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dialParameters.go
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dialParameters.go
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/*
* Copyright (c) 2018, 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 psiphon
import (
"bytes"
"crypto/md5"
"encoding/binary"
"errors"
"fmt"
"net"
"net/http"
"net/url"
"sync/atomic"
"time"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/fragmentor"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/parameters"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/prng"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/protocol"
regen "github.com/zach-klippenstein/goregen"
)
// DialParameters represents a selected protocol and all the related selected
// protocol attributes, many chosen at random, for a tunnel dial attempt.
//
// DialParameters is used:
// - to configure dialers
// - as a persistent record to store successful dial parameters for replay
// - to report dial stats in notices and Psiphon API calls.
//
// MeekResolvedIPAddress is set asynchronously, as it is not known until the
// dial process has begun. The atomic.Value will contain a string, initialized
// to "", and set to the resolved IP address once that part of the dial
// process has completed.
//
// DialParameters is not safe for concurrent use.
type DialParameters struct {
ServerEntry *protocol.ServerEntry `json:"-"`
NetworkID string `json:"-"`
IsReplay bool `json:"-"`
LastUsedTimestamp time.Time
LastUsedConfigStateHash []byte
TunnelProtocol string
DirectDialAddress string
DialPortNumber string
UpstreamProxyType string `json:"-"`
UpstreamProxyCustomHeaderNames []string `json:"-"`
SelectedSSHClientVersion bool
SSHClientVersion string
SSHKEXSeed *prng.Seed
ObfuscatorPaddingSeed *prng.Seed
FragmentorSeed *prng.Seed
MeekFrontingDialAddress string
MeekFrontingHost string
MeekDialAddress string
MeekTransformedHostName bool
MeekSNIServerName string
MeekHostHeader string
MeekObfuscatorPaddingSeed *prng.Seed
MeekResolvedIPAddress atomic.Value `json:"-"`
SelectedUserAgent bool
UserAgent string
SelectedTLSProfile bool
TLSProfile string
RandomizedTLSProfileSeed *prng.Seed
QUICVersion string
QUICDialSNIAddress string
ObfuscatedQUICPaddingSeed *prng.Seed
LivenessTestSeed *prng.Seed
APIRequestPaddingSeed *prng.Seed
DialConnMetrics common.MetricsSource `json:"-"`
ObfuscatedSSHConnMetrics common.MetricsSource `json:"-"`
dialConfig *DialConfig `json:"-"`
meekConfig *MeekConfig `json:"-"`
}
// MakeDialParameters creates a new DialParameters for the candidate server
// entry, including selecting a protocol and all the various protocol
// attributes. The input selectProtocol is used to comply with any active
// protocol selection constraints.
//
// When stored dial parameters are available and may be used,
// MakeDialParameters may replay previous dial parameters in an effort to
// leverage "known working" values instead of always chosing at random from a
// large space.
//
// MakeDialParameters will return nil/nil in cases where the candidate server
// entry should be skipped.
//
// To support replay, the caller must call DialParameters.Succeeded when a
// successful tunnel is established with the returned DialParameters; and must
// call DialParameters.Failed when a tunnel dial or activation fails, except
// when establishment is cancelled.
func MakeDialParameters(
config *Config,
canReplay func(serverEntry *protocol.ServerEntry, replayProtocol string) bool,
selectProtocol func(serverEntry *protocol.ServerEntry) (string, bool),
serverEntry *protocol.ServerEntry,
isTactics bool) (*DialParameters, error) {
networkID := config.GetNetworkID()
p := config.clientParameters.Get()
ttl := p.Duration(parameters.ReplayDialParametersTTL)
replaySSH := p.Bool(parameters.ReplaySSH)
replayObfuscatorPadding := p.Bool(parameters.ReplayObfuscatorPadding)
replayFragmentor := p.Bool(parameters.ReplayFragmentor)
replayTLSProfile := p.Bool(parameters.ReplayTLSProfile)
replayRandomizedTLSProfile := p.Bool(parameters.ReplayRandomizedTLSProfile)
replayFronting := p.Bool(parameters.ReplayFronting)
replayHostname := p.Bool(parameters.ReplayHostname)
replayQUICVersion := p.Bool(parameters.ReplayQUICVersion)
replayObfuscatedQUIC := p.Bool(parameters.ReplayObfuscatedQUIC)
replayLivenessTest := p.Bool(parameters.ReplayLivenessTest)
replayUserAgent := p.Bool(parameters.ReplayUserAgent)
replayAPIRequestPadding := p.Bool(parameters.ReplayAPIRequestPadding)
// Check for existing dial parameters for this server/network ID.
