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datapath_tcp.go
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datapath_tcp.go
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package nfqdatapath
// Go libraries
import (
"fmt"
"strconv"
"github.com/mdlayher/netlink"
"github.com/pkg/errors"
"go.aporeto.io/trireme-lib/collector"
"go.aporeto.io/trireme-lib/common"
"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.aporeto.io/trireme-lib/policy"
"go.aporeto.io/trireme-lib/utils/cache"
"go.uber.org/zap"
)
var errInvalidState = errors.New("Invalid State")
var errInvalidNetState = errors.New("Invalid net state")
var errNonPUTraffic = errors.New("Traffic belongs to a PU we are not monitoring")
var errNetSynNotSeen = errors.New("Network Syn packet was not seen")
var errNoConnFound = errors.New("no context or connection found")
// processNetworkPackets processes packets arriving from network and are destined to the application
func (d *Datapath) processNetworkTCPPackets(p *packet.Packet) (conn *connection.TCPConnection, err error) {
if d.packetLogs {
zap.L().Debug("Processing network packet ",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
)
defer zap.L().Debug("Finished Processing network packet ",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
zap.Error(err),
)
}
//var conn *connection.TCPConnection
// Retrieve connection state of SynAck packets and
// skip processing for SynAck packets that we don't have state
switch p.TCPFlags & packet.TCPSynAckMask {
case packet.TCPSynMask:
conn, err = d.netSynRetrieveState(p)
if err != nil {
switch err {
// Non PU Traffic let it through
case errNonPUTraffic:
return conn, nil
default:
if d.packetLogs {
zap.L().Debug("Packet rejected",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
zap.Error(err),
)
}
return conn, err
}
}
case packet.TCPSynAckMask:
conn, err = d.netSynAckRetrieveState(p)
if err != nil {
// This packet belongs to the client process that is not being enforcerd.
// At this point, we can release this flow to kernel as we are not interested in
// enforcing policy for the flow.
d.releaseUnmonitoredFlow(p)
return conn, nil
}
default:
conn, err = d.netRetrieveState(p)
if err != nil {
if d.packetLogs {
zap.L().Debug("Packet rejected",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
zap.Error(err),
)
}
return conn, err
}
}
conn.Lock()
defer conn.Unlock()
p.Print(packet.PacketStageIncoming)
if d.service != nil {
if !d.service.PreProcessTCPNetPacket(p, conn.Context, conn) {
p.Print(packet.PacketFailureService)
return conn, errors.New("pre service processing failed for network packet")
}
}
p.Print(packet.PacketStageAuth)
// Match the tags of the packet against the policy rules - drop if the lookup fails
action, claims, err := d.processNetworkTCPPacket(p, conn.Context, conn)
if err != nil {
p.Print(packet.PacketFailureAuth)
if d.packetLogs {
zap.L().Debug("Rejecting packet ",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
zap.Error(err),
)
}
return conn, fmt.Errorf("packet processing failed for network packet: %s", err)
}
p.Print(packet.PacketStageService)
if d.service != nil {
// PostProcessServiceInterface
if !d.service.PostProcessTCPNetPacket(p, action, claims, conn.Context, conn) {
p.Print(packet.PacketFailureService)
return conn, errors.New("post service processing failed for network packet")
}
if conn.ServiceConnection && conn.TimeOut > 0 {
d.netReplyConnectionTracker.SetTimeOut(p.L4FlowHash(), conn.TimeOut) // nolint
}
}
// Accept the packet
p.UpdateTCPChecksum()
p.Print(packet.PacketStageOutgoing)
return conn, nil
}
// processApplicationPackets processes packets arriving from an application and are destined to the network
func (d *Datapath) processApplicationTCPPackets(p *packet.Packet) (conn *connection.TCPConnection, err error) {
if d.packetLogs {
zap.L().Debug("Processing application packet ",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
)
defer zap.L().Debug("Finished Processing application packet ",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
zap.Error(err),
)
}
switch p.TCPFlags & packet.TCPSynAckMask {
case packet.TCPSynMask:
conn, err = d.appSynRetrieveState(p)
if err != nil {
if d.packetLogs {
zap.L().Debug("Packet rejected",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
zap.Error(err),
)
}
return conn, err
}
case packet.TCPSynAckMask:
conn, err = d.appSynAckRetrieveState(p)
if err != nil {
if d.packetLogs {
zap.L().Debug("SynAckPacket Ignored",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
)
}
cid, err := d.contextIDFromTCPPort.GetSpecValueFromPort(p.SourcePort)
if err == nil {
item, err := d.puFromContextID.Get(cid.(string))
if err != nil {
// Let the packet through if the context is not found
return conn, nil
}
ctx := item.(*pucontext.PUContext)
// Syn was not seen and this synack packet is coming from a PU
// we monitor. This is possible only if IP is in the external
// networks or excluded networks. Let this packet go through
// for any of these cases. Drop for everything else.
