moq_native/

client.rs

use anyhow::Context;
use ring::digest::{digest, SHA256};
use rustls::pki_types::{CertificateDer, ServerName, UnixTime};
use rustls::RootCertStore;
use std::path::PathBuf;
use std::{fs, io, net, sync::Arc, time};
use url::Url;

use web_transport::quinn as web_transport_quinn;

#[derive(Clone, Default, Debug, clap::Args, serde::Serialize, serde::Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct ClientTls {
	/// Use the TLS root at this path, encoded as PEM.
	///
	/// This value can be provided multiple times for multiple roots.
	/// If this is empty, system roots will be used instead
	#[serde(skip_serializing_if = "Vec::is_empty")]
	#[arg(long = "tls-root")]
	pub root: Vec<PathBuf>,

	/// Danger: Disable TLS certificate verification.
	///
	/// Fine for local development and between relays, but should be used in caution in production.
	// This is an Option<bool> so clap skips over it when not provided, otherwise it is set to false.
	#[serde(skip_serializing_if = "Option::is_none")]
	#[arg(long = "tls-disable-verify")]
	pub disable_verify: Option<bool>,
}

#[derive(Clone, Debug, clap::Parser, serde::Serialize, serde::Deserialize)]
#[serde(deny_unknown_fields, default)]
pub struct ClientConfig {
	/// Listen for UDP packets on the given address.
	#[arg(long, id = "client-bind", default_value = "[::]:0")]
	pub bind: net::SocketAddr,

	#[command(flatten)]
	#[serde(default)]
	pub tls: ClientTls,
}

impl Default for ClientConfig {
	fn default() -> Self {
		Self {
			bind: "[::]:0".parse().unwrap(),
			tls: ClientTls::default(),
		}
	}
}

impl ClientConfig {
	pub fn init(self) -> anyhow::Result<Client> {
		Client::new(self)
	}
}

#[derive(Clone)]
pub struct Client {
	pub quic: quinn::Endpoint,
	pub tls: rustls::ClientConfig,
	pub transport: Arc<quinn::TransportConfig>,
}

impl Client {
	pub fn new(config: ClientConfig) -> anyhow::Result<Self> {
		let provider = Arc::new(rustls::crypto::aws_lc_rs::default_provider());

		// Create a list of acceptable root certificates.
		let mut roots = RootCertStore::empty();

		if config.tls.root.is_empty() {
			let native = rustls_native_certs::load_native_certs();

			// Log any errors that occurred while loading the native root certificates.
			for err in native.errors {
				tracing::warn!(?err, "failed to load root cert");
			}

			// Add the platform's native root certificates.
			for cert in native.certs {
				roots.add(cert).context("failed to add root cert")?;
			}
		} else {
			// Add the specified root certificates.
			for root in &config.tls.root {
				let root = fs::File::open(root).context("failed to open root cert file")?;
				let mut root = io::BufReader::new(root);

				let root = rustls_pemfile::certs(&mut root)
					.next()
					.context("no roots found")?
					.context("failed to read root cert")?;

				roots.add(root).context("failed to add root cert")?;
			}
		}

		// Create the TLS configuration we'll use as a client (relay -> relay)
		let mut tls = rustls::ClientConfig::builder_with_provider(provider.clone())
			.with_protocol_versions(&[&rustls::version::TLS13])?
			.with_root_certificates(roots)
			.with_no_client_auth();

		// Allow disabling TLS verification altogether.
		if config.tls.disable_verify.unwrap_or_default() {
			tracing::warn!("TLS server certificate verification is disabled; A man-in-the-middle attack is possible.");

			let noop = NoCertificateVerification(provider.clone());
			tls.dangerous().set_certificate_verifier(Arc::new(noop));
		}

		let socket = std::net::UdpSocket::bind(config.bind).context("failed to bind UDP socket")?;

		// Enable BBR congestion control
		// TODO validate the implementation
		let mut transport = quinn::TransportConfig::default();
		transport.max_idle_timeout(Some(time::Duration::from_secs(10).try_into().unwrap()));
		transport.keep_alive_interval(Some(time::Duration::from_secs(4)));
		transport.congestion_controller_factory(Arc::new(quinn::congestion::BbrConfig::default()));
		transport.mtu_discovery_config(None); // Disable MTU discovery
		let transport = Arc::new(transport);

		// There's a bit more boilerplate to make a generic endpoint.
		let runtime = quinn::default_runtime().context("no async runtime")?;
		let endpoint_config = quinn::EndpointConfig::default();

		// Create the generic QUIC endpoint.
		let quic =
			quinn::Endpoint::new(endpoint_config, None, socket, runtime).context("failed to create QUIC endpoint")?;

		Ok(Self { quic, tls, transport })
	}

	pub async fn connect(&self, mut url: Url) -> anyhow::Result<web_transport_quinn::Session> {
		let mut config = self.tls.clone();

		let host = url.host().context("invalid DNS name")?.to_string();
		let port = url.port().unwrap_or(443);

