1 use libc::{c_char, c_int, c_void};
2 use std::any::Any;
3 use std::panic::{self, AssertUnwindSafe};
4 use std::slice;
5
6 use error::ErrorStack;
7
8 /// Wraps a user-supplied callback and a slot for panics thrown inside the callback (while FFI
9 /// frames are on the stack).
10 ///
11 /// When dropped, checks if the callback has panicked, and resumes unwinding if so.
12 pub struct CallbackState<F> {
13 /// The user callback. Taken out of the `Option` when called.
14 cb: Option<F>,
15 /// If the callback panics, we place the panic object here, to be re-thrown once OpenSSL
16 /// returns.
17 panic: Option<Box<dyn Any + Send + 'static>>,
18 }
19
20 impl<F> CallbackState<F> {
new(callback: F) -> Self21 pub fn new(callback: F) -> Self {
22 CallbackState {
23 cb: Some(callback),
24 panic: None,
25 }
26 }
27 }
28
29 impl<F> Drop for CallbackState<F> {
drop(&mut self)30 fn drop(&mut self) {
31 if let Some(panic) = self.panic.take() {
32 panic::resume_unwind(panic);
33 }
34 }
35 }
36
37 /// Password callback function, passed to private key loading functions.
38 ///
39 /// `cb_state` is expected to be a pointer to a `CallbackState`.
invoke_passwd_cb<F>( buf: *mut c_char, size: c_int, _rwflag: c_int, cb_state: *mut c_void, ) -> c_int where F: FnOnce(&mut [u8]) -> Result<usize, ErrorStack>,40 pub unsafe extern "C" fn invoke_passwd_cb<F>(
41 buf: *mut c_char,
42 size: c_int,
43 _rwflag: c_int,
44 cb_state: *mut c_void,
45 ) -> c_int
46 where
47 F: FnOnce(&mut [u8]) -> Result<usize, ErrorStack>,
48 {
49 let callback = &mut *(cb_state as *mut CallbackState<F>);
50
51 let result = panic::catch_unwind(AssertUnwindSafe(|| {
52 let pass_slice = slice::from_raw_parts_mut(buf as *mut u8, size as usize);
53 callback.cb.take().unwrap()(pass_slice)
54 }));
55
56 match result {
57 Ok(Ok(len)) => len as c_int,
58 Ok(Err(_)) => {
59 // FIXME restore error stack
60 0
61 }
62 Err(err) => {
63 callback.panic = Some(err);
64 0
65 }
66 }
67 }
68