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-rw-r--r--fs/crypto/inline_crypt.c479
1 files changed, 479 insertions, 0 deletions
diff --git a/fs/crypto/inline_crypt.c b/fs/crypto/inline_crypt.c
new file mode 100644
index 0000000000..8bfb3ce864
--- /dev/null
+++ b/fs/crypto/inline_crypt.c
@@ -0,0 +1,479 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Inline encryption support for fscrypt
+ *
+ * Copyright 2019 Google LLC
+ */
+
+/*
+ * With "inline encryption", the block layer handles the decryption/encryption
+ * as part of the bio, instead of the filesystem doing the crypto itself via
+ * crypto API. See Documentation/block/inline-encryption.rst. fscrypt still
+ * provides the key and IV to use.
+ */
+
+#include <linux/blk-crypto.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>
+#include <linux/sched/mm.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+
+#include "fscrypt_private.h"
+
+static struct block_device **fscrypt_get_devices(struct super_block *sb,
+ unsigned int *num_devs)
+{
+ struct block_device **devs;
+
+ if (sb->s_cop->get_devices) {
+ devs = sb->s_cop->get_devices(sb, num_devs);
+ if (devs)
+ return devs;
+ }
+ devs = kmalloc(sizeof(*devs), GFP_KERNEL);
+ if (!devs)
+ return ERR_PTR(-ENOMEM);
+ devs[0] = sb->s_bdev;
+ *num_devs = 1;
+ return devs;
+}
+
+static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_info *ci)
+{
+ struct super_block *sb = ci->ci_inode->i_sb;
+ unsigned int flags = fscrypt_policy_flags(&ci->ci_policy);
+ int ino_bits = 64, lblk_bits = 64;
+
+ if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)
+ return offsetofend(union fscrypt_iv, nonce);
+
+ if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64)
+ return sizeof(__le64);
+
+ if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)
+ return sizeof(__le32);
+
+ /* Default case: IVs are just the file logical block number */
+ if (sb->s_cop->get_ino_and_lblk_bits)
+ sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits);
+ return DIV_ROUND_UP(lblk_bits, 8);
+}
+
+/*
+ * Log a message when starting to use blk-crypto (native) or blk-crypto-fallback
+ * for an encryption mode for the first time. This is the blk-crypto
+ * counterpart to the message logged when starting to use the crypto API for the
+ * first time. A limitation is that these messages don't convey which specific
+ * filesystems or files are using each implementation. However, *usually*
+ * systems use just one implementation per mode, which makes these messages
+ * helpful for debugging problems where the "wrong" implementation is used.
+ */
+static void fscrypt_log_blk_crypto_impl(struct fscrypt_mode *mode,
+ struct block_device **devs,
+ unsigned int num_devs,
+ const struct blk_crypto_config *cfg)
+{
+ unsigned int i;
+
+ for (i = 0; i < num_devs; i++) {
+ if (!IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) ||
+ blk_crypto_config_supported_natively(devs[i], cfg)) {
+ if (!xchg(&mode->logged_blk_crypto_native, 1))
+ pr_info("fscrypt: %s using blk-crypto (native)\n",
+ mode->friendly_name);
+ } else if (!xchg(&mode->logged_blk_crypto_fallback, 1)) {
+ pr_info("fscrypt: %s using blk-crypto-fallback\n",
+ mode->friendly_name);
+ }
+ }
+}
+
+/* Enable inline encryption for this file if supported. */
+int fscrypt_select_encryption_impl(struct fscrypt_info *ci)
+{
+ const struct inode *inode = ci->ci_inode;
+ struct super_block *sb = inode->i_sb;
+ struct blk_crypto_config crypto_cfg;
+ struct block_device **devs;
+ unsigned int num_devs;
+ unsigned int i;
+
+ /* The file must need contents encryption, not filenames encryption */
+ if (!S_ISREG(inode->i_mode))
+ return 0;
+
+ /* The crypto mode must have a blk-crypto counterpart */
+ if (ci->ci_mode->blk_crypto_mode == BLK_ENCRYPTION_MODE_INVALID)
+ return 0;
+
+ /* The filesystem must be mounted with -o inlinecrypt */
+ if (!(sb->s_flags & SB_INLINECRYPT))
+ return 0;
+
+ /*
+ * When a page contains multiple logically contiguous filesystem blocks,
+ * some filesystem code only calls fscrypt_mergeable_bio() for the first
+ * block in the page. This is fine for most of fscrypt's IV generation
+ * strategies, where contiguous blocks imply contiguous IVs. But it
+ * doesn't work with IV_INO_LBLK_32. For now, simply exclude
+ * IV_INO_LBLK_32 with blocksize != PAGE_SIZE from inline encryption.
