boring/ssl/
async_callbacks.rs

1use super::mut_only::MutOnly;
2use super::{
3    ClientHello, GetSessionPendingError, PrivateKeyMethod, PrivateKeyMethodError, SelectCertError,
4    Ssl, SslAlert, SslContextBuilder, SslRef, SslSession, SslSignatureAlgorithm, SslVerifyError,
5    SslVerifyMode,
6};
7use crate::ex_data::Index;
8use std::convert::identity;
9use std::future::Future;
10use std::pin::Pin;
11use std::sync::LazyLock;
12use std::task::{ready, Context, Poll, Waker};
13
14/// The type of futures to pass to [`SslContextBuilder::set_async_select_certificate_callback`].
15pub type BoxSelectCertFuture = ExDataFuture<Result<BoxSelectCertFinish, AsyncSelectCertError>>;
16
17/// The type of callbacks returned by [`BoxSelectCertFuture`] methods.
18pub type BoxSelectCertFinish = Box<dyn FnOnce(ClientHello<'_>) -> Result<(), AsyncSelectCertError>>;
19
20/// The type of futures returned by [`AsyncPrivateKeyMethod`] methods.
21pub type BoxPrivateKeyMethodFuture =
22    ExDataFuture<Result<BoxPrivateKeyMethodFinish, AsyncPrivateKeyMethodError>>;
23
24/// The type of callbacks returned by [`BoxPrivateKeyMethodFuture`].
25pub type BoxPrivateKeyMethodFinish =
26    Box<dyn FnOnce(&mut SslRef, &mut [u8]) -> Result<usize, AsyncPrivateKeyMethodError>>;
27
28/// The type of futures to pass to [`SslContextBuilder::set_async_get_session_callback`].
29pub type BoxGetSessionFuture = ExDataFuture<Option<BoxGetSessionFinish>>;
30
31/// The type of callbacks returned by [`BoxSelectCertFuture`] methods.
32pub type BoxGetSessionFinish = Box<dyn FnOnce(&mut SslRef, &[u8]) -> Option<SslSession>>;
33
34/// The type of futures to pass to [`SslContextBuilder::set_async_custom_verify_callback`].
35pub type BoxCustomVerifyFuture = ExDataFuture<Result<BoxCustomVerifyFinish, SslAlert>>;
36
37/// The type of callbacks returned by [`BoxCustomVerifyFuture`] methods.
38pub type BoxCustomVerifyFinish = Box<dyn FnOnce(&mut SslRef) -> Result<(), SslAlert>>;
39
40/// Convenience alias for futures stored in [`Ssl`] ex data by [`SslContextBuilder`] methods.
41///
42/// Public for documentation purposes.
43pub type ExDataFuture<T> = Pin<Box<dyn Future<Output = T> + Send>>;
44
45pub(crate) static TASK_WAKER_INDEX: LazyLock<Index<Ssl, Option<Waker>>> =
46    LazyLock::new(|| Ssl::new_ex_index().unwrap());
47pub(crate) static SELECT_CERT_FUTURE_INDEX: LazyLock<
48    Index<Ssl, MutOnly<Option<BoxSelectCertFuture>>>,
49> = LazyLock::new(|| Ssl::new_ex_index().unwrap());
50pub(crate) static SELECT_PRIVATE_KEY_METHOD_FUTURE_INDEX: LazyLock<
51    Index<Ssl, MutOnly<Option<BoxPrivateKeyMethodFuture>>>,
52> = LazyLock::new(|| Ssl::new_ex_index().unwrap());
53pub(crate) static SELECT_GET_SESSION_FUTURE_INDEX: LazyLock<
54    Index<Ssl, MutOnly<Option<BoxGetSessionFuture>>>,
55> = LazyLock::new(|| Ssl::new_ex_index().unwrap());
56pub(crate) static SELECT_CUSTOM_VERIFY_FUTURE_INDEX: LazyLock<
57    Index<Ssl, MutOnly<Option<BoxCustomVerifyFuture>>>,
58> = LazyLock::new(|| Ssl::new_ex_index().unwrap());
59
60impl SslContextBuilder {
61    /// Sets a callback that is called before most [`ClientHello`] processing
62    /// and before the decision whether to resume a session is made. The
63    /// callback may inspect the [`ClientHello`] and configure the connection.
64    ///
65    /// This method uses a function that returns a future whose output is
66    /// itself a closure that will be passed [`ClientHello`] to configure
67    /// the connection based on the computations done in the future.