_, policy, perr := ctx.NetworkACLPolicyFromAddr(p.DestinationAddress.To4(), p.SourcePort)
if perr == nil && policy.Action.Accepted() {
return conn, nil
}
// Drop this synack as it belongs to PU
// for which we didn't see syn
zap.L().Error("Network Syn was not seen, and we are monitoring this PU. Dropping the syn ack packet", zap.String("contextID", cid.(string)), zap.Uint16("port", p.SourcePort))
return conn, errNetSynNotSeen
}
// syn ack for non aporeto traffic can be let through
return conn, nil
}
default:
conn, err = d.appRetrieveState(p)
if err != nil {
if d.packetLogs {
zap.L().Debug("Packet rejected",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
zap.Error(err),
)
}
return conn, err
}
}
conn.Lock()
defer conn.Unlock()
p.Print(packet.PacketStageIncoming)
if d.service != nil {
// PreProcessServiceInterface
if !d.service.PreProcessTCPAppPacket(p, conn.Context, conn) {
p.Print(packet.PacketFailureService)
return conn, errors.New("pre service processing failed for application packet")
}
}
p.Print(packet.PacketStageAuth)
// Match the tags of the packet against the policy rules - drop if the lookup fails
action, err := d.processApplicationTCPPacket(p, conn.Context, conn)
if err != nil {
if d.packetLogs {
zap.L().Debug("Dropping packet ",
zap.String("flow", p.L4FlowHash()),
zap.String("Flags", packet.TCPFlagsToStr(p.TCPFlags)),
zap.Error(err),
)
}
p.Print(packet.PacketFailureAuth)
return conn, fmt.Errorf("processing failed for application packet: %s", err)
}
p.Print(packet.PacketStageService)
if d.service != nil {
// PostProcessServiceInterface
if !d.service.PostProcessTCPAppPacket(p, action, conn.Context, conn) {
p.Print(packet.PacketFailureService)
return conn, errors.New("post service processing failed for application packet")
}
}
// Accept the packet
p.UpdateTCPChecksum()
p.Print(packet.PacketStageOutgoing)
return conn, nil
}
// processApplicationTCPPacket processes a TCP packet and dispatches it to other methods based on the flags
func (d *Datapath) processApplicationTCPPacket(tcpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.TCPConnection) (interface{}, error) {
if conn == nil {
return nil, nil
}
// State machine based on the flags
switch tcpPacket.TCPFlags & packet.TCPSynAckMask {
case packet.TCPSynMask: //Processing SYN packet from Application
return d.processApplicationSynPacket(tcpPacket, context, conn)
case packet.TCPAckMask:
return nil, d.processApplicationAckPacket(tcpPacket, context, conn)
case packet.TCPSynAckMask:
return nil, d.processApplicationSynAckPacket(tcpPacket, context, conn)
default:
return nil, nil
}
}
// processApplicationSynPacket processes a single Syn Packet
func (d *Datapath) processApplicationSynPacket(tcpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.TCPConnection) (interface{}, error) {
// If the packet is not in target networks then look into the external services application cache to
// make a decision whether the packet should be forwarded. For target networks with external services
// network syn/ack accepts the packet if it belongs to external services.
