Merge pull request #3 from scilio/main

Milestone 2

.gitignore

@@ -5,3 +5,5 @@ target
 *.iml
 .idea/
 .vscode/
+
+mwixnet-config.toml

Cargo.toml

@@ -10,19 +10,35 @@ blake2 = { package = "blake2-rfc", version = "0.2"}
 byteorder = "1"
 bytes = "0.5.6"
 chacha20 = "0.8.1"
+clap = { version = "2.33", features = ["yaml"] }
+dirs = "2.0"
 failure = "0.1.8"
 futures = "0.3"
-hmac = { version = "0.11.0", features = ["std"]}
+hmac = { version = "0.12.0", features = ["std"]}
 hyper = { version = "0.14", features = ["full"] }
+itertools = { version = "0.10.3"}
 jsonrpc-core = "18.0"
 jsonrpc-derive = "18.0"
 jsonrpc-http-server = "18.0"
 lazy_static = "1"
+pbkdf2 = "0.8.0"
 rand = "0.8.4"
+ring = "0.16"
+rpassword = "4.0"
 serde = { version = "1", features= ["derive"]}
 serde_derive = "1"
 serde_json = "1"
-sha2 = "0.9.8"
+sha2 = "0.10.0"
+thiserror = "1.0.31"
 tokio = { version = "1", features = ["full"] }
+toml = "0.5"
 grin_secp256k1zkp = { version = "0.7.11", features = ["bullet-proof-sizing"]}
 grin_util = "5"
+grin_api = { git = "https://github.com/mimblewimble/grin", version = "5.2.0-alpha.1" }
+grin_core = { git = "https://github.com/mimblewimble/grin", version = "5.2.0-alpha.1" }
+grin_chain = { git = "https://github.com/mimblewimble/grin", version = "5.2.0-alpha.1" }
+grin_keychain = { git = "https://github.com/mimblewimble/grin", version = "5.2.0-alpha.1" }
+grin_servers = { git = "https://github.com/mimblewimble/grin", version = "5.2.0-alpha.1" }
+grin_wallet_api = { git = "https://github.com/mimblewimble/grin-wallet", branch = "master" }
+grin_wallet_impls = { git = "https://github.com/mimblewimble/grin-wallet", branch = "master" }
+grin_wallet_libwallet = { git = "https://github.com/mimblewimble/grin-wallet", branch = "master" }

README.md

@@ -3,6 +3,21 @@ This is an implementation of @tromp's [CoinSwap Proposal](https://forum.grin.mw/
 
 A set of n CoinSwap servers (node<sub>i</sub> with i=1...n) are agreed upon in advance. They each have a known public key.
 
+### Setup
+#### init-config
+To setup a new server, run `mwixnet init-config`. Then enter a password for the server key when prompted.
+
+This will generate a key for the server and then create a new config file named `mwixnet-config.toml` in the current working directory.
+The configuration file will contain the private key of the server encrypted with the server password you provided.
+
+**Back this config file up! It's the only copy of the server's private key!**
+
+#### Wallet
+A grin-wallet account must be created for receiving extra mwixnet fees. The wallet's owner API should be available (run `grin-wallet owner_api`).
+
+### Usage
+With your wallet and fully synced node both online and listening at the addresses configured, the mwixnet server can be started by running `mwixnet` and providing the server key password and wallet password when prompted.
+
 ### SWAP API
 The first CoinSwap server (n<sub>1</sub>) provides the `swap` API, publicly available for use by GRIN wallets.
 
@@ -11,12 +26,13 @@ The first CoinSwap server (n<sub>1</sub>) provides the `swap` API, publicly avai
 **params:**
 ```
 [{
-    "comsig": "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f",
-    "msg": "00010203",
+    "comsig": "0835f4b8b9cd286c9e35475f575c3e4ae71ceb4ff36598504662627afd628a17d6ba7dedb1aa4c47f0fabad026b76fc86d06f3bef8d0621b8ac4601d4b1b98401586ca3374a401508f32049212478ae91cfa474dfaa5ef2c3dd559d5a292e02334",
     "onion": {
-        "commit": "0967593792bc958cd73848c0b948ecab2c6e996ab3c550d462fe41359e447b651f",
-        "data": ["3719e5fba260c71a5a4bcf9d9caa58cd5dc49531388782fae7699c6fa6b30b09fe42"],
-        "pubkey": "020dd38a220280f14515f6901a3a366cb7b87630814e4b68b3189a32df964961e5"
+        "commit": "099a8922343f242dd3da29935ba5bbc7e38bf68eccfb8c96aec87aec0535199139",
+        "data":[
+            "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"
+        ],
+        "pubkey": "033946e6a495e7278027b38be3d500cfc23d3e0836f1b7e24513841437f316ccb0"
     }
 }]
 ```

mwixnet.yml

@@ -0,0 +1,39 @@
+name: mwixnet
+about: MWixnet CoinSwap Server
+author: scilio
+
+args:
+  - config_file:
+      help: Path to load/save the mwixnet-config.toml configuration file
+      short: c
+      long: config_file
+      takes_value: true
+  - grin_node_url:
+      help: Api address of running GRIN node on which to check inputs and post transactions
+      short: n
+      long: grin_node_url
+      takes_value: true
+  - grin_node_secret_path:
+      help: Path to a file containing the secret for the GRIN node api
+      long: grin_node_secret_path
+      takes_value: true
+  - wallet_owner_url:
+      help: Api address of running wallet owner listener
+      short: l
+      long: wallet_owner_url
+      takes_value: true
+  - wallet_owner_secret_path:
+      help: Path to a file containing the secret for the wallet owner api
+      long: wallet_owner_secret_path
+      takes_value: true
+  - wallet_pass:
+      help: The wallet's password
+      long: wallet_pass
+      takes_value: true
+  - bind_addr:
+      help: Address to bind the rpc server to (e.g. 0.0.0.0:3000)
+      long: bind_addr
+      takes_value: true
+subcommands:
+  - init-config:
+      about: Writes a new configuration file

rustfmt.toml

@@ -0,0 +1,2 @@
+hard_tabs = true
+edition = "2021"

src/config.rs

@@ -0,0 +1,265 @@
+use crate::error::{self, Result};
+use crate::secp::SecretKey;
+
+use core::num::NonZeroU32;
+use grin_util::{file, ToHex, ZeroingString};
+use rand::{thread_rng, Rng};
+use ring::{aead, pbkdf2};
+use serde_derive::{Deserialize, Serialize};
+use std::fs::File;
+use std::io::prelude::*;
+use std::net::SocketAddr;
+use std::path::PathBuf;
+
+const GRIN_HOME: &str = ".grin";
+const CHAIN_NAME: &str = "main";
+const NODE_API_SECRET_FILE_NAME: &str = ".api_secret";
+const WALLET_OWNER_API_SECRET_FILE_NAME: &str = ".owner_api_secret";
+
+/// The decrypted server config to be passed around and used by the rest of the mwixnet code
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub struct ServerConfig {
+	/// private key used by the server to decrypt onion packets
+	pub key: SecretKey,
+	/// interval (in seconds) to wait before each mixing round
+	pub interval_s: u32,
+	/// socket address the server listener should bind to
+	pub addr: SocketAddr,
+	/// foreign api address of the grin node
+	pub grin_node_url: SocketAddr,
+	/// path to file containing api secret for the grin node
+	pub grin_node_secret_path: Option<String>,
+	/// owner api address of the grin wallet
+	pub wallet_owner_url: SocketAddr,
+	/// path to file containing secret for the grin wallet's owner api
+	pub wallet_owner_secret_path: Option<String>,
+}
+
+impl ServerConfig {
+	pub fn node_api_secret(&self) -> Option<String> {
+		file::get_first_line(self.grin_node_secret_path.clone())
+	}
+
+	pub fn wallet_owner_api_secret(&self) -> Option<String> {
+		file::get_first_line(self.wallet_owner_secret_path.clone())
+	}
+}
+
+/// Encrypted server key, for storing on disk and decrypting with a password.
+/// Includes a salt used by key derivation and a nonce used when sealing the encrypted data.
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq)]
+struct EncryptedServerKey {
+	encrypted_key: String,
+	salt: String,
+	nonce: String,
+}
+
+impl EncryptedServerKey {
+	/// Generates a random salt for pbkdf2 key derivation and a random nonce for aead sealing.
+	/// Then derives an encryption key from the password and salt. Finally, it encrypts and seals
+	/// the server key with chacha20-poly1305 using the derived key and random nonce.
+	pub fn from_secret_key(
+		server_key: &SecretKey,
+		password: &ZeroingString,
+	) -> Result<EncryptedServerKey> {
+		let salt: [u8; 8] = thread_rng().gen();
+		let password = password.as_bytes();
+		let mut key = [0; 32];
+		pbkdf2::derive(
+			pbkdf2::PBKDF2_HMAC_SHA512,
+			NonZeroU32::new(100).unwrap(),
+			&salt,
+			password,
+			&mut key,
+		);
+		let content = server_key.0.to_vec();
+		let mut enc_bytes = content;
+
+		let unbound_key = aead::UnboundKey::new(&aead::CHACHA20_POLY1305, &key).unwrap();
+		let sealing_key: aead::LessSafeKey = aead::LessSafeKey::new(unbound_key);
+		let nonce: [u8; 12] = thread_rng().gen();
+		let aad = aead::Aad::from(&[]);
+		let _ = sealing_key
+			.seal_in_place_append_tag(
+				aead::Nonce::assume_unique_for_key(nonce),
+				aad,
+				&mut enc_bytes,
+			)
+			.map_err(|e| {
+				error::ErrorKind::SaveConfigError(format!(
+					"Failure while encrypting server key: {}",
+					e
+				))
+			})?;
+
+		Ok(EncryptedServerKey {
+			encrypted_key: enc_bytes.to_hex(),
+			salt: salt.to_hex(),
+			nonce: nonce.to_hex(),
+		})
+	}
+
+	/// Decrypt the server secret key using the provided password.
+	pub fn decrypt(&self, password: &str) -> Result<SecretKey> {
+		let mut encrypted_seed = grin_util::from_hex(&self.encrypted_key.clone())
+			.map_err(|_| error::ErrorKind::LoadConfigError("Seed not valid hex".to_string()))?;
+		let salt = grin_util::from_hex(&self.salt.clone())
+			.map_err(|_| error::ErrorKind::LoadConfigError("Salt not valid hex".to_string()))?;
+		let nonce = grin_util::from_hex(&self.nonce.clone())
+			.map_err(|_| error::ErrorKind::LoadConfigError("Nonce not valid hex".to_string()))?;
+		let password = password.as_bytes();
+		let mut key = [0; 32];
+		pbkdf2::derive(
+			pbkdf2::PBKDF2_HMAC_SHA512,
+			NonZeroU32::new(100).unwrap(),
+			&salt,
+			password,
+			&mut key,
+		);
+
+		let mut n = [0u8; 12];
+		n.copy_from_slice(&nonce[0..12]);
+		let unbound_key = aead::UnboundKey::new(&aead::CHACHA20_POLY1305, &key).unwrap();
+		let opening_key: aead::LessSafeKey = aead::LessSafeKey::new(unbound_key);
+		let aad = aead::Aad::from(&[]);
+		let _ = opening_key
+			.open_in_place(
+				aead::Nonce::assume_unique_for_key(n),
+				aad,
+				&mut encrypted_seed,
+			)
+			.map_err(|e| {
+				error::ErrorKind::LoadConfigError(format!("Error decrypting seed: {}", e))
+			})?;
+
+		for _ in 0..aead::AES_256_GCM.tag_len() {
+			encrypted_seed.pop();
+		}
+
+		let secp = secp256k1zkp::Secp256k1::new();
+		let decrypted = SecretKey::from_slice(&secp, &encrypted_seed).map_err(|_| {
+			error::ErrorKind::LoadConfigError("Decrypted key not valid".to_string())
+		})?;
+		Ok(decrypted)
+	}
+}
+
+/// The config attributes saved to disk
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+struct RawConfig {
+	encrypted_key: String,
+	salt: String,
+	nonce: String,
+	interval_s: u32,
+	addr: SocketAddr,
+	grin_node_url: SocketAddr,
+	grin_node_secret_path: Option<String>,
+	wallet_owner_url: SocketAddr,
+	wallet_owner_secret_path: Option<String>,
+}
+
+/// Writes the server config to the config_path given, encrypting the server_key first.
+pub fn write_config(
+	config_path: &PathBuf,
+	server_config: &ServerConfig,
+	password: &ZeroingString,
+) -> Result<()> {
+	let encrypted = EncryptedServerKey::from_secret_key(&server_config.key, &password)?;
+
+	let raw_config = RawConfig {
+		encrypted_key: encrypted.encrypted_key,
+		salt: encrypted.salt,
+		nonce: encrypted.nonce,
+		interval_s: server_config.interval_s,
+		addr: server_config.addr,
+		grin_node_url: server_config.grin_node_url,
+		grin_node_secret_path: server_config.grin_node_secret_path.clone(),
+		wallet_owner_url: server_config.wallet_owner_url,
+		wallet_owner_secret_path: server_config.wallet_owner_secret_path.clone(),
+	};
+	let encoded: String = toml::to_string(&raw_config).map_err(|e| {
+		error::ErrorKind::SaveConfigError(format!("Error while encoding config as toml: {}", e))
+	})?;
+
+	let mut file = File::create(config_path)?;
+	file.write_all(encoded.as_bytes()).map_err(|e| {
+		error::ErrorKind::SaveConfigError(format!("Error while writing config to file: {}", e))
+	})?;
+
+	Ok(())
+}
+
+/// Reads the server config from the config_path given and decrypts it with the provided password.
+pub fn load_config(config_path: &PathBuf, password: &ZeroingString) -> Result<ServerConfig> {
+	let contents = std::fs::read_to_string(config_path).map_err(|e| {
+		error::ErrorKind::LoadConfigError(format!(
+			"Unable to read server config. Perform init-config or pass in config path.\nError: {}",
+			e
+		))
+	})?;
+	let raw_config: RawConfig =
+		toml::from_str(&contents).map_err(|e| error::ErrorKind::LoadConfigError(e.to_string()))?;
+
+	let encrypted_key = EncryptedServerKey {
+		encrypted_key: raw_config.encrypted_key,
+		salt: raw_config.salt,
+		nonce: raw_config.nonce,
+	};
+	let secret_key = encrypted_key.decrypt(&password)?;
+
+	Ok(ServerConfig {
+		key: secret_key,
+		interval_s: raw_config.interval_s,
+		addr: raw_config.addr,
+		grin_node_url: raw_config.grin_node_url,
+		grin_node_secret_path: raw_config.grin_node_secret_path,
+		wallet_owner_url: raw_config.wallet_owner_url,
+		wallet_owner_secret_path: raw_config.wallet_owner_secret_path,
+	})
+}
+
+pub fn get_grin_path() -> PathBuf {
+	let mut grin_path = match dirs::home_dir() {
+		Some(p) => p,
+		None => PathBuf::new(),
+	};
+	grin_path.push(GRIN_HOME);
+	grin_path.push(CHAIN_NAME);
+	grin_path
+}
+
+pub fn node_secret_path() -> PathBuf {
+	let mut path = get_grin_path();
+	path.push(NODE_API_SECRET_FILE_NAME);
+	path
+}
+
+pub fn wallet_owner_secret_path() -> PathBuf {
+	let mut path = get_grin_path();
+	path.push(WALLET_OWNER_API_SECRET_FILE_NAME);
+	path
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use crate::secp;
+
+	#[test]
+	fn server_key_encrypt() {
+		let password = ZeroingString::from("password");
+		let server_key = secp::random_secret();
+		let mut enc_key = EncryptedServerKey::from_secret_key(&server_key, &password).unwrap();
+		let decrypted_key = enc_key.decrypt(&password).unwrap();
+		assert_eq!(server_key, decrypted_key);
+
+		// Wrong password
+		let decrypted_key = enc_key.decrypt("wrongpass");
+		assert!(decrypted_key.is_err());
+
+		// Wrong nonce
+		enc_key.nonce = "wrongnonce".to_owned();
+		let decrypted_key = enc_key.decrypt(&password);
+		assert!(decrypted_key.is_err());
+	}
+}

src/error.rs

@@ -1,4 +1,5 @@
 use failure::{self, Context, Fail};
+use grin_wallet_libwallet as libwallet;
 use std::fmt::{self, Display};
 use std::io;
 
@@ -9,13 +10,11 @@ pub struct Error {
 }
 
 pub type Result<T> = std::result::Result<T, Error>;
+pub type StdResult<T, E> = std::result::Result<T, E>;
 
-#[derive(Clone, Debug, Eq, Fail, PartialEq)]
 /// MWixnet error types
+#[derive(Clone, Debug, Eq, Fail, PartialEq)]
 pub enum ErrorKind {
-    /// Unsupported payload version
-    #[fail(display = "Unsupported Payload Version")]
-    UnsupportedPayload,
 	/// Error from secp256k1-zkp library
 	#[fail(display = "Secp Error")]
 	SecpError,
@@ -23,33 +22,35 @@ pub enum ErrorKind {
 	#[fail(display = "InvalidKeyLength")]
 	InvalidKeyLength,
 	/// Wraps an io error produced when reading or writing
-    #[fail(display = "IOError")]
-    IOErr(
-        String,
-        io::ErrorKind,
-    ),
-    /// Expected a given value that wasn't found
-    #[fail(display = "UnexpectedData")]
-    UnexpectedData {
-        /// What we wanted
-        expected: Vec<u8>,
-        /// What we got
-        received: Vec<u8>,
-    },
+	#[fail(display = "IO Error: {}", _0)]
+	IOErr(String, io::ErrorKind),
 	/// Data wasn't in a consumable format
 	#[fail(display = "CorruptedData")]
 	CorruptedData,
-    /// Incorrect number of elements (when deserializing a vec via read_multi say).
-    #[fail(display = "CountError")]
-    CountError,
-    /// When asked to read too much data
-    #[fail(display = "TooLargeReadErr")]
-    TooLargeReadErr,
+	/// Error from grin's api crate
+	#[fail(display = "GRIN API Error: {}", _0)]
+	GrinApiError(String),
+	/// Error from grin core
+	#[fail(display = "GRIN Core Error: {}", _0)]
+	GrinCoreError(String),
+	/// Error from grin-wallet's libwallet
+	#[fail(display = "libwallet error: {}", _0)]
+	LibWalletError(String),
+	/// Error from serde-json
+	#[fail(display = "serde json error: {}", _0)]
+	SerdeJsonError(String),
+	/// Error from invalid signature
+	#[fail(display = "invalid signature")]
+	InvalidSigError,
+	/// Error while saving config
+	#[fail(display = "save config error: {}", _0)]
+	SaveConfigError(String),
+	/// Error while loading config
+	#[fail(display = "load config error: {}", _0)]
+	LoadConfigError(String),
 }
 
