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