X-Forwarded-For handler for labstack echo and Fastly

xff/fastlyxff/xff.go

@@ -0,0 +1,51 @@
+package fastlyxff
+
+import (
+	"encoding/json"
+	"net"
+	"net/netip"
+	"os"
+
+	"github.com/labstack/echo/v4"
+)
+
+type FastlyXFF struct {
+	IPv4 []string `json:"addresses"`
+	IPv6 []string `json:"ipv6_addresses"`
+}
+
+type TrustedNets struct {
+	prefixes []netip.Prefix
+}
+
+func New(fileName string) (*FastlyXFF, error) {
+	b, err := os.ReadFile(fileName)
+	if err != nil {
+		return nil, err
+	}
+
+	d := FastlyXFF{}
+
+	err = json.Unmarshal(b, &d)
+	if err != nil {
+		return nil, err
+	}
+
+	return &d, nil
+}
+
+func (xff *FastlyXFF) EchoTrustOption() ([]echo.TrustOption, error) {
+	ranges := []echo.TrustOption{}
+
+	for _, s := range append(xff.IPv4, xff.IPv6...) {
+		_, cidr, err := net.ParseCIDR(s)
+		if err != nil {
+			return nil, err
+		}
+
+		trust := echo.TrustIPRange(cidr)
+		ranges = append(ranges, trust)
+	}
+
+	return ranges, nil
+}