Start Cage 0.2 rewrite

cageng.c

@@ -0,0 +1,328 @@
+/*
+ * Cage: A Wayland kiosk.
+ *
+ * Copyright (C) 2018-2020 Jente Hidskes
+ *
+ * See the LICENSE file accompanying this file.
+ */
+
+#define _POSIX_C_SOURCE 200112L
+
+#include "config.h"
+
+#include <fcntl.h>
+#include <getopt.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <wayland-server-core.h>
+#include <wlr/backend.h>
+#include <wlr/render/wlr_renderer.h>
+#include <wlr/types/wlr_compositor.h>
+#include <wlr/util/log.h>
+
+#include "desktop/output.h"
+#include "serverng.h"
+
+static int
+sigchld_handler(int fd, uint32_t mask, void *user_data)
+{
+	struct wl_display *display = user_data;
+
+	/* Close Cage's read pipe. */
+	close(fd);
+
+	if (mask & WL_EVENT_HANGUP) {
+		wlr_log(WLR_DEBUG, "Child process closed normally");
+	} else if (mask & WL_EVENT_ERROR) {
+		wlr_log(WLR_DEBUG, "Connection closed by server");
+	}
+
+	wl_display_terminate(display);
+	return 0;
+}
+
+static bool
+set_cloexec(int fd)
+{
+	int flags = fcntl(fd, F_GETFD);
+
+	if (flags == -1) {
+		wlr_log(WLR_ERROR, "Unable to set the CLOEXEC flag: fnctl failed");
+		return false;
+	}
+
+	flags = flags | FD_CLOEXEC;
+	if (fcntl(fd, F_SETFD, flags) == -1) {
+		wlr_log(WLR_ERROR, "Unable to set the CLOEXEC flag: fnctl failed");
+		return false;
+	}
+
+	return true;
+}
+
+static bool
+spawn_primary_client(struct wl_display *display, char *argv[], pid_t *pid_out, struct wl_event_source **sigchld_source)
+{
+	int fd[2];
+	if (pipe(fd) != 0) {
+		wlr_log(WLR_ERROR, "Unable to create pipe");
+		return false;
+	}
+
+	pid_t pid = fork();
+	if (pid == 0) {
+		sigset_t set;
+		sigemptyset(&set);
+		sigprocmask(SIG_SETMASK, &set, NULL);
+		/* Close read, we only need write in the primary client process. */
+		close(fd[0]);
+		execvp(argv[0], argv);
+		_exit(1);
+	} else if (pid == -1) {
+		wlr_log_errno(WLR_ERROR, "Unable to fork");
+		return false;
+	}
+
+	/* Set this early so that if we fail, the client process will be cleaned up properly. */
+	*pid_out = pid;
+
+	if (!set_cloexec(fd[0]) || !set_cloexec(fd[1])) {
+		return false;
+	}
+
+	/* Close write, we only need read in Cage. */
+	close(fd[1]);
+
+	struct wl_event_loop *event_loop = wl_display_get_event_loop(display);
+	uint32_t mask = WL_EVENT_HANGUP | WL_EVENT_ERROR;
+	*sigchld_source = wl_event_loop_add_fd(event_loop, fd[0], mask, sigchld_handler, display);
+
+	wlr_log(WLR_DEBUG, "Child process created with pid %d", pid);
+	return true;
+}
+
+static void
+cleanup_primary_client(pid_t pid)
+{
+	int status;
+
+	waitpid(pid, &status, 0);
+
+	if (WIFEXITED(status)) {
+		wlr_log(WLR_DEBUG, "Child exited normally with exit status %d", WEXITSTATUS(status));
+	} else if (WIFSIGNALED(status)) {
+		wlr_log(WLR_DEBUG, "Child was terminated by a signal (%d)", WTERMSIG(status));
+	}
+}
+
+static bool
+drop_permissions(void)
+{
+	if (getuid() != geteuid() || getgid() != getegid()) {
+		// Set the gid and uid in the correct order.
+		if (setgid(getgid()) != 0 || setuid(getuid()) != 0) {
+			wlr_log(WLR_ERROR, "Unable to drop root, refusing to start");
+			return false;
+		}
+	}
+
+	if (setgid(0) != -1 || setuid(0) != -1) {
+		wlr_log(WLR_ERROR,
+			"Unable to drop root (we shouldn't be able to restore it after setuid), refusing to start");
+		return false;
+	}
+
+	return true;
+}
+
+static int
+handle_signal(int signal, void *user_data)
+{
+	struct wl_display *display = user_data;
+
+	switch (signal) {
+	case SIGINT:
+		/* Fallthrough */
+	case SIGTERM:
+		wl_display_terminate(display);
+		return 0;
+	default:
+		return 0;
+	}
+}
+
+static void
+handle_new_output(struct wl_listener *listener, void *user_data)
+{
+	struct cg_server *server = wl_container_of(listener, server, new_output);
+	struct wlr_output *wlr_output = user_data;
+
+	struct cg_output *output = calloc(1, sizeof(struct cg_output));
+	if (!output) {
+		wlr_log(WLR_ERROR, "Failed to allocate output");
+		return;
+	}
+
+	wlr_output_layout_add_auto(server->output_layout, wlr_output);
+
+	// TODO: do this before or after init?
