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unbuffered-client.rs
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unbuffered-client.rs
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//! This is a simple client using rustls' unbuffered API. Meaning that the application layer must
//! handle the buffers required to receive, process and send TLS data.
use std::error::Error;
use std::io::{Read, Write};
use std::net::TcpStream;
use std::sync::Arc;
use rustls::client::{ClientConnectionData, EarlyDataError, UnbufferedClientConnection};
use rustls::unbuffered::{
AppDataRecord, ConnectionState, EncodeError, EncryptError, InsufficientSizeError,
UnbufferedStatus, WriteTraffic,
};
#[allow(unused_imports)]
use rustls::version::{TLS12, TLS13};
use rustls::{ClientConfig, RootCertStore};
fn main() -> Result<(), Box<dyn Error>> {
let root_store = RootCertStore {
roots: webpki_roots::TLS_SERVER_ROOTS.into(),
};
let mut config = ClientConfig::builder_with_protocol_versions(&[&TLS13])
.with_root_certificates(root_store)
.with_no_client_auth();
config.enable_early_data = SEND_EARLY_DATA;
let config = Arc::new(config);
let mut incoming_tls = [0; INCOMING_TLS_BUFSIZE];
let mut outgoing_tls = vec![0; OUTGOING_TLS_INITIAL_BUFSIZE];
converse(&config, false, &mut incoming_tls, &mut outgoing_tls)?;
if SEND_EARLY_DATA {
eprintln!("---- second connection ----");
converse(&config, true, &mut incoming_tls, &mut outgoing_tls)?;
}
Ok(())
}
fn converse(
config: &Arc<ClientConfig>,
send_early_data: bool,
incoming_tls: &mut [u8],
outgoing_tls: &mut Vec<u8>,
) -> Result<(), Box<dyn Error>> {
let mut conn = UnbufferedClientConnection::new(Arc::clone(config), SERVER_NAME.try_into()?)?;
let mut sock = TcpStream::connect(format!("{SERVER_NAME}:{PORT}"))?;
let mut incoming_used = 0;
let mut outgoing_used = 0;
let mut open_connection = true;
let mut sent_request = false;
let mut received_response = false;
let mut sent_early_data = false;
let mut iter_count = 0;
while open_connection {
let UnbufferedStatus { mut discard, state } =
conn.process_tls_records(&mut incoming_tls[..incoming_used]);
match dbg!(state.unwrap()) {
ConnectionState::ReadTraffic(mut state) => {
while let Some(res) = state.next_record() {
let AppDataRecord {
discard: new_discard,
payload,
} = res?;
discard += new_discard;
if payload.starts_with(b"HTTP") {
let response = core::str::from_utf8(payload)?;
let header = response
.lines()
.next()
.unwrap_or(response);
println!("{header}");
} else {
println!("(.. continued HTTP response ..)");
}
received_response = true;
}
}
ConnectionState::EncodeTlsData(mut state) => {
try_or_resize_and_retry(
|out_buffer| state.encode(out_buffer),
|e| {
if let EncodeError::InsufficientSize(is) = &e {
Ok(*is)
} else {
Err(e.into())
}
},
outgoing_tls,
&mut outgoing_used,
)?;
}
ConnectionState::TransmitTlsData(mut state) => {
if let Some(mut may_encrypt_early_data) = state.may_encrypt_early_data() {
let written = try_or_resize_and_retry(
|out_buffer| may_encrypt_early_data.encrypt(EARLY_DATA, out_buffer),
|e| match &e {
EarlyDataError::Encrypt(EncryptError::InsufficientSize(is)) => Ok(*is),
_ => Err(e.into()),
},
outgoing_tls,
&mut outgoing_used,
)?;
eprintln!("queued {written}B of early data");
sent_early_data = true;
}
if let Some(mut may_encrypt) = state.may_encrypt_app_data() {
encrypt_http_request(
&mut sent_request,
&mut may_encrypt,
outgoing_tls,
&mut outgoing_used,
);
}
send_tls(&mut sock, outgoing_tls, &mut outgoing_used)?;
state.done();
}
ConnectionState::BlockedHandshake { .. } => {
