From eabc2ac7b133e6ad41a022f92161ad468349148d Mon Sep 17 00:00:00 2001
From: teor <teor@riseup.net>
Date: Fri, 17 Jan 2025 12:27:47 +1000
Subject: [PATCH] Use a custom error value for contract allow list failures

---
 domains/runtime/evm/src/lib.rs | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/domains/runtime/evm/src/lib.rs b/domains/runtime/evm/src/lib.rs
index 0adaf95026..68779548a9 100644
--- a/domains/runtime/evm/src/lib.rs
+++ b/domains/runtime/evm/src/lib.rs
@@ -148,6 +148,10 @@ pub type Executive = domain_pallet_executive::Executive<
     AllPalletsWithSystem,
 >;
 
+/// The custom error value returned when a user tries to create a contract, but their account is
+/// not on the allow list.
+pub const ERR_CONTRACT_CREATION_NOT_ALLOWED_BY_USER: u8 = 0xCC;
+
 const MAX_CONTRACT_RECURSION_DEPTH: u16 = 5;
 
 /// Rejects contracts that can't be created under the current allow list.
@@ -210,6 +214,9 @@ pub fn is_create_contract(call: &RuntimeCall, mut recursion_depth_left: u16) ->
 #[derive(Debug, Encode, Decode, Clone, Eq, PartialEq, Default, TypeInfo)]
 pub struct CheckContractCreation;
 
+// Unsigned calls can't create contracts. Only pallet-evm and pallet-ethereum can create contracts.
+// For pallet-evm all contracts are signed extrinsics, for pallet-ethereum there is only one
+// extrinsic that is self-contained.
 impl SignedExtension for CheckContractCreation {
     const IDENTIFIER: &'static str = "CheckContractCreation";
     type AccountId = <Runtime as frame_system::Config>::AccountId;
@@ -230,7 +237,7 @@ impl SignedExtension for CheckContractCreation {
     ) -> TransactionValidity {
         // Reject contract creation unless the account is in the allow list.
         if !is_create_contract_allowed(call, who) {
-            InvalidTransaction::Call.into()
+            InvalidTransaction::Custom(ERR_CONTRACT_CREATION_NOT_ALLOWED_BY_USER).into()
         } else {
             Ok(ValidTransaction::default())
         }
@@ -246,8 +253,6 @@ impl SignedExtension for CheckContractCreation {
         self.validate(who, call, info, len)?;
         Ok(())
     }
-
-    // TODO: can unsigned calls create contracts?
 }
 
 impl fp_self_contained::SelfContainedCall for RuntimeCall {
@@ -274,8 +279,10 @@ impl fp_self_contained::SelfContainedCall for RuntimeCall {
         len: usize,
     ) -> Option<TransactionValidity> {
         if !is_create_contract_allowed(self, &(*info).into()) {
-            // TODO: should this be Custom() instead?
-            return Some(Err(InvalidTransaction::Call.into()));
+            return Some(Err(InvalidTransaction::Custom(
+                ERR_CONTRACT_CREATION_NOT_ALLOWED_BY_USER,
+            )
+            .into()));
         }
 
         match self {
@@ -303,8 +310,10 @@ impl fp_self_contained::SelfContainedCall for RuntimeCall {
         len: usize,
     ) -> Option<Result<(), TransactionValidityError>> {
         if !is_create_contract_allowed(self, &(*info).into()) {
-            // TODO: should this be Custom() instead?
-            return Some(Err(InvalidTransaction::Call.into()));
+            return Some(Err(InvalidTransaction::Custom(
+                ERR_CONTRACT_CREATION_NOT_ALLOWED_BY_USER,
+            )
+            .into()));
         }
 
         match self {