Spawn processes as an unprivileged user by default, including connect…

…ion-checker

test/scripts/ssh-setup.sh

@@ -21,6 +21,9 @@ for file in test-runner connection-checker $APP_PACKAGE $PREVIOUS_APP $UI_RUNNER
     cp -f "$SCRIPT_DIR/$file" "$RUNNER_DIR"
 done
 
+# Unprivileged users need execute rights for connection checker
+chmod 551 "${RUNNER_DIR}/connection-checker"
+
 chown -R root "$RUNNER_DIR/"
 
 # Create service
@@ -69,11 +72,18 @@ function setup_macos {
 </plist>
 EOF
 
+    create_test_user_macos
+
     echo "Starting test runner service"
 
     launchctl load -w $RUNNER_PLIST_PATH
 }
 
+function create_test_user_macos {
+    echo "Adding test user account"
+    sysadminctl -addUser mole -fullName "Mole Molesson" -password mole
+}
+
 function setup_systemd {
     RUNNER_SERVICE_PATH="/etc/systemd/system/testrunner.service"
 
@@ -94,10 +104,18 @@ EOF
 
     semanage fcontext -a -t bin_t "$RUNNER_DIR/.*" &> /dev/null || true
 
+    create_test_user_linux
+
     systemctl enable testrunner.service
     systemctl start testrunner.service
 }
 
+function create_test_user_linux {
+    echo "Adding test user account"
+    useradd -m mole
+    echo "mole" | passwd mole --stdin
+}
+
 if [[ "$(uname -s)" == "Darwin" ]]; then
     setup_macos
     exit 0

test/test-runner/Cargo.toml

@@ -58,7 +58,7 @@ features = ["codec"]
 default-features = false
 
 [target.'cfg(unix)'.dependencies]
-nix = { workspace = true }
+nix = { workspace = true, features = ["user"] }
 
 [target.'cfg(target_os = "linux")'.dependencies]
 rs-release = "0.1.7"

test/test-runner/src/main.rs

@@ -386,11 +386,18 @@ impl Service for TestServer {
         }
 
         cmd.stderr(Stdio::piped());
+        cmd.kill_on_drop(true);
 
-        let mut child = cmd.kill_on_drop(true).spawn().map_err(|error| {
-            log::error!("Failed to spawn {}: {error}", opts.path);
-            test_rpc::Error::Syscall
-        })?;
+        // TODO: do not hardcode
+        let mut child = util::as_unprivileged("mole", || cmd.spawn())
+            .map_err(|error| {
+                log::error!("Failed to drop privileges: {error}");
+                test_rpc::Error::Syscall
+            })?
+            .map_err(|error| {
+                log::error!("Failed to spawn {}: {error}", opts.path);
+                test_rpc::Error::Syscall
+            })?;
 
         let pid = child
             .id()

test/test-runner/src/util.rs

@@ -21,3 +21,48 @@ impl<F: FnOnce() + Send> OnDrop<F> {
         }
     }
 }
+
+#[cfg(target_os = "windows")]
+pub fn as_unprivileged<T>(unpriv_user: &str, func: impl FnOnce() -> T) -> Result<T, nix::Error> {
+    // NOTE: no-op
+    let _ = unpriv_user;
+    Ok(func())
+}
+
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("Failed to get the specified user")]
+    GetUser(#[source] nix::Error),
+    #[error("The specified user was not found")]
+    MissingUser,
+}
+
+#[cfg(unix)]
+pub fn as_unprivileged<T>(unpriv_user: &str, func: impl FnOnce() -> T) -> Result<T, Error> {
+    let original_uid = nix::unistd::getuid();
+    let original_gid = nix::unistd::getgid();
+
+    let user = nix::unistd::User::from_name(unpriv_user)
+        .map_err(Error::GetUser)?
+        .ok_or(Error::MissingUser)?;
+    let uid = user.uid;
+    let gid = user.gid;
+
+    if let Err(error) = nix::unistd::setegid(gid) {
+        log::error!("Failed to set gid: {error}");
+    }
+    if let Err(error) = nix::unistd::seteuid(uid) {
+        log::error!("Failed to set uid: {error}");
+    }
+
+    let func_result = func();
+
+    if let Err(error) = nix::unistd::seteuid(original_uid) {
+        log::error!("Failed to restore uid: {error}");
+    }
+    if let Err(error) = nix::unistd::setegid(original_gid) {
+        log::error!("Failed to restore gid: {error}");
+    }
+
+    Ok(func_result)
+}