Keep CAP_SYS_PTRACE with suid binary
#include <unistd.h>
#include <getopt.h>
#include <sys/capability.h>
+#ifdef __linux__
+#include <sys/prctl.h>
+#endif
#include "sway/extensions.h"
#include "sway/layout.h"
#include "sway/config.h"
@@ -289,6 +292,18 @@ int main(int argc, char **argv) {
return 0;
}
+#ifdef __linux__
+ bool suid = false;
+ if (getuid() != geteuid() || getgid() != getegid()) {
+ // Retain capabilities after setuid()
+ if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0)) {
+ sway_log(L_ERROR, "Cannot keep caps after setuid()");
+ exit(EXIT_FAILURE);
+ }
+ suid = true;
+ }
+#endif
+
// we need to setup logging before wlc_init in case it fails.
if (debug) {
init_log(L_DEBUG);
@@ -311,6 +326,19 @@ int main(int argc, char **argv) {
}
register_extensions();
+#ifdef __linux__
+ if (suid) {
+ // Drop every cap except CAP_SYS_PTRACE
+ cap_t caps = cap_init();
+ cap_value_t keep = CAP_SYS_PTRACE;
+ if (cap_set_flag(caps, CAP_PERMITTED, 1, &keep, CAP_SET) ||
+ cap_set_flag(caps, CAP_EFFECTIVE, 1, &keep, CAP_SET) ||
+ cap_set_proc(caps)) {
+ sway_log(L_ERROR, "Failed to drop extra capabilities");
+ exit(EXIT_FAILURE);
+ }
+ }
+#endif
// handle SIGTERM signals
signal(SIGTERM, sig_handler);
