Add TLS fragment support

common/tlsfragment/index.go

@@ -0,0 +1,131 @@
+package tf
+
+import (
+	"encoding/binary"
+)
+
+const (
+	recordLayerHeaderLen    int    = 5
+	handshakeHeaderLen      int    = 6
+	randomDataLen           int    = 32
+	sessionIDHeaderLen      int    = 1
+	cipherSuiteHeaderLen    int    = 2
+	compressMethodHeaderLen int    = 1
+	extensionsHeaderLen     int    = 2
+	extensionHeaderLen      int    = 4
+	sniExtensionHeaderLen   int    = 5
+	contentType             uint8  = 22
+	handshakeType           uint8  = 1
+	sniExtensionType        uint16 = 0
+	sniNameDNSHostnameType  uint8  = 0
+	tlsVersionBitmask       uint16 = 0xFFFC
+	tls13                   uint16 = 0x0304
+)
+
+type myServerName struct {
+	Index      int
+	Length     int
+	ServerName string
+}
+
+func indexTLSServerName(payload []byte) *myServerName {
+	if len(payload) < recordLayerHeaderLen || payload[0] != contentType {
+		return nil
+	}
+	segmentLen := binary.BigEndian.Uint16(payload[3:5])
+	if len(payload) < recordLayerHeaderLen+int(segmentLen) {
+		return nil
+	}
+	serverName := indexTLSServerNameFromHandshake(payload[recordLayerHeaderLen : recordLayerHeaderLen+int(segmentLen)])
+	if serverName == nil {
+		return nil
+	}
+	serverName.Length += recordLayerHeaderLen
+	return serverName
+}
+
+func indexTLSServerNameFromHandshake(hs []byte) *myServerName {
+	if len(hs) < handshakeHeaderLen+randomDataLen+sessionIDHeaderLen {
+		return nil
+	}
+	if hs[0] != handshakeType {
+		return nil
+	}
+	handshakeLen := uint32(hs[1])<<16 | uint32(hs[2])<<8 | uint32(hs[3])
+	if len(hs[4:]) != int(handshakeLen) {
+		return nil
+	}
+	tlsVersion := uint16(hs[4])<<8 | uint16(hs[5])
+	if tlsVersion&tlsVersionBitmask != 0x0300 && tlsVersion != tls13 {
+		return nil
+	}
+	sessionIDLen := hs[38]
+	if len(hs) < handshakeHeaderLen+randomDataLen+sessionIDHeaderLen+int(sessionIDLen) {
+		return nil
+	}
+	cs := hs[handshakeHeaderLen+randomDataLen+sessionIDHeaderLen+int(sessionIDLen):]
+	if len(cs) < cipherSuiteHeaderLen {
+		return nil
+	}
+	csLen := uint16(cs[0])<<8 | uint16(cs[1])
+	if len(cs) < cipherSuiteHeaderLen+int(csLen)+compressMethodHeaderLen {
+		return nil
+	}
+	compressMethodLen := uint16(cs[cipherSuiteHeaderLen+int(csLen)])
+	if len(cs) < cipherSuiteHeaderLen+int(csLen)+compressMethodHeaderLen+int(compressMethodLen) {
+		return nil
+	}
+	currentIndex := cipherSuiteHeaderLen + int(csLen) + compressMethodHeaderLen + int(compressMethodLen)
+	serverName := indexTLSServerNameFromExtensions(cs[currentIndex:])
+	if serverName == nil {
+		return nil
+	}
+	serverName.Index += currentIndex
+	return serverName
+}
+
+func indexTLSServerNameFromExtensions(exs []byte) *myServerName {
+	if len(exs) == 0 {
+		return nil
+	}
+	if len(exs) < extensionsHeaderLen {
+		return nil
+	}
+	exsLen := uint16(exs[0])<<8 | uint16(exs[1])
+	exs = exs[extensionsHeaderLen:]
+	if len(exs) < int(exsLen) {
+		return nil
+	}
+	for currentIndex := extensionsHeaderLen; len(exs) > 0; {
+		if len(exs) < extensionHeaderLen {
+			return nil
+		}
+		exType := uint16(exs[0])<<8 | uint16(exs[1])
+		exLen := uint16(exs[2])<<8 | uint16(exs[3])
+		if len(exs) < extensionHeaderLen+int(exLen) {
+			return nil
+		}
+		sex := exs[extensionHeaderLen : extensionHeaderLen+int(exLen)]
+
+		switch exType {
+		case sniExtensionType:
+			if len(sex) < sniExtensionHeaderLen {
+				return nil
+			}
+			sniType := sex[2]
+			if sniType != sniNameDNSHostnameType {
+				return nil
+			}
+			sniLen := uint16(sex[3])<<8 | uint16(sex[4])
+			sex = sex[sniExtensionHeaderLen:]
+			return &myServerName{
+				Index:      currentIndex + extensionHeaderLen + sniExtensionHeaderLen,
+				Length:     int(sniLen),
+				ServerName: string(sex),
+			}
+		}
+		exs = exs[4+exLen:]
+		currentIndex += 4 + int(exLen)
+	}
+	return nil
+}