dialParams, err := GetDialParameters(serverEntry.IpAddress, networkID)
if err != nil {
NoticeAlert("GetDialParameters failed: %s", err)
dialParams = nil
// Proceed, without existing dial parameters.
}
// Check if replay is permitted:
// - TTL must be > 0 and existing dial parameters must not have expired
// as indicated by LastUsedTimestamp + TTL.
// - Config/tactics/server entry values must be unchanged from when
// previous dial parameters were established.
// - The protocol selection constraints must permit replay, as indicated
// by canReplay.
//
// When existing dial parameters don't meet these conditions, dialParams
// is reset to nil and new dial parameters will be generated.
var currentTimestamp time.Time
var configStateHash []byte
// When TTL is 0, replay is disabled; the timestamp remains 0 and the
// output DialParameters will not be stored by Success.
if ttl > 0 {
currentTimestamp = time.Now()
configStateHash = getConfigStateHash(config, p, serverEntry)
}
if dialParams != nil &&
(ttl <= 0 ||
dialParams.LastUsedTimestamp.Before(currentTimestamp.Add(-ttl)) ||
bytes.Compare(dialParams.LastUsedConfigStateHash, configStateHash) != 0) {
// In these cases, existing dial parameters are expired or no longer
// match the config state and so are cleared to avoid rechecking them.
err = DeleteDialParameters(serverEntry.IpAddress, networkID)
if err != nil {
NoticeAlert("DeleteDialParameters failed: %s", err)
}
dialParams = nil
}
if dialParams != nil {
if !canReplay(serverEntry, dialParams.TunnelProtocol) {
// In this ephemeral case, existing dial parameters may still be
// valid and used in future establishment phases, and so are
// retained.
dialParams = nil
}
}
isReplay := (dialParams != nil)
if !isReplay {
dialParams = &DialParameters{}
}
dialParams.ServerEntry = serverEntry
dialParams.NetworkID = networkID
dialParams.IsReplay = isReplay
// Even when replaying, LastUsedTimestamp is updated to extend the TTL of
// replayed dial parameters which will be updated in the datastore upon
// success.
dialParams.LastUsedTimestamp = currentTimestamp
dialParams.LastUsedConfigStateHash = configStateHash
// Initialize dial parameters.
//
// When not replaying, all required parameters are initialized. When
// replaying, existing parameters are retaing, subject to the replay-X
// tactics flags.
if !isReplay {
// TODO: should there be a pre-check of selectProtocol before incurring
// overhead of unmarshaling dial parameters? In may be that a server entry
// is fully incapable of satisfying the current protocol selection
// constraints.
