overlay coreos/config: Add Flatcar modifications for sys-apps/shadow

sdk_container/src/third_party/coreos-overlay/coreos/config/env/sys-apps/shadow

@@ -0,0 +1,75 @@
+cros_post_src_install_shadow_flatcar_modifications() {
+    (
+        insopts -m 0644
+        insinto /usr/lib/tmpfiles.d
+        newins - var-shadow.conf <<'EOF'
+f   /var/log/faillog        -   -   -   -   -
+EOF
+    )
+
+    local f
+    # install these for backward compatibility
+    for f in 'securetty' 'login.defs'; do
+        dosym -r "/usr/share/flatcar/etc/${f}" "/usr/share/shadow/${f}"
+        insinto /usr/share/flatcar/etc
+        newins - "${f}"
+    done
+    dosym -r /usr/share/flatcar/etc/default/useradd /usr/share/shadow/useradd
+    insinto /usr/share/flatcar/etc/default
+    newins - useradd
+
+    # Install our own securetty file with additional arch-specific cruft
+    local devs=''
+    case $(tc-arch) in
+        ppc*)
+            devs="hvc0 hvsi0 ttyPSC0";;
+        hppa)
+            devs="ttyB0";;
+        arm)
+            devs="ttyFB0 ttySAC0 ttySAC1 ttySAC2 ttySAC3 ttymxc0 ttymxc1 ttymxc2 ttymxc3 ttyO0 ttyO1 ttyO2";;
+        sh)
+            devs="ttySC0 ttySC1";;
+        amd64|x86)
+            devs="hvc0";;
+    esac
+
+    insopts -m0600
+    insinto /etc/
+    newins - securetty <<EOF
+# /etc/securetty: list of terminals on which root is allowed to login.
+# See securetty(5) and login(1).
+console
+
+vc/0
+vc/1
+vc/2
+vc/3
+vc/4
+vc/5
+vc/6
+vc/7
+vc/8
+vc/9
+vc/10
+vc/11
+vc/12
+tty0
+tty1
+tty2
+tty3
+tty4
+tty5
+tty6
+tty7
+tty8
+tty9
+tty10
+tty11
+tty12
+
+tts/0
+ttyS0
+
+${devs}
+EOF
+}