-impl std::error::Error for Error {
-    
-}
+impl std::error::Error for Error {}
 
 impl From<io::Error> for Error {
 	fn from(e: io::Error) -> Error {
@@ -63,6 +64,14 @@ impl From<io::ErrorKind> for Error {
 	}
 }
 
+impl From<grin_core::ser::Error> for Error {
+	fn from(e: grin_core::ser::Error) -> Error {
+		Error {
+			inner: Context::new(ErrorKind::GrinCoreError(e.to_string())),
+		}
+	}
+}
+
 impl Display for Error {
 	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 		Display::fmt(&self.inner, f)
@@ -70,8 +79,10 @@ impl Display for Error {
 }
 
 impl Error {
-    pub fn kind(&self) -> ErrorKind {
-        self.inner.get_context().clone()
+	pub fn new(kind: ErrorKind) -> Error {
+		Error {
+			inner: Context::new(kind),
+		}
 	}
 
 	pub fn message(&self) -> String {
@@ -101,10 +112,50 @@ impl From<secp256k1zkp::Error> for Error {
 	}
 }
 
-impl From<hmac::crypto_mac::InvalidKeyLength> for Error {
-    fn from(_error: hmac::crypto_mac::InvalidKeyLength) -> Error {
+impl From<hmac::digest::InvalidLength> for Error {
+	fn from(_error: hmac::digest::InvalidLength) -> Error {
 		Error {
 			inner: Context::new(ErrorKind::InvalidKeyLength),
 		}
 	}
 }
+
+impl From<grin_api::Error> for Error {
+	fn from(e: grin_api::Error) -> Error {
+		Error {
+			inner: Context::new(ErrorKind::GrinApiError(e.to_string())),
+		}
+	}
+}
+
+impl From<grin_api::json_rpc::Error> for Error {
+	fn from(e: grin_api::json_rpc::Error) -> Error {
+		Error {
+			inner: Context::new(ErrorKind::GrinApiError(e.to_string())),
+		}
+	}
+}
+
+impl From<grin_core::core::transaction::Error> for Error {
+	fn from(e: grin_core::core::transaction::Error) -> Error {
+		Error {
+			inner: Context::new(ErrorKind::GrinCoreError(e.to_string())),
+		}
+	}
+}
+
+impl From<libwallet::Error> for Error {
+	fn from(e: libwallet::Error) -> Error {
+		Error {
+			inner: Context::new(ErrorKind::LibWalletError(e.to_string())),
+		}
+	}
+}
+
+impl From<serde_json::Error> for Error {
+	fn from(e: serde_json::Error) -> Error {
+		Error {
+			inner: Context::new(ErrorKind::SerdeJsonError(e.to_string())),
+		}
+	}
+}

src/main.rs

@@ -1,29 +1,190 @@
-use server::ServerConfig;
+use config::ServerConfig;
+use node::HttpGrinNode;
+use wallet::HttpWallet;
+
+use clap::App;
+use grin_util::{StopState, ZeroingString};
+use rpassword;
+use std::path::PathBuf;
+use std::sync::Arc;
+use tokio::runtime::Runtime;
 
 #[macro_use]
-extern crate lazy_static;
+extern crate clap;
 
+mod config;
 mod error;
+mod node;
 mod onion;
+mod rpc;
 mod secp;
-mod ser;
 mod server;
 mod types;
+mod wallet;
 
-fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let secret_key = secp::insecure_rand_secret()?; // todo - load from encrypted key file
-    let server_config = ServerConfig {
-        key: secret_key,
-        addr: "127.0.0.1:3000".parse().unwrap(),
-        is_first: true
+const DEFAULT_INTERVAL: u32 = 12 * 60 * 60;
+
+fn main() {
+	real_main().unwrap();
+	std::process::exit(0);
+}
+
+fn real_main() -> Result<(), Box<dyn std::error::Error>> {
+	let yml = load_yaml!("../mwixnet.yml");
+	let args = App::from_yaml(yml).get_matches();
+
+	let config_path = match args.value_of("config_file") {
+		Some(path) => PathBuf::from(path),
+		None => {
+			let mut grin_path = config::get_grin_path();
+			grin_path.push("mwixnet-config.toml");
+			grin_path
+		}
 	};
 
-    let shutdown_signal = async move {
-        // Wait for the CTRL+C signal
+	let round_time = args
+		.value_of("round_time")
+		.map(|t| t.parse::<u32>().unwrap());
+	let bind_addr = args.value_of("bind_addr");
+	let grin_node_url = args.value_of("grin_node_url");
+	let grin_node_secret_path = args.value_of("grin_node_secret_path");
+	let wallet_owner_url = args.value_of("wallet_owner_url");
+	let wallet_owner_secret_path = args.value_of("wallet_owner_secret_path");
+
+	// Write a new config file if init-config command is supplied
+	if let ("init-config", Some(_)) = args.subcommand() {
+		if config_path.exists() {
+			panic!(
+				"Config file already exists at {}",
+				config_path.to_string_lossy()
+			);
+		}
+
+		let server_config = ServerConfig {
+			key: secp::random_secret(),
+			interval_s: round_time.unwrap_or(DEFAULT_INTERVAL),
+			addr: bind_addr.unwrap_or("0.0.0.0:3000").parse()?,
+			grin_node_url: grin_node_url.unwrap_or("127.0.0.1:3413").parse()?,
+			grin_node_secret_path: match grin_node_secret_path {
+				Some(p) => Some(p.to_owned()),
+				None => config::node_secret_path().to_str().map(|p| p.to_owned()),
+			},
+			wallet_owner_url: wallet_owner_url.unwrap_or("127.0.0.1:3420").parse()?,
+			wallet_owner_secret_path: match wallet_owner_secret_path {
+				Some(p) => Some(p.to_owned()),
+				None => config::wallet_owner_secret_path()
+					.to_str()
+					.map(|p| p.to_owned()),
+			},
+		};
+
+		let password = prompt_password_confirm();
+		config::write_config(&config_path, &server_config, &password)?;
+		println!(
+			"Config file written to {:?}. Please back this file up in a safe place.",
+			config_path
+		);
+		return Ok(());
+	}
+
+	let password = prompt_password();
+	let mut server_config = config::load_config(&config_path, &password)?;
+
+	// Override bind_addr, if supplied
+	if let Some(bind_addr) = bind_addr {
+		server_config.addr = bind_addr.parse()?;
+	}
+
+	// Override grin_node_url, if supplied
+	if let Some(grin_node_url) = grin_node_url {
+		server_config.grin_node_url = grin_node_url.parse()?;
+	}
+
+	// Override grin_node_secret_path, if supplied
+	if let Some(grin_node_secret_path) = grin_node_secret_path {
+		server_config.grin_node_secret_path = Some(grin_node_secret_path.to_owned());
+	}
+
+	// Override wallet_owner_url, if supplied
+	if let Some(wallet_owner_url) = wallet_owner_url {
+		server_config.wallet_owner_url = wallet_owner_url.parse()?;
+	}
+
+	// Override wallet_owner_secret_path, if supplied
+	if let Some(wallet_owner_secret_path) = wallet_owner_secret_path {
+		server_config.wallet_owner_secret_path = Some(wallet_owner_secret_path.to_owned());
+	}
+
+	// Open wallet
+	let wallet_pass = prompt_wallet_password(&args.value_of("wallet_pass"));
+	let wallet = HttpWallet::open_wallet(
+		&server_config.wallet_owner_url,
+		&server_config.wallet_owner_api_secret(),
+		&wallet_pass,
+	)?;
+
+	// Create GrinNode
+	let node = HttpGrinNode::new(
+		&server_config.grin_node_url,
+		&server_config.node_api_secret(),
+	);
+
+	let stop_state = Arc::new(StopState::new());
+	let stop_state_clone = stop_state.clone();
+
+	let rt = Runtime::new()?;
+	rt.spawn(async move {
+		futures::executor::block_on(build_signals_fut());
+		stop_state_clone.stop();
+	});
+
+	// Start the mwixnet JSON-RPC HTTP server
+	rpc::listen(server_config, Arc::new(wallet), Arc::new(node), stop_state)
+}
+
+async fn build_signals_fut() {
+	if cfg!(unix) {
+		use tokio::signal::unix::{signal, SignalKind};
+
+		// Listen for SIGINT, SIGQUIT, and SIGTERM
+		let mut terminate_signal =
+			signal(SignalKind::terminate()).expect("failed to create terminate signal");
+		let mut quit_signal = signal(SignalKind::quit()).expect("failed to create quit signal");
+		let mut interrupt_signal =
+			signal(SignalKind::interrupt()).expect("failed to create interrupt signal");
+
+		futures::future::select_all(vec![
+			Box::pin(terminate_signal.recv()),
+			Box::pin(quit_signal.recv()),
+			Box::pin(interrupt_signal.recv()),
+		])
+		.await;
+	} else {
 		tokio::signal::ctrl_c()
 			.await
 			.expect("failed to install CTRL+C signal handler");
-    };
-
-    server::listen(&server_config, shutdown_signal)
+	}
+}
+
+fn prompt_password() -> ZeroingString {
+	ZeroingString::from(rpassword::prompt_password_stdout("Server password: ").unwrap())
+}
+
+fn prompt_password_confirm() -> ZeroingString {
+	let mut first = "first".to_string();
+	let mut second = "second".to_string();
+	while first != second {
+		first = rpassword::prompt_password_stdout("Server password: ").unwrap();
+		second = rpassword::prompt_password_stdout("Confirm server password: ").unwrap();
+	}
+	ZeroingString::from(first)
+}
+
+fn prompt_wallet_password(wallet_pass: &Option<&str>) -> ZeroingString {
+	match *wallet_pass {
+		Some(wallet_pass) => ZeroingString::from(wallet_pass),
+		None => {
+			ZeroingString::from(rpassword::prompt_password_stdout("Wallet password: ").unwrap())
+		}
+	}
 }

src/node.rs

@@ -0,0 +1,219 @@
+use crate::error::{ErrorKind, Result};
+use crate::secp::Commitment;
+
+use grin_api::client;
+use grin_api::json_rpc::{build_request, Request, Response};
+use grin_api::{OutputPrintable, OutputType, Tip};
+use grin_core::consensus::COINBASE_MATURITY;
+use grin_core::core::{Input, OutputFeatures, Transaction};
+use grin_util::ToHex;
+
+use serde_json::json;
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+pub trait GrinNode: Send + Sync {
+	/// Retrieves the unspent output with a matching commitment
+	fn get_utxo(&self, output_commit: &Commitment) -> Result<Option<OutputPrintable>>;
+
+	/// Gets the height of the chain tip
+	fn get_chain_height(&self) -> Result<u64>;
+
+	/// Posts a transaction to the grin node
+	fn post_tx(&self, tx: &Transaction) -> Result<()>;
+}
+
+/// Checks if a commitment is in the UTXO set
+pub fn is_unspent(node: &Arc<dyn GrinNode>, commit: &Commitment) -> Result<bool> {
+	let utxo = node.get_utxo(&commit)?;
+	Ok(utxo.is_some())
+}
+
+/// Checks whether a commitment is spendable at the block height provided
+pub fn is_spendable(
+	node: &Arc<dyn GrinNode>,
+	output_commit: &Commitment,
+	next_block_height: u64,
+) -> Result<bool> {
+	let output = node.get_utxo(&output_commit)?;
+	if let Some(out) = output {
+		let is_coinbase = match out.output_type {
+			OutputType::Coinbase => true,
+			OutputType::Transaction => false,
+		};
+
+		if is_coinbase {
+			if let Some(block_height) = out.block_height {
+				if block_height + COINBASE_MATURITY < next_block_height {
+					return Ok(false);
+				}
+			} else {
+				return Ok(false);
+			}
+		}
+
+		return Ok(true);
+	}
+
+	Ok(false)
+}
+
+/// Builds an input for an unspent output commitment
+pub fn build_input(node: &Arc<dyn GrinNode>, output_commit: &Commitment) -> Result<Option<Input>> {
+	let output = node.get_utxo(&output_commit)?;
+
+	if let Some(out) = output {
+		let features = match out.output_type {
+			OutputType::Coinbase => OutputFeatures::Coinbase,
+			OutputType::Transaction => OutputFeatures::Plain,
+		};
+
+		let input = Input::new(features, out.commit);
+		return Ok(Some(input));
+	}
+
+	Ok(None)
+}
+
+/// HTTP (JSON-RPC) implementation of the 'GrinNode' trait
+#[derive(Clone)]
+pub struct HttpGrinNode {
+	node_url: SocketAddr,
+	node_api_secret: Option<String>,
+}
+
+const ENDPOINT: &str = "/v2/foreign";
+
+impl HttpGrinNode {
+	pub fn new(node_url: &SocketAddr, node_api_secret: &Option<String>) -> HttpGrinNode {
+		HttpGrinNode {
+			node_url: node_url.to_owned(),
+			node_api_secret: node_api_secret.to_owned(),
+		}
+	}
+
+	fn send_json_request<D: serde::de::DeserializeOwned>(
+		&self,
+		method: &str,
+		params: &serde_json::Value,
+	) -> Result<D> {
+		let url = format!("http://{}{}", self.node_url, ENDPOINT);
+		let req = build_request(method, params);
+		let res =
+			client::post::<Request, Response>(url.as_str(), self.node_api_secret.clone(), &req)?;
+		let parsed = res.clone().into_result()?;
+		Ok(parsed)
+	}
+}
+
+impl GrinNode for HttpGrinNode {
+	fn get_utxo(&self, output_commit: &Commitment) -> Result<Option<OutputPrintable>> {
+		let commits: Vec<String> = vec![output_commit.to_hex()];
+		let start_height: Option<u64> = None;
+		let end_height: Option<u64> = None;
+		let include_proof: Option<bool> = Some(false);
+		let include_merkle_proof: Option<bool> = Some(false);
+
+		let params = json!([
+			Some(commits),
+			start_height,
+			end_height,
+			include_proof,
+			include_merkle_proof
+		]);
+		let outputs = self.send_json_request::<Vec<OutputPrintable>>("get_outputs", &params)?;
+		if outputs.is_empty() {
+			return Ok(None);
+		}
+
+		Ok(Some(outputs[0].clone()))
+	}
+
+	fn get_chain_height(&self) -> Result<u64> {
+		let params = json!([]);
+		let tip_json = self.send_json_request::<serde_json::Value>("get_tip", &params)?;
+
+		let tip: Result<Tip> = serde_json::from_value(tip_json["Ok"].clone())
+			.map_err(|e| ErrorKind::SerdeJsonError(e.to_string()).into());
+
+		Ok(tip?.height)
+	}
+
+	fn post_tx(&self, tx: &Transaction) -> Result<()> {
+		let params = json!([tx, true]);
+		self.send_json_request::<serde_json::Value>("push_transaction", &params)?;
+		Ok(())
+	}
+}
+
+#[cfg(test)]
+pub mod mock {
+	use super::GrinNode;
+	use crate::error::Result;
+	use crate::secp::Commitment;
+
+	use grin_api::{OutputPrintable, OutputType};
+	use grin_core::core::Transaction;
+	use std::collections::HashMap;
+	use std::sync::RwLock;
+
+	/// Implementation of 'GrinNode' trait that mocks a grin node instance.
+	/// Use only for testing purposes.
+	pub struct MockGrinNode {
+		utxos: HashMap<Commitment, OutputPrintable>,
+		txns_posted: RwLock<Vec<Transaction>>,
+	}
+
+	impl MockGrinNode {
+		pub fn new() -> MockGrinNode {
+			MockGrinNode {
+				utxos: HashMap::new(),
+				txns_posted: RwLock::new(Vec::new()),
+			}
+		}
+
+		pub fn add_utxo(&mut self, output_commit: &Commitment, utxo: &OutputPrintable) {
+			self.utxos.insert(output_commit.clone(), utxo.clone());
+		}
+
+		pub fn add_default_utxo(&mut self, output_commit: &Commitment) {
+			let utxo = OutputPrintable {
+				output_type: OutputType::Transaction,
+				commit: output_commit.to_owned(),
+				spent: false,
+				proof: None,
+				proof_hash: String::from(""),
+				block_height: None,
+				merkle_proof: None,
+				mmr_index: 0,
+			};
+
+			self.add_utxo(&output_commit, &utxo);
+		}
+
+		pub fn get_posted_txns(&self) -> Vec<Transaction> {
+			let read = self.txns_posted.read().unwrap();
+			read.clone()
+		}
+	}
+
+	impl GrinNode for MockGrinNode {
+		fn get_utxo(&self, output_commit: &Commitment) -> Result<Option<OutputPrintable>> {
+			if let Some(utxo) = self.utxos.get(&output_commit) {
+				return Ok(Some(utxo.clone()));
+			}
+
+			Ok(None)
+		}
+
+		fn get_chain_height(&self) -> Result<u64> {
+			Ok(100)
+		}
+
+		fn post_tx(&self, tx: &Transaction) -> Result<()> {
+			let mut write = self.txns_posted.write().unwrap();
+			write.push(tx.clone());
+			Ok(())
+		}
+	}
+}

src/onion.rs

@@ -1,60 +1,52 @@
 use crate::error::Result;
 use crate::secp::{self, Commitment, PublicKey, Secp256k1, SecretKey, SharedSecret};
-use crate::types::{Hop, Onion, RawBytes, Payload, deserialize_payload, serialize_payload};
-use crate::ser;
+use crate::types::Payload;
 
