/__w/smoldot/smoldot/repo/light-base/src/json_rpc_service.rs

Source
// Smoldot
// Copyright (C) 2019-2022  Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

//! Background JSON-RPC service.
//!
//! # Usage
//!
//! Create a new JSON-RPC service by calling [`service()`].
//! Creating a JSON-RPC service spawns a background task (through [`PlatformRef::spawn_task`])
//! dedicated to processing JSON-RPC requests.
//!
//! In order to process a JSON-RPC request, call [`Frontend::queue_rpc_request`]. Later, the
//! JSON-RPC service can queue a response or, in the case of subscriptions, a notification. They
//! can be retrieved by calling [`Frontend::next_json_rpc_response`].
//!
//! In the situation where an attacker finds a JSON-RPC request that takes a long time to be
//! processed and continuously submits this same expensive request over and over again, the queue
//! of pending requests will start growing and use more and more memory. For this reason, if this
//! queue grows past [`Config::max_pending_requests`] items, [`Frontend::queue_rpc_request`]
//! will instead return an error.
//!

// TODO: doc
// TODO: re-review this once finished

mod background;

use crate::{
    log, network_service, platform::PlatformRef, runtime_service, sync_service,
    transactions_service,
};

use alloc::{
    borrow::Cow,
    boxed::Box,
    format,
    string::{String, ToString as _},
    sync::Arc,
};
use core::{num::NonZero, pin::Pin};
use futures_lite::StreamExt as _;

/// Configuration for [`service()`].
pub struct Config<TPlat: PlatformRef> {
    /// Access to the platform's capabilities.
    pub platform: TPlat,

    /// Name of the chain, for logging purposes.
    ///
    /// > **Note**: This name will be directly printed out. Any special character should already
    /// >           have been filtered out from this name.
    pub log_name: String,

    /// Maximum number of JSON-RPC requests that can be added to a queue if it is not ready to be
    /// processed immediately. Any additional request will be immediately rejected.
    ///
    /// This parameter is necessary in order to prevent users from using up too much memory within
    /// the client.
    // TODO: unused at the moment
    #[allow(unused)]
    pub max_pending_requests: NonZero<u32>,

    /// Maximum number of active subscriptions. Any additional subscription will be immediately
    /// rejected.
    ///
    /// This parameter is necessary in order to prevent users from using up too much memory within
    /// the client.
    // TODO: unused at the moment
    #[allow(unused)]
    pub max_subscriptions: u32,

    /// Access to the network, and identifier of the chain from the point of view of the network
    /// service.
    pub network_service: Arc<network_service::NetworkServiceChain<TPlat>>,

    /// Service responsible for synchronizing the chain.
    pub sync_service: Arc<sync_service::SyncService<TPlat>>,

    /// Service responsible for emitting transactions and tracking their state.
    pub transactions_service: Arc<transactions_service::TransactionsService<TPlat>>,

    /// Service that provides a ready-to-be-called runtime for the current best block.
    pub runtime_service: Arc<runtime_service::RuntimeService<TPlat>>,

    /// Name of the chain, as found in the chain specification.
    pub chain_name: String,
    /// Type of chain, as found in the chain specification.
    pub chain_ty: String,
    /// JSON-encoded properties of the chain, as found in the chain specification.
    pub chain_properties_json: String,
    /// Whether the chain is a live network. Found in the chain specification.
    pub chain_is_live: bool,

    /// Value to return when the `system_name` RPC is called. Should be set to the name of the
    /// final executable.
    pub system_name: String,

    /// Value to return when the `system_version` RPC is called. Should be set to the version of
    /// the final executable.
    pub system_version: String,

    /// Hash of the genesis block of the chain.
    pub genesis_block_hash: [u8; 32],
}

/// Creates a new JSON-RPC service with the given configuration.
///
/// Returns a handler that allows sending requests and receiving responses.
///
/// Destroying the [`Frontend`] automatically shuts down the service.
pub fn service<TPlat: PlatformRef>(config: Config<TPlat>) -> Frontend<TPlat> {
    let log_target = format!("json-rpc-{}", config.log_name);

    let (requests_tx, requests_rx) = async_channel::unbounded(); // TODO: capacity?
    let (responses_tx, responses_rx) = async_channel::bounded(16); // TODO: capacity?

