From 004130ae74688eb321aadc05192bab69fe5cbcbf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Fri, 22 Jul 2022 11:45:12 +0200
Subject: [PATCH] manager: limit access to private dbus socket

For the system manager, /run/systemd/private is publicly accessible, because
/run/systemd is 0755, and /run/systemd/private is 0777. For the user manager,
/run/user/<uid> is 0700, and /run/user/<uid>/systemd/private is 0777. This
does not directly cause any security issue because we check the sender in
bus_check_peercred (ucred.uid != 0 && ucred.uid != geteuid()).

But it makes sense to limit access to the socket to avoid wasting time in PID1.
Somebody could send messages there that'd we'd reject anyway. It also makes
things more explicit.

(cherry picked from commit df1cbd1adf26071aab41d96e054452a3d66103a4)

Resolves: #2119405
---
 src/core/dbus.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/core/dbus.c b/src/core/dbus.c
index 66d838cdb4..ec6c52cb85 100644
--- a/src/core/dbus.c
+++ b/src/core/dbus.c
@@ -42,6 +42,7 @@
 #include "string-util.h"
 #include "strv.h"
 #include "strxcpyx.h"
+#include "umask-util.h"
 #include "user-util.h"
 
 #define CONNECTIONS_MAX 4096
@@ -1019,7 +1020,8 @@ int bus_init_private(Manager *m) {
         if (fd < 0)
                 return log_error_errno(errno, "Failed to allocate private socket: %m");
 
-        r = bind(fd, &sa.sa, salen);
+        RUN_WITH_UMASK(0077)
+                r = bind(fd, &sa.sa, salen);
         if (r < 0)
                 return log_error_errno(errno, "Failed to bind private socket: %m");