Encryption Stability and On-Disk Format Fixes

The on-disk format for encrypted datasets protects not only
the encrypted and authenticated blocks themselves, but also
the order and interpretation of these blocks. In order to
make this work while maintaining the ability to do raw
sends, the indirect bps maintain a secure checksum of all
the MACs in the block below it along with a few other
fields that determine how the data is interpreted.

Unfortunately, the current on-disk format erroneously
includes some fields which are not portable and thus cannot
support raw sends. It is not possible to easily work around
this issue due to a separate and much smaller bug which
causes indirect blocks for encrypted dnodes to not be
compressed, which conflicts with the previous bug. In
addition, the current code generates incompatible on-disk
formats on big endian and little endian systems due to an
issue with how block pointers are authenticated. Finally,
raw send streams do not currently include dn_maxblkid when
sending both the metadnode and normal dnodes which are
needed in order to ensure that we are correctly maintaining
the portable objset MAC.

This patch zero's out the offending fields when computing
the bp MAC and ensures that these MACs are always
calculated in little endian order (regardless of the host
system's byte order). This patch also registers an errata
for the old on-disk format, which we detect by adding a
"version" field to newly created DSL Crypto Keys. We allow
datasets without a version (version 0) to only be mounted
for read so that they can easily be migrated. We also now
include dn_maxblkid in raw send streams to ensure the MAC
can be maintained correctly.

This patch also contains minor bug fixes and cleanups.

Reviewed-by: Jorgen Lundman <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed by: Matthew Ahrens <[email protected]>
Signed-off-by: Tom Caputi <[email protected]>
Closes #6845
Closes #6864
Closes #7052

1 files changed, 8 insertions, 0 deletions

diff --git a/include/sys/dnode.h b/include/sys/dnode.h
index e5e39b18c..a2bef9d2c 100644
--- a/include/sys/dnode.h
+++ b/include/sys/dnode.h
@@ -221,6 +221,13 @@ typedef struct dnode_phys {
 	uint64_t dn_maxblkid;		/* largest allocated block ID */
 	uint64_t dn_used;		/* bytes (or sectors) of disk space */
 
+	/*
+	 * Both dn_pad2 and dn_pad3 are protected by the block's MAC. This
+	 * allows us to protect any fields that might be added here in the
+	 * future. In either case, developers will want to check
+	 * zio_crypt_init_uios_dnode() to ensure the new field is being
+	 * protected properly.
+	 */
 	uint64_t dn_pad3[4];
 
 	/*
@@ -301,6 +308,7 @@ struct dnode {
 	uint8_t dn_rm_spillblk[TXG_SIZE];	/* for removing spill blk */
 	uint16_t dn_next_bonuslen[TXG_SIZE];
 	uint32_t dn_next_blksz[TXG_SIZE];	/* next block size in bytes */
+	uint64_t dn_next_maxblkid[TXG_SIZE];	/* next maxblkid in bytes */
 
 	/* protected by dn_dbufs_mtx; declared here to fill 32-bit hole */
 	uint32_t dn_dbufs_count;	/* count of dn_dbufs */