From 53ada31d748476701d7f704c884f0e40a708d826 Mon Sep 17 00:00:00 2001
From: Julian Orth <ju.orth@gmail.com>
Date: Wed, 24 Jul 2024 17:55:54 +0200
Subject: [PATCH] xwayland: disable direct libei access

---
 src/config/handler.rs |  1 +
 src/forker.rs         | 25 ++++++++++++++--------
 src/xwayland.rs       | 48 +++++++++++++++++++++++++++++++++++++++----
 3 files changed, 61 insertions(+), 13 deletions(-)

diff --git a/src/config/handler.rs b/src/config/handler.rs
index 905af050..a21fcea9 100644
--- a/src/config/handler.rs
+++ b/src/config/handler.rs
@@ -1300,6 +1300,7 @@ impl ConfigProxyHandler {
             Some(f) => f,
             _ => return Err(CphError::NoForker),
         };
+        let env = env.into_iter().map(|(k, v)| (k, Some(v))).collect();
         forker.spawn(prog.to_string(), args, env, fds);
         Ok(())
     }
diff --git a/src/forker.rs b/src/forker.rs
index 0067198d..3d6a3508 100644
--- a/src/forker.rs
+++ b/src/forker.rs
@@ -3,7 +3,7 @@ mod io;
 use {
     crate::{
         async_engine::{AsyncEngine, SpawnedFuture},
-        compositor::{DISPLAY, WAYLAND_DISPLAY},
+        compositor::{DISPLAY, LIBEI_SOCKET, WAYLAND_DISPLAY},
         forker::io::{IoIn, IoOut},
         io_uring::IoUring,
         state::State,
@@ -151,14 +151,18 @@ impl ForkerProxy {
 
     pub async fn xwayland(
         &self,
+        state: &State,
         stderr: Rc<OwnedFd>,
         dfd: Rc<OwnedFd>,
         listenfd: Rc<OwnedFd>,
         wmfd: Rc<OwnedFd>,
         waylandfd: Rc<OwnedFd>,
     ) -> Result<(Rc<OwnedFd>, c::pid_t), ForkerError> {
-        let (prog, args) = xwayland::build_args();
-        let env = vec![("WAYLAND_SOCKET".to_string(), "6".to_string())];
+        let (prog, args) = xwayland::build_args(state, self).await;
+        let env = vec![
+            ("WAYLAND_SOCKET".to_string(), Some("6".to_string())),
+            (LIBEI_SOCKET.to_string(), None),
+        ];
         let fds = vec![
             (2, stderr),
             (3, dfd),
@@ -175,7 +179,7 @@ impl ForkerProxy {
         &self,
         prog: String,
         args: Vec<String>,
-        env: Vec<(String, String)>,
+        env: Vec<(String, Option<String>)>,
         fds: Vec<(i32, Rc<OwnedFd>)>,
     ) {
         self.spawn_(prog, args, env, fds, None)
@@ -185,7 +189,7 @@ impl ForkerProxy {
         &self,
         prog: String,
         args: Vec<String>,
-        env: Vec<(String, String)>,
+        env: Vec<(String, Option<String>)>,
         fds: Vec<(i32, Rc<OwnedFd>)>,
         pidfd_id: Option<u32>,
     ) {
@@ -291,7 +295,7 @@ enum ServerMessage {
     Spawn {
         prog: String,
         args: Vec<String>,
-        env: Vec<(String, String)>,
+        env: Vec<(String, Option<String>)>,
         fds: Vec<i32>,
         pidfd_id: Option<u32>,
     },
@@ -408,7 +412,7 @@ impl Forker {
         self: &Rc<Self>,
         prog: String,
         args: Vec<String>,
-        env: Vec<(String, String)>,
+        env: Vec<(String, Option<String>)>,
         fds: Vec<i32>,
         io: &mut IoIn,
         pidfd_id: Option<u32>,
@@ -424,7 +428,7 @@ impl Forker {
         self: &Rc<Self>,
         prog: String,
         args: Vec<String>,
-        env: Vec<(String, String)>,
+        env: Vec<(String, Option<String>)>,
         fds: Vec<(i32, OwnedFd)>,
         pidfd_id: Option<u32>,
     ) {
@@ -502,7 +506,10 @@ impl Forker {
                         c::signal(c::SIGCHLD, c::SIG_DFL);
                     }
                     for (key, val) in env {
-                        env::set_var(&key, &val);
+                        match val {
+                            None => env::remove_var(&key),
+                            Some(val) => env::set_var(&key, &val),
+                        }
                     }
                     let prog = prog.into_ustr();
                     let mut argsnt = UstrPtr::new();
diff --git a/src/xwayland.rs b/src/xwayland.rs
index 7b11d972..bd2e1d6a 100644
--- a/src/xwayland.rs
+++ b/src/xwayland.rs
@@ -14,7 +14,7 @@ use {
         io_uring::IoUringError,
         state::State,
         user_session::import_environment,
-        utils::{errorfmt::ErrorFmt, line_logger::log_lines, oserror::OsError},
+        utils::{buf::Buf, errorfmt::ErrorFmt, line_logger::log_lines, oserror::OsError},
         wire::WlSurfaceId,
         xcon::XconError,
         xwayland::{
@@ -153,6 +153,7 @@ async fn run(
     let stderr_read = state.eng.spawn(log_xwayland(state.clone(), stderr_read));
     let pidfd = forker
         .xwayland(
+            &state,
             Rc::new(stderr_write),
             Rc::new(dfdwrite),
             socket,
@@ -195,9 +196,12 @@ async fn run(
     Ok(())
 }
 
-pub fn build_args() -> (String, Vec<String>) {
-    let prog = "Xwayland".to_string();
-    let args = vec![
+const PROG: &str = "Xwayland";
+const ENABLE_EI_PORTAL: &str = "-enable-ei-portal";
+
+pub async fn build_args(state: &State, forker: &ForkerProxy) -> (String, Vec<String>) {
+    let prog = PROG.to_string();
+    let mut args = vec![
         "-terminate".to_string(),
         "-rootless".to_string(),
         "-verbose".to_string(),
@@ -209,9 +213,45 @@ pub fn build_args() -> (String, Vec<String>) {
         "-wm".to_string(),
         "5".to_string(),
     ];
+    let features = detect_features(state, forker).await;
+    if features.ei_portal {
+        args.push(ENABLE_EI_PORTAL.to_string());
+    }
     (prog, args)
 }
 
+#[derive(Default, Debug)]
+struct XwaylandFeatures {
+    ei_portal: bool,
+}
+
+async fn detect_features(state: &State, forker: &ForkerProxy) -> XwaylandFeatures {
+    let mut features = Default::default();
+    let Ok((read, write)) = pipe2(c::O_CLOEXEC) else {
+        return features;
+    };
+    forker.spawn(
+        PROG.to_string(),
+        vec!["-help".to_string()],
+        vec![],
+        vec![(2, Rc::new(write))],
+    );
+    let read = Rc::new(read);
+    let mut help = Vec::new();
+    let mut buf = Buf::new(1024);
+    loop {
+        match state.ring.read(&read, buf.clone()).await {
+            Ok(0) => break,
+            Ok(n) => help.extend_from_slice(&buf[..n]),
+            Err(_) => return features,
+        }
+    }
+    if help.as_bstr().contains_str(ENABLE_EI_PORTAL) {
+        features.ei_portal = true;
+    }
+    features
+}
+
 async fn log_xwayland(state: Rc<State>, stderr: OwnedFd) {
     let stderr = Rc::new(stderr);
     let res = log_lines(&state.ring, &stderr, |left, right| {