From: Eric Biggers <ebiggers@xxxxxxxxxx>
Add a new device-mapper target "dm-default-key" that is similar to
dm-crypt but has two main differences:
- It uses the blk-crypto API instead of the regular crypto API. This
allows it to take advantage of inline encryption hardware such as that
commonly built into UFS host controllers.
- It supports a passthrough flag, which will be used by ext4 and f2fs to
avoid double encryption of encrypted files. In this setup,
dm-default-key provides the "metadata encryption" layer.
The table syntax matches dm-crypt's, but for now only a stripped-down
set of parameters is supported.
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
drivers/md/Kconfig | 20 ++
drivers/md/Makefile | 1 +
drivers/md/dm-default-key.c | 431 ++++++++++++++++++++++++++++++++++++
3 files changed, 452 insertions(+)
create mode 100644 drivers/md/dm-default-key.c
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 1e9db8e4acdf6..a9f35a8efbade 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -268,10 +268,30 @@ config DM_CRYPT
To compile this code as a module, choose M here: the module will
be called dm-crypt.
If unsure, say N.
+config DM_DEFAULT_KEY
+ tristate "Default-key target support"
+ depends on BLK_DEV_DM
+ depends on BLK_INLINE_ENCRYPTION
+ # dm-default-key doesn't require -o inlinecrypt, but it does currently
+ # rely on the inline encryption hooks being built into the kernel.
+ depends on FS_ENCRYPTION_INLINE_CRYPT
+ help
+ This device-mapper target allows you to create a device that
+ assigns a default encryption key to bios that aren't for the
+ contents of an encrypted file.
+
+ This ensures that all blocks on-disk will be encrypted with
+ some key, without the performance hit of file contents being
+ encrypted twice when fscrypt is used.
+
+ It is only appropriate to use dm-default-key when key
+ configuration is tightly controlled such that all fscrypt keys
+ are at least as hard to compromise as the default key.
+
config DM_SNAPSHOT
tristate "Snapshot target"
depends on BLK_DEV_DM
select DM_BUFIO
help
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 476a214e4bdc2..1dc4b20b506db 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -49,10 +49,11 @@ obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o
obj-$(CONFIG_BLK_DEV_DM_BUILTIN) += dm-builtin.o
obj-$(CONFIG_DM_UNSTRIPED) += dm-unstripe.o
obj-$(CONFIG_DM_BUFIO) += dm-bufio.o
obj-$(CONFIG_DM_BIO_PRISON) += dm-bio-prison.o
obj-$(CONFIG_DM_CRYPT) += dm-crypt.o
+obj-$(CONFIG_DM_DEFAULT_KEY) += dm-default-key.o
obj-$(CONFIG_DM_DELAY) += dm-delay.o
obj-$(CONFIG_DM_DUST) += dm-dust.o
obj-$(CONFIG_DM_FLAKEY) += dm-flakey.o
obj-$(CONFIG_DM_MULTIPATH) += dm-multipath.o dm-round-robin.o
obj-$(CONFIG_DM_MULTIPATH_QL) += dm-queue-length.o
diff --git a/drivers/md/dm-default-key.c b/drivers/md/dm-default-key.c
new file mode 100644
index 0000000000000..f5533418b4456
--- /dev/null
+++ b/drivers/md/dm-default-key.c
@@ -0,0 +1,431 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2024 Google LLC
+ */
+
+#include <linux/blk-crypto.h>
+#include <linux/device-mapper.h>
+#include <linux/module.h>
+
+#define DM_MSG_PREFIX "default-key"
+
+static const struct dm_default_key_cipher {
+ const char *name;
+ enum blk_crypto_mode_num mode_num;
+ int key_size;
+} dm_default_key_ciphers[] = {
+ {
+ .name = "aes-xts-plain64",
+ .mode_num = BLK_ENCRYPTION_MODE_AES_256_XTS,
+ .key_size = 64,
+ }, {
+ .name = "xchacha12,aes-adiantum-plain64",
+ .mode_num = BLK_ENCRYPTION_MODE_ADIANTUM,
+ .key_size = 32,
+ },
+};
+
+/**
+ * struct dm_default_c - private data of a default-key target
+ * @dev: the underlying device
+ * @start: starting sector of the range of @dev which this target actually maps.
+ * For this purpose a "sector" is 512 bytes.
+ * @cipher_string: the name of the encryption algorithm being used
+ * @iv_offset: starting offset for IVs. IVs are generated as if the target were
+ * preceded by @iv_offset 512-byte sectors.
