From 000e99e7f3f5c18741ee3412ba113c32c6ce3aa7 Mon Sep 17 00:00:00 2001 From: Viktor Liu <17948409+lixmal@users.noreply.github.com> Date: Mon, 13 Oct 2025 17:50:16 +0200 Subject: [PATCH] [client] Force TLS1.2 for RDP with Win11/Server2025 for CredSSP compatibility (#4617) --- client/wasm/internal/rdp/cert_validation.go | 15 ++- client/wasm/internal/rdp/rdcleanpath.go | 93 ++++++++++++-- .../wasm/internal/rdp/rdcleanpath_handlers.go | 119 +++++++++--------- 3 files changed, 152 insertions(+), 75 deletions(-) diff --git a/client/wasm/internal/rdp/cert_validation.go b/client/wasm/internal/rdp/cert_validation.go index 4a23a4bc8..1678c3996 100644 --- a/client/wasm/internal/rdp/cert_validation.go +++ b/client/wasm/internal/rdp/cert_validation.go @@ -73,8 +73,8 @@ func (p *RDCleanPathProxy) validateCertificateWithJS(conn *proxyConnection, cert } } -func (p *RDCleanPathProxy) getTLSConfigWithValidation(conn *proxyConnection) *tls.Config { - return &tls.Config{ +func (p *RDCleanPathProxy) getTLSConfigWithValidation(conn *proxyConnection, requiresCredSSP bool) *tls.Config { + config := &tls.Config{ InsecureSkipVerify: true, // We'll validate manually after handshake VerifyConnection: func(cs tls.ConnectionState) error { var certChain [][]byte @@ -93,4 +93,15 @@ func (p *RDCleanPathProxy) getTLSConfigWithValidation(conn *proxyConnection) *tl return nil }, } + + // CredSSP (NLA) requires TLS 1.2 - it's incompatible with TLS 1.3 + if requiresCredSSP { + config.MinVersion = tls.VersionTLS12 + config.MaxVersion = tls.VersionTLS12 + } else { + config.MinVersion = tls.VersionTLS12 + config.MaxVersion = tls.VersionTLS13 + } + + return config } diff --git a/client/wasm/internal/rdp/rdcleanpath.go b/client/wasm/internal/rdp/rdcleanpath.go index 8062a05cc..16bf63bb9 100644 --- a/client/wasm/internal/rdp/rdcleanpath.go +++ b/client/wasm/internal/rdp/rdcleanpath.go @@ -6,11 +6,13 @@ import ( "context" "crypto/tls" "encoding/asn1" + "errors" "fmt" "io" "net" "sync" "syscall/js" + "time" log "github.com/sirupsen/logrus" ) @@ -19,18 +21,34 @@ const ( RDCleanPathVersion = 3390 RDCleanPathProxyHost = "rdcleanpath.proxy.local" RDCleanPathProxyScheme = "ws" + + rdpDialTimeout = 15 * time.Second + + GeneralErrorCode = 1 + WSAETimedOut = 10060 + WSAEConnRefused = 10061 + WSAEConnAborted = 10053 + WSAEConnReset = 10054 + WSAEGenericError = 10050 ) type RDCleanPathPDU struct { - Version int64 `asn1:"tag:0,explicit"` - Error []byte `asn1:"tag:1,explicit,optional"` - Destination string `asn1:"utf8,tag:2,explicit,optional"` - ProxyAuth string `asn1:"utf8,tag:3,explicit,optional"` - ServerAuth string `asn1:"utf8,tag:4,explicit,optional"` - PreconnectionBlob string `asn1:"utf8,tag:5,explicit,optional"` - X224ConnectionPDU []byte `asn1:"tag:6,explicit,optional"` - ServerCertChain [][]byte `asn1:"tag:7,explicit,optional"` - ServerAddr string `asn1:"utf8,tag:9,explicit,optional"` + Version int64 `asn1:"tag:0,explicit"` + Error RDCleanPathErr `asn1:"tag:1,explicit,optional"` + Destination string `asn1:"utf8,tag:2,explicit,optional"` + ProxyAuth string `asn1:"utf8,tag:3,explicit,optional"` + ServerAuth