fix(linux/xdgportal): allow unified systemd service for all capture methods (#4854)

cmake/FindSystemd.cmake

@@ -19,11 +19,6 @@ IF (NOT WIN32)
             OUTPUT_STRIP_TRAILING_WHITESPACE
             OUTPUT_VARIABLE SYSTEMD_USER_UNIT_INSTALL_DIR)
 
-        execute_process(COMMAND ${PKG_CONFIG_EXECUTABLE}
-            --variable=systemd_user_preset_dir systemd
-            OUTPUT_STRIP_TRAILING_WHITESPACE
-            OUTPUT_VARIABLE SYSTEMD_USER_PRESET_INSTALL_DIR)
-
         execute_process(COMMAND ${PKG_CONFIG_EXECUTABLE}
             --variable=systemd_system_unit_dir systemd
             OUTPUT_STRIP_TRAILING_WHITESPACE
@@ -36,7 +31,6 @@ IF (NOT WIN32)
 
         mark_as_advanced(
                 SYSTEMD_USER_UNIT_INSTALL_DIR
-                SYSTEMD_USER_PRESET_INSTALL_DIR
                 SYSTEMD_SYSTEM_UNIT_INSTALL_DIR
                 SYSTEMD_MODULES_LOAD_DIR
         )

cmake/packaging/linux.cmake

@@ -18,10 +18,6 @@ if(${SUNSHINE_BUILD_APPIMAGE} OR ${SUNSHINE_BUILD_FLATPAK})
             DESTINATION "${SUNSHINE_ASSETS_DIR}/modules-load.d")
     install(FILES "${CMAKE_CURRENT_BINARY_DIR}/app-${PROJECT_FQDN}.service"
             DESTINATION "${SUNSHINE_ASSETS_DIR}/systemd/user")
-    install(FILES "${CMAKE_CURRENT_BINARY_DIR}/sunshine.service"
-            DESTINATION "${SUNSHINE_ASSETS_DIR}/systemd/user")
-    install(FILES "${CMAKE_CURRENT_BINARY_DIR}/00-app-${PROJECT_FQDN}.preset"
-            DESTINATION "${SUNSHINE_ASSETS_DIR}/systemd/user-preset")
 else()
     find_package(Systemd)
     find_package(Udev)
@@ -33,10 +29,6 @@ else()
     if(SYSTEMD_FOUND)
         install(FILES "${CMAKE_CURRENT_BINARY_DIR}/app-${PROJECT_FQDN}.service"
                 DESTINATION "${SYSTEMD_USER_UNIT_INSTALL_DIR}")
-        install(FILES "${CMAKE_CURRENT_BINARY_DIR}/sunshine.service"
-                DESTINATION "${SYSTEMD_USER_UNIT_INSTALL_DIR}")
-        install(FILES "${CMAKE_CURRENT_BINARY_DIR}/00-app-${PROJECT_FQDN}.preset"
-                DESTINATION "${SYSTEMD_USER_PRESET_INSTALL_DIR}")
         install(FILES "${SUNSHINE_SOURCE_ASSETS_DIR}/linux/misc/60-sunshine.conf"
                 DESTINATION "${SYSTEMD_MODULES_LOAD_DIR}")
     endif()

cmake/prep/special_package_configuration.cmake

@@ -25,8 +25,6 @@ elseif(UNIX)
 
     # configure service
     configure_file(packaging/linux/app-${PROJECT_FQDN}.service.in app-${PROJECT_FQDN}.service @ONLY)
-    configure_file(packaging/linux/sunshine.service.in sunshine.service @ONLY)
-    configure_file(packaging/linux/00-app-${PROJECT_FQDN}.preset.in 00-app-${PROJECT_FQDN}.preset @ONLY)
 
     # configure the arch linux pkgbuild
     if(${SUNSHINE_CONFIGURE_PKGBUILD})

docs/getting_started.md

@@ -447,21 +447,20 @@ After adding yourself to the group, log out and log back in for the changes to t
 
