Harden native auth and SDK datagram handling
This commit is contained in:
DuProcess
+120
-6
@@ -13,6 +13,7 @@ use crate::transport::{
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DoshTransport, SessionEvent, SessionRole, SessionTransportConfig, TransportConfig,
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service_name_from_target,
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};
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use crate::udp::is_transient_udp_send_error;
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use anyhow::{Context, Result, anyhow, bail};
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use ed25519_dalek::SigningKey;
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use std::collections::{HashMap, HashSet};
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@@ -97,6 +98,7 @@ pub enum DoshServerEvent {
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Ignored,
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}
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#[derive(Debug, Clone)]
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struct PendingServerAuth {
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client: native::NativeClientHello,
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server: NativeServerHello,
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@@ -255,7 +257,7 @@ impl DoshServer {
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};
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let body = protocol::to_body(&NativeServerHelloBody { hello })?;
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let out = protocol::encode_plain(PacketKind::NativeServerHello, pending_id, 1, 0, &body)?;
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self.socket.send_to(&out, peer).await?;
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let _ = send_udp(&self.socket, &out, peer).await?;
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Ok(())
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}
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@@ -327,7 +329,7 @@ impl DoshServer {
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peer: SocketAddr,
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packet: &protocol::Packet,
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) -> Result<DoshServerEvent> {
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let Some(pending) = self.pending.remove(&packet.header.conn_id) else {
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let Some(pending) = self.pending.get(&packet.header.conn_id).cloned() else {
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self.send_reject(peer, packet.header.conn_id, "unknown native auth")
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.await?;
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return Ok(DoshServerEvent::Ignored);
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@@ -338,13 +340,28 @@ impl DoshServer {
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return Ok(DoshServerEvent::Ignored);
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}
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if pending.created_at.elapsed() > self.config.auth_timeout {
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self.pending.remove(&packet.header.conn_id);
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self.send_reject(peer, packet.header.conn_id, "native auth expired")
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.await?;
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return Ok(DoshServerEvent::Ignored);
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}
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let body = protocol::decrypt_body(packet, &pending.session_key, CLIENT_TO_SERVER)?;
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let req: NativeUserAuthBody = protocol::from_body(&body)?;
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let body = match protocol::decrypt_body(packet, &pending.session_key, CLIENT_TO_SERVER) {
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Ok(body) => body,
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Err(_) => {
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self.send_reject(peer, packet.header.conn_id, "native auth decrypt failed")
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.await?;
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return Ok(DoshServerEvent::Ignored);
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}
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};
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let req: NativeUserAuthBody = match protocol::from_body(&body) {
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Ok(req) => req,
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Err(_) => {
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self.send_reject(peer, packet.header.conn_id, "invalid native auth body")
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.await?;
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return Ok(DoshServerEvent::Ignored);
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}
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};
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let services = match self.verify_auth_and_services(&pending, &req.auth) {
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Ok(services) => services,
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Err(err) => {
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@@ -353,6 +370,7 @@ impl DoshServer {
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return Ok(DoshServerEvent::Ignored);
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}
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};
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self.pending.remove(&packet.header.conn_id);
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let conn_id = crypto::random_16();
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let key_id = protocol::session_key_id(&pending.session_key);
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@@ -381,7 +399,7 @@ impl DoshServer {
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SERVER_TO_CLIENT,
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&body,
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)?;
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self.socket.send_to(&out, peer).await?;
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let _ = send_udp(&self.socket, &out, peer).await?;
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let transport = DoshTransport::new(
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Arc::clone(&self.socket),
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@@ -428,7 +446,7 @@ impl DoshServer {
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reason: reason.to_string(),
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})?;
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let out = protocol::encode_plain(PacketKind::AttachReject, conn_id, 0, 0, &body)?;
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self.socket.send_to(&out, peer).await?;
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let _ = send_udp(&self.socket, &out, peer).await?;
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Ok(())
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}
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@@ -439,6 +457,14 @@ impl DoshServer {
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}
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}
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async fn send_udp(socket: &UdpSocket, packet: &[u8], peer: SocketAddr) -> Result<bool> {
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match socket.send_to(packet, peer).await {
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Ok(_) => Ok(true),
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Err(err) if is_transient_udp_send_error(&err) => Ok(false),
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Err(err) => Err(err).with_context(|| format!("send UDP packet to {peer}")),
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}
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}
