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tunnelServer.go
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tunnelServer.go
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/*
* Copyright (c) 2016, Psiphon Inc.
* All rights reserved.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package server
import (
"context"
"crypto/rand"
"crypto/subtle"
"encoding/base64"
"encoding/json"
"errors"
"fmt"
"io"
"io/ioutil"
"net"
"strconv"
"sync"
"sync/atomic"
"syscall"
"time"
"github.com/Psiphon-Labs/goarista/monotime"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/accesscontrol"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/crypto/ssh"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/fragmentor"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/marionette"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/obfuscator"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/osl"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/protocol"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/quic"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/tactics"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/tapdance"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/tun"
"github.com/marusama/semaphore"
cache "github.com/patrickmn/go-cache"
)
const (
SSH_AUTH_LOG_PERIOD = 30 * time.Minute
SSH_HANDSHAKE_TIMEOUT = 30 * time.Second
SSH_BEGIN_HANDSHAKE_TIMEOUT = 1 * time.Second
SSH_CONNECTION_READ_DEADLINE = 5 * time.Minute
SSH_TCP_PORT_FORWARD_COPY_BUFFER_SIZE = 8192
SSH_TCP_PORT_FORWARD_QUEUE_SIZE = 1024
SSH_KEEP_ALIVE_PAYLOAD_MIN_BYTES = 0
SSH_KEEP_ALIVE_PAYLOAD_MAX_BYTES = 256
SSH_SEND_OSL_INITIAL_RETRY_DELAY = 30 * time.Second
SSH_SEND_OSL_RETRY_FACTOR = 2
OSL_SESSION_CACHE_TTL = 5 * time.Minute
MAX_AUTHORIZATIONS = 16
PRE_HANDSHAKE_RANDOM_STREAM_MAX_COUNT = 1
RANDOM_STREAM_MAX_BYTES = 10485760
)
// TunnelServer is the main server that accepts Psiphon client
// connections, via various obfuscation protocols, and provides
// port forwarding (TCP and UDP) services to the Psiphon client.
// At its core, TunnelServer is an SSH server. SSH is the base
// protocol that provides port forward multiplexing, and transport
// security. Layered on top of SSH, optionally, is Obfuscated SSH
// and meek protocols, which provide further circumvention
// capabilities.
type TunnelServer struct {
runWaitGroup *sync.WaitGroup
listenerError chan error
shutdownBroadcast <-chan struct{}
sshServer *sshServer
}
// NewTunnelServer initializes a new tunnel server.
func NewTunnelServer(
support *SupportServices,
shutdownBroadcast <-chan struct{}) (*TunnelServer, error) {
sshServer, err := newSSHServer(support, shutdownBroadcast)
if err != nil {
return nil, common.ContextError(err)
}
return &TunnelServer{
runWaitGroup: new(sync.WaitGroup),
listenerError: make(chan error),
shutdownBroadcast: shutdownBroadcast,
sshServer: sshServer,
}, nil
}
// Run runs the tunnel server; this function blocks while running a selection of
// listeners that handle connection using various obfuscation protocols.
//
// Run listens on each designated tunnel port and spawns new goroutines to handle
// each client connection. It halts when shutdownBroadcast is signaled. A list of active
// clients is maintained, and when halting all clients are cleanly shutdown.
//
// Each client goroutine handles its own obfuscation (optional), SSH handshake, SSH
// authentication, and then looping on client new channel requests. "direct-tcpip"
// channels, dynamic port fowards, are supported. When the UDPInterceptUdpgwServerAddress
// config parameter is configured, UDP port forwards over a TCP stream, following
// the udpgw protocol, are handled.
//
// A new goroutine is spawned to handle each port forward for each client. Each port
// forward tracks its bytes transferred. Overall per-client stats for connection duration,
// GeoIP, number of port forwards, and bytes transferred are tracked and logged when the
// client shuts down.