+ */
+ if ((fscrypt_policy_flags(&ci->ci_policy) &
+ FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) &&
+ sb->s_blocksize != PAGE_SIZE)
+ return 0;
+
+ /*
+ * On all the filesystem's block devices, blk-crypto must support the
+ * crypto configuration that the file would use.
+ */
+ crypto_cfg.crypto_mode = ci->ci_mode->blk_crypto_mode;
+ crypto_cfg.data_unit_size = sb->s_blocksize;
+ crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci);
+
+ devs = fscrypt_get_devices(sb, &num_devs);
+ if (IS_ERR(devs))
+ return PTR_ERR(devs);
+
+ for (i = 0; i < num_devs; i++) {
+ if (!blk_crypto_config_supported(devs[i], &crypto_cfg))
+ goto out_free_devs;
+ }
+
+ fscrypt_log_blk_crypto_impl(ci->ci_mode, devs, num_devs, &crypto_cfg);
+
+ ci->ci_inlinecrypt = true;
+out_free_devs:
+ kfree(devs);
+
+ return 0;
+}
+
+int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
+ const u8 *raw_key,
+ const struct fscrypt_info *ci)
+{
+ const struct inode *inode = ci->ci_inode;
+ struct super_block *sb = inode->i_sb;
+ enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_mode;
+ struct blk_crypto_key *blk_key;
+ struct block_device **devs;
+ unsigned int num_devs;
+ unsigned int i;
+ int err;
+
+ blk_key = kmalloc(sizeof(*blk_key), GFP_KERNEL);
+ if (!blk_key)
+ return -ENOMEM;
+
+ err = blk_crypto_init_key(blk_key, raw_key, crypto_mode,
+ fscrypt_get_dun_bytes(ci), sb->s_blocksize);
+ if (err) {
+ fscrypt_err(inode, "error %d initializing blk-crypto key", err);
+ goto fail;
+ }
+
+ /* Start using blk-crypto on all the filesystem's block devices. */
+ devs = fscrypt_get_devices(sb, &num_devs);
+ if (IS_ERR(devs)) {
+ err = PTR_ERR(devs);
+ goto fail;
+ }
+ for (i = 0; i < num_devs; i++) {
+ err = blk_crypto_start_using_key(devs[i], blk_key);
+ if (err)
+ break;
+ }
+ kfree(devs);
+ if (err) {
+ fscrypt_err(inode, "error %d starting to use blk-crypto", err);
+ goto fail;
+ }
+
+ /*
+ * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared().
+ * I.e., here we publish ->blk_key with a RELEASE barrier so that
+ * concurrent tasks can ACQUIRE it. Note that this concurrency is only
+ * possible for per-mode keys, not for per-file keys.
+ */
+ smp_store_release(&prep_key->blk_key, blk_key);
+ return 0;
+
+fail:
+ kfree_sensitive(blk_key);
+ return err;
+}
+
+void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
+ struct fscrypt_prepared_key *prep_key)
+{
+ struct blk_crypto_key *blk_key = prep_key->blk_key;
+ struct block_device **devs;
+ unsigned int num_devs;
+ unsigned int i;
+
+ if (!blk_key)
+ return;
+
+ /* Evict the key from all the filesystem's block devices. */
+ devs = fscrypt_get_devices(sb, &num_devs);
+ if (!IS_ERR(devs)) {
+ for (i = 0; i < num_devs; i++)
+ blk_crypto_evict_key(devs[i], blk_key);
+ kfree(devs);
+ }
+ kfree_sensitive(blk_key);
+}
+
+bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode)
+{
+ return inode->i_crypt_info->ci_inlinecrypt;
+}
+EXPORT_SYMBOL_GPL(__fscrypt_inode_uses_inline_crypto);
+
+static void fscrypt_generate_dun(const struct fscrypt_info *ci, u64 lblk_num,
+ u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
+{
+ union fscrypt_iv iv;
+ int i;
+
+ fscrypt_generate_iv(&iv, lblk_num, ci);
+
+ BUILD_BUG_ON(FSCRYPT_MAX_IV_SIZE > BLK_CRYPTO_MAX_IV_SIZE);
+ memset(dun, 0, BLK_CRYPTO_MAX_IV_SIZE);
+ for (i = 0; i < ci->ci_mode->ivsize/sizeof(dun[0]); i++)
+ dun[i] = le64_to_cpu(iv.dun[i]);
+}
+
+/**
+ * fscrypt_set_bio_crypt_ctx() - prepare a file contents bio for inline crypto
+ * @bio: a bio which will eventually be submitted to the file
+ * @inode: the file's inode
+ * @first_lblk: the first file logical block number in the I/O
+ * @gfp_mask: memory allocation flags - these must be a waiting mask so that
+ * bio_crypt_set_ctx can't fail.
