Parse and validate subnet ranges

Makefile

@@ -0,0 +1,8 @@
+build:
+	CGO_ENABLED=0 go build -v -ldflags="-s -w"
+
+run:
+	./wireguard-ui
+
+clean:
+	rm -f wireguard-ui

handler/routes.go

@@ -381,9 +381,9 @@ func GetClient(db store.IStore) echo.HandlerFunc {
 		}
 
 		qrCodeSettings := model.QRCodeSettings{
-			Enabled:       true,
-			IncludeDNS:    true,
-			IncludeMTU:    true,
+			Enabled:    true,
+			IncludeDNS: true,
+			IncludeMTU: true,
 		}
 
 		clientData, err := db.GetClientByID(clientID, qrCodeSettings)
@@ -513,9 +513,9 @@ func EmailClient(db store.IStore, mailer emailer.Emailer, emailSubject, emailCon
 		}
 
 		qrCodeSettings := model.QRCodeSettings{
-			Enabled:       true,
-			IncludeDNS:    true,
-			IncludeMTU:    true,
+			Enabled:    true,
+			IncludeDNS: true,
+			IncludeMTU: true,
 		}
 		clientData, err := db.GetClientByID(payload.ID, qrCodeSettings)
 		if err != nil {
@@ -1078,7 +1078,6 @@ func ApplyServerConfig(db store.IStore, tmplDir fs.FS) echo.HandlerFunc {
 	}
 }
 
-
 // GetHashesChanges handler returns if database hashes have changed
 func GetHashesChanges(db store.IStore) echo.HandlerFunc {
 	return func(c echo.Context) error {

main.go

@@ -45,6 +45,7 @@ var (
 	flagSessionSecret  string = util.RandomString(32)
 	flagWgConfTemplate string
 	flagBasePath       string
+	flagSubnetRanges   string
 )
 
 const (
@@ -81,6 +82,7 @@ func init() {
 	flag.StringVar(&flagEmailFromName, "email-from-name", util.LookupEnvOrString("EMAIL_FROM_NAME", flagEmailFromName), "'From' email name.")
 	flag.StringVar(&flagWgConfTemplate, "wg-conf-template", util.LookupEnvOrString("WG_CONF_TEMPLATE", flagWgConfTemplate), "Path to custom wg.conf template.")
 	flag.StringVar(&flagBasePath, "base-path", util.LookupEnvOrString("BASE_PATH", flagBasePath), "The base path of the URL")
+	flag.StringVar(&flagSubnetRanges, "subnet-ranges", util.LookupEnvOrString("SUBNET_RANGES", flagSubnetRanges), "IP ranges to choose from when assigning an IP for a client.")
 
 	var (
 		smtpPasswordLookup  = util.LookupEnvOrString("SMTP_PASSWORD", flagSmtpPassword)
@@ -127,6 +129,7 @@ func init() {
 	util.SessionSecret = []byte(flagSessionSecret)
 	util.WgConfTemplate = flagWgConfTemplate
 	util.BasePath = util.ParseBasePath(flagBasePath)
+	util.SubnetRanges = util.ParseSubnetRanges(flagSubnetRanges)
 
 	// print only if log level is INFO or lower
 	if lvl, _ := util.ParseLogLevel(util.LookupEnvOrString(util.LogLevel, "INFO")); lvl <= log.INFO {
@@ -145,6 +148,7 @@ func init() {
 		//fmt.Println("Session secret\t:", util.SessionSecret)
 		fmt.Println("Custom wg.conf\t:", util.WgConfTemplate)
 		fmt.Println("Base path\t:", util.BasePath+"/")
+		fmt.Println("Subnet ranges\t:", util.GetSubnetRangesString())
 	}
 }
 
@@ -170,6 +174,17 @@ func main() {
 	// create the wireguard config on start, if it doesn't exist
 	initServerConfig(db, tmplDir)
 
+	// Check if subnet ranges are valid for the server configuration
+	// Remove any non-valid CIDRs
+	if err := util.ValidateAndFixSubnetRanges(db); err != nil {
+		panic(err)
+	}
+
+	// Print valid ranges
+	if lvl, _ := util.ParseLogLevel(util.LookupEnvOrString(util.LogLevel, "INFO")); lvl <= log.INFO {
+		fmt.Println("Valid subnet ranges:", util.GetSubnetRangesString())
+	}
+
 	// register routes
 	app := router.New(tmplDir, extraData, util.SessionSecret)
 

util/config.go

@@ -1,24 +1,31 @@
 package util
 
-import "strings"
+import (
+	"net"
+	"strings"
+
+	"github.com/labstack/gommon/log"
+)
 
 // Runtime config
 var (
-	DisableLogin   bool
-	BindAddress    string
-	SmtpHostname   string
-	SmtpPort       int
-	SmtpUsername   string
-	SmtpPassword   string
-	SmtpNoTLSCheck bool
-	SmtpEncryption string
-	SmtpAuthType   string
-	SendgridApiKey string
-	EmailFrom      string
-	EmailFromName  string
-	SessionSecret  []byte
-	WgConfTemplate string
-	BasePath       string
+	DisableLogin      bool
+	BindAddress       string
+	SmtpHostname      string
+	SmtpPort          int
+	SmtpUsername      string
+	SmtpPassword      string
+	SmtpNoTLSCheck    bool
+	SmtpEncryption    string
+	SmtpAuthType      string
+	SendgridApiKey    string
+	EmailFrom         string
+	EmailFromName     string
+	SessionSecret     []byte
+	WgConfTemplate    string
+	BasePath          string
+	SubnetRanges      map[string]([]*net.IPNet)
+	SubnetRangesOrder []string
 )
 
