fs/f2fs/crypto.c

   1 /*
   2  * linux/fs/f2fs/crypto.c
   3  *
   4  * Copied from linux/fs/ext4/crypto.c
   5  *
   6  * Copyright (C) 2015, Google, Inc.
   7  * Copyright (C) 2015, Motorola Mobility
   8  *
   9  * This contains encryption functions for f2fs
  10  *
  11  * Written by Michael Halcrow, 2014.
  12  *
  13  * Filename encryption additions
  14  *      Uday Savagaonkar, 2014
  15  * Encryption policy handling additions
  16  *      Ildar Muslukhov, 2014
  17  * Remove ext4_encrypted_zeroout(),
  18  *   add f2fs_restore_and_release_control_page()
  19  *      Jaegeuk Kim, 2015.
  20  *
  21  * This has not yet undergone a rigorous security audit.
  22  *
  23  * The usage of AES-XTS should conform to recommendations in NIST
  24  * Special Publication 800-38E and IEEE P1619/D16.
  25  */
  26 #include <crypto/hash.h>
  27 #include <crypto/sha.h>
  28 #include <keys/user-type.h>
  29 #include <keys/encrypted-type.h>
  30 #include <linux/crypto.h>
  31 #include <linux/ecryptfs.h>
  32 #include <linux/gfp.h>
  33 #include <linux/kernel.h>
  34 #include <linux/key.h>
  35 #include <linux/list.h>
  36 #include <linux/mempool.h>
  37 #include <linux/module.h>
  38 #include <linux/mutex.h>
  39 #include <linux/random.h>
  40 #include <linux/scatterlist.h>
  41 #include <linux/spinlock_types.h>
  42 #include <linux/f2fs_fs.h>
  43 #include <linux/ratelimit.h>
  44 #include <linux/bio.h>
  45
  46 #include "f2fs.h"
  47 #include "xattr.h"
  48
  49 /* Encryption added and removed here! (L: */
  50
  51 static unsigned int num_prealloc_crypto_pages = 32;
  52 static unsigned int num_prealloc_crypto_ctxs = 128;
  53
  54 module_param(num_prealloc_crypto_pages, uint, 0444);
  55 MODULE_PARM_DESC(num_prealloc_crypto_pages,
  56                 "Number of crypto pages to preallocate");
  57 module_param(num_prealloc_crypto_ctxs, uint, 0444);
  58 MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
  59                 "Number of crypto contexts to preallocate");
  60
  61 static mempool_t *f2fs_bounce_page_pool;
  62
  63 static LIST_HEAD(f2fs_free_crypto_ctxs);
  64 static DEFINE_SPINLOCK(f2fs_crypto_ctx_lock);
  65
  66 static struct workqueue_struct *f2fs_read_workqueue;
  67 static DEFINE_MUTEX(crypto_init);
  68
  69 static struct kmem_cache *f2fs_crypto_ctx_cachep;
  70 struct kmem_cache *f2fs_crypt_info_cachep;
  71
  72 /**
  73  * f2fs_release_crypto_ctx() - Releases an encryption context
  74  * @ctx: The encryption context to release.
  75  *
  76  * If the encryption context was allocated from the pre-allocated pool, returns
  77  * it to that pool. Else, frees it.
  78  *
  79  * If there's a bounce page in the context, this frees that.
  80  */
  81 void f2fs_release_crypto_ctx(struct f2fs_crypto_ctx *ctx)
  82 {
  83         unsigned long flags;
  84
  85         if (ctx->flags & F2FS_WRITE_PATH_FL && ctx->w.bounce_page) {
  86                 mempool_free(ctx->w.bounce_page, f2fs_bounce_page_pool);
  87                 ctx->w.bounce_page = NULL;
  88         }
  89         ctx->w.control_page = NULL;
  90         if (ctx->flags & F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
  91                 kmem_cache_free(f2fs_crypto_ctx_cachep, ctx);
  92         } else {
  93                 spin_lock_irqsave(&f2fs_crypto_ctx_lock, flags);
  94                 list_add(&ctx->free_list, &f2fs_free_crypto_ctxs);
  95                 spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
  96         }
  97 }
  98
  99 /**
 100  * f2fs_get_crypto_ctx() - Gets an encryption context
 101  * @inode:       The inode for which we are doing the crypto
 102  *
 103  * Allocates and initializes an encryption context.
