1 files changed, 78 insertions, 0 deletions
diff --git a/internal/netutil/validate.go b/internal/netutil/validate.go
new file mode 100644
index 000000000..27cc9ba4a
--- /dev/null
+++ b/internal/netutil/validate.go
@@ -0,0 +1,78 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package netutil
+
+import (
+	"net/netip"
+)
+
+var (
+	// IPv6GlobalUnicast is the global IPv6 unicast IP prefix.
+	IPv6GlobalUnicast = netip.MustParsePrefix("ff00::/8")
+
+	// IPvReserved contains IPv4 reserved IP prefixes.
+	IPv4Reserved = [...]netip.Prefix{
+		netip.MustParsePrefix("0.0.0.0/8"),       // Current network
+		netip.MustParsePrefix("10.0.0.0/8"),      // Private
+		netip.MustParsePrefix("100.64.0.0/10"),   // RFC6598
+		netip.MustParsePrefix("127.0.0.0/8"),     // Loopback
+		netip.MustParsePrefix("169.254.0.0/16"),  // Link-local
+		netip.MustParsePrefix("172.16.0.0/12"),   // Private
+		netip.MustParsePrefix("192.0.0.0/24"),    // RFC6890
+		netip.MustParsePrefix("192.0.2.0/24"),    // Test, doc, examples
+		netip.MustParsePrefix("192.88.99.0/24"),  // IPv6 to IPv4 relay
+		netip.MustParsePrefix("192.168.0.0/16"),  // Private
+		netip.MustParsePrefix("198.18.0.0/15"),   // Benchmarking tests
+		netip.MustParsePrefix("198.51.100.0/24"), // Test, doc, examples
+		netip.MustParsePrefix("203.0.113.0/24"),  // Test, doc, examples
+		netip.MustParsePrefix("224.0.0.0/4"),     // Multicast
+		netip.MustParsePrefix("240.0.0.0/4"),     // Reserved (includes broadcast / 255.255.255.255)
+	}
+)
+
+// ValidateAddr will parse a netip.AddrPort from string, and return the result of ValidateIP() on addr.
+func ValidateAddr(s string) bool {
+	ipport, err := netip.ParseAddrPort(s)
+	if err != nil {
+		return false
+	}
+	return ValidateIP(ipport.Addr())
+}
+
+// ValidateIP returns whether IP is an IPv4/6 address in non-reserved, public ranges.
+func ValidateIP(ip netip.Addr) bool {
+	switch {
+	// IPv4: check if IPv4 in reserved nets
+	case ip.Is4():
+		for _, reserved := range IPv4Reserved {
+			if reserved.Contains(ip) {
+				return false
+			}
+		}
+		return true
+
+	// IPv6: check if in global unicast (public internet)
+	case ip.Is6():
+		return IPv6GlobalUnicast.Contains(ip)
+
+	// Assume malicious by default
+	default:
+		return false
+	}
+}