~mvo/click/native-dbus

/* Copyright (C) 2014 Canonical Ltd.
 * Author: Colin Watson <cjwatson@ubuntu.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 3 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/* The Click D-Bus service.  */

namespace Click {

[DBus (name = "com.ubuntu.Click")]
public class DBusService : Object, DBusInterface {
	private DBusConnection conn;
	private DBusProxy proxy_uid;

	public DBusService (DBusConnection conn) throws Error
	{
		this.conn = conn;
		proxy_uid = new DBusProxy.sync
			(conn,
			 DBusProxyFlags.DO_NOT_LOAD_PROPERTIES |
			 DBusProxyFlags.DO_NOT_CONNECT_SIGNALS,
			 null,
			 "org.freedesktop.DBus",
			 "/org/freedesktop/DBus",
			 "org.freedesktop.DBus");
	}

	private string
	get_connected_username (BusName sender) throws Error
	{
		var uid_reply = proxy_uid.call_sync
			("GetConnectionUnixUser", new Variant ("(s)", sender),
			 DBusCallFlags.NONE, -1);
		uint uid;
		uid_reply.get ("(u)", out uid);
		errno = 0;
		unowned Posix.Passwd pw = Posix.getpwuid (uid);
		if (pw == null)
			throw new DBusError.AUTHENTICATION
				("Cannot get password file entry for UID " +
				 "%d: %s", uid, strerror (errno));
		return pw.pw_name;
	}

	private void
	priv_drop_failure (string name) throws DBusError
	{
		throw new DBusError.DROP_PRIVS
			("Cannot drop privileges (%s): %s",
			 name, strerror (errno));
	}

	private void
	drop_privileges (string username) throws Error
	{
		if (Posix.geteuid () != 0)
			return;
		unowned Posix.Passwd pw = Posix.getpwnam (username);
		if (pw == null)
			throw new DBusError.DROP_PRIVS
				("Cannot get password file entry for user " +
				 "'%s': %s", username, strerror (errno));
		Posix.gid_t[] supp = {};
		Posix.setgrent ();
		unowned PosixExtra.Group? gr;
		while ((gr = PosixExtra.getgrent ()) != null) {
			foreach (unowned string member in gr.gr_mem) {
				if (member == username) {
					supp += gr.gr_gid;
					break;
				}
			}
		}
		Posix.endgrent ();
		if (PosixExtra.setgroups (supp.length, supp) < 0)
			priv_drop_failure ("setgroups");
		/* Portability note: this assumes that we have
		 * [gs]etres[gu]id, which is true on Linux but not
		 * necessarily elsewhere.  If you need to support something
		 * else, there are reasonably standard alternatives
		 * involving other similar calls; see e.g.
		 * gnulib/lib/idpriv-drop.c.
		 */
		if (PosixExtra.setresgid (pw.pw_gid, pw.pw_gid, pw.pw_gid) < 0)
			priv_drop_failure ("setresgid");
		if (PosixExtra.setresuid (pw.pw_uid, pw.pw_uid, pw.pw_uid) < 0)
			priv_drop_failure ("setresuid");
		{
			Posix.uid_t ruid, euid, suid;
			Posix.gid_t rgid, egid, sgid;
			assert (PosixExtra.getresuid (out ruid, out euid,
						      out suid) == 0 &&
				ruid == pw.pw_uid && euid == pw.pw_uid &&
				suid == pw.pw_uid);
			assert (PosixExtra.getresgid (out rgid, out egid,
						      out sgid) == 0 &&
				rgid == pw.pw_gid && egid == pw.pw_gid &&
				sgid == pw.pw_gid);
		}
		Posix.umask (get_umask () | Posix.S_IWOTH);
	}

	private bool
	euid_access (string username, string path, int mode) throws Error
	{
		var pid = Posix.fork ();
		if (pid < 0)
			throw new DBusError.DROP_PRIVS
				("Cannot fork: %s", strerror (errno));
		else if (pid == 0) {	/* child */
			drop_privileges (username);
			Posix._exit (Posix.access (path, mode) == 0 ? 0 : 1);
			throw new DBusError.DROP_PRIVS ("Unreachable");
		} else {		/* parent */
			int status;
			if (Posix.waitpid (pid, out status, 0) < 0)
				throw new DBusError.DROP_PRIVS
					("Cannot wait for privilege-dropped " +
					 "subprocess: %s", strerror (errno));
			return status == 0;
		}
	}