    let frontend = Frontend {
        platform: config.platform.clone(),
        log_target: log_target.clone(),
        responses_rx: Arc::new(async_lock::Mutex::new(Box::pin(responses_rx))),
        requests_tx,
    };

    let platform = config.platform.clone();
    platform.spawn_task(
        Cow::Owned(log_target.clone()),
        background::run(
            log_target,
            background::Config {
                platform: config.platform,
                network_service: config.network_service,
                sync_service: config.sync_service,
                transactions_service: config.transactions_service,
                runtime_service: config.runtime_service,
                chain_name: config.chain_name,
                chain_ty: config.chain_ty,
                chain_properties_json: config.chain_properties_json,
                chain_is_live: config.chain_is_live,
                system_name: config.system_name,
                system_version: config.system_version,
                genesis_block_hash: config.genesis_block_hash,
            },
            requests_rx,
            responses_tx,
        ),
    );

    frontend
}

/// Handle that allows sending JSON-RPC requests on the service.
///
/// The [`Frontend`] can be cloned, in which case the clone will refer to the same JSON-RPC
/// service.
///
/// Destroying all the [`Frontend`]s automatically shuts down the associated service.
#[derive(Clone)]
pub struct Frontend<TPlat> {
    /// See [`Config::platform`].
    platform: TPlat,

    /// How to send requests to the background task.
    requests_tx: async_channel::Sender<String>,

    /// How to receive responses coming from the background task.
    // TODO: we use an Arc so that it's clonable, but that's questionnable
    responses_rx: Arc<async_lock::Mutex<Pin<Box<async_channel::Receiver<String>>>>>,

    /// Target to use when emitting logs.
    log_target: String,
}

impl<TPlat: PlatformRef> Frontend<TPlat> {
    /// Queues the given JSON-RPC request to be processed in the background.
    ///
    /// An error is returned if [`Config::max_pending_requests`] is exceeded, which can happen
    /// if the requests take a long time to process or if [`Frontend::next_json_rpc_response`]
    /// isn't called often enough.
    pub fn queue_rpc_request(&self, json_rpc_request: String) -> Result<(), HandleRpcError> {
        let log_friendly_request =
            crate::util::truncated_str(json_rpc_request.chars().filter(|c| !c.is_control()), 250)
                .to_string();

        match self.requests_tx.try_send(json_rpc_request) {
            Ok(()) => {
                log!(
                    &self.platform,
                    Debug,
                    &self.log_target,
                    "json-rpc-request-queued",
                    request = log_friendly_request
                );
                Ok(())
            }
            Err(err) => Err(HandleRpcError::TooManyPendingRequests {
                json_rpc_request: err.into_inner(),
            }),
        }
    }

    /// Waits until a JSON-RPC response has been generated, then returns it.
    ///
    /// If this function is called multiple times in parallel, the order in which the calls are
    /// responded to is unspecified.
    pub async fn next_json_rpc_response(&self) -> String {
        let message = match self.responses_rx.lock().await.next().await {
            Some(m) => m,
            None => unreachable!(),
        };

        log!(
            &self.platform,
            Debug,
            &self.log_target,
            "json-rpc-response-yielded",
            response =
                crate::util::truncated_str(message.chars().filter(|c| !c.is_control()), 250,)
        );

        message
    }
}

/// Error potentially returned when queuing a JSON-RPC request.
#[derive(Debug, derive_more::Display, derive_more::Error)]
pub enum HandleRpcError {
    /// The JSON-RPC service cannot process this request, as too many requests are already being
    /// processed.
    #[display(
        "The JSON-RPC service cannot process this request, as too many requests are already being processed."
    )]
    TooManyPendingRequests {
        /// Request that was being queued.
        json_rpc_request: String,
    },
}

