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 <crypto/skcipher.h> 24 #include <linux/export.h> 25 #include <linux/mempool.h> 26 #include <linux/module.h> 27 #include <linux/pagemap.h> 28 #include <linux/ratelimit.h> 29 #include <linux/scatterlist.h> 30 31 #include "fscrypt_private.h" 32 33 static unsigned int num_prealloc_crypto_pages = 32; 34 35 module_param(num_prealloc_crypto_pages, uint, 0444); 36 MODULE_PARM_DESC(num_prealloc_crypto_pages, 37 "Number of crypto pages to preallocate"); 38 39 static mempool_t *fscrypt_bounce_page_pool = NULL; 40 41 static struct workqueue_struct *fscrypt_read_workqueue; 42 static DEFINE_MUTEX(fscrypt_init_mutex); 43 44 struct kmem_cache *fscrypt_inode_info_cachep; 45 46 void fscrypt_enqueue_decrypt_work(struct work_struct *work) 47 { 48 queue_work(fscrypt_read_workqueue, work); 49 } 50 EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work); 51 52 struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags) 53 { 54 if (WARN_ON_ONCE(!fscrypt_bounce_page_pool)) { 55 /* 56 * Oops, the filesystem called a function that uses the bounce 57 * page pool, but it didn't set needs_bounce_pages. 58 */ 59 return NULL; 60 } 61 return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags); 62 } 63 64 /** 65 * fscrypt_free_bounce_page() - free a ciphertext bounce page 66 * @bounce_page: the bounce page to free, or NULL 67 * 68 * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(), 69 * or by fscrypt_alloc_bounce_page() directly. 70 */ 71 void fscrypt_free_bounce_page(struct page *bounce_page) 72 { 73 if (!bounce_page) 74 return; 75 set_page_private(bounce_page, (unsigned long)NULL); 76 ClearPagePrivate(bounce_page); 77 mempool_free(bounce_page, fscrypt_bounce_page_pool); 78 } 79 EXPORT_SYMBOL(fscrypt_free_bounce_page); 80 81 /* 82 * Generate the IV for the given data unit index within the given file. 83 * For filenames encryption, index == 0. 84 * 85 * Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks() 86 * needs to know about any IV generation methods where the low bits of IV don't 87 * simply contain the data unit index (e.g., IV_INO_LBLK_32). 88 */ 89 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index, 90 const struct fscrypt_inode_info *ci) 91 { 92 u8 flags = fscrypt_policy_flags(&ci->ci_policy); 93 94 memset(iv, 0, ci->ci_mode->ivsize); 95 96 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { 97 WARN_ON_ONCE(index > U32_MAX); 98 WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX); 99 index |= (u64)ci->ci_inode->i_ino << 32; 100 } else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { 101 WARN_ON_ONCE(index > U32_MAX); 102 index = (u32)(ci->ci_hashed_ino + index); 103 } else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { 104 memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE); 105 } 106 iv->index = cpu_to_le64(index); 107 } 108 109 /* Encrypt or decrypt a single "data unit" of file contents. */ 110 int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci, 111 fscrypt_direction_t rw, u64 index, 112 struct page *src_page, struct page *dest_page, 113 unsigned int len, unsigned int offs) 114 { 115 struct crypto_sync_skcipher *tfm = ci->ci_enc_key.tfm; 116 SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm); 117 union fscrypt_iv iv; 118 struct scatterlist dst, src; 119 int err; 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 skcipher_request_set_callback( 129 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, 130 NULL, NULL); 131 sg_init_table(&dst, 1); 132 sg_set_page(&dst, dest_page, len, offs); 133 sg_init_table(&src, 1); 134 sg_set_page(&src, src_page, len, offs); 135 skcipher_request_set_crypt(req, &src, &dst, len, &iv); 136 if (rw == FS_DECRYPT) 137 err = crypto_skcipher_decrypt(req); 138 else 139 err = crypto_skcipher_encrypt(req); 140 if (err) 141 fscrypt_err(ci->ci_inode, 142 "%scryption failed for data unit %llu: %d", 143 (rw == FS_DECRYPT ? "De" : "En"), index, err); 144 return err; 145 } 146 147 /** 148 * fscrypt_encrypt_pagecache_blocks() - Encrypt data from a pagecache folio 149 * @folio: the locked pagecache folio containing the data to encrypt 150 * @len: size of the data to encrypt, in bytes 151 * @offs: offset within @page of the data to encrypt, in bytes 152 * @gfp_flags: memory allocation flags; see details below 153 * 154 * This allocates a new bounce page and encrypts the given data into it. The 155 * length and offset of the data must be aligned to the file's crypto data unit 156 * size. Alignment to the filesystem block size fulfills this requirement, as 157 * the filesystem block size is always a multiple of the data unit size. 158 * 159 * In the bounce page, the ciphertext data will be located at the same offset at 160 * which the plaintext data was located in the source page. Any other parts of 161 * the bounce page will be left uninitialized. 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 folio *folio, 173 size_t len, size_t offs, gfp_t gfp_flags) 174 { 175 const struct inode *inode = folio->mapping->host; 176 const struct fscrypt_inode_info *ci = inode->i_crypt_info; 177 const unsigned int du_bits = ci->ci_data_unit_bits; 178 const unsigned int du_size = 1U << du_bits; 179 struct page *ciphertext_page; 180 u64 index = ((u64)folio->index << (PAGE_SHIFT - du_bits)) + 181 (offs >> du_bits); 182 unsigned int i; 183 int err; 184 185 VM_BUG_ON_FOLIO(folio_test_large(folio), folio); 186 if (WARN_ON_ONCE(!folio_test_locked(folio))) 187 return ERR_PTR(-EINVAL); 188 189 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size))) 190 return ERR_PTR(-EINVAL); 191 192 ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags); 193 if (!ciphertext_page) 194 return ERR_PTR(-ENOMEM); 195 196 for (i = offs; i < offs + len; i += du_size, index++) { 197 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, index, 198 &folio->page, ciphertext_page, 199 du_size, i); 200 if (err) { 201 fscrypt_free_bounce_page(ciphertext_page); 202 return ERR_PTR(err); 203 } 204 } 205 SetPagePrivate(ciphertext_page); 206 set_page_private(ciphertext_page, (unsigned long)folio); 207 return ciphertext_page; 208 } 209 EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks); 210 211 /** 212 * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place 213 * @inode: The inode to which this block belongs 214 * @page: The page containing the block to encrypt 215 * @len: Size of block to encrypt. This must be a multiple of 216 * FSCRYPT_CONTENTS_ALIGNMENT. 217 * @offs: Byte offset within @page at which the block to encrypt begins 218 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based 219 * number of the block within the file 220 * 221 * Encrypt a possibly-compressed filesystem block that is located in an 222 * arbitrary page, not necessarily in the original pagecache page. The @inode 223 * and @lblk_num must be specified, as they can't be determined from @page. 224 * 225 * This is not compatible with fscrypt_operations::supports_subblock_data_units. 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) 232 { 233 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) 234 return -EOPNOTSUPP; 235 return fscrypt_crypt_data_unit(inode->i_crypt_info, FS_ENCRYPT, 236 lblk_num, page, page, len, offs); 237 } 238 EXPORT_SYMBOL(fscrypt_encrypt_block_inplace); 239 240 /** 241 * fscrypt_decrypt_pagecache_blocks() - Decrypt data from a pagecache folio 242 * @folio: the pagecache folio containing the data to decrypt 243 * @len: size of the data to decrypt, in bytes 244 * @offs: offset within @folio of the data to decrypt, in bytes 245 * 246 * Decrypt data that has just been read from an encrypted file. The data must 247 * be located in a pagecache folio that is still locked and not yet uptodate. 248 * The length and offset of the data must be aligned to the file's crypto data 249 * unit size. Alignment to the filesystem block size fulfills this requirement, 250 * as the filesystem block size is always a multiple of the data unit size. 