//
// Note: client handler goroutines may still be shutting down after Run() returns. See
// comment in sshClient.stop(). TODO: fully synchronized shutdown.
func (server *TunnelServer) Run() error {
type sshListener struct {
net.Listener
localAddress string
tunnelProtocol string
}
// TODO: should TunnelServer hold its own support pointer?
support := server.sshServer.support
// First bind all listeners; once all are successful,
// start accepting connections on each.
var listeners []*sshListener
for tunnelProtocol, listenPort := range support.Config.TunnelProtocolPorts {
localAddress := fmt.Sprintf(
"%s:%d", support.Config.ServerIPAddress, listenPort)
var listener net.Listener
var err error
if protocol.TunnelProtocolUsesFrontedMeekQUIC(tunnelProtocol) {
// For FRONTED-MEEK-QUIC-OSSH, no listener implemented. The edge-to-server
// hop uses HTTPS and the client tunnel protocol is distinguished using
// protocol.MeekCookieData.ClientTunnelProtocol.
continue
} else if protocol.TunnelProtocolUsesQUIC(tunnelProtocol) {
listener, err = quic.Listen(
CommonLogger(log),
localAddress,
support.Config.ObfuscatedSSHKey)
} else if protocol.TunnelProtocolUsesMarionette(tunnelProtocol) {
listener, err = marionette.Listen(
support.Config.ServerIPAddress,
support.Config.MarionetteFormat)
} else if protocol.TunnelProtocolUsesTapdance(tunnelProtocol) {
listener, err = tapdance.Listen(localAddress)
} else {
listener, err = net.Listen("tcp", localAddress)
}
if err != nil {
for _, existingListener := range listeners {
existingListener.Listener.Close()
}
return common.ContextError(err)
}
tacticsListener := tactics.NewListener(
listener,
support.TacticsServer,
tunnelProtocol,
func(IPAddress string) common.GeoIPData {
return common.GeoIPData(support.GeoIPService.Lookup(IPAddress))
})
log.WithContextFields(
LogFields{
"localAddress": localAddress,
"tunnelProtocol": tunnelProtocol,
}).Info("listening")
listeners = append(
listeners,
&sshListener{
Listener: tacticsListener,
localAddress: localAddress,
tunnelProtocol: tunnelProtocol,
})
}
for _, listener := range listeners {
server.runWaitGroup.Add(1)
go func(listener *sshListener) {
defer server.runWaitGroup.Done()
log.WithContextFields(
LogFields{
"localAddress": listener.localAddress,
"tunnelProtocol": listener.tunnelProtocol,
}).Info("running")
server.sshServer.runListener(
listener.Listener,
server.listenerError,
listener.tunnelProtocol)
log.WithContextFields(
LogFields{
"localAddress": listener.localAddress,
"tunnelProtocol": listener.tunnelProtocol,
}).Info("stopped")
}(listener)
}
var err error
select {
case <-server.shutdownBroadcast:
case err = <-server.listenerError:
}
for _, listener := range listeners {
listener.Close()
}
server.sshServer.stopClients()
server.runWaitGroup.Wait()
log.WithContext().Info("stopped")
return err
}
// GetLoadStats returns load stats for the tunnel server. The stats are
// broken down by protocol ("SSH", "OSSH", etc.) and type. Types of stats
// include current connected client count, total number of current port
// forwards.
func (server *TunnelServer) GetLoadStats() (ProtocolStats, RegionStats) {
return server.sshServer.getLoadStats()
}
// ResetAllClientTrafficRules resets all established client traffic rules
// to use the latest config and client properties. Any existing traffic
// rule state is lost, including throttling state.
func (server *TunnelServer) ResetAllClientTrafficRules() {
server.sshServer.resetAllClientTrafficRules()
}
// ResetAllClientOSLConfigs resets all established client OSL state to use
// the latest OSL config. Any existing OSL state is lost, including partial
// progress towards SLOKs.
func (server *TunnelServer) ResetAllClientOSLConfigs() {
server.sshServer.resetAllClientOSLConfigs()
}
// SetClientHandshakeState sets the handshake state -- that it completed and
// what parameters were passed -- in sshClient. This state is used for allowing
// port forwards and for future traffic rule selection. SetClientHandshakeState
// also triggers an immediate traffic rule re-selection, as the rules selected
// upon tunnel establishment may no longer apply now that handshake values are
// set.
