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         int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
  70         char *workbuf;
  71
  72         if (iname->len <= 0 || iname->len > ctx->lim)
  73                 return -EIO;
  74
  75         ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
  76                 EXT4_CRYPTO_BLOCK_SIZE : iname->len;
  77         ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
  78         ciphertext_len = (ciphertext_len > ctx->lim)
  79                         ? ctx->lim : ciphertext_len;
  80
  81         /* Allocate request */
  82         req = ablkcipher_request_alloc(tfm, GFP_NOFS);
  83         if (!req) {
  84                 printk_ratelimited(
  85                     KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
  86                 return -ENOMEM;
  87         }
  88         ablkcipher_request_set_callback(req,
  89                 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
  90                 ext4_dir_crypt_complete, &ecr);
  91
  92         /* Map the workpage */
  93         workbuf = kmap(ctx->workpage);
  94
  95         /* Copy the input */
  96         memcpy(workbuf, iname->name, iname->len);
  97         if (iname->len < ciphertext_len)
  98                 memset(workbuf + iname->len, 0, ciphertext_len - iname->len);
  99
 100         /* Initialize IV */
 101         memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
 102
 103         /* Create encryption request */
 104         sg_init_table(sg, 1);
 105         sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
 106         ablkcipher_request_set_crypt(req, sg, sg, ciphertext_len, iv);
 107         res = crypto_ablkcipher_encrypt(req);
 108         if (res == -EINPROGRESS || res == -EBUSY) {
 109                 BUG_ON(req->base.data != &ecr);
 110                 wait_for_completion(&ecr.completion);
 111                 res = ecr.res;
 112         }
 113         if (res >= 0) {
 114                 /* Copy the result to output */
 115                 memcpy(oname->name, workbuf, ciphertext_len);
 116                 res = ciphertext_len;
 117         }
 118         kunmap(ctx->workpage);
 119         ablkcipher_request_free(req);
 120         if (res < 0) {
 121                 printk_ratelimited(
 122                     KERN_ERR "%s: Error (error code %d)\n", __func__, res);
 123         }
 124         oname->len = ciphertext_len;
 125         return res;
 126 }
 127
 128 /*
 129  * ext4_fname_decrypt()
 130  *      This function decrypts the input filename, and returns
 131  *      the length of the plaintext.
 132  *      Errors are returned as negative numbers.
 133  *      We trust the caller to allocate sufficient memory to oname string.
 134  */
 135 static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
 136                               const struct ext4_str *iname,
 137                               struct ext4_str *oname)
 138 {
 139         struct ext4_str tmp_in[2], tmp_out[1];
 140         struct ablkcipher_request *req = NULL;
 141         DECLARE_EXT4_COMPLETION_RESULT(ecr);
 142         struct scatterlist sg[1];
 143         struct crypto_ablkcipher *tfm = ctx->ctfm;
 144         int res = 0;
 145         char iv[EXT4_CRYPTO_BLOCK_SIZE];
 146         char *workbuf;
 147
 148         if (iname->len <= 0 || iname->len > ctx->lim)
 149                 return -EIO;
 150
 151         tmp_in[0].name = iname->name;
 152         tmp_in[0].len = iname->len;
 153         tmp_out[0].name = oname->name;
 154
 155         /* Allocate request */
 156         req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 157         if (!req) {
 158                 printk_ratelimited(
 159                     KERN_ERR "%s: crypto_request_alloc() failed\n",  __func__);
 160                 return -ENOMEM;
 161         }
 162         ablkcipher_request_set_callback(req,
 163                 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 164                 ext4_dir_crypt_complete, &ecr);
 165
 166         /* Map the workpage */
 167         workbuf = kmap(ctx->workpage);
 168
 169         /* Copy the input */
 170         memcpy(workbuf, iname->name, iname->len);
 171
 172         /* Initialize IV */
 173         memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);
 174
 175         /* Create encryption request */
 176         sg_init_table(sg, 1);
 177         sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
 178         ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
 179         res = crypto_ablkcipher_decrypt(req);
 180         if (res == -EINPROGRESS || res == -EBUSY) {
 181                 BUG_ON(req->base.data != &ecr);
 182                 wait_for_completion(&ecr.completion);
 183                 res = ecr.res;
 184         }
 185         if (res >= 0) {
 186                 /* Copy the result to output */
 187                 memcpy(oname->name, workbuf, iname->len);
 188                 res = iname->len;
 189         }
 190         kunmap(ctx->workpage);
 191         ablkcipher_request_free(req);
 192         if (res < 0) {
 193                 printk_ratelimited(
 194                     KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
 195                     __func__, res);
 196                 return res;
 197         }
 198
 199         oname->len = strnlen(oname->name, iname->len);
 200         return oname->len;
 201 }
 202
 203 static const char *lookup_table =
 204         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
 205
 206 /**
 207  * ext4_fname_encode_digest() -
 208  *
 209  * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
 210  * The encoded string is roughly 4/3 times the size of the input string.