 104  *
 105  * Return: An allocated and initialized encryption context on success; error
 106  * value or NULL otherwise.
 107  */
 108 struct f2fs_crypto_ctx *f2fs_get_crypto_ctx(struct inode *inode)
 109 {
 110         struct f2fs_crypto_ctx *ctx = NULL;
 111         unsigned long flags;
 112         struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
 113
 114         if (ci == NULL)
 115                 return ERR_PTR(-ENOKEY);
 116
 117         /*
 118          * We first try getting the ctx from a free list because in
 119          * the common case the ctx will have an allocated and
 120          * initialized crypto tfm, so it's probably a worthwhile
 121          * optimization. For the bounce page, we first try getting it
 122          * from the kernel allocator because that's just about as fast
 123          * as getting it from a list and because a cache of free pages
 124          * should generally be a "last resort" option for a filesystem
 125          * to be able to do its job.
 126          */
 127         spin_lock_irqsave(&f2fs_crypto_ctx_lock, flags);
 128         ctx = list_first_entry_or_null(&f2fs_free_crypto_ctxs,
 129                                         struct f2fs_crypto_ctx, free_list);
 130         if (ctx)
 131                 list_del(&ctx->free_list);
 132         spin_unlock_irqrestore(&f2fs_crypto_ctx_lock, flags);
 133         if (!ctx) {
 134                 ctx = kmem_cache_zalloc(f2fs_crypto_ctx_cachep, GFP_NOFS);
 135                 if (!ctx)
 136                         return ERR_PTR(-ENOMEM);
 137                 ctx->flags |= F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 138         } else {
 139                 ctx->flags &= ~F2FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
 140         }
 141         ctx->flags &= ~F2FS_WRITE_PATH_FL;
 142         return ctx;
 143 }
 144
 145 /*
 146  * Call f2fs_decrypt on every single page, reusing the encryption
 147  * context.
 148  */
 149 static void completion_pages(struct work_struct *work)
 150 {
 151         struct f2fs_crypto_ctx *ctx =
 152                 container_of(work, struct f2fs_crypto_ctx, r.work);
 153         struct bio *bio = ctx->r.bio;
 154         struct bio_vec *bv;
 155         int i;
 156
 157         bio_for_each_segment_all(bv, bio, i) {
 158                 struct page *page = bv->bv_page;
 159                 int ret = f2fs_decrypt(ctx, page);
 160
 161                 if (ret) {
 162                         WARN_ON_ONCE(1);
 163                         SetPageError(page);
 164                 } else
 165                         SetPageUptodate(page);
 166                 unlock_page(page);
 167         }
 168         f2fs_release_crypto_ctx(ctx);
 169         bio_put(bio);
 170 }
 171
 172 void f2fs_end_io_crypto_work(struct f2fs_crypto_ctx *ctx, struct bio *bio)
 173 {
 174         INIT_WORK(&ctx->r.work, completion_pages);
 175         ctx->r.bio = bio;
 176         queue_work(f2fs_read_workqueue, &ctx->r.work);
 177 }
 178
 179 static void f2fs_crypto_destroy(void)
 180 {
 181         struct f2fs_crypto_ctx *pos, *n;
 182
 183         list_for_each_entry_safe(pos, n, &f2fs_free_crypto_ctxs, free_list)
 184                 kmem_cache_free(f2fs_crypto_ctx_cachep, pos);
 185         INIT_LIST_HEAD(&f2fs_free_crypto_ctxs);
 186         if (f2fs_bounce_page_pool)
 187                 mempool_destroy(f2fs_bounce_page_pool);
 188         f2fs_bounce_page_pool = NULL;
 189 }
 190
 191 /**
 192  * f2fs_crypto_initialize() - Set up for f2fs encryption.
