From 8119f06ca5ca50a677cf584cbe816500153ce783 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonas@schievink.net>
Date: Tue, 14 Jun 2016 18:12:50 +0200
Subject: [PATCH] Move into utility module

---
 openssl/src/crypto/mod.rs  |  1 +
 openssl/src/crypto/pkey.rs | 43 +++-------------------------
 openssl/src/crypto/util.rs | 58 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 39 deletions(-)
 create mode 100644 openssl/src/crypto/util.rs

diff --git a/openssl/src/crypto/mod.rs b/openssl/src/crypto/mod.rs
index 95b27022..9d79b8b0 100644
--- a/openssl/src/crypto/mod.rs
+++ b/openssl/src/crypto/mod.rs
@@ -24,6 +24,7 @@ pub mod rand;
 pub mod symm;
 pub mod memcmp;
 pub mod rsa;
+mod util;
 
 mod symm_internal;
 
diff --git a/openssl/src/crypto/pkey.rs b/openssl/src/crypto/pkey.rs
index 8ae9aa20..605aed42 100644
--- a/openssl/src/crypto/pkey.rs
+++ b/openssl/src/crypto/pkey.rs
@@ -1,12 +1,9 @@
-use libc::{c_int, c_uint, c_ulong, c_char, c_void};
-use std::any::Any;
+use libc::{c_int, c_uint, c_ulong, c_void};
 use std::io;
 use std::io::prelude::*;
 use std::iter::repeat;
 use std::mem;
-use std::panic;
 use std::ptr;
-use std::slice;
 use bio::MemBio;
 
 use crypto::HashTypeInternals;
@@ -15,6 +12,7 @@ use crypto::hash::Type as HashType;
 use ffi;
 use ssl::error::{SslError, StreamError};
 use crypto::rsa::RSA;
+use crypto::util::{CallbackState, invoke_passwd_cb};
 
 #[derive(Copy, Clone)]
 pub enum Parts {
@@ -104,36 +102,7 @@ impl PKey {
     pub fn private_key_from_pem_cb<R, F>(reader: &mut R, pass_cb: F) -> Result<PKey, SslError>
         where R: Read, F: FnMut(&mut [i8]) -> usize
     {
-        struct CallbackState<F: FnMut(&mut [i8]) -> usize> {
-            cb: F,
-            panic: Option<Box<Any + Send + 'static>>,
-        }
-
-        extern "C" fn user_cb_wrapper<F>(buf: *mut c_char,
-                                         size: c_int,
-                                         _rwflag: c_int,
-                                         user_cb: *mut c_void)
-                                         -> c_int
-                                         where F: FnMut(&mut [i8]) -> usize {
-            let result = panic::catch_unwind(|| {
-                // build a `i8` slice to pass to the user callback
-                let pass_slice = unsafe { slice::from_raw_parts_mut(buf, size as usize) };
-                let callback = unsafe { &mut *(user_cb as *mut CallbackState<F>) };
-
-                (callback.cb)(pass_slice)
-            });
-
-            if let Ok(len) = result {
-                return len as c_int;
-            } else {
-                return 0;
-            }
-        }
-
-        let mut cb = CallbackState {
-            cb: pass_cb,
-            panic: None,
-        };
+        let mut cb = CallbackState::new(pass_cb);
 
         let mut mem_bio = try!(MemBio::new());
         try!(io::copy(reader, &mut mem_bio).map_err(StreamError));
@@ -141,13 +110,9 @@ impl PKey {
         unsafe {
             let evp = try_ssl_null!(ffi::PEM_read_bio_PrivateKey(mem_bio.get_handle(),
                                                                  ptr::null_mut(),
-                                                                 Some(user_cb_wrapper::<F>),
+                                                                 Some(invoke_passwd_cb::<F>),
                                                                  &mut cb as *mut _ as *mut c_void));
 
-            if let Some(panic) = cb.panic {
-                panic::resume_unwind(panic);
-            }
-
             Ok(PKey {
                 evp: evp as *mut ffi::EVP_PKEY,
                 parts: Parts::Both,
diff --git a/openssl/src/crypto/util.rs b/openssl/src/crypto/util.rs
new file mode 100644
index 00000000..85df86b7
--- /dev/null
+++ b/openssl/src/crypto/util.rs
@@ -0,0 +1,58 @@
+use libc::{c_int, c_char, c_void};
+
+use std::any::Any;
+use std::panic;
+use std::slice;
+
+/// Wraps a user-supplied callback and a slot for panics thrown inside the callback (while FFI
+/// frames are on the stack).
+///
+/// When dropped, checks if the callback has panicked, and resumes unwinding if so.
+pub struct CallbackState<F> {
+    /// The user callback. Taken out of the `Option` when called.
+    cb: Option<F>,
+    /// If the callback panics, we place the panic object here, to be re-thrown once OpenSSL
+    /// returns.
+    panic: Option<Box<Any + Send + 'static>>,
+}
+
+impl<F> CallbackState<F> {
+    pub fn new(callback: F) -> Self {
+        CallbackState {
+            cb: Some(callback),
+            panic: None,
+        }
+    }
+}
+
+impl<F> Drop for CallbackState<F> {
+    fn drop(&mut self) {
+        if let Some(panic) = self.panic.take() {
+            panic::resume_unwind(panic);
+        }
+    }
+}
+
+/// Password callback function, passed to private key loading functions.
+///
+/// `cb_state` is expected to be a pointer to a `CallbackState`.
+pub extern "C" fn invoke_passwd_cb<F>(buf: *mut c_char,
+                                      size: c_int,
+                                      _rwflag: c_int,
+                                      cb_state: *mut c_void)
+                                      -> c_int
+                                      where F: FnMut(&mut [i8]) -> usize {
+    let result = panic::catch_unwind(|| {
+        // build a `i8` slice to pass to the user callback
+        let pass_slice = unsafe { slice::from_raw_parts_mut(buf, size as usize) };
+        let callback = unsafe { &mut *(cb_state as *mut CallbackState<F>) };
+
+        callback.cb.take().unwrap()(pass_slice)
+    });
+
+    if let Ok(len) = result {
+        return len as c_int;
+    } else {
+        return 0;
+    }
+}