Add WireGuard analyzer (#41)

* feat: add WireGuard analyzer

* chore(wg): reduce map creating for non wg packets

* chore: import format

* docs: add wg usage

---------

Co-authored-by: Toby <tobyxdd@gmail.com>

README.ja.md

@@ -16,7 +16,7 @@ OpenGFW は、Linux 上の [GFW](https://en.wikipedia.org/wiki/Great_Firewall)
 ## 特徴
 
 - フル IP/TCP 再アセンブル、各種プロトコルアナライザー
-  - HTTP、TLS、DNS、SSH、SOCKS4/5、その他多数
+  - HTTP、TLS、DNS、SSH、SOCKS4/5、WireGuard、その他多数
   - Shadowsocks の"完全に暗号化されたトラフィック"の検出、
     など。 (https://gfw.report/publications/usenixsecurity23/data/paper/paper.pdf)
   - トロイの木馬キラー (https://github.com/XTLS/Trojan-killer) に基づくトロイの木馬 (プロキシプロトコル) 検出
@@ -104,6 +104,10 @@ workers:
   action: block
   expr: string(socks?.req?.addr) endsWith "google.com" && socks?.req?.port == 80
 
+- name: block wireguard by handshake response
+  action: drop
+  expr: wireguard?.handshake_response?.receiver_index_matched == true
+
 - name: block bilibili geosite
   action: block
   expr: geosite(string(tls?.req?.sni), "bilibili")

README.md

@@ -20,7 +20,7 @@ Linux that's in many ways more powerful than the real thing. It's cyber sovereig
 ## Features
 
 - Full IP/TCP reassembly, various protocol analyzers
-  - HTTP, TLS, DNS, SSH, SOCKS4/5, and many more to come
+  - HTTP, TLS, DNS, SSH, SOCKS4/5, WireGuard, and many more to come
   - "Fully encrypted traffic" detection for Shadowsocks,
     etc. (https://gfw.report/publications/usenixsecurity23/data/paper/paper.pdf)
   - Trojan (proxy protocol) detection based on Trojan-killer (https://github.com/XTLS/Trojan-killer)
@@ -108,6 +108,10 @@ to [Expr Language Definition](https://expr-lang.org/docs/language-definition).
   action: block
   expr: string(socks?.req?.addr) endsWith "google.com" && socks?.req?.port == 80
 
+- name: block wireguard by handshake response
+  action: drop
+  expr: wireguard?.handshake_response?.receiver_index_matched == true
+
 - name: block bilibili geosite
   action: block
   expr: geosite(string(tls?.req?.sni), "bilibili")

README.zh.md

@@ -17,7 +17,7 @@ OpenGFW 是一个 Linux 上灵活、易用、开源的 [GFW](https://zh.wikipedi
 ## 功能
 
 - 完整的 IP/TCP 重组，各种协议解析器
-  - HTTP, TLS, DNS, SSH, SOCKS4/5, 更多协议正在开发中
+  - HTTP, TLS, DNS, SSH, SOCKS4/5, WireGuard, 更多协议正在开发中
   - Shadowsocks 等 "全加密流量" 检测 (https://gfw.report/publications/usenixsecurity23/data/paper/paper.pdf)
   - 基于 Trojan-killer 的 Trojan 检测 (https://github.com/XTLS/Trojan-killer)
   - [开发中] 基于机器学习的流量分类
@@ -103,6 +103,10 @@ workers:
   action: block
   expr: string(socks?.req?.addr) endsWith "google.com" && socks?.req?.port == 80
 
+- name: block wireguard by handshake response
+  action: drop
+  expr: wireguard?.handshake_response?.receiver_index_matched == true
+
 - name: block bilibili geosite
   action: block
   expr: geosite(string(tls?.req?.sni), "bilibili")