Coverage Report

Created: 2025-07-01 09:16

Line	Count	Source
1		// Smoldot
2		// Copyright (C) 2019-2022 Parity Technologies (UK) Ltd.
3		// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
4
5		// This program is free software: you can redistribute it and/or modify
6		// it under the terms of the GNU General Public License as published by
7		// the Free Software Foundation, either version 3 of the License, or
8		// (at your option) any later version.
9
10		// This program is distributed in the hope that it will be useful,
11		// but WITHOUT ANY WARRANTY; without even the implied warranty of
12		// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13		// GNU General Public License for more details.
14
15		// You should have received a copy of the GNU General Public License
16		// along with this program. If not, see <http://www.gnu.org/licenses/>.
17
18		//! Background JSON-RPC service.
19		//!
20		//! # Usage
21		//!
22		//! Create a new JSON-RPC service by calling [`service()`].
23		//! Creating a JSON-RPC service spawns a background task (through [`PlatformRef::spawn_task`])
24		//! dedicated to processing JSON-RPC requests.
25		//!
26		//! In order to process a JSON-RPC request, call [`Frontend::queue_rpc_request`]. Later, the
27		//! JSON-RPC service can queue a response or, in the case of subscriptions, a notification. They
28		//! can be retrieved by calling [`Frontend::next_json_rpc_response`].
29		//!
30		//! In the situation where an attacker finds a JSON-RPC request that takes a long time to be
31		//! processed and continuously submits this same expensive request over and over again, the queue
32		//! of pending requests will start growing and use more and more memory. For this reason, if this
33		//! queue grows past [`Config::max_pending_requests`] items, [`Frontend::queue_rpc_request`]
34		//! will instead return an error.
35		//!
36
37		// TODO: doc
38		// TODO: re-review this once finished
39
40		mod background;
41
42		use crate::{
43		log, network_service, platform::PlatformRef, runtime_service, sync_service,
44		transactions_service,
45		};
46
47		use alloc::{
48		borrow::Cow,
49		boxed::Box,
50		format,
51		string::{String, ToString as _},
52		sync::Arc,
53		};
54		use core::{num::NonZero, pin::Pin};
55		use futures_lite::StreamExt as _;
56
57		/// Configuration for [`service()`].
58		pub struct Config<TPlat: PlatformRef> {
59		/// Access to the platform's capabilities.
60		pub platform: TPlat,
61
62		/// Name of the chain, for logging purposes.
63		///
64		/// > Note: This name will be directly printed out. Any special character should already
65		/// > have been filtered out from this name.
66		pub log_name: String,
67
68		/// Maximum number of JSON-RPC requests that can be added to a queue if it is not ready to be
69		/// processed immediately. Any additional request will be immediately rejected.
70		///
71		/// This parameter is necessary in order to prevent users from using up too much memory within
72		/// the client.
73		// TODO: unused at the moment
74		#[allow(unused)]
75		pub max_pending_requests: NonZero<u32>,
76
77		/// Maximum number of active subscriptions. Any additional subscription will be immediately
78		/// rejected.
79		///
80		/// This parameter is necessary in order to prevent users from using up too much memory within
81		/// the client.
82		// TODO: unused at the moment
83		#[allow(unused)]
84		pub max_subscriptions: u32,
85
86		/// Access to the network, and identifier of the chain from the point of view of the network
87		/// service.
88		pub network_service: Arc<network_service::NetworkServiceChain<TPlat>>,
89
90		/// Service responsible for synchronizing the chain.
91		pub sync_service: Arc<sync_service::SyncService<TPlat>>,
92
93		/// Service responsible for emitting transactions and tracking their state.
94		pub transactions_service: Arc<transactions_service::TransactionsService<TPlat>>,
95
96		/// Service that provides a ready-to-be-called runtime for the current best block.