 211  */
 212 static int digest_encode(const char *src, int len, char *dst)
 213 {
 214         int i = 0, bits = 0, ac = 0;
 215         char *cp = dst;
 216
 217         while (i < len) {
 218                 ac += (((unsigned char) src[i]) << bits);
 219                 bits += 8;
 220                 do {
 221                         *cp++ = lookup_table[ac & 0x3f];
 222                         ac >>= 6;
 223                         bits -= 6;
 224                 } while (bits >= 6);
 225                 i++;
 226         }
 227         if (bits)
 228                 *cp++ = lookup_table[ac & 0x3f];
 229         return cp - dst;
 230 }
 231
 232 static int digest_decode(const char *src, int len, char *dst)
 233 {
 234         int i = 0, bits = 0, ac = 0;
 235         const char *p;
 236         char *cp = dst;
 237
 238         while (i < len) {
 239                 p = strchr(lookup_table, src[i]);
 240                 if (p == NULL || src[i] == 0)
 241                         return -2;
 242                 ac += (p - lookup_table) << bits;
 243                 bits += 6;
 244                 if (bits >= 8) {
 245                         *cp++ = ac & 0xff;
 246                         ac >>= 8;
 247                         bits -= 8;
 248                 }
 249                 i++;
 250         }
 251         if (ac)
 252                 return -1;
 253         return cp - dst;
 254 }
 255
 256 /**
 257  * ext4_free_fname_crypto_ctx() -
 258  *
 259  * Frees up a crypto context.
 260  */
 261 void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
 262 {
 263         if (ctx == NULL || IS_ERR(ctx))
 264                 return;
 265
 266         if (ctx->ctfm && !IS_ERR(ctx->ctfm))
 267                 crypto_free_ablkcipher(ctx->ctfm);
 268         if (ctx->htfm && !IS_ERR(ctx->htfm))
 269                 crypto_free_hash(ctx->htfm);
 270         if (ctx->workpage && !IS_ERR(ctx->workpage))
 271                 __free_page(ctx->workpage);
 272         kfree(ctx);
 273 }
 274
 275 /**
 276  * ext4_put_fname_crypto_ctx() -
 277  *
 278  * Return: The crypto context onto free list. If the free list is above a
 279  * threshold, completely frees up the context, and returns the memory.
 280  *
 281  * TODO: Currently we directly free the crypto context. Eventually we should
 282  * add code it to return to free list. Such an approach will increase
 283  * efficiency of directory lookup.
 284  */
 285 void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
 286 {
 287         if (*ctx == NULL || IS_ERR(*ctx))
 288                 return;
 289         ext4_free_fname_crypto_ctx(*ctx);
 290         *ctx = NULL;
 291 }
 292
 293 /**
 294  * ext4_search_fname_crypto_ctx() -
 295  */
 296 static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
 297                 const struct ext4_encryption_key *key)
 298 {
 299         return NULL;
 300 }
 301
 302 /**
 303  * ext4_alloc_fname_crypto_ctx() -
 304  */
 305 struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
 306         const struct ext4_encryption_key *key)
 307 {
 308         struct ext4_fname_crypto_ctx *ctx;
 309
 310         ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
 311         if (ctx == NULL)
 312                 return ERR_PTR(-ENOMEM);
 313         if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
 314                 /* This will automatically set key mode to invalid
 315                  * As enum for ENCRYPTION_MODE_INVALID is zero */
 316                 memset(&ctx->key, 0, sizeof(ctx->key));
 317         } else {
 318                 memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
 319         }
 320         ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
 321                 ? 0 : 1;
 322         ctx->ctfm_key_is_ready = 0;
 323         ctx->ctfm = NULL;
 324         ctx->htfm = NULL;
 325         ctx->workpage = NULL;
 326         return ctx;
 327 }
 328
 329 /**
 330  * ext4_get_fname_crypto_ctx() -
 331  *
 332  * Allocates a free crypto context and initializes it to hold
 333  * the crypto material for the inode.