selectedProtocol, ok := selectProtocol(serverEntry)
if !ok {
return nil, nil
}
dialParams.TunnelProtocol = selectedProtocol
}
if !isReplay || !replaySSH {
dialParams.SelectedSSHClientVersion = true
dialParams.SSHClientVersion = pickSSHClientVersion()
dialParams.SSHKEXSeed, err = prng.NewSeed()
if err != nil {
return nil, common.ContextError(err)
}
}
if !isReplay || !replayObfuscatorPadding {
dialParams.ObfuscatorPaddingSeed, err = prng.NewSeed()
if err != nil {
return nil, common.ContextError(err)
}
if protocol.TunnelProtocolUsesMeek(dialParams.TunnelProtocol) {
dialParams.MeekObfuscatorPaddingSeed, err = prng.NewSeed()
if err != nil {
return nil, common.ContextError(err)
}
}
}
if !isReplay || !replayFragmentor {
dialParams.FragmentorSeed, err = prng.NewSeed()
if err != nil {
return nil, common.ContextError(err)
}
}
if (!isReplay || !replayTLSProfile) &&
protocol.TunnelProtocolUsesMeekHTTPS(dialParams.TunnelProtocol) {
dialParams.TLSProfile = SelectTLSProfile(p)
}
if (!isReplay || !replayRandomizedTLSProfile) &&
protocol.TunnelProtocolUsesMeekHTTPS(dialParams.TunnelProtocol) &&
protocol.TLSProfileIsRandomized(dialParams.TLSProfile) {
dialParams.RandomizedTLSProfileSeed, err = prng.NewSeed()
if err != nil {
return nil, common.ContextError(err)
}
}
if (!isReplay || !replayFronting) &&
protocol.TunnelProtocolUsesFrontedMeek(dialParams.TunnelProtocol) {
dialParams.MeekFrontingDialAddress, dialParams.MeekFrontingHost, err =
selectFrontingParameters(serverEntry)
if err != nil {
return nil, common.ContextError(err)
}
}
if !isReplay || !replayHostname {
if protocol.TunnelProtocolUsesQUIC(dialParams.TunnelProtocol) {
dialParams.QUICDialSNIAddress = fmt.Sprintf("%s:%d", common.GenerateHostName(), serverEntry.SshObfuscatedQUICPort)
} else if protocol.TunnelProtocolUsesMeekHTTPS(dialParams.TunnelProtocol) {
dialParams.MeekSNIServerName = ""
if p.WeightedCoinFlip(parameters.TransformHostNameProbability) {
dialParams.MeekSNIServerName = common.GenerateHostName()
dialParams.MeekTransformedHostName = true
}
} else if protocol.TunnelProtocolUsesMeekHTTP(dialParams.TunnelProtocol) {
dialParams.MeekHostHeader = ""
hostname := serverEntry.IpAddress
if p.WeightedCoinFlip(parameters.TransformHostNameProbability) {
hostname = common.GenerateHostName()
dialParams.MeekTransformedHostName = true
}
if serverEntry.MeekServerPort == 80 {
dialParams.MeekHostHeader = hostname
} else {
dialParams.MeekHostHeader = fmt.Sprintf("%s:%d", hostname, serverEntry.MeekServerPort)
}
}
}
if (!isReplay || !replayQUICVersion) &&
protocol.TunnelProtocolUsesQUIC(dialParams.TunnelProtocol) {
dialParams.QUICVersion = selectQUICVersion(p)
}
if (!isReplay || !replayObfuscatedQUIC) &&
protocol.QUICVersionIsObfuscated(dialParams.QUICVersion) {
dialParams.ObfuscatedQUICPaddingSeed, err = prng.NewSeed()
if err != nil {
return nil, common.ContextError(err)
}
}
if !isReplay || !replayLivenessTest {
// TODO: initialize only when LivenessTestMaxUp/DownstreamBytes > 0?
dialParams.LivenessTestSeed, err = prng.NewSeed()
if err != nil {
return nil, common.ContextError(err)
}
}
if !isReplay || !replayAPIRequestPadding {
dialParams.APIRequestPaddingSeed, err = prng.NewSeed()
if err != nil {
return nil, common.ContextError(err)
}
}
// Set dial address fields. This portion of configuration is
// deterministic, given the parameters established or replayed so far.
