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