1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
#![doc(html_root_url = "https://docs.rs/tokio-native-tls/0.3.0")]
#![warn(
    missing_debug_implementations,
    missing_docs,
    rust_2018_idioms,
    unreachable_pub
)]
#![deny(broken_intra_doc_links)]
#![doc(test(
    no_crate_inject,
    attr(deny(warnings, rust_2018_idioms), allow(dead_code, unused_variables))
))]

//! Async TLS streams
//!
//! This library is an implementation of TLS streams using the most appropriate
//! system library by default for negotiating the connection. That is, on
//! Windows this library uses SChannel, on OSX it uses SecureTransport, and on
//! other platforms it uses OpenSSL.
//!
//! Each TLS stream implements the `Read` and `Write` traits to interact and
//! interoperate with the rest of the futures I/O ecosystem. Client connections
//! initiated from this crate verify hostnames automatically and by default.
//!
//! This crate primarily exports this ability through two newtypes,
//! `TlsConnector` and `TlsAcceptor`. These newtypes augment the
//! functionality provided by the `native-tls` crate, on which this crate is
//! built. Configuration of TLS parameters is still primarily done through the
//! `native-tls` crate.

use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};

use crate::native_tls::{Error, HandshakeError, MidHandshakeTlsStream};
use std::fmt;
use std::future::Future;
use std::io::{self, Read, Write};
use std::marker::Unpin;
use std::pin::Pin;
use std::ptr::null_mut;
use std::task::{Context, Poll};

/// An intermediate wrapper for the inner stream `S`.
#[derive(Debug)]
pub struct AllowStd<S> {
    inner: S,
    context: *mut (),
}

impl<S> AllowStd<S> {
    /// Returns a shared reference to the inner stream.
    pub fn get_ref(&self) -> &S {
        &self.inner
    }

    /// Returns a mutable reference to the inner stream.
    pub fn get_mut(&mut self) -> &mut S {
        &mut self.inner
    }
}

/// A wrapper around an underlying raw stream which implements the TLS or SSL
/// protocol.
///
/// A `TlsStream<S>` represents a handshake that has been completed successfully
/// and both the server and the client are ready for receiving and sending
/// data. Bytes read from a `TlsStream` are decrypted from `S` and bytes written
/// to a `TlsStream` are encrypted when passing through to `S`.
#[derive(Debug)]
pub struct TlsStream<S>(native_tls::TlsStream<AllowStd<S>>);

/// A wrapper around a `native_tls::TlsConnector`, providing an async `connect`
/// method.
#[derive(Clone)]
pub struct TlsConnector(native_tls::TlsConnector);

/// A wrapper around a `native_tls::TlsAcceptor`, providing an async `accept`
/// method.
#[derive(Clone)]
pub struct TlsAcceptor(native_tls::TlsAcceptor);

struct MidHandshake<S>(Option<MidHandshakeTlsStream<AllowStd<S>>>);

enum StartedHandshake<S> {
    Done(TlsStream<S>),
    Mid(MidHandshakeTlsStream<AllowStd<S>>),
}

struct StartedHandshakeFuture<F, S>(Option<StartedHandshakeFutureInner<F, S>>);
struct StartedHandshakeFutureInner<F, S> {
    f: F,
    stream: S,
}

struct Guard<'a, S>(&'a mut TlsStream<S>)
where
    AllowStd<S>: Read + Write;

impl<S> Drop for Guard<'_, S>
where
    AllowStd<S>: Read + Write,
{
    fn drop(&mut self) {
        (self.0).0.get_mut().context = null_mut();
    }
}

