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