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datapath_udp.go
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datapath_udp.go
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package nfqdatapath
// Go libraries
import (
"fmt"
"net"
"strconv"
"strings"
"time"
"go.aporeto.io/trireme-lib/collector"
"go.aporeto.io/trireme-lib/controller/constants"
enforcerconstants "go.aporeto.io/trireme-lib/controller/internal/enforcer/constants"
"go.aporeto.io/trireme-lib/controller/pkg/claimsheader"
"go.aporeto.io/trireme-lib/controller/pkg/connection"
"go.aporeto.io/trireme-lib/controller/pkg/packet"
"go.aporeto.io/trireme-lib/controller/pkg/pucontext"
"go.aporeto.io/trireme-lib/controller/pkg/tokens"
"go.uber.org/zap"
)
const (
// Default retransmit delay for first packet
retransmitDelay = 200
// rentrasmitRetries is the number of times we will retry
retransmitRetries = 3
)
// ProcessNetworkUDPPacket processes packets arriving from network and are destined to the application.
func (d *Datapath) ProcessNetworkUDPPacket(p *packet.Packet) (conn *connection.UDPConnection, err error) {
if d.packetLogs {
zap.L().Debug("Processing network packet ",
zap.String("flow", p.L4FlowHash()),
)
defer zap.L().Debug("Finished Processing network packet ",
zap.String("flow", p.L4FlowHash()),
zap.Error(err),
)
}
// First we must recover the connection for the packet.
//var
udpPacketType := p.GetUDPType()
zap.L().Debug("Got packet of type:", zap.Reflect("Type", udpPacketType), zap.Reflect("Len", len(p.Buffer)))
switch udpPacketType {
case packet.UDPSynMask:
conn, err = d.netSynUDPRetrieveState(p)
if err != nil {
if d.packetLogs {
zap.L().Debug("Packet rejected",
zap.String("flow", p.L4FlowHash()),
zap.Error(err),
)
}
return nil, err
}
case packet.UDPSynAckMask:
conn, err = d.netSynAckUDPRetrieveState(p)
if err != nil {
if d.packetLogs {
zap.L().Debug("Syn ack Packet Rejected/ignored",
zap.String("flow", p.L4FlowHash()),
)
}
return nil, err
}
case packet.UDPAckMask:
conn, err = d.netUDPAckRetrieveState(p)
if err != nil {
if d.packetLogs {
zap.L().Debug("Packet rejected",
zap.String("flow", p.L4FlowHash()),
zap.Error(err),
)
}
return nil, err
}
default:
// Process packets that don't have the control header. These are data packets.
conn, err = d.netUDPAckRetrieveState(p)
if err != nil {
if d.packetLogs {
zap.L().Debug("No connection found for the flow, Dropping it",
zap.String("flow", p.L4FlowHash()),
zap.Error(err),
)
}
return nil, err
}
}
// We are processing only one connection at a time.
conn.Lock()
defer conn.Unlock()
p.Print(packet.PacketStageIncoming)
if d.service != nil {
if !d.service.PreProcessUDPNetPacket(p, conn.Context, conn) {
p.Print(packet.PacketFailureService)
return conn, fmt.Errorf("pre processing failed for network packet")
}
}
// handle handshake packets and do not deliver to application.
action, claims, err := d.processNetUDPPacket(p, conn.Context, conn)
if err != nil {
if d.packetLogs {
zap.L().Debug("Rejecting packet ",
zap.String("flow", p.L4FlowHash()),
zap.Error(err),
)
}
return conn, fmt.Errorf("packet processing failed for network packet: %s", err)
}
// Process the packet by any external services.
if d.service != nil {
if !d.service.PostProcessUDPNetPacket(p, action, claims, conn.Context, conn) {
p.Print(packet.PacketFailureService)
return conn, fmt.Errorf("post service processing failed for network packet")
}
}
// If reached the final state, drain the queue.
