wg-installer: check if a key is already inserted

Check if a peer is already existing with a given public key. Introduce a
response code for signaling why the server rejected the request.

Signed-off-by: Nick Hainke <vincent@systemli.org>

net/wg-installer/wg-client/lib/rpcd_ubus.sh

@@ -95,6 +95,15 @@ wg_rpcd_get_usage () {
 	echo "num_interfaces: ${num_interfaces}"
 }
 
+wg_error_handling () {
+	local response_code=$1
+
+	case "$response_code" in
+		1)	logger -t "wginstaller" "Server rejected request since the public key is already used!" ;;
+		*)	logger -t "wginstaller" "Unknown Error Code!";;
+	esac
+}
+
 wg_rpcd_register () {
 	local token=$5
 	local ip=$6
@@ -123,6 +132,11 @@ wg_rpcd_register () {
 	json_get_vars result result
 	json_select result
 	json_select 2
+	json_get_var response_code response_code
+	if [ "$response_code" -ne 0 ]; then
+		wg_error_handling "$response_code"
+		return 1
+	fi
 	json_get_var gw_pubkey gw_pubkey
 	json_get_var gw_ipv4 gw_ipv4
 	json_get_var gw_ipv6 gw_ipv6

net/wg-installer/wg-server/lib/wg_functions.sh

@@ -3,6 +3,12 @@
 . /usr/share/libubox/jshn.sh
 . /usr/share/wginstaller/wg.sh
 
+wg_key_exists () {
+	local key=$1
+
+	wg show | grep -q "$key"
+}
+
 wg_timeout () {
 	local int=$1
 
@@ -42,6 +48,14 @@ wg_register () {
 	local mtu=$2
 	local public_key=$3
 
+	if wg_key_exists $public_key; then
+		logger -t "wginstaller" "Rejecting request since the public key is already used!" "$public_key"
+		json_init
+		json_add_int "response_code" 1
+		json_dump
+		return 1
+	fi
+
 	base_prefix_ipv6=$(uci get wgserver.@server[0].base_prefix_ipv6)
 	port_start=$(uci get wgserver.@server[0].port_start)
 	port_end=$(uci get wgserver.@server[0].port_end)
@@ -82,6 +96,7 @@ wg_register () {
 
 	# craft return address
 	json_init
+	json_add_int "response_code" 0
 	json_add_string "gw_pubkey" "$wg_server_pubkey"
 	if test -n "${gw_ipv4_assign-}"; then
 		json_add_string "gw_ipv4" "$gw_ipv4_assign"