_, pkt, perr := d.targetNetworks.GetMatchingAction(tcpPacket.DestinationAddress.To4(), tcpPacket.DestinationPort)
if perr != nil {
report, policy, perr := context.ApplicationACLPolicyFromAddr(tcpPacket.DestinationAddress.To4(), tcpPacket.DestinationPort)
if perr == nil && policy.Action.Accepted() {
return nil, nil
}
d.reportExternalServiceFlow(context, report, pkt, true, tcpPacket)
return nil, fmt.Errorf("No acls found for external services. Dropping application syn packet")
}
if policy, err := context.RetrieveCachedExternalFlowPolicy(tcpPacket.DestinationAddress.String() + ":" + strconv.Itoa(int(tcpPacket.DestinationPort))); err == nil {
d.appOrigConnectionTracker.AddOrUpdate(tcpPacket.L4FlowHash(), conn)
d.sourcePortConnectionCache.AddOrUpdate(tcpPacket.SourcePortHash(packet.PacketTypeApplication), conn)
return policy, nil
}
// We are now processing as a Trireme packet that needs authorization headers
// Create TCP Option
tcpOptions := d.createTCPAuthenticationOption([]byte{})
// Create a token
tcpData, err := d.tokenAccessor.CreateSynPacketToken(context, &conn.Auth)
if err != nil {
return nil, err
}
// Set the state indicating that we send out a Syn packet
conn.SetState(connection.TCPSynSend)
// Poplate the caches to track the connection
hash := tcpPacket.L4FlowHash()
d.appOrigConnectionTracker.AddOrUpdate(hash, conn)
d.sourcePortConnectionCache.AddOrUpdate(tcpPacket.SourcePortHash(packet.PacketTypeApplication), conn)
// Attach the tags to the packet and accept the packet
return nil, tcpPacket.TCPDataAttach(tcpOptions, tcpData)
}
// processApplicationSynAckPacket processes an application SynAck packet
func (d *Datapath) processApplicationSynAckPacket(tcpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.TCPConnection) error {
// if the traffic belongs to the same pu, let it go
if conn.GetState() == connection.TCPData && conn.IsLoopbackConnection() {
return nil
}
// If we are already in the connection.TCPData, it means that this is an external flow
// At this point we can release the flow to the kernel by updating conntrack
// We can also clean up the state since we are not going to see any more
// packets from this connection.
if conn.GetState() == connection.TCPData && !conn.ServiceConnection {
if err := d.conntrack.UpdateApplicationFlowMark(
tcpPacket.SourceAddress,
tcpPacket.DestinationAddress,
tcpPacket.IPProto,
tcpPacket.SourcePort,
tcpPacket.DestinationPort,
constants.DefaultConnMark,
); err != nil {
zap.L().Error("Failed to update conntrack entry for flow at SynAck packet",
zap.String("context", string(conn.Auth.LocalContext)),
zap.String("app-conn", tcpPacket.L4ReverseFlowHash()),
zap.String("state", fmt.Sprintf("%d", conn.GetState())),
)
}
err1 := d.netOrigConnectionTracker.Remove(tcpPacket.L4ReverseFlowHash())
err2 := d.appReplyConnectionTracker.Remove(tcpPacket.L4FlowHash())
if err1 != nil || err2 != nil {
zap.L().Debug("Failed to remove cache entries")
}
return nil
}
// We now process packets that need authorization options
// Create TCP Option
tcpOptions := d.createTCPAuthenticationOption([]byte{})
claimsHeader := claimsheader.NewClaimsHeader(
claimsheader.OptionEncrypt(conn.PacketFlowPolicy.Action.Encrypted()),
)
tcpData, err := d.tokenAccessor.CreateSynAckPacketToken(context, &conn.Auth, claimsHeader)
if err != nil {
return err
}
// Set the state for future reference
conn.SetState(connection.TCPSynAckSend)
// Attach the tags to the packet
return tcpPacket.TCPDataAttach(tcpOptions, tcpData)
}
// processApplicationAckPacket processes an application ack packet
func (d *Datapath) processApplicationAckPacket(tcpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.TCPConnection) error {
// Only process the first Ack of a connection. This means that we have received
// as SynAck packet and we can now process the ACK.
if conn.GetState() == connection.TCPSynAckReceived && tcpPacket.IsEmptyTCPPayload() {
// Create a new token that includes the source and destinatio nonse
// These are both challenges signed by the secret key and random for every
// connection minimizing the chances of a replay attack
token, err := d.tokenAccessor.CreateAckPacketToken(context, &conn.Auth)
if err != nil {
return err
}
tcpOptions := d.createTCPAuthenticationOption([]byte{})
// Attach the tags to the packet
if err := tcpPacket.TCPDataAttach(tcpOptions, token); err != nil {
return err
}
conn.SetState(connection.TCPAckSend)
// If its not a service connection, we release it to the kernel. Subsequent
// packets after the first data packet, that might be already in the queue
// will be transmitted through the kernel directly. Service connections are
// delegated to the service module
if !conn.ServiceConnection && tcpPacket.SourceAddress.String() != tcpPacket.DestinationAddress.String() &&
!(tcpPacket.SourceAddress.IsLoopback() && tcpPacket.DestinationAddress.IsLoopback()) {
if err := d.conntrack.UpdateApplicationFlowMark(
tcpPacket.SourceAddress,
tcpPacket.DestinationAddress,
tcpPacket.IPProto,
tcpPacket.SourcePort,
tcpPacket.DestinationPort,
constants.DefaultConnMark,
); err != nil {
zap.L().Error("Failed to update conntrack table for flow after ack packet",
zap.String("context", string(conn.Auth.LocalContext)),
zap.String("app-conn", tcpPacket.L4ReverseFlowHash()),
zap.String("state", fmt.Sprintf("%d", conn.GetState())),
)
}
}
return nil
}
// If we are already in the connection.TCPData connection just forward the packet
if conn.GetState() == connection.TCPData {
return nil
}
if conn.GetState() == connection.UnknownState {
// Check if the destination is in the external services approved cache
// and if yes, allow the packet to go and release the flow.