//
// The authorizations received from the client handshake are verified and the
// resulting list of authorized access types are applied to the client's tunnel
// and traffic rules. A list of active authorization IDs and authorized access
// types is returned for responding to the client and logging.
func (server *TunnelServer) SetClientHandshakeState(
sessionID string,
state handshakeState,
authorizations []string) ([]string, []string, error) {
return server.sshServer.setClientHandshakeState(sessionID, state, authorizations)
}
// GetClientHandshaked indicates whether the client has completed a handshake
// and whether its traffic rules are immediately exhausted.
func (server *TunnelServer) GetClientHandshaked(
sessionID string) (bool, bool, error) {
return server.sshServer.getClientHandshaked(sessionID)
}
// UpdateClientAPIParameters updates the recorded handshake API parameters for
// the client corresponding to sessionID.
func (server *TunnelServer) UpdateClientAPIParameters(
sessionID string,
apiParams common.APIParameters) error {
return server.sshServer.updateClientAPIParameters(sessionID, apiParams)
}
// ExpectClientDomainBytes indicates whether the client was configured to report
// domain bytes in its handshake response.
func (server *TunnelServer) ExpectClientDomainBytes(
sessionID string) (bool, error) {
return server.sshServer.expectClientDomainBytes(sessionID)
}
// SetEstablishTunnels sets whether new tunnels may be established or not.
// When not establishing, incoming connections are immediately closed.
func (server *TunnelServer) SetEstablishTunnels(establish bool) {
server.sshServer.setEstablishTunnels(establish)
}
// GetEstablishTunnels returns whether new tunnels may be established or not.
func (server *TunnelServer) GetEstablishTunnels() bool {
return server.sshServer.getEstablishTunnels()
}
type sshServer struct {
// Note: 64-bit ints used with atomic operations are placed
// at the start of struct to ensure 64-bit alignment.
// (https://golang.org/pkg/sync/atomic/#pkg-note-BUG)
lastAuthLog int64
authFailedCount int64
support *SupportServices
establishTunnels int32
concurrentSSHHandshakes semaphore.Semaphore
shutdownBroadcast <-chan struct{}
sshHostKey ssh.Signer
clientsMutex sync.Mutex
stoppingClients bool
acceptedClientCounts map[string]map[string]int64
clients map[string]*sshClient
oslSessionCacheMutex sync.Mutex
oslSessionCache *cache.Cache
authorizationSessionIDsMutex sync.Mutex
authorizationSessionIDs map[string]string
}
func newSSHServer(
support *SupportServices,
shutdownBroadcast <-chan struct{}) (*sshServer, error) {
privateKey, err := ssh.ParseRawPrivateKey([]byte(support.Config.SSHPrivateKey))
if err != nil {
return nil, common.ContextError(err)
}
// TODO: use cert (ssh.NewCertSigner) for anti-fingerprint?
signer, err := ssh.NewSignerFromKey(privateKey)
if err != nil {
return nil, common.ContextError(err)
}
var concurrentSSHHandshakes semaphore.Semaphore
if support.Config.MaxConcurrentSSHHandshakes > 0 {
concurrentSSHHandshakes = semaphore.New(support.Config.MaxConcurrentSSHHandshakes)
}
// The OSL session cache temporarily retains OSL seed state
// progress for disconnected clients. This enables clients
// that disconnect and immediately reconnect to the same
// server to resume their OSL progress. Cached progress
// is referenced by session ID and is retained for
// OSL_SESSION_CACHE_TTL after disconnect.
