fs/ext4/crypto_fname.c

   1 /*
   2  * linux/fs/ext4/crypto_fname.c
   3  *
   4  * Copyright (C) 2015, Google, Inc.
   5  *
   6  * This contains functions for filename crypto management in ext4
   7  *
   8  * Written by Uday Savagaonkar, 2014.
   9  *
  10  * This has not yet undergone a rigorous security audit.
  11  *
  12  */
  13
  14 #include <crypto/hash.h>
  15 #include <crypto/sha.h>
  16 #include <keys/encrypted-type.h>
  17 #include <keys/user-type.h>
  18 #include <linux/crypto.h>
  19 #include <linux/gfp.h>
  20 #include <linux/kernel.h>
  21 #include <linux/key.h>
  22 #include <linux/key.h>
  23 #include <linux/list.h>
  24 #include <linux/mempool.h>
  25 #include <linux/random.h>
  26 #include <linux/scatterlist.h>
  27 #include <linux/spinlock_types.h>
  28
  29 #include "ext4.h"
  30 #include "ext4_crypto.h"
  31 #include "xattr.h"
  32
  33 /**
  34  * ext4_dir_crypt_complete() -
  35  */
  36 static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
  37 {
  38         struct ext4_completion_result *ecr = req->data;
  39
  40         if (res == -EINPROGRESS)
  41                 return;
  42         ecr->res = res;
  43         complete(&ecr->completion);
  44 }
  45
  46 bool ext4_valid_filenames_enc_mode(uint32_t mode)
  47 {
  48         return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
  49 }
  50
  51 /**
  52  * ext4_fname_encrypt() -
  53  *
  54  * This function encrypts the input filename, and returns the length of the
  55  * ciphertext. Errors are returned as negative numbers.  We trust the caller to
  56  * allocate sufficient memory to oname string.
  57  */
  58 static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx,
  59                               const struct qstr *iname,
  60                               struct ext4_str *oname)
  61 {
  62         u32 ciphertext_len;
  63         struct ablkcipher_request *req = NULL;
  64         DECLARE_EXT4_COMPLETION_RESULT(ecr);
  65         struct crypto_ablkcipher *tfm = ctx->ctfm;
  66         int res = 0;
  67         char iv[EXT4_CRYPTO_BLOCK_SIZE];
  68         struct scatterlist sg[1];
  69         char *workbuf;
  70
  71         if (iname->len <= 0 || iname->len > ctx->lim)
  72                 return -EIO;
  73
  74         ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
  75                 EXT4_CRYPTO_BLOCK_SIZE : iname->len;
  76         ciphertext_len = (ciphertext_len > ctx->lim)
  77                         ? ctx->lim : ciphertext_len;
  78
  79         /* Allocate request */
  80         req = ablkcipher_request_alloc(tfm, GFP_NOFS);
  81         if (!req) {
  82                 printk_ratelimited(
  83                     KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
  84                 return -ENOMEM;
  85         }
  86         ablkcipher_request_set_callback(req,
  87                 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
  88                 ext4_dir_crypt_complete, &ecr);
  89
  90         /* Map the workpage */
  91         workbuf = kmap(ctx->workpage);
  92
  93         /* Copy the input */
  94         memcpy(workbuf, iname->name, iname->len);
  95         if (iname->len < ciphertext_len)
  96                 memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
  97
  98         /* Initialize IV */
  99         memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
 100
 101         /* Create encryption request */
 102         sg_init_table(sg, 1);
 103         sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
 104         ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
 105         res = crypto_ablkcipher_encrypt(req);
 106         if (res == -EINPROGRESS || res == -EBUSY) {
 107                 BUG_ON(req->base.data != &ecr);
 108                 wait_for_completion(&ecr.completion);
 109                 res = ecr.res;
 110         }
 111         if (res >= 0) {
 112                 /* Copy the result to output */
 113                 memcpy(oname->name, workbuf, ciphertext_len);
 114                 res = ciphertext_len;
 115         }
 116         kunmap(ctx->workpage);
 117         ablkcipher_request_free(req);
 118         if (res < 0) {
 119                 printk_ratelimited(
 120                     KERN_ERR "%s: Error (error code %d)\n", __func__, res);
 121         }
 122         oname->len = ciphertext_len;
 123         return res;
 124 }
 125
 126 /*
 127  * ext4_fname_decrypt()
 128  *      This function decrypts the input filename, and returns
 129  *      the length of the plaintext.
