Implement client TLS termination

Managed to reuse the same proxy function the server uses.

boringproxy.go

@@ -2,13 +2,11 @@ package main
 
 import (
 	"bufio"
-	"bytes"
 	"crypto/tls"
 	"flag"
 	"fmt"
 	"github.com/caddyserver/certmagic"
 	"io"
-	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
@@ -122,7 +120,16 @@ func Listen() {
 				webUiHandler.handleWebUiRequest(w, r)
 			}
 		} else {
-			p.proxyRequest(w, r)
+
+			tunnel, exists := db.GetTunnel(r.Host)
+			if !exists {
+				errMessage := fmt.Sprintf("No tunnel attached to %s", r.Host)
+				w.WriteHeader(500)
+				io.WriteString(w, errMessage)
+				return
+			}
+
+			proxyRequest(w, r, tunnel, httpClient, tunnel.TunnelPort)
 		}
 	})
 
@@ -163,7 +170,7 @@ func (p *BoringProxy) handleConnection(clientConn net.Conn) {
 
 	tunnel, exists := p.db.GetTunnel(clientHello.ServerName)
 
-	if exists && tunnel.TlsPassthrough {
+	if exists && (tunnel.TlsTermination == "client" || tunnel.TlsTermination == "passthrough") {
 		p.passthroughRequest(passConn, tunnel)
 	} else {
 		p.httpListener.PassConn(passConn)
@@ -198,78 +205,6 @@ func (p *BoringProxy) passthroughRequest(conn net.Conn, tunnel Tunnel) {
 	wg.Wait()
 }
 
-func (p *BoringProxy) proxyRequest(w http.ResponseWriter, r *http.Request) {
-
-	tunnel, exists := p.db.GetTunnel(r.Host)
-	if !exists {
-		errMessage := fmt.Sprintf("No tunnel attached to %s", r.Host)
-		w.WriteHeader(500)
-		io.WriteString(w, errMessage)
-		return
-	}
-
-	if tunnel.AuthUsername != "" || tunnel.AuthPassword != "" {
-		username, password, ok := r.BasicAuth()
-		if !ok {
-			w.Header()["WWW-Authenticate"] = []string{"Basic"}
-			w.WriteHeader(401)
-			return
-		}
-
-		if username != tunnel.AuthUsername || password != tunnel.AuthPassword {
-			w.Header()["WWW-Authenticate"] = []string{"Basic"}
-			w.WriteHeader(401)
-			// TODO: should probably use a better form of rate limiting
-			time.Sleep(2 * time.Second)
-			return
-		}
-	}
-
-	downstreamReqHeaders := r.Header.Clone()
-
-	upstreamAddr := fmt.Sprintf("localhost:%d", tunnel.TunnelPort)
-	upstreamUrl := fmt.Sprintf("http://%s%s", upstreamAddr, r.URL.RequestURI())
-
-	body, err := ioutil.ReadAll(r.Body)
-	if err != nil {
-		errMessage := fmt.Sprintf("%s", err)
-		w.WriteHeader(500)
-		io.WriteString(w, errMessage)
-		return
-	}
-
-	upstreamReq, err := http.NewRequest(r.Method, upstreamUrl, bytes.NewReader(body))
-	if err != nil {
-		errMessage := fmt.Sprintf("%s", err)
-		w.WriteHeader(500)
-		io.WriteString(w, errMessage)
-		return
-	}
-
-	upstreamReq.Header = downstreamReqHeaders
-
-	upstreamReq.Header["X-Forwarded-Host"] = []string{r.Host}
-	upstreamReq.Host = fmt.Sprintf("%s:%d", tunnel.ClientAddress, tunnel.ClientPort)
-
-	upstreamRes, err := p.httpClient.Do(upstreamReq)
-	if err != nil {
-		errMessage := fmt.Sprintf("%s", err)
-		w.WriteHeader(502)
-		io.WriteString(w, errMessage)
-		return
-	}
-	defer upstreamRes.Body.Close()
-
-	downstreamResHeaders := w.Header()
-
-	for k, v := range upstreamRes.Header {
-		downstreamResHeaders[k] = v
-	}
-
-	w.WriteHeader(upstreamRes.StatusCode)
-	io.Copy(w, upstreamRes.Body)
-}
-
 func redirectTLS(w http.ResponseWriter, r *http.Request) {
 	url := fmt.Sprintf("https://%s:443%s", r.Host, r.RequestURI)
 	http.Redirect(w, r, url, http.StatusMovedPermanently)