//
// Note: session IDs are assumed to be unpredictable. If a
// rogue client could guess the session ID of another client,
// it could resume its OSL progress and, if the OSL config
// were known, infer some activity.
oslSessionCache := cache.New(OSL_SESSION_CACHE_TTL, 1*time.Minute)
return &sshServer{
support: support,
establishTunnels: 1,
concurrentSSHHandshakes: concurrentSSHHandshakes,
shutdownBroadcast: shutdownBroadcast,
sshHostKey: signer,
acceptedClientCounts: make(map[string]map[string]int64),
clients: make(map[string]*sshClient),
oslSessionCache: oslSessionCache,
authorizationSessionIDs: make(map[string]string),
}, nil
}
func (sshServer *sshServer) setEstablishTunnels(establish bool) {
// Do nothing when the setting is already correct. This avoids
// spurious log messages when setEstablishTunnels is called
// periodically with the same setting.
if establish == sshServer.getEstablishTunnels() {
return
}
establishFlag := int32(1)
if !establish {
establishFlag = 0
}
atomic.StoreInt32(&sshServer.establishTunnels, establishFlag)
log.WithContextFields(
LogFields{"establish": establish}).Info("establishing tunnels")
}
func (sshServer *sshServer) getEstablishTunnels() bool {
return atomic.LoadInt32(&sshServer.establishTunnels) == 1
}
// runListener is intended to run an a goroutine; it blocks
// running a particular listener. If an unrecoverable error
// occurs, it will send the error to the listenerError channel.
func (sshServer *sshServer) runListener(
listener net.Listener,
listenerError chan<- error,
listenerTunnelProtocol string) {
runningProtocols := make([]string, 0)
for tunnelProtocol := range sshServer.support.Config.TunnelProtocolPorts {
runningProtocols = append(runningProtocols, tunnelProtocol)
}
handleClient := func(clientTunnelProtocol string, clientConn net.Conn) {
// Note: establish tunnel limiter cannot simply stop TCP
// listeners in all cases (e.g., meek) since SSH tunnels can
// span multiple TCP connections.
if !sshServer.getEstablishTunnels() {
log.WithContext().Debug("not establishing tunnels")
clientConn.Close()
return
}
// The tunnelProtocol passed to handleClient is used for stats,
// throttling, etc. When the tunnel protocol can be determined
// unambiguously from the listening port, use that protocol and
// don't use any client-declared value. Only use the client's
// value, if present, in special cases where the listening port
// cannot distinguish the protocol.
tunnelProtocol := listenerTunnelProtocol
if clientTunnelProtocol != "" {
if !common.Contains(runningProtocols, clientTunnelProtocol) {
log.WithContextFields(
LogFields{
"clientTunnelProtocol": clientTunnelProtocol}).
Warning("invalid client tunnel protocol")
clientConn.Close()
return
}
if protocol.UseClientTunnelProtocol(
clientTunnelProtocol, runningProtocols) {
tunnelProtocol = clientTunnelProtocol
}
}
// process each client connection concurrently
go sshServer.handleClient(tunnelProtocol, clientConn)
}
// Note: when exiting due to a unrecoverable error, be sure
// to try to send the error to listenerError so that the outer
// TunnelServer.Run will properly shut down instead of remaining
// running.
if protocol.TunnelProtocolUsesMeekHTTP(listenerTunnelProtocol) ||
protocol.TunnelProtocolUsesMeekHTTPS(listenerTunnelProtocol) {
meekServer, err := NewMeekServer(
sshServer.support,
listener,
protocol.TunnelProtocolUsesMeekHTTPS(listenerTunnelProtocol),
protocol.TunnelProtocolUsesFrontedMeek(listenerTunnelProtocol),
protocol.TunnelProtocolUsesObfuscatedSessionTickets(listenerTunnelProtocol),
handleClient,
sshServer.shutdownBroadcast)
if err == nil {
err = meekServer.Run()
}
if err != nil {
select {
case listenerError <- common.ContextError(err):
default:
}
return
}
} else {
for {
conn, err := listener.Accept()
select {
case <-sshServer.shutdownBroadcast:
if err == nil {
conn.Close()
}
return
default:
}
if err != nil {
if e, ok := err.(net.Error); ok && e.Temporary() {
log.WithContextFields(LogFields{"error": err}).Error("accept failed")
// Temporary error, keep running
continue
}
select {
case listenerError <- common.ContextError(err):
default:
}
return
}
handleClient("", conn)
}
}
}
// An accepted client has completed a direct TCP or meek connection and has a net.Conn. Registration
// is for tracking the number of connections.