+ * @sector_size: crypto sector size in bytes (usually 4096)
+ * @sector_bits: log2(sector_size)
+ * @key: the encryption key to use
+ * @max_dun: the maximum DUN that may be used (computed from other params)
+ */
+struct default_key_c {
+ struct dm_dev *dev;
+ sector_t start;
+ const char *cipher_string;
+ u64 iv_offset;
+ unsigned int sector_size;
+ unsigned int sector_bits;
+ struct blk_crypto_key key;
+ u64 max_dun;
+};
+
+static const struct dm_default_key_cipher *
+lookup_cipher(const char *cipher_string)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(dm_default_key_ciphers); i++) {
+ if (strcmp(cipher_string, dm_default_key_ciphers[i].name) == 0)
+ return &dm_default_key_ciphers[i];
+ }
+ return NULL;
+}
+
+static void default_key_dtr(struct dm_target *ti)
+{
+ struct default_key_c *dkc = ti->private;
+
+ if (dkc->dev) {
+ if (dkc->key.size)
+ blk_crypto_evict_key(dkc->dev->bdev, &dkc->key);
+ dm_put_device(ti, dkc->dev);
+ }
+ kfree_sensitive(dkc->cipher_string);
+ kfree_sensitive(dkc);
+}
+
+static int default_key_ctr_optional(struct dm_target *ti,
+ unsigned int argc, char **argv)
+{
+ struct default_key_c *dkc = ti->private;
+ struct dm_arg_set as;
+ static const struct dm_arg _args[] = {
+ {0, 3, "Invalid number of feature args"},
+ };
+ unsigned int opt_params;
+ const char *opt_string;
+ bool iv_large_sectors = false;
+ char dummy;
+ int err;
+
+ as.argc = argc;
+ as.argv = argv;
+
+ err = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
+ if (err)
+ return err;
+
+ while (opt_params--) {
+ opt_string = dm_shift_arg(&as);
+ if (!opt_string) {
+ ti->error = "Not enough feature arguments";
+ return -EINVAL;
+ }
+ if (!strcmp(opt_string, "allow_discards")) {
+ ti->num_discard_bios = 1;
+ } else if (sscanf(opt_string, "sector_size:%u%c",
+ &dkc->sector_size, &dummy) == 1) {
+ if (dkc->sector_size < SECTOR_SIZE ||
+ dkc->sector_size > 4096 ||
+ !is_power_of_2(dkc->sector_size)) {
+ ti->error = "Invalid sector_size";
+ return -EINVAL;
+ }
+ } else if (!strcmp(opt_string, "iv_large_sectors")) {
+ iv_large_sectors = true;
+ } else {
+ ti->error = "Invalid feature arguments";
+ return -EINVAL;
+ }
+ }
+
+ /* dm-default-key doesn't implement iv_large_sectors=false. */
+ if (dkc->sector_size != SECTOR_SIZE && !iv_large_sectors) {
+ ti->error = "iv_large_sectors must be specified";
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/*
+ * Construct a default-key mapping:
+ * <cipher> <key> <iv_offset> <dev_path> <start>
+ *
+ * This syntax matches dm-crypt's, but the set of supported functionality has
+ * been stripped down.
+ */
+static int default_key_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+ struct default_key_c *dkc;
+ const struct dm_default_key_cipher *cipher;
+ u8 raw_key[BLK_CRYPTO_MAX_KEY_SIZE];
+ unsigned int dun_bytes;
+ unsigned long long tmpll;
+ char dummy;
+ int err;
+
+ if (argc < 5) {
+ ti->error = "Not enough arguments";
+ return -EINVAL;
+ }
+
+ dkc = kzalloc(sizeof(*dkc), GFP_KERNEL);
+ if (!dkc) {
+ ti->error = "Out of memory";
+ return -ENOMEM;
+ }
+ ti->private = dkc;
+
+ /* <cipher> */
+ dkc->cipher_string = kstrdup(argv[0], GFP_KERNEL);
+ if (!dkc->cipher_string) {
+ ti->error = "Out of memory";
+ err = -ENOMEM;
+ goto bad;
+ }
+ cipher = lookup_cipher(dkc->cipher_string);
+ if (!cipher) {
+ ti->error = "Unsupported cipher";
+ err = -EINVAL;
+ goto bad;
+ }
+
+ /* <key> */
+ if (strlen(argv[1]) != 2 * cipher->key_size) {
+ ti->error = "Incorrect key size for cipher";
+ err = -EINVAL;
+ goto bad;
+ }
+ if (hex2bin(raw_key, argv[1], cipher->key_size) != 0) {
+ ti->error = "Malformed key string";
+ err = -EINVAL;
+ goto bad;
+ }
+
+ /* <iv_offset> */
+ if (sscanf(argv[2], "%llu%c", &dkc->iv_offset, &dummy) != 1) {
+ ti->error = "Invalid iv_offset sector";
+ err = -EINVAL;
+ goto bad;
+ }
+
+ /* <dev_path> */
+ err = dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
+ &dkc->dev);
+ if (err) {
+ ti->error = "Device lookup failed";
+ goto bad;
+ }
+
+ /* <start> */
+ if (sscanf(argv[4], "%llu%c", &tmpll, &dummy) != 1 ||
+ tmpll != (sector_t)tmpll) {
+ ti->error = "Invalid start sector";
+ err = -EINVAL;
+ goto bad;
+ }
+ dkc->start = tmpll;
+
+ if (bdev_is_zoned(dkc->dev->bdev)) {
+ /*
+ * dm-default-key needs proper sector numbers because they
+ * determine the IVs with which the data is encrypted.