 334  *
 335  * Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
 336  */
 337 struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
 338         struct inode *inode, u32 max_ciphertext_len)
 339 {
 340         struct ext4_fname_crypto_ctx *ctx;
 341         struct ext4_inode_info *ei = EXT4_I(inode);
 342         int res;
 343
 344         /* Check if the crypto policy is set on the inode */
 345         res = ext4_encrypted_inode(inode);
 346         if (res == 0)
 347                 return NULL;
 348
 349         if (!ext4_has_encryption_key(inode))
 350                 ext4_generate_encryption_key(inode);
 351
 352         /* Get a crypto context based on the key.
 353          * A new context is allocated if no context matches the requested key.
 354          */
 355         ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
 356         if (ctx == NULL)
 357                 ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
 358         if (IS_ERR(ctx))
 359                 return ctx;
 360
 361         ctx->flags = ei->i_crypt_policy_flags;
 362         if (ctx->has_valid_key) {
 363                 if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
 364                         printk_once(KERN_WARNING
 365                                     "ext4: unsupported key mode %d\n",
 366                                     ctx->key.mode);
 367                         return ERR_PTR(-ENOKEY);
 368                 }
 369
 370                 /* As a first cut, we will allocate new tfm in every call.
 371                  * later, we will keep the tfm around, in case the key gets
 372                  * re-used */
 373                 if (ctx->ctfm == NULL) {
 374                         ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
 375                                         0, 0);
 376                 }
 377                 if (IS_ERR(ctx->ctfm)) {
 378                         res = PTR_ERR(ctx->ctfm);
 379                         printk(
 380                             KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
 381                             __func__, res);
 382                         ctx->ctfm = NULL;
 383                         ext4_put_fname_crypto_ctx(&ctx);
 384                         return ERR_PTR(res);
 385                 }
 386                 if (ctx->ctfm == NULL) {
 387                         printk(
 388                             KERN_DEBUG "%s: could not allocate crypto tfm\n",
 389                             __func__);
 390                         ext4_put_fname_crypto_ctx(&ctx);
 391                         return ERR_PTR(-ENOMEM);
 392                 }
 393                 if (ctx->workpage == NULL)
 394                         ctx->workpage = alloc_page(GFP_NOFS);
 395                 if (IS_ERR(ctx->workpage)) {
 396                         res = PTR_ERR(ctx->workpage);
 397                         printk(
 398                             KERN_DEBUG "%s: error (%d) allocating work page\n",
 399                             __func__, res);
 400                         ctx->workpage = NULL;
 401                         ext4_put_fname_crypto_ctx(&ctx);
 402                         return ERR_PTR(res);
 403                 }
 404                 if (ctx->workpage == NULL) {
 405                         printk(
 406                             KERN_DEBUG "%s: could not allocate work page\n",
 407                             __func__);
 408                         ext4_put_fname_crypto_ctx(&ctx);
 409                         return ERR_PTR(-ENOMEM);
 410                 }
 411                 ctx->lim = max_ciphertext_len;
 412                 crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
 413                 crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
 414                         CRYPTO_TFM_REQ_WEAK_KEY);
 415
 416                 /* If we are lucky, we will get a context that is already
 417                  * set up with the right key. Else, we will have to
 418                  * set the key */
 419                 if (!ctx->ctfm_key_is_ready) {
 420                         /* Since our crypto objectives for filename encryption
 421                          * are pretty weak,
 422                          * we directly use the inode master key */
 423                         res = crypto_ablkcipher_setkey(ctx->ctfm,
 424                                         ctx->key.raw, ctx->key.size);
 425                         if (res) {
 426                                 ext4_put_fname_crypto_ctx(&ctx);
 427                                 return ERR_PTR(-EIO);
 428                         }
 429                         ctx->ctfm_key_is_ready = 1;
 430                 } else {
 431                         /* In the current implementation, key should never be
 432                          * marked "ready" for a context that has just been
 433                          * allocated. So we should never reach here */
 434                          BUG();
 435                 }
 436         }
 437         if (ctx->htfm == NULL)
 438                 ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
 439         if (IS_ERR(ctx->htfm)) {
 440                 res = PTR_ERR(ctx->htfm);
 441                 printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
 442                         __func__, res);
 443                 ctx->htfm = NULL;
 444                 ext4_put_fname_crypto_ctx(&ctx);
 445                 return ERR_PTR(res);
 446         }
 447         if (ctx->htfm == NULL) {
 448                 printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
 449                                 __func__);
 450                 ext4_put_fname_crypto_ctx(&ctx);
 451                 return ERR_PTR(-ENOMEM);
 452         }
 453
 454         return ctx;
 455 }
 456
 457 /**
 458  * ext4_fname_crypto_round_up() -
 459  *
 460  * Return: The next multiple of block size
 461  */
 462 u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
 463 {
 464         return ((size+blksize-1)/blksize)*blksize;
 465 }
 466
 467 /**
 468  * ext4_fname_crypto_namelen_on_disk() -
 469  */
 470 int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
 471                                       u32 namelen)
 472 {
 473         u32 ciphertext_len;
 474         int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
 475
 476         if (ctx == NULL)
 477                 return -EIO;
 478         if (!(ctx->has_valid_key))
 479                 return -EACCES;
 480         ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
 481                 EXT4_CRYPTO_BLOCK_SIZE : namelen;
 482         ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
 483         ciphertext_len = (ciphertext_len > ctx->lim)
 484                         ? ctx->lim : ciphertext_len;
 485         return (int) ciphertext_len;
 486 }
 487
 488 /**
 489  * ext4_fname_crypto_alloc_obuff() -
 490  *
 491  * Allocates an output buffer that is sufficient for the crypto operation
 492  * specified by the context and the direction.
