root/fs/crypto/crypto.c

DEFINITIONS

1. fscrypt_enqueue_decrypt_work
2. fscrypt_release_ctx
3. fscrypt_get_ctx
4. fscrypt_alloc_bounce_page
5. fscrypt_free_bounce_page
6. fscrypt_generate_iv
7. fscrypt_crypt_block
8. fscrypt_encrypt_pagecache_blocks
9. fscrypt_encrypt_block_inplace
10. fscrypt_decrypt_pagecache_blocks
11. fscrypt_decrypt_block_inplace
12. fscrypt_d_revalidate
13. fscrypt_destroy
14. fscrypt_initialize
15. fscrypt_msg
16. fscrypt_init

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * This contains encryption functions for per-file encryption.
   4  *
   5  * Copyright (C) 2015, Google, Inc.
   6  * Copyright (C) 2015, Motorola Mobility
   7  *
   8  * Written by Michael Halcrow, 2014.
   9  *
  10  * Filename encryption additions
  11  *      Uday Savagaonkar, 2014
  12  * Encryption policy handling additions
  13  *      Ildar Muslukhov, 2014
  14  * Add fscrypt_pullback_bio_page()
  15  *      Jaegeuk Kim, 2015.
  16  *
  17  * This has not yet undergone a rigorous security audit.
  18  *
  19  * The usage of AES-XTS should conform to recommendations in NIST
  20  * Special Publication 800-38E and IEEE P1619/D16.
  21  */
  22 
  23 #include <linux/pagemap.h>
  24 #include <linux/mempool.h>
  25 #include <linux/module.h>
  26 #include <linux/scatterlist.h>
  27 #include <linux/ratelimit.h>
  28 #include <linux/dcache.h>
  29 #include <linux/namei.h>
  30 #include <crypto/aes.h>
  31 #include <crypto/skcipher.h>
  32 #include "fscrypt_private.h"
  33 
  34 static unsigned int num_prealloc_crypto_pages = 32;
  35 static unsigned int num_prealloc_crypto_ctxs = 128;
  36 
  37 module_param(num_prealloc_crypto_pages, uint, 0444);
  38 MODULE_PARM_DESC(num_prealloc_crypto_pages,
  39                 "Number of crypto pages to preallocate");
  40 module_param(num_prealloc_crypto_ctxs, uint, 0444);
  41 MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
  42                 "Number of crypto contexts to preallocate");
  43 
  44 static mempool_t *fscrypt_bounce_page_pool = NULL;
  45 
  46 static LIST_HEAD(fscrypt_free_ctxs);
  47 static DEFINE_SPINLOCK(fscrypt_ctx_lock);
  48 
  49 static struct workqueue_struct *fscrypt_read_workqueue;
  50 static DEFINE_MUTEX(fscrypt_init_mutex);
  51 
  52 static struct kmem_cache *fscrypt_ctx_cachep;
  53 struct kmem_cache *fscrypt_info_cachep;
  54 
  55 void fscrypt_enqueue_decrypt_work(struct work_struct *work)
  56 {
  57         queue_work(fscrypt_read_workqueue, work);
  58 }
  59 EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
  60 
  61 /**
  62  * fscrypt_release_ctx() - Release a decryption context
  63  * @ctx: The decryption context to release.
  64  *
  65  * If the decryption context was allocated from the pre-allocated pool, return
  66  * it to that pool.  Else, free it.
  67  */
  68 void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
  69 {
  70         unsigned long flags;
  71 
  72         if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
  73                 kmem_cache_free(fscrypt_ctx_cachep, ctx);
  74         } else {
  75                 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
  76                 list_add(&ctx->free_list, &fscrypt_free_ctxs);
  77                 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
  78         }
  79 }
  80 EXPORT_SYMBOL(fscrypt_release_ctx);
  81 
  82 /**
  83  * fscrypt_get_ctx() - Get a decryption context
  84  * @gfp_flags:   The gfp flag for memory allocation
  85  *
  86  * Allocate and initialize a decryption context.