func (sshServer *sshServer) registerAcceptedClient(tunnelProtocol, region string) {
sshServer.clientsMutex.Lock()
defer sshServer.clientsMutex.Unlock()
if sshServer.acceptedClientCounts[tunnelProtocol] == nil {
sshServer.acceptedClientCounts[tunnelProtocol] = make(map[string]int64)
}
sshServer.acceptedClientCounts[tunnelProtocol][region] += 1
}
func (sshServer *sshServer) unregisterAcceptedClient(tunnelProtocol, region string) {
sshServer.clientsMutex.Lock()
defer sshServer.clientsMutex.Unlock()
sshServer.acceptedClientCounts[tunnelProtocol][region] -= 1
}
// An established client has completed its SSH handshake and has a ssh.Conn. Registration is
// for tracking the number of fully established clients and for maintaining a list of running
// clients (for stopping at shutdown time).
func (sshServer *sshServer) registerEstablishedClient(client *sshClient) bool {
sshServer.clientsMutex.Lock()
if sshServer.stoppingClients {
sshServer.clientsMutex.Unlock()
return false
}
// In the case of a duplicate client sessionID, the previous client is closed.
// - Well-behaved clients generate a random sessionID that should be unique (won't
// accidentally conflict) and hard to guess (can't be targeted by a malicious
// client).
// - Clients reuse the same sessionID when a tunnel is unexpectedly disconnected
// and reestablished. In this case, when the same server is selected, this logic
// will be hit; closing the old, dangling client is desirable.
// - Multi-tunnel clients should not normally use one server for multiple tunnels.
existingClient := sshServer.clients[client.sessionID]
sshServer.clientsMutex.Unlock()
if existingClient != nil {
// This case is expected to be common, and so logged at the lowest severity
// level.
log.WithContext().Debug(
"stopping existing client with duplicate session ID")
existingClient.stop()
// Block until the existingClient is fully terminated. This is necessary to
// avoid this scenario:
// - existingClient is invoking handshakeAPIRequestHandler
// - sshServer.clients[client.sessionID] is updated to point to new client
// - existingClient's handshakeAPIRequestHandler invokes
// SetClientHandshakeState but sets the handshake parameters for new
// client
// - as a result, the new client handshake will fail (only a single handshake
// is permitted) and the new client server_tunnel log will contain an
// invalid mix of existing/new client fields
//
// Once existingClient.awaitStopped returns, all existingClient port
// forwards and request handlers have terminated, so no API handler, either
// tunneled web API or SSH API, will remain and it is safe to point
// sshServer.clients[client.sessionID] to the new client.
// Limitation: this scenario remains possible with _untunneled_ web API
// requests.
//
// Blocking also ensures existingClient.releaseAuthorizations is invoked before
// the new client attempts to submit the same authorizations.
//
// Perform blocking awaitStopped operation outside the
// sshServer.clientsMutex mutex to avoid blocking all other clients for the
// duration. We still expect and require that the stop process completes
// rapidly, e.g., does not block on network I/O, allowing the new client
// connection to proceed without delay.
//
// In addition, operations triggered by stop, and which must complete before
// awaitStopped returns, will attempt to lock sshServer.clientsMutex,
// including unregisterEstablishedClient.
existingClient.awaitStopped()
}
sshServer.clientsMutex.Lock()
defer sshServer.clientsMutex.Unlock()
// existingClient's stop will have removed it from sshServer.clients via
// unregisterEstablishedClient, so sshServer.clients[client.sessionID] should
// be nil -- unless yet another client instance using the same sessionID has
// connected in the meantime while awaiting existingClient stop. In this
// case, it's not clear which is the most recent connection from the client,
// so instead of this connection terminating more peers, it aborts.
if sshServer.clients[client.sessionID] != nil {
// As this is expected to be rare case, it's logged at a higher severity
// level.
