feat: support for url based icons (#840)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/utils/ip_util.go

@@ -0,0 +1,87 @@
+package utils
+
+import (
+	"net"
+	"strings"
+
+	"github.com/pocket-id/pocket-id/backend/internal/common"
+)
+
+var localIPv6Ranges []*net.IPNet
+
+var localhostIPNets = []*net.IPNet{
+	{IP: net.IPv4(127, 0, 0, 0), Mask: net.CIDRMask(8, 32)}, // 127.0.0.0/8
+	{IP: net.IPv6loopback, Mask: net.CIDRMask(128, 128)},    // ::1/128
+}
+
+var privateLanIPNets = []*net.IPNet{
+	{IP: net.IPv4(10, 0, 0, 0), Mask: net.CIDRMask(8, 32)},     // 10.0.0.0/8
+	{IP: net.IPv4(172, 16, 0, 0), Mask: net.CIDRMask(12, 32)},  // 172.16.0.0/12
+	{IP: net.IPv4(192, 168, 0, 0), Mask: net.CIDRMask(16, 32)}, // 192.168.0.0/16
+}
+
+var tailscaleIPNets = []*net.IPNet{
+	{IP: net.IPv4(100, 64, 0, 0), Mask: net.CIDRMask(10, 32)}, // 100.64.0.0/10
+}
+
+func IsLocalIPv6(ip net.IP) bool {
+	if ip.To4() != nil {
+		return false
+	}
+
+	return listContainsIP(localIPv6Ranges, ip)
+}
+
+func IsLocalhostIP(ip net.IP) bool {
+	return listContainsIP(localhostIPNets, ip)
+}
+
+func IsPrivateLanIP(ip net.IP) bool {
+	if ip.To4() == nil {
+		return false
+	}
+
+	return listContainsIP(privateLanIPNets, ip)
+}
+
+func IsTailscaleIP(ip net.IP) bool {
+	if ip.To4() == nil {
+		return false
+	}
+
+	return listContainsIP(tailscaleIPNets, ip)
+}
+
+func IsPrivateIP(ip net.IP) bool {
+	return IsLocalhostIP(ip) || IsPrivateLanIP(ip) || IsTailscaleIP(ip) || IsLocalIPv6(ip)
+}
+
+func listContainsIP(ipNets []*net.IPNet, ip net.IP) bool {
+	for _, ipNet := range ipNets {
+		if ipNet.Contains(ip) {
+			return true
+		}
+	}
+	return false
+}
+
+func loadLocalIPv6Ranges() {
+	localIPv6Ranges = nil
+	ranges := strings.Split(common.EnvConfig.LocalIPv6Ranges, ",")
+
+	for _, rangeStr := range ranges {
+		rangeStr = strings.TrimSpace(rangeStr)
+		if rangeStr == "" {
+			continue
+		}
+
+		_, ipNet, err := net.ParseCIDR(rangeStr)
+		if err == nil {
+			localIPv6Ranges = append(localIPv6Ranges, ipNet)
+		}
+	}
+}
+
+func init() {
+	loadLocalIPv6Ranges()
+}