switch dialParams.TunnelProtocol {
case protocol.TUNNEL_PROTOCOL_SSH:
dialParams.DirectDialAddress = fmt.Sprintf("%s:%d", serverEntry.IpAddress, serverEntry.SshPort)
case protocol.TUNNEL_PROTOCOL_OBFUSCATED_SSH:
dialParams.DirectDialAddress = fmt.Sprintf("%s:%d", serverEntry.IpAddress, serverEntry.SshObfuscatedPort)
case protocol.TUNNEL_PROTOCOL_TAPDANCE_OBFUSCATED_SSH:
dialParams.DirectDialAddress = fmt.Sprintf("%s:%d", serverEntry.IpAddress, serverEntry.SshObfuscatedTapdancePort)
case protocol.TUNNEL_PROTOCOL_QUIC_OBFUSCATED_SSH:
dialParams.DirectDialAddress = fmt.Sprintf("%s:%d", serverEntry.IpAddress, serverEntry.SshObfuscatedQUICPort)
case protocol.TUNNEL_PROTOCOL_MARIONETTE_OBFUSCATED_SSH:
// Note: port comes from marionnete "format"
dialParams.DirectDialAddress = serverEntry.IpAddress
case protocol.TUNNEL_PROTOCOL_FRONTED_MEEK:
dialParams.MeekDialAddress = fmt.Sprintf("%s:443", dialParams.MeekFrontingDialAddress)
dialParams.MeekHostHeader = dialParams.MeekFrontingHost
if serverEntry.MeekFrontingDisableSNI {
dialParams.MeekSNIServerName = ""
} else if !dialParams.MeekTransformedHostName {
dialParams.MeekSNIServerName = dialParams.MeekFrontingDialAddress
}
case protocol.TUNNEL_PROTOCOL_FRONTED_MEEK_HTTP:
dialParams.MeekDialAddress = fmt.Sprintf("%s:80", dialParams.MeekFrontingDialAddress)
dialParams.MeekHostHeader = dialParams.MeekFrontingHost
case protocol.TUNNEL_PROTOCOL_UNFRONTED_MEEK:
dialParams.MeekDialAddress = fmt.Sprintf("%s:%d", serverEntry.IpAddress, serverEntry.MeekServerPort)
if !dialParams.MeekTransformedHostName {
if serverEntry.MeekServerPort == 80 {
dialParams.MeekHostHeader = serverEntry.IpAddress
} else {
dialParams.MeekHostHeader = dialParams.MeekDialAddress
}
}
case protocol.TUNNEL_PROTOCOL_UNFRONTED_MEEK_HTTPS,
protocol.TUNNEL_PROTOCOL_UNFRONTED_MEEK_SESSION_TICKET:
dialParams.MeekDialAddress = fmt.Sprintf("%s:%d", serverEntry.IpAddress, serverEntry.MeekServerPort)
if !dialParams.MeekTransformedHostName {
// Note: IP address in SNI field will be omitted.
dialParams.MeekSNIServerName = serverEntry.IpAddress
}
if serverEntry.MeekServerPort == 443 {
dialParams.MeekHostHeader = serverEntry.IpAddress
} else {
dialParams.MeekHostHeader = dialParams.MeekDialAddress
}
default:
return nil, common.ContextError(
fmt.Errorf("unknown tunnel protocol: %s", dialParams.TunnelProtocol))
}
if protocol.TunnelProtocolUsesMeek(dialParams.TunnelProtocol) {
host, port, _ := net.SplitHostPort(dialParams.MeekDialAddress)
if p.Bool(parameters.MeekDialDomainsOnly) {
if net.ParseIP(host) != nil {
// No error, as this is a "not supported" case.
return nil, nil
}
}
dialParams.DialPortNumber = port
// The underlying TLS will automatically disable SNI for IP address server name
// values; we have this explicit check here so we record the correct value for stats.
if net.ParseIP(dialParams.MeekSNIServerName) != nil {
dialParams.MeekSNIServerName = ""
}
} else {
_, dialParams.DialPortNumber, _ = net.SplitHostPort(dialParams.DirectDialAddress)
}
// Initialize/replay User-Agent header for HTTP upstream proxy and meek protocols.
