Rework transports

transport/legacy.go

@@ -0,0 +1,82 @@
+package transport
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"math/rand"
+	"net"
+	"net/http"
+	"net/http/httputil"
+	"time"
+)
+
+const (
+	crlf               = "\r\n"
+	HttpOK = "HTTP/1.1 200 OK\r\n"
+)
+
+type LegacyPKT struct {
+	Conn net.Conn
+	ChunkedReader io.Reader
+	Writer *bufio.Writer
+}
+
+func NewLegacy(w http.ResponseWriter) (*LegacyPKT, error) {
+	hj, ok := w.(http.Hijacker)
+	if ok {
+		conn, rw, err := hj.Hijack()
+		l := &LegacyPKT{
+			Conn: conn,
+			ChunkedReader: httputil.NewChunkedReader(rw.Reader),
+			Writer: rw.Writer,
+		}
+		return l, err
+	}
+
+	return nil, errors.New("cannot hijack connection")
+}
+
+func (t *LegacyPKT) ReadPacket() (n int, p []byte, err error){
+	buf := make([]byte, 4096) // bufio.defaultBufSize
+	n, err = t.ChunkedReader.Read(buf)
+	p = make([]byte, n)
+	copy(p, buf)
+
+	return n, p, err
+}
+
+func (t *LegacyPKT) WritePacket(b []byte) (n int, err error) {
+	return t.Conn.Write(b)
+}
+
+func (t *LegacyPKT) Close() error {
+	return t.Conn.Close()
+}
+
+// [MS-TSGU]: Terminal Services Gateway Server Protocol version 39.0
+// The server sends back the final status code 200 OK, and also a random entity body of limited size (100 bytes).
+// This enables a reverse proxy to start allowing data from the RDG server to the RDG client. The RDG server does
+// not specify an entity length in its response. It uses HTTP 1.0 semantics to send the entity body and closes the
+// connection after the last byte is sent.
+func (t *LegacyPKT) SendAccept(doSeed bool) {
+	t.Writer.WriteString(HttpOK)
+	t.Writer.WriteString("Date: " + time.Now().Format(time.RFC1123) + crlf)
+	if !doSeed {
+		t.Writer.WriteString("Content-Length: 0" + crlf)
+	}
+	t.Writer.WriteString(crlf)
+
+	if doSeed {
+		seed := make([]byte, 10)
+		rand.Read(seed)
+		// docs say it's a seed but 2019 responds with ab cd * 5
+		t.Writer.Write(seed)
+	}
+	t.Writer.Flush()
+}
+
+func (t *LegacyPKT) Drain() {
+	p := make([]byte, 32767)
+	t.Conn.Read(p)
+}