_, policy, perr := context.ApplicationACLPolicyFromAddr(tcpPacket.DestinationAddress.To4(), tcpPacket.DestinationPort)
if perr != nil {
// If it is an SSH PU, we let the connection go through
// It means it is a new SSH Session connection, we mark
// the packet and let it go through.
if context.Type() == common.SSHSessionPU {
if err := d.conntrack.UpdateApplicationFlowMark(
tcpPacket.SourceAddress,
tcpPacket.DestinationAddress,
tcpPacket.IPProto,
tcpPacket.SourcePort,
tcpPacket.DestinationPort,
constants.DefaultConnMark,
); err != nil {
zap.L().Error("Failed to update conntrack entry for flow at Ack packet",
zap.String("context", string(conn.Auth.LocalContext)),
zap.String("app-conn", tcpPacket.L4ReverseFlowHash()),
zap.String("state", fmt.Sprintf("%d", conn.GetState())),
)
}
return nil
}
// Convert Ack to FinAck for all other pus
return tcpPacket.ConvertAcktoFinAck()
}
if policy.Action.Rejected() {
return errors.New("Reject the packet")
}
if err := d.conntrack.UpdateApplicationFlowMark(
tcpPacket.SourceAddress,
tcpPacket.DestinationAddress,
tcpPacket.IPProto,
tcpPacket.SourcePort,
tcpPacket.DestinationPort,
constants.DefaultConnMark,
); err != nil {
zap.L().Error("Failed to update conntrack entry for flow at Ack packet",
zap.String("context", string(conn.Auth.LocalContext)),
zap.String("app-conn", tcpPacket.L4ReverseFlowHash()),
zap.String("state", fmt.Sprintf("%d", conn.GetState())),
)
}
return nil
}
// Here we capture the first data packet after an ACK packet by modyfing the
// state. We will not release the caches though to deal with re-transmissions.
// We will let the caches expire.
if conn.GetState() == connection.TCPAckSend {
conn.SetState(connection.TCPData)
return nil
}
return fmt.Errorf("received application ack packet in the wrong state: %d", conn.GetState())
}
// processNetworkTCPPacket processes a network TCP packet and dispatches it to different methods based on the flags
func (d *Datapath) processNetworkTCPPacket(tcpPacket *packet.Packet, context *pucontext.PUContext, conn *connection.TCPConnection) (action interface{}, claims *tokens.ConnectionClaims, err error) {
if conn == nil {
return nil, nil, nil
}
// Update connection state in the internal state machine tracker
switch tcpPacket.TCPFlags & packet.TCPSynAckMask {
case packet.TCPSynMask:
return d.processNetworkSynPacket(context, conn, tcpPacket)
case packet.TCPAckMask:
return d.processNetworkAckPacket(context, conn, tcpPacket)
case packet.TCPSynAckMask:
return d.processNetworkSynAckPacket(context, conn, tcpPacket)
default: // Ignore any other packet
return nil, nil, nil
}
}
// processNetworkSynPacket processes a syn packet arriving from the network
func (d *Datapath) processNetworkSynPacket(context *pucontext.PUContext, conn *connection.TCPConnection, tcpPacket *packet.Packet) (action interface{}, claims *tokens.ConnectionClaims, err error) {
// Incoming packets that don't have our options are candidates to be processed
// as external services.
if err = tcpPacket.CheckTCPAuthenticationOption(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
// If there is no auth option, attempt the ACLs
report, pkt, perr := context.NetworkACLPolicy(tcpPacket)
d.reportExternalServiceFlow(context, report, pkt, false, tcpPacket)
if perr != nil || pkt.Action.Rejected() {
return nil, nil, fmt.Errorf("no auth or acls: outgoing connection dropped: %s", perr)
}
conn.SetState(connection.TCPData)
d.netOrigConnectionTracker.AddOrUpdate(tcpPacket.L4FlowHash(), conn)
d.appReplyConnectionTracker.AddOrUpdate(tcpPacket.L4ReverseFlowHash(), conn)
return pkt, nil, nil
}
// 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, tcpPacket.ReadTCPData())
// If the token signature is not valid, we must drop the connection and we drop the Syn packet.
