f make inputs and outputs total value calcs overflow-safe

Author: dunxen

lightning/src/ln/interactivetxs.rs

@@ -305,10 +305,15 @@ impl NegotiationContext {
 		// MUST fail the negotiation if:
 
 		// - the peer's total input satoshis is less than their outputs
-		let counterparty_inputs_value: u64 =
-			self.counterparty_inputs_contributed().map(|input| input.prev_output.value).sum();
-		let counterparty_outputs_value =
-			self.counterparty_outputs_contributed().map(|output| output.value).sum();
+		let mut counterparty_inputs_value: u64 = 0;
+		let mut counterparty_outputs_value: u64 = 0;
+		for input in self.counterparty_inputs_contributed() {
+			counterparty_inputs_value =
+				counterparty_inputs_value.saturating_add(input.prev_output.value);
+		}
+		for output in self.counterparty_outputs_contributed() {
+			counterparty_outputs_value = counterparty_outputs_value.saturating_add(output.value);
+		}
 		if counterparty_inputs_value < counterparty_outputs_value {
 			return Err(AbortReason::OutputsValueExceedsInputsValue);
 		}