improving documentation and error handling

.gitignore

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

README.md

@@ -3,6 +3,20 @@ 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 --pass "server-password-here" init-config`.
+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.
+
+### 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 --pass "server-password-here" --wallet_pass "wallet-password-here"`
+
 ### SWAP API
 The first CoinSwap server (n<sub>1</sub>) provides the `swap` API, publicly available for use by GRIN wallets.
 

src/config.rs

@@ -14,22 +14,31 @@ use std::path::PathBuf;
 // 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,
+	/// owner api address of the grin wallet
 	pub wallet_owner_url: SocketAddr,
 }
 
-/// Encrypted server key, for storing on disk and decrypting with provided password
+/// 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,
-	pub salt: String,
-	pub nonce: 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,
@@ -104,13 +113,13 @@ impl EncryptedServerKey {
 /// The config attributes saved to disk
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
 struct RawConfig {
-	pub encrypted_key: String,
-	pub salt: String,
-	pub nonce: String,
-	pub interval_s: u32,
-	pub addr: SocketAddr,
-	pub grin_node_url: SocketAddr,
-	pub wallet_owner_url: SocketAddr,
+	encrypted_key: String,
+	salt: String,
+	nonce: String,
+	interval_s: u32,
+	addr: SocketAddr,
+	grin_node_url: SocketAddr,
+	wallet_owner_url: SocketAddr,
 }
 
 /// Writes the server config to the config_path given, encrypting the server_key first.

src/main.rs

@@ -6,6 +6,7 @@ use wallet::HttpWallet;
 use clap::App;
 use grin_util::{StopState, ZeroingString};
 use std::env;
+use std::io::{self, Write};
 use std::path::PathBuf;
 use std::sync::Arc;
 
@@ -26,7 +27,16 @@ mod wallet;
 
 const DEFAULT_INTERVAL: u32 = 12 * 60 * 60;
 
-fn main() -> std::result::Result<(), Box<dyn std::error::Error>> {
+fn main() {
+	if let Err(e) = real_main() {
+        io::stderr().write_all(format!("mwixnet server exited with error:\n{}\n", e).as_bytes()).unwrap();
+        std::process::exit(1);
+    }
+
+	std::process::exit(0);
+}
+
+fn real_main() -> std::result::Result<(), Box<dyn std::error::Error>> {
 	let yml = load_yaml!("../mwixnet.yml");
 	let args = App::from_yaml(yml).get_matches();
     
@@ -61,6 +71,7 @@ fn main() -> std::result::Result<(), Box<dyn std::error::Error>> {
         };
 
         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(());
     }