/
meekConn.go
1781 lines (1512 loc) · 59.7 KB
/
meekConn.go
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/*
* Copyright (c) 2015, 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"
"context"
"crypto/rand"
"crypto/tls"
"encoding/base64"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net"
"net/http"
"net/url"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/astaguna/popon-core/psiphon/common"
"github.com/astaguna/popon-core/psiphon/common/errors"
"github.com/astaguna/popon-core/psiphon/common/obfuscator"
"github.com/astaguna/popon-core/psiphon/common/parameters"
"github.com/astaguna/popon-core/psiphon/common/prng"
"github.com/astaguna/popon-core/psiphon/common/protocol"
"github.com/astaguna/popon-core/psiphon/common/quic"
"github.com/astaguna/popon-core/psiphon/common/transforms"
"github.com/astaguna/popon-core/psiphon/common/values"
"github.com/astaguna/popon-core/psiphon/upstreamproxy"
"golang.org/x/crypto/nacl/box"
"golang.org/x/net/http2"
)
// MeekConn is based on meek-client.go from Tor:
//
// https://gitweb.torproject.org/pluggable-transports/meek.git/blob/HEAD:/meek-client/meek-client.go
// CC0 1.0 Universal
const (
MEEK_PROTOCOL_VERSION = 3
MEEK_MAX_REQUEST_PAYLOAD_LENGTH = 65536
)
type MeekMode int
const (
MeekModeRelay = iota
MeekModeObfuscatedRoundTrip
MeekModePlaintextRoundTrip
)
// MeekConfig specifies the behavior of a MeekConn.
type MeekConfig struct {
// DiagnosticID is the server ID to record in any diagnostics notices.
DiagnosticID string
// Parameters is the active set of parameters.Parameters to use
// for the meek dial.
Parameters *parameters.Parameters
// Mode selects the mode of operation:
//
// MeekModeRelay: encapsulates net.Conn flows in HTTP requests and responses;
// secures and obfuscates metadata in an encrypted HTTP cookie, making it
// suitable for non-TLS HTTP and HTTPS with unverifed server certificates;
// the caller is responsible for securing and obfuscating the net.Conn flows;
// the origin server should be a meek server; used for the meek tunnel
// protocols.
//
// MeekModeObfuscatedRoundTrip: enables ObfuscatedRoundTrip, which performs
// HTTP round trips; secures and obfuscates metadata, including the end point
// (or path), in an encrypted HTTP cookie, making it suitable for non-TLS
// HTTP and HTTPS with unverifed server certificates; the caller is
// responsible for securing and obfuscating request/response payloads; the
// origin server should be a meek server; used for tactics requests.
//
// MeekModePlaintextRoundTrip: enables RoundTrip; the MeekConn is an
// http.RoundTripper; there are no security or obfuscation measures at the
// HTTP level; TLS and server certificate verification is required; the
// origin server may be any HTTP(S) server.
//
// As with the other modes, MeekModePlaintextRoundTrip supports HTTP/2 with
// utls, and integration with DialParameters for replay -- which are not
// otherwise implemented if using just CustomTLSDialer and net.http.
Mode MeekMode
// DialAddress is the actual network address to dial to establish a
// connection to the meek server. This may be either a fronted or
// direct address. The address must be in the form "host:port",
// where host may be a domain name or IP address.
DialAddress string
// UseQUIC indicates whether to use HTTP/2 over QUIC.
UseQUIC bool
// QUICVersion indicates which QUIC version to use.
QUICVersion string
// QUICClientHelloSeed is used for randomized QUIC Client Hellos.
QUICClientHelloSeed *prng.Seed
// QUICDisablePathMTUDiscovery indicates whether to disable path MTU
// discovery in the QUIC client.
QUICDisablePathMTUDiscovery bool
// UseHTTPS indicates whether to use HTTPS (true) or HTTP (false).
UseHTTPS bool
// TLSProfile specifies the value for CustomTLSConfig.TLSProfile for all
// underlying TLS connections created by this meek connection.
TLSProfile string
// LegacyPassthrough indicates that the server expects a legacy passthrough
// message.
LegacyPassthrough bool
// NoDefaultTLSSessionID specifies the value for
// CustomTLSConfig.NoDefaultTLSSessionID for all underlying TLS connections
// created by this meek connection.
NoDefaultTLSSessionID bool
// RandomizedTLSProfileSeed specifies the value for
// CustomTLSConfig.RandomizedTLSProfileSeed for all underlying TLS
// connections created by this meek connection.
