Raw receive should change key atomically

Currently, raw zfs sends transfer the encrypted master keys and
objset_phys_t encryption parameters in the DRR_BEGIN payload of
each send file. Both of these are processed as soon as they are
read in dmu_recv_stream(), meaning that the new keys are set
before the new snapshot is received. In addition to the fact that
this changes the user's keys for the dataset earlier than they
might expect, the keys were never reset to what they originally
were in the event that the receive failed. This patch splits the
processing into objset handling and key handling, the later of
which is moved to dmu_recv_end() so that they key change can be
done atomically.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tom Caputi <[email protected]>
Closes #7200 

1 files changed, 30 insertions, 4 deletions

diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index bbb319822..16dc13939 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -3787,11 +3787,20 @@ dmu_recv_stream(dmu_recv_cookie_t *drc, vnode_t *vp, offset_t *voffp,
 		if (err != 0)
 			goto out;
 
-		err = dsl_crypto_recv_key(spa_name(ra->os->os_spa),
+		/*
+		 * If this is a new dataset we set the key immediately.
+		 * Otherwise we don't want to change the key until we
+		 * are sure the rest of the receive succeeded so we stash
+		 * the keynvl away until then.
+		 */
+		err = dsl_crypto_recv_raw(spa_name(ra->os->os_spa),
 		    drc->drc_ds->ds_object, drc->drc_drrb->drr_type,
-		    keynvl);
+		    keynvl, drc->drc_newfs);
 		if (err != 0)
 			goto out;
+
+		if (!drc->drc_newfs)
+			drc->drc_keynvl = fnvlist_dup(keynvl);
 	}
 
 	if (featureflags & DMU_BACKUP_FEATURE_RESUMING) {
@@ -3908,6 +3917,7 @@ out:
 		 * the inconsistent state.
 		 */
 		dmu_recv_cleanup_ds(drc);
+		nvlist_free(drc->drc_keynvl);
 	}
 
 	*voffp = ra->voff;
@@ -3965,6 +3975,15 @@ dmu_recv_end_check(void *arg, dmu_tx_t *tx)
 				return (error);
 			}
 		}
+		if (drc->drc_keynvl != NULL) {
+			error = dsl_crypto_recv_raw_key_check(drc->drc_ds,
+			    drc->drc_keynvl, tx);
+			if (error != 0) {
+				dsl_dataset_rele(origin_head, FTAG);
+				return (error);
+			}
+		}
+
 		error = dsl_dataset_clone_swap_check_impl(drc->drc_ds,
 		    origin_head, drc->drc_force, drc->drc_owner, tx);
 		if (error != 0) {
@@ -4021,8 +4040,14 @@ dmu_recv_end_sync(void *arg, dmu_tx_t *tx)
 				dsl_dataset_rele(snap, FTAG);
 			}
 		}
-		VERIFY3P(drc->drc_ds->ds_prev, ==,
-		    origin_head->ds_prev);
+		if (drc->drc_keynvl != NULL) {
+			dsl_crypto_recv_raw_key_sync(drc->drc_ds,
+			    drc->drc_keynvl, tx);
+			nvlist_free(drc->drc_keynvl);
+			drc->drc_keynvl = NULL;
+		}
+
+		VERIFY3P(drc->drc_ds->ds_prev, ==, origin_head->ds_prev);
 
 		dsl_dataset_clone_swap_sync_impl(drc->drc_ds,
 		    origin_head, tx);
@@ -4174,6 +4199,7 @@ dmu_recv_end(dmu_recv_cookie_t *drc, void *owner)
 
 	if (error != 0) {
 		dmu_recv_cleanup_ds(drc);
+		nvlist_free(drc->drc_keynvl);
 	} else if (drc->drc_guid_to_ds_map != NULL) {
 		(void) add_ds_to_guidmap(drc->drc_tofs, drc->drc_guid_to_ds_map,
 		    drc->drc_newsnapobj, drc->drc_raw);