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1// SPDX-License-Identifier: GPL-2.02/*3 * Inline encryption support for fscrypt4 *5 * Copyright 2019 Google LLC6 */7 8/*9 * With "inline encryption", the block layer handles the decryption/encryption10 * as part of the bio, instead of the filesystem doing the crypto itself via11 * crypto API. See Documentation/block/inline-encryption.rst. fscrypt still12 * 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#include <linux/uio.h>21 22#include "fscrypt_private.h"23 24static struct block_device **fscrypt_get_devices(struct super_block *sb,25 unsigned int *num_devs)26{27 struct block_device **devs;28 29 if (sb->s_cop->get_devices) {30 devs = sb->s_cop->get_devices(sb, num_devs);31 if (devs)32 return devs;33 }34 devs = kmalloc(sizeof(*devs), GFP_KERNEL);35 if (!devs)36 return ERR_PTR(-ENOMEM);37 devs[0] = sb->s_bdev;38 *num_devs = 1;39 return devs;40}41 42static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_inode_info *ci)43{44 const struct super_block *sb = ci->ci_inode->i_sb;45 unsigned int flags = fscrypt_policy_flags(&ci->ci_policy);46 int dun_bits;47 48 if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)49 return offsetofend(union fscrypt_iv, nonce);50 51 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64)52 return sizeof(__le64);53 54 if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)55 return sizeof(__le32);56 57 /* Default case: IVs are just the file data unit index */58 dun_bits = fscrypt_max_file_dun_bits(sb, ci->ci_data_unit_bits);59 return DIV_ROUND_UP(dun_bits, 8);60}61 62/*63 * Log a message when starting to use blk-crypto (native) or blk-crypto-fallback64 * for an encryption mode for the first time. This is the blk-crypto65 * counterpart to the message logged when starting to use the crypto API for the66 * first time. A limitation is that these messages don't convey which specific67 * filesystems or files are using each implementation. However, *usually*68 * systems use just one implementation per mode, which makes these messages69 * helpful for debugging problems where the "wrong" implementation is used.70 */71static void fscrypt_log_blk_crypto_impl(struct fscrypt_mode *mode,72 struct block_device **devs,73 unsigned int num_devs,74 const struct blk_crypto_config *cfg)75{76 unsigned int i;77 78 for (i = 0; i < num_devs; i++) {79 if (!IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||80 blk_crypto_config_supported_natively(devs[i], cfg)) {81 if (!xchg(&mode->logged_blk_crypto_native, 1))82 pr_info("fscrypt: %s using blk-crypto (native)\n",83 mode->friendly_name);84 } else if (!xchg(&mode->logged_blk_crypto_fallback, 1)) {85 pr_info("fscrypt: %s using blk-crypto-fallback\n",86 mode->friendly_name);87 }88 }89}90 91/* Enable inline encryption for this file if supported. */92int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci)93{94 const struct inode *inode = ci->ci_inode;95 struct super_block *sb = inode->i_sb;96 struct blk_crypto_config crypto_cfg;97 struct block_device **devs;98 unsigned int num_devs;99 unsigned int i;100 101 /* The file must need contents encryption, not filenames encryption */102 if (!S_ISREG(inode->i_mode))103 return 0;104 105 /* The crypto mode must have a blk-crypto counterpart */106 if (ci->ci_mode->blk_crypto_mode == BLK_ENCRYPTION_MODE_INVALID)107 return 0;108 109 /* The filesystem must be mounted with -o inlinecrypt */110 if (!(sb->s_flags & SB_INLINECRYPT))111 return 0;112 113 /*114 * When a page contains multiple logically contiguous filesystem blocks,115 * some filesystem code only calls fscrypt_mergeable_bio() for the first116 * block in the page. This is fine for most of fscrypt's IV generation117 * strategies, where contiguous blocks imply contiguous IVs. But it118 * doesn't work with IV_INO_LBLK_32. For now, simply exclude119 * IV_INO_LBLK_32 with blocksize != PAGE_SIZE from inline encryption.120 */121 if ((fscrypt_policy_flags(&ci->ci_policy) &122 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) &&123 sb->s_blocksize != PAGE_SIZE)124 return 0;125 126 /*127 * On