RandomizedTLSProfileSeed *prng.Seed
// UseObfuscatedSessionTickets indicates whether to use obfuscated session
// tickets. Assumes UseHTTPS is true. Ignored for MeekModePlaintextRoundTrip.
UseObfuscatedSessionTickets bool
// SNIServerName is the value to place in the TLS/QUIC SNI server_name field
// when HTTPS or QUIC is used.
SNIServerName string
// HostHeader is the value to place in the HTTP request Host header.
HostHeader string
// TransformedHostName records whether a hostname transformation is
// in effect. This value is used for stats reporting.
TransformedHostName bool
// AddPsiphonFrontingHeader specifies whether to add the
// X-Psiphon-Fronting-Address custom header.
AddPsiphonFrontingHeader bool
// VerifyServerName specifies a domain name that must appear in the server
// certificate. When blank, server certificate verification is disabled.
VerifyServerName string
// VerifyPins specifies one or more certificate pin values, one of which must
// appear in the verified server certificate chain. A pin value is the
// base64-encoded SHA2 digest of a certificate's public key. When specified,
// at least one pin must match at least one certificate in the chain, at any
// position; e.g., the root CA may be pinned, or the server certificate,
// etc.
VerifyPins []string
// DisableSystemRootCAs, when true, disables loading system root CAs when
// verifying the server certificate chain. Set DisableSystemRootCAs only in
// cases where system root CAs cannot be loaded; for example, if
// unsupported (iOS < 12) or insufficient memory (VPN extension on iOS <
// 15).
//
// When DisableSystemRootCAs and VerifyServerName are set, VerifyPins must
// be set.
DisableSystemRootCAs bool
// ClientTunnelProtocol is the protocol the client is using. It's included in
// the meek cookie for optional use by the server, in cases where the server
// cannot unambiguously determine the tunnel protocol. ClientTunnelProtocol
// is used when selecting tactics targeted at specific protocols. Ignored for
// MeekModePlaintextRoundTrip.
ClientTunnelProtocol string
// NetworkLatencyMultiplier specifies a custom network latency multiplier to
// apply to client parameters used by this meek connection.
NetworkLatencyMultiplier float64
// The following values are used to create the obfuscated meek cookie.
// Ignored for MeekModePlaintextRoundTrip.
MeekCookieEncryptionPublicKey string
MeekObfuscatedKey string
MeekObfuscatorPaddingSeed *prng.Seed
// HTTPTransformerParameters specifies an HTTP transformer to apply to the
// meek connection if it uses HTTP.
HTTPTransformerParameters *transforms.HTTPTransformerParameters
}
// MeekConn is a network connection that tunnels net.Conn flows over HTTP and supports
// "domain fronting". Meek sends client->server flow in HTTP request bodies and
// receives server->client flow in HTTP response bodies. Polling is used to
// approximate full duplex TCP. MeekConn also offers HTTP round trip modes.
//
// Domain fronting is a network obfuscation technique in which the connection to a web
// server, typically a CDN, is indistinguishable from any other HTTPS
// connection to the generic "fronting domain" -- the HTTP Host header is used
// to route the requests to the actual destination. See
// https://trac.torproject.org/projects/tor/wiki/doc/meek for more details.
//
// MeekConn also support unfronted operation, in which connections are made
// without routing through a CDN; and plain HTTP operation, without TLS or
// QUIC, with connection metadata obfuscated in HTTP cookies.
type MeekConn struct {
params *parameters.Parameters
mode MeekMode
networkLatencyMultiplier float64
isQUIC bool
url *url.URL
additionalHeaders http.Header
cookie *http.Cookie
contentType string
cookieSize int
tlsPadding int
limitRequestPayloadLength int
redialTLSProbability float64
underlyingDialer common.Dialer
cachedTLSDialer *cachedTLSDialer
transport transporter
mutex sync.Mutex
isClosed bool
runCtx context.Context
stopRunning context.CancelFunc
relayWaitGroup *sync.WaitGroup
firstUnderlyingConn net.Conn
// For MeekModeObfuscatedRoundTrip
meekCookieEncryptionPublicKey string
meekObfuscatedKey string
meekObfuscatorPaddingSeed *prng.Seed
clientTunnelProtocol string
// For MeekModeRelay
fullReceiveBufferLength int
readPayloadChunkLength int
emptyReceiveBuffer chan *bytes.Buffer
partialReceiveBuffer chan *bytes.Buffer
fullReceiveBuffer chan *bytes.Buffer
emptySendBuffer chan *bytes.Buffer
partialSendBuffer chan *bytes.Buffer
fullSendBuffer chan *bytes.Buffer
}
func (conn *MeekConn) getCustomParameters() parameters.ParametersAccessor {
return conn.params.GetCustom(conn.networkLatencyMultiplier)
}
// transporter is implemented by both http.Transport and upstreamproxy.ProxyAuthTransport.
