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#[derive(Debug)]
#[repr(C)]
pub struct CppClass {
pub vtable: *const CppClassVTable,
/* other fields... */
}
impl Default for CppClass {
fn default() -> Self {
static VTABLE: CppClassVTable = CppClassVTable {
foo: foo_bar_original,
bar: foo_bar_original,
};
Self { vtable: &VTABLE }
}
}
#[derive(Debug)]
#[repr(C)]
pub struct CppClassVTable {
pub foo: unsafe extern "system" fn(thisptr: *const CppClass) -> std::os::raw::c_int,
pub bar: unsafe extern "system" fn(thisptr: *const CppClass) -> std::os::raw::c_int,
/* other methods... */
}
unsafe extern "system" fn foo_bar_original(_thisptr: *const CppClass) -> std::os::raw::c_int {
0
}
unsafe extern "system" fn bar_hooked(_thisptr: *const CppClass) -> std::os::raw::c_int {
1
}
fn main() {
unsafe {
/* The same classes, but one is our victim, and the other is unaffected. */
let mut victim_cpp_class = CppClass::default();
let unaffected_cpp_class = CppClass::default();
/* If you can, use Hook over RawHook. It uses Rust's lifetime system
* to force victim_cpp_class to stay valid while hook is set because
* you can't drop victim_cpp_class while its being borrowed inside
* copy::Hook */
{
/* Setting up hook */
/* To get VTable size you can use multiple methods:
* Calculate it on runtime by passing None as methods_count arg inside Hook::new() (very unsafe!)
* If your VTable struct implementation is 100% valid, you can use
* std::mem::size_of::<VTableStruct>() / std::mem::size_of::<usize>() to get
* methods count at compile time, or just specify it manually: Some(2) */
let vtable_size = std::mem::size_of::<CppClassVTable>() / std::mem::size_of::<usize>();
let mut hook =
vtable_hook::hook::copy::Hook::new(&mut victim_cpp_class, None, Some(vtable_size));
eprintln!("Hook: {hook:#?}");
/* Since we are mutually borrowing victim_cpp_class in hook we can't use it directly
* but we can use hook's reference instead:
* &hook.item */
/* Hooks are unset now, let's test that its true */
eprintln!("-- Hook is disabled -- ");
eprintln!("victim_cpp_class's hook is_enabled {}", hook.is_enabled());
{
let victim_cpp_class = &hook.item;
eprintln!(
"victim_cpp_class bar() result = {}",
(victim_cpp_class.vtable.read().bar)(*victim_cpp_class)
);
}
eprintln!(
"unaffected_cpp_class bar() result = {}",
(unaffected_cpp_class.vtable.read().bar)(&unaffected_cpp_class)
);
/* victim_cpp_class's hook is_enabled false
* victim_cpp_class bar() result = 0
* unaffected_cpp_class bar() result = 0 */
/* Replacing bar inside raw_hook */
hook.replace_method(1, bar_hooked as _);
/* Replacing victim_cpp_class's VTable */
hook.enable();
/* Testing */
eprintln!("-- Hook is enabled -- ");
eprintln!("victim_cpp_class's hook is_enabled {}", hook.is_enabled());
{
let victim_cpp_class = &hook.item;
eprintln!(
"victim_cpp_class bar() result = {}",
(victim_cpp_class.vtable.read().bar)(*victim_cpp_class)
);
}
eprintln!(
"unaffected_cpp_class bar() result = {}",
(unaffected_cpp_class.vtable.read().bar)(&unaffected_cpp_class)
);
/* victim_cpp_class's hook is_enabled true
* victim_cpp_class bar() result = 1
* unaffected_cpp_class bar() result = 0 */
/* hook will disable itself on drop() */
}
eprintln!("-- Hook is disabled (drop) -- ");
eprintln!(
"victim_cpp_class bar() result = {}",
(victim_cpp_class.vtable.read().bar)(&victim_cpp_class)
);
eprintln!(
"unaffected_cpp_class bar() result = {}",
(unaffected_cpp_class.vtable.read().bar)(&unaffected_cpp_class)
);
/* victim_cpp_class bar() result = 0
* unaffected_cpp_class bar() result = 0 */
}
}