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TOMOYO Linux Cross Reference
Linux/security/keys/encrypted-keys/encrypted.c

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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 
 40 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
 41 static const char KEY_USER_PREFIX[] = "user:";
 42 static const char hash_alg[] = "sha256";
 43 static const char hmac_alg[] = "hmac(sha256)";
 44 static const char blkcipher_alg[] = "cbc(aes)";
 45 static const char key_format_default[] = "default";
 46 static const char key_format_ecryptfs[] = "ecryptfs";
 47 static unsigned int ivsize;
 48 static 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 
 57 struct sdesc {
 58         struct shash_desc shash;
 59         char ctx[];
 60 };
 61 
 62 static struct crypto_shash *hashalg;
 63 static struct crypto_shash *hmacalg;
 64 
 65 enum {
 66         Opt_err = -1, Opt_new, Opt_load, Opt_update
 67 };
 68 
 69 enum {
 70         Opt_error = -1, Opt_default, Opt_ecryptfs
 71 };
 72 
 73 static const match_table_t key_format_tokens = {
 74         {Opt_default, "default"},
 75         {Opt_ecryptfs, "ecryptfs"},
 76         {Opt_error, NULL}
 77 };
 78 
 79 static const match_table_t key_tokens = {
 80         {Opt_new, "new"},
 81         {Opt_load, "load"},
 82         {Opt_update, "update"},
 83         {Opt_err, NULL}
 84 };
 85 
 86 static 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  */
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  */
142 static 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;
159 out:
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  */
177 static 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         }
268 out:
269         return ret;
270 }
271 
272 /*
273  * datablob_format - format as an ascii string, before copying to userspace
274  */
275 static 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]);
297 out:
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  */
306 static 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;
320 error:
321         return ukey;
322 }
323 
324 static 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 
338 static 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 
357 static 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 
373 enum derived_key_type { ENC_KEY, AUTH_KEY };
374 
375 /* Derive authentication/encryption key from trusted key */
376 static 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 
404 static 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 
428 static 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);
459 out:
460         return mkey;
461 }
462 
463 /* Before returning data to userspace, encrypt decrypted data. */
464 static 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);
500 out:
501         return ret;
502 }
503 
504 static 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);
520 out:
521         return ret;
522 }
523 
524 /* verify HMAC before decrypting encrypted key */
525 static 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         }
558 out:
559         return ret;
560 }
561 
562 static 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);
593 out:
594         return ret;
595 }
596 
597 /* Allocate memory for decrypted key and datablob. */
598 static 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 = strict_strtol(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 
651 static 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);
701 out:
702         up_read(&mkey->sem);
703         key_put(mkey);
704         return ret;
705 }
706 
707 static 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  */
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)
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  */
776 static int encrypted_instantiate(struct key *key, const void *data,
777                                  size_t datalen)
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         int ret;
786 
787         if (datalen <= 0 || datalen > 32767 || !data)
788                 return -EINVAL;
789 
790         datablob = kmalloc(datalen + 1, GFP_KERNEL);
791         if (!datablob)
792                 return -ENOMEM;
793         datablob[datalen] = 0;
794         memcpy(datablob, data, datalen);
795         ret = datablob_parse(datablob, &format, &master_desc,
796                              &decrypted_datalen, &hex_encoded_iv);
797         if (ret < 0)
798                 goto out;
799 
800         epayload = encrypted_key_alloc(key, format, master_desc,
801                                        decrypted_datalen);
802         if (IS_ERR(epayload)) {
803                 ret = PTR_ERR(epayload);
804                 goto out;
805         }
806         ret = encrypted_init(epayload, key->description, format, master_desc,
807                              decrypted_datalen, hex_encoded_iv);
808         if (ret < 0) {
809                 kfree(epayload);
810                 goto out;
811         }
812 
813         rcu_assign_keypointer(key, epayload);
814 out:
815         kfree(datablob);
816         return ret;
817 }
818 
819 static void encrypted_rcu_free(struct rcu_head *rcu)
820 {
821         struct encrypted_key_payload *epayload;
822 
823         epayload = container_of(rcu, struct encrypted_key_payload, rcu);
824         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
825         kfree(epayload);
826 }
827 
828 /*
829  * encrypted_update - update the master key description
830  *
831  * Change the master key description for an existing encrypted key.
832  * The next read will return an encrypted datablob using the new
833  * master key description.
834  *
835  * On success, return 0. Otherwise return errno.