if config.UseUpstreamProxy() {
// Note: UpstreamProxyURL will be validated in the dial
proxyURL, err := url.Parse(config.UpstreamProxyURL)
if err == nil {
dialParams.UpstreamProxyType = proxyURL.Scheme
}
}
dialCustomHeaders := makeDialCustomHeaders(config, p)
if protocol.TunnelProtocolUsesMeek(dialParams.TunnelProtocol) || dialParams.UpstreamProxyType == "http" {
if !isReplay || !replayUserAgent {
dialParams.SelectedUserAgent, dialParams.UserAgent = PickUserAgentIfUnset(p, dialCustomHeaders)
}
if dialParams.SelectedUserAgent {
dialCustomHeaders.Set("User-Agent", dialParams.UserAgent)
}
}
// UpstreamProxyCustomHeaderNames is a reported metric. Just the names and
// not the values are reported, in case the values are identifying.
if len(config.CustomHeaders) > 0 {
dialParams.UpstreamProxyCustomHeaderNames = make([]string, 0)
for name := range dialCustomHeaders {
if name == "User-Agent" && dialParams.SelectedUserAgent {
continue
}
dialParams.UpstreamProxyCustomHeaderNames = append(dialParams.UpstreamProxyCustomHeaderNames, name)
}
}
// Initialize Dial/MeekConfigs to be passed to the corresponding dialers.
dialParams.dialConfig = &DialConfig{
UpstreamProxyURL: config.UpstreamProxyURL,
CustomHeaders: dialCustomHeaders,
DeviceBinder: config.deviceBinder,
DnsServerGetter: config.DnsServerGetter,
IPv6Synthesizer: config.IPv6Synthesizer,
TrustedCACertificatesFilename: config.TrustedCACertificatesFilename,
FragmentorConfig: fragmentor.NewUpstreamConfig(p, dialParams.TunnelProtocol, dialParams.FragmentorSeed),
}
if protocol.TunnelProtocolUsesMeek(dialParams.TunnelProtocol) {
dialParams.meekConfig = &MeekConfig{
ClientParameters: config.clientParameters,
DialAddress: dialParams.MeekDialAddress,
UseHTTPS: protocol.TunnelProtocolUsesMeekHTTPS(dialParams.TunnelProtocol),
TLSProfile: dialParams.TLSProfile,
RandomizedTLSProfileSeed: dialParams.RandomizedTLSProfileSeed,
UseObfuscatedSessionTickets: dialParams.TunnelProtocol == protocol.TUNNEL_PROTOCOL_UNFRONTED_MEEK_SESSION_TICKET,
SNIServerName: dialParams.MeekSNIServerName,
HostHeader: dialParams.MeekHostHeader,
TransformedHostName: dialParams.MeekTransformedHostName,
ClientTunnelProtocol: dialParams.TunnelProtocol,
MeekCookieEncryptionPublicKey: serverEntry.MeekCookieEncryptionPublicKey,
MeekObfuscatedKey: serverEntry.MeekObfuscatedKey,
MeekObfuscatorPaddingSeed: dialParams.MeekObfuscatorPaddingSeed,
}
if isTactics {
dialParams.meekConfig.RoundTripperOnly = true
}
}
// Initialize MeekResolvedIPAddress, so a valid string can always be read.
dialParams.MeekResolvedIPAddress.Store("")
return dialParams, nil
}
func (dialParams *DialParameters) GetDialConfig() *DialConfig {
return dialParams.dialConfig
}
func (dialParams *DialParameters) GetMeekConfig() *MeekConfig {
return dialParams.meekConfig
}
func (dialParams *DialParameters) Succeeded() {
// When TTL is 0, don't store dial parameters.
if dialParams.LastUsedTimestamp.IsZero() {
return
}
NoticeInfo("Set dial parameters for %s", dialParams.ServerEntry.IpAddress)
err := SetDialParameters(dialParams.ServerEntry.IpAddress, dialParams.NetworkID, dialParams)
if err != nil {
NoticeAlert("SetDialParameters failed: %s", err)
}
}
func (dialParams *DialParameters) Failed() {
// When a tunnel fails, and the dial is a replay, clear the stored dial
// parameters which are now presumed to be blocked, impaired or otherwise
// no longer effective.
