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https://github.com/apernet/OpenGFW.git
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Merge pull request #114 from KujouRinka/feat-openvpn
feat: add openVPN analyzer
This commit is contained in:
Toby
GitHub
commit
ab28fc238d
384
analyzer/udp/openvpn.go
Normal file
384
analyzer/udp/openvpn.go
Normal file
@ -0,0 +1,384 @@
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package udp
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import (
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"github.com/apernet/OpenGFW/analyzer"
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"github.com/apernet/OpenGFW/analyzer/utils"
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)
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var (
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_ analyzer.UDPAnalyzer = (*OpenVPNAnalyzer)(nil)
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_ analyzer.TCPAnalyzer = (*OpenVPNAnalyzer)(nil)
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)
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var (
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_ analyzer.UDPStream = (*openvpnUDPStream)(nil)
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_ analyzer.TCPStream = (*openvpnTCPStream)(nil)
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)
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// Ref paper:
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// https://www.usenix.org/system/files/sec22fall_xue-diwen.pdf
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// OpenVPN Opcodes definitions from:
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// https://github.com/OpenVPN/openvpn/blob/master/src/openvpn/ssl_pkt.h
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const (
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OpenVPNControlHardResetClientV1 = 1
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OpenVPNControlHardResetServerV1 = 2
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OpenVPNControlSoftResetV1 = 3
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OpenVPNControlV1 = 4
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OpenVPNAckV1 = 5
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OpenVPNDataV1 = 6
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OpenVPNControlHardResetClientV2 = 7
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OpenVPNControlHardResetServerV2 = 8
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OpenVPNDataV2 = 9
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OpenVPNControlHardResetClientV3 = 10
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OpenVPNControlWkcV1 = 11
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)
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const (
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OpenVPNMinPktLen = 6
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OpenVPNTCPPktDefaultLimit = 256
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OpenVPNUDPPktDefaultLimit = 256
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)
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type OpenVPNAnalyzer struct{}
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func (a *OpenVPNAnalyzer) Name() string {
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return "openvpn"
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}
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func (a *OpenVPNAnalyzer) Limit() int {
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return 0
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}
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func (a *OpenVPNAnalyzer) NewUDP(info analyzer.UDPInfo, logger analyzer.Logger) analyzer.UDPStream {
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return newOpenVPNUDPStream(logger)
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}
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func (a *OpenVPNAnalyzer) NewTCP(info analyzer.TCPInfo, logger analyzer.Logger) analyzer.TCPStream {
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return newOpenVPNTCPStream(logger)
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}
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type openvpnPkt struct {
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pktLen uint16 // 16 bits, TCP proto only
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opcode byte // 5 bits
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_keyId byte // 3 bits, not used
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// We don't care about the rest of the packet
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// payload []byte
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}
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type openvpnStream struct {
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logger analyzer.Logger
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reqUpdated bool
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reqLSM *utils.LinearStateMachine
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reqDone bool
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respUpdated bool
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respLSM *utils.LinearStateMachine
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respDone bool
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rxPktCnt int
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txPktCnt int
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pktLimit int
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reqPktParse func() (*openvpnPkt, utils.LSMAction)
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respPktParse func() (*openvpnPkt, utils.LSMAction)
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lastOpcode byte
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}
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func (o *openvpnStream) parseCtlHardResetClient() utils.LSMAction {
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pkt, action := o.reqPktParse()
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if action != utils.LSMActionNext {
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return action
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}
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if pkt.opcode != OpenVPNControlHardResetClientV1 &&
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pkt.opcode != OpenVPNControlHardResetClientV2 &&
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pkt.opcode != OpenVPNControlHardResetClientV3 {
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return utils.LSMActionCancel
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}
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o.lastOpcode = pkt.opcode
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return utils.LSMActionNext
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}
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func (o *openvpnStream) parseCtlHardResetServer() utils.LSMAction {
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if o.lastOpcode != OpenVPNControlHardResetClientV1 &&
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o.lastOpcode != OpenVPNControlHardResetClientV2 &&
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o.lastOpcode != OpenVPNControlHardResetClientV3 {
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return utils.LSMActionCancel
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}
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pkt, action := o.respPktParse()
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if action != utils.LSMActionNext {
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return action
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}
