networkd: run as unpriviliged "systemd-network" user

This allows us to run networkd mostly unpriviliged with the exception of
CAP_NET_* and CAP_SYS_MODULE. I'd really like to get rid of the latter
though...

diff --git a/Makefile.am b/Makefile.am
index f66ef4275b49e7039950d99575fd39318962faa4..5158bbc776d51695cc23a382e0ecf7c3b687482b 100644 (file)
--- a/Makefile.am
+++ b/Makefile.am
@@ -4253,6 +4253,7 @@ systemd_networkd_SOURCES = \
 
 systemd_networkd_LDADD = \
        libsystemd-networkd-core.la \
+       libsystemd-capability.la \
        $(KMOD_LIBS)
 
 noinst_LTLIBRARIES += \

diff --git a/src/network/networkd.c b/src/network/networkd.c
index 6985dcaa4a64f07cd25a7aa79376404385c5aec2..cd7dd3ca0f59ca67db4f9c527b6909bfbb174ab7 100644 (file)
--- a/src/network/networkd.c
+++ b/src/network/networkd.c
@@ -19,6 +19,7 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include "capability.h"
 #include "sd-event.h"
 #include "sd-daemon.h"
 
@@ -26,6 +27,9 @@
 
 int main(int argc, char *argv[]) {
         _cleanup_manager_free_ Manager *m = NULL;
+        const char *user = "systemd-network";
+        uid_t uid;
+        gid_t gid;
         int r;
 
         log_set_target(LOG_TARGET_AUTO);
@@ -40,23 +44,38 @@ int main(int argc, char *argv[]) {
                 goto out;
         }
 
+        r = get_user_creds(&user, &uid, &gid, NULL, NULL);
+        if (r < 0) {
+                log_error("Cannot resolve user name %s: %s", user, strerror(-r));
+                goto out;
+        }
+
         /* Always create the directories people can create inotify
          * watches in. */
-        r = mkdir_label("/run/systemd/network", 0755);
+        r = mkdir_safe_label("/run/systemd/network", 0755, uid, gid);
         if (r < 0)
                 log_error("Could not create runtime directory: %s",
                           strerror(-r));
 
-        r = mkdir_label("/run/systemd/network/links", 0755);
+        r = mkdir_safe_label("/run/systemd/network/links", 0755, uid, gid);
         if (r < 0)
                 log_error("Could not create runtime directory 'links': %s",
                           strerror(-r));
 
-        r = mkdir_label("/run/systemd/network/leases", 0755);
+        r = mkdir_safe_label("/run/systemd/network/leases", 0755, uid, gid);
         if (r < 0)
                 log_error("Could not create runtime directory 'leases': %s",
                           strerror(-r));
 
+        r = drop_privileges(uid, gid,
+                            (1ULL << CAP_NET_ADMIN) |
+                            (1ULL << CAP_NET_BIND_SERVICE) |
+                            (1ULL << CAP_NET_BROADCAST) |
+                            (1ULL << CAP_NET_RAW) |
+                            (1ULL << CAP_SYS_MODULE));
+        if (r < 0)
+                goto out;
+
         r = manager_new(&m);
         if (r < 0) {
                 log_error("Could not create manager: %s", strerror(-r));

diff --git a/units/systemd-networkd.service.in b/units/systemd-networkd.service.in
index 40ec90ef858da765d364570fde5ea2b8b48bed03..33c3fca488c6b154795499be7f8d395e44f9278a 100644 (file)
--- a/units/systemd-networkd.service.in
+++ b/units/systemd-networkd.service.in
@@ -19,7 +19,7 @@ Type=notify
 Restart=always
 RestartSec=0
 ExecStart=@rootlibexecdir@/systemd-networkd
-CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_NET_BROADCAST CAP_NET_RAW CAP_SYS_MODULE
+CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_NET_BROADCAST CAP_NET_RAW CAP_SYS_MODULE CAP_SETUID CAP_SETGID CAP_SETPCAP CAP_CHOWN CAP_DAC_OVERRIDE CAP_FOWNER
 WatchdogSec=1min
 
 [Install]