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};
7#[cfg(feature = "credential")]
8use crate::error::ErrorStack;
9use crate::ex_data::Index;
10#[cfg(feature = "credential")]
11use crate::ssl::SslCredentialBuilder;
12use std::convert::identity;
13use std::future::Future;
14use std::pin::Pin;
15use std::sync::LazyLock;
16use std::task::{ready, Context, Poll, Waker};
17
18/// The type of futures to pass to [`SslContextBuilder::set_async_select_certificate_callback`].
19pub type BoxSelectCertFuture = ExDataFuture<Result<BoxSelectCertFinish, AsyncSelectCertError>>;
20
21/// The type of callbacks returned by [`BoxSelectCertFuture`] methods.
22pub type BoxSelectCertFinish = Box<dyn FnOnce(ClientHello<'_>) -> Result<(), AsyncSelectCertError>>;
23
24/// The type of futures returned by [`AsyncPrivateKeyMethod`] methods.
25pub type BoxPrivateKeyMethodFuture =
26    ExDataFuture<Result<BoxPrivateKeyMethodFinish, AsyncPrivateKeyMethodError>>;
27
28/// The type of callbacks returned by [`BoxPrivateKeyMethodFuture`].
29pub type BoxPrivateKeyMethodFinish =
30    Box<dyn FnOnce(&mut SslRef, &mut [u8]) -> Result<usize, AsyncPrivateKeyMethodError>>;
31
32/// The type of futures to pass to [`SslContextBuilder::set_async_get_session_callback`].
33pub type BoxGetSessionFuture = ExDataFuture<Option<BoxGetSessionFinish>>;
34
35/// The type of callbacks returned by [`BoxSelectCertFuture`] methods.
36pub type BoxGetSessionFinish = Box<dyn FnOnce(&mut SslRef, &[u8]) -> Option<SslSession>>;
37
38/// The type of futures to pass to [`SslContextBuilder::set_async_custom_verify_callback`].
39pub type BoxCustomVerifyFuture = ExDataFuture<Result<BoxCustomVerifyFinish, SslAlert>>;
40
41/// The type of callbacks returned by [`BoxCustomVerifyFuture`] methods.
42pub type BoxCustomVerifyFinish = Box<dyn FnOnce(&mut SslRef) -> Result<(), SslAlert>>;
43
44/// Convenience alias for futures stored in [`Ssl`] ex data by [`SslContextBuilder`] methods.
45///
46/// Public for documentation purposes.
47pub type ExDataFuture<T> = Pin<Box<dyn Future<Output = T> + Send>>;
48
49pub(crate) static TASK_WAKER_INDEX: LazyLock<Index<Ssl, Option<Waker>>> =
50    LazyLock::new(|| Ssl::new_ex_index().unwrap());
51pub(crate) static SELECT_CERT_FUTURE_INDEX: LazyLock<
52    Index<Ssl, MutOnly<Option<BoxSelectCertFuture>>>,
53> = LazyLock::new(|| Ssl::new_ex_index().unwrap());
54pub(crate) static SELECT_PRIVATE_KEY_METHOD_FUTURE_INDEX: LazyLock<
55    Index<Ssl, MutOnly<Option<BoxPrivateKeyMethodFuture>>>,
56> = LazyLock::new(|| Ssl::new_ex_index().unwrap());
57pub(crate) static SELECT_GET_SESSION_FUTURE_INDEX: LazyLock<
58    Index<Ssl, MutOnly<Option<BoxGetSessionFuture>>>,
59> = LazyLock::new(|| Ssl::new_ex_index().unwrap());
60pub(crate) static SELECT_CUSTOM_VERIFY_FUTURE_INDEX: LazyLock<
61    Index<Ssl, MutOnly<Option<BoxCustomVerifyFuture>>>,
62> = LazyLock::new(|| Ssl::new_ex_index().unwrap());
63
64impl SslContextBuilder {
65    /// Sets a callback that is called before most [`ClientHello`] processing
66    /// and before the decision whether to resume a session is made. The
67    /// callback may inspect the [`ClientHello`] and configure the connection.
68    ///
69    /// This method uses a function that returns a future whose output is
70    /// itself a closure that will be passed [`ClientHello`] to configure
71    /// the connection based on the computations done in the future.
72    ///
73    /// A task waker must be set on `Ssl` values associated with the resulting
74    /// `SslContext` with [`SslRef::set_task_waker`].
75    ///
76    /// See [`SslContextBuilder::set_select_certificate_callback`] for the sync
77    /// setter of this callback.