 193  *
 194  * We only call this when we start accessing encrypted files, since it
 195  * results in memory getting allocated that wouldn't otherwise be used.
 196  *
 197  * Return: Zero on success, non-zero otherwise.
 198  */
 199 int f2fs_crypto_initialize(void)
 200 {
 201         int i, res = -ENOMEM;
 202
 203         if (f2fs_bounce_page_pool)
 204                 return 0;
 205
 206         mutex_lock(&crypto_init);
 207         if (f2fs_bounce_page_pool)
 208                 goto already_initialized;
 209
 210         for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
 211                 struct f2fs_crypto_ctx *ctx;
 212
 213                 ctx = kmem_cache_zalloc(f2fs_crypto_ctx_cachep, GFP_KERNEL);
 214                 if (!ctx)
 215                         goto fail;
 216                 list_add(&ctx->free_list, &f2fs_free_crypto_ctxs);
 217         }
 218
 219         /* must be allocated at the last step to avoid race condition above */
 220         f2fs_bounce_page_pool =
 221                 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
 222         if (!f2fs_bounce_page_pool)
 223                 goto fail;
 224
 225 already_initialized:
 226         mutex_unlock(&crypto_init);
 227         return 0;
 228 fail:
 229         f2fs_crypto_destroy();
 230         mutex_unlock(&crypto_init);
 231         return res;
 232 }
 233
 234 /**
 235  * f2fs_exit_crypto() - Shutdown the f2fs encryption system
 236  */
 237 void f2fs_exit_crypto(void)
 238 {
 239         f2fs_crypto_destroy();
 240
 241         if (f2fs_read_workqueue)
 242                 destroy_workqueue(f2fs_read_workqueue);
 243         if (f2fs_crypto_ctx_cachep)
 244                 kmem_cache_destroy(f2fs_crypto_ctx_cachep);
 245         if (f2fs_crypt_info_cachep)
 246                 kmem_cache_destroy(f2fs_crypt_info_cachep);
 247 }
 248
 249 int __init f2fs_init_crypto(void)
 250 {
 251         int res = -ENOMEM;
 252
 253         f2fs_read_workqueue = alloc_workqueue("f2fs_crypto", WQ_HIGHPRI, 0);
 254         if (!f2fs_read_workqueue)
 255                 goto fail;
 256
 257         f2fs_crypto_ctx_cachep = KMEM_CACHE(f2fs_crypto_ctx,
 258                                                 SLAB_RECLAIM_ACCOUNT);
 259         if (!f2fs_crypto_ctx_cachep)
 260                 goto fail;
 261
 262         f2fs_crypt_info_cachep = KMEM_CACHE(f2fs_crypt_info,
 263                                                 SLAB_RECLAIM_ACCOUNT);
 264         if (!f2fs_crypt_info_cachep)
 265                 goto fail;
 266
 267         return 0;
 268 fail:
 269         f2fs_exit_crypto();
 270         return res;
 271 }
 272
 273 void f2fs_restore_and_release_control_page(struct page **page)
 274 {
 275         struct f2fs_crypto_ctx *ctx;
 276         struct page *bounce_page;
 277
 278         /* The bounce data pages are unmapped. */
 279         if ((*page)->mapping)
 280                 return;
 281
 282         /* The bounce data page is unmapped. */
 283         bounce_page = *page;
 284         ctx = (struct f2fs_crypto_ctx *)page_private(bounce_page);
 285
 286         /* restore control page */
 287         *page = ctx->w.control_page;
 288
 289         f2fs_restore_control_page(bounce_page);
 290 }
 291
 292 void f2fs_restore_control_page(struct page *data_page)
 293 {
 294         struct f2fs_crypto_ctx *ctx =
 295                 (struct f2fs_crypto_ctx *)page_private(data_page);
 296
 297         set_page_private(data_page, (unsigned long)NULL);
 298         ClearPagePrivate(data_page);
 299         unlock_page(data_page);
 300         f2fs_release_crypto_ctx(ctx);
