From 8972cd64904d445b27bfb7efd083f1d3bc5bbf29 Mon Sep 17 00:00:00 2001
From: alalamav <2132122+alalamav@users.noreply.github.com>
Date: Thu, 31 Jan 2019 15:03:05 -0500
Subject: [PATCH] Restrict access to the server's private networks (#14)

---
 net/private_net.go      | 43 ++++++++++++++++++++++++++++++++++++++
 net/private_net_test.go | 46 +++++++++++++++++++++++++++++++++++++++++
 shadowsocks/tcp.go      |  3 +++
 shadowsocks/udp.go      |  3 +++
 4 files changed, 95 insertions(+)
 create mode 100644 net/private_net.go
 create mode 100644 net/private_net_test.go

diff --git a/net/private_net.go b/net/private_net.go
new file mode 100644
index 00000000..e8c21a71
--- /dev/null
+++ b/net/private_net.go
@@ -0,0 +1,43 @@
+// Copyright 2019 Jigsaw Operations LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package net
+
+import "net"
+
+var privateNetworks []*net.IPNet
+
+func init() {
+	for _, cidr := range []string{
+		// RFC 1918: private IPv4 networks
+		"10.0.0.0/8",
+		"172.16.0.0/12",
+		"192.168.0.0/16",
+		// RFC 4193: IPv6 ULAs
+		"fc00::/7",
+	} {
+		_, subnet, _ := net.ParseCIDR(cidr)
+		privateNetworks = append(privateNetworks, subnet)
+	}
+}
+
+// IsPrivateAddress returns whether an IP address belongs to the LAN.
+func IsPrivateAddress(ip net.IP) bool {
+	for _, network := range privateNetworks {
+		if network.Contains(ip) {
+			return true
+		}
+	}
+	return false
+}
diff --git a/net/private_net_test.go b/net/private_net_test.go
new file mode 100644
index 00000000..795e91a1
--- /dev/null
+++ b/net/private_net_test.go
@@ -0,0 +1,46 @@
+// Copyright 2019 Jigsaw Operations LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package net
+
+import (
+	"net"
+	"testing"
+)
+
+var privateAddressTests = []struct {
+	address  string
+	expected bool
+}{
+	{"10.0.2.11", true},
+	{"172.16.1.2", true},
+	{"172.32.0.0", false},
+	{"192.168.0.23", true},
+	{"192.169.1.1", false},
+	{"127.0.0.1", false},
+	{"8.8.8.8", false},
+	{"::", false},
+	{"fd66:f83a:c650::1", true},
+	{"fde4:8dba:82e1::", true},
+	{"fe::123", false},
+}
+
+func TestIsLanAddress(t *testing.T) {
+	for _, tt := range privateAddressTests {
+		actual := IsPrivateAddress(net.ParseIP(tt.address))
+		if actual != tt.expected {
+			t.Errorf("IsLanAddress(%s): expected %t, actual %t", tt.address, tt.expected, actual)
+		}
+	}
+}
diff --git a/shadowsocks/tcp.go b/shadowsocks/tcp.go
index 9e1d6415..fe07a5ce 100644
--- a/shadowsocks/tcp.go
+++ b/shadowsocks/tcp.go
@@ -128,6 +128,9 @@ func proxyConnection(clientConn onet.DuplexConn, proxyMetrics *metrics.ProxyMetr
 	if !tgtTCPAddr.IP.IsGlobalUnicast() {
 		return onet.NewConnectionError("ERR_ADDRESS_INVALID", fmt.Sprintf("Target address is not global unicast: %v", tgtAddr.String()), err)
 	}
+	if onet.IsPrivateAddress(tgtTCPAddr.IP) {
+		return onet.NewConnectionError("ERR_ADDRESS_PRIVATE", fmt.Sprintf("Target address is a private address: %v", tgtAddr.String()), nil)
+	}
 
 	tgtTCPConn, err := net.DialTCP("tcp", nil, tgtTCPAddr)
 	if err != nil {
diff --git a/shadowsocks/udp.go b/shadowsocks/udp.go
index fe120761..fa491bb8 100644
--- a/shadowsocks/udp.go
+++ b/shadowsocks/udp.go
@@ -140,6 +140,9 @@ func (s *udpService) Start() {
 			if !tgtUDPAddr.IP.IsGlobalUnicast() {
 				return onet.NewConnectionError("ERR_ADDRESS_INVALID", fmt.Sprintf("Target address is not global unicast: %v", tgtAddr.String()), err)
 			}
+			if onet.IsPrivateAddress(tgtUDPAddr.IP) {
+				return onet.NewConnectionError("ERR_ADDRESS_PRIVATE", fmt.Sprintf("Target address is a private address: %v", tgtAddr.String()), nil)
+			}
 
 			payload := buf[len(tgtAddr):]