weston: Drop priviledges early, and seteuid when needed

src/compositor.c

@@ -2088,6 +2088,9 @@ int main(int argc, char *argv[])
 		{ NULL, }
 	};
 
+	/* Drop privilidges early, use getresuid when needed again */
+	seteuid(getuid());
+
 	while (o = getopt_long(argc, argv, opts, longopts, &o), o > 0) {
 		switch (o) {
 		case 'B':

src/evdev.c

@@ -20,6 +20,8 @@
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#define _GNU_SOURCE
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -439,6 +441,7 @@ evdev_input_device_create(struct evdev_input *master,
 	struct evdev_input_device *device;
 	struct wl_event_loop *loop;
 	struct weston_compositor *ec;
+	uid_t saved_uid, uid, euid;
 
 	device = malloc(sizeof *device);
 	if (device == NULL)
@@ -456,7 +459,10 @@ evdev_input_device_create(struct evdev_input *master,
 	device->rel.dx = 0;
 	device->rel.dy = 0;
 
+	getresuid(&uid, &euid, &saved_uid);
+	seteuid(saved_uid);
 	device->fd = open(path, O_RDONLY);
+	seteuid(euid);
 	if (device->fd < 0)
 		goto err0;
 

src/tty.c

@@ -20,6 +20,8 @@
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#define _GNU_SOURCE
+
 #include <termios.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -128,6 +130,7 @@ tty_create(struct weston_compositor *compositor, tty_vt_func_t vt_func,
 	struct wl_event_loop *loop;
 	struct stat buf;
 	char filename[16];
+	uid_t saved_uid, uid, euid;
 
 	tty = malloc(sizeof *tty);
 	if (tty == NULL)
@@ -136,6 +139,8 @@ tty_create(struct weston_compositor *compositor, tty_vt_func_t vt_func,
 	memset(tty, 0, sizeof *tty);
 	tty->compositor = compositor;
 	tty->vt_func = vt_func;
+	getresuid(&uid, &euid, &saved_uid);
+	seteuid(saved_uid);
 	if (tty_nr > 0) {
 		snprintf(filename, sizeof filename, "/dev/tty%d", tty_nr);
 		fprintf(stderr, "compositor: using %s\n", filename);
@@ -152,11 +157,13 @@ tty_create(struct weston_compositor *compositor, tty_vt_func_t vt_func,
 
 	if (tty->fd <= 0) {
 		fprintf(stderr, "failed to open tty: %m\n");
+		seteuid(euid);
 		return NULL;
 	}
 
 	if (tcgetattr(tty->fd, &tty->terminal_attributes) < 0) {
 		fprintf(stderr, "could not get terminal attributes: %m\n");
+		seteuid(euid);
 		return NULL;
 	}
 
@@ -178,6 +185,7 @@ tty_create(struct weston_compositor *compositor, tty_vt_func_t vt_func,
 	ret = ioctl(tty->fd, KDSETMODE, KD_GRAPHICS);
 	if (ret) {
 		fprintf(stderr, "failed to set KD_GRAPHICS mode on tty: %m\n");
+		seteuid(euid);
 		return NULL;
 	}
 
@@ -187,9 +195,12 @@ tty_create(struct weston_compositor *compositor, tty_vt_func_t vt_func,
 	mode.acqsig = SIGUSR1;
 	if (ioctl(tty->fd, VT_SETMODE, &mode) < 0) {
 		fprintf(stderr, "failed to take control of vt handling\n");
+		seteuid(euid);
 		return NULL;
 	}
 
+	seteuid(euid);
+
 	tty->vt_source =
 		wl_event_loop_add_signal(loop, SIGUSR1, vt_handler, tty);