type transporter interface {
CloseIdleConnections()
RoundTrip(req *http.Request) (resp *http.Response, err error)
}
// DialMeek returns an initialized meek connection. A meek connection is
// an HTTP session which does not depend on an underlying socket connection (although
// persistent HTTP connections are used for performance). This function may not
// wait for the connection to be established before returning.
func DialMeek(
ctx context.Context,
meekConfig *MeekConfig,
dialConfig *DialConfig) (*MeekConn, error) {
if meekConfig.UseQUIC && meekConfig.UseHTTPS {
return nil, errors.TraceNew(
"invalid config: only one of UseQUIC or UseHTTPS may be set")
}
if meekConfig.UseQUIC &&
(meekConfig.VerifyServerName != "" || len(meekConfig.VerifyPins) > 0) {
// TODO: UseQUIC VerifyServerName and VerifyPins support (required for MeekModePlaintextRoundTrip).
return nil, errors.TraceNew(
"invalid config: VerifyServerName and VerifyPins not supported for UseQUIC")
}
skipVerify := meekConfig.VerifyServerName == ""
if len(meekConfig.VerifyPins) > 0 && skipVerify {
return nil, errors.TraceNew(
"invalid config: VerifyServerName must be set when VerifyPins is set")
}
if meekConfig.DisableSystemRootCAs && !skipVerify &&
(len(meekConfig.VerifyServerName) == 0 || len(meekConfig.VerifyPins) == 0) {
return nil, errors.TraceNew(
"invalid config: VerifyServerName and VerifyPins must be set when DisableSystemRootCAs is set")
}
if meekConfig.Mode == MeekModePlaintextRoundTrip &&
(!meekConfig.UseHTTPS || skipVerify) {
return nil, errors.TraceNew(
"invalid config: MeekModePlaintextRoundTrip requires UseHTTPS and VerifyServerName")
}
runCtx, stopRunning := context.WithCancel(context.Background())
cleanupStopRunning := true
cleanupCachedTLSDialer := true
var cachedTLSDialer *cachedTLSDialer
// Cleanup in error cases
defer func() {
if cleanupStopRunning {
stopRunning()
}
if cleanupCachedTLSDialer && cachedTLSDialer != nil {
cachedTLSDialer.close()
}
}()
meek := &MeekConn{
params: meekConfig.Parameters,
mode: meekConfig.Mode,
networkLatencyMultiplier: meekConfig.NetworkLatencyMultiplier,
isClosed: false,
runCtx: runCtx,
stopRunning: stopRunning,
relayWaitGroup: new(sync.WaitGroup),
}
if meek.mode == MeekModeRelay {
var err error
meek.cookie,
meek.contentType,
meek.tlsPadding,
meek.limitRequestPayloadLength,
meek.redialTLSProbability,
err =
makeMeekObfuscationValues(
meek.getCustomParameters(),
meekConfig.MeekCookieEncryptionPublicKey,
meekConfig.MeekObfuscatedKey,
meekConfig.MeekObfuscatorPaddingSeed,
meekConfig.ClientTunnelProtocol,
"")
if err != nil {
return nil, errors.Trace(err)
}
// For stats, record the size of the initial obfuscated cookie.
meek.cookieSize = len(meek.cookie.Name) + len(meek.cookie.Value)
}
// Configure transport: QUIC or HTTPS or HTTP
var (
scheme string
opaqueURL string
transport transporter
additionalHeaders http.Header
proxyUrl func(*http.Request) (*url.URL, error)
)
if meekConfig.UseQUIC {
meek.isQUIC = true
scheme = "https"
udpDialer := func(ctx context.Context) (net.PacketConn, *net.UDPAddr, error) {
packetConn, remoteAddr, err := NewUDPConn(
ctx,
meekConfig.DialAddress,
dialConfig)
if err != nil {
return nil, nil, errors.Trace(err)
}
return packetConn, remoteAddr, nil
}
var err error
transport, err = quic.NewQUICTransporter(
ctx,
func(message string) {
NoticeInfo(message)
},
udpDialer,
meekConfig.SNIServerName,
meekConfig.QUICVersion,
meekConfig.QUICClientHelloSeed,
meekConfig.QUICDisablePathMTUDiscovery)
if err != nil {
return nil, errors.Trace(err)
}
} else if meekConfig.UseHTTPS {
// Custom TLS dialer:
//
// 1. ignores the HTTP request address and uses the fronting domain
// 2. optionally disables SNI -- SNI breaks fronting when used with certain CDNs.