if conn.GetState() == connection.UDPClientSendAck {
conn.SetState(connection.UDPData)
zap.L().Debug("Draining the queue of application packets")
for udpPacket := conn.ReadPacket(); udpPacket != nil; udpPacket = conn.ReadPacket() {
if d.service != nil {
// PostProcessServiceInterface
// We call it for all outgoing packets.
if !d.service.PostProcessUDPAppPacket(udpPacket, nil, conn.Context, conn) {
udpPacket.Print(packet.PacketFailureService)
zap.L().Error("Failed to encrypt queued packet")
}
}
err = d.udpSocketWriter.WriteSocket(udpPacket.Buffer)
if err != nil {
zap.L().Error("Unable to transmit Queued UDP packets", zap.Error(err))
}
}
return conn, fmt.Errorf("Drop the packet")
}
if conn.GetState() != connection.UDPData {
// handshake packets are not to be delivered to application.
return conn, fmt.Errorf("Drop net hanshake packets (udp)")
}
return conn, nil
}
func (d *Datapath) netSynUDPRetrieveState(p *packet.Packet) (*connection.UDPConnection, error) {
// Retrieve the context from the packet information.
context, err := d.contextFromIP(false, p.Mark, p.DestinationPort, packet.IPProtocolUDP)
if err != nil {
return nil, err
}
// Check if a connection already exists for this flow. This can happen
// in the case of retransmissions. If there is no connection, create
// a new one.
conn, cerr := d.udpNetOrigConnectionTracker.Get(p.L4FlowHash())
if cerr != nil {
return connection.NewUDPConnection(context, d.udpSocketWriter), nil
}
return conn.(*connection.UDPConnection), nil
}
func (d *Datapath) netSynAckUDPRetrieveState(p *packet.Packet) (*connection.UDPConnection, error) {
conn, err := d.udpSourcePortConnectionCache.GetReset(p.SourcePortHash(packet.PacketTypeNetwork), 0)
if err != nil {
return nil, fmt.Errorf("No connection.Drop the syn ack packet")
}
return conn.(*connection.UDPConnection), nil
}
func (d *Datapath) netUDPAckRetrieveState(p *packet.Packet) (*connection.UDPConnection, error) {
hash := p.L4FlowHash()
conn, err := d.udpNetReplyConnectionTracker.GetReset(hash, 0)
if err != nil {
conn, err = d.udpNetOrigConnectionTracker.GetReset(hash, 0)
if err != nil {
return nil, fmt.Errorf("net state not found: %s", err)
}
}
return conn.(*connection.UDPConnection), nil
}
// processNetUDPPacket processes a network UDP packet and dispatches it to different methods based on the flags.
// This applies only to control packets.
func (d *Datapath) processNetUDPPacket(udpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.UDPConnection) (action interface{}, claims *tokens.ConnectionClaims, err error) {
// Extra check, just in case the caller didn't provide a connection.
if conn == nil {
return nil, nil, fmt.Errorf("no connection provided")
}
udpPacketType := udpPacket.GetUDPType()
// Update connection state in the internal state machine tracker
switch udpPacketType {
case packet.UDPSynMask:
// Parse the packet for the identity information.
action, claims, err = d.processNetworkUDPSynPacket(context, conn, udpPacket)
if err != nil {
return nil, nil, err
}
// Send the return packet.
if err = d.sendUDPSynAckPacket(udpPacket, context, conn); err != nil {
return nil, nil, err
}
// Mark the state that we have transmitted a SynAck packet.
conn.SetState(connection.UDPReceiverSendSynAck)
return action, claims, nil
case packet.UDPAckMask:
// Retrieve the header and parse the signatures.
if err = d.processNetworkUDPAckPacket(udpPacket, context, conn); err != nil {
zap.L().Error("Error during authorization", zap.Error(err))
return nil, nil, err
}
// Set the connection to
conn.SetState(connection.UDPReceiverProcessedAck)
return nil, nil, nil
case packet.UDPSynAckMask:
// Process the synack header and claims of the other side.