  87  *
  88  * Return: A new decryption context on success; an ERR_PTR() otherwise.
  89  */
  90 struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
  91 {
  92         struct fscrypt_ctx *ctx;
  93         unsigned long flags;
  94 
  95         /*
  96          * First try getting a ctx from the free list so that we don't have to
  97          * call into the slab allocator.
  98          */
  99         spin_lock_irqsave(&fscrypt_ctx_lock, flags);
 100         ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
 101                                         struct fscrypt_ctx, free_list);
 102         if (ctx)
 103                 list_del(&ctx->free_list);
 104         spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
 105         if (!ctx) {
 106                 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
 107                 if (!ctx)
 108                         return ERR_PTR(-ENOMEM);
 109                 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 110         } else {
 111                 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 112         }
 113         return ctx;
 114 }
 115 EXPORT_SYMBOL(fscrypt_get_ctx);
 116 
 117 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
 118 {
 119         return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
 120 }
 121 
 122 /**
 123  * fscrypt_free_bounce_page() - free a ciphertext bounce page
 124  *
 125  * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
 126  * or by fscrypt_alloc_bounce_page() directly.
 127  */
 128 void fscrypt_free_bounce_page(struct page *bounce_page)
 129 {
 130         if (!bounce_page)
 131                 return;
 132         set_page_private(bounce_page, (unsigned long)NULL);
 133         ClearPagePrivate(bounce_page);
 134         mempool_free(bounce_page, fscrypt_bounce_page_pool);
 135 }
 136 EXPORT_SYMBOL(fscrypt_free_bounce_page);
 137 
 138 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
 139                          const struct fscrypt_info *ci)
 140 {
 141         memset(iv, 0, ci->ci_mode->ivsize);
 142         iv->lblk_num = cpu_to_le64(lblk_num);
 143 
 144         if (fscrypt_is_direct_key_policy(&ci->ci_policy))
 145                 memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
 146 
 147         if (ci->ci_essiv_tfm != NULL)
 148                 crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
 149 }
 150 
 151 /* Encrypt or decrypt a single filesystem block of file contents */
 152 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
 153                         u64 lblk_num, struct page *src_page,
 154                         struct page *dest_page, unsigned int len,
 155                         unsigned int offs, gfp_t gfp_flags)
 156 {
 157         union fscrypt_iv iv;
 158         struct skcipher_request *req = NULL;
 159         DECLARE_CRYPTO_WAIT(wait);
 160         struct scatterlist dst, src;
 161         struct fscrypt_info *ci = inode->i_crypt_info;
 162         struct crypto_skcipher *tfm = ci->ci_ctfm;
 163         int res = 0;
 164 
 165         if (WARN_ON_ONCE(len <= 0))
 166                 return -EINVAL;
 167         if (WARN_ON_ONCE(len % FS_CRYPTO_BLOCK_SIZE != 0))
 168                 return -EINVAL;
 169 
 170         fscrypt_generate_iv(&iv, lblk_num, ci);
 171 
 172         req = skcipher_request_alloc(tfm, gfp_flags);
 173         if (!req)
 174                 return -ENOMEM;
 175 
 176         skcipher_request_set_callback(
 177                 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 178                 crypto_req_done, &wait);
 179 
 180         sg_init_table(&dst, 1);
 181         sg_set_page(&dst, dest_page, len, offs);
 182         sg_init_table(&src, 1);
 183         sg_set_page(&src, src_page, len, offs);
 184         skcipher_request_set_crypt(req, &src, &dst, len, &iv);
 185         if (rw == FS_DECRYPT)
 186                 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
 187         else
 188                 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
 189         skcipher_request_free(req);
 190         if (res) {
 191                 fscrypt_err(inode, "%scryption failed for block %llu: %d",
 192                             (rw == FS_DECRYPT ? "De" : "En"), lblk_num, res);
 193                 return res;
 194         }
 195         return 0;
 196 }
 197 
 198 /**
 199  * fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a pagecache page
 200  * @page:      The locked pagecache page containing the block(s) to encrypt
 201  * @len:       Total size of the block(s) to encrypt.  Must be a nonzero
 202  *              multiple of the filesystem's block size.
