From ea1313d80d5ee1623b00c8cdf6e7ff8a7e14c2ae Mon Sep 17 00:00:00 2001
From: Mykyta Holubakha <hilobakho@gmail.com>
Date: Thu, 12 Jan 2017 04:25:03 +0200
Subject: Keep CAP_SYS_PTRACE with suid binary
---
sway/main.c | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/sway/main.c b/sway/main.c
index e8a02e7a..6c74aab2 100644
--- a/sway/main.c
+++ b/sway/main.c
@@ -10,6 +10,9 @@
#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);
--
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