feature: Add support for HTTP_PROXY, HTTPS_PROXY, and NO_PROXY

internal/api/proxy.go

@@ -1,11 +1,8 @@
 package api
 
 import (
-	"bufio"
 	"context"
 	"crypto/tls"
-	"encoding/base64"
-	"fmt"
 	"net"
 	"net/http"
 	"net/url"
@@ -15,22 +12,22 @@ import (
 //
 // Note: baseTransport is considered to be a clone created with transport.Clone()
 //
-// - If a the proxyPath is not empty, a unix socket proxy is created.
-// - Otherwise, the proxyURL is used to determine if we should proxy socks5 / http connections
+// - If proxyPath is not empty, a unix socket proxy is created.
+// - Otherwise, proxyURL is used to determine if we should proxy socks5 / http connections
 func withProxyTransport(baseTransport *http.Transport, proxyURL *url.URL, proxyPath string) *http.Transport {
 	handshakeTLS := func(ctx context.Context, conn net.Conn, addr string) (net.Conn, error) {
 		// Extract the hostname (without the port) for TLS SNI
 		host, _, err := net.SplitHostPort(addr)
 		if err != nil {
 			return nil, err
 		}
-		tlsConn := tls.Client(conn, &tls.Config{
-			ServerName: host,
-			// Pull InsecureSkipVerify from the target host transport
-			// so that insecure-skip-verify flag settings are honored for the proxy server
-			InsecureSkipVerify: baseTransport.TLSClientConfig.InsecureSkipVerify,
-		})
+		cfg := baseTransport.TLSClientConfig.Clone()
+		if cfg.ServerName == "" {
+			cfg.ServerName = host
+		}
+		tlsConn := tls.Client(conn, cfg)
 		if err := tlsConn.HandshakeContext(ctx); err != nil {
+			tlsConn.Close()
 			return nil, err
 		}
 		return tlsConn, nil
@@ -53,82 +50,7 @@ func withProxyTransport(baseTransport *http.Transport, proxyURL *url.URL, proxyP
 		// clear out any system proxy settings
 		baseTransport.Proxy = nil
 	} else if proxyURL != nil {
-		switch proxyURL.Scheme {
-		case "socks5", "socks5h":
-			// SOCKS proxies work out of the box - no need to manually dial
-			baseTransport.Proxy = http.ProxyURL(proxyURL)
-		case "http", "https":
-			dial := func(ctx context.Context, network, addr string) (net.Conn, error) {
-				// Dial the proxy
-				d := net.Dialer{}
-				conn, err := d.DialContext(ctx, "tcp", proxyURL.Host)
-				if err != nil {
-					return nil, err
-				}
-
-				// this is the whole point of manually dialing the HTTP(S) proxy:
-				// being able to force HTTP/1.
-				// When relying on Transport.Proxy, the protocol is always HTTP/2,
-				// but many proxy servers don't support HTTP/2.
-				// We don't want to disable HTTP/2 in general because we want to use it when
-				// connecting to the Sourcegraph API, using HTTP/1 for the proxy connection only.
-				protocol := "HTTP/1.1"
-
-				// CONNECT is the HTTP method used to set up a tunneling connection with a proxy
-				method := "CONNECT"
-
-				// Manually writing out the HTTP commands because it's not complicated,
-				// and http.Request has some janky behavior:
-				//   - ignores the Proto field and hard-codes the protocol to HTTP/1.1
-				//   - ignores the Host Header (Header.Set("Host", host)) and uses URL.Host instead.
-				//   - When the Host field is set, overrides the URL field
-				connectReq := fmt.Sprintf("%s %s %s\r\n", method, addr, protocol)
-
-				// A Host header is required per RFC 2616, section 14.23
-				connectReq += fmt.Sprintf("Host: %s\r\n", addr)
-
-				// use authentication if proxy credentials are present
-				if proxyURL.User != nil {
-					password, _ := proxyURL.User.Password()
-					auth := base64.StdEncoding.EncodeToString([]byte(proxyURL.User.Username() + ":" + password))
-					connectReq += fmt.Sprintf("Proxy-Authorization: Basic %s\r\n", auth)
-				}
-
-				// finish up with an extra carriage return + newline, as per RFC 7230, section 3
-				connectReq += "\r\n"
-
-				// Send the CONNECT request to the proxy to establish the tunnel
-				if _, err := conn.Write([]byte(connectReq)); err != nil {
-					conn.Close()
-					return nil, err
-				}
-
-				// Read and check the response from the proxy
-				resp, err := http.ReadResponse(bufio.NewReader(conn), nil)
-				if err != nil {
-					conn.Close()
-					return nil, err
-				}
-				if resp.StatusCode != http.StatusOK {
-					conn.Close()
-					return nil, fmt.Errorf("failed to connect to proxy %v: %v", proxyURL, resp.Status)
-				}
-				resp.Body.Close()
-				return conn, nil
-			}
-			dialTLS := func(ctx context.Context, network, addr string) (net.Conn, error) {
-				// Dial the underlying connection through the proxy
-				conn, err := dial(ctx, network, addr)
-				if err != nil {
-					return nil, err
-				}
-				return handshakeTLS(ctx, conn, addr)
-			}
-			baseTransport.DialContext = dial
-			baseTransport.DialTLSContext = dialTLS
-			// clear out any system proxy settings
-			baseTransport.Proxy = nil
-		}
+		baseTransport.Proxy = http.ProxyURL(proxyURL)
 	}
 
 	return baseTransport