+	wl_list_insert(&server->outputs, &output->link);
+	cage_output_init(output, wlr_output);
+}
+
+static void
+usage(FILE *file, const char *cage)
+{
+	fprintf(file,
+		"Usage: %s [OPTIONS] [--] APPLICATION\n"
+		"\n"
+		" -h\t Display this help message\n"
+		" -v\t Show the version number and exit\n"
+		"\n"
+		" Use -- when you want to pass arguments to APPLICATION\n",
+		cage);
+}
+
+static bool
+parse_args(struct cg_server *server, int argc, char *argv[])
+{
+	int c;
+	while ((c = getopt(argc, argv, "hv")) != -1) {
+		switch (c) {
+		case 'h':
+			usage(stdout, argv[0]);
+			return false;
+		case 'v':
+			fprintf(stdout, "Cage version " CAGE_VERSION "\n");
+			exit(0);
+		default:
+			usage(stderr, argv[0]);
+			return false;
+		}
+	}
+
+	if (optind >= argc) {
+		usage(stderr, argv[0]);
+		return false;
+	}
+
+	return true;
+}
+
+int
+main(int argc, char *argv[])
+{
+	struct cg_server server = {0};
+	struct wl_event_loop *event_loop = NULL;
+	struct wl_event_source *sigint_source = NULL;
+	struct wl_event_source *sigterm_source = NULL;
+	struct wl_event_source *sigchld_source = NULL;
+	struct wlr_backend *backend = NULL;
+	struct wlr_renderer *renderer = NULL;
+	struct wlr_compositor *compositor = NULL;
+	pid_t pid = 0;
+	int ret = 0;
+
+	if (!parse_args(&server, argc, argv)) {
+		return 1;
+	}
+
+#ifdef DEBUG
+	wlr_log_init(WLR_DEBUG, NULL);
+#else
+	wlr_log_init(WLR_ERROR, NULL);
+#endif
+
+	/* Wayland requires XDG_RUNTIME_DIR to be set. */
+	if (!getenv("XDG_RUNTIME_DIR")) {
+		wlr_log(WLR_ERROR, "XDG_RUNTIME_DIR is not set in the environment");
+		return 1;
+	}
+
+	server.wl_display = wl_display_create();
+	if (!server.wl_display) {
+		wlr_log(WLR_ERROR, "Cannot allocate a Wayland display");
+		return 1;
+	}
+
+	event_loop = wl_display_get_event_loop(server.wl_display);
+	sigint_source = wl_event_loop_add_signal(event_loop, SIGINT, handle_signal, &server.wl_display);
+	sigterm_source = wl_event_loop_add_signal(event_loop, SIGTERM, handle_signal, &server.wl_display);
+
+	backend = wlr_backend_autocreate(server.wl_display, NULL);
+	if (!backend) {
+		wlr_log(WLR_ERROR, "Unable to create the wlroots backend");
+		ret = 1;
+		goto end;
+	}
+
+	if (!drop_permissions()) {
+		ret = 1;
+		goto end;
+	}
+
+	renderer = wlr_backend_get_renderer(backend);
+	wlr_renderer_init_wl_display(renderer, server.wl_display);
+
+	compositor = wlr_compositor_create(server.wl_display, renderer);
+	if (!compositor) {
+		wlr_log(WLR_ERROR, "Unable to create the wlroots compositor");
+		ret = 1;
+		goto end;
+	}
+
+	server.output_layout = wlr_output_layout_create();
+	if (!server.output_layout) {
+		wlr_log(WLR_ERROR, "Unable to create output layout");
+		ret = 1;
+		goto end;
+	}
+
+	wl_list_init(&server.outputs);
+	server.new_output.notify = handle_new_output;
+	wl_signal_add(&backend->events.new_output, &server.new_output);
+
+	const char *socket = wl_display_add_socket_auto(server.wl_display);
+	if (!socket) {
+		wlr_log_errno(WLR_ERROR, "Unable to open Wayland socket");
+		ret = 1;
+		goto end;
+	}
+
+	if (!wlr_backend_start(backend)) {
+		wlr_log(WLR_ERROR, "Unable to start the wlroots backend");
+		ret = 1;
+		goto end;
+	}
+
+	if (setenv("WAYLAND_DISPLAY", socket, true) < 0) {
+		wlr_log_errno(WLR_ERROR, "Unable to set WAYLAND_DISPLAY. Clients may not be able to connect");
+	} else {
+		wlr_log(WLR_DEBUG, "Cage " CAGE_VERSION " is running on Wayland display %s", socket);
+	}
+
+	if (!spawn_primary_client(server.wl_display, argv + optind, &pid, &sigchld_source)) {
+		ret = 1;
+		goto end;
+	}
+
+	wl_display_run(server.wl_display);
+	wl_display_destroy_clients(server.wl_display);
+
+end:
+	cleanup_primary_client(pid);
+
+	wl_event_source_remove(sigint_source);
+	wl_event_source_remove(sigterm_source);
+	if (sigchld_source) {
+		wl_event_source_remove(sigchld_source);
+	}
+	/* This function is not null-safe, but we only ever get here
+	   with a proper wl_display. */
+	wl_display_destroy(server.wl_display);
+	wlr_output_layout_destroy(server.output_layout);
+	return ret;
+}