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if pkt.opcode != OpenVPNControlHardResetServerV1 &&
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pkt.opcode != OpenVPNControlHardResetServerV2 {
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return utils.LSMActionCancel
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}
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o.lastOpcode = pkt.opcode
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return utils.LSMActionNext
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}
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func (o *openvpnStream) parseReq() utils.LSMAction {
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pkt, action := o.reqPktParse()
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if action != utils.LSMActionNext {
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return action
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}
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if pkt.opcode != OpenVPNControlSoftResetV1 &&
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pkt.opcode != OpenVPNControlV1 &&
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pkt.opcode != OpenVPNAckV1 &&
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pkt.opcode != OpenVPNDataV1 &&
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pkt.opcode != OpenVPNDataV2 &&
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pkt.opcode != OpenVPNControlWkcV1 {
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return utils.LSMActionCancel
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}
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o.txPktCnt += 1
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o.reqUpdated = true
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return utils.LSMActionPause
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}
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func (o *openvpnStream) parseResp() utils.LSMAction {
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pkt, action := o.respPktParse()
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if action != utils.LSMActionNext {
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return action
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}
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if pkt.opcode != OpenVPNControlSoftResetV1 &&
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pkt.opcode != OpenVPNControlV1 &&
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pkt.opcode != OpenVPNAckV1 &&
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pkt.opcode != OpenVPNDataV1 &&
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pkt.opcode != OpenVPNDataV2 &&
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pkt.opcode != OpenVPNControlWkcV1 {
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return utils.LSMActionCancel
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}
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o.rxPktCnt += 1
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o.respUpdated = true
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return utils.LSMActionPause
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}
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type openvpnUDPStream struct {
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openvpnStream
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curPkt []byte
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// We don't introduce `invalidCount` here to decrease the false positive rate
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// invalidCount int
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}
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func newOpenVPNUDPStream(logger analyzer.Logger) *openvpnUDPStream {
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s := &openvpnUDPStream{
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openvpnStream: openvpnStream{
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logger: logger,
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pktLimit: OpenVPNUDPPktDefaultLimit,
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},
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}
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s.respPktParse = s.parsePkt
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s.reqPktParse = s.parsePkt
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s.reqLSM = utils.NewLinearStateMachine(
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s.parseCtlHardResetClient,
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s.parseReq,
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)
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s.respLSM = utils.NewLinearStateMachine(
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s.parseCtlHardResetServer,
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s.parseResp,
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)
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return s
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}
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func (o *openvpnUDPStream) Feed(rev bool, data []byte) (u *analyzer.PropUpdate, d bool) {
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if len(data) == 0 {
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return nil, false
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}
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var update *analyzer.PropUpdate
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var cancelled bool
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o.curPkt = data
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if rev {
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o.respUpdated = false
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cancelled, o.respDone = o.respLSM.Run()
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if o.respUpdated {
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update = &analyzer.PropUpdate{
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Type: analyzer.PropUpdateReplace,
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M: analyzer.PropMap{"rx_pkt_cnt": o.rxPktCnt, "tx_pkt_cnt": o.txPktCnt},
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}
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o.respUpdated = false
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}
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} else {
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o.reqUpdated = false
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cancelled, o.reqDone = o.reqLSM.Run()
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if o.reqUpdated {
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update = &analyzer.PropUpdate{
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Type: analyzer.PropUpdateReplace,
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M: analyzer.PropMap{"rx_pkt_cnt": o.rxPktCnt, "tx_pkt_cnt": o.txPktCnt},
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}
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o.reqUpdated = false
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}
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}
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return update, cancelled || (o.reqDone && o.respDone) || o.rxPktCnt+o.txPktCnt > o.pktLimit
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}
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func (o *openvpnUDPStream) Close(limited bool) *analyzer.PropUpdate {
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return nil
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}
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// Parse OpenVPN UDP packet.
