 static void encrypted_rcu_free(struct rcu_head *rcu)
822 struct encrypted_key_payload *epayload;
824 epayload = container_of(rcu, struct encrypted_key_payload, rcu);
825 memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
830 * encrypted_update - update the master key description
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.
836 * On success, return 0. Otherwise return errno.
838 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
840 struct encrypted_key_payload *epayload = key->payload.data[0];
841 struct encrypted_key_payload *new_epayload;
843 char *new_master_desc = NULL;
844 const char *format = NULL;
845 size_t datalen = prep->datalen;
848 if (test_bit(KEY_FLAG_NEGATIVE, &key->flags))
850 if (datalen <= 0 || datalen > 32767 || !prep->data)
853 buf = kmalloc(datalen + 1, GFP_KERNEL);
858 memcpy(buf, prep->data, datalen);
859 ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
863 ret = valid_master_desc(new_master_desc, epayload->master_desc);
867 new_epayload = encrypted_key_alloc(key, epayload->format,
868 new_master_desc, epayload->datalen);
869 if (IS_ERR(new_epayload)) {
870 ret = PTR_ERR(new_epayload);
874 __ekey_init(new_epayload, epayload->format, new_master_desc,
877 memcpy(new_epayload->iv, epayload->iv, ivsize);
878 memcpy(new_epayload->payload_data, epayload->payload_data,
879 epayload->payload_datalen);
881 rcu_assign_keypointer(key, new_epayload);
882 call_rcu(&epayload->rcu, encrypted_rcu_free);
889 * encrypted_read - format and copy the encrypted data to userspace
891 * The resulting datablob format is:
892 * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
894 * On success, return to userspace the encrypted key datablob size.
896 static long encrypted_read(const struct key *key, char __user *buffer,
899 struct encrypted_key_payload *epayload;
901 const u8 *master_key;
902 size_t master_keylen;
903 char derived_key[HASH_SIZE];
905 size_t asciiblob_len;
908 epayload = dereference_key_locked(key);
910 /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
911 asciiblob_len = epayload->datablob_len + ivsize + 1
912 + roundup(epayload->decrypted_datalen, blksize)
915 if (!buffer || buflen < asciiblob_len)
916 return asciiblob_len;
918 mkey = request_master_key(epayload, &master_key, &master_keylen);
920 return PTR_ERR(mkey);
922 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
926 ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
930 ret = datablob_hmac_append(epayload, master_key, master_keylen);
934 ascii_buf = datablob_format(epayload, asciiblob_len);
943 if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
947 return asciiblob_len;
955 * encrypted_destroy - before freeing the key, clear the decrypted data
957 * Before freeing the key, clear the memory containing the decrypted
960 static void encrypted_destroy(struct key *key)
962 struct encrypted_key_payload *epayload = key->payload.data[0];
967 memzero_explicit(epayload->decrypted_data, epayload->decrypted_datalen);
968 kfree(key->payload.data[0]);
971 struct key_type key_type_encrypted = {
973 .instantiate = encrypted_instantiate,
974 .update = encrypted_update,
975 .destroy = encrypted_destroy,
976 .describe = user_describe,
977 .read = encrypted_read,
979 EXPORT_SYMBOL_GPL(key_type_encrypted);
981 static int __init init_encrypted(void)
985 hash_tfm = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
986 if (IS_ERR(hash_tfm)) {
987 pr_err("encrypted_key: can't allocate %s transform: %ld\n",
988 hash_alg, PTR_ERR(hash_tfm));
989 return PTR_ERR(hash_tfm);
992 ret = aes_get_sizes();
995 ret = register_key_type(&key_type_encrypted);
1000 crypto_free_shash(hash_tfm);
1005 static void __exit cleanup_encrypted(void)
1007 crypto_free_shash(hash_tfm);
1008 unregister_key_type(&key_type_encrypted);
1011 late_initcall(init_encrypted);
1012 module_exit(cleanup_encrypted);
1014 MODULE_LICENSE("GPL");