From 26be0727e5aaa5ed569b29bd9a6b043899a5617b Mon Sep 17 00:00:00 2001
From: Gavin Wood <gavin@parity.io>
Date: Tue, 22 Aug 2023 13:19:05 +0200
Subject: [PATCH] Bound number of assets which can be withdrawn to pay for
 execution. (#7641)

* Bound number of assets which can be withdrawn to pay for execution.

* ".git/.scripts/commands/fmt/fmt.sh"

* Include ClaimAsset in limiting the assets

* Change max assets to constant

---------

Co-authored-by: command-bot <>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
---
 polkadot/xcm/xcm-builder/src/barriers.rs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/polkadot/xcm/xcm-builder/src/barriers.rs b/polkadot/xcm/xcm-builder/src/barriers.rs
index 6996c7145528..353e111b813b 100644
--- a/polkadot/xcm/xcm-builder/src/barriers.rs
+++ b/polkadot/xcm/xcm-builder/src/barriers.rs
@@ -52,6 +52,8 @@ impl ShouldExecute for TakeWeightCredit {
 	}
 }
 
+const MAX_ASSETS_FOR_BUY_EXECUTION: usize = 1;
+
 /// Allows execution from `origin` if it is contained in `T` (i.e. `T::Contains(origin)`) taking
 /// payments into account.
 ///
@@ -79,10 +81,10 @@ impl<T: Contains<MultiLocation>> ShouldExecute for AllowTopLevelPaidExecutionFro
 		instructions[..end]
 			.matcher()
 			.match_next_inst(|inst| match inst {
-				ReceiveTeleportedAsset(..) |
-				WithdrawAsset(..) |
-				ReserveAssetDeposited(..) |
-				ClaimAsset { .. } => Ok(()),
+				ReceiveTeleportedAsset(..) | ReserveAssetDeposited(..) => Ok(()),
+				WithdrawAsset(ref assets) if assets.len() <= MAX_ASSETS_FOR_BUY_EXECUTION => Ok(()),
+				ClaimAsset { ref assets, .. } if assets.len() <= MAX_ASSETS_FOR_BUY_EXECUTION =>
+					Ok(()),
 				_ => Err(ProcessMessageError::BadFormat),
 			})?
 			.skip_inst_while(|inst| matches!(inst, ClearOrigin))?