//
// It may be the case that a dial is not using stored dial parameters, and
// in this case we retain those dial parameters since they were not
// exercised and may still be efective.
if dialParams.IsReplay {
NoticeInfo("Delete dial parameters for %s", dialParams.ServerEntry.IpAddress)
err := DeleteDialParameters(dialParams.ServerEntry.IpAddress, dialParams.NetworkID)
if err != nil {
NoticeAlert("DeleteDialParameters failed: %s", err)
}
}
}
func getConfigStateHash(
config *Config,
p *parameters.ClientParametersSnapshot,
serverEntry *protocol.ServerEntry) []byte {
// The config state hash should reflect config, tactics, and server entry
// settings that impact the dial parameters. The hash should change if any
// of these input values change in a way that invalidates any stored dial
// parameters.
// MD5 hash is used solely as a data checksum and not for any security purpose.
hash := md5.New()
hash.Write([]byte(p.Tag()))
// TODO: marshal entire server entry?
var serverEntryConfigurationVersion [8]byte
binary.BigEndian.PutUint64(
serverEntryConfigurationVersion[:],
uint64(serverEntry.ConfigurationVersion))
hash.Write(serverEntryConfigurationVersion[:])
hash.Write([]byte(serverEntry.LocalTimestamp))
// TODO: add config.CustomHeaders, which could impact User-Agent header?
hash.Write([]byte(config.UpstreamProxyURL))
return hash.Sum(nil)
}
func selectFrontingParameters(serverEntry *protocol.ServerEntry) (string, string, error) {
frontingDialHost := ""
frontingHost := ""
if len(serverEntry.MeekFrontingAddressesRegex) > 0 {
// Generate a front address based on the regex.
var err error
frontingDialHost, err = regen.Generate(serverEntry.MeekFrontingAddressesRegex)
if err != nil {
return "", "", common.ContextError(err)
}
} else {
// Randomly select, for this connection attempt, one front address for
// fronting-capable servers.
if len(serverEntry.MeekFrontingAddresses) == 0 {
return "", "", common.ContextError(errors.New("MeekFrontingAddresses is empty"))
}
index := prng.Intn(len(serverEntry.MeekFrontingAddresses))
frontingDialHost = serverEntry.MeekFrontingAddresses[index]
}
if len(serverEntry.MeekFrontingHosts) > 0 {
index := prng.Intn(len(serverEntry.MeekFrontingHosts))
frontingHost = serverEntry.MeekFrontingHosts[index]
} else {
// Backwards compatibility case
frontingHost = serverEntry.MeekFrontingHost
}
return frontingDialHost, frontingHost, nil
}
func selectQUICVersion(p *parameters.ClientParametersSnapshot) string {
limitQUICVersions := p.QUICVersions(parameters.LimitQUICVersions)
quicVersions := make([]string, 0)
for _, quicVersion := range protocol.SupportedQUICVersions {
if len(limitQUICVersions) > 0 &&
!common.Contains(limitQUICVersions, quicVersion) {
continue
}
quicVersions = append(quicVersions, quicVersion)
}
if len(quicVersions) == 0 {
return ""
}
choice := prng.Intn(len(quicVersions))
return quicVersions[choice]
}
func makeDialCustomHeaders(
config *Config,
p *parameters.ClientParametersSnapshot) http.Header {
dialCustomHeaders := make(http.Header)
if config.CustomHeaders != nil {
for k, v := range config.CustomHeaders {
dialCustomHeaders[k] = make([]string, len(v))
copy(dialCustomHeaders[k], v)
}
}
additionalCustomHeaders := p.HTTPHeaders(parameters.AdditionalCustomHeaders)
if additionalCustomHeaders != nil {
for k, v := range additionalCustomHeaders {
dialCustomHeaders[k] = make([]string, len(v))
copy(dialCustomHeaders[k], v)
}
}
return dialCustomHeaders
}