// 3. may skip verifying the server cert.
//
// Reasoning for #3:
//
// With a TLS MiM attack in place, and server certs verified, we'll fail to connect because the client
// will refuse to connect. That's not a successful outcome.
//
// With a MiM attack in place, and server certs not verified, we'll fail to connect if the MiM is actively
// targeting Psiphon and classifying the HTTP traffic by Host header or payload signature.
//
// However, in the case of a passive MiM that's just recording traffic or an active MiM that's targeting
// something other than Psiphon, the client will connect. This is a successful outcome.
//
// What is exposed to the MiM? The Host header does not contain a Psiphon server IP address, just an
// unrelated, randomly generated domain name which cannot be used to block direct connections. The
// Psiphon server IP is sent over meek, but it's in the encrypted cookie.
//
// The payload (user traffic) gets its confidentiality and integrity from the underlying SSH protocol.
// So, nothing is leaked to the MiM apart from signatures which could be used to classify the traffic
// as Psiphon to possibly block it; but note that not revealing that the client is Psiphon is outside
// our threat model; we merely seek to evade mass blocking by taking steps that require progressively
// more effort to block.
//
// There is a subtle attack remaining: an adversary that can MiM some CDNs but not others (and so can
// classify Psiphon traffic on some CDNs but not others) may throttle non-MiM CDNs so that our server
// selection always chooses tunnels to the MiM CDN (without any server cert verification, we won't
// exclusively connect to non-MiM CDNs); then the adversary kills the underlying TCP connection after
// some short period. This is partially mitigated by tactics mechanisms.
scheme = "https"
meek.initUnderlyingDialer(dialConfig)
tlsConfig := &CustomTLSConfig{
Parameters: meekConfig.Parameters,
DialAddr: meekConfig.DialAddress,
Dial: meek.underlyingDial,
SNIServerName: meekConfig.SNIServerName,
SkipVerify: skipVerify,
VerifyServerName: meekConfig.VerifyServerName,
VerifyPins: meekConfig.VerifyPins,
DisableSystemRootCAs: meekConfig.DisableSystemRootCAs,
TLSProfile: meekConfig.TLSProfile,
NoDefaultTLSSessionID: &meekConfig.NoDefaultTLSSessionID,
RandomizedTLSProfileSeed: meekConfig.RandomizedTLSProfileSeed,
TLSPadding: meek.tlsPadding,
TrustedCACertificatesFilename: dialConfig.TrustedCACertificatesFilename,
}
tlsConfig.EnableClientSessionCache()
if meekConfig.UseObfuscatedSessionTickets {
tlsConfig.ObfuscatedSessionTicketKey = meekConfig.MeekObfuscatedKey
}
if meekConfig.Mode != MeekModePlaintextRoundTrip &&
meekConfig.MeekObfuscatedKey != "" {
// As the passthrough message is unique and indistinguishable from a normal
// TLS client random value, we set it unconditionally and not just for
// protocols which may support passthrough (even for those protocols,
// clients don't know which servers are configured to use it).
passthroughMessage, err := obfuscator.MakeTLSPassthroughMessage(
!meekConfig.LegacyPassthrough,
meekConfig.MeekObfuscatedKey)
if err != nil {
return nil, errors.Trace(err)
}
tlsConfig.PassthroughMessage = passthroughMessage
}
tlsDialer := NewCustomTLSDialer(tlsConfig)
// Pre-dial one TLS connection in order to inspect the negotiated
// application protocol. Then we create an HTTP/2 or HTTP/1.1 transport
// depending on which protocol was negotiated. The TLS dialer
// is assumed to negotiate only "h2" or "http/1.1"; or not negotiate
// an application protocol.
//
// We cannot rely on net/http's HTTP/2 support since it's only
// activated when http.Transport.DialTLS returns a golang crypto/tls.Conn;
// e.g., https://github.com/golang/go/blob/c8aec4095e089ff6ac50d18e97c3f46561f14f48/src/net/http/transport.go#L1040
//
// The pre-dialed connection is stored in a cachedTLSDialer, which will
// return the cached pre-dialed connection to its first Dial caller, and
// use the tlsDialer for all other Dials.
//
// cachedTLSDialer.close() must be called on all exits paths from this
// function and in meek.Close() to ensure the cached conn is closed in
// any case where no Dial call is made.