recv_tls(&mut sock, incoming_tls, &mut incoming_used)?;
}
ConnectionState::WriteTraffic(mut may_encrypt) => {
if encrypt_http_request(
&mut sent_request,
&mut may_encrypt,
outgoing_tls,
&mut outgoing_used,
) {
send_tls(&mut sock, outgoing_tls, &mut outgoing_used)?;
recv_tls(&mut sock, incoming_tls, &mut incoming_used)?;
} else if !received_response {
// this happens in the TLS 1.3 case. the app-data was sent in the preceding
// `TransmitTlsData` state. the server should have already written a
// response which we can read out from the socket
recv_tls(&mut sock, incoming_tls, &mut incoming_used)?;
} else {
try_or_resize_and_retry(
|out_buffer| may_encrypt.queue_close_notify(out_buffer),
|e| {
if let EncryptError::InsufficientSize(is) = &e {
Ok(*is)
} else {
Err(e.into())
}
},
outgoing_tls,
&mut outgoing_used,
)?;
send_tls(&mut sock, outgoing_tls, &mut outgoing_used)?;
open_connection = false;
}
}
ConnectionState::Closed => {
open_connection = false;
}
// other states are not expected in this example
_ => unreachable!(),
}
if discard != 0 {
assert!(discard <= incoming_used);
incoming_tls.copy_within(discard..incoming_used, 0);
incoming_used -= discard;
eprintln!("discarded {discard}B from `incoming_tls`");
}
iter_count += 1;
assert!(
iter_count < MAX_ITERATIONS,
"did not get a HTTP response within {MAX_ITERATIONS} iterations"
);
}
assert!(sent_request);
assert!(received_response);
assert_eq!(send_early_data, sent_early_data);
assert_eq!(0, incoming_used);
assert_eq!(0, outgoing_used);
Ok(())
}
fn try_or_resize_and_retry<E>(
mut f: impl FnMut(&mut [u8]) -> Result<usize, E>,
map_err: impl FnOnce(E) -> Result<InsufficientSizeError, Box<dyn Error>>,
outgoing_tls: &mut Vec<u8>,
outgoing_used: &mut usize,
) -> Result<usize, Box<dyn Error>>
where
E: Error + 'static,
{
let written = match f(&mut outgoing_tls[*outgoing_used..]) {
Ok(written) => written,
Err(e) => {
let InsufficientSizeError { required_size } = map_err(e)?;
let new_len = *outgoing_used + required_size;
outgoing_tls.resize(new_len, 0);
eprintln!("resized `outgoing_tls` buffer to {new_len}B");
f(&mut outgoing_tls[*outgoing_used..])?
}
};
*outgoing_used += written;
Ok(written)
}
fn recv_tls(
sock: &mut TcpStream,
incoming_tls: &mut [u8],
incoming_used: &mut usize,
) -> Result<(), Box<dyn Error>> {
let read = sock.read(&mut incoming_tls[*incoming_used..])?;
eprintln!("received {read}B of data");
*incoming_used += read;
Ok(())
}
fn send_tls(
sock: &mut TcpStream,
outgoing_tls: &[u8],
outgoing_used: &mut usize,
) -> Result<(), Box<dyn Error>> {
sock.write_all(&outgoing_tls[..*outgoing_used])?;
eprintln!("sent {outgoing_used}B of data");
*outgoing_used = 0;
Ok(())
}
fn encrypt_http_request(
sent_request: &mut bool,
may_encrypt: &mut WriteTraffic<'_, ClientConnectionData>,
outgoing_tls: &mut [u8],
outgoing_used: &mut usize,
) -> bool {
if !*sent_request {
let request = format!("GET / HTTP/1.1\r\nHost: {SERVER_NAME}\r\nConnection: close\r\nAccept-Encoding: identity\r\n\r\n").into_bytes();
let written = may_encrypt
.encrypt(&request, &mut outgoing_tls[*outgoing_used..])
.expect("encrypted request does not fit in `outgoing_tls`");
*outgoing_used += written;
*sent_request = true;
eprintln!("queued HTTP request");
true
} else {
false
}
}
const SERVER_NAME: &str = "example.com";
const PORT: u16 = 443;
const KB: usize = 1024;
const INCOMING_TLS_BUFSIZE: usize = 16 * KB;
const OUTGOING_TLS_INITIAL_BUFSIZE: usize = KB;
const MAX_ITERATIONS: usize = 20;
const SEND_EARLY_DATA: bool = false;
const EARLY_DATA: &[u8] = b"hello";