 130  *      Errors are returned as negative numbers.
 131  *      We trust the caller to allocate sufficient memory to oname string.
 132  */
 133 static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
 134                               const struct ext4_str *iname,
 135                               struct ext4_str *oname)
 136 {
 137         struct ext4_str tmp_in[2], tmp_out[1];
 138         struct ablkcipher_request *req = NULL;
 139         DECLARE_EXT4_COMPLETION_RESULT(ecr);
 140         struct scatterlist sg[1];
 141         struct crypto_ablkcipher *tfm = ctx->ctfm;
 142         int res = 0;
 143         char iv[EXT4_CRYPTO_BLOCK_SIZE];
 144         char *workbuf;
 145
 146         if (iname->len <= 0 || iname->len > ctx->lim)
 147                 return -EIO;
 148
 149         tmp_in[0].name = iname->name;
 150         tmp_in[0].len = iname->len;
 151         tmp_out[0].name = oname->name;
 152
 153         /* Allocate request */
 154         req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 155         if (!req) {
 156                 printk_ratelimited(
 157                     KERN_ERR "%s: crypto_request_alloc() failed\n",  __func__);
 158                 return -ENOMEM;
 159         }
 160         ablkcipher_request_set_callback(req,
 161                 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 162                 ext4_dir_crypt_complete, &ecr);
 163
 164         /* Map the workpage */
 165         workbuf = kmap(ctx->workpage);
 166
 167         /* Copy the input */
 168         memcpy(workbuf, iname->name, iname->len);
 169
 170         /* Initialize IV */
 171         memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
 172
 173         /* Create encryption request */
 174         sg_init_table(sg, 1);
 175         sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
 176         ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
 177         res = crypto_ablkcipher_decrypt(req);
 178         if (res == -EINPROGRESS || res == -EBUSY) {
 179                 BUG_ON(req->base.data != &ecr);
 180                 wait_for_completion(&ecr.completion);
 181                 res = ecr.res;
 182         }
 183         if (res >= 0) {
 184                 /* Copy the result to output */
 185                 memcpy(oname->name, workbuf, iname->len);
 186                 res = iname->len;
 187         }
 188         kunmap(ctx->workpage);
 189         ablkcipher_request_free(req);
 190         if (res < 0) {
 191                 printk_ratelimited(
 192                     KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
 193                     __func__, res);
 194                 return res;
 195         }
 196
 197         oname->len = strnlen(oname->name, iname->len);
 198         return oname->len;
 199 }
 200
 201 static const char *lookup_table =
 202         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
 203
 204 /**
 205  * ext4_fname_encode_digest() -
 206  *
 207  * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
 208  * The encoded string is roughly 4/3 times the size of the input string.
 209  */
 210 static int digest_encode(const char *src, int len, char *dst)
 211 {
 212         int i = 0, bits = 0, ac = 0;
 213         char *cp = dst;
 214
 215         while (i < len) {
 216                 ac += (((unsigned char) src[i]) << bits);
 217                 bits += 8;
 218                 do {
 219                         *cp++ = lookup_table[ac & 0x3f];
 220                         ac >>= 6;
 221                         bits -= 6;
 222                 } while (bits >= 6);
 223                 i++;
 224         }
 225         if (bits)
 226                 *cp++ = lookup_table[ac & 0x3f];
 227         return cp - dst;
 228 }
 229
 230 static int digest_decode(const char *src, int len, char *dst)
 231 {
 232         int i = 0, bits = 0, ac = 0;
 233         const char *p;
 234         char *cp = dst;
 235
 236         while (i < len) {
 237                 p = strchr(lookup_table, src[i]);
 238                 if (p == NULL || src[i] == 0)
 239                         return -2;
 240                 ac += (p - lookup_table) << bits;
 241                 bits += 6;
 242                 if (bits >= 8) {
 243                         *cp++ = ac & 0xff;
 244                         ac >>= 8;
 245                         bits -= 8;
 246                 }
 247                 i++;
 248         }
 249         if (ac)
 250                 return -1;
 251         return cp - dst;
 252 }
 253
 254 /**
 255  * ext4_free_fname_crypto_ctx() -
 256  *
 257  * Frees up a crypto context.