action, claims, err = d.processNetworkUDPSynAckPacket(udpPacket, context, conn)
if err != nil {
zap.L().Error("UDP Syn ack failed with", zap.Error(err))
return nil, nil, err
}
// Send back the acknowledgement.
err = d.sendUDPAckPacket(udpPacket, context, conn)
if err != nil {
zap.L().Error("Unable to send udp Syn ack failed", zap.Error(err))
return nil, nil, err
}
conn.SetState(connection.UDPClientSendAck)
return action, claims, nil
default:
state := conn.GetState()
if state == connection.UDPReceiverProcessedAck || state == connection.UDPClientSendAck || state == connection.UDPData {
conn.SetState(connection.UDPData)
return nil, nil, nil
}
return nil, nil, fmt.Errorf("Invalid packet")
}
}
// ProcessApplicationUDPPacket processes packets arriving from an application and are destined to the network
func (d *Datapath) ProcessApplicationUDPPacket(p *packet.Packet) (conn *connection.UDPConnection, err error) {
if d.packetLogs {
zap.L().Debug("Processing application UDP packet ",
zap.String("flow", p.L4FlowHash()),
)
defer zap.L().Debug("Finished Processing UDP application packet ",
zap.String("flow", p.L4FlowHash()),
zap.Error(err),
)
}
// First retrieve the connection state.
conn, err = d.appUDPRetrieveState(p)
if err != nil {
zap.L().Debug("Connection not found", zap.Error(err))
return nil, fmt.Errorf("Received packet from unenforced process: %s", err)
}
// We are processing only one packet from a given connection at a time.
conn.Lock()
defer conn.Unlock()
// do some pre processing.
if d.service != nil {
// PreProcessServiceInterface
if !d.service.PreProcessUDPAppPacket(p, conn.Context, conn, packet.UDPSynMask) {
p.Print(packet.PacketFailureService)
return nil, fmt.Errorf("pre service processing failed for UDP application packet")
}
}
drop := false
switch conn.GetState() {
case connection.UDPStart:
// Queue the packet. We will send it after we authorize the session.
if err = conn.QueuePackets(p); err != nil {
return conn, fmt.Errorf("Unable to queue packets:%s", err)
}
// Process the application packet.
err = d.processApplicationUDPSynPacket(p, conn.Context, conn)
if err != nil {
return conn, fmt.Errorf("Unable to send UDP Syn packet: %s", err)
}
// Set the state indicating that we send out a Syn packet
conn.SetState(connection.UDPClientSendSyn)
// Drop the packet. We stored it in the queue.
drop = true
case connection.UDPReceiverProcessedAck, connection.UDPClientSendAck, connection.UDPData:
conn.SetState(connection.UDPData)
default:
zap.L().Debug("Packet is added to the queue", zap.String("flow", p.L4FlowHash()))
if err = conn.QueuePackets(p); err != nil {
return conn, fmt.Errorf("Unable to queue packets:%s", err)
}
// Drop the packet. We stored it in the queue.
