1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Inline encryption support for fscrypt 4 * 5 * Copyright 2019 Google LLC 6 */ 7 8 /* 9 * With "inline encryption", the block layer handles the decryption/encryption 10 * as part of the bio, instead of the filesystem doing the crypto itself via 11 * crypto API. See Documentation/block/inline-encryption.rst. fscrypt still 12 * provides the key and IV to use. 13 */ 14 15 #include <linux/blk-crypto.h> 16 #include <linux/blkdev.h> 17 #include <linux/buffer_head.h> 18 #include <linux/sched/mm.h> 19 #include <linux/slab.h> 20 21 #include "fscrypt_private.h" 22 23 struct fscrypt_blk_crypto_key { 24 struct blk_crypto_key base; 25 int num_devs; 26 struct request_queue *devs[]; 27 }; 28 29 static int fscrypt_get_num_devices(struct super_block *sb) 30 { 31 if (sb->s_cop->get_num_devices) 32 return sb->s_cop->get_num_devices(sb); 33 return 1; 34 } 35 36 static void fscrypt_get_devices(struct super_block *sb, int num_devs, 37 struct request_queue **devs) 38 { 39 if (num_devs == 1) 40 devs[0] = bdev_get_queue(sb->s_bdev); 41 else 42 sb->s_cop->get_devices(sb, devs); 43 } 44 45 static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_info *ci) 46 { 47 struct super_block *sb = ci->ci_inode->i_sb; 48 unsigned int flags = fscrypt_policy_flags(&ci->ci_policy); 49 int ino_bits = 64, lblk_bits = 64; 50 51 if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) 52 return offsetofend(union fscrypt_iv, nonce); 53 54 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) 55 return sizeof(__le64); 56 57 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) 58 return sizeof(__le32); 59 60 /* Default case: IVs are just the file logical block number */ 61 if (sb->s_cop->get_ino_and_lblk_bits) 62 sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits); 63 return DIV_ROUND_UP(lblk_bits, 8); 64 } 65 66 /* Enable inline encryption for this file if supported. */ 67 int fscrypt_select_encryption_impl(struct fscrypt_info *ci) 68 { 69 const struct inode *inode = ci->ci_inode; 70 struct super_block *sb = inode->i_sb; 71 struct blk_crypto_config crypto_cfg; 72 int num_devs; 73 struct request_queue **devs; 74 int i; 75 76 /* The file must need contents encryption, not filenames encryption */ 77 if (!fscrypt_needs_contents_encryption(inode)) 78 return 0; 79 80 /* The crypto mode must have a blk-crypto counterpart */ 81 if (ci->ci_mode->blk_crypto_mode == BLK_ENCRYPTION_MODE_INVALID) 82 return 0; 83 84 /* The filesystem must be mounted with -o inlinecrypt */ 85 if (!(sb->s_flags & SB_INLINECRYPT)) 86 return 0; 87 88 /* 89 * When a page contains multiple logically contiguous filesystem blocks, 90 * some filesystem code only calls fscrypt_mergeable_bio() for the first 91 * block in the page. This is fine for most of fscrypt's IV generation 92 * strategies, where contiguous blocks imply contiguous IVs. But it 93 * doesn't work with IV_INO_LBLK_32. For now, simply exclude 94 * IV_INO_LBLK_32 with blocksize != PAGE_SIZE from inline encryption. 95 */ 96 if ((fscrypt_policy_flags(&ci->ci_policy) & 97 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) && 98 sb->s_blocksize != PAGE_SIZE) 99 return 0; 100 101 /* 102 * On all the filesystem's devices, blk-crypto must support the crypto 103 * configuration that the file would use. 104 */ 105 crypto_cfg.crypto_mode = ci->ci_mode->blk_crypto_mode; 106 crypto_cfg.data_unit_size = sb->s_blocksize; 107 crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci); 108 num_devs = fscrypt_get_num_devices(sb); 109 devs = kmalloc_array(num_devs, sizeof(*devs), GFP_KERNEL); 110 if (!devs) 111 return -ENOMEM; 112 fscrypt_get_devices(sb, num_devs, devs); 113 114 for (i = 0; i < num_devs; i++) { 115 if (!blk_crypto_config_supported(devs[i], &crypto_cfg)) 116 goto out_free_devs; 117 } 118 119 ci->ci_inlinecrypt = true; 120 out_free_devs: 121 kfree(devs); 122 123 return 0; 124 } 125 126 int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key, 127 const u8 *raw_key, 128 const struct fscrypt_info *ci) 129 { 130 const struct inode *inode = ci->ci_inode; 131 struct super_block *sb = inode->i_sb; 132 enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_mode; 133 int num_devs = fscrypt_get_num_devices(sb); 134 int queue_refs = 0; 135 struct fscrypt_blk_crypto_key *blk_key; 136 int err; 137 int i; 138 139 blk_key = kzalloc(struct_size(blk_key, devs, num_devs), GFP_KERNEL); 140 if (!blk_key) 141 return -ENOMEM; 142 143 blk_key->num_devs = num_devs; 144 fscrypt_get_devices(sb, num_devs, blk_key->devs); 145 146 err = blk_crypto_init_key(&blk_key->base, raw_key, crypto_mode, 147 fscrypt_get_dun_bytes(ci), sb->s_blocksize); 148 if (err) { 149 fscrypt_err(inode, "error %d initializing blk-crypto key", err); 150 goto fail; 151 } 152 153 /* 154 * We have to start using blk-crypto on all the filesystem's devices. 155 * We also have to save all the request_queue's for later so that the 156 * key can be evicted from them. This is needed because some keys 157 * aren't destroyed until after the filesystem was already unmounted 158 * (namely, the per-mode keys in struct fscrypt_master_key). 159 */ 160 for (i = 0; i < num_devs; i++) { 161 if (!blk_get_queue(blk_key->devs[i])) { 162 fscrypt_err(inode, "couldn't get request_queue"); 163 err = -EAGAIN; 164 goto fail; 165 } 166 queue_refs++; 167 168 err = blk_crypto_start_using_key(&blk_key->base, 169 blk_key->devs[i]); 170 if (err) { 171 fscrypt_err(inode, 172 "error %d starting to use blk-crypto", err); 173 goto fail; 174 } 175 } 176 /* 177 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). 178 * I.e., here we publish ->blk_key with a RELEASE barrier so that 179 * concurrent tasks can ACQUIRE it. Note that this concurrency is only 180 * possible for per-mode keys, not for per-file keys. 181 */ 182 smp_store_release(&prep_key->blk_key, blk_key); 183 return 0; 184 185 fail: 186 for (i = 0; i < queue_refs; i++) 187 blk_put_queue(blk_key->devs[i]); 188 kfree_sensitive(blk_key); 189 return err; 190 } 191 192 void fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key) 193 { 194 struct fscrypt_blk_crypto_key *blk_key = prep_key->blk_key; 195 int i; 196 197 if (blk_key) { 198 for (i = 0; i < blk_key->num_devs; i++) { 199 blk_crypto_evict_key(blk_key->devs[i], &blk_key->base); 200 blk_put_queue(blk_key->devs[i]); 201 } 202 kfree_sensitive(blk_key); 203 } 204 } 205 206 bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode) 207 { 208 return inode->i_crypt_info->ci_inlinecrypt; 209 } 210 EXPORT_SYMBOL_GPL(__fscrypt_inode_uses_inline_crypto); 211 212 static void fscrypt_generate_dun(const struct fscrypt_info *ci, u64 lblk_num, 213 u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]) 214 { 215 union fscrypt_iv iv; 216 int i; 217 218 fscrypt_generate_iv(&iv, lblk_num, ci); 219 220 BUILD_BUG_ON(FSCRYPT_MAX_IV_SIZE > BLK_CRYPTO_MAX_IV_SIZE); 221 memset(dun, 0, BLK_CRYPTO_MAX_IV_SIZE); 222 for (i = 0; i < ci->ci_mode->ivsize/sizeof(dun[0]); i++) 223 dun[i] = le64_to_cpu(iv.dun[i]); 224 } 225 226 /** 227 * fscrypt_set_bio_crypt_ctx() - prepare a file contents bio for inline crypto 228 * @bio: a bio which will eventually be submitted to the file 229 * @inode: the file's inode 230 * @first_lblk: the first file logical block number in the I/O 231 * @gfp_mask: memory allocation flags - these must be a waiting mask so that 232 * bio_crypt_set_ctx can't fail. 233 * 234 * If the contents of the file should be encrypted (or decrypted) with inline 235 * encryption, then assign the appropriate encryption context to the bio. 236 * 237 * Normally the bio should be newly allocated (i.e. no pages added yet), as 238 * otherwise fscrypt_mergeable_bio() won't work as intended. 239 * 240 * The encryption context will be freed automatically when the bio is freed. 