fix(privacy-channel): remove dead reentrancy guard (audit informative)

contracts/privacy-channel/src/contract.rs

@@ -1,9 +1,5 @@
-use moonlight_errors::Error;
 use moonlight_utxo_core::core::UtxoHandlerTrait;
-use soroban_sdk::{
-    contract, contractevent, contractimpl, panic_with_error, symbol_short, Address, BytesN, Env,
-    Symbol, Vec,
-};
+use soroban_sdk::{contract, contractevent, contractimpl, Address, BytesN, Env, Vec};
 use stellar_access::ownable;
 use stellar_contract_utils::upgradeable;
 
@@ -36,23 +32,6 @@ fn bump_instance_ttl(e: &Env) {
         .extend_ttl(INSTANCE_LIFETIME_THRESHOLD, INSTANCE_BUMP_AMOUNT);
 }
 
-// MOON-06: reentrancy guard. `transact` makes external SAC calls (deposit pull / withdraw push);
-// a non-standard or malicious asset could call back into `transact`. The guard is a transient flag
-// that is set on entry and cleared on exit; a re-entrant call observes it and reverts. (On revert
-// the transient write is rolled back, so the flag never persists across transactions.)
-const REENTRANCY_GUARD: Symbol = symbol_short!("RGUARD");
-
-fn enter_reentrancy_guard(e: &Env) {
-    if e.storage().temporary().has(&REENTRANCY_GUARD) {
-        panic_with_error!(e, Error::ReentrantCall);
-    }
-    e.storage().temporary().set(&REENTRANCY_GUARD, &true);
-}
-
-fn exit_reentrancy_guard(e: &Env) {
-    e.storage().temporary().remove(&REENTRANCY_GUARD);
-}
-
 #[contractimpl]
 impl PrivacyChannelContract {
     pub fn __constructor(e: &Env, admin: Address, auth_contract: Address, asset: Address) {
@@ -106,15 +85,12 @@ impl PrivacyChannelContract {
 
     pub fn transact(e: Env, op: ChannelOperation) {
         bump_instance_ttl(&e);
-        enter_reentrancy_guard(&e);
 
         let (utxo_op, total_deposit, total_withdraw) =
             pre_process_channel_operation(&e, op.clone());
 
         Self::process_bundle(&e, utxo_op.clone(), total_deposit, total_withdraw);
 
         execute_external_operations(&e, op.deposit, op.withdraw);
-
-        exit_reentrancy_guard(&e);
     }
 }

contracts/privacy-channel/src/test/mod.rs

@@ -4,6 +4,4 @@ pub mod moon01;
 #[cfg(test)]
 pub mod moon05;
 #[cfg(test)]
-pub mod moon06;
-#[cfg(test)]
 pub mod test;

modules/errors/src/lib.rs

@@ -86,8 +86,6 @@ pub enum MoonlightError {
     UnauthorizedOperation = 3_006,
     /// A deposit or withdraw amount was not strictly positive.
     InvalidExternalAmount = 3_007,
-    /// `transact` was re-entered while a call was already in progress.
-    ReentrantCall = 3_008,
 
     // Helper errors: 4000-4099.
     /// An address payload was expected to be an Ed25519 account address but was not.