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 DEFINE_MUTEX(fscrypt_init_mutex); 42 43 struct kmem_cache *fscrypt_inode_info_cachep; 44 45 static struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags) 46 { 47 if (WARN_ON_ONCE(!fscrypt_bounce_page_pool)) { 48 /* 49 * Oops, the filesystem called a function that uses the bounce 50 * page pool, but it didn't set needs_bounce_pages. 51 */ 52 return NULL; 53 } 54 return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags); 55 } 56 57 /** 58 * fscrypt_free_bounce_page() - free a ciphertext bounce page 59 * @bounce_page: the bounce page to free, or NULL 60 * 61 * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(). 62 */ 63 void fscrypt_free_bounce_page(struct page *bounce_page) 64 { 65 if (!bounce_page) 66 return; 67 set_page_private(bounce_page, (unsigned long)NULL); 68 ClearPagePrivate(bounce_page); 69 mempool_free(bounce_page, fscrypt_bounce_page_pool); 70 } 71 EXPORT_SYMBOL(fscrypt_free_bounce_page); 72 73 /* 74 * Generate the IV for the given data unit index within the given file. 75 * For filenames encryption, index == 0. 76 * 77 * Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks() 78 * needs to know about any IV generation methods where the low bits of IV don't 79 * simply contain the data unit index (e.g., IV_INO_LBLK_32). 80 */ 81 void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index, 82 const struct fscrypt_inode_info *ci) 83 { 84 u8 flags = fscrypt_policy_flags(&ci->ci_policy); 85 86 memset(iv, 0, sizeof(*iv)); 87 88 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { 89 WARN_ON_ONCE(index > U32_MAX); 90 WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX); 91 index |= (u64)ci->ci_inode->i_ino << 32; 92 } else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { 93 WARN_ON_ONCE(index > U32_MAX); 94 index = (u32)(ci->ci_hashed_ino + index); 95 } else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { 96 memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE); 97 } 98 iv->index = cpu_to_le64(index); 99 } 100 101 typedef enum { 102 FS_DECRYPT = 0, 103 FS_ENCRYPT, 104 } fscrypt_direction_t; 105 106 /* Encrypt or decrypt a single "data unit" of file contents. */ 107 static int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci, 108 fscrypt_direction_t rw, u64 index, 109 struct page *src_page, 110 struct page *dest_page, unsigned int len, 111 unsigned int offs) 112 { 113 struct crypto_sync_skcipher *tfm; 114 union fscrypt_iv iv; 115 struct scatterlist dst, src; 116 int err; 117 118 if (WARN_ON_ONCE(ci == NULL)) /* File hasn't been opened yet? */ 119 return -ENOKEY; 120 tfm = ci->ci_enc_key.tfm; 121 if (WARN_ON_ONCE(tfm == NULL)) /* Called on block-based filesystem? */ 122 return -ENOKEY; 123 124 if (WARN_ON_ONCE(len <= 0)) 125 return -EINVAL; 126 if (WARN_ON_ONCE(len % FSCRYPT_CONTENTS_ALIGNMENT != 0)) 127 return -EINVAL; 128 129 fscrypt_generate_iv(&iv, index, ci); 130 131 { 132 SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm); 133 skcipher_request_set_callback(req, 134 CRYPTO_TFM_REQ_MAY_BACKLOG | 135 CRYPTO_TFM_REQ_MAY_SLEEP, 136 NULL, NULL); 137 sg_init_table(&dst, 1); 138 sg_set_page(&dst, dest_page, len, offs); 139 sg_init_table(&src, 1); 140 sg_set_page(&src, src_page, len, offs); 141 skcipher_request_set_crypt(req, &src, &dst, len, &iv); 142 if (rw == FS_DECRYPT) 143 err = crypto_skcipher_decrypt(req); 144 else 145 err = crypto_skcipher_encrypt(req); 146 } 147 if (err) 148 fscrypt_err(ci->ci_inode, 149 "%scryption failed for data unit %llu: %d", 150 (rw == FS_DECRYPT ? "De" : "En"), index, err); 151 return err; 152 } 153 154 /** 155 * fscrypt_encrypt_pagecache_blocks() - Encrypt data from a pagecache folio 156 * @folio: the locked pagecache folio containing the data to encrypt 157 * @len: size of the data to encrypt, in bytes 158 * @offs: offset within @page of the data to encrypt, in bytes 159 * @gfp_flags: memory allocation flags; see details below 160 * 161 * This allocates a new bounce page and encrypts the given data into it. The 162 * length and offset of the data must be aligned to the file's crypto data unit 163 * size. Alignment to the filesystem block size fulfills this requirement, as 164 * the filesystem block size is always a multiple of the data unit size. 165 * 166 * In the bounce page, the ciphertext data will be located at the same offset at 167 * which the plaintext data was located in the source page. Any other parts of 168 * the bounce page will be left uninitialized. 169 * 170 * This is for use by the ->writepages() method of non-block-based filesystems. 171 * 172 * The bounce page allocation is mempool-backed, so it will always succeed when 173 * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However, 174 * only the first page of each bio can be allocated this way. To prevent 175 * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used. 176 * 177 * Return: the new encrypted bounce page on success; an ERR_PTR() on failure 178 */ 179 struct page *fscrypt_encrypt_pagecache_blocks(struct folio *folio, 180 size_t len, size_t offs, gfp_t gfp_flags) 181 { 182 const struct inode *inode = folio->mapping->host; 183 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode); 184 unsigned int du_bits; 185 unsigned int du_size; 186 struct page *ciphertext_page; 187 u64 index; 188 unsigned int i; 189 int err; 190 191 if (WARN_ON_ONCE(ci == NULL)) /* File hasn't been opened yet? */ 192 return ERR_PTR(-ENOKEY); 193 