 const (
@@ -66,3 +73,45 @@ func ParseBasePath(basePath string) string {
 	}
 	return basePath
 }
+
+func ParseSubnetRanges(subnetRangesStr string) map[string]([]*net.IPNet) {
+	subnetRanges := map[string]([]*net.IPNet){}
+	if subnetRangesStr == "" {
+		return subnetRanges
+	}
+	cidrSet := map[string]bool{}
+	subnetRangesStr = strings.TrimSpace(subnetRangesStr)
+	subnetRangesStr = strings.Trim(subnetRangesStr, ";:,")
+	ranges := strings.Split(subnetRangesStr, ";")
+	for _, rng := range ranges {
+		rng = strings.TrimSpace(rng)
+		rngSpl := strings.Split(rng, ":")
+		if len(rngSpl) != 2 {
+			log.Warnf("Unable to parse subnet range: %v. Skipped.", rng)
+			continue
+		}
+		rngName := strings.TrimSpace(rngSpl[0])
+		subnetRanges[rngName] = make([]*net.IPNet, 0)
+		cidrs := strings.Split(rngSpl[1], ",")
+		for _, cidr := range cidrs {
+			cidr = strings.TrimSpace(cidr)
+			_, net, err := net.ParseCIDR(cidr)
+			if err != nil {
+				log.Warnf("[%v] Unable to parse CIDR: %v. Skipped.", rngName, cidr)
+				continue
+			}
+			if cidrSet[net.String()] {
+				log.Warnf("[%v] CIDR already exists: %v. Skipped.", rngName, net.String())
+				continue
+			}
+			cidrSet[net.String()] = true
+			subnetRanges[rngName] = append(subnetRanges[rngName], net)
+		}
+		if len(subnetRanges[rngName]) == 0 {
+			delete(subnetRanges, rngName)
+		} else {
+			SubnetRangesOrder = append(SubnetRangesOrder, rngName)
+		}
+	}
+	return subnetRanges
+}

util/util.go

@@ -95,6 +95,15 @@ func ClientDefaultsFromEnv() model.ClientDefaults {
 	return clientDefaults
 }
 
+// ContainsCIDR to check if ipnet1 contains ipnet2
+// https://stackoverflow.com/a/40406619/6111641
+// https://go.dev/play/p/Q4J-JEN3sF
+func ContainsCIDR(ipnet1, ipnet2 *net.IPNet) bool {
+	ones1, _ := ipnet1.Mask.Size()
+	ones2, _ := ipnet2.Mask.Size()
+	return ones1 <= ones2 && ipnet1.Contains(ipnet2.IP)
+}
+
 // ValidateCIDR to validate a network CIDR
 func ValidateCIDR(cidr string) bool {
 	_, _, err := net.ParseCIDR(cidr)
@@ -384,6 +393,88 @@ func ValidateIPAllocation(serverAddresses []string, ipAllocatedList []string, ip
 	return true, nil
 }
 
+// ValidateAndFixSubnetRanges to check if subnet ranges are valid for the server configuration
+// Removes all non-valid CIDRs
+func ValidateAndFixSubnetRanges(db store.IStore) error {
+	if len(SubnetRangesOrder) == 0 {
+		return nil
+	}
+
+	server, err := db.GetServer()
+	if err != nil {
+		return err
+	}
+	var serverSubnets []*net.IPNet
+	for _, addr := range server.Interface.Addresses {
+		addr = strings.TrimSpace(addr)
+		_, net, err := net.ParseCIDR(addr)
+		if err != nil {
+			return err
+		}
+		serverSubnets = append(serverSubnets, net)
+	}
+
+	for _, rng := range SubnetRangesOrder {
+		cidrs := SubnetRanges[rng]
+		if len(cidrs) > 0 {
+			newCIDRs := make([]*net.IPNet, 0)
+			for _, cidr := range cidrs {
+				valid := false
+
+				for _, serverSubnet := range serverSubnets {
+					if ContainsCIDR(serverSubnet, cidr) {
+						valid = true
+						break
+					}
+				}
+
+				if valid {
+					newCIDRs = append(newCIDRs, cidr)
+				} else {
+					log.Warnf("[%v] CIDR is outside of all server subnets: %v. Removed.", rng, cidr)
+				}
+			}
+
+			if len(newCIDRs) > 0 {
+				SubnetRanges[rng] = newCIDRs
+			} else {
+				delete(SubnetRanges, rng)
+				log.Warnf("[%v] No valid CIDRs in this subnet range. Removed.", rng)
+			}
+		}
+	}
+
+	return nil
+}
+
+// GetSubnetRangesString to get a formatted string, representing active subnet ranges
+func GetSubnetRangesString() string {
+	if len(SubnetRangesOrder) == 0 {
+		return ""
+	}
+
+	strB := strings.Builder{}
+
+	for _, rng := range SubnetRangesOrder {
+		cidrs := SubnetRanges[rng]
+		if len(cidrs) > 0 {
+			strB.WriteString(rng)
+			strB.WriteString(":[")
+			first := true
+			for _, cidr := range cidrs {
+				if !first {
+					strB.WriteString(", ")
+				}
+				strB.WriteString(cidr.String())
+				first = false
+			}
+			strB.WriteString("]  ")
+		}
+	}
+
+	return strings.TrimSpace(strB.String())
+}
+
 // WriteWireGuardServerConfig to write Wireguard server config. e.g. wg0.conf
 func WriteWireGuardServerConfig(tmplDir fs.FS, serverConfig model.Server, clientDataList []model.ClientData, usersList []model.User, globalSettings model.GlobalSetting) error {
 	var tmplWireguardConf string