1 files changed, 415 insertions, 0 deletions

diff --git a/fs/crypto/block.c b/fs/crypto/block.c
new file mode 100644
index 000000000000..5193f8ba3ee0
--- /dev/null
+++ b/fs/crypto/block.c
@@ -0,0 +1,415 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * File contents en/decryption on block-based filesystems
+ *
+ * Copyright 2019 Google LLC
+ */
+
+/*
+ * This file implements fscrypt's file contents en/decryption using blk-crypto
+ * (Documentation/block/inline-encryption.rst).  fscrypt assigns a bio_crypt_ctx
+ * with a key and IV to each bio, and the block layer does the en/decryption.
+ *
+ * This file's exported functions are called only by block-based filesystems.
+ */
+
+#include <linux/blk-crypto.h>
+#include <linux/blkdev.h>
+#include <linux/export.h>
+#include <linux/sched/mm.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+
+#include "fscrypt_private.h"
+
+static unsigned int
+fscrypt_get_devices(struct super_block *sb,
+		    struct block_device *devs[FSCRYPT_MAX_DEVICES])
+{
+	if (sb->s_cop->get_devices)
+		return sb->s_cop->get_devices(sb, devs);
+	devs[0] = sb->s_bdev;
+	return 1;
+}
+
+static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_inode_info *ci)
+{
+	const struct super_block *sb = ci->ci_inode->i_sb;
+	unsigned int flags = fscrypt_policy_flags(&ci->ci_policy);
+	int dun_bits;
+
+	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 data unit index */
+	dun_bits = fscrypt_max_file_dun_bits(sb, ci->ci_data_unit_bits);
+	return DIV_ROUND_UP(dun_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 *dev,
+					const struct blk_crypto_key *blk_key)
+{
+	if (blk_crypto_config_supported_natively(dev, &blk_key->crypto_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);
+	}
+}
+
+int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
+				     const u8 *key_bytes, size_t key_size,
+				     bool is_hw_wrapped,
+				     const struct fscrypt_inode_info *ci)
+{
+	const struct inode *inode = ci->ci_inode;
+	struct super_block *sb = inode->i_sb;
+	bool inlinecrypt = sb->s_flags & SB_INLINECRYPT;
+	struct fscrypt_mode *mode = ci->ci_mode;
+	enum blk_crypto_key_type key_type = is_hw_wrapped ?
+		BLK_CRYPTO_KEY_TYPE_HW_WRAPPED : BLK_CRYPTO_KEY_TYPE_RAW;
+	struct blk_crypto_key *blk_key;
+	struct block_device *devs[FSCRYPT_MAX_DEVICES];
+	unsigned int num_devs;
+	unsigned int i;
+	int err;
+
+	if (is_hw_wrapped && !inlinecrypt) {
+		/*
+		 * blk_crypto_init_key() would catch this anyway, but this
+		 * provides a clearer error message.
+		 */
+		fscrypt_err(
+			inode,
+			"Hardware-wrapped keys require inline encryption (-o inlinecrypt)");
+		return -EINVAL;
+	}
+
+	blk_key = kmalloc_obj(*blk_key);
+	if (!blk_key)
+		return -ENOMEM;
+
+	err = blk_crypto_init_key(blk_key, key_bytes, key_size, key_type,
+				  mode->blk_crypto_mode,
+				  fscrypt_get_dun_bytes(ci),
+				  1U << ci->ci_data_unit_bits,
+				  inlinecrypt ? BLK_CRYPTO_CFG_ALLOW_HW : 0);
+	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. */
+	num_devs = fscrypt_get_devices(sb, devs);
+	for (i = 0; i < num_devs; i++) {
+		err = blk_crypto_start_using_key(devs[i], blk_key);
+		if (err)
+			break;
+		fscrypt_log_blk_crypto_impl(mode, devs[i], blk_key);
+	}
+	if (err) {
+		if (err == -EOPNOTSUPP && is_hw_wrapped)
+			fscrypt_err(
+				inode,
+				"Hardware-wrapped key required, but no suitable inline encryption capabilities are available");
+		else
+			fscrypt_err(inode,
+				    "Error %d starting to use blk-crypto", err);
+		goto fail;
+	}
+
+	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[FSCRYPT_MAX_DEVICES];
+	unsigned int num_devs;
+	unsigned int i;
+
+	if (!blk_key)
+		return;
+
+	/*
+	 * Evict the key from all the filesystem's block devices.
+	 * This *must* be done before the key is freed.
+	 */
+	num_devs = fscrypt_get_devices(sb, devs);
+	for (i = 0; i < num_devs; i++)
+		blk_crypto_evict_key(devs[i], blk_key);
+
+	kfree_sensitive(blk_key);
+}
+
+/*
+ * Ask the inline encryption hardware to derive the software secret from a
+ * hardware-wrapped key.  Returns -EOPNOTSUPP if hardware-wrapped keys aren't
+ * supported on this filesystem or hardware.