+ */
+ DMDEBUG("Zone append operations will be emulated");
+ ti->emulate_zone_append = true;
+ }
+
+ /* optional arguments */
+ dkc->sector_size = SECTOR_SIZE;
+ if (argc > 5) {
+ err = default_key_ctr_optional(ti, argc - 5, &argv[5]);
+ if (err)
+ goto bad;
+ }
+ dkc->sector_bits = ilog2(dkc->sector_size);
+ if (ti->len & ((dkc->sector_size >> SECTOR_SHIFT) - 1)) {
+ ti->error = "Device size is not a multiple of sector_size";
+ err = -EINVAL;
+ goto bad;
+ }
+
+ dkc->max_dun = (dkc->iv_offset + ti->len - 1) >>
+ (dkc->sector_bits - SECTOR_SHIFT);
+ dun_bytes = DIV_ROUND_UP(fls64(dkc->max_dun), 8);
+
+ err = blk_crypto_init_key(&dkc->key, raw_key, cipher->mode_num,
+ dun_bytes, dkc->sector_size);
+ if (err) {
+ ti->error = "Error initializing blk-crypto key";
+ goto bad;
+ }
+
+ err = blk_crypto_start_using_key(dkc->dev->bdev, &dkc->key);
+ if (err) {
+ ti->error = "Error starting to use blk-crypto";
+ goto bad;
+ }
+
+ ti->num_flush_bios = 1;
+
+ err = 0;
+ goto out;
+
+bad:
+ default_key_dtr(ti);
+out:
+ memzero_explicit(raw_key, sizeof(raw_key));
+ return err;
+}
+
+static int default_key_map(struct dm_target *ti, struct bio *bio)
+{
+ const struct default_key_c *dkc = ti->private;
+ sector_t sector_in_target;
+ u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE] = {};
+
+ bio_set_dev(bio, dkc->dev->bdev);
+
+ /*
+ * If the bio is a device-level request which doesn't target a specific
+ * sector, there's nothing more to do.
+ */
+ if (bio_sectors(bio) == 0)
+ return DM_MAPIO_REMAPPED;
+
+ /* Map the bio's sector to the underlying device. (512-byte sectors) */
+ sector_in_target = dm_target_offset(ti, bio->bi_iter.bi_sector);
+ bio->bi_iter.bi_sector = dkc->start + sector_in_target;
+
+ /*
+ * If the bio should skip dm-default-key (i.e. if it's for an encrypted
+ * file's contents), or if it doesn't have any data (e.g. if it's a
+ * DISCARD request), there's nothing more to do.
+ */
+ if (bio_should_skip_dm_default_key(bio) || !bio_has_data(bio))
+ return DM_MAPIO_REMAPPED;
+
+ /*
+ * Else, dm-default-key needs to set this bio's encryption context.
+ * It must not already have one.
+ */
+ if (WARN_ON_ONCE(bio_has_crypt_ctx(bio)))
+ return DM_MAPIO_KILL;
+
+ /* Calculate the DUN and enforce data-unit (crypto sector) alignment. */
+ dun[0] = dkc->iv_offset + sector_in_target; /* 512-byte sectors */
+ if (dun[0] & ((dkc->sector_size >> SECTOR_SHIFT) - 1))
+ return DM_MAPIO_KILL;
+ dun[0] >>= dkc->sector_bits - SECTOR_SHIFT; /* crypto sectors */
+
+ /*
+ * This check isn't necessary as we should have calculated max_dun
+ * correctly, but be safe.