drop = true
}
if d.service != nil {
// PostProcessServiceInterface
if !d.service.PostProcessUDPAppPacket(p, nil, conn.Context, conn) {
p.Print(packet.PacketFailureService)
return conn, fmt.Errorf("Encryption failed for application packet")
}
}
if drop {
return conn, fmt.Errorf("Drop in nfq - buffered")
}
return conn, nil
}
func (d *Datapath) appUDPRetrieveState(p *packet.Packet) (*connection.UDPConnection, error) {
hash := p.L4FlowHash()
if conn, err := d.udpAppReplyConnectionTracker.GetReset(hash, 0); err == nil {
return conn.(*connection.UDPConnection), nil
}
if conn, err := d.udpAppOrigConnectionTracker.GetReset(hash, 0); err == nil {
return conn.(*connection.UDPConnection), nil
}
context, err := d.contextFromIP(true, p.Mark, p.SourcePort, packet.IPProtocolUDP)
if err != nil {
return nil, fmt.Errorf("No context in app processing")
}
return connection.NewUDPConnection(context, d.udpSocketWriter), nil
}
// processApplicationUDPSynPacket processes a single Syn Packet
func (d *Datapath) processApplicationUDPSynPacket(udpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.UDPConnection) (err error) {
if !addressMatch(udpPacket.DestinationAddress, context.UDPNetworks()) {
d.reportUDPExternalFlow(udpPacket, context, true, nil, nil)
return fmt.Errorf("No target found")
}
udpOptions := d.CreateUDPAuthMarker(packet.UDPSynMask)
udpData, err := d.tokenAccessor.CreateSynPacketToken(context, &conn.Auth)
if err != nil {
return err
}
newPacket, err := d.clonePacketHeaders(udpPacket)
if err != nil {
return fmt.Errorf("Unable to clone packet: %s", err)
}
// Attach the UDP data and token
newPacket.UDPTokenAttach(udpOptions, udpData)
// send packet
// err = d.udpSocketWriter.WriteSocket(newPacket.Buffer)
err = d.writeWithRetransmit(newPacket.Buffer, conn.SynChannel())
if err != nil {
zap.L().Error("Unable to send syn token on raw socket", zap.Error(err))
return fmt.Errorf("unable to transmit syn packet")
}
// Poplate the caches to track the connection
hash := udpPacket.L4FlowHash()
d.udpAppOrigConnectionTracker.AddOrUpdate(hash, conn)
d.udpSourcePortConnectionCache.AddOrUpdate(newPacket.SourcePortHash(packet.PacketTypeApplication), conn)
d.udpNatConnectionTracker.AddOrUpdate(newPacket.SourcePortHash(packet.PacketTypeApplication), newPacket.SourcePortHash(packet.PacketTypeNetwork))
// Attach the tags to the packet and accept the packet
return nil
}
func (d *Datapath) writeWithRetransmit(buffer []byte, stop chan bool) error {
localBuffer := make([]byte, len(buffer))
copy(localBuffer, buffer)
if err := d.udpSocketWriter.WriteSocket(localBuffer); err != nil {
zap.L().Error("Failed to write control packet to socket", zap.Error(err))
return err
}
go func() {
for retries := 0; retries < retransmitRetries; retries++ {
delay := time.Millisecond * time.Duration((retransmitDelay * (retries + 1)))
select {
case <-stop:
return
case <-time.After(delay):
if err := d.udpSocketWriter.WriteSocket(localBuffer); err != nil {
zap.L().Error("Failed to write control packet to socket", zap.Error(err))
}
}
}
}()
return nil
}
func (d *Datapath) clonePacketHeaders(p *packet.Packet) (*packet.Packet, error) {
// copy the ip and udp headers.
newPacket := make([]byte, packet.UDPDataPos)
p.FixupIPHdrOnDataModify(p.IPTotalLength, packet.UDPDataPos)
_ = copy(newPacket, p.Buffer[:packet.UDPDataPos])
return packet.New(packet.PacketTypeApplication, newPacket, p.Mark, true)
}
// CreateUDPAuthMarker creates a UDP auth marker.
func (d *Datapath) CreateUDPAuthMarker(packetType uint8) []byte {
// Every UDP control packet has a 20 byte packet signature. The
// first 2 bytes represent the following control information.
// Byte 0 : Bits 0,1 are reserved fields.
// Bits 2,3,4 represent version information.
// Bits 5, 6 represent udp packet type,
// Bit 7 represents encryption. (currently unused).
// Byte 1: reserved for future use.