-use chacha20::{ChaCha20, Key, Nonce};
 use chacha20::cipher::{NewCipher, StreamCipher};
-use hmac::{Hmac, Mac, NewMac};
+use chacha20::{ChaCha20, Key, Nonce};
+use grin_core::ser::{self, ProtocolVersion, Writeable, Writer};
+use grin_util::{self, ToHex};
+use hmac::{Hmac, Mac};
+use serde::ser::SerializeStruct;
+use serde::Deserialize;
 use sha2::{Digest, Sha256};
+use std::fmt;
 
 type HmacSha256 = Hmac<Sha256>;
+type RawBytes = Vec<u8>;
 
-/// Create an Onion for the Commitment, encrypting the payload for each hop
-pub fn create_onion(commitment: &Commitment, session_key: &SecretKey, hops: &Vec<Hop>) -> Result<Onion> {
-    let secp = Secp256k1::new();
-    let mut ephemeral_key = session_key.clone();
-
-    let mut shared_secrets: Vec<SharedSecret> = Vec::new();
-    let mut enc_payloads: Vec<RawBytes> = Vec::new();
-    for hop in hops {
-        let shared_secret = SharedSecret::new(&secp, &hop.pubkey, &ephemeral_key);
-
-        let ephemeral_pubkey = PublicKey::from_secret_key(&secp, &ephemeral_key)?;
-        let blinding_factor = calc_blinding_factor(&shared_secret, &ephemeral_pubkey)?;
-
-        shared_secrets.push(shared_secret);
-        enc_payloads.push(serialize_payload(&hop.payload)?);
-        ephemeral_key.mul_assign(&secp, &blinding_factor)?;
-    }
-
-    for i in (0..shared_secrets.len()).rev() {
-        let mut cipher = new_stream_cipher(&shared_secrets[i])?;
-        for j in i..shared_secrets.len() {
-            cipher.apply_keystream(&mut enc_payloads[j]);
-        }
-    }
-
-    let onion = Onion{
-        ephemeral_pubkey: secp::to_public_key(&session_key)?,
-        commit: commitment.clone(),
-        enc_payloads: enc_payloads,
-    };
-    Ok(onion)
+/// A data packet with layers of encryption
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Onion {
+	/// The onion originator's portion of the shared secret
+	pub ephemeral_pubkey: PublicKey,
+	/// The pedersen commitment before adjusting the excess and subtracting the fee
+	pub commit: Commitment,
+	/// The encrypted payloads which represent the layers of the onion
+	pub enc_payloads: Vec<RawBytes>,
 }
 
-/// Peel a single layer off of the Onion, returning the peeled Onion and decrypted Payload
-pub fn peel_layer(onion: &Onion, secret_key: &SecretKey) -> Result<(Payload, Onion)> {
+impl Onion {
+	pub fn serialize(&self) -> Result<Vec<u8>> {
+		let mut vec = vec![];
+		ser::serialize_default(&mut vec, &self)?;
+		Ok(vec)
+	}
+
+	/// Peel a single layer off of the Onion, returning the peeled Onion and decrypted Payload
+	pub fn peel_layer(&self, secret_key: &SecretKey) -> Result<(Payload, Onion)> {
 		let secp = Secp256k1::new();
 
-    let shared_secret = SharedSecret::new(&secp, &onion.ephemeral_pubkey, &secret_key);
+		let shared_secret = SharedSecret::new(&secp, &self.ephemeral_pubkey, &secret_key);
 		let mut cipher = new_stream_cipher(&shared_secret)?;
 
-    let mut decrypted_bytes = onion.enc_payloads[0].clone();
+		let mut decrypted_bytes = self.enc_payloads[0].clone();
 		cipher.apply_keystream(&mut decrypted_bytes);
-    let decrypted_payload = deserialize_payload(&decrypted_bytes)?;
+		let decrypted_payload = Payload::deserialize(&decrypted_bytes)?;
 
-    let enc_payloads : Vec<RawBytes> = onion.enc_payloads.iter()
+		let enc_payloads: Vec<RawBytes> = self
+			.enc_payloads
+			.iter()
 			.enumerate()
 			.filter(|&(i, _)| i != 0)
 			.map(|(_, enc_payload)| {
@@ -64,24 +56,29 @@ pub fn peel_layer(onion: &Onion, secret_key: &SecretKey) -> Result<(Payload, Oni
 			})
 			.collect();
 
-    let blinding_factor = calc_blinding_factor(&shared_secret, &onion.ephemeral_pubkey)?;
+		let blinding_factor = calc_blinding_factor(&shared_secret, &self.ephemeral_pubkey)?;
 
-    let mut ephemeral_pubkey = onion.ephemeral_pubkey.clone();
+		let mut ephemeral_pubkey = self.ephemeral_pubkey.clone();
 		ephemeral_pubkey.mul_assign(&secp, &blinding_factor)?;
 
-    let mut commitment = onion.commit.clone();
+		let mut commitment = self.commit.clone();
 		commitment = secp::add_excess(&commitment, &decrypted_payload.excess)?;
+		commitment = secp::sub_value(&commitment, decrypted_payload.fee.into())?;
 
-    let peeled_onion = Onion{
-        ephemeral_pubkey: ephemeral_pubkey,
+		let peeled_onion = Onion {
+			ephemeral_pubkey,
 			commit: commitment.clone(),
-        enc_payloads: enc_payloads,
+			enc_payloads,
 		};
 		Ok((decrypted_payload, peeled_onion))
+	}
 }
 
-fn calc_blinding_factor(shared_secret: &SharedSecret, ephemeral_pubkey: &PublicKey) -> Result<SecretKey> {
-    let serialized_pubkey = ser::ser_vec(&ephemeral_pubkey)?;
+fn calc_blinding_factor(
+	shared_secret: &SharedSecret,
+	ephemeral_pubkey: &PublicKey,
+) -> Result<SecretKey> {
+	let serialized_pubkey = ser::ser_vec(&ephemeral_pubkey, ProtocolVersion::local())?;
 
 	let mut hasher = Sha256::default();
 	hasher.update(&serialized_pubkey);
@@ -103,65 +100,249 @@ fn new_stream_cipher(shared_secret: &SharedSecret) -> Result<ChaCha20> {
 	Ok(ChaCha20::new(&key, &nonce))
 }
 
+impl Writeable for Onion {
+	fn write<W: Writer>(&self, writer: &mut W) -> std::result::Result<(), ser::Error> {
+		self.ephemeral_pubkey.write(writer)?;
+		writer.write_fixed_bytes(&self.commit)?;
+		writer.write_u64(self.enc_payloads.len() as u64)?;
+		for p in &self.enc_payloads {
+			writer.write_u64(p.len() as u64)?;
+			p.write(writer)?;
+		}
+		Ok(())
+	}
+}
+
+impl serde::ser::Serialize for Onion {
+	fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
+	where
+		S: serde::ser::Serializer,
+	{
+		let mut state = serializer.serialize_struct("Onion", 3)?;
+
+		let secp = Secp256k1::new();
+		state.serialize_field(
+			"pubkey",
+			&self.ephemeral_pubkey.serialize_vec(&secp, true).to_hex(),
+		)?;
+		state.serialize_field("commit", &self.commit.to_hex())?;
+
+		let hex_payloads: Vec<String> = self.enc_payloads.iter().map(|v| v.to_hex()).collect();
+		state.serialize_field("data", &hex_payloads)?;
+		state.end()
+	}
+}
+
+impl<'de> serde::de::Deserialize<'de> for Onion {
+	fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
+	where
+		D: serde::de::Deserializer<'de>,
+	{
+		#[derive(Deserialize)]
+		#[serde(field_identifier, rename_all = "snake_case")]
+		enum Field {
+			Pubkey,
+			Commit,
+			Data,
+		}
+
+		struct OnionVisitor;
+
+		impl<'de> serde::de::Visitor<'de> for OnionVisitor {
+			type Value = Onion;
+
+			fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+				formatter.write_str("an Onion")
+			}
+
+			fn visit_map<A>(self, mut map: A) -> std::result::Result<Self::Value, A::Error>
+			where
+				A: serde::de::MapAccess<'de>,
+			{
+				let mut pubkey = None;
+				let mut commit = None;
+				let mut data = None;
+
+				while let Some(key) = map.next_key()? {
+					match key {
+						Field::Pubkey => {
+							let val: String = map.next_value()?;
+							let vec =
+								grin_util::from_hex(&val).map_err(serde::de::Error::custom)?;
+							let secp = Secp256k1::new();
+							pubkey = Some(
+								PublicKey::from_slice(&secp, &vec[..])
+									.map_err(serde::de::Error::custom)?,
+							);
+						}
+						Field::Commit => {
+							let val: String = map.next_value()?;
+							let vec =
+								grin_util::from_hex(&val).map_err(serde::de::Error::custom)?;
+							commit = Some(Commitment::from_vec(vec));
+						}
+						Field::Data => {
+							let val: Vec<String> = map.next_value()?;
+							let mut vec: Vec<Vec<u8>> = Vec::new();
+							for hex in val {
+								vec.push(
+									grin_util::from_hex(&hex).map_err(serde::de::Error::custom)?,
+								);
+							}
+							data = Some(vec);
+						}
+					}
+				}
+
+				Ok(Onion {
+					ephemeral_pubkey: pubkey.unwrap(),
+					commit: commit.unwrap(),
+					enc_payloads: data.unwrap(),
+				})
+			}
+		}
+
+		const FIELDS: &[&str] = &["pubkey", "commit", "data"];
+		deserializer.deserialize_struct("Onion", &FIELDS, OnionVisitor)
+	}
+}
+
 #[cfg(test)]
-mod tests {
-    use super::super::secp;
-    use super::super::types;
-    use super::super::onion;
+pub mod test_util {
+	use super::{Onion, RawBytes};
+	use crate::error::Result;
+	use crate::secp::{Commitment, PublicKey, Secp256k1, SecretKey, SharedSecret};
+	use crate::types::Payload;
+
+	use crate::secp;
+	use chacha20::cipher::StreamCipher;
+
+	#[derive(Clone)]
+	pub struct Hop {
+		pub pubkey: PublicKey,
+		pub payload: Payload,
+	}
+
+	/// Create an Onion for the Commitment, encrypting the payload for each hop
+	pub fn create_onion(commitment: &Commitment, hops: &Vec<Hop>) -> Result<Onion> {
+		let secp = Secp256k1::new();
+		let session_key = secp::random_secret();
+		let mut ephemeral_key = session_key.clone();
+
+		let mut shared_secrets: Vec<SharedSecret> = Vec::new();
+		let mut enc_payloads: Vec<RawBytes> = Vec::new();
+		for hop in hops {
+			let shared_secret = SharedSecret::new(&secp, &hop.pubkey, &ephemeral_key);
+
+			let ephemeral_pubkey = PublicKey::from_secret_key(&secp, &ephemeral_key)?;
+			let blinding_factor = super::calc_blinding_factor(&shared_secret, &ephemeral_pubkey)?;
+
+			shared_secrets.push(shared_secret);
+			enc_payloads.push(hop.payload.serialize()?);
+			ephemeral_key.mul_assign(&secp, &blinding_factor)?;
+		}
+
+		for i in (0..shared_secrets.len()).rev() {
+			let mut cipher = super::new_stream_cipher(&shared_secrets[i])?;
+			for j in i..shared_secrets.len() {
+				cipher.apply_keystream(&mut enc_payloads[j]);
+			}
+		}
+
+		let onion = Onion {
+			ephemeral_pubkey: PublicKey::from_secret_key(&secp, &session_key)?,
+			commit: commitment.clone(),
+			enc_payloads,
+		};
+		Ok(onion)
+	}
+
+	/// Calculates the expected next ephemeral pubkey after peeling a layer off of the Onion.
+	pub fn next_ephemeral_pubkey(onion: &Onion, server_key: &SecretKey) -> Result<PublicKey> {
+		let secp = Secp256k1::new();
+		let mut ephemeral_pubkey = onion.ephemeral_pubkey.clone();
+		let shared_secret = SharedSecret::new(&secp, &ephemeral_pubkey, &server_key);
+		let blinding_factor = super::calc_blinding_factor(&shared_secret, &ephemeral_pubkey)?;
+		ephemeral_pubkey.mul_assign(&secp, &blinding_factor)?;
+		Ok(ephemeral_pubkey)
+	}
+}
+
+#[cfg(test)]
+pub mod tests {
+	use super::test_util::{self, Hop};
+	use crate::secp;
+	use crate::types::Payload;
+
+	use grin_core::core::FeeFields;
 
 	/// Test end-to-end Onion creation and unwrapping logic.
 	#[test]
 	fn onion() {
-        let value : u64 = 1000;
-        let blind = secp::insecure_rand_secret().unwrap(); 
-        let commitment = secp::commit(value, &blind).unwrap();
+		let total_fee: u64 = 10;
+		let fee_per_hop: u64 = 2;
+		let in_value: u64 = 1000;
+		let out_value: u64 = in_value - total_fee;
+		let blind = secp::random_secret();
+		let commitment = secp::commit(in_value, &blind).unwrap();
 
-        let session_key = secp::insecure_rand_secret().unwrap();
-        let mut hops : Vec<types::Hop> = Vec::new();
-    
-        let mut keys : Vec<secp::SecretKey> = Vec::new();
-        let mut final_commit = commitment.clone();
+		let mut hops: Vec<Hop> = Vec::new();
+		let mut keys: Vec<secp::SecretKey> = Vec::new();
+		let mut final_commit = secp::commit(out_value, &blind).unwrap();
 		let mut final_blind = blind.clone();
 		for i in 0..5 {
-            keys.push(secp::insecure_rand_secret().unwrap());
+			keys.push(secp::random_secret());
 
-            let excess = secp::insecure_rand_secret().unwrap();
+			let excess = secp::random_secret();
 
 			let secp = secp256k1zkp::Secp256k1::with_caps(secp256k1zkp::ContextFlag::Commit);
 			final_blind.add_assign(&secp, &excess).unwrap();
 			final_commit = secp::add_excess(&final_commit, &excess).unwrap();
 			let proof = if i == 4 {
-                let n1 = secp::insecure_rand_secret().unwrap();
-                let rp = secp.bullet_proof(value, final_blind.clone(), n1.clone(), n1.clone(), None, None);
+				let n1 = secp::random_secret();
+				let rp = secp.bullet_proof(
+					out_value,
+					final_blind.clone(),
+					n1.clone(),
+					n1.clone(),
+					None,
+					None,
+				);
 				assert!(secp.verify_bullet_proof(final_commit, rp, None).is_ok());
 				Some(rp)
 			} else {
 				None
 			};
 
-            hops.push(types::Hop{
+			hops.push(Hop {
 				pubkey: secp::PublicKey::from_secret_key(&secp, &keys[i]).unwrap(),
-                payload: types::Payload{
-                    excess: excess,
+				payload: Payload {
+					excess,
+					fee: FeeFields::from(fee_per_hop as u32),
 					rangeproof: proof,
-                }
+				},
 			});
 		}
 
-        let mut onion_packet = onion::create_onion(&commitment, &session_key, &hops).unwrap();
+		let mut onion_packet = test_util::create_onion(&commitment, &hops).unwrap();
 
-        let mut payload = types::Payload{
-            excess: secp::insecure_rand_secret().unwrap(),
-            rangeproof: None
+		let mut payload = Payload {
+			excess: secp::random_secret(),
+			fee: FeeFields::from(fee_per_hop as u32),
+			rangeproof: None,
 		};
 		for i in 0..5 {
-            let peeled = onion::peel_layer(&onion_packet, &keys[i]).unwrap();
+			let peeled = onion_packet.peel_layer(&keys[i]).unwrap();
 			payload = peeled.0;
 			onion_packet = peeled.1;
 		}
 
 		assert!(payload.rangeproof.is_some());
-        assert_eq!(payload.rangeproof.unwrap(), hops[4].payload.rangeproof.unwrap());
-        assert_eq!(secp::commit(value, &final_blind).unwrap(), final_commit);
+		assert_eq!(
+			payload.rangeproof.unwrap(),
+			hops[4].payload.rangeproof.unwrap()
+		);
+		assert_eq!(secp::commit(out_value, &final_blind).unwrap(), final_commit);
+		assert_eq!(payload.fee, FeeFields::from(fee_per_hop as u32));
 	}
 }