 #### Services
 
-> [!NOTE]
-> Two service unit files are available. Pick "app-dev.lizardbyte.app.Sunshine" for unprivileged XDG Portal
-> or X11 capture, otherwise pick "sunshine" for privileged KMS capture.
-
 **Start once**
 ```bash
-systemctl --user start sunshine
+systemctl --user start app-dev.lizardbyte.app.Sunshine
 ```
 
-**Start on boot (privileged; swap names for unprivileged XDG capture)**
+**Start on boot**
 ```bash
-systemctl --user --now disable app-dev.lizardbyte.app.Sunshine
+systemctl --user --now enable app-dev.lizardbyte.app.Sunshine
-systemctl --user --now enable sunshine
 ```
 
+> [!NOTE]
+> The service has been renamed to "app-dev.lizardbyte.app.Sunshine" in order to increase compatibility with
+> XDG Desktop Portal, but it is also aliased to "sunshine.service" for convenience.
+
 ### macOS
 The first time you start Sunshine, you will be asked to grant access to screen recording and your microphone.
 

docs/troubleshooting.md

@@ -160,18 +160,21 @@ sudo usermod -aG input $USER
 ```
 
 ### KMS Streaming fails
-If screencasting fails with KMS, you may be using the unprivileged app-dev.lizardbyte.app.Sunshine service unit.
+KMS screencasting requires elevated privileges which are not allowed for Flatpak or AppImage packages.
-Switch to the privileged sunshine service:
+This means that you must install Sunshine using the native package format of your distribution, if available.
+KMS capture will soon be phased out in favour of XDG Portal Capture (which works with all package types).
+
+### KMS Streaming; some windows flicker/disappear on KDE Plasma 6.5+
+KWin's overlay support interferes with KMS capture. As of KWin 6.5 this is not yet set by default, but
+for future versions that enables this by default, you may be able to disable again via a special
+[environment variable](https://invent.kde.org/plasma/kwin/-/wikis/Environment-Variables#kwin_use_overlays):
 