log.WithContext().Warning(
"aborting new client with duplicate session ID")
return false
}
sshServer.clients[client.sessionID] = client
return true
}
func (sshServer *sshServer) unregisterEstablishedClient(client *sshClient) {
sshServer.clientsMutex.Lock()
registeredClient := sshServer.clients[client.sessionID]
// registeredClient will differ from client when client is the existingClient
// terminated in registerEstablishedClient. In that case, registeredClient
// remains connected, and the sshServer.clients entry should be retained.
if registeredClient == client {
delete(sshServer.clients, client.sessionID)
}
sshServer.clientsMutex.Unlock()
client.stop()
}
type ProtocolStats map[string]map[string]int64
type RegionStats map[string]map[string]map[string]int64
func (sshServer *sshServer) getLoadStats() (ProtocolStats, RegionStats) {
sshServer.clientsMutex.Lock()
defer sshServer.clientsMutex.Unlock()
// Explicitly populate with zeros to ensure 0 counts in log messages
zeroStats := func() map[string]int64 {
stats := make(map[string]int64)
stats["accepted_clients"] = 0
stats["established_clients"] = 0
stats["dialing_tcp_port_forwards"] = 0
stats["tcp_port_forwards"] = 0
stats["total_tcp_port_forwards"] = 0
stats["udp_port_forwards"] = 0
stats["total_udp_port_forwards"] = 0
stats["tcp_port_forward_dialed_count"] = 0
stats["tcp_port_forward_dialed_duration"] = 0
stats["tcp_port_forward_failed_count"] = 0
stats["tcp_port_forward_failed_duration"] = 0
stats["tcp_port_forward_rejected_dialing_limit_count"] = 0
return stats
}
zeroProtocolStats := func() map[string]map[string]int64 {
stats := make(map[string]map[string]int64)
stats["ALL"] = zeroStats()
for tunnelProtocol := range sshServer.support.Config.TunnelProtocolPorts {
stats[tunnelProtocol] = zeroStats()
}
return stats
}
// [<protocol or ALL>][<stat name>] -> count
protocolStats := zeroProtocolStats()
// [<region][<protocol or ALL>][<stat name>] -> count
regionStats := make(RegionStats)
// Note: as currently tracked/counted, each established client is also an accepted client
for tunnelProtocol, regionAcceptedClientCounts := range sshServer.acceptedClientCounts {
for region, acceptedClientCount := range regionAcceptedClientCounts {
if acceptedClientCount > 0 {
if regionStats[region] == nil {
regionStats[region] = zeroProtocolStats()
}
protocolStats["ALL"]["accepted_clients"] += acceptedClientCount
protocolStats[tunnelProtocol]["accepted_clients"] += acceptedClientCount
regionStats[region]["ALL"]["accepted_clients"] += acceptedClientCount
regionStats[region][tunnelProtocol]["accepted_clients"] += acceptedClientCount
}
}
}
for _, client := range sshServer.clients {
client.Lock()
tunnelProtocol := client.tunnelProtocol
region := client.geoIPData.Country
if regionStats[region] == nil {
regionStats[region] = zeroProtocolStats()
}
stats := []map[string]int64{
protocolStats["ALL"],
protocolStats[tunnelProtocol],
regionStats[region]["ALL"],
regionStats[region][tunnelProtocol]}
for _, stat := range stats {
stat["established_clients"] += 1
// Note: can't sum trafficState.peakConcurrentPortForwardCount to get a global peak
stat["dialing_tcp_port_forwards"] += client.tcpTrafficState.concurrentDialingPortForwardCount
stat["tcp_port_forwards"] += client.tcpTrafficState.concurrentPortForwardCount
stat["total_tcp_port_forwards"] += client.tcpTrafficState.totalPortForwardCount
// client.udpTrafficState.concurrentDialingPortForwardCount isn't meaningful
stat["udp_port_forwards"] += client.udpTrafficState.concurrentPortForwardCount
stat["total_udp_port_forwards"] += client.udpTrafficState.totalPortForwardCount
stat["tcp_port_forward_dialed_count"] += client.qualityMetrics.tcpPortForwardDialedCount