// The source will retry but we have no state to maintain here.
if err != nil {
d.reportRejectedFlow(tcpPacket, conn, collector.DefaultEndPoint, context.ManagementID(), context, tokens.CodeFromErr(err), nil, nil, false)
return nil, nil, fmt.Errorf("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.reportRejectedFlow(tcpPacket, conn, collector.DefaultEndPoint, context.ManagementID(), context, collector.InvalidToken, nil, nil, false)
return nil, nil, errors.New("Syn packet dropped because of no claims")
}
txLabel, ok := claims.T.Get(enforcerconstants.TransmitterLabel)
if err := tcpPacket.CheckTCPAuthenticationOption(enforcerconstants.TCPAuthenticationOptionBaseLen); !ok || err != nil {
d.reportRejectedFlow(tcpPacket, conn, txLabel, context.ManagementID(), context, collector.InvalidFormat, nil, nil, false)
return nil, nil, fmt.Errorf("TCP authentication option not found: %s", err)
}
// Remove any of our data from the packet. No matter what we don't need the
// metadata any more.
if err := tcpPacket.TCPDataDetach(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
d.reportRejectedFlow(tcpPacket, conn, txLabel, context.ManagementID(), context, collector.InvalidHeader, nil, nil, false)
return nil, nil, fmt.Errorf("Syn packet dropped because of invalid format: %s", err)
}
tcpPacket.DropDetachedBytes()
// 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
tags := claims.T.Copy()
tags.AppendKeyValue(enforcerconstants.PortNumberLabelString, strconv.Itoa(int(tcpPacket.DestinationPort)))
report, pkt := context.SearchRcvRules(tags)
if pkt.Action.Rejected() && (txLabel != context.ManagementID()) {
d.reportRejectedFlow(tcpPacket, conn, txLabel, context.ManagementID(), context, collector.PolicyDrop, report, pkt, false)
return nil, nil, fmt.Errorf("connection rejected because of policy: %s", tags.String())
}
hash := tcpPacket.L4FlowHash()
// Update the connection state and store the Nonse send to us by the host.
// We use the nonse in the subsequent packets to achieve randomization.
conn.SetState(connection.TCPSynReceived)
// conntrack
d.netOrigConnectionTracker.AddOrUpdate(hash, conn)
d.appReplyConnectionTracker.AddOrUpdate(tcpPacket.L4ReverseFlowHash(), conn)
// Cache the action
conn.ReportFlowPolicy = report
conn.PacketFlowPolicy = pkt
if txLabel == context.ManagementID() {
zap.L().Debug("Traffic to the same pu", zap.String("flow", tcpPacket.L4FlowHash()))
conn.SetLoopbackConnection(true)
}
// Accept the connection
return pkt, claims, nil
}
// policyPair stores both reporting and actual action taken on packet.
type policyPair struct {
report *policy.FlowPolicy
packet *policy.FlowPolicy
}
// processNetworkSynAckPacket processes a SynAck packet arriving from the network
func (d *Datapath) processNetworkSynAckPacket(context *pucontext.PUContext, conn *connection.TCPConnection, tcpPacket *packet.Packet) (action interface{}, claims *tokens.ConnectionClaims, err error) {
// Packets with no authorization are processed as external services based on the ACLS
if err = tcpPacket.CheckTCPAuthenticationOption(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
if _, err := d.puFromContextID.Get(conn.Context.ID()); err != nil {
// PU has been deleted. Ignore these packets
return nil, nil, fmt.Errorf("PU is already dead - drop SynAck packet")
}
flowHash := tcpPacket.SourceAddress.String() + ":" + strconv.Itoa(int(tcpPacket.SourcePort))
if plci, plerr := context.RetrieveCachedExternalFlowPolicy(flowHash); plerr == nil {
plc := plci.(*policyPair)
d.releaseFlow(context, plc.report, plc.packet, tcpPacket)
return plc.packet, nil, nil
}
// Never seen this IP before, let's parse them.
report, pkt, perr := context.ApplicationACLPolicyFromAddr(tcpPacket.SourceAddress.To4(), tcpPacket.SourcePort)
if perr != nil || pkt.Action.Rejected() {
d.reportReverseExternalServiceFlow(context, report, pkt, true, tcpPacket)
return nil, nil, fmt.Errorf("no auth or acls: drop synack packet and connection: %s: action=%d", perr, pkt.Action)
}
// Added to the cache if we can accept it
context.CacheExternalFlowPolicy(
tcpPacket,
&policyPair{
report: report,
packet: pkt,
},
)
// Set the state to Data so the other state machines ignore subsequent packets
conn.SetState(connection.TCPData)
d.releaseFlow(context, report, pkt, tcpPacket)
return pkt, nil, nil
}
// This is a corner condition. We are receiving a SynAck packet and we are in
// a state that indicates that we have already processed one. This means that
// our ack packet was lost. We need to revert conntrack in this case and get
// back into the picture.
