rng-tools: Restrict rngd.service

Whilst rngd has to run as root, we can significantly constrain its
permissions (network is only required if nistbeacon is enabled).

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

diff --git a/meta/recipes-support/rng-tools/rng-tools/rngd.service b/meta/recipes-support/rng-tools/rng-tools/rngd.service
index 084322ac40aab9866bda1a78f061e81ba7d50224..0559b97991546405e4e63f7e9b6e299e72bbf805 100644 (file)
--- a/meta/recipes-support/rng-tools/rng-tools/rngd.service
+++ b/meta/recipes-support/rng-tools/rng-tools/rngd.service
@@ -8,6 +8,25 @@ Conflicts=shutdown.target
 [Service]
 EnvironmentFile=-@SYSCONFDIR@/default/rng-tools
 ExecStart=@SBINDIR@/rngd -f $EXTRA_ARGS
+CapabilityBoundingSet=CAP_SYS_ADMIN
+IPAddressDeny=any
+LockPersonality=yes
+MemoryDenyWriteExecute=yes
+NoNewPrivileges=yes
+PrivateTmp=yes
+ProtectControlGroups=yes
+ProtectHome=yes
+ProtectHostname=yes
+ProtectKernelModules=yes
+ProtectKernelLogs=yes
+ProtectSystem=strict
+RestrictAddressFamilies=AF_UNIX
+RestrictNamespaces=yes
+RestrictRealtime=yes
+RestrictSUIDSGID=yes
+SystemCallArchitectures=native
+SystemCallErrorNumber=EPERM
+SystemCallFilter=@system-service
 
 [Install]
 WantedBy=sysinit.target

diff --git a/meta/recipes-support/rng-tools/rng-tools_6.9.bb b/meta/recipes-support/rng-tools/rng-tools_6.9.bb
index 913342c315de97ae979ec007ca211aa59fe829a7..8c98a9aa3ae2ef6e8839cab90897ea692b1a8195 100644 (file)
--- a/meta/recipes-support/rng-tools/rng-tools_6.9.bb
+++ b/meta/recipes-support/rng-tools/rng-tools_6.9.bb
@@ -49,4 +49,11 @@ do_install_append() {
         -e 's,@SBINDIR@,${sbindir},g' \
         ${D}${sysconfdir}/init.d/rng-tools \
         ${D}${systemd_system_unitdir}/rngd.service
+
+    if [ "${@bb.utils.contains('PACKAGECONFIG', 'nistbeacon', 'yes', 'no', d)}" = "yes" ]; then
+        sed -i \
+            -e '/^IPAddressDeny=any/d' \
+            -e '/^RestrictAddressFamilies=/ s/$/ AF_INET AF_INET6/' \
+            ${D}${systemd_system_unitdir}/rngd.service
+    fi
 }