stat["tcp_port_forward_dialed_duration"] +=
int64(client.qualityMetrics.tcpPortForwardDialedDuration / time.Millisecond)
stat["tcp_port_forward_failed_count"] += client.qualityMetrics.tcpPortForwardFailedCount
stat["tcp_port_forward_failed_duration"] +=
int64(client.qualityMetrics.tcpPortForwardFailedDuration / time.Millisecond)
stat["tcp_port_forward_rejected_dialing_limit_count"] +=
client.qualityMetrics.tcpPortForwardRejectedDialingLimitCount
}
client.qualityMetrics.tcpPortForwardDialedCount = 0
client.qualityMetrics.tcpPortForwardDialedDuration = 0
client.qualityMetrics.tcpPortForwardFailedCount = 0
client.qualityMetrics.tcpPortForwardFailedDuration = 0
client.qualityMetrics.tcpPortForwardRejectedDialingLimitCount = 0
client.Unlock()
}
return protocolStats, regionStats
}
func (sshServer *sshServer) resetAllClientTrafficRules() {
sshServer.clientsMutex.Lock()
clients := make(map[string]*sshClient)
for sessionID, client := range sshServer.clients {
clients[sessionID] = client
}
sshServer.clientsMutex.Unlock()
for _, client := range clients {
client.setTrafficRules()
}
}
func (sshServer *sshServer) resetAllClientOSLConfigs() {
// Flush cached seed state. This has the same effect
// and same limitations as calling setOSLConfig for
// currently connected clients -- all progress is lost.
sshServer.oslSessionCacheMutex.Lock()
sshServer.oslSessionCache.Flush()
sshServer.oslSessionCacheMutex.Unlock()
sshServer.clientsMutex.Lock()
clients := make(map[string]*sshClient)
for sessionID, client := range sshServer.clients {
clients[sessionID] = client
}
sshServer.clientsMutex.Unlock()
for _, client := range clients {
client.setOSLConfig()
}
}
func (sshServer *sshServer) setClientHandshakeState(
sessionID string,
state handshakeState,
authorizations []string) ([]string, []string, error) {
sshServer.clientsMutex.Lock()
client := sshServer.clients[sessionID]
sshServer.clientsMutex.Unlock()
if client == nil {
return nil, nil, common.ContextError(errors.New("unknown session ID"))
}
activeAuthorizationIDs, authorizedAccessTypes, err := client.setHandshakeState(
state, authorizations)
if err != nil {
return nil, nil, common.ContextError(err)
}
return activeAuthorizationIDs, authorizedAccessTypes, nil
}
func (sshServer *sshServer) getClientHandshaked(
sessionID string) (bool, bool, error) {
sshServer.clientsMutex.Lock()
client := sshServer.clients[sessionID]
sshServer.clientsMutex.Unlock()
if client == nil {
return false, false, common.ContextError(errors.New("unknown session ID"))
}
completed, exhausted := client.getHandshaked()
return completed, exhausted, nil
}
func (sshServer *sshServer) updateClientAPIParameters(
sessionID string,
apiParams common.APIParameters) error {
sshServer.clientsMutex.Lock()
client := sshServer.clients[sessionID]
sshServer.clientsMutex.Unlock()
if client == nil {
return common.ContextError(errors.New("unknown session ID"))
}
client.updateAPIParameters(apiParams)
return nil
}
func (sshServer *sshServer) revokeClientAuthorizations(sessionID string) {
sshServer.clientsMutex.Lock()
client := sshServer.clients[sessionID]
sshServer.clientsMutex.Unlock()
if client == nil {
return
}
// sshClient.handshakeState.authorizedAccessTypes is not cleared. Clearing
// authorizedAccessTypes may cause sshClient.logTunnel to fail to log
// access types. As the revocation may be due to legitimate use of an
// authorization in multiple sessions by a single client, useful metrics
// would be lost.
client.Lock()
client.handshakeState.authorizationsRevoked = true
client.Unlock()
// Select and apply new traffic rules, as filtered by the client's new
// authorization state.