src/rpc.rs

@@ -0,0 +1,271 @@
+use crate::config::ServerConfig;
+use crate::node::GrinNode;
+use crate::onion::Onion;
+use crate::secp::{self, ComSignature};
+use crate::server::{Server, ServerImpl, SwapError};
+use crate::wallet::Wallet;
+
+use grin_util::StopState;
+use jsonrpc_core::{Result, Value};
+use jsonrpc_derive::rpc;
+use jsonrpc_http_server::jsonrpc_core::*;
+use jsonrpc_http_server::*;
+use serde::{Deserialize, Serialize};
+use std::sync::{Arc, Mutex};
+use std::thread::{sleep, spawn};
+use std::time::Duration;
+
+#[derive(Serialize, Deserialize)]
+pub struct SwapReq {
+	onion: Onion,
+	#[serde(with = "secp::comsig_serde")]
+	comsig: ComSignature,
+}
+
+#[rpc(server)]
+pub trait API {
+	#[rpc(name = "swap")]
+	fn swap(&self, swap: SwapReq) -> Result<Value>;
+
+	// milestone 3: Used by mwixnet coinswap servers to communicate with each other
+	// fn derive_outputs(&self, entries: Vec<Onion>) -> Result<Value>;
+	// fn derive_kernel(&self, tx: Tx) -> Result<Value>;
+}
+
+#[derive(Clone)]
+struct RPCServer {
+	server_config: ServerConfig,
+	server: Arc<Mutex<dyn Server>>,
+}
+
+impl RPCServer {
+	/// Spin up an instance of the JSON-RPC HTTP server.
+	fn start_http(&self) -> jsonrpc_http_server::Server {
+		let mut io = IoHandler::new();
+		io.extend_with(RPCServer::to_delegate(self.clone()));
+
+		ServerBuilder::new(io)
+			.cors(DomainsValidation::Disabled)
+			.request_middleware(|request: hyper::Request<hyper::Body>| {
+				if request.uri() == "/v1" {
+					request.into()
+				} else {
+					jsonrpc_http_server::Response::bad_request("Only v1 supported").into()
+				}
+			})
+			.start_http(&self.server_config.addr)
+			.expect("Unable to start RPC server")
+	}
+}
+
+impl From<SwapError> for Error {
+	fn from(e: SwapError) -> Self {
+		match e {
+			SwapError::UnknownError(_) => Error {
+				message: e.to_string(),
+				code: ErrorCode::InternalError,
+				data: None,
+			},
+			_ => Error::invalid_params(e.to_string()),
+		}
+	}
+}
+
+impl API for RPCServer {
+	/// Implements the 'swap' API
+	fn swap(&self, swap: SwapReq) -> Result<Value> {
+		self.server
+			.lock()
+			.unwrap()
+			.swap(&swap.onion, &swap.comsig)?;
+		Ok(Value::String("success".into()))
+	}
+}
+
+/// Spin up the JSON-RPC web server
+pub fn listen(
+	server_config: ServerConfig,
+	wallet: Arc<dyn Wallet>,
+	node: Arc<dyn GrinNode>,
+	stop_state: Arc<StopState>,
+) -> std::result::Result<(), Box<dyn std::error::Error>> {
+	let server = ServerImpl::new(server_config.clone(), wallet.clone(), node.clone());
+	let server = Arc::new(Mutex::new(server));
+
+	let rpc_server = RPCServer {
+		server_config: server_config.clone(),
+		server: server.clone(),
+	};
+
+	let http_server = rpc_server.start_http();
+	println!("Server listening on {}", server_config.addr);
+
+	let close_handle = http_server.close_handle();
+	let round_handle = spawn(move || {
+		let mut secs = 0;
+		loop {
+			if stop_state.is_stopped() {
+				close_handle.close();
+				break;
+			}
+
+			sleep(Duration::from_secs(1));
+			secs = (secs + 1) % server_config.interval_s;
+
+			if secs == 0 {
+				let _ = server.lock().unwrap().execute_round();
+			}
+		}
+	});
+
+	http_server.wait();
+	round_handle.join().unwrap();
+
+	Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+	use crate::config::ServerConfig;
+	use crate::onion::test_util;
+	use crate::rpc::{RPCServer, SwapReq};
+	use crate::secp::{self, ComSignature};
+	use crate::server::mock::MockServer;
+	use crate::server::{Server, SwapError};
+
+	use std::net::TcpListener;
+	use std::sync::{Arc, Mutex};
+
+	use hyper::{Body, Client, Request, Response};
+	use tokio::runtime::Runtime;
+
+	async fn body_to_string(req: Response<Body>) -> String {
+		let body_bytes = hyper::body::to_bytes(req.into_body()).await.unwrap();
+		String::from_utf8(body_bytes.to_vec()).unwrap()
+	}
+
+	/// Spin up a temporary web service, query the API, then cleanup and return response
+	fn make_request(
+		server: Arc<Mutex<dyn Server>>,
+		req: String,
+	) -> Result<String, Box<dyn std::error::Error>> {
+		let server_config = ServerConfig {
+			key: secp::random_secret(),
+			interval_s: 1,
+			addr: TcpListener::bind("127.0.0.1:0")?.local_addr()?,
+			grin_node_url: "127.0.0.1:3413".parse()?,
+			grin_node_secret_path: None,
+			wallet_owner_url: "127.0.0.1:3420".parse()?,
+			wallet_owner_secret_path: None,
+		};
+
+		let rpc_server = RPCServer {
+			server_config: server_config.clone(),
+			server: server.clone(),
+		};
+
+		// Start the JSON-RPC server
+		let http_server = rpc_server.start_http();
+
+		let uri = format!("http://{}/v1", server_config.addr);
+
+		let threaded_rt = Runtime::new()?;
+		let do_request = async move {
+			let request = Request::post(uri)
+				.header("Content-Type", "application/json")
+				.body(Body::from(req))
+				.unwrap();
+
+			Client::new().request(request).await
+		};
+
+		let response = threaded_rt.block_on(do_request)?;
+		let response_str: String = threaded_rt.block_on(body_to_string(response));
+
+		// Wait for shutdown
+		threaded_rt.shutdown_background();
+
+		// Execute one round
+		server.lock().unwrap().execute_round()?;
+
+		// Stop the server
+		http_server.close();
+
+		Ok(response_str)
+	}
+
+	// todo: Test all error types
+
+	/// Demonstrates a successful swap response
+	#[test]
+	fn swap_success() -> Result<(), Box<dyn std::error::Error>> {
+		let commitment = secp::commit(1234, &secp::random_secret())?;
+		let onion = test_util::create_onion(&commitment, &vec![])?;
+		let comsig = ComSignature::sign(1234, &secp::random_secret(), &onion.serialize()?)?;
+		let swap = SwapReq {
+			onion: onion.clone(),
+			comsig,
+		};
+
+		let server: Arc<Mutex<dyn Server>> = Arc::new(Mutex::new(MockServer::new()));
+
+		let req = format!(
+			"{{\"jsonrpc\": \"2.0\", \"method\": \"swap\", \"params\": [{}], \"id\": \"1\"}}",
+			serde_json::json!(swap)
+		);
+		println!("Request: {}", req);
+		let response = make_request(server, req)?;
+		let expected = "{\"jsonrpc\":\"2.0\",\"result\":\"success\",\"id\":\"1\"}\n";
+		assert_eq!(response, expected);
+
+		Ok(())
+	}
+
+	#[test]
+	fn swap_bad_request() -> Result<(), Box<dyn std::error::Error>> {
+		let server: Arc<Mutex<dyn Server>> = Arc::new(Mutex::new(MockServer::new()));
+
+		let params = "{ \"param\": \"Not a valid Swap request\" }";
+		let req = format!(
+			"{{\"jsonrpc\": \"2.0\", \"method\": \"swap\", \"params\": [{}], \"id\": \"1\"}}",
+			params
+		);
+		let response = make_request(server, req)?;
+		let expected = "{\"jsonrpc\":\"2.0\",\"error\":{\"code\":-32602,\"message\":\"Invalid params: missing field `onion`.\"},\"id\":\"1\"}\n";
+		assert_eq!(response, expected);
+		Ok(())
+	}
+
+	/// Returns "Commitment not found" when there's no matching output in the UTXO set.
+	#[test]
+	fn swap_utxo_missing() -> Result<(), Box<dyn std::error::Error>> {
+		let commitment = secp::commit(1234, &secp::random_secret())?;
+		let onion = test_util::create_onion(&commitment, &vec![])?;
+		let comsig = ComSignature::sign(1234, &secp::random_secret(), &onion.serialize()?)?;
+		let swap = SwapReq {
+			onion: onion.clone(),
+			comsig,
+		};
+
+		let mut server = MockServer::new();
+		server.set_response(
+			&onion,
+			SwapError::CoinNotFound {
+				commit: commitment.clone(),
+			},
+		);
+		let server: Arc<Mutex<dyn Server>> = Arc::new(Mutex::new(server));
+
+		let req = format!(
+			"{{\"jsonrpc\": \"2.0\", \"method\": \"swap\", \"params\": [{}], \"id\": \"1\"}}",
+			serde_json::json!(swap)
+		);
+		let response = make_request(server, req)?;
+		let expected = format!(
+			"{{\"jsonrpc\":\"2.0\",\"error\":{{\"code\":-32602,\"message\":\"Output {:?} does not exist, or is already spent.\"}},\"id\":\"1\"}}\n",
+			commitment
+		);
+		assert_eq!(response, expected);
+		Ok(())
+	}
+}

src/secp.rs

@@ -1,92 +1,165 @@
-pub use secp256k1zkp::{ContextFlag, Message, Secp256k1, Signature};
+pub use secp256k1zkp::aggsig;
+pub use secp256k1zkp::constants::{
+	AGG_SIGNATURE_SIZE, COMPRESSED_PUBLIC_KEY_SIZE, MAX_PROOF_SIZE, PEDERSEN_COMMITMENT_SIZE,
+	SECRET_KEY_SIZE,
+};
 pub use secp256k1zkp::ecdh::SharedSecret;
+pub use secp256k1zkp::key::{PublicKey, SecretKey, ZERO_KEY};
 pub use secp256k1zkp::pedersen::{Commitment, RangeProof};
-pub use secp256k1zkp::key::{PublicKey, SecretKey};
-pub use secp256k1zkp::constants::{AGG_SIGNATURE_SIZE, COMPRESSED_PUBLIC_KEY_SIZE, MAX_PROOF_SIZE, PEDERSEN_COMMITMENT_SIZE, SECRET_KEY_SIZE};
+pub use secp256k1zkp::{ContextFlag, Message, Secp256k1, Signature};
 
-use crate::ser::{Readable, Reader, Writeable, Writer};
-use crate::error::{ErrorKind, Result};
+use crate::error::{Error, ErrorKind, Result};
 
-use rand::RngCore;
-use std::cmp;
+use blake2::blake2b::Blake2b;
+use byteorder::{BigEndian, ByteOrder};
+use grin_core::ser::{self, Readable, Reader, Writeable, Writer};
+use secp256k1zkp::rand::thread_rng;
 
 /// A generalized Schnorr signature with a pedersen commitment value & blinding factors as the keys
-pub const COM_SIGNATURE_SIZE : usize = 96;
+#[derive(Clone)]
+pub struct ComSignature {
+	pub_nonce: Commitment,
+	s: SecretKey,
+	t: SecretKey,
+}
 
-pub struct ComSignature(pub [u8; COM_SIGNATURE_SIZE]);
 impl ComSignature {
-    /// Builds a ComSignature from a byte vector. If the vector is too short, it will be
-    /// completed by zeroes. If it's too long, it will be truncated.
-    pub fn from_vec(v: Vec<u8>) -> ComSignature {
-        let mut h = [0; COM_SIGNATURE_SIZE];
-        for i in 0..cmp::min(v.len(), COM_SIGNATURE_SIZE) {
-            h[i] = v[i];
+	pub fn new(pub_nonce: &Commitment, s: &SecretKey, t: &SecretKey) -> ComSignature {
+		ComSignature {
+			pub_nonce: pub_nonce.to_owned(),
+			s: s.to_owned(),
+			t: t.to_owned(),
 		}
-        ComSignature(h)
 	}
 
 	#[allow(dead_code)]
-    pub fn sign(_value: u64, _blind: &SecretKey, _msg: &Vec<u8>) -> Result<ComSignature> {
-        // milestone 2 - todo
-        let mut h = [0u8; COM_SIGNATURE_SIZE];
-        for i in 0..COM_SIGNATURE_SIZE {
-            h[i] = i as u8;
-        }
-        Ok(ComSignature(h))
+	pub fn sign(amount: u64, blind: &SecretKey, msg: &Vec<u8>) -> Result<ComSignature> {
+		let secp = Secp256k1::with_caps(ContextFlag::Commit);
+
+		let mut amt_bytes = [0; 32];
+		BigEndian::write_u64(&mut amt_bytes[24..32], amount);
+		let k_amt = SecretKey::from_slice(&secp, &amt_bytes)?;
+
+		let k_1 = SecretKey::new(&secp, &mut thread_rng());
+		let k_2 = SecretKey::new(&secp, &mut thread_rng());
+
+		let commitment = secp.commit(amount, blind.clone())?;
+		let nonce_commitment = secp.commit_blind(k_1.clone(), k_2.clone())?;
+
+		let e = ComSignature::calc_challenge(&secp, &commitment, &nonce_commitment, &msg)?;
+
+		// s = k_1 + (e * amount)
+		let mut s = k_amt.clone();
+		s.mul_assign(&secp, &e)?;
+		s.add_assign(&secp, &k_1)?;
+
+		// t = k_2 + (e * blind)
+		let mut t = blind.clone();
+		t.mul_assign(&secp, &e)?;
+		t.add_assign(&secp, &k_2)?;
+
+		Ok(ComSignature::new(&nonce_commitment, &s, &t))
+	}
+
+	#[allow(non_snake_case)]
+	pub fn verify(&self, commit: &Commitment, msg: &Vec<u8>) -> Result<()> {
+		let secp = Secp256k1::with_caps(ContextFlag::Commit);
+
+		let S1 = secp.commit_blind(self.s.clone(), self.t.clone())?;
+
+		let mut Ce = commit.to_pubkey(&secp)?;
+		let e = ComSignature::calc_challenge(&secp, &commit, &self.pub_nonce, &msg)?;
+		Ce.mul_assign(&secp, &e)?;
+
+		let commits = vec![Commitment::from_pubkey(&secp, &Ce)?, self.pub_nonce.clone()];
+		let S2 = secp.commit_sum(commits, Vec::new())?;
+
+		if S1 != S2 {
+			return Err(Error::new(ErrorKind::InvalidSigError));
 		}
 
-    pub fn verify(self, _commit: &Commitment, _msg: &Vec<u8>) -> Result<()> {
-        // milestone 2 - todo
 		Ok(())
 	}
-}
 
-impl AsRef<[u8]> for ComSignature {
-    fn as_ref(&self) -> &[u8] {
-        &self.0
+	fn calc_challenge(
+		secp: &Secp256k1,
+		commit: &Commitment,
+		nonce_commit: &Commitment,
+		msg: &Vec<u8>,
+	) -> Result<SecretKey> {
+		let mut challenge_hasher = Blake2b::new(32);
+		challenge_hasher.update(&commit.0);
+		challenge_hasher.update(&nonce_commit.0);
+		challenge_hasher.update(msg);
+
+		let mut challenge = [0; 32];
+		challenge.copy_from_slice(challenge_hasher.finalize().as_bytes());
+
+		Ok(SecretKey::from_slice(&secp, &challenge)?)
 	}
 }
 
 /// Serializes a ComSignature to and from hex
 pub mod comsig_serde {
 	use super::ComSignature;
-    use serde::{Deserialize, Serializer};
+	use grin_core::ser::{self, ProtocolVersion};
 	use grin_util::ToHex;
+	use serde::{Deserialize, Serializer};
 
 	/// Serializes a ComSignature as a hex string
 	pub fn serialize<S>(comsig: &ComSignature, serializer: S) -> Result<S::Ok, S::Error>
 	where
 		S: Serializer,
 	{
-        serializer.serialize_str(&comsig.to_hex())
+		use serde::ser::Error;
+		let bytes = ser::ser_vec(&comsig, ProtocolVersion::local()).map_err(Error::custom)?;
+		serializer.serialize_str(&bytes.to_hex())
 	}
 
 	/// Creates a ComSignature from a hex string
-    pub fn deserialize<'de, D>(deserializer: D) -> std::result::Result<ComSignature, D::Error>
+	pub fn deserialize<'de, D>(deserializer: D) -> Result<ComSignature, D::Error>
 	where
 		D: serde::Deserializer<'de>,
 	{
 		use serde::de::Error;
-        String::deserialize(deserializer)
-            .and_then(|string| grin_util::from_hex(&string).map_err(Error::custom))
-            .and_then(|bytes: Vec<u8>| Ok(ComSignature::from_vec(bytes.to_vec())))
+		let bytes = String::deserialize(deserializer)
+			.and_then(|string| grin_util::from_hex(&string).map_err(Error::custom))?;
+		let sig: ComSignature = ser::deserialize_default(&mut &bytes[..]).map_err(Error::custom)?;
+		Ok(sig)
 	}
 }
 
-/// Compute a PublicKey from a SecretKey
-pub fn to_public_key(secret_key: &SecretKey) -> Result<PublicKey> {
-    let secp = Secp256k1::new();
-    let pubkey = PublicKey::from_secret_key(&secp, secret_key)?;
-    Ok(pubkey)
+#[allow(non_snake_case)]
+impl Readable for ComSignature {
+	fn read<R: Reader>(reader: &mut R) -> std::result::Result<Self, ser::Error> {
+		let R = Commitment::read(reader)?;
+		let s = read_secret_key(reader)?;
+		let t = read_secret_key(reader)?;
+		Ok(ComSignature::new(&R, &s, &t))
+	}
 }
 
-/// Generate a random SecretKey. Not for production use
-pub fn insecure_rand_secret() -> Result<SecretKey> {
+impl Writeable for ComSignature {
+	fn write<W: Writer>(&self, writer: &mut W) -> std::result::Result<(), ser::Error> {
+		writer.write_fixed_bytes(self.pub_nonce.0)?;
+		writer.write_fixed_bytes(self.s.0)?;
+		writer.write_fixed_bytes(self.t.0)?;
+		Ok(())
+	}
+}
+
+/// Generate a random SecretKey.
+pub fn random_secret() -> SecretKey {
 	let secp = Secp256k1::new();
-    let mut seed = [0u8; 32];
-    rand::thread_rng().fill_bytes(&mut seed);
-    let secret = SecretKey::from_slice(&secp, &seed)?;
-    Ok(secret)
+	SecretKey::new(&secp, &mut thread_rng())
+}
+
+/// Deserialize a SecretKey from a Reader
+pub fn read_secret_key<R: Reader>(reader: &mut R) -> std::result::Result<SecretKey, ser::Error> {
+	let buf = reader.read_fixed_bytes(SECRET_KEY_SIZE)?;
+	let secp = Secp256k1::with_caps(ContextFlag::None);
+	let pk = SecretKey::from_slice(&secp, &buf).map_err(|_| ser::Error::CorruptedData)?;
+	Ok(pk)
 }
 
 /// Build a Pedersen Commitment using the provided value and blinding factor
@@ -99,96 +172,56 @@ pub fn commit(value: u64, blind: &SecretKey) -> Result<Commitment> {
 /// Add a blinding factor to an existing Commitment
 pub fn add_excess(commitment: &Commitment, excess: &SecretKey) -> Result<Commitment> {
 	let secp = Secp256k1::with_caps(ContextFlag::Commit);
-    let excess_commit : Commitment = secp.commit(0, excess.clone())?;
+	let excess_commit: Commitment = secp.commit(0, excess.clone())?;
 
 	let commits = vec![commitment.clone(), excess_commit.clone()];
 	let sum = secp.commit_sum(commits, Vec::new())?;
 	Ok(sum)
 }
 