97		pub runtime_service: Arc<runtime_service::RuntimeService<TPlat>>,
98
99		/// Name of the chain, as found in the chain specification.
100		pub chain_name: String,
101		/// Type of chain, as found in the chain specification.
102		pub chain_ty: String,
103		/// JSON-encoded properties of the chain, as found in the chain specification.
104		pub chain_properties_json: String,
105		/// Whether the chain is a live network. Found in the chain specification.
106		pub chain_is_live: bool,
107
108		/// Value to return when the `system_name` RPC is called. Should be set to the name of the
109		/// final executable.
110		pub system_name: String,
111
112		/// Value to return when the `system_version` RPC is called. Should be set to the version of
113		/// the final executable.
114		pub system_version: String,
115
116		/// Hash of the genesis block of the chain.
117		pub genesis_block_hash: [u8; 32],
118		}
119
120		/// Creates a new JSON-RPC service with the given configuration.
121		///
122		/// Returns a handler that allows sending requests and receiving responses.
123		///
124		/// Destroying the [`Frontend`] automatically shuts down the service.
125	0	pub fn service<TPlat: PlatformRef>(config: Config<TPlat>) -> Frontend<TPlat> {
126	0	let log_target = format!("json-rpc-{}", config.log_name);
127
128	0	let (requests_tx, requests_rx) = async_channel::unbounded(); // TODO: capacity?
129	0	let (responses_tx, responses_rx) = async_channel::bounded(16); // TODO: capacity?
130
131	0	let frontend = Frontend {
132	0	platform: config.platform.clone(),
133	0	log_target: log_target.clone(),
134	0	responses_rx: Arc::new(async_lock::Mutex::new(Box::pin(responses_rx))),
135	0	requests_tx,
136	0	};
137
138	0	let platform = config.platform.clone();
139	0	platform.spawn_task(
140	0	Cow::Owned(log_target.clone()),
141	0	background::run(
142	0	log_target,
143	0	background::Config {
144	0	platform: config.platform,
145	0	network_service: config.network_service,
146	0	sync_service: config.sync_service,
147	0	transactions_service: config.transactions_service,
148	0	runtime_service: config.runtime_service,
149	0	chain_name: config.chain_name,
150	0	chain_ty: config.chain_ty,
151	0	chain_properties_json: config.chain_properties_json,
152	0	chain_is_live: config.chain_is_live,
153	0	system_name: config.system_name,
154	0	system_version: config.system_version,
155	0	genesis_block_hash: config.genesis_block_hash,
156	0	},
157	0	requests_rx,
158	0	responses_tx,
159		),
160		);
161
162	0	frontend
163	0	} Unexecuted instantiation: _RINvNtCsgnEOxJmACC4_13smoldot_light16json_rpc_service7servicepEB4_ Unexecuted instantiation: _RINvNtCs508CmrSPkZh_13smoldot_light16json_rpc_service7serviceNtNtCs7snhGEhbuap_18smoldot_light_wasm8platform11PlatformRefEB11_ Unexecuted instantiation: _RINvNtCs508CmrSPkZh_13smoldot_light16json_rpc_service7servicepEB4_
164
165		/// Handle that allows sending JSON-RPC requests on the service.
166		///
167		/// The [`Frontend`] can be cloned, in which case the clone will refer to the same JSON-RPC
168		/// service.
169		///
170		/// Destroying all the [`Frontend`]s automatically shuts down the associated service.
171		#[derive(Clone)]
172		pub struct Frontend<TPlat> {
173		/// See [`Config::platform`].
174		platform: TPlat,
175
176		/// How to send requests to the background task.
177		requests_tx: async_channel::Sender<String>,
178
179		/// How to receive responses coming from the background task.
180		// TODO: we use an Arc so that it's clonable, but that's questionnable
181		responses_rx: Arc<async_lock::Mutex<Pin<Box<async_channel::Receiver<String>>>>>,
182
183		/// Target to use when emitting logs.
184		log_target: String,
185		}
186
187		impl<TPlat: PlatformRef> Frontend<TPlat> {
188		/// Queues the given JSON-RPC request to be processed in the background.
189		///
190		/// An error is returned if [`Config::max_pending_requests`] is exceeded, which can happen
191		/// if the requests take a long time to process or if [`Frontend::next_json_rpc_response`]