// *mut () context is neither Send nor Sync
unsafe impl<S: Send> Send for AllowStd<S> {}
unsafe impl<S: Sync> Sync for AllowStd<S> {}

impl<S> AllowStd<S>
where
    S: Unpin,
{
    fn with_context<F, R>(&mut self, f: F) -> io::Result<R>
    where
        F: FnOnce(&mut Context<'_>, Pin<&mut S>) -> Poll<io::Result<R>>,
    {
        unsafe {
            assert!(!self.context.is_null());
            let waker = &mut *(self.context as *mut _);
            match f(waker, Pin::new(&mut self.inner)) {
                Poll::Ready(r) => r,
                Poll::Pending => Err(io::Error::from(io::ErrorKind::WouldBlock)),
            }
        }
    }
}

impl<S> Read for AllowStd<S>
where
    S: AsyncRead + Unpin,
{
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        let mut buf = ReadBuf::new(buf);
        self.with_context(|ctx, stream| stream.poll_read(ctx, &mut buf))?;
        Ok(buf.filled().len())
    }
}

impl<S> Write for AllowStd<S>
where
    S: AsyncWrite + Unpin,
{
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.with_context(|ctx, stream| stream.poll_write(ctx, buf))
    }

    fn flush(&mut self) -> io::Result<()> {
        self.with_context(|ctx, stream| stream.poll_flush(ctx))
    }
}

impl<S> TlsStream<S> {
    fn with_context<F, R>(&mut self, ctx: &mut Context<'_>, f: F) -> Poll<io::Result<R>>
    where
        F: FnOnce(&mut native_tls::TlsStream<AllowStd<S>>) -> io::Result<R>,
        AllowStd<S>: Read + Write,
    {
        self.0.get_mut().context = ctx as *mut _ as *mut ();
        let g = Guard(self);
        match f(&mut (g.0).0) {
            Ok(v) => Poll::Ready(Ok(v)),
            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => Poll::Pending,
            Err(e) => Poll::Ready(Err(e)),
        }
    }

    /// Returns a shared reference to the inner stream.
    pub fn get_ref(&self) -> &native_tls::TlsStream<AllowStd<S>>
    where
        S: AsyncRead + AsyncWrite + Unpin,
    {
        &self.0
    }

    /// Returns a mutable reference to the inner stream.
    pub fn get_mut(&mut self) -> &mut native_tls::TlsStream<AllowStd<S>>
    where
        S: AsyncRead + AsyncWrite + Unpin,
    {
        &mut self.0
    }
}

impl<S> AsyncRead for TlsStream<S>
where
    S: AsyncRead + AsyncWrite + Unpin,
{
    fn poll_read(
        mut self: Pin<&mut Self>,
        ctx: &mut Context<'_>,
        buf: &mut ReadBuf<'_>,
    ) -> Poll<io::Result<()>> {
        self.with_context(ctx, |s| {
            let n = s.read(buf.initialize_unfilled())?;
            buf.advance(n);
            Ok(())
        })
    }
}

impl<S> AsyncWrite for TlsStream<S>
where
    S: AsyncRead + AsyncWrite + Unpin,
{
    fn poll_write(
        mut self: Pin<&mut Self>,
        ctx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<io::Result<usize>> {
        self.with_context(ctx, |s| s.write(buf))
    }

    fn poll_flush(mut self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<io::Result<()>> {
        self.with_context(ctx, |s| s.flush())
    }

    fn poll_shutdown(mut self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<io::Result<()>> {
        self.with_context(ctx, |s| s.shutdown())
    }
}

async fn handshake<F, S>(f: F, stream: S) -> Result<TlsStream<S>, Error>
where
    F: FnOnce(
            AllowStd<S>,
        ) -> Result<native_tls::TlsStream<AllowStd<S>>, HandshakeError<AllowStd<S>>>
        + Unpin,
    S: AsyncRead + AsyncWrite + Unpin,
{
    let start = StartedHandshakeFuture(Some(StartedHandshakeFutureInner { f, stream }));

    match start.await {
        Err(e) => Err(e),
        Ok(StartedHandshake::Done(s)) => Ok(s),
        Ok(StartedHandshake::Mid(s)) => MidHandshake(Some(s)).await,
    }
}

