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)
}
return &sshServer{
support: support,
shutdownBroadcast: shutdownBroadcast,
sshHostKey: signer,
acceptedClientCounts: make(map[string]int64),
clients: make(map[string]*sshClient),
}, nil
}
// GenerateConfig creates a new Psiphon server config. It returns JSON
// encoded configs and a client-compatible "server entry" for the server. It
// generates all necessary secrets and key material, which are emitted in
// the config file and server entry as necessary.
// GenerateConfig uses sample values for many fields. The intention is for
// generated configs to be used for testing or as a template for production
// setup, not to generate production-ready configurations.
func GenerateConfig(params *GenerateConfigParams) ([]byte, []byte, []byte, error) {
// Input validation
if net.ParseIP(params.ServerIPAddress) == nil {
return nil, nil, nil, common.ContextError(errors.New("invalid IP address"))
}
if len(params.TunnelProtocolPorts) == 0 {
return nil, nil, nil, common.ContextError(errors.New("no tunnel protocols"))
}
usedPort := make(map[int]bool)
if params.WebServerPort != 0 {
usedPort[params.WebServerPort] = true
}
usingMeek := false
for protocol, port := range params.TunnelProtocolPorts {
if !common.Contains(common.SupportedTunnelProtocols, protocol) {
return nil, nil, nil, common.ContextError(errors.New("invalid tunnel protocol"))
}
if usedPort[port] {
return nil, nil, nil, common.ContextError(errors.New("duplicate listening port"))
}
usedPort[port] = true
if common.TunnelProtocolUsesMeekHTTP(protocol) ||
common.TunnelProtocolUsesMeekHTTPS(protocol) {
usingMeek = true
}
}
// Web server config
var webServerSecret, webServerCertificate,
webServerPrivateKey, webServerPortForwardAddress string
if params.WebServerPort != 0 {
var err error
webServerSecret, err = common.MakeRandomStringHex(WEB_SERVER_SECRET_BYTE_LENGTH)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
webServerCertificate, webServerPrivateKey, err = GenerateWebServerCertificate("")
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
webServerPortForwardAddress = net.JoinHostPort(
params.ServerIPAddress, strconv.Itoa(params.WebServerPort))
}
// SSH config
// TODO: use other key types: anti-fingerprint by varying params
rsaKey, err := rsa.GenerateKey(rand.Reader, SSH_RSA_HOST_KEY_BITS)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
sshPrivateKey := pem.EncodeToMemory(
&pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: x509.MarshalPKCS1PrivateKey(rsaKey),
},
)
signer, err := ssh.NewSignerFromKey(rsaKey)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
sshPublicKey := signer.PublicKey()
sshUserNameSuffix, err := common.MakeRandomStringHex(SSH_USERNAME_SUFFIX_BYTE_LENGTH)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
sshUserName := "******" + sshUserNameSuffix
sshPassword, err := common.MakeRandomStringHex(SSH_PASSWORD_BYTE_LENGTH)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
// TODO: vary version string for anti-fingerprint
sshServerVersion := "SSH-2.0-Psiphon"
// Obfuscated SSH config
obfuscatedSSHKey, err := common.MakeRandomStringHex(SSH_OBFUSCATED_KEY_BYTE_LENGTH)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
// Meek config
var meekCookieEncryptionPublicKey, meekCookieEncryptionPrivateKey, meekObfuscatedKey string
if usingMeek {
rawMeekCookieEncryptionPublicKey, rawMeekCookieEncryptionPrivateKey, err :=
box.GenerateKey(rand.Reader)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
meekCookieEncryptionPublicKey = base64.StdEncoding.EncodeToString(rawMeekCookieEncryptionPublicKey[:])
meekCookieEncryptionPrivateKey = base64.StdEncoding.EncodeToString(rawMeekCookieEncryptionPrivateKey[:])
meekObfuscatedKey, err = common.MakeRandomStringHex(SSH_OBFUSCATED_KEY_BYTE_LENGTH)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
}
// Other config
discoveryValueHMACKey, err := common.MakeRandomStringBase64(DISCOVERY_VALUE_KEY_BYTE_LENGTH)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
// Assemble configs and server entry
// Note: this config is intended for either testing or as an illustrative
// example or template and is not intended for production deployment.
