diff --git a/bridges/snowbridge/primitives/router/src/inbound/mod.rs b/bridges/snowbridge/primitives/router/src/inbound/mod.rs index fbfc52d01c83..a9324ac42470 100644 --- a/bridges/snowbridge/primitives/router/src/inbound/mod.rs +++ b/bridges/snowbridge/primitives/router/src/inbound/mod.rs @@ -416,6 +416,8 @@ where // Final destination is a 32-byte account on AssetHub Destination::AccountId32 { id } => Ok(Location::new(0, [AccountId32 { network: None, id }])), + // Forwarding to a destination parachain is not allowed for PNA and is validated on the + // Ethereum side. https://github.com/Snowfork/snowbridge/blob/e87ddb2215b513455c844463a25323bb9c01ff36/contracts/src/Assets.sol#L216-L224 _ => Err(ConvertMessageError::InvalidDestination), }?; diff --git a/bridges/snowbridge/primitives/router/src/outbound/mod.rs b/bridges/snowbridge/primitives/router/src/outbound/mod.rs index efc1ef56f304..3b5dbdb77c89 100644 --- a/bridges/snowbridge/primitives/router/src/outbound/mod.rs +++ b/bridges/snowbridge/primitives/router/src/outbound/mod.rs @@ -207,9 +207,9 @@ where fn convert(&mut self) -> Result<(Command, [u8; 32]), XcmConverterError> { let result = match self.peek() { - Ok(ReserveAssetDeposited { .. }) => self.send_native_tokens_message(), + Ok(ReserveAssetDeposited { .. }) => self.make_mint_foreign_token_command(), // Get withdraw/deposit and make native tokens create message. - Ok(WithdrawAsset { .. }) => self.send_tokens_message(), + Ok(WithdrawAsset { .. }) => self.make_unlock_native_token_command(), Err(e) => Err(e), _ => return Err(XcmConverterError::UnexpectedInstruction), }?; @@ -222,7 +222,9 @@ where Ok(result) } - fn send_tokens_message(&mut self) -> Result<(Command, [u8; 32]), XcmConverterError> { + fn make_unlock_native_token_command( + &mut self, + ) -> Result<(Command, [u8; 32]), XcmConverterError> { use XcmConverterError::*; // Get the reserve assets from WithdrawAsset. @@ -271,7 +273,12 @@ where ensure!(reserve_assets.len() == 1, TooManyAssets); let reserve_asset = reserve_assets.get(0).ok_or(AssetResolutionFailed)?; - // If there was a fee specified verify it. + // Fees are collected on AH, up front and directly from the user, to cover the + // complete cost of the transfer. Any additional fees provided in the XCM program are + // refunded to the beneficiary. We only validate the fee here if its provided to make sure + // the XCM program is well formed. Another way to think about this from an XCM perspective + // would be that the user offered to pay X amount in fees, but we charge 0 of that X amount + // (no fee) and refund X to the user. if let Some(fee_asset) = fee_asset { // The fee asset must be the same as the reserve asset. if fee_asset.id != reserve_asset.id || fee_asset.fun > reserve_asset.fun { @@ -328,7 +335,9 @@ where /// # BuyExecution /// # DepositAsset /// # SetTopic - fn send_native_tokens_message(&mut self) -> Result<(Command, [u8; 32]), XcmConverterError> { + fn make_mint_foreign_token_command( + &mut self, + ) -> Result<(Command, [u8; 32]), XcmConverterError> { use XcmConverterError::*; // Get the reserve assets. @@ -377,7 +386,12 @@ where ensure!(reserve_assets.len() == 1, TooManyAssets); let reserve_asset = reserve_assets.get(0).ok_or(AssetResolutionFailed)?; - // If there was a fee specified verify it. + // Fees are collected on AH, up front and directly from the user, to cover the + // complete cost of the transfer. Any additional fees provided in the XCM program are + // refunded to the beneficiary. We only validate the fee here if its provided to make sure + // the XCM program is well formed. Another way to think about this from an XCM perspective + // would be that the user offered to pay X amount in fees, but we charge 0 of that X amount + // (no fee) and refund X to the user. if let Some(fee_asset) = fee_asset { // The fee asset must be the same as the reserve asset. if fee_asset.id != reserve_asset.id || fee_asset.fun > reserve_asset.fun {