impl<F, S> Future for StartedHandshakeFuture<F, S>
where
    F: FnOnce(
            AllowStd<S>,
        ) -> Result<native_tls::TlsStream<AllowStd<S>>, HandshakeError<AllowStd<S>>>
        + Unpin,
    S: Unpin,
    AllowStd<S>: Read + Write,
{
    type Output = Result<StartedHandshake<S>, Error>;

    fn poll(
        mut self: Pin<&mut Self>,
        ctx: &mut Context<'_>,
    ) -> Poll<Result<StartedHandshake<S>, Error>> {
        let inner = self.0.take().expect("future polled after completion");
        let stream = AllowStd {
            inner: inner.stream,
            context: ctx as *mut _ as *mut (),
        };

        match (inner.f)(stream) {
            Ok(mut s) => {
                s.get_mut().context = null_mut();
                Poll::Ready(Ok(StartedHandshake::Done(TlsStream(s))))
            }
            Err(HandshakeError::WouldBlock(mut s)) => {
                s.get_mut().context = null_mut();
                Poll::Ready(Ok(StartedHandshake::Mid(s)))
            }
            Err(HandshakeError::Failure(e)) => Poll::Ready(Err(e)),
        }
    }
}

impl TlsConnector {
    /// Connects the provided stream with this connector, assuming the provided
    /// domain.
    ///
    /// This function will internally call `TlsConnector::connect` to connect
    /// the stream and returns a future representing the resolution of the
    /// connection operation. The returned future will resolve to either
    /// `TlsStream<S>` or `Error` depending if it's successful or not.
    ///
    /// This is typically used for clients who have already established, for
    /// example, a TCP connection to a remote server. That stream is then
    /// provided here to perform the client half of a connection to a
    /// TLS-powered server.
    pub async fn connect<S>(&self, domain: &str, stream: S) -> Result<TlsStream<S>, Error>
    where
        S: AsyncRead + AsyncWrite + Unpin,
    {
        handshake(move |s| self.0.connect(domain, s), stream).await
    }
}

impl fmt::Debug for TlsConnector {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("TlsConnector").finish()
    }
}

impl From<native_tls::TlsConnector> for TlsConnector {
    fn from(inner: native_tls::TlsConnector) -> TlsConnector {
        TlsConnector(inner)
    }
}

impl TlsAcceptor {
    /// Accepts a new client connection with the provided stream.
    ///
    /// This function will internally call `TlsAcceptor::accept` to connect
    /// the stream and returns a future representing the resolution of the
    /// connection operation. The returned future will resolve to either
    /// `TlsStream<S>` or `Error` depending if it's successful or not.
    ///
    /// This is typically used after a new socket has been accepted from a
    /// `TcpListener`. That socket is then passed to this function to perform
    /// the server half of accepting a client connection.
    pub async fn accept<S>(&self, stream: S) -> Result<TlsStream<S>, Error>
    where
        S: AsyncRead + AsyncWrite + Unpin,
    {
        handshake(move |s| self.0.accept(s), stream).await
    }
}

impl fmt::Debug for TlsAcceptor {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("TlsAcceptor").finish()
    }
}

impl From<native_tls::TlsAcceptor> for TlsAcceptor {
    fn from(inner: native_tls::TlsAcceptor) -> TlsAcceptor {
        TlsAcceptor(inner)
    }
}

impl<S: AsyncRead + AsyncWrite + Unpin> Future for MidHandshake<S> {
    type Output = Result<TlsStream<S>, Error>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let mut_self = self.get_mut();
        let mut s = mut_self.0.take().expect("future polled after completion");

        s.get_mut().context = cx as *mut _ as *mut ();
        match s.handshake() {
            Ok(mut s) => {
                s.get_mut().context = null_mut();
                Poll::Ready(Ok(TlsStream(s)))
            }
            Err(HandshakeError::WouldBlock(mut s)) => {
                s.get_mut().context = null_mut();
                mut_self.0 = Some(s);
                Poll::Pending
            }
            Err(HandshakeError::Failure(e)) => Poll::Ready(Err(e)),
        }
    }
}

/// re-export native_tls
pub mod native_tls {
    pub use native_tls::*;
}