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 = fscrypt_get_inode_info_raw(inode); 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(fscrypt_get_inode_info_raw(inode), 236 FS_ENCRYPT, lblk_num, page, page, len, 237 offs); 238 } 239 EXPORT_SYMBOL(fscrypt_encrypt_block_inplace); 240 241 /** 242 * fscrypt_decrypt_pagecache_blocks() - Decrypt data from a pagecache folio 243 * @folio: the pagecache folio containing the data to decrypt 244 * @len: size of the data to decrypt, in bytes 245 * @offs: offset within @folio of the data to decrypt, in bytes 246 * 247 * Decrypt data that has just been read from an encrypted file. The data must 248 * be located in a pagecache folio that is still locked and not yet uptodate. 249 * The length and offset of the data must be aligned to the file's crypto data 250 * unit size. Alignment to the filesystem block size fulfills this requirement, 251 * as the filesystem block size is always a multiple of the data unit size. 252 * 253 * Return: 0 on success; -errno on failure 254 */ 255 int fscrypt_decrypt_pagecache_blocks(struct folio *folio, size_t len, 256 size_t offs) 257 { 258 const struct inode *inode = folio->mapping->host; 259 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode); 260 const unsigned int du_bits = ci->ci_data_unit_bits; 261 const unsigned int du_size = 1U << du_bits; 262 u64 index = ((u64)folio->index << (PAGE_SHIFT - du_bits)) + 263 (offs >> du_bits); 264 size_t i; 265 int err; 266 267 if (WARN_ON_ONCE(!folio_test_locked(folio))) 268 return -EINVAL; 269 270 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size))) 271 return -EINVAL; 272 273 for (i = offs; i < offs + len; i += du_size, index++) { 274 struct page *page = folio_page(folio, i >> PAGE_SHIFT); 275 276 err = fscrypt_crypt_data_unit(ci, FS_DECRYPT, index, page, 277 page, du_size, i & ~PAGE_MASK); 278 if (err) 279 return err; 280 } 281 return 0; 282 } 283 EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks); 284 285 /** 286 * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place 287 * @inode: The inode to which this block belongs 288 * @page: The page containing the block to decrypt 289 * @len: Size of block to decrypt. This must be a multiple of 290 * FSCRYPT_CONTENTS_ALIGNMENT. 291 * @offs: Byte offset within @page at which the block to decrypt begins 292 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based 293 * number of the block within the file 294 * 295 * Decrypt a possibly-compressed filesystem block that is located in an 296 * arbitrary page, not necessarily in the original pagecache page. The @inode 297 * and @lblk_num must be specified, as they can't be determined from @page. 298 * 299 * This is not compatible with fscrypt_operations::supports_subblock_data_units. 300 * 301 * Return: 0 on success; -errno on failure 302 */ 303 int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page, 304 unsigned int len, unsigned int offs, 305 u64 lblk_num) 306 { 307 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) 308 return -EOPNOTSUPP; 309 return fscrypt_crypt_data_unit(fscrypt_get_inode_info_raw(inode), 310 FS_DECRYPT, lblk_num, page, page, len, 311 offs); 312 } 313 EXPORT_SYMBOL(fscrypt_decrypt_block_inplace); 314 315 /** 316 * fscrypt_initialize() - allocate major buffers for fs encryption. 317 * @sb: the filesystem superblock 318 * 319 * We only call this when we start accessing encrypted files, since it 320 * results in memory getting allocated that wouldn't otherwise be used. 321 * 322 * Return: 0 on success; -errno on failure 323 */ 324 int fscrypt_initialize(struct super_block *sb) 325 { 326 int err = 0; 327 mempool_t *pool; 328 329 /* pairs with smp_store_release() below */ 330 if (likely(smp_load_acquire(&fscrypt_bounce_page_pool))) 331 return 0; 332 333 /* No need to allocate a bounce page pool if this FS won't use it. */ 334 if (!sb->s_cop->needs_bounce_pages) 335 return 0; 336 337 mutex_lock(&fscrypt_init_mutex); 338 if (fscrypt_bounce_page_pool) 339 goto out_unlock; 340 341 err = -ENOMEM; 342 pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0); 343 if (!pool) 344 goto out_unlock; 345 /* pairs with smp_load_acquire() above */ 346 smp_store_release(&fscrypt_bounce_page_pool, pool); 347 err = 0; 348 out_unlock: 349 mutex_unlock(&fscrypt_init_mutex); 350 return err; 351 } 352 353 void fscrypt_msg(const struct inode *inode, const char *level, 354 const char *fmt, ...) 355 { 356 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, 357 DEFAULT_RATELIMIT_BURST); 358 struct va_format vaf; 359 va_list args; 360 361 if (!__ratelimit(&rs)) 362 return; 363 364 va_start(args, fmt); 365 vaf.fmt = fmt; 366 vaf.va = &args; 367 if (inode && inode->i_ino) 368 printk("%sfscrypt (%s, inode %lu): %pV\n", 369 level, inode->i_sb->s_id, inode->i_ino, &vaf); 370 else if (inode) 371 printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf); 372 else 373 printk("%sfscrypt: %pV\n", level, &vaf); 374 va_end(args); 375 } 376 377 /** 378 * fscrypt_init() - Set up for fs encryption. 379 * 380 * Return: 0 on success; -errno on failure 381 */ 382 static int __init fscrypt_init(void) 383 { 384 int err = -ENOMEM; 385 386 /* 387 * Use an unbound workqueue to allow bios to be decrypted in parallel 388 * even when they happen to complete on the same CPU. This sacrifices 389 * locality, but it's worthwhile since decryption is CPU-intensive. 390 * 391 * Also use a high-priority workqueue to prioritize decryption work, 392 * which blocks reads from completing, over regular application tasks. 393 */ 394 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue", 395 WQ_UNBOUND | WQ_HIGHPRI, 396 num_online_cpus()); 397 if (!fscrypt_read_workqueue) 398 goto fail; 399 400 fscrypt_inode_info_cachep = KMEM_CACHE(fscrypt_inode_info, 401 SLAB_RECLAIM_ACCOUNT); 402 if (!fscrypt_inode_info_cachep) 403 goto fail_free_queue; 404 405 err = fscrypt_init_keyring(); 406 if (err) 407 goto fail_free_inode_info; 408 409 return 0; 410 411 fail_free_inode_info: 412 kmem_cache_destroy(fscrypt_inode_info_cachep); 413 fail_free_queue: 414 destroy_workqueue(fscrypt_read_workqueue); 415 fail: 416 return err; 417 } 418 late_initcall(fscrypt_init) 419