 301 }
 302
 303 /**
 304  * f2fs_crypt_complete() - The completion callback for page encryption
 305  * @req: The asynchronous encryption request context
 306  * @res: The result of the encryption operation
 307  */
 308 static void f2fs_crypt_complete(struct crypto_async_request *req, int res)
 309 {
 310         struct f2fs_completion_result *ecr = req->data;
 311
 312         if (res == -EINPROGRESS)
 313                 return;
 314         ecr->res = res;
 315         complete(&ecr->completion);
 316 }
 317
 318 typedef enum {
 319         F2FS_DECRYPT = 0,
 320         F2FS_ENCRYPT,
 321 } f2fs_direction_t;
 322
 323 static int f2fs_page_crypto(struct f2fs_crypto_ctx *ctx,
 324                                 struct inode *inode,
 325                                 f2fs_direction_t rw,
 326                                 pgoff_t index,
 327                                 struct page *src_page,
 328                                 struct page *dest_page)
 329 {
 330         u8 xts_tweak[F2FS_XTS_TWEAK_SIZE];
 331         struct ablkcipher_request *req = NULL;
 332         DECLARE_F2FS_COMPLETION_RESULT(ecr);
 333         struct scatterlist dst, src;
 334         struct f2fs_crypt_info *ci = F2FS_I(inode)->i_crypt_info;
 335         struct crypto_ablkcipher *tfm = ci->ci_ctfm;
 336         int res = 0;
 337
 338         req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 339         if (!req) {
 340                 printk_ratelimited(KERN_ERR
 341                                 "%s: crypto_request_alloc() failed\n",
 342                                 __func__);
 343                 return -ENOMEM;
 344         }
 345         ablkcipher_request_set_callback(
 346                 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 347                 f2fs_crypt_complete, &ecr);
 348
 349         BUILD_BUG_ON(F2FS_XTS_TWEAK_SIZE < sizeof(index));
 350         memcpy(xts_tweak, &index, sizeof(index));
 351         memset(&xts_tweak[sizeof(index)], 0,
 352                         F2FS_XTS_TWEAK_SIZE - sizeof(index));
 353
 354         sg_init_table(&dst, 1);
 355         sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0);
 356         sg_init_table(&src, 1);
 357         sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0);
 358         ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
 359                                         xts_tweak);
 360         if (rw == F2FS_DECRYPT)
 361                 res = crypto_ablkcipher_decrypt(req);
 362         else
 363                 res = crypto_ablkcipher_encrypt(req);
 364         if (res == -EINPROGRESS || res == -EBUSY) {
 365                 wait_for_completion(&ecr.completion);
 366                 res = ecr.res;
 367         }
 368         ablkcipher_request_free(req);
 369         if (res) {
 370                 printk_ratelimited(KERN_ERR
 371                         "%s: crypto_ablkcipher_encrypt() returned %d\n",
 372                         __func__, res);
 373                 return res;
 374         }
 375         return 0;
 376 }
 377
 378 static struct page *alloc_bounce_page(struct f2fs_crypto_ctx *ctx)
 379 {
 380         ctx->w.bounce_page = mempool_alloc(f2fs_bounce_page_pool, GFP_NOWAIT);
 381         if (ctx->w.bounce_page == NULL)
 382                 return ERR_PTR(-ENOMEM);
 383         ctx->flags |= F2FS_WRITE_PATH_FL;
 384         return ctx->w.bounce_page;
 385 }
 386
 387 /**
 388  * f2fs_encrypt() - Encrypts a page
 389  * @inode:          The inode for which the encryption should take place
 390  * @plaintext_page: The page to encrypt. Must be locked.
