From 91206defc16406134d6d9a50d6762e07387c37b5 Mon Sep 17 00:00:00 2001
From: NikVolf <nikvolf@gmail.com>
Date: Wed, 14 Dec 2016 13:20:09 +0100
Subject: [PATCH] proper counting block fees and rewards

---
 verification/src/accept_block.rs | 37 ++++++++++++++------------------
 verification/src/error.rs        |  2 ++
 2 files changed, 18 insertions(+), 21 deletions(-)

diff --git a/verification/src/accept_block.rs b/verification/src/accept_block.rs
index 12c64bbb..87cd01c9 100644
--- a/verification/src/accept_block.rs
+++ b/verification/src/accept_block.rs
@@ -5,7 +5,7 @@ use work::block_reward_satoshi;
 use duplex_store::DuplexTransactionOutputProvider;
 use canon::CanonBlock;
 use constants::MAX_BLOCK_SIGOPS;
-use error::Error;
+use error::{Error, TransactionError};
 
 /// Flexible verification of ordered block
 pub struct BlockAcceptor<'a> {
@@ -115,11 +115,12 @@ impl<'a> BlockRule for BlockCoinbaseClaim<'a> {
 	fn check(&self) -> Result<(), Error> {
 		let store = DuplexTransactionOutputProvider::new(self.store, &*self.block);
 
-		let mut fee: u64 = 0;
+		let mut fees: u64 = 0;
 
 		for tx in self.block.transactions.iter().skip(1) {
+			// (1) Total sum of all referenced outputs
 			let mut incoming: u64 = 0;
-			for input in tx.inputs.iter() {
+			for input in tx.raw.inputs.iter() {
 				let (sum, overflow) = incoming.overflowing_add(
 					store.previous_transaction_output(&input.previous_output).map(|o| o.value).unwrap_or(0));
 				if overflow {
@@ -128,31 +129,25 @@ impl<'a> BlockRule for BlockCoinbaseClaim<'a> {
 				incoming = sum;
 			}
 
-			let spends = tx.total_spends();
+			// (2) Total sum of all outputs
+			let spends = tx.raw.total_spends();
 
-			let (sum, overflow) = fee.overflowing_add(incoming);
+			// Difference between (1) and (2)
+			let (difference, overflow) = incoming.overflowing_sub(spends);
 			if overflow {
-				return Err(Error::
+				return Err(Error::Transaction(2, TransactionError::Overspend))
 			}
 
+			// Adding to total fees (with possible overflow)
+			let (sum, overflow) = fees.overflowing_add(difference);
+			if overflow {
+				return Err(Error::TransactionFeesOverflow)
+			}
+
+			fees = sum;
 		}
 
-		let available = self.block.transactions.iter()
-			.skip(1)
-			.flat_map(|tx| tx.raw.inputs.iter())
-			.map(|input| store.previous_transaction_output(&input.previous_output).map(|o| o.value).unwrap_or(0))
-			.sum::<u64>();
-
-		let spends = self.block.transactions.iter()
-			.skip(1)
-			.map(|tx| tx.raw.total_spends())
-			.sum::<u64>();
-
 		let claim = self.block.transactions[0].raw.total_spends();
-		let (fees, overflow) = available.overflowing_sub(spends);
-		if overflow {
-			return Err(Error::TransactionFeesOverflow);
-		}
 
 		let (reward, overflow) = fees.overflowing_add(block_reward_satoshi(self.height));
 		if overflow {
diff --git a/verification/src/error.rs b/verification/src/error.rs
index 72b2f8f0..50e7e7c5 100644
--- a/verification/src/error.rs
+++ b/verification/src/error.rs
@@ -40,6 +40,8 @@ pub enum Error {
 	TransactionFeeAndRewardOverflow,
 	/// Sum of the transaction fees in block exceeds u64::max
 	TransactionFeesOverflow,
+	/// Sum of all referenced outputs in block transactions resulted in the overflow
+	ReferencedInputsSumOverflow
 }
 
 #[derive(Debug, PartialEq)]