Merge pull request #37 from willox/ckey_override

add guest_override command

debug_server/Cargo.toml

@@ -18,6 +18,7 @@ serde = { version = "1.0.117", features = ["derive"] }
 bincode = "1.3.1"
 clap = "2.33.3"
 dmasm = { git = "https://github.com/willox/dmasm" }
+region = "2.2.0"
 
 [target.'cfg(windows)'.dependencies]
 winapi = { version = "0.3.9", features = ["winuser", "libloaderapi", "errhandlingapi"] }

debug_server/src/ckey_override.rs

@@ -0,0 +1,52 @@
+use region::Protection;
+use std::{ffi::CString, os::raw::c_char};
+
+use auxtools::*;
+
+static mut STRING_PTR: *mut *const c_char = std::ptr::null_mut();
+
+#[init(full)]
+fn ckey_override_init() -> Result<(), String> {
+	let byondcore = sigscan::Scanner::for_module(BYONDCORE).unwrap();
+
+	// This feature soft-fails
+	#[cfg(windows)]
+	if let Some(ptr) = byondcore.find(signature!(
+		"68 ?? ?? ?? ?? 50 E8 ?? ?? ?? ?? 83 C4 0C 8D 8D ?? ?? ?? ?? E8 ?? ?? ?? ?? 8B 85 ?? ?? ?? ??"
+	)) {
+		unsafe {
+			STRING_PTR = ptr.add(1) as *mut *const c_char;
+		}
+	}
+
+	Ok(())
+}
+
+#[derive(Debug)]
+pub enum Error {
+	UnsupportedByondVersion,
+	InvalidString,
+}
+
+pub fn override_guest_ckey(name: &str) -> Result<(), Error> {
+	unsafe {
+		if STRING_PTR.is_null() {
+			return Err(Error::UnsupportedByondVersion);
+		}
+	}
+
+	let name = name.replace('%', "%%");
+
+	let new_ptr = CString::new(name)
+		.map_err(|_| Error::InvalidString)?
+		.into_raw();
+
+	unsafe {
+		region::protect(STRING_PTR as *const u8, 4, Protection::READ_WRITE_EXECUTE).unwrap();
+
+		// Leak is fine
+		*STRING_PTR = new_ptr;
+	}
+
+	Ok(())
+}

debug_server/src/lib.rs

@@ -1,4 +1,5 @@
 mod assemble_env;
+mod ckey_override;
 mod disassemble_env;
 mod instruction_hooking;
 mod server;

debug_server/src/server.rs

@@ -129,7 +129,15 @@ impl Server {
 							.help("Id of the proc to disassemble (for when multiple procs are defined with the same path)")
 							.takes_value(true),
 					)
-		)
+			)
+			.subcommand(
+				App::new("guest_override")
+					.about("Override the CKey used by guest connections")
+					.arg(
+						Arg::with_name("ckey")
+							.takes_value(true),
+					)
+			)
 	}
 
 	pub fn connect(addr: &SocketAddr) -> std::io::Result<Server> {
@@ -743,6 +751,18 @@ impl Server {
 						}
 					}
 
+					("guest_override", Some(matches)) => match matches.value_of("ckey") {
+						Some(ckey) => match crate::ckey_override::override_guest_ckey(ckey) {
+							Ok(()) => "Success".to_owned(),
+
+							Err(e) => {
+								format!("Failed: {:?}", e)
+							}
+						},
+
+						None => "no ckey provided".to_owned(),
+					},
+
 					_ => "unknown command".to_owned(),
 				}
 			}