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 struct fscrypt_inode_info *ci = inode->i_crypt_info; 259 const unsigned int du_bits = ci->ci_data_unit_bits; 260 const unsigned int du_size = 1U << du_bits; 261 u64 index = ((u64)folio->index << (PAGE_SHIFT - du_bits)) + 262 (offs >> du_bits); 263 size_t i; 264 int err; 265 266 if (WARN_ON_ONCE(!folio_test_locked(folio))) 267 return -EINVAL; 268 269 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size))) 270 return -EINVAL; 271 272 for (i = offs; i < offs + len; i += du_size, index++) { 273 struct page *page = folio_page(folio, i >> PAGE_SHIFT); 274 275 err = fscrypt_crypt_data_unit(ci, FS_DECRYPT, index, page, 276 page, du_size, i & ~PAGE_MASK); 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 * This is not compatible with fscrypt_operations::supports_subblock_data_units. 299 * 300 * Return: 0 on success; -errno on failure 301 */ 302 int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page, 303 unsigned int len, unsigned int offs, 304 u64 lblk_num) 305 { 306 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) 307 return -EOPNOTSUPP; 308 return fscrypt_crypt_data_unit(inode->i_crypt_info, FS_DECRYPT, 309 lblk_num, page, page, len, offs); 310 } 311 EXPORT_SYMBOL(fscrypt_decrypt_block_inplace); 312 313 /** 314 * fscrypt_initialize() - allocate major buffers for fs encryption. 315 * @sb: the filesystem superblock 316 * 317 * We only call this when we start accessing encrypted files, since it 318 * results in memory getting allocated that wouldn't otherwise be used. 319 * 320 * Return: 0 on success; -errno on failure 321 */ 322 int fscrypt_initialize(struct super_block *sb) 323 { 324 int err = 0; 325 mempool_t *pool; 326 327 /* pairs with smp_store_release() below */ 328 if (likely(smp_load_acquire(&fscrypt_bounce_page_pool))) 329 return 0; 330 331 /* No need to allocate a bounce page pool if this FS won't use it. */ 332 if (!sb->s_cop->needs_bounce_pages) 333 return 0; 334 335 mutex_lock(&fscrypt_init_mutex); 336 if (fscrypt_bounce_page_pool) 337 goto out_unlock; 338 339 err = -ENOMEM; 340 pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0); 341 if (!pool) 342 goto out_unlock; 343 /* pairs with smp_load_acquire() above */ 344 smp_store_release(&fscrypt_bounce_page_pool, pool); 345 err = 0; 346 out_unlock: 347 mutex_unlock(&fscrypt_init_mutex); 348 return err; 349 } 350 351 void fscrypt_msg(const struct inode *inode, const char *level, 352 const char *fmt, ...) 353 { 354 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, 355 DEFAULT_RATELIMIT_BURST); 356 struct va_format vaf; 357 va_list args; 358 359 if (!__ratelimit(&rs)) 360 return; 361 362 va_start(args, fmt); 363 vaf.fmt = fmt; 364 vaf.va = &args; 365 if (inode && inode->i_ino) 366 printk("%sfscrypt (%s, inode %lu): %pV\n", 367 level, inode->i_sb->s_id, inode->i_ino, &vaf); 368 else if (inode) 369 printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf); 370 else 371 printk("%sfscrypt: %pV\n", level, &vaf); 372 va_end(args); 373 } 374 375 /** 376 * fscrypt_init() - Set up for fs encryption. 377 * 378 * Return: 0 on success; -errno on failure 379 */ 380 static int __init fscrypt_init(void) 381 { 382 int err = -ENOMEM; 383 384 /* 385 * Use an unbound workqueue to allow bios to be decrypted in parallel 386 * even when they happen to complete on the same CPU. This sacrifices 387 * locality, but it's worthwhile since decryption is CPU-intensive. 388 * 389 * Also use a high-priority workqueue to prioritize decryption work, 390 * which blocks reads from completing, over regular application tasks. 391 */ 392 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue", 393 WQ_UNBOUND | WQ_HIGHPRI, 394 num_online_cpus()); 395 if (!fscrypt_read_workqueue) 396 goto fail; 397 398 fscrypt_inode_info_cachep = KMEM_CACHE(fscrypt_inode_info, 399 SLAB_RECLAIM_ACCOUNT); 400 if (!fscrypt_inode_info_cachep) 401 goto fail_free_queue; 402 403 err = fscrypt_init_keyring(); 404 if (err) 405 goto fail_free_inode_info; 406 407 return 0; 408 409 fail_free_inode_info: 410 kmem_cache_destroy(fscrypt_inode_info_cachep); 411 fail_free_queue: 412 destroy_workqueue(fscrypt_read_workqueue); 413 fail: 414 return err; 415 } 416 late_initcall(fscrypt_init) 417