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fn validate_requested_services(
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allowed_services: &HashSet<String>,
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requests: &[ForwardingRequest],
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@@ -477,6 +503,7 @@ mod tests {
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use super::*;
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use crate::client::DoshClient;
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use crate::config::{ClientConfig, HostsConfig};
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use crate::protocol::{CLIENT_TO_SERVER, NativeUserAuthBody};
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use crate::transport::TransportEvent;
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use ed25519_dalek::SigningKey;
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@@ -588,4 +615,91 @@ mod tests {
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}
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}
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}
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#[tokio::test]
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async fn bad_native_auth_does_not_consume_pending_challenge() {
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let dir = tempfile::tempdir().unwrap();
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let host_key = dir.path().join("host_key");
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let authorized_keys = dir.path().join("authorized_keys");
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let signing = SigningKey::from_bytes(&[93u8; 32]);
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let keypair = ssh_key::private::Ed25519Keypair::from(&signing);
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let private =
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ssh_key::PrivateKey::new(ssh_key::private::KeypairData::from(keypair), "").unwrap();
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std::fs::write(
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&authorized_keys,
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format!("{}\n", private.public_key().to_openssh().unwrap()),
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)
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.unwrap();
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let server_config = ServerConfig {
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host_key: host_key.to_string_lossy().to_string(),
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authorized_keys: vec![authorized_keys.to_string_lossy().to_string()],
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..ServerConfig::default()
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};
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let server_config = DoshServerConfig::new(server_config)
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.bind_addr("127.0.0.1:0".parse().unwrap())
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.require_current_user(false);
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let mut server = DoshServer::bind(server_config).await.unwrap();
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let peer: SocketAddr = "127.0.0.1:9".parse().unwrap();
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let (client_secret, client_public) = native::generate_native_ephemeral();
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let hello = native::NativeClientHello {
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protocol_version: native::NATIVE_PROTOCOL_VERSION,
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client_random: crypto::random_32(),
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client_ephemeral_public: client_public,
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requested_host: "127.0.0.1".to_string(),
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requested_user: "sdk-user".to_string(),
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requested_session: "test".to_string(),
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requested_mode: "forward-only".to_string(),
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terminal_size: (80, 24),
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supported_aead: vec!["chacha20poly1305".to_string()],
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supported_user_key_algorithms: vec!["ssh-ed25519".to_string()],
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cached_host_key_fingerprint: None,
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attach_ticket_envelope: None,
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requested_env: Vec::new(),
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};
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let (pending_id, server_hello) = server.build_server_hello(hello.clone(), peer).unwrap();
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let session_key = native::derive_native_session_key(
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&client_secret,
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server_hello.server_ephemeral_public,
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&hello,
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&server_hello,
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)
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.unwrap();
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let auth = native::sign_user_auth(&signing, &hello, &server_hello, Vec::new()).unwrap();
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let body = protocol::to_body(&NativeUserAuthBody { auth }).unwrap();
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let bad = protocol::encode_encrypted(
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PacketKind::NativeUserAuth,
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pending_id,
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2,
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1,
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&[7u8; 32],
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CLIENT_TO_SERVER,
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&body,
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)
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.unwrap();
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let bad = protocol::decode(&bad).unwrap();
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assert!(matches!(
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server.handle_user_auth(peer, &bad).await.unwrap(),
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DoshServerEvent::Ignored
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));
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assert!(server.pending.contains_key(&pending_id));
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let valid = protocol::encode_encrypted(
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PacketKind::NativeUserAuth,
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pending_id,
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2,
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1,
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&session_key,
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CLIENT_TO_SERVER,
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&body,
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)
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.unwrap();
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let valid = protocol::decode(&valid).unwrap();
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assert!(matches!(
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server.handle_user_auth(peer, &valid).await.unwrap(),
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DoshServerEvent::Accepted(_)
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));
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assert!(!server.pending.contains_key(&pending_id));
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}
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}
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