 258  */
 259 void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
 260 {
 261         if (ctx == NULL || IS_ERR(ctx))
 262                 return;
 263
 264         if (ctx->ctfm && !IS_ERR(ctx->ctfm))
 265                 crypto_free_ablkcipher(ctx->ctfm);
 266         if (ctx->htfm && !IS_ERR(ctx->htfm))
 267                 crypto_free_hash(ctx->htfm);
 268         if (ctx->workpage && !IS_ERR(ctx->workpage))
 269                 __free_page(ctx->workpage);
 270         kfree(ctx);
 271 }
 272
 273 /**
 274  * ext4_put_fname_crypto_ctx() -
 275  *
 276  * Return: The crypto context onto free list. If the free list is above a
 277  * threshold, completely frees up the context, and returns the memory.
 278  *
 279  * TODO: Currently we directly free the crypto context. Eventually we should
 280  * add code it to return to free list. Such an approach will increase
 281  * efficiency of directory lookup.
 282  */
 283 void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
 284 {
 285         if (*ctx == NULL || IS_ERR(*ctx))
 286                 return;
 287         ext4_free_fname_crypto_ctx(*ctx);
 288         *ctx = NULL;
 289 }
 290
 291 /**
 292  * ext4_search_fname_crypto_ctx() -
 293  */
 294 static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
 295                 const struct ext4_encryption_key *key)
 296 {
 297         return NULL;
 298 }
 299
 300 /**
 301  * ext4_alloc_fname_crypto_ctx() -
 302  */
 303 struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
 304         const struct ext4_encryption_key *key)
 305 {
 306         struct ext4_fname_crypto_ctx *ctx;
 307
 308         ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
 309         if (ctx == NULL)
 310                 return ERR_PTR(-ENOMEM);
 311         if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
 312                 /* This will automatically set key mode to invalid
 313                  * As enum for ENCRYPTION_MODE_INVALID is zero */
 314                 memset(&ctx->key, 0, sizeof(ctx->key));
 315         } else {
 316                 memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
 317         }
 318         ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
 319                 ? 0 : 1;
 320         ctx->ctfm_key_is_ready = 0;
 321         ctx->ctfm = NULL;
 322         ctx->htfm = NULL;
 323         ctx->workpage = NULL;
 324         return ctx;
 325 }
 326
 327 /**
 328  * ext4_get_fname_crypto_ctx() -
 329  *
 330  * Allocates a free crypto context and initializes it to hold
 331  * the crypto material for the inode.
 332  *
 333  * Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
 334  */
 335 struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
 336         struct inode *inode, u32 max_ciphertext_len)
 337 {
 338         struct ext4_fname_crypto_ctx *ctx;
 339         struct ext4_inode_info *ei = EXT4_I(inode);
 340         int res;
 341
 342         /* Check if the crypto policy is set on the inode */
 343         res = ext4_encrypted_inode(inode);
 344         if (res == 0)
 345                 return NULL;
 346
 347         if (!ext4_has_encryption_key(inode))
 348                 ext4_generate_encryption_key(inode);
 349
 350         /* Get a crypto context based on the key.
 351          * A new context is allocated if no context matches the requested key.
 352          */
 353         ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
 354         if (ctx == NULL)
 355                 ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
 356         if (IS_ERR(ctx))
 357                 return ctx;
 358
 359         if (ctx->has_valid_key) {
 360                 if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
 361                         printk_once(KERN_WARNING
 362                                     "ext4: unsupported key mode %d\n",
 363                                     ctx->key.mode);
 364                         return ERR_PTR(-ENOKEY);
 365                 }
 366
 367                 /* As a first cut, we will allocate new tfm in every call.