analyzer/udp/wireguard.go

@@ -0,0 +1,217 @@
+package udp
+
+import (
+	"container/ring"
+	"encoding/binary"
+	"slices"
+	"sync"
+
+	"github.com/apernet/OpenGFW/analyzer"
+)
+
+var (
+	_ analyzer.UDPAnalyzer = (*WireGuardAnalyzer)(nil)
+	_ analyzer.UDPStream   = (*wireGuardUDPStream)(nil)
+)
+
+const (
+	wireguardUDPInvalidCountThreshold = 4
+	wireguardRememberedIndexCount     = 6
+	wireguardPropKeyMessageType       = "message_type"
+)
+
+const (
+	wireguardTypeHandshakeInitiation = 1
+	wireguardTypeHandshakeResponse   = 2
+	wireguardTypeData                = 4
+	wireguardTypeCookieReply         = 3
+)
+
+const (
+	wireguardSizeHandshakeInitiation = 148
+	wireguardSizeHandshakeResponse   = 92
+	wireguardMinSizePacketData       = 32 // 16 bytes header + 16 bytes AEAD overhead
+	wireguardSizePacketCookieReply   = 64
+)
+
+type WireGuardAnalyzer struct{}
+
+func (a *WireGuardAnalyzer) Name() string {
+	return "wireguard"
+}
+
+func (a *WireGuardAnalyzer) Limit() int {
+	return 0
+}
+
+func (a *WireGuardAnalyzer) NewUDP(info analyzer.UDPInfo, logger analyzer.Logger) analyzer.UDPStream {
+	return newWireGuardUDPStream(logger)
+}
+
+type wireGuardUDPStream struct {
+	logger                analyzer.Logger
+	invalidCount          int
+	rememberedIndexes     *ring.Ring
+	rememberedIndexesLock sync.RWMutex
+}
+
+func newWireGuardUDPStream(logger analyzer.Logger) *wireGuardUDPStream {
+	return &wireGuardUDPStream{
+		logger:            logger,
+		rememberedIndexes: ring.New(wireguardRememberedIndexCount),
+	}
+}
+
+func (s *wireGuardUDPStream) Feed(rev bool, data []byte) (u *analyzer.PropUpdate, done bool) {
+	m := s.parseWireGuardPacket(rev, data)
+	if m == nil {
+		s.invalidCount++
+		return nil, s.invalidCount >= wireguardUDPInvalidCountThreshold
+	}
+	s.invalidCount = 0 // Reset invalid count on valid WireGuard packet
+	messageType := m[wireguardPropKeyMessageType].(byte)
+	propUpdateType := analyzer.PropUpdateMerge
+	if messageType == wireguardTypeHandshakeInitiation {
+		propUpdateType = analyzer.PropUpdateReplace
+	}
+	return &analyzer.PropUpdate{
+		Type: propUpdateType,
+		M:    m,
+	}, false
+}
+
+func (s *wireGuardUDPStream) Close(limited bool) *analyzer.PropUpdate {
+	return nil
+}
+
+func (s *wireGuardUDPStream) parseWireGuardPacket(rev bool, data []byte) analyzer.PropMap {
+	if len(data) < 4 {
+		return nil
+	}
+	if slices.Max(data[1:4]) != 0 {
+		return nil
+	}
+
+	messageType := data[0]
+	var propKey string
+	var propValue analyzer.PropMap
+	switch messageType {
+	case wireguardTypeHandshakeInitiation:
+		propKey = "handshake_initiation"
+		propValue = s.parseWireGuardHandshakeInitiation(rev, data)
+	case wireguardTypeHandshakeResponse:
+		propKey = "handshake_response"
+		propValue = s.parseWireGuardHandshakeResponse(rev, data)
+	case wireguardTypeData:
+		propKey = "packet_data"
+		propValue = s.parseWireGuardPacketData(rev, data)
+	case wireguardTypeCookieReply:
+		propKey = "packet_cookie_reply"
+		propValue = s.parseWireGuardPacketCookieReply(rev, data)
+	}
+	if propValue == nil {
+		return nil
+	}
+
+	m := make(analyzer.PropMap)
+	m[wireguardPropKeyMessageType] = messageType
+	m[propKey] = propValue
+	return m
+}
+
+func (s *wireGuardUDPStream) parseWireGuardHandshakeInitiation(rev bool, data []byte) analyzer.PropMap {
+	if len(data) != wireguardSizeHandshakeInitiation {
+		return nil
+	}
+	m := make(analyzer.PropMap)
+
+	senderIndex := binary.LittleEndian.Uint32(data[4:8])
+	m["sender_index"] = senderIndex
+	s.putSenderIndex(rev, senderIndex)
+
+	return m
+}
+
+func (s *wireGuardUDPStream) parseWireGuardHandshakeResponse(rev bool, data []byte) analyzer.PropMap {
+	if len(data) != wireguardSizeHandshakeResponse {
+		return nil
+	}
+	m := make(analyzer.PropMap)
+
+	senderIndex := binary.LittleEndian.Uint32(data[4:8])
+	m["sender_index"] = senderIndex
+	s.putSenderIndex(rev, senderIndex)
+
+	receiverIndex := binary.LittleEndian.Uint32(data[8:12])
+	m["receiver_index"] = receiverIndex
+	m["receiver_index_matched"] = s.matchReceiverIndex(rev, receiverIndex)
+
+	return m
+}
+
+func (s *wireGuardUDPStream) parseWireGuardPacketData(rev bool, data []byte) analyzer.PropMap {
+	if len(data) < wireguardMinSizePacketData {
+		return nil
+	}
+	if len(data)%16 != 0 {
+		// WireGuard zero padding the packet to make the length a multiple of 16
+		return nil
+	}
+	m := make(analyzer.PropMap)
+
+	receiverIndex := binary.LittleEndian.Uint32(data[4:8])
+	m["receiver_index"] = receiverIndex
+	m["receiver_index_matched"] = s.matchReceiverIndex(rev, receiverIndex)
+
+	m["counter"] = binary.LittleEndian.Uint64(data[8:16])
+
+	return m
+}
+
+func (s *wireGuardUDPStream) parseWireGuardPacketCookieReply(rev bool, data []byte) analyzer.PropMap {
+	if len(data) != wireguardSizePacketCookieReply {
+		return nil
+	}
+	m := make(analyzer.PropMap)
+
+	receiverIndex := binary.LittleEndian.Uint32(data[4:8])
+	m["receiver_index"] = receiverIndex
+	m["receiver_index_matched"] = s.matchReceiverIndex(rev, receiverIndex)
+
+	return m
+}
+
+type wireGuardIndex struct {
+	SenderIndex uint32
+	Reverse     bool
+}
+
+func (s *wireGuardUDPStream) putSenderIndex(rev bool, senderIndex uint32) {
+	s.rememberedIndexesLock.Lock()
+	defer s.rememberedIndexesLock.Unlock()
+
+	s.rememberedIndexes.Value = &wireGuardIndex{
+		SenderIndex: senderIndex,
+		Reverse:     rev,
+	}
+	s.rememberedIndexes = s.rememberedIndexes.Prev()
+}
+
+func (s *wireGuardUDPStream) matchReceiverIndex(rev bool, receiverIndex uint32) bool {
+	s.rememberedIndexesLock.RLock()
+	defer s.rememberedIndexesLock.RUnlock()
+
+	var found bool
+	ris := s.rememberedIndexes
+	for it := ris.Next(); it != ris; it = it.Next() {
+		if it.Value == nil {
+			break
+		}
+		wgidx := it.Value.(*wireGuardIndex)
+		if wgidx.Reverse == !rev && wgidx.SenderIndex == receiverIndex {
+			found = true
+			break
+		}
+	}
+	return found
+}

