From a8a0d952293337544da4681f0c896052eafd9d0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20=C3=85dahl?= <jadahl@gmail.com>
Date: Fri, 5 Apr 2024 16:44:07 +0200
Subject: [PATCH] Add headless session files
It consists of a python script for running the session, and a systemd
system service template.
---
data/gnome-headless-session@.service | 6 +
data/meson.build | 4 +
utils/gdm-headless-login-session | 157 +++++++++++++++++++++++++++
utils/meson.build | 5 +
4 files changed, 172 insertions(+)
create mode 100644 data/gnome-headless-session@.service
create mode 100644 utils/gdm-headless-login-session
diff --git a/data/gnome-headless-session@.service b/data/gnome-headless-session@.service
new file mode 100644
index 000000000..269d16288
--- /dev/null
+++ b/data/gnome-headless-session@.service
@@ -0,0 +1,6 @@
+[Unit]
+Description=Headless desktop session
+
+[Service]
+ExecStart=/usr/libexec/gdm-headless-login-session --user=%i
+Restart=on-failure
diff --git a/data/meson.build b/data/meson.build
index 2211e98b5..2df07cd32 100644
--- a/data/meson.build
+++ b/data/meson.build
@@ -221,3 +221,7 @@ if get_option('gdm-xsession')
install_dir: gdmconfdir,
)
endif
+
+headless_session_service = install_data('gnome-headless-session@.service',
+ install_dir: systemd_systemunitdir,
+ )
diff --git a/utils/gdm-headless-login-session b/utils/gdm-headless-login-session
new file mode 100644
index 000000000..e108be523
--- /dev/null
+++ b/utils/gdm-headless-login-session
@@ -0,0 +1,157 @@
+#!/usr/bin/env python3
+
+import argparse
+import pam
+import pwd
+import os
+import signal
+import sys
+
+import gi
+gi.require_version('AccountsService', '1.0')
+from gi.repository import AccountsService, GLib
+
+def run_desktop_in_new_session(pam_environment, user, session_desktop, tty_input, tty_output):
+ keyfile = GLib.KeyFile()
+ keyfile.load_from_data_dirs(f'wayland-sessions/{session_desktop}.desktop',
+ GLib.KeyFileFlags.NONE)
+
+ try:
+ can_run_headless = keyfile.get_boolean(GLib.KEY_FILE_DESKTOP_GROUP,
+ 'X-GDM-CanRunHeadless')
+ except GLib.GError:
+ raise Exception(f"Session {session_desktop} can't run headlessly")
+
+ if not can_run_headless:
+ raise Exception(f"Session {session_desktop} can't run headlessly")
+
+ executable = keyfile.get_string(GLib.KEY_FILE_DESKTOP_GROUP,
+ GLib.KEY_FILE_DESKTOP_KEY_TRY_EXEC)
+ if GLib.find_program_in_path(executable) is None:
+ raise Exception(f"Invalid session {session_desktop}")
+
+ command = keyfile.get_string(GLib.KEY_FILE_DESKTOP_GROUP,
+ GLib.KEY_FILE_DESKTOP_KEY_EXEC)
+ [success, args] = GLib.shell_parse_argv(command)
+
+ pam_handle = pam.pam()
+
+ for key, value in pam_environment.items():
+ pam_handle.putenv(f'{key}={value}')
+
+ if not pam_handle.authenticate(user, '', service='gdm-autologin', call_end=False):
+ raise Exception("Authentication failed")
+
+ for key, value in pam_environment.items():
+ pam_handle.putenv(f'{key}={value}')
+
+ if pam_handle.open_session() != pam.PAM_SUCCESS:
+ raise Exception("Failed to open PAM session")
+
+ session_environment = os.environ.copy()
+ session_environment.update(pam_handle.getenvlist())
+
+ user_info = pwd.getpwnam(user)