// Bytes [2:20]: Packet signature.
marker := make([]byte, packet.UDPSignatureLen)
// ignore version info as of now.
marker[0] |= packetType // byte 0
marker[1] = 0 // byte 1
// byte 2 - 19
copy(marker[2:], []byte(packet.UDPAuthMarker))
return marker
}
// sendUDPSynAckPacket processes a UDP SynAck packet
func (d *Datapath) sendUDPSynAckPacket(udpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.UDPConnection) (err error) {
// Create UDP Option
udpOptions := d.CreateUDPAuthMarker(packet.UDPSynAckMask)
udpData, err := d.tokenAccessor.CreateSynAckPacketToken(context, &conn.Auth, claimsheader.NewClaimsHeader())
if err != nil {
return err
}
udpPacket.CreateReverseFlowPacket(udpPacket.SourceAddress, udpPacket.SourcePort)
// Attach the UDP data and token
udpPacket.UDPTokenAttach(udpOptions, udpData)
// If we have already a backgroun re-transmit session, stop it at this point. We will
// start from the beginning.
if conn.GetState() == connection.UDPReceiverSendSynAck {
conn.SynAckStop()
}
// Only start the retransmission timer once. Not on every packet.
if err := d.writeWithRetransmit(udpPacket.Buffer, conn.SynAckChannel()); err != nil {
zap.L().Debug("Unable to send synack token on raw socket", zap.Error(err))
return err
}
return nil
}
func (d *Datapath) sendUDPAckPacket(udpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.UDPConnection) (err error) {
// Create UDP Option
zap.L().Debug("Sending UDP Ack packet", zap.String("flow", udpPacket.L4ReverseFlowHash()))
udpOptions := d.CreateUDPAuthMarker(packet.UDPAckMask)
udpData, err := d.tokenAccessor.CreateAckPacketToken(context, &conn.Auth)
if err != nil {
return err
}
srcPortHash, err := d.udpNatConnectionTracker.GetReset(udpPacket.SourcePortHash(packet.PacketTypeNetwork), 0)
if err != nil {
return fmt.Errorf("error getting actual destination")
}
destIPPort := srcPortHash.(string)
destIP := strings.Split(destIPPort, ":")[0]
destPort, err := (strconv.Atoi(strings.Split(destIPPort, ":")[1]))
if err != nil {
return fmt.Errorf("Unable to get dest port from cache")
}
udpPacket.CreateReverseFlowPacket(net.ParseIP(destIP), uint16(destPort))
// Attach the UDP data and token
udpPacket.UDPTokenAttach(udpOptions, udpData)
// send packet
err = d.udpSocketWriter.WriteSocket(udpPacket.Buffer)
if err != nil {
zap.L().Debug("Unable to send ack token on raw socket", zap.Error(err))
return err
}
if !conn.ServiceConnection {
zap.L().Debug("Plumbing the conntrack (app) rule for flow", zap.String("flow", udpPacket.L4FlowHash()))
if err = d.conntrackHdl.ConntrackTableUpdateMark(
destIP,
udpPacket.SourceAddress.String(),
udpPacket.IPProto,
uint16(destPort),
udpPacket.SourcePort,
constants.DefaultConnMark,
); err != nil {
zap.L().Error("Failed to update conntrack table for flow",
zap.String("context", string(conn.Auth.LocalContext)),
zap.String("app-conn", udpPacket.L4FlowHash()),
zap.String("state", fmt.Sprintf("%d", conn.GetState())),
zap.Error(err),
)
}
}
return nil
}
// processNetworkUDPSynPacket processes a syn packet arriving from the network
func (d *Datapath) processNetworkUDPSynPacket(context *pucontext.PUContext, conn *connection.UDPConnection, udpPacket *packet.Packet) (action interface{}, claims *tokens.ConnectionClaims, err error) {
claims, err = d.tokenAccessor.ParsePacketToken(&conn.Auth, udpPacket.ReadUDPToken())
if err != nil {
d.reportUDPRejectedFlow(udpPacket, conn, collector.DefaultEndPoint, context.ManagementID(), context, tokens.CodeFromErr(err), nil, nil, false)
return nil, nil, fmt.Errorf("UDP Syn packet dropped because of invalid token: %s", err)
}
// if there are no claims we must drop the connection and we drop the Syn
// packet. The source will retry but we have no state to maintain here.
if claims == nil {
d.reportUDPRejectedFlow(udpPacket, conn, collector.DefaultEndPoint, context.ManagementID(), context, collector.InvalidToken, nil, nil, false)
return nil, nil, fmt.Errorf("UDP Syn packet dropped because of no claims")
}
// Why is this required. Take a look.