all the filesystem's block devices, blk-crypto must support the128 * crypto configuration that the file would use.129 */130 crypto_cfg.crypto_mode = ci->ci_mode->blk_crypto_mode;131 crypto_cfg.data_unit_size = 1U << ci->ci_data_unit_bits;132 crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci);133 134 devs = fscrypt_get_devices(sb, &num_devs);135 if (IS_ERR(devs))136 return PTR_ERR(devs);137 138 for (i = 0; i < num_devs; i++) {139 if (!blk_crypto_config_supported(devs[i], &crypto_cfg))140 goto out_free_devs;141 }142 143 fscrypt_log_blk_crypto_impl(ci->ci_mode, devs, num_devs, &crypto_cfg);144 145 ci->ci_inlinecrypt = true;146out_free_devs:147 kfree(devs);148 149 return 0;150}151 152int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,153 const u8 *raw_key,154 const struct fscrypt_inode_info *ci)155{156 const struct inode *inode = ci->ci_inode;157 struct super_block *sb = inode->i_sb;158 enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_mode;159 struct blk_crypto_key *blk_key;160 struct block_device **devs;161 unsigned int num_devs;162 unsigned int i;163 int err;164 165 blk_key = kmalloc(sizeof(*blk_key), GFP_KERNEL);166 if (!blk_key)167 return -ENOMEM;168 169 err = blk_crypto_init_key(blk_key, raw_key, crypto_mode,170 fscrypt_get_dun_bytes(ci),171 1U << ci->ci_data_unit_bits);172 if (err) {173 fscrypt_err(inode, "error %d initializing blk-crypto key", err);174 goto fail;175 }176 177 /* Start using blk-crypto on all the filesystem's block devices. */178 devs = fscrypt_get_devices(sb, &num_devs);179 if (IS_ERR(devs)) {180 err = PTR_ERR(devs);181 goto fail;182 }183 for (i = 0; i < num_devs; i++) {184 err = blk_crypto_start_using_key(devs[i], blk_key);185 if (err)186 break;187 }188 kfree(devs);189 if (err) {190 fscrypt_err(inode, "error %d starting to use blk-crypto", err);191 goto fail;192 }193 194 /*195 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared().196 * I.e., here we publish ->blk_key with a RELEASE barrier so that197 * concurrent tasks can ACQUIRE it. Note that this concurrency is only198 * possible for per-mode keys, not for per-file keys.199 */200 smp_store_release(&prep_key->blk_key, blk_key);201 return 0;202 203fail:204 kfree_sensitive(blk_key);205 return err;206}207 208void fscrypt_destroy_inline_crypt_key(struct super_block *sb,209 struct fscrypt_prepared_key *prep_key)210{211 struct blk_crypto_key *blk_key = prep_key->blk_key;212 struct block_device **devs;213 unsigned int num_devs;214 unsigned int i;215 216 if (!blk_key)217 return;218 219 /* Evict the key from all the filesystem's block devices. */220 devs = fscrypt_get_devices(sb, &num_devs);221 if (!IS_ERR(devs)) {222 for (i = 0; i < num_devs; i++)223 blk_crypto_evict_key(devs[i], blk_key);224 kfree(devs);225 }226 kfree_sensitive(blk_key);227}228 229bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode)230{231 return inode->i_crypt_info->ci_inlinecrypt;232}233EXPORT_SYMBOL_GPL(__fscrypt_inode_uses_inline_crypto);234 235static void fscrypt_generate_dun(const struct fscrypt_inode_info *ci,236 u64 lblk_num,237 u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE])238{239 u64 index = lblk_num << ci->ci_data_units_per_block_bits;240 union fscrypt_iv iv;241 int i;242 243 fscrypt_generate_iv(&iv, index, ci);244 245 BUILD_BUG_ON(FSCRYPT_MAX_IV_SIZE > BLK_CRYPTO_MAX_IV_SIZE);246 memset(dun, 0, BLK_CRYPTO_MAX_IV_SIZE);247 for (i = 0; i < ci->ci_mode->ivsize/sizeof(dun[0]); i++)248 dun[i] = le64_to_cpu(iv.dun[i]);249}250 251/**252 * fscrypt_set_bio_crypt_ctx() - prepare a file contents bio for inline crypto253 * @bio: a bio which will eventually be submitted to the file254 * @inode: the file's inode255 * @first_lblk: the first file logical block number in the I/O256 * @gfp_mask: memory allocation flags - these must be a waiting mask so that257 * bio_crypt_set_ctx can't fail.258 *259 * If the contents of the file should be encrypted (or decrypted) with inline260 * encryption, then assign the appropriate encryption context to the bio.261 *262 * Normally the bio should be newly allocated (i.e. no pages added yet), as263 * otherwise fscrypt_mergeable_bio() won't work as intended.264 *265 * The encryption context will be freed automatically when the bio is freed.266 */267void fscrypt_set_bio_crypt_ctx(struct bio *bio, const struct inode *inode,268 u64 first_lblk, gfp_t gfp_mask)269{270 const struct fscrypt_inode_info *ci;271 u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];272 273 if (!fscrypt_inode_uses_inline_crypto(inode))274 return;275 ci = inode->i_crypt_info;276 277 fscrypt_generate_dun(ci, first_lblk, dun);278 bio_crypt_set_ctx(bio, ci->ci_enc_key.blk_key, dun, gfp_mask);279}280EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx);281 282/* Extract the inode and logical block number from a buffer_head. */283static bool bh_get_inode_and_lblk_num(const struct buffer_head *bh,284 const struct inode **inode_ret,285 u64 *lblk_num_ret)286{287 struct folio *folio = bh->b_folio;288 const struct address_space *mapping;289 const struct inode *inode;290 291 /*292 * The ext4 journal (jbd2) can submit a buffer_head it directly created293 * for a non-pagecache page. fscrypt doesn't care about these.294 */295 mapping = folio_mapping(folio);296 if (!mapping)297 return false;298 inode = mapping->host;299 300 *inode_ret = inode;301 *lblk_num_ret = ((u64)folio->index << (PAGE_SHIFT - inode->i_blkbits)) +302 (bh_offset(bh) >> inode->i_blkbits);303 return true;304}305 306/**307 * fscrypt_set_bio_crypt_ctx_bh() - prepare a file contents bio for inline308 * crypto309 * @bio: a bio which will eventually be submitted to the file310 * @first_bh: the first buffer_head for which I/O will be submitted311 * @gfp_mask: memory allocation flags312 *313 * Same as fscrypt_set_bio_crypt_ctx(), except this takes a buffer_head instead314 * of an inode and block number directly.315 */316void fscrypt_set_bio_crypt_ctx_bh(struct bio *bio,317 const struct buffer_head *first_bh,318 gfp_t gfp_mask)319{320 const struct inode *inode;321 u64 first_lblk;322 323 if (bh_get_inode_and_lblk_num(first_bh, &inode, &first_lblk))324 fscrypt_set_bio_crypt_ctx(bio, inode, first_lblk, gfp_mask);325}326EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx_bh);327 328/**329 * fscrypt_mergeable_bio() - test whether data can be added to a bio330 * @bio: the bio being built up331 * @inode: the inode for the next part of the I/O332 * @next_lblk: the next file logical block number in the I/O333 *334 * When building a bio which may contain data which should undergo inline335 * encryption (or decryption) via fscrypt, filesystems should call this function336 * to ensure that the resulting bio contains only contiguous data unit numbers.337 * This will return false if the next part of the I/O cannot be merged with the338 * bio because either the encryption key would be different or the encryption339 * data unit numbers would be discontiguous.340 *341 * fscrypt_set_bio_crypt_ctx() must have already been called on the bio.342 *343 * This function isn't required in cases where crypto-mergeability is ensured in344 * another way, such as I/O targeting only a single file (and thus a single key)345 * combined with fscrypt_limit_io_blocks() to ensure DUN contiguity.346 *347 * Return: true iff the I/O is mergeable348 */349bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode,350 u64 next_lblk)351{352 const struct bio_crypt_ctx *bc = bio->bi_crypt_context;353 u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];354 355 if (!!bc != fscrypt_inode_uses_inline_crypto(inode))356 return false;357 if (!bc)358 return true;359 360 /*361 * Comparing the key pointers is good enough, as all I/O for each key362 * uses the same pointer. I.e., there's currently no need to support363 * merging requests where the keys are the same but the pointers differ.364 */365 if (bc->bc_key != inode->i_crypt_info->ci_enc_key.blk_key)366 return false;367 368 fscrypt_generate_dun(inode->i_crypt_info, next_lblk, next_dun);369 return bio_crypt_dun_is_contiguous(bc, bio->bi_iter.bi_size, next_dun);370}371EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio);372 373/**374 * fscrypt_mergeable_bio_bh() - test