 203  * @offs:      Byte offset within @page of the first block to encrypt.  Must be
 204  *              a multiple of the filesystem's block size.
 205  * @gfp_flags: Memory allocation flags
 206  *
 207  * A new bounce page is allocated, and the specified block(s) are encrypted into
 208  * it.  In the bounce page, the ciphertext block(s) will be located at the same
 209  * offsets at which the plaintext block(s) were located in the source page; any
 210  * other parts of the bounce page will be left uninitialized.  However, normally
 211  * blocksize == PAGE_SIZE and the whole page is encrypted at once.
 212  *
 213  * This is for use by the filesystem's ->writepages() method.
 214  *
 215  * Return: the new encrypted bounce page on success; an ERR_PTR() on failure
 216  */
 217 struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
 218                                               unsigned int len,
 219                                               unsigned int offs,
 220                                               gfp_t gfp_flags)
 221 
 222 {
 223         const struct inode *inode = page->mapping->host;
 224         const unsigned int blockbits = inode->i_blkbits;
 225         const unsigned int blocksize = 1 << blockbits;
 226         struct page *ciphertext_page;
 227         u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
 228                        (offs >> blockbits);
 229         unsigned int i;
 230         int err;
 231 
 232         if (WARN_ON_ONCE(!PageLocked(page)))
 233                 return ERR_PTR(-EINVAL);
 234 
 235         if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
 236                 return ERR_PTR(-EINVAL);
 237 
 238         ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
 239         if (!ciphertext_page)
 240                 return ERR_PTR(-ENOMEM);
 241 
 242         for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
 243                 err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
 244                                           page, ciphertext_page,
 245                                           blocksize, i, gfp_flags);
 246                 if (err) {
 247                         fscrypt_free_bounce_page(ciphertext_page);
 248                         return ERR_PTR(err);
 249                 }
 250         }
 251         SetPagePrivate(ciphertext_page);
 252         set_page_private(ciphertext_page, (unsigned long)page);
 253         return ciphertext_page;
 254 }
 255 EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);
 256 
 257 /**
 258  * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
 259  * @inode:     The inode to which this block belongs
 260  * @page:      The page containing the block to encrypt
 261  * @len:       Size of block to encrypt.  Doesn't need to be a multiple of the
 262  *              fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
 263  * @offs:      Byte offset within @page at which the block to encrypt begins
 264  * @lblk_num:  Filesystem logical block number of the block, i.e. the 0-based
 265  *              number of the block within the file
 266  * @gfp_flags: Memory allocation flags
 267  *
 268  * Encrypt a possibly-compressed filesystem block that is located in an
 269  * arbitrary page, not necessarily in the original pagecache page.  The @inode
 270  * and @lblk_num must be specified, as they can't be determined from @page.
 271  *
 272  * Return: 0 on success; -errno on failure
 273  */
 274 int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
 275                                   unsigned int len, unsigned int offs,
 276                                   u64 lblk_num, gfp_t gfp_flags)
 277 {
 278         return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
 279                                    len, offs, gfp_flags);
 280 }
 281 EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
 282 
 283 /**
 284  * fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a pagecache page
 285  * @page:      The locked pagecache page containing the block(s) to decrypt
 286  * @len:       Total size of the block(s) to decrypt.  Must be a nonzero
 287  *              multiple of the filesystem's block size.
 288  * @offs:      Byte offset within @page of the first block to decrypt.  Must be
 289  *              a multiple of the filesystem's block size.
 290  *
 291  * The specified block(s) are decrypted in-place within the pagecache page,
 292  * which must still be locked and not uptodate.  Normally, blocksize ==
 293  * PAGE_SIZE and the whole page is decrypted at once.