if conn.GetState() != connection.TCPSynSend {
// Revert the connmarks - dealing with retransmissions
if cerr := d.conntrack.UpdateNetworkFlowMark(
tcpPacket.SourceAddress,
tcpPacket.DestinationAddress,
tcpPacket.IPProto,
tcpPacket.SourcePort,
tcpPacket.DestinationPort,
0,
); cerr != nil {
zap.L().Error("Failed to update conntrack table for flow after synack packet",
zap.String("context", string(conn.Auth.LocalContext)),
zap.String("app-conn", tcpPacket.L4ReverseFlowHash()),
zap.String("state", fmt.Sprintf("%d", conn.GetState())),
)
}
}
// Now we can process the SynAck packet with its options
tcpData := tcpPacket.ReadTCPData()
if len(tcpData) == 0 {
d.reportRejectedFlow(tcpPacket, nil, context.ManagementID(), collector.DefaultEndPoint, context, collector.MissingToken, nil, nil, true)
return nil, nil, errors.New("SynAck packet dropped because of missing token")
}
claims, err = d.tokenAccessor.ParsePacketToken(&conn.Auth, tcpPacket.ReadTCPData())
if err != nil {
d.reportRejectedFlow(tcpPacket, nil, context.ManagementID(), collector.DefaultEndPoint, context, collector.MissingToken, nil, nil, true)
return nil, nil, fmt.Errorf("SynAck packet dropped because of bad claims: %s", err)
}
if claims == nil {
d.reportRejectedFlow(tcpPacket, nil, context.ManagementID(), collector.DefaultEndPoint, context, collector.MissingToken, nil, nil, true)
return nil, nil, errors.New("SynAck packet dropped because of no claims")
}
tcpPacket.ConnectionMetadata = &conn.Auth
if err := tcpPacket.CheckTCPAuthenticationOption(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
d.reportRejectedFlow(tcpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, collector.InvalidHeader, nil, nil, true)
return nil, nil, errors.New("TCP authentication option not found")
}
// Remove any of our data
if err := tcpPacket.TCPDataDetach(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
d.reportRejectedFlow(tcpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, collector.InvalidPayload, nil, nil, true)
return nil, nil, fmt.Errorf("SynAck packet dropped because of invalid format: %s", err)
}
tcpPacket.DropDetachedBytes()
if !d.mutualAuthorization {
// If we dont do mutual authorization, dont lookup txt rules.
conn.SetState(connection.TCPSynAckReceived)
// conntrack
d.netReplyConnectionTracker.AddOrUpdate(tcpPacket.L4FlowHash(), conn)
return nil, claims, nil
}
report, pkt := context.SearchTxtRules(claims.T, !d.mutualAuthorization)
// Report and release traffic belonging to the same pu
if conn.Auth.RemoteContextID == context.ManagementID() {
conn.SetState(connection.TCPData)
conn.SetLoopbackConnection(true)
d.reportAcceptedFlow(tcpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, nil, nil, true)
d.releaseUnmonitoredFlow(tcpPacket)
return nil, nil, nil
}
// NOTE: For backward compatibility, remove this check later
if claims.H != nil {
if claims.H.ToClaimsHeader().Encrypt() != pkt.Action.Encrypted() {
d.reportRejectedFlow(tcpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, collector.EncryptionMismatch, nil, nil, true)
return nil, nil, fmt.Errorf("syn/ack packet dropped because of encryption mismatch")
}
}
if pkt.Action.Rejected() {
d.reportRejectedFlow(tcpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, collector.PolicyDrop, report, pkt, true)
return nil, nil, fmt.Errorf("dropping because of reject rule on transmitter: %s", claims.T.String())
}
conn.SetState(connection.TCPSynAckReceived)
// conntrack
d.netReplyConnectionTracker.AddOrUpdate(tcpPacket.L4FlowHash(), conn)
return pkt, claims, nil
}
// processNetworkAckPacket processes an Ack packet arriving from the network
func (d *Datapath) processNetworkAckPacket(context *pucontext.PUContext, conn *connection.TCPConnection, tcpPacket *packet.Packet) (action interface{}, claims *tokens.ConnectionClaims, err error) {
if conn.GetState() == connection.TCPData || conn.GetState() == connection.TCPAckSend {
return nil, nil, nil
}
if conn.IsLoopbackConnection() {
conn.SetState(connection.TCPData)
d.releaseUnmonitoredFlow(tcpPacket)
return nil, nil, nil
}
if conn.GetState() == connection.UnknownState {
// Check if the destination is in the external servicess approved cache
// and if yes, allow the packet to go and release the flow.
