linux-pam: adjust login pam file for SELinux

When SELinux support is enabled, the login pam file installed by
linux-pam should be adjusted to use the pam_selinux.so module.

To achieve this in a reasonably simple manner, we introduce the SELinux
related lines in login.pam as comments, and if SELinux support is
enabled, turn those commented lines into real lines.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Bryce Ferguson <bryce.ferguson@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/linux-pam/linux-pam.mk

@@ -29,6 +29,10 @@ endif
 ifeq ($(BR2_PACKAGE_LIBSELINUX),y)
 LINUX_PAM_CONF_OPTS += --enable-selinux
 LINUX_PAM_DEPENDENCIES += libselinux
+define LINUX_PAM_SELINUX_PAMFILE_TWEAK
+	$(SED) 's/^# \(.*pam_selinux.so.*\)$$/\1/' \
+		$(TARGET_DIR)/etc/pam.d/login
+endef
 else
 LINUX_PAM_CONF_OPTS += --disable-selinux
 endif
@@ -46,6 +50,7 @@ define LINUX_PAM_INSTALL_CONFIG
 		$(TARGET_DIR)/etc/pam.d/login
 	$(INSTALL) -m 0644 -D package/linux-pam/other.pam \
 		$(TARGET_DIR)/etc/pam.d/other
+	$(LINUX_PAM_SELINUX_PAMFILE_TWEAK)
 endef
 
 LINUX_PAM_POST_INSTALL_TARGET_HOOKS += LINUX_PAM_INSTALL_CONFIG

package/linux-pam/login.pam

@@ -4,7 +4,9 @@ account		required	pam_unix.so
 
 password	required	pam_unix.so nullok
 
+# session	required	pam_selinux.so close
 session		required	pam_limits.so
 session		required	pam_env.so
 session		required	pam_unix.so
 session		optional	pam_lastlog.so
+# session	required	pam_selinux.so open