 368                  * later, we will keep the tfm around, in case the key gets
 369                  * re-used */
 370                 if (ctx->ctfm == NULL) {
 371                         ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
 372                                         0, 0);
 373                 }
 374                 if (IS_ERR(ctx->ctfm)) {
 375                         res = PTR_ERR(ctx->ctfm);
 376                         printk(
 377                             KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
 378                             __func__, res);
 379                         ctx->ctfm = NULL;
 380                         ext4_put_fname_crypto_ctx(&ctx);
 381                         return ERR_PTR(res);
 382                 }
 383                 if (ctx->ctfm == NULL) {
 384                         printk(
 385                             KERN_DEBUG "%s: could not allocate crypto tfm\n",
 386                             __func__);
 387                         ext4_put_fname_crypto_ctx(&ctx);
 388                         return ERR_PTR(-ENOMEM);
 389                 }
 390                 if (ctx->workpage == NULL)
 391                         ctx->workpage = alloc_page(GFP_NOFS);
 392                 if (IS_ERR(ctx->workpage)) {
 393                         res = PTR_ERR(ctx->workpage);
 394                         printk(
 395                             KERN_DEBUG "%s: error (%d) allocating work page\n",
 396                             __func__, res);
 397                         ctx->workpage = NULL;
 398                         ext4_put_fname_crypto_ctx(&ctx);
 399                         return ERR_PTR(res);
 400                 }
 401                 if (ctx->workpage == NULL) {
 402                         printk(
 403                             KERN_DEBUG "%s: could not allocate work page\n",
 404                             __func__);
 405                         ext4_put_fname_crypto_ctx(&ctx);
 406                         return ERR_PTR(-ENOMEM);
 407                 }
 408                 ctx->lim = max_ciphertext_len;
 409                 crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
 410                 crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
 411                         CRYPTO_TFM_REQ_WEAK_KEY);
 412
 413                 /* If we are lucky, we will get a context that is already
 414                  * set up with the right key. Else, we will have to
 415                  * set the key */
 416                 if (!ctx->ctfm_key_is_ready) {
 417                         /* Since our crypto objectives for filename encryption
 418                          * are pretty weak,
 419                          * we directly use the inode master key */
 420                         res = crypto_ablkcipher_setkey(ctx->ctfm,
 421                                         ctx->key.raw, ctx->key.size);
 422                         if (res) {
 423                                 ext4_put_fname_crypto_ctx(&ctx);
 424                                 return ERR_PTR(-EIO);
 425                         }
 426                         ctx->ctfm_key_is_ready = 1;
 427                 } else {
 428                         /* In the current implementation, key should never be
 429                          * marked "ready" for a context that has just been
 430                          * allocated. So we should never reach here */
 431                          BUG();
 432                 }
 433         }
 434         if (ctx->htfm == NULL)
 435                 ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
 436         if (IS_ERR(ctx->htfm)) {
 437                 res = PTR_ERR(ctx->htfm);
 438                 printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
 439                         __func__, res);
 440                 ctx->htfm = NULL;
 441                 ext4_put_fname_crypto_ctx(&ctx);
 442                 return ERR_PTR(res);
 443         }
 444         if (ctx->htfm == NULL) {
 445                 printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
 446                                 __func__);
 447                 ext4_put_fname_crypto_ctx(&ctx);
 448                 return ERR_PTR(-ENOMEM);
 449         }
 450
 451         return ctx;
 452 }
 453
 454 /**
 455  * ext4_fname_crypto_round_up() -
 456  *
 457  * Return: The next multiple of block size
 458  */
 459 u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
 460 {
 461         return ((size+blksize-1)/blksize)*blksize;
 462 }
 463
 464 /**
 465  * ext4_fname_crypto_namelen_on_disk() -
 466  */
 467 int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
 468                                       u32 namelen)
 469 {
 470         u32 ciphertext_len;
 471
 472         if (ctx == NULL)
 473                 return -EIO;
 474         if (!(ctx->has_valid_key))
 475                 return -EACCES;
 476         ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
 477                 EXT4_CRYPTO_BLOCK_SIZE : namelen;
 478         ciphertext_len = (ciphertext_len > ctx->lim)
 479                         ? ctx->lim : ciphertext_len;
 480         return (int) ciphertext_len;
 481 }
 482
 483 /**
 484  * ext4_fname_crypto_alloc_obuff() -
 485  *
 486  * Allocates an output buffer that is sufficient for the crypto operation
 487  * specified by the context and the direction.