string `asn1:"utf8,tag:4,explicit,optional"` + PreconnectionBlob string `asn1:"utf8,tag:5,explicit,optional"` + X224ConnectionPDU []byte `asn1:"tag:6,explicit,optional"` + ServerCertChain [][]byte `asn1:"tag:7,explicit,optional"` + ServerAddr string `asn1:"utf8,tag:9,explicit,optional"` +} + +type RDCleanPathErr struct { + ErrorCode int16 `asn1:"tag:0,explicit"` + HTTPStatusCode int16 `asn1:"tag:1,explicit,optional"` + WSALastError int16 `asn1:"tag:2,explicit,optional"` + TLSAlertCode int8 `asn1:"tag:3,explicit,optional"` } type RDCleanPathProxy struct { @@ -210,9 +228,13 @@ func (p *RDCleanPathProxy) handleDirectRDP(conn *proxyConnection, firstPacket [] destination := conn.destination log.Infof("Direct RDP mode: Connecting to %s via NetBird", destination) - rdpConn, err := p.nbClient.Dial(conn.ctx, "tcp", destination) + ctx, cancel := context.WithTimeout(conn.ctx, rdpDialTimeout) + defer cancel() + + rdpConn, err := p.nbClient.Dial(ctx, "tcp", destination) if err != nil { log.Errorf("Failed to connect to %s: %v", destination, err) + p.sendRDCleanPathError(conn, newWSAError(err)) return } conn.rdpConn = rdpConn @@ -220,6 +242,7 @@ func (p *RDCleanPathProxy) handleDirectRDP(conn *proxyConnection, firstPacket [] _, err = rdpConn.Write(firstPacket) if err != nil { log.Errorf("Failed to write first packet: %v", err) + p.sendRDCleanPathError(conn, newWSAError(err)) return } @@ -227,6 +250,7 @@ func (p *RDCleanPathProxy) handleDirectRDP(conn *proxyConnection, firstPacket [] n, err := rdpConn.Read(response) if err != nil { log.Errorf("Failed to read X.224 response: %v", err) + p.sendRDCleanPathError(conn, newWSAError(err)) return } @@ -269,3 +293,52 @@ func (p *RDCleanPathProxy) sendToWebSocket(conn *proxyConnection, data []byte) { conn.wsHandlers.Call("send", uint8Array.Get("buffer")) } } + +func (p *RDCleanPathProxy) sendRDCleanPathError(conn *proxyConnection, pdu RDCleanPathPDU) { + data, err := asn1.Marshal(pdu) + if err != nil { + log.Errorf("Failed to marshal error PDU: %v", err) + return + } + p.sendToWebSocket(conn, data) +} + +func errorToWSACode(err error) int16 { + if err == nil { + return WSAEGenericError + } + var netErr *net.OpError + if errors.As(err, &netErr) && netErr.Timeout() { + return WSAETimedOut + } + if errors.Is(err, context.DeadlineExceeded) { + return WSAETimedOut + } + if errors.Is(err, context.Canceled) { + return WSAEConnAborted + } + if errors.Is(err, io.EOF) { + return WSAEConnReset + } + return WSAEGenericError +} + +func newWSAError(err error) RDCleanPathPDU { + return RDCleanPathPDU{ + Version: RDCleanPathVersion, + Error: RDCleanPathErr{ + ErrorCode: GeneralErrorCode, + WSALastError: errorToWSACode(err), + }, + } +} + +func newHTTPError(statusCode int16) RDCleanPathPDU { + return RDCleanPathPDU{ + Version: RDCleanPathVersion, + Error: RDCleanPathErr{ + ErrorCode: GeneralErrorCode, + HTTPStatusCode: statusCode, + }, + } +} diff --git a/client/wasm/internal/rdp/rdcleanpath_handlers.go b/client/wasm/internal/rdp/rdcleanpath_handlers.go index 010efa5ea..97bb46338 100644 --- a/client/wasm/internal/rdp/rdcleanpath_handlers.go +++ b/client/wasm/internal/rdp/rdcleanpath_handlers.go @@ -3,6 +3,7 @@ package rdp import ( + "context" "crypto/tls" "encoding/asn1" "io" @@ -11,11 +12,17 @@ import ( log "github.com/sirupsen/logrus" ) +const ( + // MS-RDPBCGR: confusingly named, actually means PROTOCOL_HYBRID (CredSSP) + protocolSSL = 0x00000001 + protocolHybridEx = 0x00000008 +) + func (p *RDCleanPathProxy) processRDCleanPathPDU(conn *proxyConnection, pdu RDCleanPathPDU) { log.Infof("Processing RDCleanPath PDU: Version=%d, Destination=%s", pdu.Version, pdu.Destination) if pdu.Version != RDCleanPathVersion { - p.sendRDCleanPathError(conn, "Unsupported version") + p.sendRDCleanPathError(conn, newHTTPError(400)) return } @@ -24,10 +31,13 @@ func (p *RDCleanPathProxy) processRDCleanPathPDU(conn *proxyConnection, pdu RDCl destination = pdu.Destination } - rdpConn, err := p.nbClient.Dial(conn.ctx, "tcp", destination) + ctx, cancel := context.WithTimeout(conn.ctx, rdpDialTimeout) + defer cancel() + + rdpConn, err := p.nbClient.Dial(ctx, "tcp", destination) if err != nil { log.Errorf("Failed to connect to %s: %v", destination, err) - p.sendRDCleanPathError(conn, "Connection failed") + p.sendRDCleanPathError(conn, newWSAError(err)) p.cleanupConnection(conn) return } @@ -40,6 +50,34 @@ func (p *RDCleanPathProxy) processRDCleanPathPDU(conn *proxyConnection, pdu RDCl p.setupTLSConnection(conn, pdu) } +// detectCredSSPFromX224 checks if the X.224 response indicates NLA/CredSSP is required. +// Per MS-RDPBCGR spec: byte 11 = TYPE_RDP_NEG_RSP (0x02), bytes 15-18 = selectedProtocol flags. +// Returns (requiresTLS12, selectedProtocol, detectionSuccessful). +func (p *RDCleanPathProxy) detectCredSSPFromX224(x224Response []byte) (bool, uint32, bool) { + const minResponseLength = 19 + + if len(x224Response) < minResponseLength { + return false, 0, false + } + + // Per X.224 specification: + // x224Response[0] == 0x03: Length of X.224 header (3 bytes) + // x224Response[5] == 0xD0: X.224 Data TPDU code + if x224Response[0] != 0x03 || x224Response[5] != 0xD0 { + return false, 0, false + } + + if x224Response[11] == 0x02 { + flags := uint32(x224Response[15]) | uint32(x224Response[16])<<8 | + uint32(x224Response[17])<<16 | uint32(x224Response[18])<<24 + + hasNLA := (flags & (protocolSSL | protocolHybridEx)) != 0 + return hasNLA, flags, true + } + + return false, 0, false +} + func (p *RDCleanPathProxy) setupTLSConnection(conn *proxyConnection, pdu RDCleanPathPDU) { var x224Response []byte if len(pdu.X224ConnectionPDU) > 0 { @@ -47,7 +85,7 @@ func (p *RDCleanPathProxy) setupTLSConnection(conn *proxyConnection, pdu RDClean _, err := conn.rdpConn.Write(pdu.X224ConnectionPDU) if err != nil { log.Errorf("Failed to write X.224 PDU: %v", err) - p.sendRDCleanPathError(conn, "Failed to forward X.224") + p.sendRDCleanPathError(conn, newWSAError(err)) return } @@ -55,21 +93,32 @@ func (p *RDCleanPathProxy) setupTLSConnection(conn *proxyConnection, pdu RDClean n, err := conn.rdpConn.Read(response) if err != nil { log.Errorf("Failed to read X.224 response: %v", err) - p.sendRDCleanPathError(conn, "Failed