+ *
+ * If the contents of the file should be encrypted (or decrypted) with inline
+ * encryption, then assign the appropriate encryption context to the bio.
+ *
+ * Normally the bio should be newly allocated (i.e. no pages added yet), as
+ * otherwise fscrypt_mergeable_bio() won't work as intended.
+ *
+ * The encryption context will be freed automatically when the bio is freed.
+ */
+void fscrypt_set_bio_crypt_ctx(struct bio *bio, const struct inode *inode,
+ u64 first_lblk, gfp_t gfp_mask)
+{
+ const struct fscrypt_info *ci;
+ u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
+
+ if (!fscrypt_inode_uses_inline_crypto(inode))
+ return;
+ ci = inode->i_crypt_info;
+
+ fscrypt_generate_dun(ci, first_lblk, dun);
+ bio_crypt_set_ctx(bio, ci->ci_enc_key.blk_key, dun, gfp_mask);
+}
+EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx);
+
+/* Extract the inode and logical block number from a buffer_head. */
+static bool bh_get_inode_and_lblk_num(const struct buffer_head *bh,
+ const struct inode **inode_ret,
+ u64 *lblk_num_ret)
+{
+ struct page *page = bh->b_page;
+ const struct address_space *mapping;
+ const struct inode *inode;
+
+ /*
+ * The ext4 journal (jbd2) can submit a buffer_head it directly created
+ * for a non-pagecache page. fscrypt doesn't care about these.
+ */
+ mapping = page_mapping(page);
+ if (!mapping)
+ return false;
+ inode = mapping->host;
+
+ *inode_ret = inode;
+ *lblk_num_ret = ((u64)page->index << (PAGE_SHIFT - inode->i_blkbits)) +
+ (bh_offset(bh) >> inode->i_blkbits);
+ return true;
+}
+
+/**
+ * fscrypt_set_bio_crypt_ctx_bh() - prepare a file contents bio for inline
+ * crypto
+ * @bio: a bio which will eventually be submitted to the file
+ * @first_bh: the first buffer_head for which I/O will be submitted
+ * @gfp_mask: memory allocation flags
+ *
+ * Same as fscrypt_set_bio_crypt_ctx(), except this takes a buffer_head instead
+ * of an inode and block number directly.
+ */
+void fscrypt_set_bio_crypt_ctx_bh(struct bio *bio,
+ const struct buffer_head *first_bh,
+ gfp_t gfp_mask)
+{
+ const struct inode *inode;
+ u64 first_lblk;
+
+ if (bh_get_inode_and_lblk_num(first_bh, &inode, &first_lblk))
+ fscrypt_set_bio_crypt_ctx(bio, inode, first_lblk, gfp_mask);
+}
+EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx_bh);
+
+/**
+ * fscrypt_mergeable_bio() - test whether data can be added to a bio
+ * @bio: the bio being built up
+ * @inode: the inode for the next part of the I/O
+ * @next_lblk: the next file logical block number in the I/O
+ *
+ * When building a bio which may contain data which should undergo inline
+ * encryption (or decryption) via fscrypt, filesystems should call this function
+ * to ensure that the resulting bio contains only contiguous data unit numbers.
+ * This will return false if the next part of the I/O cannot be merged with the
+ * bio because either the encryption key would be different or the encryption
+ * data unit numbers would be discontiguous.
+ *
+ * fscrypt_set_bio_crypt_ctx() must have already been called on the bio.
+ *
+ * This function isn't required in cases where crypto-mergeability is ensured in
+ * another way, such as I/O targeting only a single file (and thus a single key)
+ * combined with fscrypt_limit_io_blocks() to ensure DUN contiguity.
+ *
+ * Return: true iff the I/O is mergeable
+ */
+bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode,
+ u64 next_lblk)
+{
+ const struct bio_crypt_ctx *bc = bio->bi_crypt_context;
+ u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
+
+ if (!!bc != fscrypt_inode_uses_inline_crypto(inode))
+ return false;
+ if (!bc)
+ return true;
+
+ /*
+ * Comparing the key pointers is good enough, as all I/O for each key
+ * uses the same pointer. I.e., there's currently no need to support
+ * merging requests where the keys are the same but the pointers differ.