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func (o *openvpnUDPStream) parsePkt() (p *openvpnPkt, action utils.LSMAction) {
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if o.curPkt == nil {
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return nil, utils.LSMActionPause
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}
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if !OpenVPNCheckForValidOpcode(o.curPkt[0] >> 3) {
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return nil, utils.LSMActionCancel
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}
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// Parse packet header
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p = &openvpnPkt{}
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p.opcode = o.curPkt[0] >> 3
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p._keyId = o.curPkt[0] & 0x07
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o.curPkt = nil
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return p, utils.LSMActionNext
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}
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type openvpnTCPStream struct {
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openvpnStream
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reqBuf *utils.ByteBuffer
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respBuf *utils.ByteBuffer
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}
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func newOpenVPNTCPStream(logger analyzer.Logger) *openvpnTCPStream {
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s := &openvpnTCPStream{
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openvpnStream: openvpnStream{
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logger: logger,
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pktLimit: OpenVPNTCPPktDefaultLimit,
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},
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reqBuf: &utils.ByteBuffer{},
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respBuf: &utils.ByteBuffer{},
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}
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s.respPktParse = func() (*openvpnPkt, utils.LSMAction) {
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return s.parsePkt(true)
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}
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s.reqPktParse = func() (*openvpnPkt, utils.LSMAction) {
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return s.parsePkt(false)
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}
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s.reqLSM = utils.NewLinearStateMachine(
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s.parseCtlHardResetClient,
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s.parseReq,
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)
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s.respLSM = utils.NewLinearStateMachine(
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s.parseCtlHardResetServer,
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s.parseResp,
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)
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return s
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}
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func (o *openvpnTCPStream) Feed(rev, start, end bool, skip int, data []byte) (u *analyzer.PropUpdate, d bool) {
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if skip != 0 {
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return nil, true
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}
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if len(data) == 0 {
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return nil, false
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}
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var update *analyzer.PropUpdate
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var cancelled bool
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if rev {
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o.respBuf.Append(data)
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o.respUpdated = false
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cancelled, o.respDone = o.respLSM.Run()
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if o.respUpdated {
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update = &analyzer.PropUpdate{
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Type: analyzer.PropUpdateReplace,
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M: analyzer.PropMap{"rx_pkt_cnt": o.rxPktCnt, "tx_pkt_cnt": o.txPktCnt},
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}
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o.respUpdated = false
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}
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} else {
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o.reqBuf.Append(data)
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o.reqUpdated = false
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cancelled, o.reqDone = o.reqLSM.Run()
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if o.reqUpdated {
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update = &analyzer.PropUpdate{
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Type: analyzer.PropUpdateMerge,
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M: analyzer.PropMap{"rx_pkt_cnt": o.rxPktCnt, "tx_pkt_cnt": o.txPktCnt},
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}
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o.reqUpdated = false
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}
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}
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return update, cancelled || (o.reqDone && o.respDone) || o.rxPktCnt+o.txPktCnt > o.pktLimit
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}
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func (o *openvpnTCPStream) Close(limited bool) *analyzer.PropUpdate {
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o.reqBuf.Reset()
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o.respBuf.Reset()
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return nil
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}
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// Parse OpenVPN TCP packet.
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func (o *openvpnTCPStream) parsePkt(rev bool) (p *openvpnPkt, action utils.LSMAction) {
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var buffer *utils.ByteBuffer
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if rev {
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buffer = o.respBuf
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} else {
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buffer = o.reqBuf
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}
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// Parse packet length
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pktLen, ok := buffer.GetUint16(false, false)
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if !ok {
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return nil, utils.LSMActionPause
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}
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if pktLen < OpenVPNMinPktLen {
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return nil, utils.LSMActionCancel
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}
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pktOp, ok := buffer.Get(3, false)
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if !ok {
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return nil, utils.LSMActionPause
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}
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if !OpenVPNCheckForValidOpcode(pktOp[2] >> 3) {
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return nil, utils.LSMActionCancel
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}
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pkt, ok := buffer.Get(int(pktLen)+2, true)
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if !ok {
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return nil, utils.LSMActionPause
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}
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pkt = pkt[2:]
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// Parse packet header
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p = &openvpnPkt{}
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p.pktLen = pktLen
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p.opcode = pkt[0] >> 3
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p._keyId = pkt[0] & 0x07
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return p, utils.LSMActionNext
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}
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func OpenVPNCheckForValidOpcode(opcode byte) bool {
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switch opcode {
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case OpenVPNControlHardResetClientV1,
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OpenVPNControlHardResetServerV1,
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OpenVPNControlSoftResetV1,
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OpenVPNControlV1,
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OpenVPNAckV1,
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OpenVPNDataV1,
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OpenVPNControlHardResetClientV2,
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OpenVPNControlHardResetServerV2,
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OpenVPNDataV2,
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OpenVPNControlHardResetClientV3,
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OpenVPNControlWkcV1:
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return true
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}
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return false
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}
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@ -92,6 +92,7 @@ var analyzers = []analyzer.Analyzer{
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&tcp.TLSAnalyzer{},
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&tcp.TrojanAnalyzer{},
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&udp.DNSAnalyzer{},
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&udp.OpenVPNAnalyzer{},
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&udp.QUICAnalyzer{},
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&udp.WireGuardAnalyzer{},
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}
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