//
// The pre-dial must be interruptible so that DialMeek doesn't block and
// hang/delay a shutdown or end of establishment. So the pre-dial uses
// the Controller's PendingConns, not the MeekConn PendingConns. For this
// purpose, a special preDialer is configured.
//
// Only one pre-dial attempt is made; there are no retries. This differs
// from relayRoundTrip, which retries and may redial for each retry.
// Retries at the pre-dial phase are less useful since there's no active
// session to preserve, and establishment will simply try another server.
// Note that the underlying TCPDial may still try multiple IP addreses when
// the destination is a domain and it resolves to multiple IP adresses.
// The pre-dial is made within the parent dial context, so that DialMeek
// may be interrupted. Subsequent dials are made within the meek round trip
// request context. Since http.DialTLS doesn't take a context argument
// (yet; as of Go 1.9 this issue is still open: https://github.com/golang/go/issues/21526),
// cachedTLSDialer is used as a conduit to send the request context.
// meekConn.relayRoundTrip sets its request context into cachedTLSDialer,
// and cachedTLSDialer.dial uses that context.
// As DialAddr is set in the CustomTLSConfig, no address is required here.
preConn, err := tlsDialer(ctx, "tcp", "")
if err != nil {
return nil, errors.Trace(err)
}
cachedTLSDialer = newCachedTLSDialer(preConn, tlsDialer)
if IsTLSConnUsingHTTP2(preConn) {
NoticeInfo("negotiated HTTP/2 for %s", meekConfig.DiagnosticID)
transport = &http2.Transport{
DialTLS: func(network, addr string, _ *tls.Config) (net.Conn, error) {
return cachedTLSDialer.dial(network, addr)
},
}
} else {
transport = &http.Transport{
DialTLS: func(network, addr string) (net.Conn, error) {
return cachedTLSDialer.dial(network, addr)
},
}
}
} else {
scheme = "http"
var dialer common.Dialer
// For HTTP, and when the meekConfig.DialAddress matches the
// meekConfig.HostHeader, we let http.Transport handle proxying.
// http.Transport will put the the HTTP server address in the HTTP
// request line. In this one case, we can use an HTTP proxy that does
// not offer CONNECT support.
if strings.HasPrefix(dialConfig.UpstreamProxyURL, "http://") &&
(meekConfig.DialAddress == meekConfig.HostHeader ||
meekConfig.DialAddress == meekConfig.HostHeader+":80") {
url, err := common.SafeParseURL(dialConfig.UpstreamProxyURL)
if err != nil {
return nil, errors.Trace(err)
}
proxyUrl = http.ProxyURL(url)
// Here, the dialer must use the address that http.Transport
// passes in (which will be proxy address).
copyDialConfig := new(DialConfig)
*copyDialConfig = *dialConfig
copyDialConfig.UpstreamProxyURL = ""
meek.initUnderlyingDialer(copyDialConfig)
dialer = meek.underlyingDial
// In this proxy case, the destination server address is in the
// request line URL. net/http will render the request line using
// the URL but preferring the Host header for the host value,
// which means any custom host header will clobber the true
// destination address. The URL.Opaque logic is applied in this
// case, to force the request line URL value.
//
// This URL.Opaque setting assumes MeekModeRelay, with no path; at
// this time plain HTTP is used only with MeekModeRelay.
// x/net/http2 will reject requests where the URL.Opaque contains
// more than the path; but HTTP/2 is not used in this case.
values := dialConfig.CustomHeaders["Host"]
if len(values) > 0 {
opaqueURL = "http://" + meekConfig.DialAddress + "/"
}
} else {
// If dialConfig.UpstreamProxyURL is set, HTTP proxying via
// CONNECT will be used by the dialer.
meek.initUnderlyingDialer(dialConfig)
baseDialer := meek.underlyingDial
// The dialer ignores any address that http.Transport will pass in
// (derived from the HTTP request URL) and always dials
// meekConfig.DialAddress.
dialer = func(ctx context.Context, network, _ string) (net.Conn, error) {
return baseDialer(ctx, network, meekConfig.DialAddress)
}
}
if protocol.TunnelProtocolUsesMeekHTTP(meekConfig.ClientTunnelProtocol) {
// Only apply transformer if it will perform a transform; otherwise
// applying a no-op transform will incur an unnecessary performance
// cost.