78    pub fn set_async_select_certificate_callback<F>(&mut self, callback: F)
79    where
80        F: Fn(&mut ClientHello<'_>) -> Result<BoxSelectCertFuture, AsyncSelectCertError>
81            + Send
82            + Sync
83            + 'static,
84    {
85        self.set_select_certificate_callback(move |mut client_hello| {
86            let fut_poll_result = with_ex_data_future(
87                &mut client_hello,
88                *SELECT_CERT_FUTURE_INDEX,
89                ClientHello::ssl_mut,
90                &callback,
91                identity,
92            );
93
94            let fut_result = match fut_poll_result {
95                Poll::Ready(fut_result) => fut_result,
96                Poll::Pending => return Err(SelectCertError::RETRY),
97            };
98
99            let finish = fut_result.or(Err(SelectCertError::ERROR))?;
100
101            finish(client_hello).or(Err(SelectCertError::ERROR))
102        });
103    }
104
105    /// Configures a custom private key method on the context.
106    ///
107    /// A task waker must be set on `Ssl` values associated with the resulting
108    /// `SslContext` with [`SslRef::set_task_waker`].
109    ///
110    /// See [`AsyncPrivateKeyMethod`] for more details.
111    pub fn set_async_private_key_method(&mut self, method: impl AsyncPrivateKeyMethod) {
112        self.set_private_key_method(AsyncPrivateKeyMethodBridge(Box::new(method)));
113    }
114
115    /// Sets a callback that is called when a client proposed to resume a session
116    /// but it was not found in the internal cache.
117    ///
118    /// The callback is passed a reference to the session ID provided by the client.
119    /// It should return the session corresponding to that ID if available. This is
120    /// only used for servers, not clients.
121    ///
122    /// A task waker must be set on `Ssl` values associated with the resulting
123    /// `SslContext` with [`SslRef::set_task_waker`].
124    ///
125    /// See [`SslContextBuilder::set_get_session_callback`] for the sync setter
126    /// of this callback.
127    ///
128    /// # Safety
129    ///
130    /// The returned [`SslSession`] must not be associated with a different [`SslContextBuilder`].
131    pub unsafe fn set_async_get_session_callback<F>(&mut self, callback: F)
132    where
133        F: Fn(&mut SslRef, &[u8]) -> Option<BoxGetSessionFuture> + Send + Sync + 'static,
134    {
135        let async_callback = move |ssl: &mut SslRef, id: &[u8]| {
136            let fut_poll_result = with_ex_data_future(
137                &mut *ssl,
138                *SELECT_GET_SESSION_FUTURE_INDEX,
139                |ssl| ssl,
140                |ssl| callback(ssl, id).ok_or(()),
141                |option| option.ok_or(()),
142            );
143
144            match fut_poll_result {
145                Poll::Ready(Err(())) => Ok(None),
146                Poll::Ready(Ok(finish)) => Ok(finish(ssl, id)),
147                Poll::Pending => Err(GetSessionPendingError),
148            }
149        };
150
151        self.set_get_session_callback(async_callback);
152    }
153
154    /// Configures certificate verification.
155    ///
156    /// The callback should return `Ok(())` if the certificate is valid.
157    /// If the certificate is invalid, the callback should return `SslVerifyError::Invalid(alert)`.
158    /// Some useful alerts include [`SslAlert::CERTIFICATE_EXPIRED`], [`SslAlert::CERTIFICATE_REVOKED`],
159    /// [`SslAlert::UNKNOWN_CA`], [`SslAlert::BAD_CERTIFICATE`], [`SslAlert::CERTIFICATE_UNKNOWN`],
160    /// and [`SslAlert::INTERNAL_ERROR`]. See RFC 5246 section 7.2.2 for their precise meanings.
161    ///
162    /// A task waker must be set on `Ssl` values associated with the resulting
163    /// `SslContext` with [`SslRef::set_task_waker`].
164    ///
165    /// See [`SslContextBuilder::set_custom_verify_callback`] for the sync version of this method.
166    ///
167    /// # Panics
168    ///
169    /// This method panics if this `Ssl` is associated with a RPK context.
170    pub fn set_async_custom_verify_callback<F>(&mut self, mode: SslVerifyMode, callback: F)
171    where
172        F: Fn(&mut SslRef) -> Result<BoxCustomVerifyFuture, SslAlert> + Send + Sync + 'static,
173    {
174        self.set_custom_verify_callback(mode, async_custom_verify_callback(callback));
175    }
176}
177
178#[cfg(feature = "credential")]
179impl SslCredentialBuilder {
180    /// Configures a custom private key method on the context.
