Limit the size of oracle responses (#3597)

## Motivation

Services can be called as oracles, and the responses they provide must
be bounded because they are stored in blocks.

## Proposal

Implement a configurable limit to the size of oracle responses, and
enforce that limit in contract HTTP requests and service-as-oracle
responses.

To distinguish between contracts and services in compile time, an
extension trait was used to allow minimal change to the `BaseRuntime`
implementation.

## Test Plan

Unit test cases were added to check if the limits were being respected.

## Release Plan

- These changes follow the usual release cycle, because
services-as-oracles is still feature gated by `unstable-oracles`.

## Links

- Closes #3563
- [reviewer
checklist](https://github.com/linera-io/linera-protocol/blob/main/CONTRIBUTING.md#reviewer-checklist)

---------

Signed-off-by: Janito Vaqueiro Ferreira Filho <[email protected]>
Co-authored-by: Andreas Fackler <[email protected]>

Author: jvff

CLI.md

@@ -476,6 +476,7 @@ View or update the resource control policy
 * `--maximum-block-proposal-size <MAXIMUM_BLOCK_PROPOSAL_SIZE>` — Set the maximum size of a block proposal, in bytes
 * `--maximum-bytes-read-per-block <MAXIMUM_BYTES_READ_PER_BLOCK>` — Set the maximum read data per block
 * `--maximum-bytes-written-per-block <MAXIMUM_BYTES_WRITTEN_PER_BLOCK>` — Set the maximum write data per block
+* `--maximum-oracle-response-bytes <MAXIMUM_ORACLE_RESPONSE_BYTES>` — Set the maximum size of oracle responses
 * `--maximum-http-response-bytes <MAXIMUM_HTTP_RESPONSE_BYTES>` — Set the maximum size in bytes of a received HTTP response
 * `--http-request-timeout-ms <HTTP_REQUEST_TIMEOUT_MS>` — Set the maximum amount of time allowed to wait for an HTTP response
 * `--http-request-allow-list <HTTP_REQUEST_ALLOW_LIST>` — Set the list of hosts that contracts and services can send HTTP requests to
@@ -535,6 +536,7 @@ Create genesis configuration for a Linera deployment. Create initial user chains
 * `--maximum-block-proposal-size <MAXIMUM_BLOCK_PROPOSAL_SIZE>` — Set the maximum size of a block proposal, in bytes. (This will overwrite value from `--policy-config`)
 * `--maximum-bytes-read-per-block <MAXIMUM_BYTES_READ_PER_BLOCK>` — Set the maximum read data per block. (This will overwrite value from `--policy-config`)
 * `--maximum-bytes-written-per-block <MAXIMUM_BYTES_WRITTEN_PER_BLOCK>` — Set the maximum write data per block. (This will overwrite value from `--policy-config`)
+* `--maximum-oracle-response-bytes <MAXIMUM_ORACLE_RESPONSE_BYTES>` — Set the maximum size of oracle responses. (This will overwrite value from `--policy-config`)
 * `--maximum-http-response-bytes <MAXIMUM_HTTP_RESPONSE_BYTES>` — Set the maximum size in bytes of a received HTTP response
 * `--http-request-timeout-ms <HTTP_REQUEST_TIMEOUT_MS>` — Set the maximum amount of time allowed to wait for an HTTP response
 * `--http-request-allow-list <HTTP_REQUEST_ALLOW_LIST>` — Set the list of hosts that contracts and services can send HTTP requests to

Cargo.lock

@@ -12,15 +12,23 @@ repository.workspace = true
 version.workspace = true
 
 [features]
-test = ["tokio/macros", "linera-base/test", "linera-execution/test"]
-metrics = ["prometheus", "linera-views/metrics", "linera-execution/metrics"]
-web = ["linera-base/web", "linera-views/web", "linera-execution/web"]
 benchmark = ["linera-base/test"]
+metrics = ["prometheus", "linera-views/metrics", "linera-execution/metrics"]
+test = [
+    "dep:anyhow",
+    "dep:axum",
+    "tokio/macros",
+    "linera-base/test",
+    "linera-execution/test",
+]
 unstable-oracles = ["linera-execution/unstable-oracles"]
+web = ["linera-base/web", "linera-views/web", "linera-execution/web"]
 
 [dependencies]
+anyhow = { workspace = true, optional = true }
 async-graphql.workspace = true
 async-trait.workspace = true
+axum = { workspace = true, optional = true }
 custom_debug_derive.workspace = true
 futures.workspace = true
 linera-base.workspace = true

examples/Cargo.lock

@@ -0,0 +1,57 @@
+// Copyright (c) Zefchain Labs, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+//! A simple HTTP server to use for testing.
+
+use std::{future::IntoFuture, net::Ipv4Addr};
+
+use axum::Router;
+use futures::FutureExt as _;
+use tokio::{net::TcpListener, sync::oneshot};
+
+/// A handle to a running HTTP server.
+///
+/// The server is gracefully shutdown when this handle is dropped.
+pub struct HttpServer {
+    port: u16,
+    _shutdown_sender: oneshot::Sender<()>,
+}
+
+impl HttpServer {
+    /// Spawns a task with an HTTP server serving the routes defined by the [`Router`].
+    ///
+    /// Returns an [`HttpServer`] handle to keep the server running in the background.
+    pub async fn start(router: Router) -> anyhow::Result<Self> {
+        let (shutdown_sender, shutdown_receiver) = oneshot::channel();
+        let shutdown_signal = shutdown_receiver.map(|_| ());
+
+        let listener = TcpListener::bind((Ipv4Addr::from([127, 0, 0, 1]), 0)).await?;
+        let port = listener.local_addr()?.port();
+
+        tokio::spawn(
+            axum::serve(listener, router)
+                .with_graceful_shutdown(shutdown_signal)
+                .into_future(),
+        );
+
+        Ok(HttpServer {
+            port,
+            _shutdown_sender: shutdown_sender,
+        })
+    }
+
+    /// Returns the URL string this HTTP server is listening on.
+    pub fn url(&self) -> String {
+        format!("http://{}:{}", self.hostname(), self.port())
+    }
+
+    /// Returns the hostname of this HTTP server.
+    pub fn hostname(&self) -> String {
+        "localhost".to_owned()
+    }
+
+    /// Returns the port this HTTP server is listening on.
+    pub fn port(&self) -> u16 {
+        self.port
+    }
+}

linera-chain/Cargo.toml

@@ -3,6 +3,8 @@
 
 //! Test utilities
 
+mod http_server;
+
 use linera_base::{
     crypto::{AccountPublicKey, AccountSecretKey},
     data_types::{Amount, BlockHeight, Round, Timestamp},
@@ -15,6 +17,7 @@ use linera_execution::{
     Message, MessageKind, Operation, ResourceControlPolicy, SystemOperation,
 };
 
+pub use self::http_server::HttpServer;
 use crate::{
     block::ConfirmedBlock,
     data_types::{