	private Json.Object
	get_manifest (string filename) throws Error
	{
		string[] command = {"click", "info", filename};
		string manifest_text;
		string click_stderr;
		int click_status;
		Process.spawn_sync
			(null, command, null, SpawnFlags.SEARCH_PATH, null,
			 out manifest_text, out click_stderr,
			 out click_status);
		try {
			Process.check_exit_status (click_status);
		} catch (Error e) {
			throw new DBusError.MANIFEST
				("\"click info %s\" failed.\n%s",
				 filename, click_stderr);
		}

		var parser = new Json.Parser ();
		parser.load_from_data (manifest_text);
		return parser.get_root ().get_object ();
	}

	private string?
	get_field_string (Json.Object manifest, string field)
	{
		var node = manifest.get_member (field);
		return node != null ? node.dup_string () : null;
	}

	private Json.Object?
	get_field_object (Json.Object manifest, string field)
	{
		var node = manifest.get_member (field);
		return node != null ? node.dup_object () : null;
	}

	private bool
	get_field_boolean (Json.Object manifest, string field, bool def)
	{
		var node = manifest.get_member (field);
		return node != null ? node.get_boolean () : def;
	}

	private void
	installed_manifest (Json.Object manifest, string username,
			    out string package, out string version,
			    ref HashTable<string, Variant> details)
	{
		package = get_field_string (manifest, "name");
		version = get_field_string (manifest, "version");
		if (package == null || version == null)
			return;
		var architecture = get_field_string (manifest, "architecture");
		if (architecture != null)
			details["architecture"] = architecture;
		/* A missing "_removable" entry in the manifest means that
		 * we just installed the package, so it must be removable.
		 */
		details["removable"] = get_field_boolean
			(manifest, "_removable", true);
		string[] app_names = {};
		var hooks = get_field_object (manifest, "hooks");
		if (hooks != null) {
			foreach (var app_name in hooks.get_members ())
				app_names += app_name;
			details["app_names"] = app_names;
		}
	}

	public void
	install_file (string filename, InstallFlags flags,
		      out string package, out string version,
		      out HashTable<string, Variant> details,
		      BusName sender)
		throws Error
	{
		var username = get_connected_username (sender);
		message (@"Click: installing $filename for $username");
		if (! euid_access (username, filename, Posix.R_OK))
			throw new DBusError.FAILED_TO_INSTALL
				("User %s cannot read %s", username, filename);
		string[] command = {"click", "install", @"--user=$username"};
		if (InstallFlags.FORCE_MISSING_FRAMEWORK in flags)
			command += "--force-missing-framework";
		if (InstallFlags.ALLOW_UNAUTHENTICATED in flags)
			command += "--allow-unauthenticated";
		command += filename;
		string click_stderr;
		int click_status;
		Process.spawn_sync
			(null, command, null,
			 SpawnFlags.SEARCH_PATH |
			 SpawnFlags.STDOUT_TO_DEV_NULL,
			 null, null, out click_stderr, out click_status);
		try {
			Process.check_exit_status (click_status);
		} catch (Error e) {
			throw new DBusError.FAILED_TO_INSTALL
				("%s failed to install.\n%s",
				 filename, click_stderr);
		}
		package = "";
		version = "";
		details = new HashTable<string, Variant> (str_hash, str_equal);
		try {
			installed_manifest
				(get_manifest (filename), username,
				 out package, out version, ref details);
		} catch (Error e) {
			stderr.printf ("Failed to get installed package " +
				       "manifest: %s", e.message);
		}
	}

	public void
	remove_package (string package, string version, BusName sender)
		throws Error
	{
		var username = get_connected_username (sender);
		message (@"Click: removing $package $version for $username");
		var db = new Click.DB ();
		db.read ();
		var registry = new Click.User.for_user (db, username);
		var old_version = registry.get_version (package);
		if (old_version != version) {
			throw new DBusError.FAILED_TO_REMOVE
				("Not removing Click package %s %s; " +
				 "does not match current version %s.",
				 package, version, old_version);
		}
		registry.remove (package);
		db.maybe_remove (package, version);
		/* TODO: remove data? */
	}

	private static void
	on_bus_acquired (DBusConnection conn)
	{
		try {
			conn.register_object
				("/com/ubuntu/Click", new DBusService (conn));
		} catch (Error e) {
			stderr.printf ("Could not register service: %s\n",
				       e.message);
			Process.exit (Posix.EXIT_FAILURE);
		}
	}

	static void
	main ()
	{
		Environment.set_variable ("CLICK_IN_DBUS_SERVICE", "1", true);
		Bus.own_name
			(BusType.SYSTEM, "com.ubuntu.Click",
			 BusNameOwnerFlags.NONE, on_bus_acquired, () => {},
			 () => stderr.printf ("Could not acquire name\n"));
		new MainLoop ().run ();
	}
}

}