		// Look up the DNS entry.
		let ip = tokio::net::lookup_host((host.clone(), port))
			.await
			.context("failed DNS lookup")?
			.next()
			.context("no DNS entries")?;

		if url.scheme() == "http" {
			// Perform a HTTP request to fetch the certificate fingerprint.
			let mut fingerprint = url.clone();
			fingerprint.set_path("/certificate.sha256");

			tracing::warn!(url = %fingerprint, "performing insecure HTTP request for certificate");

			let resp = reqwest::get(fingerprint.as_str())
				.await
				.context("failed to fetch fingerprint")?
				.error_for_status()
				.context("fingerprint request failed")?;

			let fingerprint = resp.text().await.context("failed to read fingerprint")?;
			let fingerprint = hex::decode(fingerprint.trim()).context("invalid fingerprint")?;

			let verifier = FingerprintVerifier::new(config.crypto_provider().clone(), fingerprint);
			config.dangerous().set_certificate_verifier(Arc::new(verifier));

			url.set_scheme("https").expect("failed to set scheme");
		}

		let alpn = match url.scheme() {
			"https" => web_transport::quinn::ALPN,
			"moql" => moq_lite::ALPN,
			_ => anyhow::bail!("url scheme must be 'http', 'https', or 'moql'"),
		};

		// TODO support connecting to both ALPNs at the same time
		config.alpn_protocols = vec![alpn.as_bytes().to_vec()];
		config.key_log = Arc::new(rustls::KeyLogFile::new());

		let config: quinn::crypto::rustls::QuicClientConfig = config.try_into()?;
		let mut config = quinn::ClientConfig::new(Arc::new(config));
		config.transport_config(self.transport.clone());

		tracing::debug!(%url, %ip, %alpn, "connecting");

		let connection = self.quic.connect_with(config, ip, &host)?.await?;
		tracing::Span::current().record("id", connection.stable_id());

		let session = match url.scheme() {
			"https" => web_transport::quinn::Session::connect(connection, url).await?,
			moq_lite::ALPN => web_transport::quinn::Session::raw(connection, url),
			_ => unreachable!(),
		};

		Ok(session)
	}
}

#[derive(Debug)]
struct NoCertificateVerification(Arc<rustls::crypto::CryptoProvider>);

impl rustls::client::danger::ServerCertVerifier for NoCertificateVerification {
	fn verify_server_cert(
		&self,
		_end_entity: &CertificateDer<'_>,
		_intermediates: &[CertificateDer<'_>],
		_server_name: &ServerName<'_>,
		_ocsp: &[u8],
		_now: UnixTime,
	) -> Result<rustls::client::danger::ServerCertVerified, rustls::Error> {
		Ok(rustls::client::danger::ServerCertVerified::assertion())
	}

	fn verify_tls12_signature(
		&self,
		message: &[u8],
		cert: &CertificateDer<'_>,
		dss: &rustls::DigitallySignedStruct,
	) -> Result<rustls::client::danger::HandshakeSignatureValid, rustls::Error> {
		rustls::crypto::verify_tls12_signature(message, cert, dss, &self.0.signature_verification_algorithms)
	}

	fn verify_tls13_signature(
		&self,
		message: &[u8],
		cert: &CertificateDer<'_>,
		dss: &rustls::DigitallySignedStruct,
	) -> Result<rustls::client::danger::HandshakeSignatureValid, rustls::Error> {
		rustls::crypto::verify_tls13_signature(message, cert, dss, &self.0.signature_verification_algorithms)
	}

	fn supported_verify_schemes(&self) -> Vec<rustls::SignatureScheme> {
		self.0.signature_verification_algorithms.supported_schemes()
	}
}

// Verify the certificate matches a provided fingerprint.
#[derive(Debug)]
struct FingerprintVerifier {
	provider: Arc<rustls::crypto::CryptoProvider>,
	fingerprint: Vec<u8>,
}

impl FingerprintVerifier {
	pub fn new(provider: Arc<rustls::crypto::CryptoProvider>, fingerprint: Vec<u8>) -> Self {
		Self { provider, fingerprint }
	}
}

impl rustls::client::danger::ServerCertVerifier for FingerprintVerifier {
	fn verify_server_cert(
		&self,
		end_entity: &CertificateDer<'_>,
		_intermediates: &[CertificateDer<'_>],
		_server_name: &ServerName<'_>,
		_ocsp: &[u8],
		_now: UnixTime,
	) -> Result<rustls::client::danger::ServerCertVerified, rustls::Error> {
		let fingerprint = digest(&SHA256, end_entity);
		if fingerprint.as_ref() == self.fingerprint.as_slice() {
			Ok(rustls::client::danger::ServerCertVerified::assertion())
		} else {
			Err(rustls::Error::General("fingerprint mismatch".into()))
		}
	}

	fn verify_tls12_signature(
		&self,
		message: &[u8],
		cert: &CertificateDer<'_>,
		dss: &rustls::DigitallySignedStruct,
	) -> Result<rustls::client::danger::HandshakeSignatureValid, rustls::Error> {
		rustls::crypto::verify_tls12_signature(message, cert, dss, &self.provider.signature_verification_algorithms)
	}

	fn verify_tls13_signature(
		&self,
		message: &[u8],
		cert: &CertificateDer<'_>,
		dss: &rustls::DigitallySignedStruct,
	) -> Result<rustls::client::danger::HandshakeSignatureValid, rustls::Error> {
		rustls::crypto::verify_tls13_signature(message, cert, dss, &self.provider.signature_verification_algorithms)
	}

	fn supported_verify_schemes(&self) -> Vec<rustls::SignatureScheme> {
		self.provider.signature_verification_algorithms.supported_schemes()
	}
}