 294  *
 295  * This is for use by the filesystem's ->readpages() method.
 296  *
 297  * Return: 0 on success; -errno on failure
 298  */
 299 int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
 300                                      unsigned int offs)
 301 {
 302         const struct inode *inode = page->mapping->host;
 303         const unsigned int blockbits = inode->i_blkbits;
 304         const unsigned int blocksize = 1 << blockbits;
 305         u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
 306                        (offs >> blockbits);
 307         unsigned int i;
 308         int err;
 309 
 310         if (WARN_ON_ONCE(!PageLocked(page)))
 311                 return -EINVAL;
 312 
 313         if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
 314                 return -EINVAL;
 315 
 316         for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
 317                 err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
 318                                           page, blocksize, i, GFP_NOFS);
 319                 if (err)
 320                         return err;
 321         }
 322         return 0;
 323 }
 324 EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);
 325 
 326 /**
 327  * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
 328  * @inode:     The inode to which this block belongs
 329  * @page:      The page containing the block to decrypt
 330  * @len:       Size of block to decrypt.  Doesn't need to be a multiple of the
 331  *              fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
 332  * @offs:      Byte offset within @page at which the block to decrypt begins
 333  * @lblk_num:  Filesystem logical block number of the block, i.e. the 0-based
 334  *              number of the block within the file
 335  *
 336  * Decrypt a possibly-compressed filesystem block that is located in an
 337  * arbitrary page, not necessarily in the original pagecache page.  The @inode
 338  * and @lblk_num must be specified, as they can't be determined from @page.
 339  *
 340  * Return: 0 on success; -errno on failure
 341  */
 342 int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
 343                                   unsigned int len, unsigned int offs,
 344                                   u64 lblk_num)
 345 {
 346         return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
 347                                    len, offs, GFP_NOFS);
 348 }
 349 EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
 350 
 351 /*
 352  * Validate dentries in encrypted directories to make sure we aren't potentially
 353  * caching stale dentries after a key has been added.
 354  */
 355 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
 356 {
 357         struct dentry *dir;
 358         int err;
 359         int valid;
 360 
 361         /*
 362          * Plaintext names are always valid, since fscrypt doesn't support
 363          * reverting to ciphertext names without evicting the directory's inode
 364          * -- which implies eviction of the dentries in the directory.
 365          */
 366         if (!(dentry->d_flags & DCACHE_ENCRYPTED_NAME))
 367                 return 1;
 368 
 369         /*
 370          * Ciphertext name; valid if the directory's key is still unavailable.
 371          *
 372          * Although fscrypt forbids rename() on ciphertext names, we still must
 373          * use dget_parent() here rather than use ->d_parent directly.  That's
 374          * because a corrupted fs image may contain directory hard links, which
 375          * the VFS handles by moving the directory's dentry tree in the dcache
 376          * each time ->lookup() finds the directory and it already has a dentry
 377          * elsewhere.  Thus ->d_parent can be changing, and we must safely grab
 378          * a reference to some ->d_parent to prevent it from being freed.
 379          */
 380 
 381         if (flags & LOOKUP_RCU)
 382                 return -ECHILD;
 383 
 384         dir = dget_parent(dentry);
 385         err = fscrypt_get_encryption_info(d_inode(dir));
 386         valid = !fscrypt_has_encryption_key(d_inode(dir));
 387         dput(dir);
 388 
 389         if (err < 0)
 390                 return err;
 391 
 392         return valid;
 393 }
 394 
 395 const struct dentry_operations fscrypt_d_ops = {
 396         .d_revalidate = fscrypt_d_revalidate,
 397 };
 398 
 399 static void fscrypt_destroy(void)
 400 {
 401         struct fscrypt_ctx *pos, *n;
 402 
 403         list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
 404                 kmem_cache_free(fscrypt_ctx_cachep, pos);
 405         INIT_LIST_HEAD(&fscrypt_free_ctxs);
 406         mempool_destroy(fscrypt_bounce_page_pool);
 407         fscrypt_bounce_page_pool = NULL;
 408 }
 409 
 410 /**
 411  * fscrypt_initialize() - allocate major buffers for fs encryption.
