add WebRTC and IPCAM wire formats, encrypt shim header, simulate DTLS

Security fixes: - Encrypt shim header inside AES-GCM (eliminates 0x5C10ADED fingerprint) - XOR magic with session-derived mask when AES disabled - Unified encode/decode path via wire.go New wire formats: - webrtc: SRTP-style 24B RTP header with 0xBEDE extensions (abs-send-time, transport-cc), 10B auth tag, compound RTCP SR+SDES, STUN with FINGERPRINT - ipcam: H.264/RTP surveillance camera simulation with FU-A fragmentation, STAP-A SPS/PPS, GOP state machine (I/P frames) DTLS handshake simulation: - Fake DTLS 1.2 ClientHello/ServerHello/ChangeCipherSpec/Finished - Realistic cipher suites, use_srtp extension, supported_groups DPI score improvement: 34.6 -> 70.4 (webrtc+AES mode)
2026-08-29 08:49:44 +00:00 · 2026-04-08 15:55:56 +08:00
parent 8852bb7976
commit 8b001daf0a
6 changed files with 1380 additions and 111 deletions
@@ -0,0 +1,226 @@
+package main
+
+import (
+	"context"
+	cryptoRand "crypto/rand"
+	"encoding/binary"
+	"errors"
+	"hash/crc32"
+	"io"
+	"math/rand"
+	"net"
+	"sync/atomic"
+	"time"
+)
+
+func buildWebRTCRTPHeader(seq uint16, ts uint32, pt uint8, marker bool, ssrc uint32, absTime uint32, twccSeq uint16) []byte {
+	b := make([]byte, 24)
+	b[0] = 0x90 // V=2, X=1
+	b[1] = pt
+	if marker {
+		b[1] |= 0x80
+	}
+	binary.BigEndian.PutUint16(b[2:4], seq)
+	binary.BigEndian.PutUint32(b[4:8], ts)
+	binary.BigEndian.PutUint32(b[8:12], ssrc)
+	binary.BigEndian.PutUint16(b[12:14], 0xBEDE)
+	binary.BigEndian.PutUint16(b[14:16], 0x0002)
+	b[16] = 0x32 // id=3, len=2 (abs-send-time)
+	b[17] = byte(absTime >> 16)
+	b[18] = byte(absTime >> 8)
+	b[19] = byte(absTime)
+	b[20] = 0x51 // id=5, len=1 (transport-cc)
+	binary.BigEndian.PutUint16(b[21:23], twccSeq)
+	b[23] = 0x00 // padding
+	return b
+}
+
+func appendSRTPAuthTag(packet []byte) []byte {
+	tag := make([]byte, 10)
+	_, _ = cryptoRand.Read(tag)
+	return append(packet, tag...)
+}
+
+func stripWebRTCRTP(b []byte) (pt uint8, marker bool, rest []byte, err error) {
+	if len(b) < 24+10 {
+		return 0, false, nil, io.ErrUnexpectedEOF
+	}
+	if (b[0]>>6)&0x3 != 2 {
+		return 0, false, nil, errors.New("rtp ver")
+	}
+	marker = (b[1] & 0x80) != 0
+	pt = b[1] & 0x7F
+	rest = b[24 : len(b)-10]
+	return pt, marker, rest, nil
+}
+
+type audioState struct {
+	seq     uint16
+	ts      uint32
+	ssrc    uint32
+	twccSeq *uint32
+}
+
+func (a *audioState) buildAudioPacket() []byte {
+	twcc := uint16(atomic.AddUint32(a.twccSeq, 1))
+	now := time.Now()
+	sec := uint32(uint64(now.Unix()) + ntpEpochOffset)
+	frac := uint32(uint64(now.Nanosecond()) * (1 << 18) / 1_000_000_000)
+	absTime := (sec << 18) | frac
+
+	h := buildWebRTCRTPHeader(a.seq, a.ts, 111, true, a.ssrc, absTime, twcc)
+	a.seq++
+	a.ts += 960
+
+	payloadLen := 80 + rand.Intn(41) // 80-120
+	payload := make([]byte, payloadLen)
+	_, _ = cryptoRand.Read(payload)
+
+	pkt := append(h, payload...)
+	return appendSRTPAuthTag(pkt)
+}
+
+func buildCompoundRTCP(ssrc uint32, rtpTs uint32, pktCount uint32, octCount uint32) []byte {
+	now := time.Now()
+	sec := uint32(uint64(now.Unix()) + ntpEpochOffset)
+	frac := uint32(uint64(now.Nanosecond()) * (1 << 32) / 1_000_000_000)
+
+	// SR: 28 bytes
+	sr := make([]byte, 28)
+	sr[0] = 0x80 // V=2, P=0, RC=0
+	sr[1] = 200  // SR
+	binary.BigEndian.PutUint16(sr[2:4], 6)
+	binary.BigEndian.PutUint32(sr[4:8], ssrc)
+	binary.BigEndian.PutUint32(sr[8:12], sec)
+	binary.BigEndian.PutUint32(sr[12:16], frac)
+	binary.BigEndian.PutUint32(sr[16:20], rtpTs)
+	binary.BigEndian.PutUint32(sr[20:24], pktCount)
+	binary.BigEndian.PutUint32(sr[24:28], octCount)
+
+	// SDES: CNAME = "{hex-ssrc}@webrtc.local"
+	cname := []byte(hexSSRC(ssrc) + "@webrtc.local")
+	// SDES header(4) + SSRC(4) + CNAME item(2+len) + END(1) + padding
+	sdesPayload := make([]byte, 0, 4+len(cname)+3)
+	sdesPayload = append(sdesPayload, byte(ssrc>>24), byte(ssrc>>16), byte(ssrc>>8), byte(ssrc))
+	sdesPayload = append(sdesPayload, 1, byte(len(cname)))
+	sdesPayload = append(sdesPayload, cname...)