+ */
+ if (WARN_ON_ONCE(dun[0] > dkc->max_dun))
+ return DM_MAPIO_KILL;
+
+ bio_crypt_set_ctx(bio, &dkc->key, dun, GFP_NOIO);
+
+ return DM_MAPIO_REMAPPED;
+}
+
+static void default_key_status(struct dm_target *ti, status_type_t type,
+ unsigned int status_flags, char *result,
+ unsigned int maxlen)
+{
+ const struct default_key_c *dkc = ti->private;
+ unsigned int sz = 0;
+ int num_feature_args = 0;
+
+ switch (type) {
+ case STATUSTYPE_INFO:
+ case STATUSTYPE_IMA:
+ result[0] = '\0';
+ break;
+
+ case STATUSTYPE_TABLE:
+ /* Omit the key for now. */
+ DMEMIT("%s - %llu %s %llu", dkc->cipher_string, dkc->iv_offset,
+ dkc->dev->name, (unsigned long long)dkc->start);
+
+ num_feature_args += !!ti->num_discard_bios;
+ if (dkc->sector_size != SECTOR_SIZE)
+ num_feature_args += 2;
+ if (num_feature_args != 0) {
+ DMEMIT(" %d", num_feature_args);
+ if (ti->num_discard_bios)
+ DMEMIT(" allow_discards");
+ if (dkc->sector_size != SECTOR_SIZE) {
+ DMEMIT(" sector_size:%u", dkc->sector_size);
+ DMEMIT(" iv_large_sectors");
+ }
+ }
+ break;
+ }
+}
+
+static int default_key_prepare_ioctl(struct dm_target *ti,
+ struct block_device **bdev)
+{
+ const struct default_key_c *dkc = ti->private;
+ const struct dm_dev *dev = dkc->dev;
+
+ *bdev = dev->bdev;
+
+ /* Only pass ioctls through if the device sizes match exactly. */
+ return dkc->start != 0 || ti->len != bdev_nr_sectors(dev->bdev);
+}
+
+static int default_key_iterate_devices(struct dm_target *ti,
+ iterate_devices_callout_fn fn,
+ void *data)
+{
+ const struct default_key_c *dkc = ti->private;
+
+ return fn(ti, dkc->dev, dkc->start, ti->len, data);
+}
+
+#ifdef CONFIG_BLK_DEV_ZONED
+static int default_key_report_zones(struct dm_target *ti,
+ struct dm_report_zones_args *args,
+ unsigned int nr_zones)
+{
+ const struct default_key_c *dkc = ti->private;
+
+ return dm_report_zones(dkc->dev->bdev, dkc->start,
+ dkc->start + dm_target_offset(ti, args->next_sector),
+ args, nr_zones);
+}
+#else
+#define default_key_report_zones NULL
+#endif
+
+static void default_key_io_hints(struct dm_target *ti,
+ struct queue_limits *limits)
+{
+ const struct default_key_c *dkc = ti->private;
+ const unsigned int sector_size = dkc->sector_size;
+
+ limits->logical_block_size =
+ max_t(unsigned int, limits->logical_block_size, sector_size);
+ limits->physical_block_size =
+ max_t(unsigned int, limits->physical_block_size, sector_size);
+ limits->io_min = max_t(unsigned int, limits->io_min, sector_size);
+ limits->dma_alignment = limits->logical_block_size - 1;
+}
+
+static struct target_type default_key_target = {
+ .name = "default-key",
+ .version = {1, 0, 0},
+ .features = DM_TARGET_PASSES_CRYPTO | DM_TARGET_ZONED_HM,
+ .module = THIS_MODULE,
+ .ctr = default_key_ctr,
+ .dtr = default_key_dtr,
+ .map = default_key_map,
+ .status = default_key_status,
+ .prepare_ioctl = default_key_prepare_ioctl,
+ .iterate_devices = default_key_iterate_devices,
+ .report_zones = default_key_report_zones,
+ .io_hints = default_key_io_hints,
+};
+
+static int __init dm_default_key_init(void)
+{
+ return dm_register_target(&default_key_target);
+}
+
+static void __exit dm_default_key_exit(void)
+{
+ dm_unregister_target(&default_key_target);
+}
+
+module_init(dm_default_key_init);
+module_exit(dm_default_key_exit);
+
+MODULE_AUTHOR("Paul Lawrence <paullawrence@xxxxxxxxxx>");
+MODULE_AUTHOR("Paul Crowley <paulcrowley@xxxxxxxxxx>");
+MODULE_AUTHOR("Eric Biggers <ebiggers@xxxxxxxxxx>");
+MODULE_DESCRIPTION(DM_NAME " target for encrypting filesystem metadata");
+MODULE_LICENSE("GPL");
--
2.47.0