68    ///
69    /// A task waker must be set on `Ssl` values associated with the resulting
70    /// `SslContext` with [`SslRef::set_task_waker`].
71    ///
72    /// See [`SslContextBuilder::set_select_certificate_callback`] for the sync
73    /// setter of this callback.
74    pub fn set_async_select_certificate_callback<F>(&mut self, callback: F)
75    where
76        F: Fn(&mut ClientHello<'_>) -> Result<BoxSelectCertFuture, AsyncSelectCertError>
77            + Send
78            + Sync
79            + 'static,
80    {
81        self.set_select_certificate_callback(move |mut client_hello| {
82            let fut_poll_result = with_ex_data_future(
83                &mut client_hello,
84                *SELECT_CERT_FUTURE_INDEX,
85                ClientHello::ssl_mut,
86                &callback,
87                identity,
88            );
89
90            let fut_result = match fut_poll_result {
91                Poll::Ready(fut_result) => fut_result,
92                Poll::Pending => return Err(SelectCertError::RETRY),
93            };
94
95            let finish = fut_result.or(Err(SelectCertError::ERROR))?;
96
97            finish(client_hello).or(Err(SelectCertError::ERROR))
98        })
99    }
100
101    /// Configures a custom private key method on the context.
102    ///
103    /// A task waker must be set on `Ssl` values associated with the resulting
104    /// `SslContext` with [`SslRef::set_task_waker`].
105    ///
106    /// See [`AsyncPrivateKeyMethod`] for more details.
107    pub fn set_async_private_key_method(&mut self, method: impl AsyncPrivateKeyMethod) {
108        self.set_private_key_method(AsyncPrivateKeyMethodBridge(Box::new(method)));
109    }
110
111    /// Sets a callback that is called when a client proposed to resume a session
112    /// but it was not found in the internal cache.
113    ///
114    /// The callback is passed a reference to the session ID provided by the client.
115    /// It should return the session corresponding to that ID if available. This is
116    /// only used for servers, not clients.
117    ///
118    /// A task waker must be set on `Ssl` values associated with the resulting
119    /// `SslContext` with [`SslRef::set_task_waker`].
120    ///
121    /// See [`SslContextBuilder::set_get_session_callback`] for the sync setter
122    /// of this callback.
123    ///
124    /// # Safety
125    ///
126    /// The returned [`SslSession`] must not be associated with a different [`SslContextBuilder`].
127    pub unsafe fn set_async_get_session_callback<F>(&mut self, callback: F)
128    where
129        F: Fn(&mut SslRef, &[u8]) -> Option<BoxGetSessionFuture> + Send + Sync + 'static,
130    {
131        let async_callback = move |ssl: &mut SslRef, id: &[u8]| {
132            let fut_poll_result = with_ex_data_future(
133                &mut *ssl,
134                *SELECT_GET_SESSION_FUTURE_INDEX,
135                |ssl| ssl,
136                |ssl| callback(ssl, id).ok_or(()),
137                |option| option.ok_or(()),
138            );
139
140            match fut_poll_result {
141                Poll::Ready(Err(())) => Ok(None),
142                Poll::Ready(Ok(finish)) => Ok(finish(ssl, id)),
143                Poll::Pending => Err(GetSessionPendingError),
144            }
145        };
146
147        self.set_get_session_callback(async_callback)
148    }
149
150    /// Configures certificate verification.
151    ///
152    /// The callback should return `Ok(())` if the certificate is valid.
153    /// If the certificate is invalid, the callback should return `SslVerifyError::Invalid(alert)`.
154    /// Some useful alerts include [`SslAlert::CERTIFICATE_EXPIRED`], [`SslAlert::CERTIFICATE_REVOKED`],
155    /// [`SslAlert::UNKNOWN_CA`], [`SslAlert::BAD_CERTIFICATE`], [`SslAlert::CERTIFICATE_UNKNOWN`],
156    /// and [`SslAlert::INTERNAL_ERROR`]. See RFC 5246 section 7.2.2 for their precise meanings.
157    ///
158    /// A task waker must be set on `Ssl` values associated with the resulting
159    /// `SslContext` with [`SslRef::set_task_waker`].
160    ///
161    /// See [`SslContextBuilder::set_custom_verify_callback`] for the sync version of this method.
162    ///
163    /// # Panics
164    ///
165    /// This method panics if this `Ssl` is associated with a RPK context.