+ */
+ if (bc->bc_key != inode->i_crypt_info->ci_enc_key.blk_key)
+ return false;
+
+ fscrypt_generate_dun(inode->i_crypt_info, next_lblk, next_dun);
+ return bio_crypt_dun_is_contiguous(bc, bio->bi_iter.bi_size, next_dun);
+}
+EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio);
+
+/**
+ * fscrypt_mergeable_bio_bh() - test whether data can be added to a bio
+ * @bio: the bio being built up
+ * @next_bh: the next buffer_head for which I/O will be submitted
+ *
+ * Same as fscrypt_mergeable_bio(), except this takes a buffer_head instead of
+ * an inode and block number directly.
+ *
+ * Return: true iff the I/O is mergeable
+ */
+bool fscrypt_mergeable_bio_bh(struct bio *bio,
+ const struct buffer_head *next_bh)
+{
+ const struct inode *inode;
+ u64 next_lblk;
+
+ if (!bh_get_inode_and_lblk_num(next_bh, &inode, &next_lblk))
+ return !bio->bi_crypt_context;
+
+ return fscrypt_mergeable_bio(bio, inode, next_lblk);
+}
+EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh);
+
+/**
+ * fscrypt_dio_supported() - check whether DIO (direct I/O) is supported on an
+ * inode, as far as encryption is concerned
+ * @inode: the inode in question
+ *
+ * Return: %true if there are no encryption constraints that prevent DIO from
+ * being supported; %false if DIO is unsupported. (Note that in the
+ * %true case, the filesystem might have other, non-encryption-related
+ * constraints that prevent DIO from actually being supported. Also, on
+ * encrypted files the filesystem is still responsible for only allowing
+ * DIO when requests are filesystem-block-aligned.)
+ */
+bool fscrypt_dio_supported(struct inode *inode)
+{
+ int err;
+
+ /* If the file is unencrypted, no veto from us. */
+ if (!fscrypt_needs_contents_encryption(inode))
+ return true;
+
+ /*
+ * We only support DIO with inline crypto, not fs-layer crypto.
+ *
+ * To determine whether the inode is using inline crypto, we have to set
+ * up the key if it wasn't already done. This is because in the current
+ * design of fscrypt, the decision of whether to use inline crypto or
+ * not isn't made until the inode's encryption key is being set up. In
+ * the DIO read/write case, the key will always be set up already, since
+ * the file will be open. But in the case of statx(), the key might not
+ * be set up yet, as the file might not have been opened yet.
+ */
+ err = fscrypt_require_key(inode);
+ if (err) {
+ /*
+ * Key unavailable or couldn't be set up. This edge case isn't
+ * worth worrying about; just report that DIO is unsupported.
+ */
+ return false;
+ }
+ return fscrypt_inode_uses_inline_crypto(inode);
+}
+EXPORT_SYMBOL_GPL(fscrypt_dio_supported);
+
+/**
+ * fscrypt_limit_io_blocks() - limit I/O blocks to avoid discontiguous DUNs
+ * @inode: the file on which I/O is being done
+ * @lblk: the block at which the I/O is being started from
+ * @nr_blocks: the number of blocks we want to submit starting at @lblk
+ *
+ * Determine the limit to the number of blocks that can be submitted in a bio
+ * targeting @lblk without causing a data unit number (DUN) discontiguity.
+ *
+ * This is normally just @nr_blocks, as normally the DUNs just increment along
+ * with the logical blocks. (Or the file is not encrypted.)
+ *
+ * In rare cases, fscrypt can be using an IV generation method that allows the
+ * DUN to wrap around within logically contiguous blocks, and that wraparound
+ * will occur. If this happens, a value less than @nr_blocks will be returned
+ * so that the wraparound doesn't occur in the middle of a bio, which would
+ * cause encryption/decryption to produce wrong results.
+ *
+ * Return: the actual number of blocks that can be submitted
+ */
+u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, u64 nr_blocks)
+{
+ const struct fscrypt_info *ci;
+ u32 dun;
+
+ if (!fscrypt_inode_uses_inline_crypto(inode))
+ return nr_blocks;
+
+ if (nr_blocks <= 1)
+ return nr_blocks;
+
+ ci = inode->i_crypt_info;
+ if (!(fscrypt_policy_flags(&ci->ci_policy) &
+ FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))
+ return nr_blocks;
+
+ /* With IV_INO_LBLK_32, the DUN can wrap around from U32_MAX to 0. */
+
+ dun = ci->ci_hashed_ino + lblk;
+
+ return min_t(u64, nr_blocks, (u64)U32_MAX + 1 - dun);
+}
+EXPORT_SYMBOL_GPL(fscrypt_limit_io_blocks);
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