 412  * @cop_flags:  fscrypt operations flags
 413  *
 414  * We only call this when we start accessing encrypted files, since it
 415  * results in memory getting allocated that wouldn't otherwise be used.
 416  *
 417  * Return: Zero on success, non-zero otherwise.
 418  */
 419 int fscrypt_initialize(unsigned int cop_flags)
 420 {
 421         int i, res = -ENOMEM;
 422 
 423         /* No need to allocate a bounce page pool if this FS won't use it. */
 424         if (cop_flags & FS_CFLG_OWN_PAGES)
 425                 return 0;
 426 
 427         mutex_lock(&fscrypt_init_mutex);
 428         if (fscrypt_bounce_page_pool)
 429                 goto already_initialized;
 430 
 431         for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
 432                 struct fscrypt_ctx *ctx;
 433 
 434                 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
 435                 if (!ctx)
 436                         goto fail;
 437                 list_add(&ctx->free_list, &fscrypt_free_ctxs);
 438         }
 439 
 440         fscrypt_bounce_page_pool =
 441                 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
 442         if (!fscrypt_bounce_page_pool)
 443                 goto fail;
 444 
 445 already_initialized:
 446         mutex_unlock(&fscrypt_init_mutex);
 447         return 0;
 448 fail:
 449         fscrypt_destroy();
 450         mutex_unlock(&fscrypt_init_mutex);
 451         return res;
 452 }
 453 
 454 void fscrypt_msg(const struct inode *inode, const char *level,
 455                  const char *fmt, ...)
 456 {
 457         static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
 458                                       DEFAULT_RATELIMIT_BURST);
 459         struct va_format vaf;
 460         va_list args;
 461 
 462         if (!__ratelimit(&rs))
 463                 return;
 464 
 465         va_start(args, fmt);
 466         vaf.fmt = fmt;
 467         vaf.va = &args;
 468         if (inode)
 469                 printk("%sfscrypt (%s, inode %lu): %pV\n",
 470                        level, inode->i_sb->s_id, inode->i_ino, &vaf);
 471         else
 472                 printk("%sfscrypt: %pV\n", level, &vaf);
 473         va_end(args);
 474 }
 475 
 476 /**
 477  * fscrypt_init() - Set up for fs encryption.
 478  */
 479 static int __init fscrypt_init(void)
 480 {
 481         int err = -ENOMEM;
 482 
 483         /*
 484          * Use an unbound workqueue to allow bios to be decrypted in parallel
 485          * even when they happen to complete on the same CPU.  This sacrifices
 486          * locality, but it's worthwhile since decryption is CPU-intensive.
 487          *
 488          * Also use a high-priority workqueue to prioritize decryption work,
 489          * which blocks reads from completing, over regular application tasks.
 490          */
 491         fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
 492                                                  WQ_UNBOUND | WQ_HIGHPRI,
 493                                                  num_online_cpus());
 494         if (!fscrypt_read_workqueue)
 495                 goto fail;
 496 
 497         fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
 498         if (!fscrypt_ctx_cachep)
 499                 goto fail_free_queue;
 500 
 501         fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
 502         if (!fscrypt_info_cachep)
 503                 goto fail_free_ctx;
 504 
 505         err = fscrypt_init_keyring();
 506         if (err)
 507                 goto fail_free_info;
 508 
 509         return 0;
 510 
 511 fail_free_info:
 512         kmem_cache_destroy(fscrypt_info_cachep);
 513 fail_free_ctx:
 514         kmem_cache_destroy(fscrypt_ctx_cachep);
 515 fail_free_queue:
 516         destroy_workqueue(fscrypt_read_workqueue);
 517 fail:
 518         return err;
 519 }
 520 late_initcall(fscrypt_init)