+ uid = user_info.pw_uid
+ gid = user_info.pw_gid
+
+ old_tty_output = os.fdopen(os.dup(2), 'w')
+
+ pid = os.fork()
+ if pid == 0:
+ try:
+ os.setsid()
+ except OSError as e:
+ print(f"Could not create new pid session: {e}", file=old_tty_output)
+
+ try:
+ os.dup2(tty_input.fileno(), 0)
+ os.dup2(tty_output.fileno(), 1)
+ os.dup2(tty_output.fileno(), 2)
+ except OSError as e:
+ print(f"Could not set up standard i/o: {e}", file=old_tty_output)
+
+ try:
+ os.initgroups(user, gid)
+ os.setgid(gid)
+ os.setuid(uid);
+ except OSError as e:
+ print(f"Could not become user {user} (uid={uid}): {e}", file=old_tty_output)
+
+ try:
+ os.execvpe(args[0], args, session_environment)
+ except OSError as e:
+ print(f"Could not run program \"{' '.join(arguments)}\": {e}", file=old_tty_output)
+ os._exit(1)
+
+
+ def signal_handler(sig, frame):
+ os.kill(pid, sig)
+
+ signal.signal(signal.SIGTERM, signal_handler)
+
+ try:
+ (_, exit_code) = os.waitpid(pid, 0);
+ except KeyboardInterrupt:
+ os.kill(pid, signal.SIGTERM)
+ except OSError as e:
+ print(f"Could not wait for program to finish: {e}", file=old_tty_output)
+
+ if os.WIFEXITED(exit_code):
+ exit_code = os.WEXITSTATUS(exit_code)
+ else:
+ os.kill(os.getpid(), os.WTERMSIG(exit_code))
+ old_tty_output.close()
+
+ if pam_handle.close_session() != pam.PAM_SUCCESS:
+ raise Exception("Failed to close PAM session")
+
+ pam_handle.end()
+
+ return exit_code
+
+def wait_for_user_data(user):
+ main_context = GLib.MainContext.default()
+ while not user.is_loaded():
+ main_context.iteration(True)
+
+def main():
+ parser = argparse.ArgumentParser(description='Run a desktop session in a PAM session as a specified user.')
+ parser.add_argument('--user', help='Username for which to run the session')
+
+ args = parser.parse_args()
+
+ if args.user is None:
+ parser.print_usage()
+ sys.exit(1)
+
+ try:
+ tty_path = '/dev/null'
+
+ tty_input = open(tty_path, 'r')
+ tty_output = open(tty_path, 'w')
+ except OSError as e:
+ raise Exception(f"Error opening /dev/null as tty associated with VT {vt}: {e}")
+
+ user_manager = AccountsService.UserManager().get_default()
+ user = user_manager.get_user(args.user)
+ wait_for_user_data(user)
+ session_desktop = user.get_session()
+ if not session_desktop:
+ session_desktop = 'gnome'
+
+ pam_environment = {}
+ pam_environment['XDG_SESSION_TYPE'] = 'wayland'
+ pam_environment['XDG_SESSION_CLASS'] = 'user'
+ pam_environment['XDG_SESSION_DESKTOP'] = session_desktop
+
+ try:
+ result = run_desktop_in_new_session(pam_environment, args.user, session_desktop, tty_input, tty_output)
+ except Exception as e:
+ raise Exception(f"Error running desktop session \"{session_desktop}\": {e}")
+ tty_input.close()
+ tty_output.close()
+ sys.exit(result)
+
+if __name__ == '__main__':
+ main()
diff --git a/utils/meson.build b/utils/meson.build
index e4141fb13..57dd6519f 100644
--- a/utils/meson.build
+++ b/utils/meson.build
@@ -65,3 +65,8 @@ if distro != 'none'
install_dir: get_option('libexecdir'),
)
endif
+
+gdm_headless_login_session = install_data('gdm-headless-login-session',
+ install_mode: 'rwxr-xr-x',
+ install_dir: get_option('libexecdir'),
+ )
--
2.44.0