whether data can be added to a bio375 * @bio: the bio being built up376 * @next_bh: the next buffer_head for which I/O will be submitted377 *378 * Same as fscrypt_mergeable_bio(), except this takes a buffer_head instead of379 * an inode and block number directly.380 *381 * Return: true iff the I/O is mergeable382 */383bool fscrypt_mergeable_bio_bh(struct bio *bio,384 const struct buffer_head *next_bh)385{386 const struct inode *inode;387 u64 next_lblk;388 389 if (!bh_get_inode_and_lblk_num(next_bh, &inode, &next_lblk))390 return !bio->bi_crypt_context;391 392 return fscrypt_mergeable_bio(bio, inode, next_lblk);393}394EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh);395 396/**397 * fscrypt_dio_supported() - check whether DIO (direct I/O) is supported on an398 * inode, as far as encryption is concerned399 * @inode: the inode in question400 *401 * Return: %true if there are no encryption constraints that prevent DIO from402 * being supported; %false if DIO is unsupported. (Note that in the403 * %true case, the filesystem might have other, non-encryption-related404 * constraints that prevent DIO from actually being supported. Also, on405 * encrypted files the filesystem is still responsible for only allowing406 * DIO when requests are filesystem-block-aligned.)407 */408bool fscrypt_dio_supported(struct inode *inode)409{410 int err;411 412 /* If the file is unencrypted, no veto from us. */413 if (!fscrypt_needs_contents_encryption(inode))414 return true;415 416 /*417 * We only support DIO with inline crypto, not fs-layer crypto.418 *419 * To determine whether the inode is using inline crypto, we have to set420 * up the key if it wasn't already done. This is because in the current421 * design of fscrypt, the decision of whether to use inline crypto or422 * not isn't made until the inode's encryption key is being set up. In423 * the DIO read/write case, the key will always be set up already, since424 * the file will be open. But in the case of statx(), the key might not425 * be set up yet, as the file might not have been opened yet.426 */427 err = fscrypt_require_key(inode);428 if (err) {429 /*430 * Key unavailable or couldn't be set up. This edge case isn't431 * worth worrying about; just report that DIO is unsupported.432 */433 return false;434 }435 return fscrypt_inode_uses_inline_crypto(inode);436}437EXPORT_SYMBOL_GPL(fscrypt_dio_supported);438 439/**440 * fscrypt_limit_io_blocks() - limit I/O blocks to avoid discontiguous DUNs441 * @inode: the file on which I/O is being done442 * @lblk: the block at which the I/O is being started from443 * @nr_blocks: the number of blocks we want to submit starting at @lblk444 *445 * Determine the limit to the number of blocks that can be submitted in a bio446 * targeting @lblk without causing a data unit number (DUN) discontiguity.447 *448 * This is normally just @nr_blocks, as normally the DUNs just increment along449 * with the logical blocks. (Or the file is not encrypted.)450 *451 * In rare cases, fscrypt can be using an IV generation method that allows the452 * DUN to wrap around within logically contiguous blocks, and that wraparound453 * will occur. If this happens, a value less than @nr_blocks will be returned454 * so that the wraparound doesn't occur in the middle of a bio, which would455 * cause encryption/decryption to produce wrong results.456 *457 * Return: the actual number of blocks that can be submitted458 */459u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, u64 nr_blocks)460{461 const struct fscrypt_inode_info *ci;462 u32 dun;463 464 if (!fscrypt_inode_uses_inline_crypto(inode))465 return nr_blocks;466 467 if (nr_blocks <= 1)468 return nr_blocks;469 470 ci = inode->i_crypt_info;471 if (!(fscrypt_policy_flags(&ci->ci_policy) &472 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))473 return nr_blocks;474 475 /* With IV_INO_LBLK_32, the DUN can wrap around from U32_MAX to 0. */476 477 dun = ci->ci_hashed_ino + lblk;478 479 return min_t(u64, nr_blocks, (u64)U32_MAX + 1 - dun);480}481EXPORT_SYMBOL_GPL(fscrypt_limit_io_blocks);482