-/// secp256k1-zkp object serialization
-
-impl Readable for Commitment {
-    fn read<R: Reader>(reader: &mut R) -> Result<Commitment> {
-        let a = reader.read_fixed_bytes(PEDERSEN_COMMITMENT_SIZE)?;
-        let mut c = [0; PEDERSEN_COMMITMENT_SIZE];
-        c[..PEDERSEN_COMMITMENT_SIZE].clone_from_slice(&a[..PEDERSEN_COMMITMENT_SIZE]);
-        Ok(Commitment(c))
-    }
+/// Subtracts a value (v*H) from an existing commitment
+pub fn sub_value(commitment: &Commitment, value: u64) -> Result<Commitment> {
+	let secp = Secp256k1::with_caps(ContextFlag::Commit);
+	let neg_commit: Commitment = secp.commit(value, ZERO_KEY)?;
+	let sum = secp.commit_sum(vec![commitment.clone()], vec![neg_commit.clone()])?;
+	Ok(sum)
 }
 
-impl Writeable for Commitment {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        writer.write_fixed_bytes(self)
-    }
+/// Signs the message with the provided SecretKey
+pub fn sign(sk: &SecretKey, msg: &Message) -> Result<Signature> {
+	let secp = Secp256k1::with_caps(ContextFlag::Full);
+	let pubkey = PublicKey::from_secret_key(&secp, &sk)?;
+	let sig = aggsig::sign_single(&secp, &msg, &sk, None, None, None, Some(&pubkey), None)?;
+	Ok(sig)
 }
 
-impl Readable for RangeProof {
-    fn read<R: Reader>(reader: &mut R) -> Result<RangeProof> {
-        let len = reader.read_u64()?;
-        let max_len = cmp::min(len as usize, MAX_PROOF_SIZE);
-        let p = reader.read_fixed_bytes(max_len)?;
-        let mut proof = [0; MAX_PROOF_SIZE];
-        proof[..p.len()].clone_from_slice(&p[..]);
-        Ok(RangeProof {
-            plen: proof.len(),
-            proof,
-        })
-    }
-}
+#[cfg(test)]
+mod tests {
+	use super::{ComSignature, ContextFlag, Secp256k1, SecretKey};
+	use crate::error::Result;
 
-impl Writeable for RangeProof {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        writer.write_bytes(self)
-    }
-}
+	use rand::Rng;
+	use secp256k1zkp::rand::{thread_rng, RngCore};
 
-impl Readable for Signature {
-    fn read<R: Reader>(reader: &mut R) -> Result<Signature> {
-        let a = reader.read_fixed_bytes(AGG_SIGNATURE_SIZE)?;
-        let mut c = [0; AGG_SIGNATURE_SIZE];
-        c[..AGG_SIGNATURE_SIZE].clone_from_slice(&a[..AGG_SIGNATURE_SIZE]);
-        Ok(Signature::from_raw_data(&c).unwrap())
-    }
-}
+	/// Test signing and verification of ComSignatures
+	#[test]
+	fn verify_comsig() -> Result<()> {
+		let secp = Secp256k1::with_caps(ContextFlag::Commit);
 
-impl Writeable for Signature {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        writer.write_fixed_bytes(self)
-    }
-}
+		let amount = thread_rng().next_u64();
+		let blind = SecretKey::new(&secp, &mut thread_rng());
+		let msg: [u8; 16] = rand::thread_rng().gen();
+		let comsig = ComSignature::sign(amount, &blind, &msg.to_vec())?;
 
-impl Readable for PublicKey {
-    // Read the public key in compressed form
-    fn read<R: Reader>(reader: &mut R) -> Result<Self> {
-        let buf = reader.read_fixed_bytes(COMPRESSED_PUBLIC_KEY_SIZE)?;
-        let secp = Secp256k1::with_caps(ContextFlag::None);
-        let pk = PublicKey::from_slice(&secp, &buf).map_err(|_| ErrorKind::CorruptedData)?;
-        Ok(pk)
-    }
-}
+		let commit = secp.commit(amount, blind.clone())?;
+		assert!(comsig.verify(&commit, &msg.to_vec()).is_ok());
+
+		let wrong_msg: [u8; 16] = rand::thread_rng().gen();
+		assert!(comsig.verify(&commit, &wrong_msg.to_vec()).is_err());
+
+		let wrong_commit = secp.commit(amount, SecretKey::new(&secp, &mut thread_rng()))?;
+		assert!(comsig.verify(&wrong_commit, &msg.to_vec()).is_err());
 
-impl Writeable for PublicKey {
-    // Write the public key in compressed form
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        let secp = Secp256k1::with_caps(ContextFlag::None);
-        writer.write_fixed_bytes(self.serialize_vec(&secp, true))?;
-        Ok(())
-    }
-}
-
-impl Readable for SecretKey {
-    fn read<R: Reader>(reader: &mut R) -> Result<Self> {
-        let buf = reader.read_fixed_bytes(SECRET_KEY_SIZE)?;
-        let secp = Secp256k1::with_caps(ContextFlag::None);
-        let pk = SecretKey::from_slice(&secp, &buf).map_err(|_| ErrorKind::CorruptedData)?;
-        Ok(pk)
-    }
-}
-
-impl Writeable for SecretKey {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        writer.write_fixed_bytes(self.0)?;
 		Ok(())
 	}
 }

src/ser.rs

@@ -1,624 +0,0 @@
-// Copyright 2021 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.
-
-//! Serialization and deserialization layer specialized for binary encoding.
-//! Ensures consistency and safety. Basically a minimal subset or
-//! rustc_serialize customized for our need.
-//!
-//! To use it simply implement `Writeable` or `Readable` and then use the
-//! `serialize` or `deserialize` functions on them as appropriate.
-
-use crate::error::{Error, ErrorKind, Result};
-use byteorder::{BigEndian, ByteOrder, ReadBytesExt};
-use bytes::Buf;
-use std::io::{self, Read, Write};
-use std::marker;
-
-/// Implementations defined how different numbers and binary structures are
-/// written to an underlying stream or container (depending on implementation).
-pub trait Writer {
-    /// Writes a u8 as bytes
-    fn write_u8(&mut self, n: u8) -> Result<()> {
-        self.write_fixed_bytes(&[n])
-    }
-
-    /// Writes a u16 as bytes
-    fn write_u16(&mut self, n: u16) -> Result<()> {
-        let mut bytes = [0; 2];
-        BigEndian::write_u16(&mut bytes, n);
-        self.write_fixed_bytes(&bytes)
-    }
-
-    /// Writes a u32 as bytes
-    fn write_u32(&mut self, n: u32) -> Result<()> {
-        let mut bytes = [0; 4];
-        BigEndian::write_u32(&mut bytes, n);
-        self.write_fixed_bytes(&bytes)
-    }
-
-    /// Writes a u32 as bytes
-    fn write_i32(&mut self, n: i32) -> Result<()> {
-        let mut bytes = [0; 4];
-        BigEndian::write_i32(&mut bytes, n);
-        self.write_fixed_bytes(&bytes)
-    }
-
-    /// Writes a u64 as bytes
-    fn write_u64(&mut self, n: u64) -> Result<()> {
-        let mut bytes = [0; 8];
-        BigEndian::write_u64(&mut bytes, n);
-        self.write_fixed_bytes(&bytes)
-    }
-
-    /// Writes a i64 as bytes
-    fn write_i64(&mut self, n: i64) -> Result<()> {
-        let mut bytes = [0; 8];
-        BigEndian::write_i64(&mut bytes, n);
-        self.write_fixed_bytes(&bytes)
-    }
-
-    /// Writes a variable number of bytes. The length is encoded as a 64-bit
-    /// prefix.
-    fn write_bytes<T: AsRef<[u8]>>(&mut self, bytes: T) -> Result<()> {
-        self.write_u64(bytes.as_ref().len() as u64)?;
-        self.write_fixed_bytes(bytes)
-    }
-
-    /// Writes a fixed number of bytes. The reader is expected to know the actual length on read.
-    fn write_fixed_bytes<T: AsRef<[u8]>>(&mut self, bytes: T) -> Result<()>;
-
-    /// Writes a fixed length of "empty" bytes.
-    fn write_empty_bytes(&mut self, length: usize) -> Result<()> {
-        self.write_fixed_bytes(vec![0u8; length])
-    }
-}
-
-/// Implementations defined how different numbers and binary structures are
-/// read from an underlying stream or container (depending on implementation).
-pub trait Reader {
-    /// Read a u8 from the underlying Read
-    fn read_u8(&mut self) -> Result<u8>;
-    /// Read a u16 from the underlying Read
-    fn read_u16(&mut self) -> Result<u16>;
-    /// Read a u32 from the underlying Read
-    fn read_u32(&mut self) -> Result<u32>;
-    /// Read a u64 from the underlying Read
-    fn read_u64(&mut self) -> Result<u64>;
-    /// Read a i32 from the underlying Read
-    fn read_i32(&mut self) -> Result<i32>;
-    /// Read a i64 from the underlying Read
-    fn read_i64(&mut self) -> Result<i64>;
-    /// Read a u64 len prefix followed by that number of exact bytes.
-    fn read_bytes_len_prefix(&mut self) -> Result<Vec<u8>>;
-    /// Read a fixed number of bytes from the underlying reader.
-    fn read_fixed_bytes(&mut self, length: usize) -> Result<Vec<u8>>;
-    /// Consumes a byte from the reader, producing an error if it doesn't have
-    /// the expected value
-    fn expect_u8(&mut self, val: u8) -> Result<u8>;
-
-    /// Read a fixed number of "empty" bytes from the underlying reader.
-    /// It is an error if any non-empty bytes encountered.
-    fn read_empty_bytes(&mut self, length: usize) -> Result<()> {
-        for _ in 0..length {
-            if self.read_u8()? != 0u8 {
-                return Err(ErrorKind::CorruptedData.into());
-            }
-        }
-        Ok(())
-    }
-}
-
-/// Trait that every type that can be serialized as binary must implement.
-/// Writes directly to a Writer, a utility type thinly wrapping an
-/// underlying Write implementation.
-pub trait Writeable {
-    /// Write the data held by this Writeable to the provided writer
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()>;
-}
-
-/// Reader that exposes an Iterator interface.
-pub struct IteratingReader<'a, T, R: Reader> {
-    count: u64,
-    curr: u64,
-    reader: &'a mut R,
-    _marker: marker::PhantomData<T>,
-}
-
-impl<'a, T, R: Reader> IteratingReader<'a, T, R> {
-    /// Constructor to create a new iterating reader for the provided underlying reader.
-    /// Takes a count so we know how many to iterate over.
-    pub fn new(reader: &'a mut R, count: u64) -> Self {
-        let curr = 0;
-        IteratingReader {
-            count,
-            curr,
-            reader,
-            _marker: marker::PhantomData,
-        }
-    }
-}
-
-impl<'a, T, R> Iterator for IteratingReader<'a, T, R>
-where
-    T: Readable,
-    R: Reader,
-{
-    type Item = T;
-
-    fn next(&mut self) -> Option<T> {
-        if self.curr >= self.count {
-            return None;
-        }
-        self.curr += 1;
-        T::read(self.reader).ok()
-    }
-}
-
-/// Reads multiple serialized items into a Vec.
-pub fn read_multi<T, R>(reader: &mut R, count: u64) -> Result<Vec<T>>
-where
-    T: Readable,
-    R: Reader,
-{
-    // Very rudimentary check to ensure we do not overflow anything
-    // attempting to read huge amounts of data.
-    // Probably better than checking if count * size overflows a u64 though.
-    if count > 1_000_000 {
-        return Err(ErrorKind::TooLargeReadErr.into());
-    }
-
-    let res: Vec<T> = IteratingReader::new(reader, count).collect();
-    if res.len() as u64 != count {
-        return Err(ErrorKind::CountError.into());
-    }
-    Ok(res)
-}
-
-/// Trait that every type that can be deserialized from binary must implement.
-/// Reads directly to a Reader, a utility type thinly wrapping an
-/// underlying Read implementation.
-pub trait Readable
-where
-    Self: Sized,
-{
-    /// Reads the data necessary to this Readable from the provided reader
-    fn read<R: Reader>(reader: &mut R) -> Result<Self>;
-}
-
-/// Deserializes a Readable from any std::io::Read implementation.
-pub fn deserialize<T: Readable, R: Read>(source: &mut R) -> Result<T> {
-    let mut reader = BinReader::new(source);
-    T::read(&mut reader)
-}
-
-/// Serializes a Writeable into any std::io::Write implementation.
-pub fn serialize<W: Writeable>(sink: &mut dyn Write, thing: &W) -> Result<()> {
-    let mut writer = BinWriter::new(sink);
-    thing.write(&mut writer)
-}
-
-/// Utility function to serialize a writeable directly in memory using a
-/// Vec<u8>.
-pub fn ser_vec<W: Writeable>(thing: &W) -> Result<Vec<u8>> {
-    let mut vec = vec![];
-    serialize(&mut vec, thing)?;
-    Ok(vec)
-}
-
-/// Utility to read from a binary source
-pub struct BinReader<'a, R: Read> {
-    source: &'a mut R,
-}
-
-impl<'a, R: Read> BinReader<'a, R> {
-    /// Constructor for a new BinReader for the provided source.
-    pub fn new(source: &'a mut R) -> Self {
-        BinReader { source }
-    }
-}
-
-fn map_io_err(err: io::Error) -> Error {
-    ErrorKind::IOErr(format!("{}", err), err.kind()).into()
-}
-
-/// Utility wrapper for an underlying byte Reader. Defines higher level methods
-/// to read numbers, byte vectors, hashes, etc.
-impl<'a, R: Read> Reader for BinReader<'a, R> {
-    fn read_u8(&mut self) -> Result<u8> {
-        self.source.read_u8().map_err(map_io_err)
-    }
-    fn read_u16(&mut self) -> Result<u16> {
-        self.source.read_u16::<BigEndian>().map_err(map_io_err)
-    }
-    fn read_u32(&mut self) -> Result<u32> {
-        self.source.read_u32::<BigEndian>().map_err(map_io_err)
-    }
-    fn read_i32(&mut self) -> Result<i32> {
-        self.source.read_i32::<BigEndian>().map_err(map_io_err)
-    }
-    fn read_u64(&mut self) -> Result<u64> {
-        self.source.read_u64::<BigEndian>().map_err(map_io_err)
-    }
-    fn read_i64(&mut self) -> Result<i64> {
-        self.source.read_i64::<BigEndian>().map_err(map_io_err)
-    }
-    /// Read a variable size vector from the underlying Read. Expects a usize
-    fn read_bytes_len_prefix(&mut self) -> Result<Vec<u8>> {
-        let len = self.read_u64()?;
-        self.read_fixed_bytes(len as usize)
-    }
-
-    /// Read a fixed number of bytes.
-    fn read_fixed_bytes(&mut self, len: usize) -> Result<Vec<u8>> {
-        // not reading more than 100k bytes in a single read
-        if len > 100_000 {
-            return Err(ErrorKind::TooLargeReadErr.into());
-        }
-        let mut buf = vec![0; len];
-        self.source
-            .read_exact(&mut buf)
-            .map(move |_| buf)
-            .map_err(map_io_err)
-    }
-
-    fn expect_u8(&mut self, val: u8) -> Result<u8> {
-        let b = self.read_u8()?;
-        if b == val {
-            Ok(b)
-        } else {
-            Err(ErrorKind::UnexpectedData {
-                expected: vec![val],
-                received: vec![b],
-            }.into())
-        }
-    }
-}
-
-/// A reader that reads straight off a stream.
-/// Tracks total bytes read so we can verify we read the right number afterwards.
-pub struct StreamingReader<'a> {
-    total_bytes_read: u64,
-    stream: &'a mut dyn Read,
-}
-
-impl<'a> StreamingReader<'a> {
-    /// Create a new streaming reader with the provided underlying stream.
-    /// Also takes a duration to be used for each individual read_exact call.
-    pub fn new(stream: &'a mut dyn Read) -> StreamingReader<'a> {
-        StreamingReader {
-            total_bytes_read: 0,
-            stream,
-        }
-    }
-
-    /// Returns the total bytes read via this streaming reader.
-    pub fn total_bytes_read(&self) -> u64 {
-        self.total_bytes_read
-    }
-}
-
-/// Note: We use read_fixed_bytes() here to ensure our "async" I/O behaves as expected.
-impl<'a> Reader for StreamingReader<'a> {
-    fn read_u8(&mut self) -> Result<u8> {
-        let buf = self.read_fixed_bytes(1)?;
-        Ok(buf[0])
-    }
-    fn read_u16(&mut self) -> Result<u16> {
-        let buf = self.read_fixed_bytes(2)?;
-        Ok(BigEndian::read_u16(&buf[..]))
-    }
-    fn read_u32(&mut self) -> Result<u32> {
-        let buf = self.read_fixed_bytes(4)?;
-        Ok(BigEndian::read_u32(&buf[..]))
-    }
-    fn read_i32(&mut self) -> Result<i32> {
-        let buf = self.read_fixed_bytes(4)?;
-        Ok(BigEndian::read_i32(&buf[..]))
-    }
-    fn read_u64(&mut self) -> Result<u64> {
-        let buf = self.read_fixed_bytes(8)?;
-        Ok(BigEndian::read_u64(&buf[..]))
-    }
-    fn read_i64(&mut self) -> Result<i64> {
-        let buf = self.read_fixed_bytes(8)?;
-        Ok(BigEndian::read_i64(&buf[..]))
-    }
-
-    /// Read a variable size vector from the underlying stream. Expects a usize
-    fn read_bytes_len_prefix(&mut self) -> Result<Vec<u8>> {
-        let len = self.read_u64()?;
-        self.total_bytes_read += 8;
-        self.read_fixed_bytes(len as usize)
-    }
-
-    /// Read a fixed number of bytes.
-    fn read_fixed_bytes(&mut self, len: usize) -> Result<Vec<u8>> {
-        let mut buf = vec![0u8; len];
-        self.stream.read_exact(&mut buf)?;
-        self.total_bytes_read += len as u64;
-        Ok(buf)
-    }
-
-    fn expect_u8(&mut self, val: u8) -> Result<u8> {
-        let b = self.read_u8()?;
-        if b == val {
-            Ok(b)
-        } else {
-            Err(ErrorKind::UnexpectedData {
-                expected: vec![val],
-                received: vec![b],
-            }.into())
-        }
-    }
-}
-
-/// Protocol version-aware wrapper around a `Buf` impl
-pub struct BufReader<'a, B: Buf> {
-    inner: &'a mut B,
-    bytes_read: usize,
-}
-
-impl<'a, B: Buf> BufReader<'a, B> {
-    /// Construct a new BufReader
-    pub fn new(buf: &'a mut B) -> Self {
-        Self {
-            inner: buf,
-            bytes_read: 0,
-        }
-    }
-
-    /// Check whether the buffer has enough bytes remaining to perform a read
-    fn has_remaining(&mut self, len: usize) -> Result<()> {
-        if self.inner.remaining() >= len {
-            self.bytes_read += len;
-            Ok(())
-        } else {
-            Err(io::ErrorKind::UnexpectedEof.into())
-        }
-    }
-
-    /// The total bytes read
-    pub fn bytes_read(&self) -> u64 {
-        self.bytes_read as u64
-    }
-
-    /// Convenience function to read from the buffer and deserialize
-    pub fn body<T: Readable>(&mut self) -> Result<T> {
-        T::read(self)
-    }
-}
-
-impl<'a, B: Buf> Reader for BufReader<'a, B> {
-    fn read_u8(&mut self) -> Result<u8> {
-        self.has_remaining(1)?;
-        Ok(self.inner.get_u8())
-    }
-
-    fn read_u16(&mut self) -> Result<u16> {
-        self.has_remaining(2)?;
-        Ok(self.inner.get_u16())
-    }
-
-    fn read_u32(&mut self) -> Result<u32> {
-        self.has_remaining(4)?;
-        Ok(self.inner.get_u32())
-    }
-
-    fn read_u64(&mut self) -> Result<u64> {
-        self.has_remaining(8)?;
-        Ok(self.inner.get_u64())
-    }
-
-    fn read_i32(&mut self) -> Result<i32> {
-        self.has_remaining(4)?;
-        Ok(self.inner.get_i32())
-    }
-
-    fn read_i64(&mut self) -> Result<i64> {
-        self.has_remaining(8)?;
-        Ok(self.inner.get_i64())
-    }
-
-    fn read_bytes_len_prefix(&mut self) -> Result<Vec<u8>> {
-        let len = self.read_u64()?;
-        self.read_fixed_bytes(len as usize)
-    }
-
-    fn read_fixed_bytes(&mut self, len: usize) -> Result<Vec<u8>> {
-        // not reading more than 100k bytes in a single read
-        if len > 100_000 {
-            return Err(ErrorKind::TooLargeReadErr.into());
-        }
-        self.has_remaining(len)?;
-
-        let mut buf = vec![0; len];
-        self.inner.copy_to_slice(&mut buf[..]);
-        Ok(buf)
-    }
-
-    fn expect_u8(&mut self, val: u8) -> Result<u8> {
-        let b = self.read_u8()?;
-        if b == val {
-            Ok(b)
-        } else {
-            Err(ErrorKind::UnexpectedData {
-                expected: vec![val],
-                received: vec![b],
-            }.into())
-        }
-    }
-}
-
-/// Utility wrapper for an underlying byte Writer. Defines higher level methods
-/// to write numbers, byte vectors, hashes, etc.
-pub struct BinWriter<'a> {
-    sink: &'a mut dyn Write,
-}
-
-impl<'a> BinWriter<'a> {
-    /// Wraps a standard Write in a new BinWriter
-    pub fn new(sink: &'a mut dyn Write) -> BinWriter<'a> {
-        BinWriter { sink }
-    }
-}
-
-impl<'a> Writer for BinWriter<'a> {
-    fn write_fixed_bytes<T: AsRef<[u8]>>(&mut self, bytes: T) -> Result<()> {
-        self.sink.write_all(bytes.as_ref())?;
-        Ok(())
-    }
-}
-
-macro_rules! impl_int {
-    ($int:ty, $w_fn:ident, $r_fn:ident) => {
-        impl Writeable for $int {
-            fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-                writer.$w_fn(*self)
-            }
-        }
-
-        impl Readable for $int {
-            fn read<R: Reader>(reader: &mut R) -> Result<$int> {
-                reader.$r_fn()
-            }
-        }
-    };
-}
-
-impl_int!(u8, write_u8, read_u8);
-impl_int!(u16, write_u16, read_u16);
-impl_int!(u32, write_u32, read_u32);
-impl_int!(i32, write_i32, read_i32);
-impl_int!(u64, write_u64, read_u64);
-impl_int!(i64, write_i64, read_i64);
-
-impl<T> Readable for Vec<T>
-where
-    T: Readable,
-{
-    fn read<R: Reader>(reader: &mut R) -> Result<Vec<T>> {
-        let mut buf = Vec::new();
-        loop {
-            let elem = T::read(reader);
-            match elem {
-                Ok(e) => buf.push(e),
-                // Err(ErrorKind::IOErr(ref _d, ref kind)) if *kind == io::ErrorKind::UnexpectedEof => {
-                // 	break;
-                // }
-                Err(e) => {
-                    match e.kind() {
-                        ErrorKind::IOErr(ref _d, ref kind) if *kind == io::ErrorKind::UnexpectedEof => {
-                            break;
-                        },
-                        _ => return Err(e),
-                    }
-                },
-            }
-        }
-        Ok(buf)
-    }
-}
-
-impl<T> Writeable for Vec<T>
-where
-    T: Writeable,
-{
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        for elmt in self {
-            elmt.write(writer)?;
-        }
-        Ok(())
-    }
-}
-
-impl<'a, A: Writeable> Writeable for &'a A {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        Writeable::write(*self, writer)
-    }
-}
-
-impl<A: Writeable, B: Writeable> Writeable for (A, B) {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        Writeable::write(&self.0, writer)?;
-        Writeable::write(&self.1, writer)
-    }
-}
-
-impl<A: Readable, B: Readable> Readable for (A, B) {
-    fn read<R: Reader>(reader: &mut R) -> Result<(A, B)> {
-        Ok((Readable::read(reader)?, Readable::read(reader)?))
-    }
-}
-
-impl<A: Writeable, B: Writeable, C: Writeable> Writeable for (A, B, C) {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        Writeable::write(&self.0, writer)?;
-        Writeable::write(&self.1, writer)?;
-        Writeable::write(&self.2, writer)
-    }
-}
-
-impl<A: Writeable, B: Writeable, C: Writeable, D: Writeable> Writeable for (A, B, C, D) {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
-        Writeable::write(&self.0, writer)?;
-        Writeable::write(&self.1, writer)?;
-        Writeable::write(&self.2, writer)?;
-        Writeable::write(&self.3, writer)
-    }
-}
-
-impl<A: Readable, B: Readable, C: Readable> Readable for (A, B, C) {
-    fn read<R: Reader>(reader: &mut R) -> Result<(A, B, C)> {
-        Ok((
-            Readable::read(reader)?,
-            Readable::read(reader)?,
-            Readable::read(reader)?,
-        ))
-    }
-}
-
-impl<A: Readable, B: Readable, C: Readable, D: Readable> Readable for (A, B, C, D) {
-    fn read<R: Reader>(reader: &mut R) -> Result<(A, B, C, D)> {
-        Ok((
-            Readable::read(reader)?,
-            Readable::read(reader)?,
-            Readable::read(reader)?,
-            Readable::read(reader)?,
-        ))
-    }
-}
-
-/// Serializes a Vec<u8> to and from hex
-pub mod vec_serde {
-    use serde::{Deserialize, Serializer};
-    use grin_util::ToHex;
-
-    /// Serializes a Vec<u8> as a hex string
-    pub fn serialize<S>(bytes: &Vec<u8>, serializer: S) -> Result<S::Ok, S::Error>
-    where
-        S: Serializer,
-    {
-        serializer.serialize_str(&bytes.to_hex())
-    }
-
-    /// Creates a Vec<u8> from a hex string
-    pub fn deserialize<'de, D>(deserializer: D) -> std::result::Result<Vec<u8>, D::Error>
-    where
-        D: serde::Deserializer<'de>,
-    {
-        use serde::de::Error;
-        String::deserialize(deserializer)
-            .and_then(|string| grin_util::from_hex(&string).map_err(Error::custom))
-    }
-}