_, plcy, perr := context.NetworkACLPolicy(tcpPacket)
// Ignore FIN packets. Let them go through.
if tcpPacket.TCPFlags&packet.TCPFinMask != 0 {
return nil, nil, nil
}
if perr != nil {
err := tcpPacket.ConvertAcktoFinAck()
return nil, nil, err
}
if plcy.Action.Rejected() {
return nil, nil, errors.New("Reject the packet")
}
if err := d.conntrack.UpdateNetworkFlowMark(
tcpPacket.SourceAddress,
tcpPacket.DestinationAddress,
tcpPacket.IPProto,
tcpPacket.SourcePort,
tcpPacket.DestinationPort,
constants.DefaultConnMark,
); err != nil && !netlink.IsNotExist(errors.Cause(err)) {
zap.L().Error("Failed to update conntrack entry for flow at network Ack packet",
zap.String("context", string(conn.Auth.LocalContext)),
zap.String("app-conn", tcpPacket.L4ReverseFlowHash()),
zap.String("state", fmt.Sprintf("%d", conn.GetState())),
zap.Error(err),
)
}
return nil, nil, nil
}
hash := tcpPacket.L4FlowHash()
// Validate that the source/destination nonse matches. The signature has validated both directions
if conn.GetState() == connection.TCPSynAckSend || conn.GetState() == connection.TCPSynReceived {
if err := tcpPacket.CheckTCPAuthenticationOption(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
// TODO: this needs to be converted to a rejected packet messages. It doesn't mean rejected flow. Disabling.
// d.reportRejectedFlow(tcpPacket, conn, collector.DefaultEndPoint, context.ManagementID(), context, collector.InvalidHeader, nil, nil)
return nil, nil, fmt.Errorf("TCP authentication option not found: %s", err)
}
if _, err := d.tokenAccessor.ParseAckToken(&conn.Auth, tcpPacket.ReadTCPData()); err != nil {
d.reportRejectedFlow(tcpPacket, conn, collector.DefaultEndPoint, context.ManagementID(), context, collector.InvalidToken, nil, nil, false)
return nil, nil, fmt.Errorf("Ack packet dropped because signature validation failed: %s", err)
}
// Remove any of our data - adjust the sequence numbers
if err := tcpPacket.TCPDataDetach(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
d.reportRejectedFlow(tcpPacket, conn, collector.DefaultEndPoint, context.ManagementID(), context, collector.InvalidPayload, nil, nil, false)
return nil, nil, fmt.Errorf("Ack packet dropped because of invalid format: %s", err)
}
tcpPacket.DropDetachedBytes()
if conn.PacketFlowPolicy != nil && conn.PacketFlowPolicy.Action.Rejected() {
if !conn.PacketFlowPolicy.ObserveAction.Observed() {
zap.L().Error("Flow rejected but not observed", zap.String("conn", context.ManagementID()))
}
// Flow has been allowed because we are observing a deny rule's impact on the system. Packets are forwarded, reported as dropped + observed.
d.reportRejectedFlow(tcpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, collector.PolicyDrop, conn.ReportFlowPolicy, conn.PacketFlowPolicy, false)
} else {
// We accept the packet as a new flow
d.reportAcceptedFlow(tcpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, conn.ReportFlowPolicy, conn.PacketFlowPolicy, false)
}
conn.SetState(connection.TCPData)
if !conn.ServiceConnection {
if err := d.conntrack.UpdateNetworkFlowMark(
tcpPacket.SourceAddress,
tcpPacket.DestinationAddress,
tcpPacket.IPProto,
tcpPacket.SourcePort,
tcpPacket.DestinationPort,
constants.DefaultConnMark,
); err != nil {
zap.L().Error("Failed to update conntrack table after ack packet",
zap.String("app-conn", tcpPacket.L4ReverseFlowHash()))
}
}
// Accept the packet
return nil, nil, nil
}
if conn.ServiceConnection {
return nil, nil, nil
}
// Everything else is dropped - ACK received in the Syn state without a SynAck
d.reportRejectedFlow(tcpPacket, conn, conn.Auth.RemoteContextID, context.ManagementID(), context, collector.InvalidState, nil, nil, false)
zap.L().Error("Invalid state reached",
zap.String("state", fmt.Sprintf("%d", conn.GetState())),
zap.String("context", context.ManagementID()),
zap.String("net-conn", hash),
)
return nil, nil, fmt.Errorf("Ack packet dropped, invalid duplicate state: %d", conn.GetState())
}
// createTCPAuthenticationOption creates the TCP authentication option -
func (d *Datapath) createTCPAuthenticationOption(token []byte) []byte {
tokenLen := uint8(len(token))
options := []byte{packet.TCPAuthenticationOption, enforcerconstants.TCPAuthenticationOptionBaseLen + tokenLen, 0, 0}
if tokenLen != 0 {
options = append(options, token...)