166    pub fn set_async_custom_verify_callback<F>(&mut self, mode: SslVerifyMode, callback: F)
167    where
168        F: Fn(&mut SslRef) -> Result<BoxCustomVerifyFuture, SslAlert> + Send + Sync + 'static,
169    {
170        self.set_custom_verify_callback(mode, async_custom_verify_callback(callback))
171    }
172}
173
174impl SslRef {
175    pub fn set_async_custom_verify_callback<F>(&mut self, mode: SslVerifyMode, callback: F)
176    where
177        F: Fn(&mut SslRef) -> Result<BoxCustomVerifyFuture, SslAlert> + Send + Sync + 'static,
178    {
179        self.set_custom_verify_callback(mode, async_custom_verify_callback(callback))
180    }
181
182    /// Sets the task waker to be used in async callbacks installed on this `Ssl`.
183    pub fn set_task_waker(&mut self, waker: Option<Waker>) {
184        self.replace_ex_data(*TASK_WAKER_INDEX, waker);
185    }
186}
187
188fn async_custom_verify_callback<F>(
189    callback: F,
190) -> impl Fn(&mut SslRef) -> Result<(), SslVerifyError>
191where
192    F: Fn(&mut SslRef) -> Result<BoxCustomVerifyFuture, SslAlert> + Send + Sync + 'static,
193{
194    move |ssl| {
195        let fut_poll_result = with_ex_data_future(
196            &mut *ssl,
197            *SELECT_CUSTOM_VERIFY_FUTURE_INDEX,
198            |ssl| ssl,
199            &callback,
200            identity,
201        );
202
203        match fut_poll_result {
204            Poll::Ready(Err(alert)) => Err(SslVerifyError::Invalid(alert)),
205            Poll::Ready(Ok(finish)) => Ok(finish(ssl).map_err(SslVerifyError::Invalid)?),
206            Poll::Pending => Err(SslVerifyError::Retry),
207        }
208    }
209}
210
211/// A fatal error to be returned from async select certificate callbacks.
212#[derive(Debug, Copy, Clone, PartialEq, Eq)]
213pub struct AsyncSelectCertError;
214
215/// Describes async private key hooks. This is used to off-load signing
216/// operations to a custom, potentially asynchronous, backend. Metadata about the
217/// key such as the type and size are parsed out of the certificate.
218///
219/// See [`PrivateKeyMethod`] for the sync version of those hooks.
220///
221/// [`ssl_private_key_method_st`]: https://commondatastorage.googleapis.com/chromium-boringssl-docs/ssl.h.html#ssl_private_key_method_st
222pub trait AsyncPrivateKeyMethod: Send + Sync + 'static {
223    /// Signs the message `input` using the specified signature algorithm.
224    ///
225    /// This method uses a function that returns a future whose output is
226    /// itself a closure that will be passed `ssl` and `output`
227    /// to finish writing the signature.
228    ///
229    /// See [`PrivateKeyMethod::sign`] for the sync version of this method.
230    fn sign(
231        &self,
232        ssl: &mut SslRef,
233        input: &[u8],
234        signature_algorithm: SslSignatureAlgorithm,
235        output: &mut [u8],
236    ) -> Result<BoxPrivateKeyMethodFuture, AsyncPrivateKeyMethodError>;
237
238    /// Decrypts `input`.
239    ///
240    /// This method uses a function that returns a future whose output is
241    /// itself a closure that will be passed `ssl` and `output`
242    /// to finish decrypting the input.
243    ///
244    /// See [`PrivateKeyMethod::decrypt`] for the sync version of this method.
245    fn decrypt(
246        &self,
247        ssl: &mut SslRef,
248        input: &[u8],
249        output: &mut [u8],
250    ) -> Result<BoxPrivateKeyMethodFuture, AsyncPrivateKeyMethodError>;
251}
252
253/// A fatal error to be returned from async private key methods.
