Nfts: Multiple approvals

bin/node/runtime/src/lib.rs

@@ -1453,6 +1453,7 @@ parameter_types! {
 	pub const ItemDeposit: Balance = 1 * DOLLARS;
 	pub const KeyLimit: u32 = 32;
 	pub const ValueLimit: u32 = 256;
+	pub const ApprovalsLimit: u32 = 20;
 }
 
 impl pallet_uniques::Config for Runtime {
@@ -1490,6 +1491,7 @@ impl pallet_nfts::Config for Runtime {
 	type StringLimit = StringLimit;
 	type KeyLimit = KeyLimit;
 	type ValueLimit = ValueLimit;
+	type ApprovalsLimit = ApprovalsLimit;
 	type WeightInfo = pallet_nfts::weights::SubstrateWeight<Runtime>;
 	#[cfg(feature = "runtime-benchmarks")]
 	type Helper = ();

frame/nfts/src/benchmarking.rs

@@ -368,9 +368,10 @@ benchmarks_instance_pallet! {
 		let (item, ..) = mint_item::<T, I>(0);
 		let delegate: T::AccountId = account("delegate", 0, SEED);
 		let delegate_lookup = T::Lookup::unlookup(delegate.clone());
-	}: _(SystemOrigin::Signed(caller.clone()), collection, item, delegate_lookup)
+		let deadline = T::BlockNumber::max_value();
+	}: _(SystemOrigin::Signed(caller.clone()), collection, item, delegate_lookup, Some(deadline))
 	verify {
-		assert_last_event::<T, I>(Event::ApprovedTransfer { collection, item, owner: caller, delegate }.into());
+		assert_last_event::<T, I>(Event::ApprovedTransfer { collection, item, owner: caller, delegate, deadline: Some(deadline) }.into());
 	}
 
 	cancel_approval {
@@ -379,12 +380,26 @@ benchmarks_instance_pallet! {
 		let delegate: T::AccountId = account("delegate", 0, SEED);
 		let delegate_lookup = T::Lookup::unlookup(delegate.clone());
 		let origin = SystemOrigin::Signed(caller.clone()).into();
-		Nfts::<T, I>::approve_transfer(origin, collection, item, delegate_lookup.clone())?;
-	}: _(SystemOrigin::Signed(caller.clone()), collection, item, Some(delegate_lookup))
+		let deadline = T::BlockNumber::max_value();
+		Nfts::<T, I>::approve_transfer(origin, collection, item, delegate_lookup.clone(), Some(deadline))?;
+	}: _(SystemOrigin::Signed(caller.clone()), collection, item, delegate_lookup)
 	verify {
 		assert_last_event::<T, I>(Event::ApprovalCancelled { collection, item, owner: caller, delegate }.into());
 	}
 
+	clear_all_transfer_approvals {
+		let (collection, caller, _) = create_collection::<T, I>();
+		let (item, ..) = mint_item::<T, I>(0);
+		let delegate: T::AccountId = account("delegate", 0, SEED);
+		let delegate_lookup = T::Lookup::unlookup(delegate.clone());
+		let origin = SystemOrigin::Signed(caller.clone()).into();
+		let deadline = T::BlockNumber::max_value();
+		Nfts::<T, I>::approve_transfer(origin, collection, item, delegate_lookup.clone(), Some(deadline))?;
+	}: _(SystemOrigin::Signed(caller.clone()), collection, item)
+	verify {
+		assert_last_event::<T, I>(Event::AllApprovalsCancelled {collection, item, owner: caller}.into());
+	}
+
 	set_accept_ownership {
 		let caller: T::AccountId = whitelisted_caller();
 		T::Currency::make_free_balance_be(&caller, DepositBalanceOf::<T, I>::max_value());

frame/nfts/src/functions.rs

@@ -48,6 +48,12 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		Account::<T, I>::insert((&dest, &collection, &item), ());
 		let origin = details.owner;
 		details.owner = dest;
+
+		// The approved accounts have to be reset to None, because otherwise pre-approve attack
+		// would be possible, where the owner can approve his second account before making the
+		// transaction and then claiming the item back.
+		details.approvals.clear();
+
 		Item::<T, I>::insert(&collection, &item, &details);
 		ItemPriceOf::<T, I>::remove(&collection, &item);
 
@@ -168,7 +174,12 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 
 				let owner = owner.clone();
 				Account::<T, I>::insert((&owner, &collection, &item), ());
-				let details = ItemDetails { owner, approved: None, is_frozen: false, deposit };
+				let details = ItemDetails {
+					owner,
+					approvals: ApprovalsOf::<T, I>::default(),
+					is_frozen: false,
+					deposit,
+				};
 				Item::<T, I>::insert(&collection, &item, details);
 				Ok(())
 			},