Revert "Clean up HTTP proxy (#123)" (#124)

This reverts commit 4d4d3f6.

x/examples/http2transport/main.go

@@ -45,7 +45,7 @@ func main() {
 	defer listener.Close()
 	log.Printf("Proxy listening on %v", listener.Addr().String())
 
-	server := http.Server{Handler: httpproxy.NewProxyHandler(dialer)}
+	server := http.Server{Handler: httpproxy.NewConnectHandler(dialer)}
 	go func() {
 		if err := server.Serve(listener); err != nil && err != http.ErrServerClosed {
 			log.Fatalf("Error running web server: %v", err)

x/httpproxy/connect_handler.go

@@ -15,26 +15,68 @@
 package httpproxy
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"net"
 	"net/http"
+	"strings"
 
 	"github.com/Jigsaw-Code/outline-sdk/transport"
 )
 
-type connectHandler struct {
+type handler struct {
 	dialer transport.StreamDialer
+	client http.Client
 }
 
-var _ http.Handler = (*connectHandler)(nil)
+var _ http.Handler = (*handler)(nil)
 
-func (h *connectHandler) ServeHTTP(proxyResp http.ResponseWriter, proxyReq *http.Request) {
-	if proxyReq.Method != http.MethodConnect {
-		proxyResp.Header().Add("Allow", "CONNECT")
-		http.Error(proxyResp, fmt.Sprintf("Method %v is not supported", proxyReq.Method), http.StatusMethodNotAllowed)
+// ServeHTTP implements [http.Handler].ServeHTTP for CONNECT requests, using the internal [transport.StreamDialer].
+func (h *handler) ServeHTTP(proxyResp http.ResponseWriter, proxyReq *http.Request) {
+	// TODO(fortuna): For public services (not local), we need authentication and drain on failures to avoid fingerprinting.
+	if proxyReq.Method == http.MethodConnect {
+		h.handleConnect(proxyResp, proxyReq)
 		return
 	}
+	if proxyReq.URL.Host != "" {
+		h.handleHTTPProxyRequest(proxyResp, proxyReq)
+		return
+	}
+	http.Error(proxyResp, "Not Found", http.StatusNotFound)
+}
+
+func (h *handler) handleHTTPProxyRequest(proxyResp http.ResponseWriter, proxyReq *http.Request) {
+	// We create a new request that uses a relative path + Host header, instead of the absolute URL in the proxy request.
+	targetReq, err := http.NewRequestWithContext(proxyReq.Context(), proxyReq.Method, proxyReq.URL.String(), proxyReq.Body)
+	if err != nil {
+		http.Error(proxyResp, "Error creating target request", http.StatusInternalServerError)
+		return
+	}
+	for key, values := range proxyReq.Header {
+		for _, value := range values {
+			targetReq.Header.Add(key, value)
+		}
+	}
+	targetResp, err := h.client.Do(targetReq)
+	if err != nil {
+		http.Error(proxyResp, "Failed to fetch destination", http.StatusServiceUnavailable)
+		return
+	}
+	defer targetResp.Body.Close()
+	for key, values := range targetResp.Header {
+		for _, value := range values {
+			proxyResp.Header().Add(key, value)
+		}
+	}
+	_, err = io.Copy(proxyResp, targetResp.Body)
+	if err != nil {
+		http.Error(proxyResp, "Failed write response", http.StatusServiceUnavailable)
+		return
+	}
+}
+
+func (h *handler) handleConnect(proxyResp http.ResponseWriter, proxyReq *http.Request) {
 	// Validate the target address.
 	_, portStr, err := net.SplitHostPort(proxyReq.Host)
 	if err != nil {
@@ -86,5 +128,11 @@ func (h *connectHandler) ServeHTTP(proxyResp http.ResponseWriter, proxyReq *http
 // The resulting handler is currently vulnerable to probing attacks. It's ok as a localhost proxy
 // but it may be vulnerable if used as a public proxy.
 func NewConnectHandler(dialer transport.StreamDialer) http.Handler {
-	return &connectHandler{dialer}
+	dialContext := func(ctx context.Context, network, addr string) (net.Conn, error) {
+		if !strings.HasPrefix(network, "tcp") {
+			return nil, fmt.Errorf("protocol not supported: %v", network)
+		}
+		return dialer.Dial(ctx, addr)
+	}
+	return &handler{dialer, http.Client{Transport: &http.Transport{DialContext: dialContext}}}
 }

x/mobileproxy/mobileproxy.go

@@ -77,7 +77,7 @@ func RunProxy(localAddress string, transportConfig string) (*Proxy, error) {
 		return nil, fmt.Errorf("could not listen on address %v: %v", localAddress, err)
 	}
 
-	server := &http.Server{Handler: httpproxy.NewProxyHandler(dialer)}
+	server := &http.Server{Handler: httpproxy.NewConnectHandler(dialer)}
 	go server.Serve(listener)
 
 	host, portStr, err := net.SplitHostPort(listener.Addr().String())