Detect and prevent mixed raw and non-raw sends

Currently, there is an issue in the raw receive code where
raw receives are allowed to happen on top of previously
non-raw received datasets. This is a problem because the
source-side dataset doesn't know about how the blocks on
the destination were encrypted. As a result, any MAC in
the objset's checksum-of-MACs tree that is a parent of both
blocks encrypted on the source and blocks encrypted by the
destination will be incorrect. This will result in
authentication errors when we decrypt the dataset.

This patch fixes this issue by adding a new check to the
raw receive code. The code now maintains an "IVset guid",
which acts as an identifier for the set of IVs used to
encrypt a given snapshot. When a snapshot is raw received,
the destination snapshot will take this value from the
DRR_BEGIN payload. Non-raw receives and normal "zfs snap"
operations will cause ZFS to generate a new IVset guid.
When a raw incremental stream is received, ZFS will check
that the "from" IVset guid in the stream matches that of
the "from" destination snapshot. If they do not match, the
code will error out the receive, preventing the problem.

This patch requires an on-disk format change to add the
IVset guids to snapshots and bookmarks. As a result, this
patch has errata handling and a tunable to help affected
users resolve the issue with as little interruption as
possible.

Reviewed-by: Paul Dagnelie <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Matt Ahrens <[email protected]>
Signed-off-by: Tom Caputi <[email protected]>
Closes #8308

1 files changed, 31 insertions, 0 deletions

diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index ad944e5b8..086750fed 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -621,6 +621,13 @@ dsl_dataset_hold_obj(dsl_pool_t *dp, uint64_t dsobj, void *tag,
 			ds->ds_reserved = ds->ds_quota = 0;
 		}
 
+		if (err == 0 && ds->ds_dir->dd_crypto_obj != 0 &&
+		    ds->ds_is_snapshot &&
+		    zap_contains(mos, dsobj, DS_FIELD_IVSET_GUID) != 0) {
+			dp->dp_spa->spa_errata =
+			    ZPOOL_ERRATA_ZOL_8308_ENCRYPTION;
+		}
+
 		dsl_deadlist_open(&ds->ds_deadlist,
 		    mos, dsl_dataset_phys(ds)->ds_deadlist_obj);
 		uint64_t remap_deadlist_obj =
@@ -1702,6 +1709,30 @@ dsl_dataset_snapshot_sync_impl(dsl_dataset_t *ds, const char *snapname,
 		    sizeof (remap_deadlist_obj), 1, &remap_deadlist_obj, tx));
 	}
 
+	/*
+	 * Create a ivset guid for this snapshot if the dataset is
+	 * encrypted. This may be overridden by a raw receive. A
+	 * previous implementation of this code did not have this
+	 * field as part of the on-disk format for ZFS encryption
+	 * (see errata #4). As part of the remediation for this
+	 * issue, we ask the user to enable the bookmark_v2 feature
+	 * which is now a dependency of the encryption feature. We
+	 * use this as a heuristic to determine when the user has
+	 * elected to correct any datasets created with the old code.
+	 * As a result, we only do this step if the bookmark_v2
+	 * feature is enabled, which limits the number of states a
+	 * given pool / dataset can be in with regards to terms of
+	 * correcting the issue.
+	 */
+	if (ds->ds_dir->dd_crypto_obj != 0 &&
+	    spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_BOOKMARK_V2)) {
+		uint64_t ivset_guid = unique_create();
+
+		dmu_object_zapify(mos, dsobj, DMU_OT_DSL_DATASET, tx);
+		VERIFY0(zap_add(mos, dsobj, DS_FIELD_IVSET_GUID,
+		    sizeof (ivset_guid), 1, &ivset_guid, tx));
+	}
+
 	ASSERT3U(dsl_dataset_phys(ds)->ds_prev_snap_txg, <, tx->tx_txg);
 	dsl_dataset_phys(ds)->ds_prev_snap_obj = dsobj;
 	dsl_dataset_phys(ds)->ds_prev_snap_txg = crtxg;