src/server.rs

@@ -1,213 +1,649 @@
-use crate::onion;
-use crate::secp::{self, Commitment, ComSignature, SecretKey};
-use crate::ser;
-use crate::types::Onion;
+use crate::config::ServerConfig;
+use crate::node::{self, GrinNode};
+use crate::onion::Onion;
+use crate::secp::{ComSignature, Commitment, RangeProof, Secp256k1, SecretKey};
+use crate::wallet::{self, Wallet};
 
-use jsonrpc_derive::rpc;
-use jsonrpc_http_server::*;
-use jsonrpc_http_server::jsonrpc_core::*;
-use jsonrpc_core::{Result, Value};
-use serde::{Deserialize, Serialize};
-use std::net::SocketAddr;
-use std::sync::Mutex;
+use grin_core::core::{Input, Output, OutputFeatures, TransactionBody};
+use grin_core::global::DEFAULT_ACCEPT_FEE_BASE;
+use itertools::Itertools;
+use std::collections::HashMap;
+use std::result::Result;
+use std::sync::{Arc, Mutex};
+use thiserror::Error;
 
 #[derive(Clone, Debug, PartialEq)]
-pub struct ServerConfig {
-    pub key: SecretKey,
-    pub addr: SocketAddr,
-    pub is_first: bool,
+struct Submission {
+	/// The total excess for the output commitment
+	excess: SecretKey,
+	/// The derived output commitment after applying excess and fee
+	output_commit: Commitment,
+	/// The rangeproof, included only for the final hop (node N)
+	rangeproof: Option<RangeProof>,
+	/// Transaction input being spent
+	input: Input,
+	/// Transaction fee
+	fee: u64,
+	/// The remaining onion after peeling off our layer
+	onion: Onion,
 }
 
-pub struct Submission {
-    pub excess: SecretKey,
-    pub input_commit: Commitment,
-    pub onion: Onion,
+/// Swap error types
+#[derive(Clone, Error, Debug, PartialEq)]
+pub enum SwapError {
+	#[error("Invalid number of payloads provided (expected {expected:?}, found {found:?})")]
+	InvalidPayloadLength { expected: usize, found: usize },
+	#[error("Commitment Signature is invalid")]
+	InvalidComSignature,
+	#[error("Rangeproof is invalid")]
+	InvalidRangeproof,
+	#[error("Rangeproof is required but was not supplied")]
+	MissingRangeproof,
+	#[error("Output {commit:?} does not exist, or is already spent.")]
+	CoinNotFound { commit: Commitment },
+	#[error("Output {commit:?} is already in the swap list.")]
+	AlreadySwapped { commit: Commitment },
+	#[error("Failed to peel onion layer: {0}")]
+	PeelOnionFailure(String),
+	#[error("Fee too low (expected >= {minimum_fee:?}, actual {actual_fee:?})")]
+	FeeTooLow { minimum_fee: u64, actual_fee: u64 },
+	#[error("{0}")]
+	UnknownError(String),
 }
 
-#[derive(Serialize, Deserialize)]
-pub struct SwapReq {
-    pub onion: Onion,
-    #[serde(with = "ser::vec_serde")]
-    pub msg: Vec<u8>,
-    #[serde(with = "secp::comsig_serde")]
-    pub comsig: ComSignature,
-}
-
-lazy_static! {
-    static ref SERVER_STATE: Mutex<Vec<Submission>> = Mutex::new(Vec::new());
-}
-
-#[rpc(server)]
-pub trait Server {
-    #[rpc(name = "swap")]
-    fn swap(&self, swap: SwapReq) -> Result<Value>;
-
-    // milestone 3:
-    // fn derive_outputs(&self, entries: Vec<Onion>) -> Result<Value>;
-    // fn derive_kernel(&self, tx: Tx) -> Result<Value>;
+/// A MWixnet server
+pub trait Server: Send + Sync {
+	/// Submit a new output to be swapped.
+	fn swap(&self, onion: &Onion, comsig: &ComSignature) -> Result<(), SwapError>;
+
+	/// Iterate through all saved submissions, filter out any inputs that are no longer spendable,
+	/// and assemble the coinswap transaction, posting the transaction to the configured node.
+	///
+	/// Currently only a single mix node is used. Milestone 3 will include support for multiple mix nodes.
+	fn execute_round(&self) -> crate::error::Result<()>;
 }
 
+/// The standard MWixnet server implementation
+#[derive(Clone)]
 pub struct ServerImpl {
-    server_key: SecretKey,
+	server_config: ServerConfig,
+	wallet: Arc<dyn Wallet>,
+	node: Arc<dyn GrinNode>,
+	submissions: Arc<Mutex<HashMap<Commitment, Submission>>>,
 }
 
 impl ServerImpl {
-    pub fn new(server_key: SecretKey) -> Self {
-        ServerImpl { server_key }
+	/// Create a new MWixnet server
+	pub fn new(
+		server_config: ServerConfig,
+		wallet: Arc<dyn Wallet>,
+		node: Arc<dyn GrinNode>,
+	) -> Self {
+		ServerImpl {
+			server_config,
+			wallet,
+			node,
+			submissions: Arc::new(Mutex::new(HashMap::new())),
+		}
+	}
+
+	/// The fee base to use. For now, just using the default.
+	fn get_fee_base(&self) -> u64 {
+		DEFAULT_ACCEPT_FEE_BASE
+	}
+
+	/// Minimum fee to perform a swap.
+	/// Requires enough fee for the mwixnet server's kernel, 1 input and its output to swap.
+	fn get_minimum_swap_fee(&self) -> u64 {
+		TransactionBody::weight_by_iok(1, 1, 1) * self.get_fee_base()
 	}
 }
 
 impl Server for ServerImpl {
-    fn swap(&self, swap: SwapReq) -> Result<Value> {
-        // milestone 2 - check that commitment is unspent
+	fn swap(&self, onion: &Onion, comsig: &ComSignature) -> Result<(), SwapError> {
+		// milestone 3: check that enc_payloads length matches number of configured servers
+		if onion.enc_payloads.len() != 1 {
+			return Err(SwapError::InvalidPayloadLength {
+				expected: 1,
+				found: onion.enc_payloads.len(),
+			});
+		}
 
 		// Verify commitment signature to ensure caller owns the output
-        let _ = swap.comsig.verify(&swap.onion.commit, &swap.msg)
-            .map_err(|_| jsonrpc_core::Error::invalid_params("ComSignature invalid"))?;
+		let serialized_onion = onion
+			.serialize()
+			.map_err(|e| SwapError::UnknownError(e.to_string()))?;
+		let _ = comsig
+			.verify(&onion.commit, &serialized_onion)
+			.map_err(|_| SwapError::InvalidComSignature)?;
 
-        let peeled = onion::peel_layer(&swap.onion, &self.server_key)
-            .map_err(|e| jsonrpc_core::Error::invalid_params(e.message()))?;
-        SERVER_STATE.lock().unwrap().push(Submission{
-            excess: peeled.0.excess,
-            input_commit: swap.onion.commit,
-            onion: peeled.1
+		// Verify that commitment is unspent
+		let input = node::build_input(&self.node, &onion.commit)
+			.map_err(|e| SwapError::UnknownError(e.to_string()))?;
+		let input = input.ok_or(SwapError::CoinNotFound {
+			commit: onion.commit.clone(),
+		})?;
+
+		let peeled = onion
+			.peel_layer(&self.server_config.key)
+			.map_err(|e| SwapError::PeelOnionFailure(e.message()))?;
+
+		// Verify the fee meets the minimum
+		let fee: u64 = peeled.0.fee.into();
+		if fee < self.get_minimum_swap_fee() {
+			return Err(SwapError::FeeTooLow {
+				minimum_fee: self.get_minimum_swap_fee(),
+				actual_fee: fee,
 			});
-        Ok(Value::String("success".into()))
 		}
 
-}
-
-/// Spin up the JSON-RPC web server
-pub fn listen<F>(server_config: &ServerConfig, shutdown_signal: F) -> std::result::Result<(), Box<dyn std::error::Error>>
-where
-    F: futures::future::Future<Output = ()> + Send + 'static,
-{
-    let mut io = IoHandler::new();
-    io.extend_with(ServerImpl::to_delegate(ServerImpl::new(server_config.key.clone())));
-
-    let server = ServerBuilder::new(io)
-        .cors(DomainsValidation::Disabled)
-        .request_middleware(|request: hyper::Request<hyper::Body>| {
-            if request.uri() == "/v1" {
-                request.into()
+		// Verify the bullet proof and build the final output
+		if let Some(r) = peeled.0.rangeproof {
+			let secp = Secp256k1::with_caps(secp256k1zkp::ContextFlag::Commit);
+			secp.verify_bullet_proof(peeled.1.commit, r, None)
+				.map_err(|_| SwapError::InvalidRangeproof)?;
 		} else {
-                jsonrpc_http_server::Response::bad_request("Only v1 supported").into()
+			// milestone 3: only the last hop will have a rangeproof
+			return Err(SwapError::MissingRangeproof);
 		}
-        })
-        .start_http(&server_config.addr)
-        .expect("Unable to start RPC server");
 