+ */
+int fscrypt_derive_sw_secret(struct super_block *sb,
+			     const u8 *wrapped_key, size_t wrapped_key_size,
+			     u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE])
+{
+	int err;
+
+	/* The filesystem must be mounted with -o inlinecrypt. */
+	if (!(sb->s_flags & SB_INLINECRYPT)) {
+		fscrypt_warn(NULL,
+			     "%s: filesystem not mounted with inlinecrypt\n",
+			     sb->s_id);
+		return -EOPNOTSUPP;
+	}
+
+	err = blk_crypto_derive_sw_secret(sb->s_bdev, wrapped_key,
+					  wrapped_key_size, sw_secret);
+	if (err == -EOPNOTSUPP)
+		fscrypt_warn(NULL,
+			     "%s: block device doesn't support hardware-wrapped keys\n",
+			     sb->s_id);
+	return err;
+}
+
+static void fscrypt_generate_dun(const struct fscrypt_inode_info *ci,
+				 loff_t pos, u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE])
+{
+	union fscrypt_iv iv;
+	int i;
+
+	fscrypt_generate_iv(&iv, pos >> ci->ci_data_unit_bits, 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
+ * @pos: the first file position (in bytes) 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), 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,
+			       loff_t pos, gfp_t gfp_mask)
+{
+	const struct fscrypt_inode_info *ci;
+	u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
+
+	if (!fscrypt_needs_contents_encryption(inode))
+		return;
+	ci = fscrypt_get_inode_info_raw(inode);
+
+	fscrypt_generate_dun(ci, pos, dun);
+	bio_crypt_set_ctx(bio, ci->ci_enc_key.blk_key, dun, gfp_mask);
+}
+EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx);
+
+/**
+ * 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
+ * @pos: the next file position (in bytes) in the I/O
+ *
+ * When building a bio which may contain data which should undergo 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,
+			   loff_t pos)
+{
+	const struct bio_crypt_ctx *bc = bio->bi_crypt_context;
+	const struct fscrypt_inode_info *ci;
+	u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE];
+
+	if (!!bc != fscrypt_needs_contents_encryption(inode))
+		return false;
+	if (!bc)
+		return true;
+	ci = fscrypt_get_inode_info_raw(inode);
+
+	/*
+	 * 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 != ci->ci_enc_key.blk_key)
+		return false;
+
+	fscrypt_generate_dun(ci, pos, next_dun);
+	return bio_crypt_dun_is_contiguous(bc, bio->bi_iter.bi_size, next_dun);
+}
+EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio);
+
+/**
+ * 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_inode_info *ci;
+	u32 dun;
+
+	if (!fscrypt_needs_contents_encryption(inode))
+		return nr_blocks;
+
+	if (nr_blocks <= 1)
+		return nr_blocks;
+
+	ci = fscrypt_get_inode_info_raw(inode);
+	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);
+
+struct fscrypt_zero_done {
+	atomic_t		pending;
+	blk_status_t		status;
+	struct completion	done;
+};
+
+static void fscrypt_zeroout_range_done(struct fscrypt_zero_done *done)
+{
+	if (atomic_dec_and_test(&done->pending))
+		complete(&done->done);
+}
+
+static void fscrypt_zeroout_range_end_io(struct bio *bio)
+{
+	struct fscrypt_zero_done *done = bio->bi_private;
+
+	if (bio->bi_status)
+		cmpxchg(&done->status, 0, bio->bi_status);
+	fscrypt_zeroout_range_done(done);
+	bio_put(bio);
+}
+
+/**
+ * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
+ * @inode: the file's inode
+ * @pos: the first file position (in bytes) to zero out
+ * @sector: the first sector to zero out
+ * @len: bytes to zero out
+ *
+ * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
+ * ciphertext blocks which decrypt to the all-zeroes block.  The blocks must be
+ * both logically and physically contiguous.  It's also assumed that the
+ * filesystem only uses a single block device, ->s_bdev.  @len must be a
+ * multiple of the file system logical block size.
+ *
+ * Note that since each block uses a different IV, this involves writing a
+ * different ciphertext to each block; we can't simply reuse the same one.
+ *
+ * Return: 0 on success; -errno on failure.
+ */
+int fscrypt_zeroout_range(const struct inode *inode, loff_t pos,
+			  sector_t sector, u64 len)
+{
+	struct fscrypt_zero_done done = {
+		.pending	= ATOMIC_INIT(1),
+		.done		= COMPLETION_INITIALIZER_ONSTACK(done.done),
+	};
+
+	if (len == 0)
+		return 0;
+
+	do {
+		struct bio *bio;
+		unsigned int n;
+
+		bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE,
+				GFP_NOFS);
+		bio->bi_iter.bi_sector = sector;
+		bio->bi_private = &done;
+		bio->bi_end_io = fscrypt_zeroout_range_end_io;
+		fscrypt_set_bio_crypt_ctx(bio, inode, pos, GFP_NOFS);
+
+		for (n = 0; n < BIO_MAX_VECS; n++) {
+			unsigned int bytes_this_page = min(len, PAGE_SIZE);
+
+			__bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
+			len -= bytes_this_page;
+			pos += bytes_this_page;
+			sector += (bytes_this_page >> SECTOR_SHIFT);
+			if (!len || !fscrypt_mergeable_bio(bio, inode, pos))
+				break;
+		}
+
+		atomic_inc(&done.pending);
+		blk_crypto_submit_bio(bio);
+	} while (len);
+
+	fscrypt_zeroout_range_done(&done);
+
+	wait_for_completion(&done.done);
+	return blk_status_to_errno(done.status);
+}
+EXPORT_SYMBOL(fscrypt_zeroout_range);