181    ///
182    /// A task waker must be set on `Ssl` values associated with the resulting
183    /// `SslContext` with [`SslRef::set_task_waker`].
184    ///
185    /// See [`AsyncPrivateKeyMethod`] for more details.
186    pub fn set_async_private_key_method(
187        &mut self,
188        method: impl AsyncPrivateKeyMethod,
189    ) -> Result<(), ErrorStack> {
190        self.set_private_key_method(AsyncPrivateKeyMethodBridge(Box::new(method)))
191    }
192}
193
194impl SslRef {
195    pub fn set_async_custom_verify_callback<F>(&mut self, mode: SslVerifyMode, callback: F)
196    where
197        F: Fn(&mut SslRef) -> Result<BoxCustomVerifyFuture, SslAlert> + Send + Sync + 'static,
198    {
199        self.set_custom_verify_callback(mode, async_custom_verify_callback(callback));
200    }
201
202    /// Sets the task waker to be used in async callbacks installed on this `Ssl`.
203    pub fn set_task_waker(&mut self, waker: Option<Waker>) {
204        self.replace_ex_data(*TASK_WAKER_INDEX, waker);
205    }
206}
207
208fn async_custom_verify_callback<F>(
209    callback: F,
210) -> impl Fn(&mut SslRef) -> Result<(), SslVerifyError>
211where
212    F: Fn(&mut SslRef) -> Result<BoxCustomVerifyFuture, SslAlert> + Send + Sync + 'static,
213{
214    move |ssl| {
215        let fut_poll_result = with_ex_data_future(
216            &mut *ssl,
217            *SELECT_CUSTOM_VERIFY_FUTURE_INDEX,
218            |ssl| ssl,
219            &callback,
220            identity,
221        );
222
223        match fut_poll_result {
224            Poll::Ready(Err(alert)) => Err(SslVerifyError::Invalid(alert)),
225            Poll::Ready(Ok(finish)) => Ok(finish(ssl).map_err(SslVerifyError::Invalid)?),
226            Poll::Pending => Err(SslVerifyError::Retry),
227        }
228    }
229}
230
231/// A fatal error to be returned from async select certificate callbacks.
232#[derive(Debug, Copy, Clone, PartialEq, Eq)]
233pub struct AsyncSelectCertError;
234
235/// Describes async private key hooks. This is used to off-load signing
236/// operations to a custom, potentially asynchronous, backend. Metadata about the
237/// key such as the type and size are parsed out of the certificate.
238///
239/// See [`PrivateKeyMethod`] for the sync version of those hooks.
240///
241/// [`ssl_private_key_method_st`]: https://commondatastorage.googleapis.com/chromium-boringssl-docs/ssl.h.html#ssl_private_key_method_st
242pub trait AsyncPrivateKeyMethod: Send + Sync + 'static {
243    /// Signs the message `input` using the specified signature algorithm.
244    ///
245    /// This method uses a function that returns a future whose output is
246    /// itself a closure that will be passed `ssl` and `output`
247    /// to finish writing the signature.
248    ///
249    /// See [`PrivateKeyMethod::sign`] for the sync version of this method.
250    fn sign(
251        &self,
252        ssl: &mut SslRef,
253        input: &[u8],
254        signature_algorithm: SslSignatureAlgorithm,
255        output: &mut [u8],
256    ) -> Result<BoxPrivateKeyMethodFuture, AsyncPrivateKeyMethodError>;
257
258    /// Decrypts `input`.
259    ///
260    /// This method uses a function that returns a future whose output is
261    /// itself a closure that will be passed `ssl` and `output`
262    /// to finish decrypting the input.
263    ///
264    /// See [`PrivateKeyMethod::decrypt`] for the sync version of this method.
265    fn decrypt(
266        &self,
267        ssl: &mut SslRef,
268        input: &[u8],
269        output: &mut [u8],
270    ) -> Result<BoxPrivateKeyMethodFuture, AsyncPrivateKeyMethodError>;
271}
272
273/// A fatal error to be returned from async private key methods.