-    let close_handle = server.close_handle();
-    std::thread::spawn(move || {
-        futures::executor::block_on(shutdown_signal);
-        close_handle.close();
+		let mut locked = self.submissions.lock().unwrap();
+		if locked.contains_key(&onion.commit) {
+			return Err(SwapError::AlreadySwapped {
+				commit: onion.commit.clone(),
 			});
-    server.wait();
+		}
+
+		locked.insert(
+			onion.commit,
+			Submission {
+				excess: peeled.0.excess,
+				output_commit: peeled.1.commit,
+				rangeproof: peeled.0.rangeproof,
+				input,
+				fee,
+				onion: peeled.1,
+			},
+		);
+		Ok(())
+	}
+
+	fn execute_round(&self) -> crate::error::Result<()> {
+		let mut locked_state = self.submissions.lock().unwrap();
+		let next_block_height = self.node.get_chain_height()? + 1;
+
+		let spendable: Vec<Submission> = locked_state
+			.values()
+			.into_iter()
+			.unique_by(|s| s.output_commit)
+			.filter(|s| {
+				node::is_spendable(&self.node, &s.input.commit, next_block_height).unwrap_or(false)
+			})
+			.filter(|s| !node::is_unspent(&self.node, &s.output_commit).unwrap_or(true))
+			.cloned()
+			.collect();
+
+		if spendable.len() == 0 {
+			return Ok(());
+		}
+
+		let total_fee: u64 = spendable.iter().enumerate().map(|(_, s)| s.fee).sum();
+
+		let inputs: Vec<Input> = spendable.iter().enumerate().map(|(_, s)| s.input).collect();
+
+		let outputs: Vec<Output> = spendable
+			.iter()
+			.enumerate()
+			.map(|(_, s)| {
+				Output::new(
+					OutputFeatures::Plain,
+					s.output_commit,
+					s.rangeproof.unwrap(),
+				)
+			})
+			.collect();
+
+		let excesses: Vec<SecretKey> = spendable
+			.iter()
+			.enumerate()
+			.map(|(_, s)| s.excess.clone())
+			.collect();
+
+		let tx = wallet::assemble_tx(
+			&self.wallet,
+			&inputs,
+			&outputs,
+			self.get_fee_base(),
+			total_fee,
+			&excesses,
+		)?;
+
+		self.node.post_tx(&tx)?;
+		locked_state.clear();
 
 		Ok(())
+	}
+}
+
+#[cfg(test)]
+pub mod mock {
+	use super::{Server, SwapError};
+	use crate::onion::Onion;
+	use crate::secp::ComSignature;
+
+	use std::collections::HashMap;
+
+	pub struct MockServer {
+		errors: HashMap<Onion, SwapError>,
+	}
+
+	impl MockServer {
+		pub fn new() -> MockServer {
+			MockServer {
+				errors: HashMap::new(),
+			}
+		}
+
+		pub fn set_response(&mut self, onion: &Onion, e: SwapError) {
+			self.errors.insert(onion.clone(), e);
+		}
+	}
+
+	impl Server for MockServer {
+		fn swap(&self, onion: &Onion, _comsig: &ComSignature) -> Result<(), SwapError> {
+			if let Some(e) = self.errors.get(&onion) {
+				return Err(e.clone());
+			}
+
+			Ok(())
+		}
+
+		fn execute_round(&self) -> crate::error::Result<()> {
+			Ok(())
+		}
+	}
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::{onion, secp, server, types};
+	use crate::config::ServerConfig;
+	use crate::node::mock::MockGrinNode;
+	use crate::onion::test_util::{self, Hop};
+	use crate::onion::Onion;
+	use crate::secp::{
+		self, ComSignature, Commitment, PublicKey, RangeProof, Secp256k1, SecretKey,
+	};
+	use crate::server::{Server, ServerImpl, Submission, SwapError};
+	use crate::types::Payload;
+	use crate::wallet::mock::MockWallet;
+
+	use grin_core::core::{Committed, FeeFields, Input, OutputFeatures, Transaction, Weighting};
+	use grin_core::global::{self, ChainTypes};
 	use std::net::TcpListener;
-    use std::time::Duration;
-    use std::thread;
+	use std::sync::Arc;
 
-    use hyper::{Body, Client, Request, Response};
-    use tokio::runtime;
-
-    async fn body_to_string(req: Response<Body>) -> String {
-        let body_bytes = hyper::body::to_bytes(req.into_body()).await.unwrap();
-        String::from_utf8(body_bytes.to_vec()).unwrap()
+	macro_rules! assert_error_type {
+		($result:expr, $error_type:pat) => {
+			assert!($result.is_err());
+			assert!(if let $error_type = $result.unwrap_err() {
+				true
+			} else {
+				false
+			});
+		};
 	}
 
-    /// Spin up a temporary web service, query the API, then cleanup and return response
-    fn make_request(server_key: secp::SecretKey, req: String) -> Result<String, Box<dyn std::error::Error>> {
-        let server_config = server::ServerConfig { 
-            key: server_key,
-            addr: TcpListener::bind("127.0.0.1:0")?.local_addr()?,
-            is_first: true
+	fn new_server(
+		server_key: &SecretKey,
+		utxos: &Vec<&Commitment>,
+	) -> (ServerImpl, Arc<MockGrinNode>) {
+		let config = ServerConfig {
+			key: server_key.clone(),
+			interval_s: 1,
+			addr: TcpListener::bind("127.0.0.1:0")
+				.unwrap()
+				.local_addr()
+				.unwrap(),
+			grin_node_url: "127.0.0.1:3413".parse().unwrap(),
+			grin_node_secret_path: None,
+			wallet_owner_url: "127.0.0.1:3420".parse().unwrap(),
+			wallet_owner_secret_path: None,
 		};
+		let wallet = Arc::new(MockWallet {});
+		let mut mut_node = MockGrinNode::new();
+		for utxo in utxos {
+			mut_node.add_default_utxo(&utxo);
+		}
+		let node = Arc::new(mut_node);
 
-        let threaded_rt = runtime::Runtime::new()?;
-        let (shutdown_sender, shutdown_receiver) = futures::channel::oneshot::channel();
-        let uri = format!("http://{}/v1", server_config.addr);
+		let server = ServerImpl::new(config, wallet.clone(), node.clone());
+		(server, node)
+	}
 
-        // Spawn the server task
-        threaded_rt.spawn(async move {
-            server::listen(&server_config, async { shutdown_receiver.await.ok(); }).unwrap()
-        });
+	fn proof(value: u64, fee: u64, input_blind: &SecretKey, hop_excess: &SecretKey) -> RangeProof {
+		let secp = Secp256k1::new();
+		let nonce = secp::random_secret();
 
-        // Wait for listener
-        thread::sleep(Duration::from_millis(500));
+		let mut blind = input_blind.clone();
+		blind.add_assign(&secp, &hop_excess).unwrap();
 
-        let do_request = async move {
-            let request = Request::post(uri)
-                .header("Content-Type", "application/json")
-                .body(Body::from(req))
-                .unwrap();
+		secp.bullet_proof(
+			value - fee,
+			blind.clone(),
+			nonce.clone(),
+			nonce.clone(),
+			None,
+			None,
+		)
+	}
 
-            Client::new().request(request).await
-        };
-
-        let response = threaded_rt.block_on(do_request)?;
-        let response_str: String = threaded_rt.block_on(body_to_string(response));
-
-        shutdown_sender.send(()).ok();
-
-        // Wait for shutdown
-        thread::sleep(Duration::from_millis(500));
-        threaded_rt.shutdown_background();
-
-        Ok(response_str)
+	fn new_hop(
+		server_key: &SecretKey,
+		hop_excess: &SecretKey,
+		fee: u64,
+		proof: Option<RangeProof>,
+	) -> Hop {
+		let secp = Secp256k1::new();
+		Hop {
+			pubkey: PublicKey::from_secret_key(&secp, &server_key).unwrap(),
+			payload: Payload {
+				excess: hop_excess.clone(),
+				fee: FeeFields::from(fee as u32),
+				rangeproof: proof,
+			},
+		}
 	}
 
 	/// Single hop to demonstrate request validation and onion unwrapping.
-    /// UTXO creation and bulletproof generation reserved for milestones 2 & 3.
 	#[test]
 	fn swap_lifecycle() -> Result<(), Box<dyn std::error::Error>> {
-        let server_key = secp::insecure_rand_secret()?;
+		let value: u64 = 200_000_000;
+		let fee: u64 = 50_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
 
-        let secp = secp::Secp256k1::new();
-        let value: u64 = 100;
-        let blind = secp::insecure_rand_secret()?;
-        let commitment = secp::commit(value, &blind)?;
-        let session_key = secp::insecure_rand_secret()?;
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let proof = proof(value, fee, &blind, &hop_excess);
+		let hop = new_hop(&server_key, &hop_excess, fee, Some(proof));
 
-        let hop = types::Hop {
-            pubkey: secp::PublicKey::from_secret_key(&secp, &server_key)?,
-            payload: types::Payload{
-                excess: secp::insecure_rand_secret()?,
-                rangeproof: None,
+		let onion = test_util::create_onion(&input_commit, &vec![hop])?;
+		let comsig = ComSignature::sign(value, &blind, &onion.serialize()?)?;
+
+		let (server, node) = new_server(&server_key, &vec![&input_commit]);
+		server.swap(&onion, &comsig)?;
+
+		// Make sure entry is added to server.
+		let output_commit = secp::add_excess(&input_commit, &hop_excess)?;
+		let output_commit = secp::sub_value(&output_commit, fee)?;
+
+		let expected = Submission {
+			excess: hop_excess.clone(),
+			output_commit: output_commit.clone(),
+			rangeproof: Some(proof),
+			input: Input::new(OutputFeatures::Plain, input_commit.clone()),
+			fee,
+			onion: Onion {
+				ephemeral_pubkey: test_util::next_ephemeral_pubkey(&onion, &server_key)?,
+				commit: output_commit.clone(),
+				enc_payloads: vec![],
+			},
+		};
+
+		{
+			let submissions = server.submissions.lock().unwrap();
+			assert_eq!(1, submissions.len());
+			assert!(submissions.contains_key(&input_commit));
+			assert_eq!(&expected, submissions.get(&input_commit).unwrap());
 		}
-        };
-        let hops: Vec<types::Hop> = vec![hop];
-        let onion_packet = onion::create_onion(&commitment, &session_key, &hops)?;
-        let msg : Vec<u8> = vec![0u8, 1u8, 2u8, 3u8];
-        let comsig = secp::ComSignature::sign(value, &blind, &msg)?;
-        let swap = server::SwapReq{
-            onion: onion_packet,
-            msg: msg,
-            comsig: comsig,
-        };
 
-        let req = format!("{{\"jsonrpc\": \"2.0\", \"method\": \"swap\", \"params\": [{}], \"id\": \"1\"}}", serde_json::json!(swap));
-        let response = make_request(server_key, req)?;
-        let expected = "{\"jsonrpc\":\"2.0\",\"result\":\"success\",\"id\":\"1\"}\n";
-        assert_eq!(response, expected);
+		server.execute_round()?;
+
+		// Make sure entry is removed from server.submissions
+		assert!(server.submissions.lock().unwrap().is_empty());
+
+		// check that the transaction was posted
+		let posted_txns = node.get_posted_txns();
+		assert_eq!(posted_txns.len(), 1);
+		let posted_txn: Transaction = posted_txns.into_iter().next().unwrap();
+		assert!(posted_txn.inputs_committed().contains(&input_commit));
+		assert!(posted_txn.outputs_committed().contains(&output_commit));
+		// todo: check that outputs also contain the commitment generated by our wallet
+
+		global::set_local_chain_type(ChainTypes::AutomatedTesting);
+		posted_txn.validate(Weighting::AsTransaction)?;
+
 		Ok(())
 	}
 
+	/// Returns InvalidPayloadLength when too many payloads are provided.
 	#[test]
-    fn swap_bad_request() -> Result<(), Box<dyn std::error::Error>> {
-        let params = "{ \"param\": \"Not a valid Swap request\" }";
-        let req = format!("{{\"jsonrpc\": \"2.0\", \"method\": \"swap\", \"params\": [{}], \"id\": \"1\"}}", params);
-        let response = make_request(secp::insecure_rand_secret()?, req)?;
-        let expected = "{\"jsonrpc\":\"2.0\",\"error\":{\"code\":-32602,\"message\":\"Invalid params: missing field `onion`.\"},\"id\":\"1\"}\n";
-        assert_eq!(response, expected);
+	fn swap_too_many_payloads() -> Result<(), Box<dyn std::error::Error>> {
+		let value: u64 = 200_000_000;
+		let fee: u64 = 50_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
+
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let proof = proof(value, fee, &blind, &hop_excess);
+		let hop = new_hop(&server_key, &hop_excess, fee, Some(proof));
+
+		let hops: Vec<Hop> = vec![hop.clone(), hop.clone()]; // Multiple payloads
+		let onion = test_util::create_onion(&input_commit, &hops)?;
+		let comsig = ComSignature::sign(value, &blind, &onion.serialize()?)?;
+
+		let (server, _node) = new_server(&server_key, &vec![&input_commit]);
+		let result = server.swap(&onion, &comsig);
+		assert_eq!(
+			Err(SwapError::InvalidPayloadLength {
+				expected: 1,
+				found: 2
+			}),
+			result
+		);
+
+		// Make sure no entry is added to server.submissions
+		assert!(server.submissions.lock().unwrap().is_empty());
+
 		Ok(())
 	}
 
-    // milestone 2 - add tests to cover invalid comsig's & inputs not in utxo set
+	/// Returns InvalidComSignature when ComSignature fails to verify.
+	#[test]
+	fn swap_invalid_com_signature() -> Result<(), Box<dyn std::error::Error>> {
+		let value: u64 = 200_000_000;
+		let fee: u64 = 50_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
+
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let proof = proof(value, fee, &blind, &hop_excess);
+		let hop = new_hop(&server_key, &hop_excess, fee, Some(proof));
+
+		let onion = test_util::create_onion(&input_commit, &vec![hop])?;
+
+		let wrong_blind = secp::random_secret();
+		let comsig = ComSignature::sign(value, &wrong_blind, &onion.serialize()?)?;
+
+		let (server, _node) = new_server(&server_key, &vec![&input_commit]);
+		let result = server.swap(&onion, &comsig);
+		assert_eq!(Err(SwapError::InvalidComSignature), result);
+
+		// Make sure no entry is added to server.submissions
+		assert!(server.submissions.lock().unwrap().is_empty());
+
+		Ok(())
+	}
+
+	/// Returns InvalidRangeProof when the rangeproof fails to verify for the commitment.
+	#[test]
+	fn swap_invalid_rangeproof() -> Result<(), Box<dyn std::error::Error>> {
+		let value: u64 = 200_000_000;
+		let fee: u64 = 50_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
+
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let wrong_value = value + 10_000_000;
+		let proof = proof(wrong_value, fee, &blind, &hop_excess);
+		let hop = new_hop(&server_key, &hop_excess, fee, Some(proof));
+
+		let onion = test_util::create_onion(&input_commit, &vec![hop])?;
+		let comsig = ComSignature::sign(value, &blind, &onion.serialize()?)?;
+
+		let (server, _node) = new_server(&server_key, &vec![&input_commit]);
+		let result = server.swap(&onion, &comsig);
+		assert_eq!(Err(SwapError::InvalidRangeproof), result);
+
+		// Make sure no entry is added to server.submissions
+		assert!(server.submissions.lock().unwrap().is_empty());
+
+		Ok(())
+	}
+
+	/// Returns MissingRangeproof when no rangeproof is provided.
+	#[test]
+	fn swap_missing_rangeproof() -> Result<(), Box<dyn std::error::Error>> {
+		let value: u64 = 200_000_000;
+		let fee: u64 = 50_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
+
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let hop = new_hop(&server_key, &hop_excess, fee, None);
+
+		let onion = test_util::create_onion(&input_commit, &vec![hop])?;
+		let comsig = ComSignature::sign(value, &blind, &onion.serialize()?)?;
+
+		let (server, _node) = new_server(&server_key, &vec![&input_commit]);
+		let result = server.swap(&onion, &comsig);
+		assert_eq!(Err(SwapError::MissingRangeproof), result);
+
+		// Make sure no entry is added to server.submissions
+		assert!(server.submissions.lock().unwrap().is_empty());
+
+		Ok(())
+	}
+
+	/// Returns CoinNotFound when there's no matching output in the UTXO set.
+	#[test]
+	fn swap_utxo_missing() -> Result<(), Box<dyn std::error::Error>> {
+		let value: u64 = 200_000_000;
+		let fee: u64 = 50_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
+
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let proof = proof(value, fee, &blind, &hop_excess);
+		let hop = new_hop(&server_key, &hop_excess, fee, Some(proof));
+
+		let onion = test_util::create_onion(&input_commit, &vec![hop])?;
+		let comsig = ComSignature::sign(value, &blind, &onion.serialize()?)?;
+
+		let (server, _node) = new_server(&server_key, &vec![]);
+		let result = server.swap(&onion, &comsig);
+		assert_eq!(
+			Err(SwapError::CoinNotFound {
+				commit: input_commit.clone()
+			}),
+			result
+		);
+
+		// Make sure no entry is added to server.submissions
+		assert!(server.submissions.lock().unwrap().is_empty());
+
+		Ok(())
+	}
+
+	/// Returns AlreadySwapped when trying to swap the same commitment multiple times.
+	#[test]
+	fn swap_already_swapped() -> Result<(), Box<dyn std::error::Error>> {
+		let value: u64 = 200_000_000;
+		let fee: u64 = 50_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
+
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let proof = proof(value, fee, &blind, &hop_excess);
+		let hop = new_hop(&server_key, &hop_excess, fee, Some(proof));
+
+		let onion = test_util::create_onion(&input_commit, &vec![hop])?;
+		let comsig = ComSignature::sign(value, &blind, &onion.serialize()?)?;
+
+		let (server, _node) = new_server(&server_key, &vec![&input_commit]);
+		server.swap(&onion, &comsig)?;
+
+		// Call swap a second time
+		let result = server.swap(&onion, &comsig);
+		assert_eq!(
+			Err(SwapError::AlreadySwapped {
+				commit: input_commit.clone()
+			}),
+			result
+		);
+
+		Ok(())
+	}
+
+	/// Returns PeelOnionFailure when a failure occurs trying to decrypt the onion payload.
+	#[test]
+	fn swap_peel_onion_failure() -> Result<(), Box<dyn std::error::Error>> {
+		let value: u64 = 200_000_000;
+		let fee: u64 = 50_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
+
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let proof = proof(value, fee, &blind, &hop_excess);
+
+		let wrong_server_key = secp::random_secret();
+		let hop = new_hop(&wrong_server_key, &hop_excess, fee, Some(proof));
+
+		let onion = test_util::create_onion(&input_commit, &vec![hop])?;
+		let comsig = ComSignature::sign(value, &blind, &onion.serialize()?)?;
+
+		let (server, _node) = new_server(&server_key, &vec![&input_commit]);
+		let result = server.swap(&onion, &comsig);
+
+		assert!(result.is_err());
+		assert_error_type!(result, SwapError::PeelOnionFailure(_));
+
+		Ok(())
+	}
+
+	/// Returns FeeTooLow when the minimum fee is not met.
+	#[test]
+	fn swap_fee_too_low() -> Result<(), Box<dyn std::error::Error>> {
+		let value: u64 = 200_000_000;
+		let fee: u64 = 1_000_000;
+		let blind = secp::random_secret();
+		let input_commit = secp::commit(value, &blind)?;
+
+		let server_key = secp::random_secret();
+		let hop_excess = secp::random_secret();
+		let proof = proof(value, fee, &blind, &hop_excess);
+		let hop = new_hop(&server_key, &hop_excess, fee, Some(proof));
+
+		let onion = test_util::create_onion(&input_commit, &vec![hop])?;
+		let comsig = ComSignature::sign(value, &blind, &onion.serialize()?)?;
+
+		let (server, _node) = new_server(&server_key, &vec![&input_commit]);
+		let result = server.swap(&onion, &comsig);
+		assert_eq!(
+			Err(SwapError::FeeTooLow {
+				minimum_fee: 12_500_000,
+				actual_fee: fee
+			}),
+			result
+		);
+
+		Ok(())
+	}
 }

src/types.rs

@@ -1,30 +1,42 @@
-use crate::error::{ErrorKind, Result};
-use crate::secp::{Commitment, PublicKey, RangeProof, SecretKey, Secp256k1};
-use crate::ser::{self, BinReader, Readable, Reader, Writeable, Writer};
-use grin_util::{self, ToHex};
+use crate::error::{Result, StdResult};
+use crate::secp::{self, RangeProof, SecretKey};
+
+use grin_core::core::FeeFields;
+use grin_core::ser::{self, Readable, Reader, Writeable, Writer};
 use serde::{Deserialize, Serialize};
-use serde::ser::SerializeStruct;
-use std::fmt;
-use std::io::Cursor;
 
