feature(rpc): add an rpc server to Zebra

zebra-rpc/Cargo.toml

@@ -8,3 +8,19 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+
+futures = "0.3"
+
+# lightwalletd sends JSON-RPC requests over HTTP 1.1
+hyper = { version = "0.14.17", features = ["http1", "server"] }
+
+jsonrpc-core = "18.0.0"
+jsonrpc-derive = "18.0.0"
+jsonrpc-http-server = "18.0.0"
+
+tokio = { version = "1.16.1", features = ["time", "rt-multi-thread", "macros", "tracing"] }
+
+tracing = "0.1"
+tracing-futures = "0.2"
+
+serde = { version = "1", features = ["serde_derive"] }

zebra-rpc/src/config.rs

@@ -0,0 +1,30 @@
+//! User-configurable RPC settings.
+
+use std::net::SocketAddr;
+
+use serde::{Deserialize, Serialize};
+
+/// RPC configuration section.
+#[derive(Clone, Debug, Default, Deserialize, Serialize)]
+#[serde(deny_unknown_fields, default)]
+pub struct Config {
+    /// IP address and port for the RPC server.
+    ///
+    /// Note: The RPC server is disabled by default.
+    /// To enable the RPC server, set a listen address in the config:
+    /// ```toml
+    /// [rpc]
+    /// listen_addr = '127.0.0.1:8232'
+    /// ```
+    ///
+    /// The recommended ports for the RPC server are:
+    /// - Mainnet: 127.0.0.1:8232
+    /// - Testnet: 127.0.0.1:18232
+    ///
+    /// # Security
+    ///
+    /// If you bind Zebra's RPC port to a public IP address,
+    /// anyone on the internet can send transactions via your node.
+    /// They can also query your node's state.
+    pub listen_addr: Option<SocketAddr>,
+}

zebra-rpc/src/lib.rs

@@ -1,5 +1,9 @@
-//! A Zebra remote procedure call interface
+//! A Zebra Remote Procedure Call (RPC) interface
 
 #![doc(html_favicon_url = "https://www.zfnd.org/images/zebra-favicon-128.png")]
 #![doc(html_logo_url = "https://www.zfnd.org/images/zebra-icon.png")]
 #![doc(html_root_url = "https://doc.zebra.zfnd.org/zebra_rpc")]
+
+pub mod config;
+pub mod methods;
+pub mod server;

zebra-rpc/src/methods.rs

@@ -0,0 +1,69 @@
+//! Zebra supported RPC methods.
+//!
+//! Based on the [`zcashd` RPC methods](https://zcash.github.io/rpc/)
+//! as used by `lightwalletd.`
+//!
+//! Some parts of the `zcashd` RPC documentation are outdated.
+//! So this implementation follows the `lightwalletd` client implementation.
+
+use jsonrpc_core::{self, Result};
+use jsonrpc_derive::rpc;
+
+#[rpc(server)]
+/// RPC method signatures.
+pub trait Rpc {
+    /// getinfo
+    ///
+    /// TODO: explain what the method does
+    ///       link to the zcashd RPC reference
+    ///       list the arguments and fields that lightwalletd uses
+    ///       note any other lightwalletd changes
+    #[rpc(name = "getinfo")]
+    fn get_info(&self) -> Result<GetInfo>;
+
+    /// getblockchaininfo
+    ///
+    /// TODO: explain what the method does
+    ///       link to the zcashd RPC reference
+    ///       list the arguments and fields that lightwalletd uses
+    ///       note any other lightwalletd changes
+    #[rpc(name = "getblockchaininfo")]
+    fn get_blockchain_info(&self) -> Result<GetBlockChainInfo>;
+}
+
+/// RPC method implementations.
+pub struct RpcImpl;
+impl Rpc for RpcImpl {
+    fn get_info(&self) -> Result<GetInfo> {
+        // TODO: dummy output data, fix in the context of #3142
+        let response = GetInfo {
+            build: "TODO: Zebra v1.0.0 ...".into(),
+            subversion: "TODO: /Zebra:1.0.0-beta.../".into(),
+        };
+
+        Ok(response)
+    }
+
+    fn get_blockchain_info(&self) -> Result<GetBlockChainInfo> {
+        // TODO: dummy output data, fix in the context of #3143
+        let response = GetBlockChainInfo {
+            chain: "TODO: main".to_string(),
+        };
+
+        Ok(response)
+    }
+}
+
+#[derive(serde::Serialize, serde::Deserialize)]
+/// Response to a `getinfo` RPC request.
+pub struct GetInfo {
+    build: String,
+    subversion: String,
+}
+
+#[derive(serde::Serialize, serde::Deserialize)]
+/// Response to a `getblockchaininfo` RPC request.
+pub struct GetBlockChainInfo {
+    chain: String,
+    // TODO: add other fields used by lightwalletd (#3143)
+}

zebra-rpc/src/server.rs

@@ -0,0 +1,63 @@
+//! A JSON-RPC 1.0 & 2.0 endpoint for Zebra.
+//!
+//! This endpoint is compatible with clients that incorrectly send
+//! `"jsonrpc" = 1.0` fields in JSON-RPC 1.0 requests,
+//! such as `lightwalletd`.
+
+use tracing::*;
+use tracing_futures::Instrument;
+
+use jsonrpc_core;
+use jsonrpc_http_server::ServerBuilder;
+
+use crate::{
+    config::Config,
+    methods::{Rpc, RpcImpl},
+    server::compatibility::FixHttpRequestMiddleware,
+};
+
+pub mod compatibility;
+
+/// Zebra RPC Server
+#[derive(Clone, Debug)]
+pub struct RpcServer;
+
+impl RpcServer {
+    /// Start a new RPC server endpoint
+    pub fn spawn(config: Config) -> tokio::task::JoinHandle<()> {
+        if let Some(listen_addr) = config.listen_addr {
+            info!("Trying to open RPC endpoint at {}...", listen_addr,);
+
+            // Create handler compatible with V1 and V2 RPC protocols
+            let mut io =
+                jsonrpc_core::IoHandler::with_compatibility(jsonrpc_core::Compatibility::Both);
+            io.extend_with(RpcImpl.to_delegate());
+
+            let server = ServerBuilder::new(io)
+                // use the same tokio executor as the rest of Zebra
+                .event_loop_executor(tokio::runtime::Handle::current())
+                .threads(1)
+                // TODO: disable this security check if we see errors from lightwalletd.
+                //.allowed_hosts(DomainsValidation::Disabled)
+                .request_middleware(FixHttpRequestMiddleware)
+                .start_http(&listen_addr)
+                .expect("Unable to start RPC server");
+
+            // The server is a blocking task, so we need to spawn it on a blocking thread.
+            let span = Span::current();
+            let server = move || {
+                span.in_scope(|| {
+                    info!("Opened RPC endpoint at {}", server.address());
+
+                    server.wait();
+
+                    info!("Stopping RPC endpoint");
+                })
+            };
+            tokio::task::spawn_blocking(server)
+        } else {
+            // There is no RPC port, so the RPC task does nothing.
+            tokio::task::spawn(futures::future::pending().in_current_span())
+        }
+    }
+}