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Copy pathsession.rs
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309 lines (278 loc) · 10.4 KB
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//! [`Session`] — the sans-I/O glue between a socket's byte stream and a response.
//!
//! A `Session` owns an HTTP protocol engine (HTTP/1.x, or HTTP/2 when the TLS
//! client negotiates `h2` via ALPN), an optional TLS transport, and the shared
//! [`Handler`]. Runtimes feed it the bytes that arrive on a socket and write
//! back the bytes it produces; the session decrypts, parses, invokes the
//! handler (with optional compression), serializes, and re-encrypts. It
//! performs no I/O itself.
use std::borrow::Cow;
use std::sync::Arc;
use crate::error::Result;
use crate::handler::Handler;
use crate::proto::{H1Conn, Limits, Request, Response};
#[cfg(feature = "compress")]
use crate::compress;
#[cfg(feature = "h2")]
use crate::h2::H2Conn;
/// The transport beneath the HTTP engine: either a plain byte passthrough or a
/// TLS layer.
enum Transport {
Plain,
#[cfg(feature = "tls")]
Tls(Box<crate::tls::TlsStream>),
}
impl Transport {
/// Turn received wire bytes into plaintext (decrypting under TLS). On a
/// plain connection the bytes are returned borrowed — no copy; the engine
/// copies them into its own input buffer.
fn decrypt<'a>(&mut self, wire_in: &'a [u8]) -> Result<Cow<'a, [u8]>> {
match self {
Transport::Plain => Ok(Cow::Borrowed(wire_in)),
#[cfg(feature = "tls")]
Transport::Tls(stream) => {
stream.feed(wire_in)?;
Ok(Cow::Owned(stream.recv_all()?))
}
}
}
/// Turn application bytes into wire bytes (encrypting under TLS, and
/// flushing any pending handshake records). Takes the buffer by value so a
/// plain connection can hand it straight back without copying.
fn encrypt(&mut self, app: Vec<u8>) -> Result<Vec<u8>> {
match self {
Transport::Plain => Ok(app),
#[cfg(feature = "tls")]
Transport::Tls(stream) => {
stream.send(&app)?;
stream.pop_all()
}
}
}
fn handshaking(&self) -> bool {
match self {
Transport::Plain => false,
#[cfg(feature = "tls")]
Transport::Tls(stream) => !stream.is_handshake_complete(),
}
}
#[allow(unused)]
fn alpn(&self) -> Option<Vec<u8>> {
match self {
Transport::Plain => None,
#[cfg(feature = "tls")]
Transport::Tls(stream) => stream.alpn_protocol(),
}
}
}
/// The chosen application protocol engine for a connection.
enum Engine {
H1(H1Conn),
#[cfg(feature = "h2")]
H2(Box<H2Conn>),
}
/// Shared, per-server settings a [`Session`] needs. Cheap to clone.
#[derive(Clone)]
pub struct SessionConfig {
/// The request handler, shared across all connections.
pub handler: Arc<dyn Handler>,
/// HTTP parsing limits.
pub limits: Limits,
/// `Server` header value (or `None` to omit).
pub server_name: Option<String>,
/// `Strict-Transport-Security` header value to send on **secure**
/// connections (e.g. `"max-age=31536000"`), or `None` to omit it. Never
/// sent over plain HTTP, where HSTS is meaningless.
pub hsts: Option<String>,
/// `Alt-Svc` header value advertising alternative services such as HTTP/3
/// (e.g. `r#"h3=":443"; ma=86400"#`), or `None` to omit it.
pub alt_svc: Option<String>,
/// Response compression options.
#[cfg(feature = "compress")]
pub compression: compress::Options,
}
impl SessionConfig {
/// Build a config around a handler, with default limits and compression.
pub fn new(handler: Arc<dyn Handler>) -> SessionConfig {
SessionConfig {
handler,
limits: Limits::default(),
server_name: Some(concat!("httpsd/", env!("CARGO_PKG_VERSION")).to_owned()),
hsts: None,
alt_svc: None,
#[cfg(feature = "compress")]
compression: compress::Options::default(),
}
}
}
/// A single HTTP(S) connection in progress.
pub struct Session {
/// `None` until the protocol is known (after the TLS handshake).
engine: Option<Engine>,
transport: Transport,
cfg: SessionConfig,
}
impl Session {
/// Create a plaintext (HTTP/1.x) session.
pub fn plain(cfg: SessionConfig) -> Session {
let engine = Engine::H1(Self::new_h1(&cfg));
Session {
engine: Some(engine),
transport: Transport::Plain,
cfg,
}
}
/// Create a TLS (HTTPS) session wrapping an accepted
/// [`TlsStream`](crate::tls::TlsStream). The protocol (HTTP/1.1 or HTTP/2)
/// is chosen once ALPN is known.
