PoC RC

Author: youknowone

Modules/_base64/src/lib.rs

@@ -4,8 +4,9 @@ use std::mem::MaybeUninit;
 use std::ptr;
 use std::slice;
 
+use cpython_sys::_Py_DecRef;
+use cpython_sys::_Py_IncRef;
 use cpython_sys::METH_FASTCALL;
-use cpython_sys::Py_DecRef;
 use cpython_sys::Py_buffer;
 use cpython_sys::Py_ssize_t;
 use cpython_sys::PyBuffer_Release;
@@ -26,6 +27,78 @@ const PYBUF_SIMPLE: c_int = 0;
 const PAD_BYTE: u8 = b'=';
 const ENCODE_TABLE: [u8; 64] = *b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
+pub struct PyRc {
+    ptr: std::ptr::NonNull<PyObject>,
+}
+
+impl PyRc {
+    /// # Safety
+    /// `ptr` must be a valid pointer to a PyObject.
+    pub unsafe fn from_raw(ptr: *mut PyObject) -> Option<Self> {
+        let ptr = std::ptr::NonNull::new(ptr)?;
+        Some(Self { ptr })
+    }
+
+    pub fn into_non_null(zelf: Self) -> std::ptr::NonNull<PyObject> {
+        let ptr = zelf.ptr;
+        std::mem::forget(zelf);
+        ptr
+    }
+
+    pub fn into_raw(zelf: Self) -> *mut PyObject {
+        let ptr = zelf.ptr.as_ptr();
+        std::mem::forget(zelf);
+        ptr
+    }
+
+    pub fn as_raw(&self) -> *mut PyObject {
+        self.ptr.as_ptr()
+    }
+}
+
+impl AsRef<PyObject> for PyRc {
+    fn as_ref(&self) -> &PyObject {
+        unsafe { self.ptr.as_ref() }
+    }
+}
+
+impl AsMut<PyObject> for PyRc {
+    fn as_mut(&mut self) -> &mut PyObject {
+        unsafe { self.ptr.as_mut() }
+    }
+}
+
+impl std::ops::Deref for PyRc {
+    type Target = PyObject;
+
+    fn deref(&self) -> &Self::Target {
+        self.as_ref()
+    }
+}
+
+impl std::ops::DerefMut for PyRc {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.as_mut()
+    }
+}
+
+impl Clone for PyRc {
+    fn clone(&self) -> Self {
+        unsafe {
+            _Py_IncRef(self.ptr.as_ptr());
+        }
+        Self { ptr: self.ptr }
+    }
+}
+
+impl Drop for PyRc {
+    fn drop(&mut self) {
+        unsafe {
+            _Py_DecRef(self.ptr.as_ptr());
+        }
+    }
+}
+
 #[inline]
 fn encoded_output_len(input_len: usize) -> Option<usize> {
     input_len
@@ -135,12 +208,12 @@ pub unsafe extern "C" fn standard_b64encode(
 
     // Safe cast by Safety
     match standard_b64encode_impl(source) {
-        Ok(result) => result,
+        Ok(result) => PyRc::into_raw(result),
         Err(_) => ptr::null_mut(),
     }
 }
 
-fn standard_b64encode_impl(source: &PyObject) -> Result<*mut PyObject, ()> {
+fn standard_b64encode_impl(source: &PyObject) -> Result<PyRc, ()> {
     let buffer = match BorrowedBuffer::from_object(source) {
         Ok(buf) => buf,
         Err(_) => return Err(()),
@@ -174,16 +247,17 @@ fn standard_b64encode_impl(source: &PyObject) -> Result<*mut PyObject, ()> {
         return Err(());
     }
 
-    let result = unsafe { PyBytes_FromStringAndSize(ptr::null(), output_len as Py_ssize_t) };
-    if result.is_null() {
+    let Some(result) = (unsafe {
+        PyRc::from_raw(PyBytes_FromStringAndSize(
+            ptr::null(),
+            output_len as Py_ssize_t,
+        ))
+    }) else {
         return Err(());
-    }
+    };
 
-    let dest_ptr = unsafe { PyBytes_AsString(result) };
+    let dest_ptr = unsafe { PyBytes_AsString(result.as_raw()) };
     if dest_ptr.is_null() {
-        unsafe {
-            Py_DecRef(result);
-        }
         return Err(());
     }
     let dest = unsafe { slice::from_raw_parts_mut(dest_ptr.cast::<u8>(), output_len) };