+	sdesPayload = append(sdesPayload, 0x00) // END
+	for len(sdesPayload)%4 != 0 {
+		sdesPayload = append(sdesPayload, 0x00)
+	}
+
+	sdesHdr := make([]byte, 4)
+	sdesHdr[0] = 0x81 // V=2, SC=1
+	sdesHdr[1] = 202  // SDES
+	binary.BigEndian.PutUint16(sdesHdr[2:4], uint16(len(sdesPayload)/4))
+
+	compound := append(sr, sdesHdr...)
+	compound = append(compound, sdesPayload...)
+
+	// SRTCP index (E-flag set, index=0)
+	idx := make([]byte, 4)
+	idx[0] = 0x80 // E-flag
+	compound = append(compound, idx...)
+
+	return appendSRTPAuthTag(compound)
+}
+
+func hexSSRC(ssrc uint32) string {
+	b := make([]byte, 4)
+	binary.BigEndian.PutUint32(b, ssrc)
+	const hex = "0123456789abcdef"
+	out := make([]byte, 8)
+	for i := 0; i < 4; i++ {
+		out[i*2] = hex[b[i]>>4]
+		out[i*2+1] = hex[b[i]&0x0f]
+	}
+	return string(out)
+}
+
+func stunCRC32(data []byte) uint32 {
+	return crc32.ChecksumIEEE(data) ^ 0x5354554E
+}
+
+func buildSTUNBindingRequestFull() []byte {
+	b := make([]byte, 28)
+	binary.BigEndian.PutUint16(b[0:2], 0x0001) // Binding Request
+	binary.BigEndian.PutUint16(b[2:4], 8)       // length: FINGERPRINT attr (8 bytes)
+	binary.BigEndian.PutUint32(b[4:8], 0x2112A442)
+	_, _ = cryptoRand.Read(b[8:20])
+
+	// FINGERPRINT attribute
+	binary.BigEndian.PutUint16(b[20:22], 0x8028) // type
+	binary.BigEndian.PutUint16(b[22:24], 4)       // length
+	fp := stunCRC32(b[:20])
+	binary.BigEndian.PutUint32(b[24:28], fp)
+	return b
+}
+
+func buildSTUNBindingResponse(transactionID []byte) []byte {
+	b := make([]byte, 44)
+	binary.BigEndian.PutUint16(b[0:2], 0x0101) // Binding Success Response
+	binary.BigEndian.PutUint16(b[2:4], 24)      // length: XOR-MAPPED-ADDRESS(12) + FINGERPRINT(8)
+	binary.BigEndian.PutUint32(b[4:8], 0x2112A442)
+	copy(b[8:20], transactionID)
+
+	// XOR-MAPPED-ADDRESS
+	binary.BigEndian.PutUint16(b[20:22], 0x0020) // type
+	binary.BigEndian.PutUint16(b[22:24], 8)       // length
+	b[24] = 0x00                                   // reserved
+	b[25] = 0x01                                   // IPv4
+	binary.BigEndian.PutUint16(b[26:28], 0x2112^0xD903) // XOR'd port
+	binary.BigEndian.PutUint32(b[28:32], 0x2112A442^0xC0A80101) // XOR'd 192.168.1.1
+
+	// FINGERPRINT
+	binary.BigEndian.PutUint16(b[32:34], 0x8028)
+	binary.BigEndian.PutUint16(b[34:36], 4)
+	fp := stunCRC32(b[:32])
+	binary.BigEndian.PutUint32(b[36:40], fp)
+
+	// pad remaining
+	return b[:40]
+}
+
+func runAudioTicker(ctx context.Context, conn *net.UDPConn, peer *net.UDPAddr, audio *audioState, tb *tokenBucket, pcap *pcapWriter) {
+	ticker := time.NewTicker(20 * time.Millisecond)
+	defer ticker.Stop()
+
+	localAddr := conn.LocalAddr().(*net.UDPAddr)
+	srcIP := ip4OrLoopback(localAddr.IP)
+	dstIP := ip4OrLoopback(peer.IP)
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			jitter := time.Duration(rand.Intn(4000)-2000) * time.Microsecond
+			time.Sleep(jitter)
+
+			pkt := audio.buildAudioPacket()
+			tb.wait(len(pkt) + 28)
+			_, _ = conn.WriteToUDP(pkt, peer)
+			pcap.WriteUDP(srcIP, localAddr.Port, dstIP, peer.Port, pkt)
+		}
+	}
+}
+
+func runSTUNConsent(ctx context.Context, conn *net.UDPConn, peer *net.UDPAddr, pcap *pcapWriter) {
+	localAddr := conn.LocalAddr().(*net.UDPAddr)
+	srcIP := ip4OrLoopback(localAddr.IP)
+	dstIP := ip4OrLoopback(peer.IP)
+
+	for {
+		jitter := time.Duration(rand.Intn(2000)-1000) * time.Millisecond
+		wait := 5*time.Second + jitter
+
+		select {
+		case <-ctx.Done():
+			return
+		case <-time.After(wait):
+			req := buildSTUNBindingRequestFull()
+			_, _ = conn.WriteToUDP(req, peer)
+			pcap.WriteUDP(srcIP, localAddr.Port, dstIP, peer.Port, req)
+		}
+	}
+}