 391  *
 392  * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
 393  * encryption context.
 394  *
 395  * Called on the page write path.  The caller must call
 396  * f2fs_restore_control_page() on the returned ciphertext page to
 397  * release the bounce buffer and the encryption context.
 398  *
 399  * Return: An allocated page with the encrypted content on success. Else, an
 400  * error value or NULL.
 401  */
 402 struct page *f2fs_encrypt(struct inode *inode,
 403                           struct page *plaintext_page)
 404 {
 405         struct f2fs_crypto_ctx *ctx;
 406         struct page *ciphertext_page = NULL;
 407         int err;
 408
 409         BUG_ON(!PageLocked(plaintext_page));
 410
 411         ctx = f2fs_get_crypto_ctx(inode);
 412         if (IS_ERR(ctx))
 413                 return (struct page *)ctx;
 414
 415         /* The encryption operation will require a bounce page. */
 416         ciphertext_page = alloc_bounce_page(ctx);
 417         if (IS_ERR(ciphertext_page))
 418                 goto err_out;
 419
 420         ctx->w.control_page = plaintext_page;
 421         err = f2fs_page_crypto(ctx, inode, F2FS_ENCRYPT, plaintext_page->index,
 422                                         plaintext_page, ciphertext_page);
 423         if (err) {
 424                 ciphertext_page = ERR_PTR(err);
 425                 goto err_out;
 426         }
 427
 428         SetPagePrivate(ciphertext_page);
 429         set_page_private(ciphertext_page, (unsigned long)ctx);
 430         lock_page(ciphertext_page);
 431         return ciphertext_page;
 432
 433 err_out:
 434         f2fs_release_crypto_ctx(ctx);
 435         return ciphertext_page;
 436 }
 437
 438 /**
 439  * f2fs_decrypt() - Decrypts a page in-place
 440  * @ctx:  The encryption context.
 441  * @page: The page to decrypt. Must be locked.
 442  *
 443  * Decrypts page in-place using the ctx encryption context.
 444  *
 445  * Called from the read completion callback.
 446  *
 447  * Return: Zero on success, non-zero otherwise.
 448  */
 449 int f2fs_decrypt(struct f2fs_crypto_ctx *ctx, struct page *page)
 450 {
 451         BUG_ON(!PageLocked(page));
 452
 453         return f2fs_page_crypto(ctx, page->mapping->host,
 454                                 F2FS_DECRYPT, page->index, page, page);
 455 }
 456
 457 /*
 458  * Convenience function which takes care of allocating and
 459  * deallocating the encryption context
 460  */
 461 int f2fs_decrypt_one(struct inode *inode, struct page *page)
 462 {
 463         struct f2fs_crypto_ctx *ctx = f2fs_get_crypto_ctx(inode);
 464         int ret;
 465
 466         if (IS_ERR(ctx))
 467                 return PTR_ERR(ctx);
 468         ret = f2fs_decrypt(ctx, page);
 469         f2fs_release_crypto_ctx(ctx);
 470         return ret;
 471 }
 472
 473 bool f2fs_valid_contents_enc_mode(uint32_t mode)
 474 {
 475         return (mode == F2FS_ENCRYPTION_MODE_AES_256_XTS);
 476 }
 477
 478 /**
 479  * f2fs_validate_encryption_key_size() - Validate the encryption key size
 480  * @mode: The key mode.
 481  * @size: The key size to validate.
 482  *
 483  * Return: The validated key size for @mode. Zero if invalid.
 484  */
 485 uint32_t f2fs_validate_encryption_key_size(uint32_t mode, uint32_t size)
 486 {
 487         if (size == f2fs_encryption_key_size(mode))
 488                 return size;
 489         return 0;
 490 }