#[cfg(feature = "tls")]
pub fn tls(cfg: SessionConfig, stream: crate::tls::TlsStream) -> Session {
Session {
engine: None,
transport: Transport::Tls(Box::new(stream)),
cfg,
}
}
fn new_h1(cfg: &SessionConfig) -> H1Conn {
let mut conn = H1Conn::new(cfg.limits);
conn.set_server_name(cfg.server_name.clone());
conn
}
/// Feed bytes received from the socket: decrypt, (lazily) select the
/// protocol, parse requests, run the handler, and queue responses.
pub fn received(&mut self, wire_in: &[u8]) -> Result<()> {
let plaintext = self.transport.decrypt(wire_in)?;
// Choose the engine once the handshake exposes the ALPN protocol.
if self.engine.is_none() && !self.transport.handshaking() {
self.select_engine();
}
if plaintext.is_empty() || self.engine.is_none() {
return Ok(());
}
self.drive(plaintext.as_ref())
}
#[cfg(feature = "tls")]
fn select_engine(&mut self) {
#[cfg(feature = "h2")]
if self.transport.alpn().as_deref() == Some(b"h2") {
self.engine = Some(Engine::H2(Box::new(H2Conn::new(
self.cfg.limits,
self.cfg.server_name.clone(),
))));
return;
}
self.engine = Some(Engine::H1(Self::new_h1(&self.cfg)));
}
#[cfg(not(feature = "tls"))]
fn select_engine(&mut self) {
self.engine = Some(Engine::H1(Self::new_h1(&self.cfg)));
}
fn drive(&mut self, plaintext: &[u8]) -> Result<()> {
let secure = !matches!(self.transport, Transport::Plain);
match self.engine.as_mut().unwrap() {
Engine::H1(conn) => {
conn.feed(plaintext);
while let Ok(Some(req)) = conn.poll_request() {
let resp = Self::run_handler(&self.cfg, &req, secure);
conn.respond(resp);
}
}
#[cfg(feature = "h2")]
Engine::H2(conn) => {
conn.received(plaintext);
while let Some((sid, req)) = conn.poll_request() {
let resp = Self::run_handler(&self.cfg, &req, secure);
conn.respond(sid, resp);
}
}
}
Ok(())
}
/// Run the handler, apply response compression, and (on secure transports)
/// the HSTS header.
fn run_handler(cfg: &SessionConfig, req: &Request, secure: bool) -> Response {
let resp = cfg.handler.handle(req);
#[cfg(feature = "compress")]
let resp = compress::compress_response(req, resp, &cfg.compression);
apply_edge_headers(cfg, resp, secure)
}
/// Produce the bytes to write to the socket: TLS handshake records and/or
/// (encrypted) response data. May be empty.
pub fn to_send(&mut self) -> Result<Vec<u8>> {
let app = match self.engine.as_mut() {
Some(Engine::H1(conn)) => conn.take_out(),
#[cfg(feature = "h2")]
Some(Engine::H2(conn)) => conn.take_out(),
None => Vec::new(),
};
self.transport.encrypt(app)
}
/// Whether the engine still has output to produce — queued bytes or a
/// response body (e.g. a file) being streamed in chunks. Drivers must keep
/// calling [`to_send`](Self::to_send) while this is true before waiting for
/// the next read or closing, so a body is flushed in full.
pub fn has_output(&self) -> bool {
match self.engine.as_ref() {
Some(Engine::H1(conn)) => conn.has_output(),
#[cfg(feature = "h2")]
Some(Engine::H2(conn)) => conn.has_output(),
None => false,
}
}
/// Whether the connection should be closed once pending output is written.
pub fn wants_close(&self) -> bool {
match self.engine.as_ref() {
Some(Engine::H1(conn)) => conn.wants_close(),
#[cfg(feature = "h2")]
Some(Engine::H2(conn)) => conn.wants_close(),
None => false,
}
}
/// Whether the session is still completing the TLS handshake.
pub fn handshaking(&self) -> bool {
self.transport.handshaking()
}
}
/// Add the configured edge headers: `Strict-Transport-Security` (secure
/// connections only — clients ignore HSTS over plain HTTP) and `Alt-Svc`
/// (e.g. advertising HTTP/3). Shared with the HTTP/3 engine (always secure).
pub(crate) fn apply_edge_headers(
cfg: &SessionConfig,
mut resp: Response,
secure: bool,
) -> Response {
let h = resp.headers_mut();
if secure && let Some(value) = &cfg.hsts {
h.set_if_absent("Strict-Transport-Security", value.clone());
}
if let Some(value) = &cfg.alt_svc {
h.set_if_absent("Alt-Svc", value.clone());
}
resp
}
#[cfg(test)]
mod tests {
use super::*;
use crate::proto::StatusCode;
fn cfg() -> SessionConfig {
let mut c = SessionConfig::new(Arc::new(|_: &Request| Response::status(StatusCode::OK)));
c.hsts = Some("max-age=31536000".into());
c
}
#[test]
fn hsts_added_only_on_secure() {
let secure = apply_edge_headers(&cfg(), Response::status(StatusCode::OK), true);
assert_eq!(
secure.headers().get("strict-transport-security"),
Some("max-age=31536000")
);
let plain = apply_edge_headers(&cfg(), Response::status(StatusCode::OK), false);
assert!(plain.headers().get("strict-transport-security").is_none());
}
#[test]
fn hsts_absent_when_unset() {
let c = SessionConfig::new(Arc::new(|_: &Request| Response::status(StatusCode::OK)));
let r = apply_edge_headers(&c, Response::status(StatusCode::OK), true);
assert!(r.headers().get("strict-transport-security").is_none());
}
}
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