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 <crypto/skcipher.h> 29 #include "fscrypt_private.h" 30 31 static unsigned int num_prealloc_crypto_pages = 32; 32 33 module_param(num_prealloc_crypto_pages, uint, 0444); 34 MODULE_PARM_DESC(num_prealloc_crypto_pages, 35 "Number of crypto pages to preallocate"); 36 37 static mempool_t *fscrypt_bounce_page_pool = NULL; 38 39 static struct workqueue_struct *fscrypt_read_workqueue; 40 static DEFINE_MUTEX(fscrypt_init_mutex); 41 42 struct kmem_cache *fscrypt_inode_info_cachep; 43 44 void fscrypt_enqueue_decrypt_work(struct work_struct *work) 45 { 46 queue_work(fscrypt_read_workqueue, work); 47 } 48 EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work); 49 50 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags) 51 { 52 if (WARN_ON_ONCE(!fscrypt_bounce_page_pool)) { 53 /* 54 * Oops, the filesystem called a function that uses the bounce 55 * page pool, but it didn't set needs_bounce_pages. 56 */ 57 return NULL; 58 } 59 return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags); 60 } 61 62 /** 63 * fscrypt_free_bounce_page() - free a ciphertext bounce page 64 * @bounce_page: the bounce page to free, or NULL 65 * 66 * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(), 67 * or by fscrypt_alloc_bounce_page() directly. 68 */ 69 void fscrypt_free_bounce_page(struct page *bounce_page) 70 { 71 if (!bounce_page) 72 return; 73 set_page_private(bounce_page, (unsigned long)NULL); 74 ClearPagePrivate(bounce_page); 75 mempool_free(bounce_page, fscrypt_bounce_page_pool); 76 } 77 EXPORT_SYMBOL(fscrypt_free_bounce_page); 78 79 /* 80 * Generate the IV for the given data unit index within the given file. 81 * For filenames encryption, index == 0. 82 * 83 * Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks() 84 * needs to know about any IV generation methods where the low bits of IV don't 85 * simply contain the data unit index (e.g., IV_INO_LBLK_32). 86 */ 87 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index, 88 const struct fscrypt_inode_info *ci) 89 { 90 u8 flags = fscrypt_policy_flags(&ci->ci_policy); 91 92 memset(iv, 0, ci->ci_mode->ivsize); 93 94 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { 95 WARN_ON_ONCE(index > U32_MAX); 96 WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX); 97 index |= (u64)ci->ci_inode->i_ino << 32; 98 } else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { 99 WARN_ON_ONCE(index > U32_MAX); 100 index = (u32)(ci->ci_hashed_ino + index); 101 } else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { 102 memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE); 103 } 104 iv->index = cpu_to_le64(index); 105 } 106 107 /* Encrypt or decrypt a single "data unit" of file contents. */ 108 int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci, 109 fscrypt_direction_t rw, u64 index, 110 struct page *src_page, struct page *dest_page, 111 unsigned int len, unsigned int offs, 112 gfp_t gfp_flags) 113 { 114 union fscrypt_iv iv; 115 struct skcipher_request *req = NULL; 116 DECLARE_CRYPTO_WAIT(wait); 117 struct scatterlist dst, src; 118 struct crypto_skcipher *tfm = ci->ci_enc_key.tfm; 119 int res = 0; 120 121 if (WARN_ON_ONCE(len <= 0)) 122 return -EINVAL; 123 if (WARN_ON_ONCE(len % FSCRYPT_CONTENTS_ALIGNMENT != 0)) 124 return -EINVAL; 125 126 fscrypt_generate_iv(&iv, index, ci); 127 128 req = skcipher_request_alloc(tfm, gfp_flags); 129 if (!req) 130 return -ENOMEM; 131 132 skcipher_request_set_callback( 133 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, 134 crypto_req_done, &wait); 135 136 sg_init_table(&dst, 1); 137 sg_set_page(&dst, dest_page, len, offs); 138 sg_init_table(&src, 1); 139 sg_set_page(&src, src_page, len, offs); 140 skcipher_request_set_crypt(req, &src, &dst, len, &iv); 141 if (rw == FS_DECRYPT) 142 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait); 143 else 144 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); 145 skcipher_request_free(req); 146 if (res) { 147 fscrypt_err(ci->ci_inode, 148 "%scryption failed for data unit %llu: %d", 149 (rw == FS_DECRYPT ? "De" : "En"), index, res); 150 return res; 151 } 152 return 0; 153 } 154 155 /** 156 * fscrypt_encrypt_pagecache_blocks() - Encrypt data from a pagecache page 157 * @page: the locked pagecache page containing the data to encrypt 158 * @len: size of the data to encrypt, in bytes 159 * @offs: offset within @page of the data to encrypt, in bytes 160 * @gfp_flags: memory allocation flags; see details below 161 * 162 * This allocates a new bounce page and encrypts the given data into it. The 163 * length and offset of the data must be aligned to the file's crypto data unit 164 * size. Alignment to the filesystem block size fulfills this requirement, as 165 * the filesystem block size is always a multiple of the data unit size. 166 * 167 * In the bounce page, the ciphertext data will be located at the same offset at 168 * which the plaintext data was located in the source page. Any other parts of 169 * the bounce page will be left uninitialized. 