274#[derive(Debug, Copy, Clone, PartialEq, Eq)]
275pub struct AsyncPrivateKeyMethodError;
276
277struct AsyncPrivateKeyMethodBridge(Box<dyn AsyncPrivateKeyMethod>);
278
279impl PrivateKeyMethod for AsyncPrivateKeyMethodBridge {
280    fn sign(
281        &self,
282        ssl: &mut SslRef,
283        input: &[u8],
284        signature_algorithm: SslSignatureAlgorithm,
285        output: &mut [u8],
286    ) -> Result<usize, PrivateKeyMethodError> {
287        with_private_key_method(ssl, output, |ssl, output| {
288            <dyn AsyncPrivateKeyMethod>::sign(&*self.0, ssl, input, signature_algorithm, output)
289        })
290    }
291
292    fn decrypt(
293        &self,
294        ssl: &mut SslRef,
295        input: &[u8],
296        output: &mut [u8],
297    ) -> Result<usize, PrivateKeyMethodError> {
298        with_private_key_method(ssl, output, |ssl, output| {
299            <dyn AsyncPrivateKeyMethod>::decrypt(&*self.0, ssl, input, output)
300        })
301    }
302
303    fn complete(
304        &self,
305        ssl: &mut SslRef,
306        output: &mut [u8],
307    ) -> Result<usize, PrivateKeyMethodError> {
308        with_private_key_method(ssl, output, |_, _| {
309            // This should never be reached, if it does, that's a bug on boring's side,
310            // which called `complete` without having been returned to with a pending
311            // future from `sign` or `decrypt`.
312
313            if cfg!(debug_assertions) {
314                panic!("BUG: boring called complete without a pending operation");
315            }
316
317            Err(AsyncPrivateKeyMethodError)
318        })
319    }
320}
321
322/// Creates and drives a private key method future.
323///
324/// This is a convenience function for the three methods of impl `PrivateKeyMethod``
325/// for `dyn AsyncPrivateKeyMethod`. It relies on [`with_ex_data_future`] to
326/// drive the future and then immediately calls the final [`BoxPrivateKeyMethodFinish`]
327/// when the future is ready.
328fn with_private_key_method(
329    ssl: &mut SslRef,
330    output: &mut [u8],
331    create_fut: impl FnOnce(
332        &mut SslRef,
333        &mut [u8],
334    ) -> Result<BoxPrivateKeyMethodFuture, AsyncPrivateKeyMethodError>,
335) -> Result<usize, PrivateKeyMethodError> {
336    let fut_poll_result = with_ex_data_future(
337        ssl,
338        *SELECT_PRIVATE_KEY_METHOD_FUTURE_INDEX,
339        |ssl| ssl,
340        |ssl| create_fut(ssl, output),
341        identity,
342    );
343
344    let fut_result = match fut_poll_result {
345        Poll::Ready(fut_result) => fut_result,
346        Poll::Pending => return Err(PrivateKeyMethodError::RETRY),
347    };
348
349    let finish = fut_result.or(Err(PrivateKeyMethodError::FAILURE))?;
350
351    finish(ssl, output).or(Err(PrivateKeyMethodError::FAILURE))
352}
353
354/// Creates and drives a future stored in `ssl_handle`'s `Ssl` at ex data index `index`.
355///
356/// This function won't even bother storing the future in `index` if the future
357/// created by `create_fut` returns `Poll::Ready(_)` on the first poll call.
358fn with_ex_data_future<H, R, T, E>(
359    ssl_handle: &mut H,
360    index: Index<Ssl, MutOnly<Option<ExDataFuture<R>>>>,
361    get_ssl_mut: impl Fn(&mut H) -> &mut SslRef,
362    create_fut: impl FnOnce(&mut H) -> Result<ExDataFuture<R>, E>,
363    into_result: impl Fn(R) -> Result<T, E>,
364) -> Poll<Result<T, E>> {
365    let ssl = get_ssl_mut(ssl_handle);
366    let waker = ssl
367        .ex_data(*TASK_WAKER_INDEX)
368        .cloned()
369        .flatten()
370        .expect("task waker should be set");
371
372    let mut ctx = Context::from_waker(&waker);
373
374    if let Some(data @ Some(_)) = ssl.ex_data_mut(index).map(MutOnly::get_mut) {
375        let fut_result = into_result(ready!(data.as_mut().unwrap().as_mut().poll(&mut ctx)));
376
377        *data = None;
378
379        Poll::Ready(fut_result)
380    } else {
381        let mut fut = create_fut(ssl_handle)?;
382
383        match fut.as_mut().poll(&mut ctx) {
384            Poll::Ready(fut_result) => Poll::Ready(into_result(fut_result)),
385            Poll::Pending => {
386                get_ssl_mut(ssl_handle).replace_ex_data(index, MutOnly::new(Some(fut)));
387
388                Poll::Pending
389            }
390        }
391    }
392}
boring/ssl/async_callbacks.rs

boring/ssl/
async_callbacks.rs