241 */ 242 void fscrypt_set_bio_crypt_ctx(struct bio *bio, const struct inode *inode, 243 u64 first_lblk, gfp_t gfp_mask) 244 { 245 const struct fscrypt_info *ci; 246 u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; 247 248 if (!fscrypt_inode_uses_inline_crypto(inode)) 249 return; 250 ci = inode->i_crypt_info; 251 252 fscrypt_generate_dun(ci, first_lblk, dun); 253 bio_crypt_set_ctx(bio, &ci->ci_enc_key.blk_key->base, dun, gfp_mask); 254 } 255 EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx); 256 257 /* Extract the inode and logical block number from a buffer_head. */ 258 static bool bh_get_inode_and_lblk_num(const struct buffer_head *bh, 259 const struct inode **inode_ret, 260 u64 *lblk_num_ret) 261 { 262 struct page *page = bh->b_page; 263 const struct address_space *mapping; 264 const struct inode *inode; 265 266 /* 267 * The ext4 journal (jbd2) can submit a buffer_head it directly created 268 * for a non-pagecache page. fscrypt doesn't care about these. 269 */ 270 mapping = page_mapping(page); 271 if (!mapping) 272 return false; 273 inode = mapping->host; 274 275 *inode_ret = inode; 276 *lblk_num_ret = ((u64)page->index << (PAGE_SHIFT - inode->i_blkbits)) + 277 (bh_offset(bh) >> inode->i_blkbits); 278 return true; 279 } 280 281 /** 282 * fscrypt_set_bio_crypt_ctx_bh() - prepare a file contents bio for inline 283 * crypto 284 * @bio: a bio which will eventually be submitted to the file 285 * @first_bh: the first buffer_head for which I/O will be submitted 286 * @gfp_mask: memory allocation flags 287 * 288 * Same as fscrypt_set_bio_crypt_ctx(), except this takes a buffer_head instead 289 * of an inode and block number directly. 290 */ 291 void fscrypt_set_bio_crypt_ctx_bh(struct bio *bio, 292 const struct buffer_head *first_bh, 293 gfp_t gfp_mask) 294 { 295 const struct inode *inode; 296 u64 first_lblk; 297 298 if (bh_get_inode_and_lblk_num(first_bh, &inode, &first_lblk)) 299 fscrypt_set_bio_crypt_ctx(bio, inode, first_lblk, gfp_mask); 300 } 301 EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx_bh); 302 303 /** 304 * fscrypt_mergeable_bio() - test whether data can be added to a bio 305 * @bio: the bio being built up 306 * @inode: the inode for the next part of the I/O 307 * @next_lblk: the next file logical block number in the I/O 308 * 309 * When building a bio which may contain data which should undergo inline 310 * encryption (or decryption) via fscrypt, filesystems should call this function 311 * to ensure that the resulting bio contains only contiguous data unit numbers. 312 * This will return false if the next part of the I/O cannot be merged with the 313 * bio because either the encryption key would be different or the encryption 314 * data unit numbers would be discontiguous. 315 * 316 * fscrypt_set_bio_crypt_ctx() must have already been called on the bio. 317 * 318 * Return: true iff the I/O is mergeable 319 */ 320 bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode, 321 u64 next_lblk) 322 { 323 const struct bio_crypt_ctx *bc = bio->bi_crypt_context; 324 u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; 325 326 if (!!bc != fscrypt_inode_uses_inline_crypto(inode)) 327 return false; 328 if (!bc) 329 return true; 330 331 /* 332 * Comparing the key pointers is good enough, as all I/O for each key 333 * uses the same pointer. I.e., there's currently no need to support 334 * merging requests where the keys are the same but the pointers differ. 335 */ 336 if (bc->bc_key != &inode->i_crypt_info->ci_enc_key.blk_key->base) 337 return false; 338 339 fscrypt_generate_dun(inode->i_crypt_info, next_lblk, next_dun); 340 return bio_crypt_dun_is_contiguous(bc, bio->bi_iter.bi_size, next_dun); 341 } 342 EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio); 343 344 /** 345 * fscrypt_mergeable_bio_bh() - test whether data can be added to a bio 346 * @bio: the bio being built up 347 * @next_bh: the next buffer_head for which I/O will be submitted 348 * 349 * Same as fscrypt_mergeable_bio(), except this takes a buffer_head instead of 350 * an inode and block number directly. 351 * 352 * Return: true iff the I/O is mergeable 353 */ 354 bool fscrypt_mergeable_bio_bh(struct bio *bio, 355 const struct buffer_head *next_bh) 356 { 357 const struct inode *inode; 358 u64 next_lblk; 359 360 if (!bh_get_inode_and_lblk_num(next_bh, &inode, &next_lblk)) 361 return !bio->bi_crypt_context; 362 363 return fscrypt_mergeable_bio(bio, inode, next_lblk); 364 } 365 EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh); 366