grin/wallet/src/receiver.rs

// Copyright 2017 The Grin Developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Provides the JSON/HTTP API for wallets to receive payments. Because
//! receiving money in MimbleWimble requires an interactive exchange, a
//! wallet server that's running at all time is required in many cases.
//!
//! The API looks like this:
//!
//! POST /v1/wallet/receive
//! > {
//! >   "amount": 10,
//! >   "blind_sum": "a12b7f...",
//! >   "tx": "f083de...",
//! > }
//!
//! < {
//! <   "tx": "f083de...",
//! <   "status": "ok"
//! < }
//!
//! POST /v1/wallet/finalize
//! > {
//! >   "tx": "f083de...",
//! > }
//!
//! POST /v1/wallet/receive_coinbase
//! > {
//! >   "amount": 1,
//! > }
//!
//! < {
//! <   "output": "8a90bc...",
//! <   "kernel": "f083de...",
//! < }
//!
//! Note that while at this point the finalize call is completely unecessary, a
//! double-exchange will be required as soon as we support Schnorr signatures.
//! So we may as well have it in place already.

use core::consensus::reward;
use core::core::{Block, Transaction, TxKernel, Output, build};
use core::ser;
use api::{self, ApiEndpoint, Operation, ApiResult};
use keychain::{BlindingFactor, Identifier, Keychain};
use types::*;
use util;
use util::LOGGER;

/// Dummy wrapper for the hex-encoded serialized transaction.
#[derive(Serialize, Deserialize)]
pub struct TxWrapper {
	pub tx_hex: String,
}

/// Receive an already well formed JSON transaction issuance and finalize the
/// transaction, adding our receiving output, to broadcast to the rest of the
/// network.
pub fn receive_json_tx(
	config: &WalletConfig,
	keychain: &Keychain,
	partial_tx_str: &str,
) -> Result<(), Error> {
	let (amount, blinding, partial_tx) = partial_tx_from_json(keychain, partial_tx_str)?;
	let final_tx = receive_transaction(config, keychain, amount, blinding, partial_tx)?;
	let tx_hex = util::to_hex(ser::ser_vec(&final_tx).unwrap());

	let url = format!("{}/v1/pool/push", config.check_node_api_http_addr.as_str());
	let _: () = api::client::post(url.as_str(), &TxWrapper { tx_hex: tx_hex })
		.map_err(|e| Error::Node(e))?;
	Ok(())
}

/// Component used to receive coins, implements all the receiving end of the
/// wallet REST API as well as some of the command-line operations.
#[derive(Clone)]
pub struct WalletReceiver {
	pub keychain: Keychain,
	pub config: WalletConfig,
}

impl ApiEndpoint for WalletReceiver {
	type ID = String;
	type T = String;
	type OP_IN = WalletReceiveRequest;
	type OP_OUT = CbData;

	fn operations(&self) -> Vec<Operation> {
		vec![Operation::Custom("receive_json_tx".to_string())]
	}

	fn operation(&self, op: String, input: WalletReceiveRequest) -> ApiResult<CbData> {
		match op.as_str() {
			"receive_json_tx" => {
				match input {
					WalletReceiveRequest::PartialTransaction(partial_tx_str) => {
						debug!(
							LOGGER,
							"Operation {} with transaction {}",
							op,
							&partial_tx_str,
						);
						receive_json_tx(&self.config, &self.keychain, &partial_tx_str)
							.map_err(|e| {
								api::Error::Internal(
									format!("Error processing partial transaction: {:?}", e),
								)
							})
							.unwrap();

						// TODO: Return emptiness for now, should be a proper enum return type
						Ok(CbData {
							output: String::from(""),
							kernel: String::from(""),
							key_id: String::from(""),
						})
					}
					_ => Err(api::Error::Argument(format!("Incorrect request data: {}", op))),
				}
			}
			_ => Err(api::Error::Argument(format!("Unknown operation: {}", op))),
		}
	}
}