cmd/root.go

@@ -92,6 +92,7 @@ var analyzers = []analyzer.Analyzer{
 	&tcp.TLSAnalyzer{},
 	&tcp.TrojanAnalyzer{},
 	&udp.DNSAnalyzer{},
+	&udp.WireGuardAnalyzer{},
 }
 
 var modifiers = []modifier.Modifier{

docs/Analyzers.md

@@ -369,3 +369,54 @@ Example for blocking connections to `google.com:80` and user `foobar`:
   action: block
   expr: socks?.req?.auth?.method == 2 && socks?.req?.auth?.username == "foobar"
 ```
+
+
+## WireGuard
+
+```json5
+{
+  "wireguard": {
+    "message_type": 1, // 0x1: handshake_initiation, 0x2: handshake_response, 0x3: packet_cookie_reply, 0x4: packet_data
+    "handshake_initiation": {
+      "sender_index": 0x12345678
+    },
+    "handshake_response": {
+      "sender_index": 0x12345678,
+      "receiver_index": 0x87654321,
+      "receiver_index_matched": true
+    },
+    "packet_data": {
+      "receiver_index": 0x12345678,
+      "receiver_index_matched": true
+    },
+    "packet_cookie_reply": {
+      "receiver_index": 0x12345678,
+      "receiver_index_matched": true
+    }
+  }
+}
+```
+
+Example for blocking WireGuard traffic:
+
+```yaml
+# false positive: high
+- name: Block all WireGuard-like traffic
+  action: block
+  expr: wireguard != nil
+
+# false positive: medium
+- name: Block WireGuard by handshake_initiation
+  action: drop
+  expr: wireguard?.handshake_initiation != nil
+
+# false positive: low
+- name: Block WireGuard by handshake_response
+  action: drop
+  expr: wireguard?.handshake_response?.receiver_index_matched == true
+
+# false positive: pretty low
+- name: Block WireGuard by packet_data
+  action: block
+  expr: wireguard?.packet_data?.receiver_index_matched == true
+```