 ```bash
-systemctl --user --now disable app-dev.lizardbyte.app.Sunshine
+export KWIN_USE_OVERLAYS=0
-systemctl --user --now enable sunshine
 ```
 
 > [!NOTE]
-> The above commands will not work with the AppImage or Flatpak packages, as KMS screencasting
+> Disabling overlays will reduce KWin's rendering efficiency. Consider using XDG Portal Capture instead.
-> requires elevated privileges which are not allowed by their respective packaging security policies.
-> As an alternative, XDG Portal capture is recommended.
 
 ### KMS streaming fails on Nvidia GPUs
 If KMS screen capture results in a black screen being streamed, you may need to

packaging/linux/00-app-dev.lizardbyte.app.Sunshine.preset.in

@@ -1,4 +0,0 @@
-# @PROJECT_DESCRIPTION@
-# The unprivileged service should preset to disabled
-
-disable app-@PROJECT_FQDN@.service

packaging/linux/app-dev.lizardbyte.app.Sunshine.service.in

@@ -2,7 +2,6 @@
 Description=@PROJECT_DESCRIPTION@
 StartLimitIntervalSec=500
 StartLimitBurst=5
-Conflicts=sunshine.service
 After=graphical-session.target xdg-desktop-autostart.target xdg-desktop-portal.service
 
 [Service]
@@ -12,7 +11,7 @@ ExecStartPre=/bin/sleep 5
 @SUNSHINE_SERVICE_STOP_COMMAND@
 Restart=on-failure
 RestartSec=5s
-NoNewPrivileges=true
 
 [Install]
 WantedBy=graphical-session.target
+Alias=sunshine.service

packaging/linux/copr/Sunshine.spec

@@ -390,9 +390,8 @@ fi
 %caps(cap_sys_admin+p) %{_bindir}/sunshine
 %caps(cap_sys_admin+p) %{_bindir}/sunshine-*
 
-# Systemd unit/preset files for user services
+# Systemd unit files for user services
 %{_userunitdir}/*.service
-%{_userpresetdir}/*.preset
 
 # Udev rules
 %{_udevrulesdir}/*-sunshine.rules

packaging/linux/sunshine.service.in

@@ -1,17 +0,0 @@
-[Unit]
-Description=@PROJECT_DESCRIPTION@
-StartLimitIntervalSec=500
-StartLimitBurst=5
-Conflicts=app-@PROJECT_FQDN@.service
-After=graphical-session.target xdg-desktop-autostart.target
-
-[Service]
-# Avoid starting Sunshine before the desktop is fully initialized.
-ExecStartPre=/bin/sleep 5
-@SUNSHINE_SERVICE_START_COMMAND@
-@SUNSHINE_SERVICE_STOP_COMMAND@
-Restart=on-failure
-RestartSec=5s
-
-[Install]
-WantedBy=graphical-session.target

src/platform/linux/kmsgrab.cpp

@@ -1684,17 +1684,6 @@ namespace platf {
 #if defined(SUNSHINE_BUILD_FLATPAK) || defined(SUNSHINE_BUILD_APPIMAGE)
           BOOST_LOG((config::video.capture == "kms") ? fatal : error)
             << "AppImage and Flatpak do not support KMS capture. Use another capture method."sv;
-#else
-          {
-            const std::string kms_msg =
-              "You must use the 'sunshine' service instead of the 'app-" +
-              std::string(PROJECT_FQDN) +
-              "' service for KMS capture.\n"
-              "Please refer to the official documentation:\n"
-              "  stable: https://docs.lizardbyte.dev/projects/sunshine/latest/md_docs_2getting__started.html#linux-1\n"
-              "  beta: https://docs.lizardbyte.dev/projects/sunshine/master/md_docs_2getting__started.html#linux-1";
-            BOOST_LOG((config::video.capture == "kms") ? fatal : error) << kms_msg;
-          }
 #endif
           break;
         }

src/platform/linux/portalgrab.cpp

@@ -31,6 +31,12 @@
 #include "vaapi.h"
 #include "wayland.h"
 
+#if !defined(__FreeBSD__)
+  // platform includes
+  #include <sys/capability.h>
+  #include <sys/prctl.h>
+#endif
+
 namespace {
   // Buffer and limit constants
   constexpr int SPA_POD_BUFFER_SIZE = 4096;
@@ -223,12 +229,43 @@ namespace portal {
       return 0;
     }
 
+    void finalize_portal_security() {
+#if !defined(__FreeBSD__)
+      BOOST_LOG(debug) << "Finalizing Portal security: dropping CAP_SYS_ADMIN and resetting dumpable"sv;
+
+      cap_t caps = cap_get_proc();
+      if (!caps) {
+        BOOST_LOG(error) << "Failed to get process capabilities"sv;
+        return;
+      }
+
+      std::array<cap_value_t, 1> remove_list {CAP_SYS_ADMIN};
+
+      cap_set_flag(caps, CAP_PERMITTED, remove_list.size(), remove_list.data(), CAP_CLEAR);
+      cap_set_flag(caps, CAP_EFFECTIVE, remove_list.size(), remove_list.data(), CAP_CLEAR);
+
+      if (cap_set_proc(caps) != 0) {
+        BOOST_LOG(error) << "Failed to prune capabilities: "sv << std::strerror(errno);
+      }
+      cap_free(caps);
+
+      // Reset dumpable AFTER the caps have been pruned to ensure the Portal can
+      // access /proc/pid/root.
+      if (prctl(PR_SET_DUMPABLE, 1) != 0) {
+        BOOST_LOG(error) << "Failed to set PR_SET_DUMPABLE: "sv << std::strerror(errno);
+      }
+#endif
+    }
+
     int connect_to_portal() {
       g_autoptr(GMainLoop) loop = g_main_loop_new(nullptr, FALSE);
       g_autofree gchar *session_path = nullptr;
       g_autofree gchar *session_token = nullptr;
       create_session_path(conn, nullptr, &session_token);
 
+      // Drop CAP_SYS_ADMIN and set DUMPABLE flag to allow XDG /root access
+      finalize_portal_security();
+
       // Try combined RemoteDesktop + ScreenCast session first
       bool use_screencast_only = !try_remote_desktop_session(loop, &session_path, session_token);