if meekConfig.HTTPTransformerParameters != nil && meekConfig.HTTPTransformerParameters.ProtocolTransformSpec != nil {
dialer = transforms.WrapDialerWithHTTPTransformer(dialer, meekConfig.HTTPTransformerParameters)
}
}
httpTransport := &http.Transport{
Proxy: proxyUrl,
DialContext: dialer,
}
if proxyUrl != nil {
// When http.Transport is handling proxying, wrap transport with a
// transport that (a) adds custom headers; (b) can perform HTTP
// proxy auth negotiation.
var err error
transport, err = upstreamproxy.NewProxyAuthTransport(
httpTransport, dialConfig.CustomHeaders)
if err != nil {
return nil, errors.Trace(err)
}
} else {
transport = httpTransport
}
}
url := &url.URL{
Scheme: scheme,
Host: meekConfig.HostHeader,
Path: "/",
Opaque: opaqueURL,
}
if scheme == "http" && proxyUrl == nil {
// Add custom headers to HTTP. This may be unproxied HTTP, or CONNECT
// method proxied HTTP, which is handled implicitly by DialTCP (in the
// latter case, the CONNECT request itself will also have custom
// headers via upstreamproxy applied by the dialer).
//
// When proxyUrl != nil, proxying is handled by http.Transport and
// custom headers are set in upstreamproxy.NewProxyAuthTransport, above.
additionalHeaders = dialConfig.CustomHeaders
} else {
additionalHeaders = make(http.Header)
// User-Agent is passed in via dialConfig.CustomHeaders. Always use
// any User-Agent header, even when not using all custom headers.
userAgent := dialConfig.CustomHeaders.Get("User-Agent")
if userAgent != "" {
additionalHeaders.Set("User-Agent", userAgent)
}
}
if meekConfig.AddPsiphonFrontingHeader {
host, _, err := net.SplitHostPort(meekConfig.DialAddress)
if err != nil {
return nil, errors.Trace(err)
}
additionalHeaders.Set("X-Psiphon-Fronting-Address", host)
}
meek.url = url
meek.additionalHeaders = additionalHeaders
meek.cachedTLSDialer = cachedTLSDialer
meek.transport = transport
// stopRunning and cachedTLSDialer will now be closed in meek.Close()
cleanupStopRunning = false
cleanupCachedTLSDialer = false
// Allocate relay resources, including buffers and running the relay
// go routine, only when running in relay mode.
if meek.mode == MeekModeRelay {
// The main loop of a MeekConn is run in the relay() goroutine.
// A MeekConn implements net.Conn concurrency semantics:
// "Multiple goroutines may invoke methods on a Conn simultaneously."
//
// Read() calls and relay() are synchronized by exchanging control of a single
// receiveBuffer (bytes.Buffer). This single buffer may be:
// - in the emptyReceiveBuffer channel when it is available and empty;
// - in the partialReadBuffer channel when it is available and contains data;
// - in the fullReadBuffer channel when it is available and full of data;
// - "checked out" by relay or Read when they are are writing to or reading from the
// buffer, respectively.
// relay() will obtain the buffer from either the empty or partial channel but block when
// the buffer is full. Read will obtain the buffer from the partial or full channel when
// there is data to read but block when the buffer is empty.
// Write() calls and relay() are synchronized in a similar way, using a single
// sendBuffer.
p := meek.getCustomParameters()
if p.Bool(parameters.MeekLimitBufferSizes) {
meek.fullReceiveBufferLength = p.Int(parameters.MeekLimitedFullReceiveBufferLength)
meek.readPayloadChunkLength = p.Int(parameters.MeekLimitedReadPayloadChunkLength)
} else {
meek.fullReceiveBufferLength = p.Int(parameters.MeekFullReceiveBufferLength)
meek.readPayloadChunkLength = p.Int(parameters.MeekReadPayloadChunkLength)
}
meek.emptyReceiveBuffer = make(chan *bytes.Buffer, 1)
meek.partialReceiveBuffer = make(chan *bytes.Buffer, 1)
meek.fullReceiveBuffer = make(chan *bytes.Buffer, 1)
meek.emptySendBuffer = make(chan *bytes.Buffer, 1)
meek.partialSendBuffer = make(chan *bytes.Buffer, 1)
meek.fullSendBuffer = make(chan *bytes.Buffer, 1)
meek.emptyReceiveBuffer <- new(bytes.Buffer)
meek.emptySendBuffer <- new(bytes.Buffer)
meek.relayWaitGroup.Add(1)
go meek.relay()
} else if meek.mode == MeekModeObfuscatedRoundTrip {
meek.meekCookieEncryptionPublicKey = meekConfig.MeekCookieEncryptionPublicKey
meek.meekObfuscatedKey = meekConfig.MeekObfuscatedKey
meek.meekObfuscatorPaddingSeed = meekConfig.MeekObfuscatorPaddingSeed
meek.clientTunnelProtocol = meekConfig.ClientTunnelProtocol
} else if meek.mode == MeekModePlaintextRoundTrip {
// MeekModeRelay and MeekModeObfuscatedRoundTrip set the Host header
// implicitly via meek.url; MeekModePlaintextRoundTrip does not use
// meek.url; it uses the RoundTrip input request.URL instead. So the
// Host header is set to meekConfig.HostHeader explicitly here.