836  */
837 static int encrypted_update(struct key *key, const void *data, size_t datalen)
838 {
839         struct encrypted_key_payload *epayload = key->payload.data;
840         struct encrypted_key_payload *new_epayload;
841         char *buf;
842         char *new_master_desc = NULL;
843         const char *format = NULL;
844         int ret = 0;
845 
846         if (datalen <= 0 || datalen > 32767 || !data)
847                 return -EINVAL;
848 
849         buf = kmalloc(datalen + 1, GFP_KERNEL);
850         if (!buf)
851                 return -ENOMEM;
852 
853         buf[datalen] = 0;
854         memcpy(buf, data, datalen);
855         ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
856         if (ret < 0)
857                 goto out;
858 
859         ret = valid_master_desc(new_master_desc, epayload->master_desc);
860         if (ret < 0)
861                 goto out;
862 
863         new_epayload = encrypted_key_alloc(key, epayload->format,
864                                            new_master_desc, epayload->datalen);
865         if (IS_ERR(new_epayload)) {
866                 ret = PTR_ERR(new_epayload);
867                 goto out;
868         }
869 
870         __ekey_init(new_epayload, epayload->format, new_master_desc,
871                     epayload->datalen);
872 
873         memcpy(new_epayload->iv, epayload->iv, ivsize);
874         memcpy(new_epayload->payload_data, epayload->payload_data,
875                epayload->payload_datalen);
876 
877         rcu_assign_keypointer(key, new_epayload);
878         call_rcu(&epayload->rcu, encrypted_rcu_free);
879 out:
880         kfree(buf);
881         return ret;
882 }
883 
884 /*
885  * encrypted_read - format and copy the encrypted data to userspace
886  *
887  * The resulting datablob format is:
888  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
889  *
890  * On success, return to userspace the encrypted key datablob size.
891  */
892 static long encrypted_read(const struct key *key, char __user *buffer,
893                            size_t buflen)
894 {
895         struct encrypted_key_payload *epayload;
896         struct key *mkey;
897         u8 *master_key;
898         size_t master_keylen;
899         char derived_key[HASH_SIZE];
900         char *ascii_buf;
901         size_t asciiblob_len;
902         int ret;
903 
904         epayload = rcu_dereference_key(key);
905 
906         /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
907         asciiblob_len = epayload->datablob_len + ivsize + 1
908             + roundup(epayload->decrypted_datalen, blksize)
909             + (HASH_SIZE * 2);
910 
911         if (!buffer || buflen < asciiblob_len)
912                 return asciiblob_len;
913 
914         mkey = request_master_key(epayload, &master_key, &master_keylen);
915         if (IS_ERR(mkey))
916                 return PTR_ERR(mkey);
917 
918         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
919         if (ret < 0)
920                 goto out;
921 
922         ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
923         if (ret < 0)
924                 goto out;
925 
926         ret = datablob_hmac_append(epayload, master_key, master_keylen);
927         if (ret < 0)
928                 goto out;
929 
930         ascii_buf = datablob_format(epayload, asciiblob_len);
931         if (!ascii_buf) {
932                 ret = -ENOMEM;
933                 goto out;
934         }
935 
936         up_read(&mkey->sem);
937         key_put(mkey);
938 
939         if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
940                 ret = -EFAULT;
941         kfree(ascii_buf);
942 
943         return asciiblob_len;
944 out:
945         up_read(&mkey->sem);
946         key_put(mkey);
947         return ret;
948 }
949 
950 /*
951  * encrypted_destroy - before freeing the key, clear the decrypted data
952  *
953  * Before freeing the key, clear the memory containing the decrypted
954  * key data.
955  */
956 static void encrypted_destroy(struct key *key)
957 {
958         struct encrypted_key_payload *epayload = key->payload.data;
959 
960         if (!epayload)
961                 return;
962 
963         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
964         kfree(key->payload.data);
965 }
966 
967 struct key_type key_type_encrypted = {
968         .name = "encrypted",
969         .instantiate = encrypted_instantiate,
970         .update = encrypted_update,
971         .match = user_match,
972         .destroy = encrypted_destroy,
973         .describe = user_describe,
974         .read = encrypted_read,
975 };
976 EXPORT_SYMBOL_GPL(key_type_encrypted);
977 
978 static void encrypted_shash_release(void)
979 {
980         if (hashalg)
981                 crypto_free_shash(hashalg);
982         if (hmacalg)
983                 crypto_free_shash(hmacalg);
984 }
985 
986 static int __init encrypted_shash_alloc(void)
987 {
988         int ret;
989 
990         hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
991         if (IS_ERR(hmacalg)) {
992                 pr_info("encrypted_key: could not allocate crypto %s\n",
993                         hmac_alg);
994                 return PTR_ERR(hmacalg);
995         }
996 
997         hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
998         if (IS_ERR(hashalg)) {
999                 pr_info("encrypted_key: could not allocate crypto %s\n",
1000                         hash_alg);
1001                 ret = PTR_ERR(hashalg);
1002                 goto hashalg_fail;
1003         }
1004 
1005         return 0;
1006 
1007 hashalg_fail:
1008         crypto_free_shash(hmacalg);
1009         return ret;
1010 }
1011 
1012 static int __init init_encrypted(void)
1013 {
1014         int ret;
1015 
1016         ret = encrypted_shash_alloc();
1017         if (ret < 0)
1018                 return ret;
1019         ret = aes_get_sizes();
1020         if (ret < 0)
1021                 goto out;
1022         ret = register_key_type(&key_type_encrypted);
1023         if (ret < 0)
1024                 goto out;
1025         return 0;
1026 out:
1027         encrypted_shash_release();
1028         return ret;
1029 
1030 }
1031 
1032 static void __exit cleanup_encrypted(void)
1033 {
1034         encrypted_shash_release();
1035         unregister_key_type(&key_type_encrypted);
1036 }
1037 
1038 late_initcall(init_encrypted);
1039 module_exit(cleanup_encrypted);
1040 
1041 MODULE_LICENSE("GPL");
1042 

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