1use crate::error::ErrorStack;
2use foreign_types::{ForeignType, ForeignTypeRef};
3use libc::{c_char, c_int, c_void};
4use std::any::Any;
5use std::panic::{self, AssertUnwindSafe};
6use std::slice;
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.
12pub 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
20impl<F> CallbackState<F> {
21    pub fn new(callback: F) -> Self {
22        CallbackState {
23            cb: Some(callback),
24            panic: None,
25        }
26    }
27}
28
29impl<F> Drop for CallbackState<F> {
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`.
40pub 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
46where
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
69pub trait ForeignTypeExt: ForeignType {
70    unsafe fn from_ptr_opt(ptr: *mut Self::CType) -> Option<Self> {
71        if ptr.is_null() {
72            None
73        } else {
74            Some(Self::from_ptr(ptr))
75        }
76    }
77}
78impl<FT: ForeignType> ForeignTypeExt for FT {}
79
80pub trait ForeignTypeRefExt: ForeignTypeRef {
81    unsafe fn from_const_ptr<'a>(ptr: *const Self::CType) -> &'a Self {
82        Self::from_ptr(ptr as *mut Self::CType)
83    }
84
85    unsafe fn from_const_ptr_opt<'a>(ptr: *const Self::CType) -> Option<&'a Self> {
86        if ptr.is_null() {
87            None
88        } else {
89            Some(Self::from_const_ptr(ptr as *mut Self::CType))
90        }
91    }
92}
93impl<FT: ForeignTypeRef> ForeignTypeRefExt for FT {}
94