meek.additionalHeaders.Add("Host", meekConfig.HostHeader)
}
return meek, nil
}
func (meek *MeekConn) initUnderlyingDialer(dialConfig *DialConfig) {
// Not safe for concurrent calls; should be called only from DialMeek.
meek.underlyingDialer = NewTCPDialer(dialConfig)
}
func (meek *MeekConn) underlyingDial(ctx context.Context, network, addr string) (net.Conn, error) {
conn, err := meek.underlyingDialer(ctx, network, addr)
if err == nil {
meek.mutex.Lock()
if meek.firstUnderlyingConn == nil {
// Keep a reference to the first underlying conn to be used as a
// common.MetricsSource in GetMetrics. This enables capturing
// metrics such as fragmentor configuration.
meek.firstUnderlyingConn = conn
}
meek.mutex.Unlock()
}
// Note: no trace error to preserve error type
return conn, err
}
type cachedTLSDialer struct {
usedCachedConn int32
cachedConn net.Conn
dialer common.Dialer
mutex sync.Mutex
requestCtx context.Context
}
func newCachedTLSDialer(cachedConn net.Conn, dialer common.Dialer) *cachedTLSDialer {
return &cachedTLSDialer{
cachedConn: cachedConn,
dialer: dialer,
}
}
func (c *cachedTLSDialer) setRequestContext(requestCtx context.Context) {
// Note: not using sync.Value since underlying type of requestCtx may change.
c.mutex.Lock()
defer c.mutex.Unlock()
c.requestCtx = requestCtx
}
func (c *cachedTLSDialer) dial(network, addr string) (net.Conn, error) {
if atomic.CompareAndSwapInt32(&c.usedCachedConn, 0, 1) {
conn := c.cachedConn
c.cachedConn = nil
return conn, nil
}
c.mutex.Lock()
ctx := c.requestCtx
c.mutex.Unlock()
if ctx == nil {
ctx = context.Background()
}
return c.dialer(ctx, network, addr)
}
func (c *cachedTLSDialer) close() {
if atomic.CompareAndSwapInt32(&c.usedCachedConn, 0, 1) {
c.cachedConn.Close()
c.cachedConn = nil
}
}
// Close terminates the meek connection and releases its resources. In in
// MeekModeRelay, Close waits for the relay goroutine to stop.
func (meek *MeekConn) Close() (err error) {
// A mutex is required to support net.Conn concurrency semantics.
meek.mutex.Lock()
isClosed := meek.isClosed
meek.isClosed = true
meek.mutex.Unlock()
if !isClosed {
meek.stopRunning()
if meek.cachedTLSDialer != nil {
meek.cachedTLSDialer.close()
}
// stopRunning interrupts HTTP requests in progress by closing the context
// associated with the request. In the case of h2quic.RoundTripper, testing
// indicates that quic-go.receiveStream.readImpl in _not_ interrupted in
// this case, and so an in-flight FRONTED-MEEK-QUIC round trip may hang shutdown
// in relayRoundTrip->readPayload->...->quic-go.receiveStream.readImpl.
//
// To workaround this, we call CloseIdleConnections _before_ Wait, as, in
// the case of QUICTransporter, this closes the underlying UDP sockets which
// interrupts any blocking I/O calls.
//
// The standard CloseIdleConnections call _after_ wait is for the net/http
// case: it only closes idle connections, so the call should be after wait.