170 * 171 * This is for use by the filesystem's ->writepages() method. 172 * 173 * The bounce page allocation is mempool-backed, so it will always succeed when 174 * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However, 175 * only the first page of each bio can be allocated this way. To prevent 176 * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used. 177 * 178 * Return: the new encrypted bounce page on success; an ERR_PTR() on failure 179 */ 180 struct page *fscrypt_encrypt_pagecache_blocks(struct page *page, 181 unsigned int len, 182 unsigned int offs, 183 gfp_t gfp_flags) 184 185 { 186 const struct inode *inode = page->mapping->host; 187 const struct fscrypt_inode_info *ci = inode->i_crypt_info; 188 const unsigned int du_bits = ci->ci_data_unit_bits; 189 const unsigned int du_size = 1U << du_bits; 190 struct page *ciphertext_page; 191 u64 index = ((u64)page->index << (PAGE_SHIFT - du_bits)) + 192 (offs >> du_bits); 193 unsigned int i; 194 int err; 195 196 if (WARN_ON_ONCE(!PageLocked(page))) 197 return ERR_PTR(-EINVAL); 198 199 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size))) 200 return ERR_PTR(-EINVAL); 201 202 ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags); 203 if (!ciphertext_page) 204 return ERR_PTR(-ENOMEM); 205 206 for (i = offs; i < offs + len; i += du_size, index++) { 207 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, index, 208 page, ciphertext_page, 209 du_size, i, gfp_flags); 210 if (err) { 211 fscrypt_free_bounce_page(ciphertext_page); 212 return ERR_PTR(err); 213 } 214 } 215 SetPagePrivate(ciphertext_page); 216 set_page_private(ciphertext_page, (unsigned long)page); 217 return ciphertext_page; 218 } 219 EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks); 220 221 /** 222 * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place 223 * @inode: The inode to which this block belongs 224 * @page: The page containing the block to encrypt 225 * @len: Size of block to encrypt. This must be a multiple of 226 * FSCRYPT_CONTENTS_ALIGNMENT. 227 * @offs: Byte offset within @page at which the block to encrypt begins 228 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based 229 * number of the block within the file 230 * @gfp_flags: Memory allocation flags 231 * 232 * Encrypt a possibly-compressed filesystem block that is located in an 233 * arbitrary page, not necessarily in the original pagecache page. The @inode 234 * and @lblk_num must be specified, as they can't be determined from @page. 235 * 236 * This is not compatible with fscrypt_operations::supports_subblock_data_units. 237 * 238 * Return: 0 on success; -errno on failure 239 */ 240 int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page, 241 unsigned int len, unsigned int offs, 242 u64 lblk_num, gfp_t gfp_flags) 243 { 244 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) 245 return -EOPNOTSUPP; 246 return fscrypt_crypt_data_unit(inode->i_crypt_info, FS_ENCRYPT, 247 lblk_num, page, page, len, offs, 248 gfp_flags); 249 } 250 EXPORT_SYMBOL(fscrypt_encrypt_block_inplace); 251 252 /** 253 * fscrypt_decrypt_pagecache_blocks() - Decrypt data from a pagecache folio 254 * @folio: the pagecache folio containing the data to decrypt 255 * @len: size of the data to decrypt, in bytes 256 * @offs: offset within @folio of the data to decrypt, in bytes 257 * 258 * Decrypt data that has just been read from an encrypted file. The data must 259 * be located in a pagecache folio that is still locked and not yet uptodate. 260 * The length and offset of the data must be aligned to the file's crypto data 261 * unit size. Alignment to the filesystem block size fulfills this requirement, 262 * as the filesystem block size is always a multiple of the data unit size. 263 * 264 * Return: 0 on success; -errno on failure 265 */ 266 int fscrypt_decrypt_pagecache_blocks(struct folio *folio, size_t len, 267 size_t offs) 268 { 269 const struct inode *inode = folio->mapping->host; 270 const struct fscrypt_inode_info *ci = inode->i_crypt_info; 271 const unsigned int du_bits = ci->ci_data_unit_bits; 272 const unsigned int du_size = 1U << du_bits; 273 u64 index = ((u64)folio->index << (PAGE_SHIFT - du_bits)) + 274 (offs >> du_bits); 275 size_t i; 276 int err; 277 278 if (WARN_ON_ONCE(!folio_test_locked(folio))) 279 