// Read wallet data without acquiring the write lock.
fn retrieve_existing_key(
	config: &WalletConfig,
	key_id: Identifier,
) -> Result<(Identifier, u32), Error> {
	let res = WalletData::read_wallet(&config.data_file_dir, |wallet_data| {
		if let Some(existing) = wallet_data.get_output(&key_id) {
			let key_id = existing.key_id.clone();
			let derivation = existing.n_child;
			(key_id, derivation)
		} else {
			panic!("should never happen");
		}
	})?;
	Ok(res)
}

fn next_available_key(
	config: &WalletConfig,
	keychain: &Keychain,
) -> Result<(Identifier, u32), Error> {
	let res = WalletData::read_wallet(&config.data_file_dir, |wallet_data| {
		let root_key_id = keychain.root_key_id();
		let derivation = wallet_data.next_child(root_key_id.clone());
		let key_id = keychain.derive_key_id(derivation).unwrap();
		(key_id, derivation)
	})?;
	Ok(res)
}

/// Build a coinbase output and the corresponding kernel
pub fn receive_coinbase(
	config: &WalletConfig,
	keychain: &Keychain,
	block_fees: &BlockFees
) -> Result<(Output, TxKernel, BlockFees), Error> {
	let root_key_id = keychain.root_key_id();
	let key_id = block_fees.key_id();

	let (key_id, derivation) = match key_id {
		Some(key_id) => retrieve_existing_key(config, key_id)?,
		None => next_available_key(config, keychain)?,
	};

	// Now acquire the wallet lock and write the new output.
	WalletData::with_wallet(&config.data_file_dir, |wallet_data| {
		// track the new output and return the stuff needed for reward
		wallet_data.add_output(OutputData {
			root_key_id: root_key_id.clone(),
			key_id: key_id.clone(),
			n_child: derivation,
			value: reward(block_fees.fees),
			status: OutputStatus::Unconfirmed,
			height: 0,
			lock_height: 0,
			is_coinbase: true,
		});
	})?;

	debug!(
		LOGGER,
		"Received coinbase and built candidate output - {:?}, {:?}, {}",
		root_key_id.clone(),
		key_id.clone(),
		derivation,
	);

	debug!(LOGGER, "block_fees - {:?}", block_fees);

	let mut block_fees = block_fees.clone();
	block_fees.key_id = Some(key_id.clone());

	debug!(LOGGER, "block_fees updated - {:?}", block_fees);

	let (out, kern) = Block::reward_output(
		&keychain,
		&key_id,
		block_fees.fees,
	)?;
	Ok((out, kern, block_fees))
}

/// Builds a full transaction from the partial one sent to us for transfer
fn receive_transaction(
	config: &WalletConfig,
	keychain: &Keychain,
	amount: u64,
	blinding: BlindingFactor,
	partial: Transaction,
) -> Result<Transaction, Error> {
	let root_key_id = keychain.root_key_id();

	let (key_id, derivation) = next_available_key(config, keychain)?;

	// double check the fee amount included in the partial tx
	// we don't necessarily want to just trust the sender
	// we could just overwrite the fee here (but we won't) due to the ecdsa sig
	let fee = tx_fee(partial.inputs.len(), partial.outputs.len() + 1, None);
	if fee != partial.fee {
		return Err(Error::FeeDispute {
			sender_fee: partial.fee,
			recipient_fee: fee,
		});
	}

	let out_amount = amount - fee;

	let (tx_final, _) = build::transaction(vec![
		build::initial_tx(partial),
		build::with_excess(blinding),
		build::output(out_amount, key_id.clone()),
		// build::with_fee(fee_amount),
	], keychain)?;

	// make sure the resulting transaction is valid (could have been lied to on excess).
	tx_final.validate(&keychain.secp())?;

	// operate within a lock on wallet data
	WalletData::with_wallet(&config.data_file_dir, |wallet_data| {
		wallet_data.add_output(OutputData {
			root_key_id: root_key_id.clone(),
			key_id: key_id.clone(),
			n_child: derivation,
			value: out_amount,
			status: OutputStatus::Unconfirmed,
			height: 0,
			lock_height: 0,
			is_coinbase: false,
		});
	})?;

	debug!(
		LOGGER,
		"Received txn and built output - {:?}, {:?}, {}",
		root_key_id.clone(),
		key_id.clone(),
		derivation,
	);

	Ok(tx_final)
}