Support custom wintun.dll paths (#73)

Author: blechschmidt

.gitignore

@@ -6,4 +6,3 @@ target/
 **/*.rs.bk
 Cargo.lock
 wintun.dll
-.history

Cargo.toml

@@ -30,7 +30,7 @@ nix = { version = "0.29", features = ["ioctl"] }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 wintun = { version = "0.4", features = ["panic_on_unsent_packets"] }
-libloading = "0.8.3"
+libloading = "0.8"
 
 [target.'cfg(any(target_os = "macos", target_os = "freebsd"))'.dependencies]
 ipnet = "2"

README.md

@@ -135,5 +135,4 @@ pub extern "C" fn start_tun(fd: std::os::raw::c_int) {
 Windows
 -----
 You need to copy the [wintun.dll](https://wintun.net/) file which matches your architecture to 
-the same directory as your executable or can set `WINTUN_LIBARAY_PATH` to the dll file and run your program as administrator.
-
+the same directory as your executable and run your program as administrator.

src/platform/windows/device.rs

@@ -31,10 +31,12 @@ pub struct Device {
 impl Device {
     /// Create a new `Device` for the given `Configuration`.
     pub fn new(config: &Configuration) -> Result<Self> {
+        let wintun_path = match &config.platform_config.wintun_path {
+            Some(path) => path.clone(),
+            None => "wintun.dll".to_string(),
+        };
         let wintun = unsafe {
-            let wintun_libray_path =
-                std::env::var("WINTUN_LIBARAY_PATH").unwrap_or("wintun.dll".to_string());
-            let wintun = libloading::Library::new(wintun_libray_path)?;
+            let wintun = libloading::Library::new(wintun_path)?;
             wintun::load_from_library(wintun)?
         };
         let tun_name = config.tun_name.as_deref().unwrap_or("wintun");

src/platform/windows/mod.rs

@@ -22,16 +22,24 @@ use crate::configuration::Configuration;
 use crate::error::Result;
 
 /// Windows-only interface configuration.
-#[derive(Copy, Clone, Default, Debug)]
+#[derive(Clone, Default, Debug)]
 pub struct PlatformConfig {
     pub(crate) device_guid: Option<u128>,
+    pub(crate) wintun_path: Option<String>,
 }
 
 impl PlatformConfig {
     pub fn device_guid(&mut self, device_guid: Option<u128>) {
         log::trace!("Windows configuration device GUID");
         self.device_guid = device_guid;
     }
+
+    /// Use a custom path to the wintun.dll instead of looking in the working directory.
+    /// Security note: It is up to the caller to ensure that the library can be safely loaded from
+    /// the indicated path.
+    pub fn custom_wintun_path(&mut self, wintun_path: Option<String>) {
+        self.wintun_path = wintun_path;
+    }
 }
 
 /// Create a TUN device with the given name.