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