Support for genesis block that includes a coinbase (mimblewimble#2079)

* Chain init now handles genesis body properly, related unit test creating the genesis with reward
* Avoid making block body public by adding a with_reward method
* apply_block in all genesis cases works

chain/src/chain.rs

@@ -28,7 +28,7 @@ use core::core::hash::{Hash, Hashed, ZERO_HASH};
 use core::core::merkle_proof::MerkleProof;
 use core::core::verifier_cache::VerifierCache;
 use core::core::{
-	Block, BlockHeader, BlockSums, Output, OutputIdentifier, Transaction, TxKernelEntry,
+	Block, BlockHeader, BlockSums, Committed, Output, OutputIdentifier, Transaction, TxKernelEntry,
 };
 use core::global;
 use core::pow;
@@ -1231,6 +1231,8 @@ fn setup_head(
 			}
 		}
 		Err(NotFoundErr(_)) => {
+			let mut sums = BlockSums::default();
+
 			// Save the genesis header with a "zero" header_root.
 			// We will update this later once we have the correct header_root.
 			batch.save_block_header(&genesis.header)?;
@@ -1239,16 +1241,27 @@ fn setup_head(
 			let tip = Tip::from_header(&genesis.header);
 			batch.save_head(&tip)?;
 
-			// Initialize our header MM with the genesis header.
-			txhashset::header_extending(txhashset, &mut batch, |extension| {
-				extension.apply_header(&genesis.header)?;
+			batch.save_block_header(&genesis.header)?;
+
+			if genesis.kernels().len() > 0 {
+				let (utxo_sum, kernel_sum) = (sums, &genesis as &Committed).verify_kernel_sums(
+					genesis.header.overage(),
+					genesis.header.total_kernel_offset(),
+				)?;
+				sums = BlockSums {
+					utxo_sum,
+					kernel_sum,
+				};
+			}
+			txhashset::extending(txhashset, &mut batch, |extension| {
+				extension.apply_block(&genesis)?;
+				extension.validate_roots()?;
+				extension.validate_sizes()?;
 				Ok(())
 			})?;
 
-			batch.save_block_header(&genesis.header)?;
-
 			// Save the block_sums to the db for use later.
-			batch.save_block_sums(&genesis.hash(), &BlockSums::default())?;
+			batch.save_block_sums(&genesis.hash(), &sums)?;
 
 			info!("init: saved genesis: {:?}", genesis.hash());
 		}

chain/src/txhashset/txhashset.rs

@@ -999,7 +999,7 @@ impl<'a> Extension<'a> {
 	/// Get the header at the specified height based on the current state of the extension.
 	/// Derives the MMR pos from the height (insertion index) and retrieves the header hash.
 	/// Looks the header up in the db by hash.
-	pub fn get_header_by_height(&mut self, height: u64) -> Result<BlockHeader, Error> {
+	pub fn get_header_by_height(&self, height: u64) -> Result<BlockHeader, Error> {
 		let pos = pmmr::insertion_to_pmmr_index(height + 1);
 		if let Some(hash) = self.get_header_hash(pos) {
 			let header = self.batch.get_block_header(&hash)?;
@@ -1227,8 +1227,9 @@ impl<'a> Extension<'a> {
 	/// from the respective MMRs.
 	/// For a significantly faster way of validating full kernel sums see BlockSums.
 	pub fn validate_kernel_sums(&self) -> Result<((Commitment, Commitment)), Error> {
+		let genesis = self.get_header_by_height(0)?;
 		let (utxo_sum, kernel_sum) = self.verify_kernel_sums(
-			self.header.total_overage(),
+			self.header.total_overage(genesis.kernel_mmr_size > 0),
 			self.header.total_kernel_offset(),
 		)?;
 		Ok((utxo_sum, kernel_sum))