// This call is intended to clean up all network resources deterministically
// before Close returns.
if meek.isQUIC {
meek.transport.CloseIdleConnections()
}
meek.relayWaitGroup.Wait()
meek.transport.CloseIdleConnections()
}
return nil
}
// IsClosed implements the Closer interface. The return value
// indicates whether the MeekConn has been closed.
func (meek *MeekConn) IsClosed() bool {
meek.mutex.Lock()
isClosed := meek.isClosed
meek.mutex.Unlock()
return isClosed
}
// GetMetrics implements the common.MetricsSource interface.
func (meek *MeekConn) GetMetrics() common.LogFields {
logFields := make(common.LogFields)
if meek.mode == MeekModeRelay {
logFields["meek_cookie_size"] = meek.cookieSize
logFields["meek_tls_padding"] = meek.tlsPadding
logFields["meek_limit_request"] = meek.limitRequestPayloadLength
logFields["meek_redial_probability"] = meek.redialTLSProbability
}
// Include metrics, such as fragmentor metrics, from the _first_ underlying
// dial conn. Properties of subsequent underlying dial conns are not reflected
// in these metrics; we assume that the first dial conn, which most likely
// transits the various protocol handshakes, is most significant.
meek.mutex.Lock()
underlyingMetrics, ok := meek.firstUnderlyingConn.(common.MetricsSource)
if ok {
logFields.Add(underlyingMetrics.GetMetrics())
}
meek.mutex.Unlock()
return logFields
}
// GetNoticeMetrics implements the common.NoticeMetricsSource interface.
func (meek *MeekConn) GetNoticeMetrics() common.LogFields {
// These fields are logged only in notices, for diagnostics. The server
// will log the same values, but derives them from HTTP headers, so they
// don't need to be sent in the API request.
logFields := make(common.LogFields)
logFields["meek_cookie_name"] = meek.cookie.Name
logFields["meek_content_type"] = meek.contentType
return logFields
}
// ObfuscatedRoundTrip makes a request to the meek server and returns the
// response. A new, obfuscated meek cookie is created for every request. The
// specified end point is recorded in the cookie and is not exposed as
// plaintext in the meek traffic. The caller is responsible for securing and
// obfuscating the request body.
//
// ObfuscatedRoundTrip is not safe for concurrent use. The caller must ensure
// only one ObfuscatedRoundTrip call is active at once. If Close is called
// before or concurrent with ObfuscatedRoundTrip, or before the response body
// is read, idle connections may be left open.
func (meek *MeekConn) ObfuscatedRoundTrip(
requestCtx context.Context, endPoint string, requestBody []byte) ([]byte, error) {
if meek.mode != MeekModeObfuscatedRoundTrip {
return nil, errors.TraceNew("operation unsupported")
}
cookie, contentType, _, _, _, err := makeMeekObfuscationValues(
meek.getCustomParameters(),
meek.meekCookieEncryptionPublicKey,
meek.meekObfuscatedKey,
meek.meekObfuscatorPaddingSeed,
meek.clientTunnelProtocol,
endPoint)
if err != nil {
return nil, errors.Trace(err)
}
// Note:
//
// - multiple, concurrent ObfuscatedRoundTrip calls are unsafe due to the
// setDialerRequestContext calls in newRequest.
//
// At this time, ObfuscatedRoundTrip is used for tactics in Controller and
// the concurrency constraints are satisfied.
request, err := meek.newRequest(
requestCtx, cookie, contentType, bytes.NewReader(requestBody), 0)
if err != nil {
return nil, errors.Trace(err)
}
meek.scheduleQUICCloseIdle(request)
response, err := meek.transport.RoundTrip(request)
if err == nil {
defer response.Body.Close()
if response.StatusCode != http.StatusOK {
err = fmt.Errorf("unexpected response status code: %d", response.StatusCode)
}
}
if err != nil {
return nil, errors.Trace(err)
}
responseBody, err := ioutil.ReadAll(response.Body)
if err != nil {
return nil, errors.Trace(err)
}
return responseBody, nil
}
// RoundTrip implements the http.RoundTripper interface. RoundTrip may only be
// used when TLS and server certificate verification are configured. RoundTrip
// does not implement any security or obfuscation at the HTTP layer.
//
// RoundTrip is not safe for concurrent use. The caller must ensure only one
// RoundTrip call is active at once. If Close is called before or concurrent
// with RoundTrip, or before the response body is read, idle connections may
// be left open.
func (meek *MeekConn) RoundTrip(request *http.Request) (*http.Response, error) {
if meek.mode != MeekModePlaintextRoundTrip {
return nil, errors.TraceNew("operation unsupported")
}
requestCtx := request.Context()
// Clone the request to apply addtional headers without modifying the input.
request = request.Clone(requestCtx)
meek.addAdditionalHeaders(request)
// The setDialerRequestContext/CloseIdleConnections concurrency note in
// ObfuscatedRoundTrip applies to RoundTrip as well.
// Ensure dials are made within the request context.
meek.setDialerRequestContext(requestCtx)
meek.scheduleQUICCloseIdle(request)
response, err := meek.transport.RoundTrip(request)