config := &Config{
LogLevel: "info",
LogFilename: params.LogFilename,
GeoIPDatabaseFilenames: nil,
HostID: "example-host-id",
ServerIPAddress: params.ServerIPAddress,
DiscoveryValueHMACKey: discoveryValueHMACKey,
WebServerPort: params.WebServerPort,
WebServerSecret: webServerSecret,
WebServerCertificate: webServerCertificate,
WebServerPrivateKey: webServerPrivateKey,
WebServerPortForwardAddress: webServerPortForwardAddress,
SSHPrivateKey: string(sshPrivateKey),
SSHServerVersion: sshServerVersion,
SSHUserName: sshUserName,
SSHPassword: sshPassword,
ObfuscatedSSHKey: obfuscatedSSHKey,
TunnelProtocolPorts: params.TunnelProtocolPorts,
DNSResolverIPAddress: "8.8.8.8",
UDPInterceptUdpgwServerAddress: "127.0.0.1:7300",
MeekCookieEncryptionPrivateKey: meekCookieEncryptionPrivateKey,
MeekObfuscatedKey: meekObfuscatedKey,
MeekCertificateCommonName: "www.example.org",
MeekProhibitedHeaders: nil,
MeekProxyForwardedForHeaders: []string{"X-Forwarded-For"},
LoadMonitorPeriodSeconds: 300,
TrafficRulesFilename: params.TrafficRulesFilename,
}
encodedConfig, err := json.MarshalIndent(config, "\n", " ")
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
intPtr := func(i int) *int {
return &i
}
trafficRulesSet := &TrafficRulesSet{
DefaultRules: TrafficRules{
RateLimits: RateLimits{
ReadUnthrottledBytes: new(int64),
ReadBytesPerSecond: new(int64),
WriteUnthrottledBytes: new(int64),
WriteBytesPerSecond: new(int64),
},
IdleTCPPortForwardTimeoutMilliseconds: intPtr(DEFAULT_IDLE_TCP_PORT_FORWARD_TIMEOUT_MILLISECONDS),
IdleUDPPortForwardTimeoutMilliseconds: intPtr(DEFAULT_IDLE_UDP_PORT_FORWARD_TIMEOUT_MILLISECONDS),
MaxTCPPortForwardCount: intPtr(DEFAULT_MAX_TCP_PORT_FORWARD_COUNT),
MaxUDPPortForwardCount: intPtr(DEFAULT_MAX_UDP_PORT_FORWARD_COUNT),
AllowTCPPorts: nil,
AllowUDPPorts: nil,
},
}
encodedTrafficRulesSet, err := json.MarshalIndent(trafficRulesSet, "\n", " ")
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
capabilities := []string{}
if params.EnableSSHAPIRequests {
capabilities = append(capabilities, common.CAPABILITY_SSH_API_REQUESTS)
}
if params.WebServerPort != 0 {
capabilities = append(capabilities, common.CAPABILITY_UNTUNNELED_WEB_API_REQUESTS)
}
for protocol, _ := range params.TunnelProtocolPorts {
capabilities = append(capabilities, psiphon.GetCapability(protocol))
}
sshPort := params.TunnelProtocolPorts["SSH"]
obfuscatedSSHPort := params.TunnelProtocolPorts["OSSH"]
// Meek port limitations
// - fronted meek protocols are hard-wired in the client to be port 443 or 80.
// - only one other meek port may be specified.
meekPort := params.TunnelProtocolPorts["UNFRONTED-MEEK-OSSH"]
if meekPort == 0 {
meekPort = params.TunnelProtocolPorts["UNFRONTED-MEEK-HTTPS-OSSH"]
}
// Note: fronting params are a stub; this server entry will exercise
// client and server fronting code paths, but not actually traverse
// a fronting hop.
serverEntryWebServerPort := ""
strippedWebServerCertificate := ""
if params.WebServerPort != 0 {
serverEntryWebServerPort = fmt.Sprintf("%d", params.WebServerPort)
// Server entry format omits the BEGIN/END lines and newlines
lines := strings.Split(webServerCertificate, "\n")
strippedWebServerCertificate = strings.Join(lines[1:len(lines)-2], "")
}
serverEntry := &psiphon.ServerEntry{
IpAddress: params.ServerIPAddress,
WebServerPort: serverEntryWebServerPort,
WebServerSecret: webServerSecret,
WebServerCertificate: strippedWebServerCertificate,
SshPort: sshPort,
SshUsername: sshUserName,
SshPassword: sshPassword,
SshHostKey: base64.RawStdEncoding.EncodeToString(sshPublicKey.Marshal()),
SshObfuscatedPort: obfuscatedSSHPort,
SshObfuscatedKey: obfuscatedSSHKey,
Capabilities: capabilities,
Region: "US",
MeekServerPort: meekPort,
MeekCookieEncryptionPublicKey: meekCookieEncryptionPublicKey,
MeekObfuscatedKey: meekObfuscatedKey,
MeekFrontingHosts: []string{params.ServerIPAddress},
MeekFrontingAddresses: []string{params.ServerIPAddress},
MeekFrontingDisableSNI: false,
}
encodedServerEntry, err := psiphon.EncodeServerEntry(serverEntry)
if err != nil {
return nil, nil, nil, common.ContextError(err)
}
return encodedConfig, encodedTrafficRulesSet, []byte(encodedServerEntry), nil
}
func TestObfuscatedSSHConn(t *testing.T) {
keyword, _ := MakeRandomStringHex(32)
serverAddress := "127.0.0.1:2222"
listener, err := net.Listen("tcp", serverAddress)
if err != nil {
t.Fatalf("Listen failed: %s", err)
}
rsaKey, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
t.Fatalf("GenerateKey failed: %s", err)
}
hostKey, err := ssh.NewSignerFromKey(rsaKey)
if err != nil {
t.Fatalf("NewSignerFromKey failed: %s", err)
}
sshCertChecker := &ssh.CertChecker{
HostKeyFallback: func(addr string, remote net.Addr, publicKey ssh.PublicKey) error {
if !bytes.Equal(hostKey.PublicKey().Marshal(), publicKey.Marshal()) {
return errors.New("unexpected host public key")
}
return nil
},
}
result := make(chan error, 1)
go func() {
conn, err := listener.Accept()
if err == nil {
conn, err = NewObfuscatedSshConn(
OBFUSCATION_CONN_MODE_SERVER, conn, keyword)
}
if err == nil {
config := &ssh.ServerConfig{
NoClientAuth: true,
}
config.AddHostKey(hostKey)
_, _, _, err = ssh.NewServerConn(conn, config)
}
if err != nil {
select {
case result <- err:
default:
}
}
}()
go func() {
conn, err := net.DialTimeout("tcp", serverAddress, 5*time.Second)
if err == nil {
conn, err = NewObfuscatedSshConn(
OBFUSCATION_CONN_MODE_CLIENT, conn, keyword)
}
if err == nil {
config := &ssh.ClientConfig{
HostKeyCallback: sshCertChecker.CheckHostKey,
}
_, _, _, err = ssh.NewClientConn(conn, "", config)
}
// Sends nil on success
select {
case result <- err:
default:
}
}()
err = <-result
if err != nil {
t.Fatalf("obfuscated SSH handshake failed: %s", err)
}
}