txLabel, _ := claims.T.Get(enforcerconstants.TransmitterLabel)
// Add the port as a label with an @ prefix. These labels are invalid otherwise
// If all policies are restricted by port numbers this will allow port-specific policies
claims.T.AppendKeyValue(enforcerconstants.PortNumberLabelString, strconv.Itoa(int(udpPacket.DestinationPort)))
report, pkt := context.SearchRcvRules(claims.T)
if pkt.Action.Rejected() {
d.reportUDPRejectedFlow(udpPacket, conn, txLabel, context.ManagementID(), context, collector.PolicyDrop, report, pkt, false)
return nil, nil, fmt.Errorf("connection rejected because of policy: %s", claims.T.String())
}
hash := udpPacket.L4FlowHash()
// conntrack
d.udpNetOrigConnectionTracker.AddOrUpdate(hash, conn)
d.udpAppReplyConnectionTracker.AddOrUpdate(udpPacket.L4ReverseFlowHash(), conn)
// Record actions
conn.ReportFlowPolicy = report
conn.PacketFlowPolicy = pkt
return pkt, claims, nil
}
func (d *Datapath) processNetworkUDPSynAckPacket(udpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.UDPConnection) (action interface{}, claims *tokens.ConnectionClaims, err error) {
conn.SynStop()
// Packets that have authorization information go through the auth path
// Decode the JWT token using the context key
claims, err = d.tokenAccessor.ParsePacketToken(&conn.Auth, udpPacket.ReadUDPToken())
if err != nil {
d.reportUDPRejectedFlow(udpPacket, nil, collector.DefaultEndPoint, context.ManagementID(), context, collector.MissingToken, nil, nil, true)
return nil, nil, fmt.Errorf("SynAck packet dropped because of bad claims: %s", err)
}
if claims == nil {
d.reportUDPRejectedFlow(udpPacket, nil, collector.DefaultEndPoint, context.ManagementID(), context, collector.MissingToken, nil, nil, true)
return nil, nil, fmt.Errorf("SynAck packet dropped because of no claims")
}
report, pkt := context.SearchTxtRules(claims.T, !d.mutualAuthorization)
if pkt.Action.Rejected() {
d.reportUDPRejectedFlow(udpPacket, conn, context.ManagementID(), conn.Auth.RemoteContextID, context, collector.PolicyDrop, report, pkt, true)
return nil, nil, fmt.Errorf("dropping because of reject rule on transmitter: %s", claims.T.String())
}
// conntrack
d.udpNetReplyConnectionTracker.AddOrUpdate(udpPacket.L4FlowHash(), conn)
return pkt, claims, nil
}
func (d *Datapath) processNetworkUDPAckPacket(udpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.UDPConnection) (err error) {
conn.SynAckStop()
_, err = d.tokenAccessor.ParseAckToken(&conn.Auth, udpPacket.ReadUDPToken())
if err != nil {
d.reportUDPRejectedFlow(udpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, collector.PolicyDrop, conn.ReportFlowPolicy, conn.PacketFlowPolicy, false)
return fmt.Errorf("ack packet dropped because signature validation failed: %s", err)
}
if !conn.ServiceConnection {
zap.L().Debug("Plumb conntrack rule for flow:", zap.String("flow", udpPacket.L4FlowHash()))
// Plumb connmark rule here.
if err := d.conntrackHdl.ConntrackTableUpdateMark(
udpPacket.DestinationAddress.String(),
udpPacket.SourceAddress.String(),
udpPacket.IPProto,
udpPacket.DestinationPort,
udpPacket.SourcePort,
constants.DefaultConnMark,
); err != nil {
zap.L().Error("Failed to update conntrack table after ack packet")
}
}
d.reportUDPAcceptedFlow(udpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, conn.ReportFlowPolicy, conn.PacketFlowPolicy, false)
return nil
}