-pub type RawBytes = Vec<u8>;
-
-const CURRENT_VERSION : u8 = 0;
+const CURRENT_VERSION: u8 = 0;
 
 #[derive(Serialize, Deserialize, Debug, Clone)]
 pub struct Payload {
 	pub excess: SecretKey,
+	pub fee: FeeFields,
 	pub rangeproof: Option<RangeProof>,
 }
 
-impl Readable for Payload {
-    fn read<R: Reader>(reader: &mut R) -> Result<Payload> {
-        let version = reader.read_u8()?;
-        if version != CURRENT_VERSION {
-            return Err(ErrorKind::UnsupportedPayload.into());
+impl Payload {
+	pub fn deserialize(bytes: &Vec<u8>) -> Result<Payload> {
+		let payload: Payload = ser::deserialize_default(&mut &bytes[..])?;
+		Ok(payload)
 	}
 
-        let excess = SecretKey::read(reader)?;
+	#[cfg(test)]
+	pub fn serialize(&self) -> Result<Vec<u8>> {
+		let mut vec = vec![];
+		ser::serialize_default(&mut vec, &self)?;
+		Ok(vec)
+	}
+}
+
+impl Readable for Payload {
+	fn read<R: Reader>(reader: &mut R) -> StdResult<Payload, ser::Error> {
+		let version = reader.read_u8()?;
+		if version != CURRENT_VERSION {
+			return Err(ser::Error::UnsupportedProtocolVersion);
+		}
+
+		let excess = secp::read_secret_key(reader)?;
+		let fee = FeeFields::try_from(reader.read_u64()?).map_err(|_| ser::Error::CorruptedData)?;
 		let rangeproof = if reader.read_u8()? == 0 {
 			None
 		} else {
@@ -32,135 +44,28 @@ impl Readable for Payload {
 		};
 
 		let payload = Payload {
-            excess: excess,
-            rangeproof: rangeproof
+			excess,
+			fee,
+			rangeproof,
 		};
 		Ok(payload)
 	}
 }
 
 impl Writeable for Payload {
-    fn write<W: Writer>(&self, writer: &mut W) -> Result<()> {
+	fn write<W: Writer>(&self, writer: &mut W) -> StdResult<(), ser::Error> {
 		writer.write_u8(CURRENT_VERSION)?;
 		writer.write_fixed_bytes(&self.excess)?;
+		writer.write_u64(self.fee.into())?;
 
 		match &self.rangeproof {
 			Some(proof) => {
 				writer.write_u8(1)?;
 				proof.write(writer)?;
-            },
+			}
 			None => writer.write_u8(0)?,
 		};
 
 		Ok(())
 	}
 }
-
-pub fn serialize_payload(payload: &Payload) -> Result<Vec<u8>> {
-    ser::ser_vec(&payload)
-}
-
-pub fn deserialize_payload(bytes: &Vec<u8>) -> Result<Payload> {
-    let mut cursor = Cursor::new(&bytes);
-    let mut reader = BinReader::new(&mut cursor);
-    Payload::read(&mut reader)
-}
-
-pub struct Hop {
-    pub pubkey: PublicKey,
-    pub payload: Payload,
-}
-
-pub struct Onion {
-    pub ephemeral_pubkey: PublicKey,
-    pub commit: Commitment,
-    pub enc_payloads: Vec<RawBytes>,
-}
-
-impl serde::ser::Serialize for Onion {
-    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
-    where
-        S: serde::ser::Serializer,
-    {
-        let mut state = serializer.serialize_struct("Onion", 3)?;
-
-        let secp = Secp256k1::new();
-        state.serialize_field("pubkey", &self.ephemeral_pubkey.serialize_vec(&secp, true).to_hex())?;
-        state.serialize_field("commit", &self.commit.to_hex())?;
-
-        let hex_payloads: Vec<String> = self.enc_payloads.iter().map(|v| v.to_hex()).collect();
-        state.serialize_field("data", &hex_payloads)?;
-        state.end()
-    }
-}
-
-impl<'de> serde::de::Deserialize<'de> for Onion {
-    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
-    where
-        D: serde::de::Deserializer<'de>,
-    {
-        #[derive(Deserialize)]
-        #[serde(field_identifier, rename_all = "snake_case")]
-        enum Field {
-            Pubkey,
-            Commit,
-            Data
-        }
-
-        struct OnionVisitor;
-
-        impl<'de> serde::de::Visitor<'de> for OnionVisitor {
-            type Value = Onion;
-
-            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
-                formatter.write_str("an Onion")
-            }
-
-            fn visit_map<A>(self, mut map: A) -> std::result::Result<Self::Value, A::Error>
-            where
-                A: serde::de::MapAccess<'de>,
-            {
-                let mut pubkey = None;
-                let mut commit = None;
-                let mut data = None;
-
-                while let Some(key) = map.next_key()? {
-                    match key {
-                        Field::Pubkey => {
-                            let val: String = map.next_value()?;
-                            let vec = grin_util::from_hex(&val).map_err(serde::de::Error::custom)?;
-                            let secp = Secp256k1::new();
-                            pubkey = Some(PublicKey::from_slice(&secp, &vec[..]).map_err(serde::de::Error::custom)?);
-                        }
-                        Field::Commit => {
-                            let val: String = map.next_value()?;
-                            let vec = grin_util::from_hex(&val).map_err(serde::de::Error::custom)?;
-                            commit = Some(Commitment::from_vec(vec));
-                        }
-                        Field::Data => {
-                            let val: Vec<String> = map.next_value()?;
-                            let mut vec: Vec<Vec<u8>> = Vec::new();
-                            for hex in val {
-                                vec.push(grin_util::from_hex(&hex).map_err(serde::de::Error::custom)?);
-                            }
-                            data = Some(vec);
-                        }
-                    }
-                }
-
-                Ok(Onion {
-                    ephemeral_pubkey: pubkey.unwrap(),
-                    commit: commit.unwrap(),
-                    enc_payloads: data.unwrap(),
-                })
-            }
-        }
-
-        const FIELDS: &[&str] = &[
-            "pubkey",
-            "commit",
-            "data"
-        ];
-        deserializer.deserialize_struct("Onion", &FIELDS, OnionVisitor)
-    }
-}

src/wallet.rs

@@ -0,0 +1,265 @@
+use crate::error::{ErrorKind, Result};
+use crate::secp;
+
+use grin_api::client;
+use grin_api::json_rpc::{build_request, Request, Response};
+use grin_core::core::{
+	FeeFields, Input, Inputs, KernelFeatures, Output, Transaction, TransactionBody, TxKernel,
+};
+use grin_core::libtx::secp_ser;
+use grin_keychain::BlindingFactor;
+use grin_util::{ToHex, ZeroingString};
+use grin_wallet_api::{EncryptedRequest, EncryptedResponse, JsonId, Token};
+use secp256k1zkp::{ContextFlag, PublicKey, Secp256k1, SecretKey};
+use serde::{Deserialize, Serialize};
+use serde_json::json;
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+pub trait Wallet: Send + Sync {
+	/// Builds an output for the wallet with the provided amount.
+	fn build_output(&self, amount: u64) -> Result<(BlindingFactor, Output)>;
+}
+
+/// Builds and verifies a 'Transaction' using the provided components.
+pub fn assemble_tx(
+	wallet: &Arc<dyn Wallet>,
+	inputs: &Vec<Input>,
+	outputs: &Vec<Output>,
+	fee_base: u64,
+	total_fee: u64,
+	excesses: &Vec<SecretKey>,
+) -> Result<Transaction> {
+	let secp = Secp256k1::with_caps(ContextFlag::Commit);
+	let txn_inputs = Inputs::from(inputs.as_slice());
+	let mut txn_outputs = outputs.clone();
+	let mut txn_excesses = excesses.clone();
+	let mut kernel_fee = total_fee;
+
+	// calculate fee required if we add our own output
+	let fee_required =
+		TransactionBody::weight_by_iok(inputs.len() as u64, (outputs.len() + 1) as u64, 1)
+			* fee_base;
+
+	// calculate fee to spend the output to ensure there's enough leftover to cover the fees for spending it
+	let fee_to_spend = TransactionBody::weight_by_iok(1, 0, 0) * fee_base;
+
+	// collect any leftover fees
+	if total_fee > fee_required + fee_to_spend {
+		let amount = total_fee - fee_required;
+		kernel_fee -= amount;
+
+		let wallet_output = wallet.build_output(amount)?;
+		txn_outputs.push(wallet_output.1);
+
+		let output_excess = wallet_output
+			.0
+			.secret_key(&secp)
+			.map_err(|_| ErrorKind::CorruptedData)?;
+		txn_excesses.push(output_excess);
+	}
+
+	// generate random transaction offset
+	let offset = secp::random_secret();
+
+	// calculate kernel excess
+	let kern_excess = secp.blind_sum(txn_excesses, vec![offset.clone()])?;
+
+	// build and verify kernel
+	let mut kernel = TxKernel::with_features(KernelFeatures::Plain {
+		fee: FeeFields::new(0, kernel_fee).unwrap(),
+	});
+	let msg = kernel.msg_to_sign()?;
+	kernel.excess = secp::commit(0, &kern_excess)?;
+	kernel.excess_sig = secp::sign(&kern_excess, &msg)?;
+	kernel.verify()?;
+
+	// assemble the transaction
+	let tx = Transaction::new(txn_inputs, &txn_outputs, &[kernel])
+		.with_offset(BlindingFactor::from_secret_key(offset));
+	Ok(tx)
+}
+
+/// HTTP (JSONRPC) implementation of the 'Wallet' trait.
+#[derive(Clone)]
+pub struct HttpWallet {
+	wallet_owner_url: SocketAddr,
+	wallet_owner_secret: Option<String>,
+	shared_key: SecretKey,
+	token: Token,
+}
+
+const ENDPOINT: &str = "/v3/owner";
+
+/// Wrapper for ECDH Public keys
+#[derive(Serialize, Deserialize, Debug, Clone)]
+#[serde(transparent)]
+pub struct ECDHPubkey {
+	/// public key, flattened
+	#[serde(with = "secp_ser::pubkey_serde")]
+	pub ecdh_pubkey: PublicKey,
+}
+
+impl HttpWallet {
+	/// Calls the 'open_wallet' using the RPC API.
+	pub fn open_wallet(
+		wallet_owner_url: &SocketAddr,
+		wallet_owner_secret: &Option<String>,
+		wallet_pass: &ZeroingString,
+	) -> Result<HttpWallet> {
+		println!("Opening wallet at {}", wallet_owner_url);
+		let shared_key = HttpWallet::init_secure_api(&wallet_owner_url, &wallet_owner_secret)?;
+
+		let open_wallet_params = json!({
+			"name": null,
+			"password": wallet_pass.to_string()
+		});
+		let token: Token = HttpWallet::send_enc_request(
+			&wallet_owner_url,
+			&wallet_owner_secret,
+			"open_wallet",
+			&open_wallet_params,
+			&shared_key,
+		)?;
+		println!("Connected to wallet");
+
+		Ok(HttpWallet {
+			wallet_owner_url: wallet_owner_url.clone(),
+			wallet_owner_secret: wallet_owner_secret.clone(),
+			shared_key: shared_key.clone(),
+			token: token.clone(),
+		})
+	}
+
+	fn init_secure_api(
+		wallet_owner_url: &SocketAddr,
+		wallet_owner_secret: &Option<String>,
+	) -> Result<SecretKey> {
+		let secp = Secp256k1::new();
+		let ephemeral_sk = secp::random_secret();
+		let ephemeral_pk = PublicKey::from_secret_key(&secp, &ephemeral_sk)?;
+		let init_params = json!({
+			"ecdh_pubkey": ephemeral_pk.serialize_vec(&secp, true).to_hex()
+		});
+
+		let response_pk: ECDHPubkey = HttpWallet::send_json_request(
+			&wallet_owner_url,
+			&wallet_owner_secret,
+			"init_secure_api",
+			&init_params,
+		)?;
+
+		let shared_key = {
+			let mut shared_pubkey = response_pk.ecdh_pubkey.clone();
+			shared_pubkey.mul_assign(&secp, &ephemeral_sk)?;
+
+			let x_coord = shared_pubkey.serialize_vec(&secp, true);
+			SecretKey::from_slice(&secp, &x_coord[1..])?
+		};
+
+		Ok(shared_key)
+	}
+
+	fn send_enc_request<D: serde::de::DeserializeOwned>(
+		wallet_owner_url: &SocketAddr,
+		wallet_owner_secret: &Option<String>,
+		method: &str,
+		params: &serde_json::Value,
+		shared_key: &SecretKey,
+	) -> Result<D> {
+		let url = format!("http://{}{}", wallet_owner_url, ENDPOINT);
+		let req = json!({
+			"method": method,
+			"params": params,
+			"id": JsonId::IntId(1),
+			"jsonrpc": "2.0",
+		});
+		let enc_req = EncryptedRequest::from_json(&JsonId::IntId(1), &req, &shared_key)?;
+		let res = client::post::<EncryptedRequest, EncryptedResponse>(
+			url.as_str(),
+			wallet_owner_secret.clone(),
+			&enc_req,
+		)?;
+		let decrypted = res.decrypt(&shared_key)?;
+		let response: Response = serde_json::from_value(decrypted.clone())?;
+		let parsed = serde_json::from_value(response.result.unwrap().get("Ok").unwrap().clone())?;
+		Ok(parsed)
+	}
+
+	fn send_json_request<D: serde::de::DeserializeOwned>(
+		wallet_owner_url: &SocketAddr,
+		wallet_owner_secret: &Option<String>,
+		method: &str,
+		params: &serde_json::Value,
+	) -> Result<D> {
+		let url = format!("http://{}{}", wallet_owner_url, ENDPOINT);
+		let req = build_request(method, params);
+		let res =
+			client::post::<Request, Response>(url.as_str(), wallet_owner_secret.clone(), &req)?;
+		let parsed = res.clone().into_result()?;
+		Ok(parsed)
+	}
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct OutputWithBlind {
+	#[serde(
+		serialize_with = "secp_ser::as_hex",
+		deserialize_with = "secp_ser::blind_from_hex"
+	)]
+	blind: BlindingFactor,
+	output: Output,
+}
+
+impl Wallet for HttpWallet {
+	/// Builds an 'Output' for the wallet using the 'build_output' RPC API.
+	fn build_output(&self, amount: u64) -> Result<(BlindingFactor, Output)> {
+		let req_json = json!({
+			"token": self.token.keychain_mask.clone().unwrap().0,
+			"features": "Plain",
+			"amount":  amount
+		});
+		let output: OutputWithBlind = HttpWallet::send_enc_request(
+			&self.wallet_owner_url,
+			&self.wallet_owner_secret,
+			"build_output",
+			&req_json,
+			&self.shared_key,
+		)?;
+		Ok((output.blind, output.output))
+	}
+}
+
+#[cfg(test)]
+pub mod mock {
+	use super::Wallet;
+	use crate::error::Result;
+	use crate::secp;
+
+	use grin_core::core::{Output, OutputFeatures};
+	use grin_keychain::BlindingFactor;
+	use secp256k1zkp::Secp256k1;
+
+	/// HTTP (JSONRPC) implementation of the 'Wallet' trait.
+	#[derive(Clone)]
+	pub struct MockWallet {}
+
+	impl Wallet for MockWallet {
+		/// Builds an 'Output' for the wallet using the 'build_output' RPC API.
+		fn build_output(&self, amount: u64) -> Result<(BlindingFactor, Output)> {
+			let secp = Secp256k1::new();
+			let blind = secp::random_secret();
+			let commit = secp::commit(amount, &blind)?;
+			let proof = secp.bullet_proof(
+				amount,
+				blind.clone(),
+				secp::random_secret(),
+				secp::random_secret(),
+				None,
+				None,
+			);
+			let output = Output::new(OutputFeatures::Plain, commit.clone(), proof);
+			Ok((BlindingFactor::from_secret_key(blind), output))
+		}
+	}
+}