Native Encryption for ZFS on Linux

This change incorporates three major pieces:

The first change is a keystore that manages wrapping
and encryption keys for encrypted datasets. These
commands mostly involve manipulating the new
DSL Crypto Key ZAP Objects that live in the MOS. Each
encrypted dataset has its own DSL Crypto Key that is
protected with a user's key. This level of indirection
allows users to change their keys without re-encrypting
their entire datasets. The change implements the new
subcommands "zfs load-key", "zfs unload-key" and
"zfs change-key" which allow the user to manage their
encryption keys and settings. In addition, several new
flags and properties have been added to allow dataset
creation and to make mounting and unmounting more
convenient.

The second piece of this patch provides the ability to
encrypt, decyrpt, and authenticate protected datasets.
Each object set maintains a Merkel tree of Message
Authentication Codes that protect the lower layers,
similarly to how checksums are maintained. This part
impacts the zio layer, which handles the actual
encryption and generation of MACs, as well as the ARC
and DMU, which need to be able to handle encrypted
buffers and protected data.

The last addition is the ability to do raw, encrypted
sends and receives. The idea here is to send raw
encrypted and compressed data and receive it exactly
as is on a backup system. This means that the dataset
on the receiving system is protected using the same
user key that is in use on the sending side. By doing
so, datasets can be efficiently backed up to an
untrusted system without fear of data being
compromised.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #494 
Closes #5769

include/sys/fs/zfs.h

@@ -171,6 +171,14 @@ typedef enum {
 	ZFS_PROP_OVERLAY,
 	ZFS_PROP_PREV_SNAP,
 	ZFS_PROP_RECEIVE_RESUME_TOKEN,
+	ZFS_PROP_ENCRYPTION,
+	ZFS_PROP_KEYLOCATION,
+	ZFS_PROP_KEYFORMAT,
+	ZFS_PROP_PBKDF2_SALT,
+	ZFS_PROP_PBKDF2_ITERS,
+	ZFS_PROP_ENCRYPTION_ROOT,
+	ZFS_PROP_KEY_GUID,
+	ZFS_PROP_KEYSTATUS,
 	ZFS_NUM_PROPS
 } zfs_prop_t;
 
@@ -281,6 +289,8 @@ uint64_t zfs_prop_default_numeric(zfs_prop_t);
 boolean_t zfs_prop_readonly(zfs_prop_t);
 boolean_t zfs_prop_inheritable(zfs_prop_t);
 boolean_t zfs_prop_setonce(zfs_prop_t);
+boolean_t zfs_prop_encryption_key_param(zfs_prop_t);
+boolean_t zfs_prop_valid_keylocation(const char *, boolean_t);
 const char *zfs_prop_to_name(zfs_prop_t);
 zfs_prop_t zfs_name_to_prop(const char *);
 boolean_t zfs_prop_user(const char *);
@@ -404,6 +414,30 @@ typedef enum {
 	ZFS_VOLMODE_NONE = 3
 } zfs_volmode_t;
 
+typedef enum zfs_keystatus {
+	ZFS_KEYSTATUS_NONE = 0,
+	ZFS_KEYSTATUS_UNAVAILABLE,
+	ZFS_KEYSTATUS_AVAILABLE,
+} zfs_keystatus_t;
+
+typedef enum zfs_keyformat {
+	ZFS_KEYFORMAT_NONE = 0,
+	ZFS_KEYFORMAT_RAW,
+	ZFS_KEYFORMAT_HEX,
+	ZFS_KEYFORMAT_PASSPHRASE,
+	ZFS_KEYFORMAT_FORMATS
+} zfs_keyformat_t;
+
+typedef enum zfs_key_location {
+	ZFS_KEYLOCATION_NONE = 0,
+	ZFS_KEYLOCATION_PROMPT,
+	ZFS_KEYLOCATION_URI,
+	ZFS_KEYLOCATION_LOCATIONS
+} zfs_keylocation_t;
+
+#define	DEFAULT_PBKDF2_ITERATIONS 350000
+#define	MIN_PBKDF2_ITERATIONS 100000
+
 /*
  * On-disk version number.
  */
@@ -1061,6 +1095,9 @@ typedef enum zfs_ioc {
 	ZFS_IOC_DESTROY_BOOKMARKS,
 	ZFS_IOC_RECV_NEW,
 	ZFS_IOC_POOL_SYNC,
+	ZFS_IOC_LOAD_KEY,
+	ZFS_IOC_UNLOAD_KEY,
+	ZFS_IOC_CHANGE_KEY,
 
 	/*
 	 * Linux - 3/64 numbers reserved.
@@ -1125,6 +1162,12 @@ typedef enum {
 #define	ZPOOL_HIST_DSNAME	"dsname"
 #define	ZPOOL_HIST_DSID		"dsid"
 
+/*
+ * Special nvlist name that will not have its args recorded in the pool's
+ * history log.
+ */
+#define	ZPOOL_HIDDEN_ARGS	"hidden_args"
+
 /*
  * Flags for ZFS_IOC_VDEV_SET_STATE
  */
@@ -1144,6 +1187,7 @@ typedef enum {
 #define	ZFS_IMPORT_ONLY		0x8
 #define	ZFS_IMPORT_TEMP_NAME	0x10
 #define	ZFS_IMPORT_SKIP_MMP	0x20
+#define	ZFS_IMPORT_LOAD_KEYS	0x40
 
 /*
  * Sysevent payload members.  ZFS will generate the following sysevents with the