client.setTrafficRules()
}
func (sshServer *sshServer) expectClientDomainBytes(
sessionID string) (bool, error) {
sshServer.clientsMutex.Lock()
client := sshServer.clients[sessionID]
sshServer.clientsMutex.Unlock()
if client == nil {
return false, common.ContextError(errors.New("unknown session ID"))
}
return client.expectDomainBytes(), nil
}
func (sshServer *sshServer) stopClients() {
sshServer.clientsMutex.Lock()
sshServer.stoppingClients = true
clients := sshServer.clients
sshServer.clients = make(map[string]*sshClient)
sshServer.clientsMutex.Unlock()
for _, client := range clients {
client.stop()
}
}
func (sshServer *sshServer) handleClient(tunnelProtocol string, clientConn net.Conn) {
// Calling clientConn.RemoteAddr at this point, before any Read calls,
// satisfies the constraint documented in tapdance.Listen.
geoIPData := sshServer.support.GeoIPService.Lookup(
common.IPAddressFromAddr(clientConn.RemoteAddr()))
sshServer.registerAcceptedClient(tunnelProtocol, geoIPData.Country)
defer sshServer.unregisterAcceptedClient(tunnelProtocol, geoIPData.Country)
// When configured, enforce a cap on the number of concurrent SSH
// handshakes. This limits load spikes on busy servers when many clients
// attempt to connect at once. Wait a short time, SSH_BEGIN_HANDSHAKE_TIMEOUT,
// to acquire; waiting will avoid immediately creating more load on another
// server in the network when the client tries a new candidate. Disconnect the
// client when that wait time is exceeded.
//
// This mechanism limits memory allocations and CPU usage associated with the
// SSH handshake. At this point, new direct TCP connections or new meek
// connections, with associated resource usage, are already established. Those
// connections are expected to be rate or load limited using other mechanisms.
//
// TODO:
//
// - deduct time spent acquiring the semaphore from SSH_HANDSHAKE_TIMEOUT in
// sshClient.run, since the client is also applying an SSH handshake timeout
// and won't exclude time spent waiting.
// - each call to sshServer.handleClient (in sshServer.runListener) is invoked
// in its own goroutine, but shutdown doesn't synchronously await these
// goroutnes. Once this is synchronizes, the following context.WithTimeout
// should use an sshServer parent context to ensure blocking acquires
// interrupt immediately upon shutdown.
var onSSHHandshakeFinished func()
if sshServer.support.Config.MaxConcurrentSSHHandshakes > 0 {
ctx, cancelFunc := context.WithTimeout(
context.Background(),
sshServer.support.Config.sshBeginHandshakeTimeout)
defer cancelFunc()
err := sshServer.concurrentSSHHandshakes.Acquire(ctx, 1)
if err != nil {
clientConn.Close()
// This is a debug log as the only possible error is context timeout.
log.WithContextFields(LogFields{"error": err}).Debug(
"acquire SSH handshake semaphore failed")
return
}
onSSHHandshakeFinished = func() {
sshServer.concurrentSSHHandshakes.Release(1)
}
}
sshClient := newSshClient(sshServer, tunnelProtocol, geoIPData)
// sshClient.run _must_ call onSSHHandshakeFinished to release the semaphore:
// in any error case; or, as soon as the SSH handshake phase has successfully
// completed.
sshClient.run(clientConn, onSSHHandshakeFinished)
}
func (sshServer *sshServer) monitorPortForwardDialError(err error) {
// "err" is the error returned from a failed TCP or UDP port
// forward dial. Certain system error codes indicate low resource
// conditions: insufficient file descriptors, ephemeral ports, or
// memory. For these cases, log an alert.
// TODO: also temporarily suspend new clients
// Note: don't log net.OpError.Error() as the full error string
// may contain client destination addresses.
opErr, ok := err.(*net.OpError)
if ok {
if opErr.Err == syscall.EADDRNOTAVAIL ||
opErr.Err == syscall.EAGAIN ||
opErr.Err == syscall.ENOMEM ||
opErr.Err == syscall.EMFILE ||