 493  */
 494 int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
 495                                    u32 ilen, struct ext4_str *crypto_str)
 496 {
 497         unsigned int olen;
 498         int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
 499
 500         if (!ctx)
 501                 return -EIO;
 502         if (padding < EXT4_CRYPTO_BLOCK_SIZE)
 503                 padding = EXT4_CRYPTO_BLOCK_SIZE;
 504         olen = ext4_fname_crypto_round_up(ilen, padding);
 505         crypto_str->len = olen;
 506         if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
 507                 olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
 508         /* Allocated buffer can hold one more character to null-terminate the
 509          * string */
 510         crypto_str->name = kmalloc(olen+1, GFP_NOFS);
 511         if (!(crypto_str->name))
 512                 return -ENOMEM;
 513         return 0;
 514 }
 515
 516 /**
 517  * ext4_fname_crypto_free_buffer() -
 518  *
 519  * Frees the buffer allocated for crypto operation.
 520  */
 521 void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
 522 {
 523         if (!crypto_str)
 524                 return;
 525         kfree(crypto_str->name);
 526         crypto_str->name = NULL;
 527 }
 528
 529 /**
 530  * ext4_fname_disk_to_usr() - converts a filename from disk space to user space
 531  */
 532 int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
 533                             struct dx_hash_info *hinfo,
 534                             const struct ext4_str *iname,
 535                             struct ext4_str *oname)
 536 {
 537         char buf[24];
 538         int ret;
 539
 540         if (ctx == NULL)
 541                 return -EIO;
 542         if (iname->len < 3) {
 543                 /*Check for . and .. */
 544                 if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
 545                         oname->name[0] = '.';
 546                         oname->name[iname->len-1] = '.';
 547                         oname->len = iname->len;
 548                         return oname->len;
 549                 }
 550         }
 551         if (ctx->has_valid_key)
 552                 return ext4_fname_decrypt(ctx, iname, oname);
 553
 554         if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
 555                 ret = digest_encode(iname->name, iname->len, oname->name);
 556                 oname->len = ret;
 557                 return ret;
 558         }
 559         if (hinfo) {
 560                 memcpy(buf, &hinfo->hash, 4);
 561                 memcpy(buf+4, &hinfo->minor_hash, 4);
 562         } else
 563                 memset(buf, 0, 8);
 564         memcpy(buf + 8, iname->name + iname->len - 16, 16);
 565         oname->name[0] = '_';
 566         ret = digest_encode(buf, 24, oname->name+1);
 567         oname->len = ret + 1;
 568         return ret + 1;
 569 }
 570
 571 int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
 572                            struct dx_hash_info *hinfo,
 573                            const struct ext4_dir_entry_2 *de,
 574                            struct ext4_str *oname)
 575 {
 576         struct ext4_str iname = {.name = (unsigned char *) de->name,
 577                                  .len = de->name_len };
 578
 579         return _ext4_fname_disk_to_usr(ctx, hinfo, &iname, oname);
 580 }
 581
 582
 583 /**
 584  * ext4_fname_usr_to_disk() - converts a filename from user space to disk space
 585  */
 586 int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
 587                            const struct qstr *iname,
 588                            struct ext4_str *oname)
 589 {
 590         int res;
 591
 592         if (ctx == NULL)
 593                 return -EIO;
 594         if (iname->len < 3) {
 595                 /*Check for . and .. */
 596                 if (iname->name[0] == '.' &&
 597                                 iname->name[iname->len-1] == '.') {
 598                         oname->name[0] = '.';
 599                         oname->name[iname->len-1] = '.';
 600                         oname->len = iname->len;
 601                         return oname->len;
 602                 }
 603         }
 604         if (ctx->has_valid_key) {
 605                 res = ext4_fname_encrypt(ctx, iname, oname);
 606                 return res;
 607         }
 608         /* Without a proper key, a user is not allowed to modify the filenames