194 du_bits = ci->ci_data_unit_bits; 195 du_size = 1U << du_bits; 196 index = (folio_pos(folio) + offs) >> du_bits; 197 198 VM_BUG_ON_FOLIO(folio_test_large(folio), folio); 199 if (WARN_ON_ONCE(!folio_test_locked(folio))) 200 return ERR_PTR(-EINVAL); 201 202 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size))) 203 return ERR_PTR(-EINVAL); 204 205 ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags); 206 if (!ciphertext_page) 207 return ERR_PTR(-ENOMEM); 208 209 for (i = offs; i < offs + len; i += du_size, index++) { 210 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, index, 211 &folio->page, ciphertext_page, 212 du_size, i); 213 if (err) { 214 fscrypt_free_bounce_page(ciphertext_page); 215 return ERR_PTR(err); 216 } 217 } 218 SetPagePrivate(ciphertext_page); 219 set_page_private(ciphertext_page, (unsigned long)folio); 220 return ciphertext_page; 221 } 222 EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks); 223 224 /** 225 * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place 226 * @inode: The inode to which this block belongs 227 * @page: The page containing the block to encrypt 228 * @len: Size of block to encrypt. This must be a multiple of 229 * FSCRYPT_CONTENTS_ALIGNMENT. 230 * @offs: Byte offset within @page at which the block to encrypt begins 231 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based 232 * number of the block within the file 233 * 234 * Encrypt a possibly-compressed filesystem block that is located in an 235 * arbitrary page, not necessarily in the original pagecache page. The @inode 236 * and @lblk_num must be specified, as they can't be determined from @page. 237 * 238 * This function only supports non-block-based filesystems that don't support 239 * sub-block data units (as indicated by the fscrypt_operations fields). 240 * 241 * Return: 0 on success; -errno on failure 242 */ 243 int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page, 244 unsigned int len, unsigned int offs, 245 u64 lblk_num) 246 { 247 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) 248 return -EOPNOTSUPP; 249 return fscrypt_crypt_data_unit(fscrypt_get_inode_info_raw(inode), 250 FS_ENCRYPT, lblk_num, page, page, len, 251 offs); 252 } 253 EXPORT_SYMBOL(fscrypt_encrypt_block_inplace); 254 255 /** 256 * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place 257 * @inode: The inode to which this block belongs 258 * @page: The page containing the block to decrypt 259 * @len: Size of block to decrypt. This must be a multiple of 260 * FSCRYPT_CONTENTS_ALIGNMENT. 261 * @offs: Byte offset within @page at which the block to decrypt begins 262 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based 263 * number of the block within the file 264 * 265 * Decrypt a possibly-compressed filesystem block that is located in an 266 * arbitrary page, not necessarily in the original pagecache page. The @inode 267 * and @lblk_num must be specified, as they can't be determined from @page. 268 * 269 * This function only supports non-block-based filesystems that don't support 270 * sub-block data units (as indicated by the fscrypt_operations fields). 271 * 272 * Return: 0 on success; -errno on failure 273 */ 274 int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page, 275 unsigned int len, unsigned int offs, 276 u64 lblk_num) 277 { 278 if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) 279 return -EOPNOTSUPP; 280 return fscrypt_crypt_data_unit(fscrypt_get_inode_info_raw(inode), 281 FS_DECRYPT, lblk_num, page, page, len, 282 offs); 283 } 284 EXPORT_SYMBOL(fscrypt_decrypt_block_inplace); 285 286 /** 287 * fscrypt_initialize() - allocate major buffers for fs encryption. 288 * @sb: the filesystem superblock 289 * 290 * We only call this when we start accessing encrypted files, since it 291 * results in memory getting allocated that wouldn't otherwise be used. 292 * 293 * Return: 0 on success; -errno on failure 294 */ 295 int fscrypt_initialize(struct super_block *sb) 296 { 297 mempool_t *pool; 298 299 /* pairs with smp_store_release() below */ 300 if (smp_load_acquire(&fscrypt_bounce_page_pool)) 301 return 0; 302 303 /* No need to allocate a bounce page pool if this FS won't use it. */ 304 if (!sb->s_cop->needs_bounce_pages) 305 return 0; 306 307 guard(mutex)(&fscrypt_init_mutex); 308 if (fscrypt_bounce_page_pool) 309 return 0; 310 311 pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0); 312 if (!pool) 313 return -ENOMEM; 314 /* pairs with smp_load_acquire() above */ 315 smp_store_release(&fscrypt_bounce_page_pool, pool); 316 return 0; 317 } 318 319 void fscrypt_msg(const struct inode *inode, const char *level, 320 const char *fmt, ...) 321 { 322 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, 323 DEFAULT_RATELIMIT_BURST); 324 struct va_format vaf; 325 va_list args; 326 327 if (!__ratelimit(&rs)) 328 return; 329 330 va_start(args, fmt); 331 vaf.fmt = fmt; 332 vaf.va = &args; 333 if (inode && inode->i_ino) 334 printk("%sfscrypt (%s, inode %llu): %pV\n", 335 level, inode->i_sb->s_id, inode->i_ino, &vaf); 336 else if (inode) 337 printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf); 338 else 339 printk("%sfscrypt: %pV\n", level, &vaf); 340 va_end(args); 341 } 342 343 static int __init fscrypt_init(void) 344 { 345 fscrypt_inode_info_cachep = KMEM_CACHE(fscrypt_inode_info, 346 SLAB_RECLAIM_ACCOUNT | 347 SLAB_PANIC); 348 fscrypt_init_keyring(); 349 return 0; 350 } 351 late_initcall(fscrypt_init) 352