}
return options
}
// appSynRetrieveState retrieves state for the the application Syn packet.
// It creates a new connection by default
func (d *Datapath) appSynRetrieveState(p *packet.Packet) (*connection.TCPConnection, error) {
context, err := d.contextFromIP(true, p.Mark, p.SourcePort, packet.IPProtocolTCP)
if err != nil {
return nil, errors.New("No context in app processing")
}
if conn, err := d.appOrigConnectionTracker.GetReset(p.L4FlowHash(), 0); err == nil {
return conn.(*connection.TCPConnection), nil
}
return connection.NewTCPConnection(context, p), nil
}
// appSynAckRetrieveState retrieves the state for application syn/ack packet.
func (d *Datapath) appSynAckRetrieveState(p *packet.Packet) (*connection.TCPConnection, error) {
hash := p.L4FlowHash()
// Did we see a network syn for this server PU?
conn, err := d.appReplyConnectionTracker.GetReset(hash, 0)
if err != nil {
return nil, errNetSynNotSeen
}
if uerr := updateTimer(d.appReplyConnectionTracker, hash, conn.(*connection.TCPConnection)); uerr != nil {
zap.L().Error("entry expired just before updating the timer", zap.String("flow", hash))
return nil, uerr
}
return conn.(*connection.TCPConnection), nil
}
// appRetrieveState retrieves the state for the rest of the application packets. It
// returns an error if it cannot find the state
func (d *Datapath) appRetrieveState(p *packet.Packet) (*connection.TCPConnection, error) {
hash := p.L4FlowHash()
// If this ack packet is from Server, Did we see a network Syn for this server PU?
conn, err := d.appReplyConnectionTracker.GetReset(hash, 0)
if err == nil {
if uerr := updateTimer(d.appReplyConnectionTracker, hash, conn.(*connection.TCPConnection)); uerr != nil {
zap.L().Error("entry expired just before updating the timer", zap.String("flow", hash))
return nil, uerr
}
return conn.(*connection.TCPConnection), nil
}
// If this ack packet is from client, Did we see an Application Syn packet before?
conn, err = d.appOrigConnectionTracker.GetReset(hash, 0)
if err == nil {
if uerr := updateTimer(d.appOrigConnectionTracker, hash, conn.(*connection.TCPConnection)); uerr != nil {
return nil, uerr
}
return conn.(*connection.TCPConnection), nil
}
if p.TCPFlags&packet.TCPSynAckMask == packet.TCPAckMask {
// Let's try if its an existing connection
context, err := d.contextFromIP(true, p.Mark, p.SourcePort, packet.IPProtocolTCP)
if err != nil {
return nil, errors.New("No context in app processing")
}
conn = connection.NewTCPConnection(context, p)
conn.(*connection.TCPConnection).SetState(connection.UnknownState)
return conn.(*connection.TCPConnection), nil
}
return nil, errNoConnFound
}
// netSynRetrieveState retrieves the state for the Syn packets on the network.
// Obviously if no state is found, it generates a new connection record.
func (d *Datapath) netSynRetrieveState(p *packet.Packet) (*connection.TCPConnection, error) {
context, err := d.contextFromIP(false, p.Mark, p.DestinationPort, packet.IPProtocolTCP)
if err != nil {
//This needs to hit only for local processes never for containers
//Don't return an error create a dummy context and return it so we truncate the packet before we send it up
if d.mode != constants.RemoteContainer {
//we will create the bare minimum needed to exercise our stack
//We need this syn to look similar to what we will pass on the retry
//so we setup enough for us to identify this request in the later stages
// Remove any of our data from the packet.
if err = p.CheckTCPAuthenticationOption(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
zap.L().Error("Syn received with tcp option not set", zap.Error(err))
return nil, errNonPUTraffic
}
if err = p.TCPDataDetach(enforcerconstants.TCPAuthenticationOptionBaseLen); err != nil {
zap.L().Error("Error removing TCP Data", zap.Error(err))
return nil, errNonPUTraffic
}
p.DropDetachedBytes()