chain/tests/mine_simple_chain.rs

@@ -31,8 +31,9 @@ use chain::Chain;
 use core::core::hash::Hashed;
 use core::core::verifier_cache::LruVerifierCache;
 use core::core::{Block, BlockHeader, OutputFeatures, OutputIdentifier, Transaction};
+use core::genesis;
 use core::global::ChainTypes;
-use core::libtx::{self, build};
+use core::libtx::{self, build, reward};
 use core::pow::Difficulty;
 use core::{consensus, global, pow};
 use keychain::{ExtKeychain, ExtKeychainPath, Keychain};
@@ -60,14 +61,51 @@ fn setup(dir_name: &str, genesis: Block) -> Chain {
 #[test]
 fn mine_empty_chain() {
 	global::set_mining_mode(ChainTypes::AutomatedTesting);
-	let chain = setup(".grin", pow::mine_genesis_block().unwrap());
-	let keychain = ExtKeychain::from_random_seed().unwrap();
+	let keychain = keychain::ExtKeychain::from_random_seed().unwrap();
+	mine_some_on_top(".grin", pow::mine_genesis_block().unwrap(), &keychain);
+}
+
+#[test]
+fn mine_genesis_reward_chain() {
+	global::set_mining_mode(ChainTypes::AutomatedTesting);
+
+	// add coinbase data from the dev genesis block
+	let mut genesis = genesis::genesis_dev();
+	let keychain = keychain::ExtKeychain::from_random_seed().unwrap();
+	let key_id = keychain::ExtKeychain::derive_key_id(0, 1, 0, 0, 0);
+	let reward = reward::output(&keychain, &key_id, 0, 0).unwrap();
+	genesis = genesis.with_reward(reward.0, reward.1);
+
+	{
+		// setup a tmp chain to hande tx hashsets
+		let tmp_chain = setup(".grin.tmp", pow::mine_genesis_block().unwrap());
+		tmp_chain.set_txhashset_roots(&mut genesis).unwrap();
+		genesis.header.output_mmr_size = 1;
+		genesis.header.kernel_mmr_size = 1;
+	}
+
+	// get a valid PoW
+	pow::pow_size(
+		&mut genesis.header,
+		Difficulty::unit(),
+		global::proofsize(),
+		global::min_edge_bits(),
+	).unwrap();
+
+	mine_some_on_top(".grin.genesis", genesis, &keychain);
+}
+
+fn mine_some_on_top<K>(dir: &str, genesis: Block, keychain: &K)
+where
+	K: Keychain,
+{
+	let chain = setup(dir, genesis);
 
 	for n in 1..4 {
 		let prev = chain.head_header().unwrap();
 		let next_header_info = consensus::next_difficulty(1, chain.difficulty_iter());
 		let pk = ExtKeychainPath::new(1, n as u32, 0, 0, 0).to_identifier();
-		let reward = libtx::reward::output(&keychain, &pk, 0, prev.height).unwrap();
+		let reward = libtx::reward::output(keychain, &pk, 0, prev.height).unwrap();
 		let mut b =
 			core::core::Block::new(&prev, vec![], next_header_info.clone().difficulty, reward)
 				.unwrap();

core/src/core/block.rs

@@ -262,8 +262,13 @@ impl BlockHeader {
 
 	/// The "total overage" to use when verifying the kernel sums for a full
 	/// chain state. For a full chain state this is 0 - (height * reward).
-	pub fn total_overage(&self) -> i64 {
-		((self.height * REWARD) as i64).checked_neg().unwrap_or(0)
+	pub fn total_overage(&self, genesis_had_reward: bool) -> i64 {
+		let mut reward_count = self.height;
+		if genesis_had_reward {
+			reward_count += 1;
+		}
+
+		((reward_count * REWARD) as i64).checked_neg().unwrap_or(0)
 	}
 
 	/// Total kernel offset for the chain state up to and including this block.
@@ -358,7 +363,7 @@ impl Block {
 		reward_output: (Output, TxKernel),
 	) -> Result<Block, Error> {
 		let mut block =
-			Block::with_reward(prev, txs, reward_output.0, reward_output.1, difficulty)?;
+			Block::from_reward(prev, txs, reward_output.0, reward_output.1, difficulty)?;
 
 		// Now set the pow on the header so block hashing works as expected.
 		{
@@ -421,7 +426,7 @@ impl Block {
 	/// Builds a new block ready to mine from the header of the previous block,
 	/// a vector of transactions and the reward information. Checks
 	/// that all transactions are valid and calculates the Merkle tree.
-	pub fn with_reward(
+	pub fn from_reward(
 		prev: &BlockHeader,
 		txs: Vec<Transaction>,
 		reward_out: Output,
@@ -461,6 +466,14 @@ impl Block {
 		}.cut_through()
 	}
 
+	/// Consumes this block and returns a new block with the coinbase output
+	/// and kernels added
+	pub fn with_reward(mut self, reward_out: Output, reward_kern: TxKernel) -> Block {
+		self.body.outputs.push(reward_out);
+		self.body.kernels.push(reward_kern);
+		self
+	}
+
 	/// Get inputs
 	pub fn inputs(&self) -> &Vec<Input> {
 		&self.body.inputs

servers/src/mining/mine_block.rs

@@ -120,7 +120,7 @@ fn build_block(
 	};
 
 	let (output, kernel, block_fees) = get_coinbase(wallet_listener_url, block_fees)?;
-	let mut b = core::Block::with_reward(&head, txs, output, kernel, difficulty.difficulty)?;
+	let mut b = core::Block::from_reward(&head, txs, output, kernel, difficulty.difficulty)?;
 
 	// making sure we're not spending time mining a useless block
 	b.validate(&head.total_kernel_offset, verifier_cache)?;