return -EINVAL; 280 281 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size))) 282 return -EINVAL; 283 284 for (i = offs; i < offs + len; i += du_size, index++) { 285 struct page *page = folio_page(folio, i >> PAGE_SHIFT); 286 287 err = fscrypt_crypt_data_unit(ci, FS_DECRYPT, index, page, 288 page, du_size, i & ~PAGE_MASK, 289 GFP_NOFS); 290 if (err) 291 return err; 292 } 293 return 0; 294 } 295 EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks); 296 297 /** 298 * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place 299 * @inode: The inode to which this block belongs 300 * @page: The page containing the block to decrypt 301 * @len: Size of block to decrypt. This must be a multiple of 302 * FSCRYPT_CONTENTS_ALIGNMENT. 303 * @offs: Byte offset within @page at which the block to decrypt begins 304 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based 305 * number of the block within the file 306 * 307 * Decrypt a possibly-compressed filesystem block that is located in an 308 * arbitrary page, not necessarily in the original pagecache page. The @inode 309 * and @lblk_num must be specified, as they can't be determined from @page. 310 * 311 * This is not compatible with fscrypt_operations::supports_subblock_data_units. 312 * 313 * Return: 0 on success; -errno on failure 314 */ 315 int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page, 316 unsigned int len, unsigned int offs, 317 u64 lblk_num) 318 { 319 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) 320 return -EOPNOTSUPP; 321 return fscrypt_crypt_data_unit(inode->i_crypt_info, FS_DECRYPT, 322 lblk_num, page, page, len, offs, 323 GFP_NOFS); 324 } 325 EXPORT_SYMBOL(fscrypt_decrypt_block_inplace); 326 327 /** 328 * fscrypt_initialize() - allocate major buffers for fs encryption. 329 * @sb: the filesystem superblock 330 * 331 * We only call this when we start accessing encrypted files, since it 332 * results in memory getting allocated that wouldn't otherwise be used. 333 * 334 * Return: 0 on success; -errno on failure 335 */ 336 int fscrypt_initialize(struct super_block *sb) 337 { 338 int err = 0; 339 mempool_t *pool; 340 341 /* pairs with smp_store_release() below */ 342 if (likely(smp_load_acquire(&fscrypt_bounce_page_pool))) 343 return 0; 344 345 /* No need to allocate a bounce page pool if this FS won't use it. */ 346 if (!sb->s_cop->needs_bounce_pages) 347 return 0; 348 349 mutex_lock(&fscrypt_init_mutex); 350 if (fscrypt_bounce_page_pool) 351 goto out_unlock; 352 353 err = -ENOMEM; 354 pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0); 355 if (!pool) 356 goto out_unlock; 357 /* pairs with smp_load_acquire() above */ 358 smp_store_release(&fscrypt_bounce_page_pool, pool); 359 err = 0; 360 out_unlock: 361 mutex_unlock(&fscrypt_init_mutex); 362 return err; 363 } 364 365 void fscrypt_msg(const struct inode *inode, const char *level, 366 const char *fmt, ...) 367 { 368 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, 369 DEFAULT_RATELIMIT_BURST); 370 struct va_format vaf; 371 va_list args; 372 373 if (!__ratelimit(&rs)) 374 return; 375 376 va_start(args, fmt); 377 vaf.fmt = fmt; 378 vaf.va = &args; 379 if (inode && inode->i_ino) 380 printk("%sfscrypt (%s, inode %lu): %pV\n", 381 level, inode->i_sb->s_id, inode->i_ino, &vaf); 382 else if (inode) 383 printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf); 384 else 385 printk("%sfscrypt: %pV\n", level, &vaf); 386 va_end(args); 387 } 388 389 /** 390 * fscrypt_init() - Set up for fs encryption. 391 * 392 * Return: 0 on success; -errno on failure 393 */ 394 static int __init fscrypt_init(void) 395 { 396 int err = -ENOMEM; 397 398 /* 399 * Use an unbound workqueue to allow bios to be decrypted in parallel 400 * even when they happen to complete on the same CPU. This sacrifices 401 * locality, but it's worthwhile since decryption is CPU-intensive. 402 * 403 * Also use a high-priority workqueue to prioritize decryption work, 404 * which blocks reads from completing, over regular application tasks. 405 */ 406 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue", 407 WQ_UNBOUND | WQ_HIGHPRI, 408 num_online_cpus()); 409 if (!fscrypt_read_workqueue) 410 goto fail; 411 412 fscrypt_inode_info_cachep = KMEM_CACHE(fscrypt_inode_info, 413 SLAB_RECLAIM_ACCOUNT); 414 if (!fscrypt_inode_info_cachep) 415 goto fail_free_queue; 416 417 err = fscrypt_init_keyring(); 418 if (err) 419 goto fail_free_inode_info; 420 421 return 0; 422 423 fail_free_inode_info: 424 kmem_cache_destroy(fscrypt_inode_info_cachep); 425 fail_free_queue: 426 destroy_workqueue(fscrypt_read_workqueue); 427 fail: 428 return err; 429 } 430 late_initcall(fscrypt_init) 431