to read X.224 response") + p.sendRDCleanPathError(conn, newWSAError(err)) return } x224Response = response[:n] log.Debugf("Received X.224 Connection Confirm (%d bytes)", n) } - tlsConfig := p.getTLSConfigWithValidation(conn) + requiresCredSSP, selectedProtocol, detected := p.detectCredSSPFromX224(x224Response) + if detected { + if requiresCredSSP { + log.Warnf("Detected NLA/CredSSP (selectedProtocol: 0x%08X), forcing TLS 1.2 for compatibility", selectedProtocol) + } else { + log.Warnf("No NLA/CredSSP detected (selectedProtocol: 0x%08X), allowing up to TLS 1.3", selectedProtocol) + } + } else { + log.Warnf("Could not detect RDP security protocol, allowing up to TLS 1.3") + } + + tlsConfig := p.getTLSConfigWithValidation(conn, requiresCredSSP) tlsConn := tls.Client(conn.rdpConn, tlsConfig) conn.tlsConn = tlsConn if err := tlsConn.Handshake(); err != nil { log.Errorf("TLS handshake failed: %v", err) - p.sendRDCleanPathError(conn, "TLS handshake failed") + p.sendRDCleanPathError(conn, newWSAError(err)) return } @@ -106,47 +155,6 @@ func (p *RDCleanPathProxy) setupTLSConnection(conn *proxyConnection, pdu RDClean p.cleanupConnection(conn) } -func (p *RDCleanPathProxy) setupPlainConnection(conn *proxyConnection, pdu RDCleanPathPDU) { - if len(pdu.X224ConnectionPDU) > 0 { - log.Debugf("Forwarding X.224 Connection Request (%d bytes)", len(pdu.X224ConnectionPDU)) - _, err := conn.rdpConn.Write(pdu.X224ConnectionPDU) - if err != nil { - log.Errorf("Failed to write X.224 PDU: %v", err) - p.sendRDCleanPathError(conn, "Failed to forward X.224") - return - } - - response := make([]byte, 1024) - n, err := conn.rdpConn.Read(response) - if err != nil { - log.Errorf("Failed to read X.224 response: %v", err) - p.sendRDCleanPathError(conn, "Failed to read X.224 response") - return - } - - responsePDU := RDCleanPathPDU{ - Version: RDCleanPathVersion, - X224ConnectionPDU: response[:n], - ServerAddr: conn.destination, - } - - p.sendRDCleanPathPDU(conn, responsePDU) - } else { - responsePDU := RDCleanPathPDU{ - Version: RDCleanPathVersion, - ServerAddr: conn.destination, - } - p.sendRDCleanPathPDU(conn, responsePDU) - } - - go p.forwardConnToWS(conn, conn.rdpConn, "TCP") - go p.forwardWSToConn(conn, conn.rdpConn, "TCP") - - <-conn.ctx.Done() - log.Debug("TCP connection context done, cleaning up") - p.cleanupConnection(conn) -} - func (p *RDCleanPathProxy) sendRDCleanPathPDU(conn *proxyConnection, pdu RDCleanPathPDU) { data, err := asn1.Marshal(pdu) if err != nil { @@ -158,21 +166,6 @@ func (p *RDCleanPathProxy) sendRDCleanPathPDU(conn *proxyConnection, pdu RDClean p.sendToWebSocket(conn, data) } -func (p *RDCleanPathProxy) sendRDCleanPathError(conn *proxyConnection, errorMsg string) { - pdu := RDCleanPathPDU{ - Version: RDCleanPathVersion, - Error: []byte(errorMsg), - } - - data, err := asn1.Marshal(pdu) - if err != nil { - log.Errorf("Failed to marshal error PDU: %v", err) - return - } - - p.sendToWebSocket(conn, data) -} - func (p *RDCleanPathProxy) readWebSocketMessage(conn *proxyConnection) ([]byte, error) { msgChan := make(chan []byte) errChan := make(chan error)