 488  */
 489 int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
 490                                    u32 ilen, struct ext4_str *crypto_str)
 491 {
 492         unsigned int olen;
 493
 494         if (!ctx)
 495                 return -EIO;
 496         olen = ext4_fname_crypto_round_up(ilen, EXT4_CRYPTO_BLOCK_SIZE);
 497         crypto_str->len = olen;
 498         if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
 499                 olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
 500         /* Allocated buffer can hold one more character to null-terminate the
 501          * string */
 502         crypto_str->name = kmalloc(olen+1, GFP_NOFS);
 503         if (!(crypto_str->name))
 504                 return -ENOMEM;
 505         return 0;
 506 }
 507
 508 /**
 509  * ext4_fname_crypto_free_buffer() -
 510  *
 511  * Frees the buffer allocated for crypto operation.
 512  */
 513 void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
 514 {
 515         if (!crypto_str)
 516                 return;
 517         kfree(crypto_str->name);
 518         crypto_str->name = NULL;
 519 }
 520
 521 /**
 522  * ext4_fname_disk_to_usr() - converts a filename from disk space to user space
 523  */
 524 int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
 525                             struct dx_hash_info *hinfo,
 526                             const struct ext4_str *iname,
 527                             struct ext4_str *oname)
 528 {
 529         char buf[24];
 530         int ret;
 531
 532         if (ctx == NULL)
 533                 return -EIO;
 534         if (iname->len < 3) {
 535                 /*Check for . and .. */
 536                 if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
 537                         oname->name[0] = '.';
 538                         oname->name[iname->len-1] = '.';
 539                         oname->len = iname->len;
 540                         return oname->len;
 541                 }
 542         }
 543         if (ctx->has_valid_key)
 544                 return ext4_fname_decrypt(ctx, iname, oname);
 545
 546         if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
 547                 ret = digest_encode(iname->name, iname->len, oname->name);
 548                 oname->len = ret;
 549                 return ret;
 550         }
 551         if (hinfo) {
 552                 memcpy(buf, &hinfo->hash, 4);
 553                 memcpy(buf+4, &hinfo->minor_hash, 4);
 554         } else
 555                 memset(buf, 0, 8);
 556         memcpy(buf + 8, iname->name + iname->len - 16, 16);
 557         oname->name[0] = '_';
 558         ret = digest_encode(buf, 24, oname->name+1);
 559         oname->len = ret + 1;
 560         return ret + 1;
 561 }
 562
 563 int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
 564                            struct dx_hash_info *hinfo,
 565                            const struct ext4_dir_entry_2 *de,
 566                            struct ext4_str *oname)
 567 {
 568         struct ext4_str iname = {.name = (unsigned char *) de->name,
 569                                  .len = de->name_len };
 570
 571         return _ext4_fname_disk_to_usr(ctx, hinfo, &iname, oname);
 572 }
 573
 574
 575 /**
 576  * ext4_fname_usr_to_disk() - converts a filename from user space to disk space
 577  */
 578 int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
 579                            const struct qstr *iname,
 580                            struct ext4_str *oname)
 581 {
 582         int res;
 583
 584         if (ctx == NULL)
 585                 return -EIO;
 586         if (iname->len < 3) {
 587                 /*Check for . and .. */
 588                 if (iname->name[0] == '.' &&
 589                                 iname->name[iname->len-1] == '.') {
 590                         oname->name[0] = '.';
 591                         oname->name[iname->len-1] = '.';
 592                         oname->len = iname->len;
 593                         return oname->len;
 594                 }
 595         }
 596         if (ctx->has_valid_key) {
 597                 res = ext4_fname_encrypt(ctx, iname, oname);
 598                 return res;
 599         }
 600         /* Without a proper key, a user is not allowed to modify the filenames
 601          * in a directory. Consequently, a user space name cannot be mapped to