 609          * in a directory. Consequently, a user space name cannot be mapped to
 610          * a disk-space name */
 611         return -EACCES;
 612 }
 613
 614 /*
 615  * Calculate the htree hash from a filename from user space
 616  */
 617 int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
 618                             const struct qstr *iname,
 619                             struct dx_hash_info *hinfo)
 620 {
 621         struct ext4_str tmp;
 622         int ret = 0;
 623         char buf[EXT4_FNAME_CRYPTO_DIGEST_SIZE+1];
 624
 625         if (!ctx ||
 626             ((iname->name[0] == '.') &&
 627              ((iname->len == 1) ||
 628               ((iname->name[1] == '.') && (iname->len == 2))))) {
 629                 ext4fs_dirhash(iname->name, iname->len, hinfo);
 630                 return 0;
 631         }
 632
 633         if (!ctx->has_valid_key && iname->name[0] == '_') {
 634                 if (iname->len != 33)
 635                         return -ENOENT;
 636                 ret = digest_decode(iname->name+1, iname->len, buf);
 637                 if (ret != 24)
 638                         return -ENOENT;
 639                 memcpy(&hinfo->hash, buf, 4);
 640                 memcpy(&hinfo->minor_hash, buf + 4, 4);
 641                 return 0;
 642         }
 643
 644         if (!ctx->has_valid_key && iname->name[0] != '_') {
 645                 if (iname->len > 43)
 646                         return -ENOENT;
 647                 ret = digest_decode(iname->name, iname->len, buf);
 648                 ext4fs_dirhash(buf, ret, hinfo);
 649                 return 0;
 650         }
 651
 652         /* First encrypt the plaintext name */
 653         ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
 654         if (ret < 0)
 655                 return ret;
 656
 657         ret = ext4_fname_encrypt(ctx, iname, &tmp);
 658         if (ret >= 0) {
 659                 ext4fs_dirhash(tmp.name, tmp.len, hinfo);
 660                 ret = 0;
 661         }
 662
 663         ext4_fname_crypto_free_buffer(&tmp);
 664         return ret;
 665 }
 666
 667 int ext4_fname_match(struct ext4_fname_crypto_ctx *ctx, struct ext4_str *cstr,
 668                      int len, const char * const name,
 669                      struct ext4_dir_entry_2 *de)
 670 {
 671         int ret = -ENOENT;
 672         int bigname = (*name == '_');
 673
 674         if (ctx->has_valid_key) {
 675                 if (cstr->name == NULL) {
 676                         struct qstr istr;
 677
 678                         ret = ext4_fname_crypto_alloc_buffer(ctx, len, cstr);
 679                         if (ret < 0)
 680                                 goto errout;
 681                         istr.name = name;
 682                         istr.len = len;
 683                         ret = ext4_fname_encrypt(ctx, &istr, cstr);
 684                         if (ret < 0)
 685                                 goto errout;
 686                 }
 687         } else {
 688                 if (cstr->name == NULL) {
 689                         cstr->name = kmalloc(32, GFP_KERNEL);
 690                         if (cstr->name == NULL)
 691                                 return -ENOMEM;
 692                         if ((bigname && (len != 33)) ||
 693                             (!bigname && (len > 43)))
 694                                 goto errout;
 695                         ret = digest_decode(name+bigname, len-bigname,
 696                                             cstr->name);
 697                         if (ret < 0) {
 698                                 ret = -ENOENT;
 699                                 goto errout;
 700                         }
 701                         cstr->len = ret;
 702                 }
 703                 if (bigname) {
 704                         if (de->name_len < 16)
 705                                 return 0;
 706                         ret = memcmp(de->name + de->name_len - 16,
 707                                      cstr->name + 8, 16);
 708                         return (ret == 0) ? 1 : 0;
 709                 }
 710         }
 711         if (de->name_len != cstr->len)
 712                 return 0;
 713         ret = memcmp(de->name, cstr->name, cstr->len);
 714         return (ret == 0) ? 1 : 0;
 715 errout:
 716         kfree(cstr->name);
 717         cstr->name = NULL;
 718         return ret;
 719 }