254#[derive(Debug, Copy, Clone, PartialEq, Eq)]
255pub struct AsyncPrivateKeyMethodError;
256
257struct AsyncPrivateKeyMethodBridge(Box<dyn AsyncPrivateKeyMethod>);
258
259impl PrivateKeyMethod for AsyncPrivateKeyMethodBridge {
260    fn sign(
261        &self,
262        ssl: &mut SslRef,
263        input: &[u8],
264        signature_algorithm: SslSignatureAlgorithm,
265        output: &mut [u8],
266    ) -> Result<usize, PrivateKeyMethodError> {
267        with_private_key_method(ssl, output, |ssl, output| {
268            <dyn AsyncPrivateKeyMethod>::sign(&*self.0, ssl, input, signature_algorithm, output)
269        })
270    }
271
272    fn decrypt(
273        &self,
274        ssl: &mut SslRef,
275        input: &[u8],
276        output: &mut [u8],
277    ) -> Result<usize, PrivateKeyMethodError> {
278        with_private_key_method(ssl, output, |ssl, output| {
279            <dyn AsyncPrivateKeyMethod>::decrypt(&*self.0, ssl, input, output)
280        })
281    }
282
283    fn complete(
284        &self,
285        ssl: &mut SslRef,
286        output: &mut [u8],
287    ) -> Result<usize, PrivateKeyMethodError> {
288        with_private_key_method(ssl, output, |_, _| {
289            // This should never be reached, if it does, that's a bug on boring's side,
290            // which called `complete` without having been returned to with a pending
291            // future from `sign` or `decrypt`.
292
293            if cfg!(debug_assertions) {
294                panic!("BUG: boring called complete without a pending operation");
295            }
296
297            Err(AsyncPrivateKeyMethodError)
298        })
299    }
300}
301
302/// Creates and drives a private key method future.
303///
304/// This is a convenience function for the three methods of impl `PrivateKeyMethod``
305/// for `dyn AsyncPrivateKeyMethod`. It relies on [`with_ex_data_future`] to
306/// drive the future and then immediately calls the final [`BoxPrivateKeyMethodFinish`]
307/// when the future is ready.
308fn with_private_key_method(
309    ssl: &mut SslRef,
310    output: &mut [u8],
311    create_fut: impl FnOnce(
312        &mut SslRef,
313        &mut [u8],
314    ) -> Result<BoxPrivateKeyMethodFuture, AsyncPrivateKeyMethodError>,
315) -> Result<usize, PrivateKeyMethodError> {
316    let fut_poll_result = with_ex_data_future(
317        ssl,
318        *SELECT_PRIVATE_KEY_METHOD_FUTURE_INDEX,
319        |ssl| ssl,
320        |ssl| create_fut(ssl, output),
321        identity,
322    );
323
324    let fut_result = match fut_poll_result {
325        Poll::Ready(fut_result) => fut_result,
326        Poll::Pending => return Err(PrivateKeyMethodError::RETRY),
327    };
328
329    let finish = fut_result.or(Err(PrivateKeyMethodError::FAILURE))?;
330
331    finish(ssl, output).or(Err(PrivateKeyMethodError::FAILURE))
332}
333
334/// Creates and drives a future stored in `ssl_handle`'s `Ssl` at ex data index `index`.
335///
336/// This function won't even bother storing the future in `index` if the future
337/// created by `create_fut` returns `Poll::Ready(_)` on the first poll call.
338fn with_ex_data_future<H, R, T, E>(
339    ssl_handle: &mut H,
340    index: Index<Ssl, MutOnly<Option<ExDataFuture<R>>>>,
341    get_ssl_mut: impl Fn(&mut H) -> &mut SslRef,
342    create_fut: impl FnOnce(&mut H) -> Result<ExDataFuture<R>, E>,
343    into_result: impl Fn(R) -> Result<T, E>,
344) -> Poll<Result<T, E>> {
345    let ssl = get_ssl_mut(ssl_handle);
346    let waker = ssl
347        .ex_data(*TASK_WAKER_INDEX)
348        .cloned()
349        .flatten()
350        .expect("task waker should be set");
351
352    let mut ctx = Context::from_waker(&waker);
353
354    if let Some(data @ Some(_)) = ssl.ex_data_mut(index).map(MutOnly::get_mut) {
355        let fut_result = into_result(ready!(data.as_mut().unwrap().as_mut().poll(&mut ctx)));
356
357        *data = None;
358
359        Poll::Ready(fut_result)
360    } else {
361        let mut fut = create_fut(ssl_handle)?;
362
363        match fut.as_mut().poll(&mut ctx) {
364            Poll::Ready(fut_result) => Poll::Ready(into_result(fut_result)),
365            Poll::Pending => {
366                get_ssl_mut(ssl_handle).replace_ex_data(index, MutOnly::new(Some(fut)));
367
368                Poll::Pending
369            }
370        }
371    }
372}
boring/ssl/async_callbacks.rs

boring/ssl/
async_callbacks.rs