 602          * a disk-space name */
 603         return -EACCES;
 604 }
 605
 606 /*
 607  * Calculate the htree hash from a filename from user space
 608  */
 609 int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
 610                             const struct qstr *iname,
 611                             struct dx_hash_info *hinfo)
 612 {
 613         struct ext4_str tmp;
 614         int ret = 0;
 615         char buf[EXT4_FNAME_CRYPTO_DIGEST_SIZE+1];
 616
 617         if (!ctx ||
 618             ((iname->name[0] == '.') &&
 619              ((iname->len == 1) ||
 620               ((iname->name[1] == '.') && (iname->len == 2))))) {
 621                 ext4fs_dirhash(iname->name, iname->len, hinfo);
 622                 return 0;
 623         }
 624
 625         if (!ctx->has_valid_key && iname->name[0] == '_') {
 626                 if (iname->len != 33)
 627                         return -ENOENT;
 628                 ret = digest_decode(iname->name+1, iname->len, buf);
 629                 if (ret != 24)
 630                         return -ENOENT;
 631                 memcpy(&hinfo->hash, buf, 4);
 632                 memcpy(&hinfo->minor_hash, buf + 4, 4);
 633                 return 0;
 634         }
 635
 636         if (!ctx->has_valid_key && iname->name[0] != '_') {
 637                 if (iname->len > 43)
 638                         return -ENOENT;
 639                 ret = digest_decode(iname->name, iname->len, buf);
 640                 ext4fs_dirhash(buf, ret, hinfo);
 641                 return 0;
 642         }
 643
 644         /* First encrypt the plaintext name */
 645         ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
 646         if (ret < 0)
 647                 return ret;
 648
 649         ret = ext4_fname_encrypt(ctx, iname, &tmp);
 650         if (ret >= 0) {
 651                 ext4fs_dirhash(tmp.name, tmp.len, hinfo);
 652                 ret = 0;
 653         }
 654
 655         ext4_fname_crypto_free_buffer(&tmp);
 656         return ret;
 657 }
 658
 659 int ext4_fname_match(struct ext4_fname_crypto_ctx *ctx, struct ext4_str *cstr,
 660                      int len, const char * const name,
 661                      struct ext4_dir_entry_2 *de)
 662 {
 663         int ret = -ENOENT;
 664         int bigname = (*name == '_');
 665
 666         if (ctx->has_valid_key) {
 667                 if (cstr->name == NULL) {
 668                         struct qstr istr;
 669
 670                         ret = ext4_fname_crypto_alloc_buffer(ctx, len, cstr);
 671                         if (ret < 0)
 672                                 goto errout;
 673                         istr.name = name;
 674                         istr.len = len;
 675                         ret = ext4_fname_encrypt(ctx, &istr, cstr);
 676                         if (ret < 0)
 677                                 goto errout;
 678                 }
 679         } else {
 680                 if (cstr->name == NULL) {
 681                         cstr->name = kmalloc(32, GFP_KERNEL);
 682                         if (cstr->name == NULL)
 683                                 return -ENOMEM;
 684                         if ((bigname && (len != 33)) ||
 685                             (!bigname && (len > 43)))
 686                                 goto errout;
 687                         ret = digest_decode(name+bigname, len-bigname,
 688                                             cstr->name);
 689                         if (ret < 0) {
 690                                 ret = -ENOENT;
 691                                 goto errout;
 692                         }
 693                         cstr->len = ret;
 694                 }
 695                 if (bigname) {
 696                         if (de->name_len < 16)
 697                                 return 0;
 698                         ret = memcmp(de->name + de->name_len - 16,
 699                                      cstr->name + 8, 16);
 700                         return (ret == 0) ? 1 : 0;
 701                 }
 702         }
 703         if (de->name_len != cstr->len)
 704                 return 0;
 705         ret = memcmp(de->name, cstr->name, cstr->len);
 706         return (ret == 0) ? 1 : 0;
 707 errout:
 708         kfree(cstr->name);
 709         cstr->name = NULL;
 710         return ret;
 711 }