192		/// isn't called often enough.
193	0	pub fn queue_rpc_request(&self, json_rpc_request: String) -> Result<(), HandleRpcError> {
194	0	let log_friendly_request =
195	0	crate::util::truncated_str(json_rpc_request.chars().filter(\|c\| !c.is_control()), 250) Unexecuted instantiation: _RNCNvMNtCsgnEOxJmACC4_13smoldot_light16json_rpc_serviceINtB4_8FrontendpE17queue_rpc_request0B6_ Unexecuted instantiation: _RNCNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB4_8FrontendNtNtCs7snhGEhbuap_18smoldot_light_wasm8platform11PlatformRefE17queue_rpc_request0B1a_ Unexecuted instantiation: _RNCNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB4_8FrontendpE17queue_rpc_request0B6_
196	0	.to_string();
197
198	0	match self.requests_tx.try_send(json_rpc_request) {
199		Ok(()) => {
200	0	log!(
201	0	&self.platform,
202		Debug,
203	0	&self.log_target,
204		"json-rpc-request-queued",
205		request = log_friendly_request
206		);
207	0	Ok(())
208		}
209	0	Err(err) => Err(HandleRpcError::TooManyPendingRequests {
210	0	json_rpc_request: err.into_inner(),
211	0	}),
212		}
213	0	} Unexecuted instantiation: _RNvMNtCsgnEOxJmACC4_13smoldot_light16json_rpc_serviceINtB2_8FrontendpE17queue_rpc_requestB4_ Unexecuted instantiation: _RNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB2_8FrontendNtNtCs7snhGEhbuap_18smoldot_light_wasm8platform11PlatformRefE17queue_rpc_requestB18_ Unexecuted instantiation: _RNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB2_8FrontendpE17queue_rpc_requestB4_
214
215		/// Waits until a JSON-RPC response has been generated, then returns it.
216		///
217		/// If this function is called multiple times in parallel, the order in which the calls are
218		/// responded to is unspecified.
219	0	pub async fn next_json_rpc_response(&self) -> String { Unexecuted instantiation: _RNvMNtCsgnEOxJmACC4_13smoldot_light16json_rpc_serviceINtB2_8FrontendpE22next_json_rpc_responseB4_ Unexecuted instantiation: _RNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB2_8FrontendNtNtCs7snhGEhbuap_18smoldot_light_wasm8platform11PlatformRefE22next_json_rpc_responseB18_ Unexecuted instantiation: _RNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB2_8FrontendpE22next_json_rpc_responseB4_
220	0	let message = match self.responses_rx.lock().await.next().await {
221	0	Some(m) => m,
222	0	None => unreachable!(),
223		};
224
225	0	log!(
226	0	&self.platform,
227		Debug,
228	0	&self.log_target,
229		"json-rpc-response-yielded",
230		response =
231	0	crate::util::truncated_str(message.chars().filter(\|c\| !c.is_control()), 250,) Unexecuted instantiation: _RNCNCNvMNtCsgnEOxJmACC4_13smoldot_light16json_rpc_serviceINtB6_8FrontendpE22next_json_rpc_response00B8_ Unexecuted instantiation: _RNCNCNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB6_8FrontendNtNtCs7snhGEhbuap_18smoldot_light_wasm8platform11PlatformRefE22next_json_rpc_response00B1c_ Unexecuted instantiation: _RNCNCNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB6_8FrontendpE22next_json_rpc_response00B8_
232		);
233
234	0	message
235	0	} Unexecuted instantiation: _RNCNvMNtCsgnEOxJmACC4_13smoldot_light16json_rpc_serviceINtB4_8FrontendpE22next_json_rpc_response0B6_ Unexecuted instantiation: _RNCNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB4_8FrontendNtNtCs7snhGEhbuap_18smoldot_light_wasm8platform11PlatformRefE22next_json_rpc_response0B1a_ Unexecuted instantiation: _RNCNvMNtCs508CmrSPkZh_13smoldot_light16json_rpc_serviceINtB4_8FrontendpE22next_json_rpc_response0B6_
236		}
237
238		/// Error potentially returned when queuing a JSON-RPC request.
239		#[derive(Debug, derive_more::Display, derive_more::Error)]
240		pub enum HandleRpcError {
241		/// The JSON-RPC service cannot process this request, as too many requests are already being
242		/// processed.
243		#[display(
244		"The JSON-RPC service cannot process this request, as too many requests are already being processed."
245		)]
246		TooManyPendingRequests {
247		/// Request that was being queued.
248		json_rpc_request: String,
249		},
250		}