client.go

@@ -7,6 +7,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"github.com/caddyserver/certmagic"
 	"golang.org/x/crypto/ssh"
 	"io"
 	"io/ioutil"
@@ -29,6 +30,7 @@ type BoringProxyClient struct {
 	user             string
 	cancelFuncs      map[string]context.CancelFunc
 	cancelFuncsMutex *sync.Mutex
+	certConfig       *certmagic.Config
 }
 
 func NewBoringProxyClient() *BoringProxyClient {
@@ -39,6 +41,9 @@ func NewBoringProxyClient() *BoringProxyClient {
 	user := flagSet.String("user", "admin", "user")
 	flagSet.Parse(os.Args[2:])
 
+	certmagic.DefaultACME.DisableHTTPChallenge = true
+	certConfig := certmagic.NewDefault()
+
 	httpClient := &http.Client{}
 	tunnels := make(map[string]Tunnel)
 	cancelFuncs := make(map[string]context.CancelFunc)
@@ -54,6 +59,7 @@ func NewBoringProxyClient() *BoringProxyClient {
 		user:             *user,
 		cancelFuncs:      cancelFuncs,
 		cancelFuncsMutex: cancelFuncsMutex,
+		certConfig:       certConfig,
 	}
 }
 
@@ -218,6 +224,33 @@ func (c *BoringProxyClient) BoreTunnel(tunnel Tunnel) context.CancelFunc {
 		}
 		//defer listener.Close()
 
+		if tunnel.TlsTermination == "client" {
+			// TODO: There's still quite a bit of duplication with what the server does. Could we
+			// encapsulate it into a type?
+			err = c.certConfig.ManageSync([]string{tunnel.Domain})
+			if err != nil {
+				log.Println("CertMagic error at startup")
+				log.Println(err)
+			}
+
+			tlsConfig := &tls.Config{
+				GetCertificate: c.certConfig.GetCertificate,
+				NextProtos:     []string{"h2", "acme-tls/1"},
+			}
+			tlsListener := tls.NewListener(listener, tlsConfig)
+
+			http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+				proxyRequest(w, r, tunnel, c.httpClient, tunnel.ClientPort)
+			})
+
+			// TODO: It seems inefficient to make a separate HTTP server for each TLS-passthrough tunnel,
+			// but the code is much simpler. The only alternative I've thought of so far involves storing
+			// all the tunnels in a mutexed map and retrieving them from a single HTTP server, same as the
+			// boringproxy server does.
+			go http.Serve(tlsListener, nil)
+
+		} else {
+
 			go func() {
 				for {
 					conn, err := listener.Accept()
@@ -233,6 +266,7 @@ func (c *BoringProxyClient) BoreTunnel(tunnel Tunnel) context.CancelFunc {
 					go c.handleConnection(conn, tunnel.ClientAddress, tunnel.ClientPort)
 				}
 			}()
+		}
 
 		<-ctx.Done()
 		listener.Close()

database.go

@@ -50,7 +50,7 @@ type Tunnel struct {
 	AuthUsername     string `json:"auth_username"`
 	AuthPassword     string `json:"auth_password"`
 	CssId            string `json:"css_id"`
-	TlsPassthrough   bool   `json:"tls_passthrough"`
+	TlsTermination   string `json:"tls_termination"`
 }
 
 func NewDatabase() (*Database, error) {

http_proxy.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"time"
+)
+
+func proxyRequest(w http.ResponseWriter, r *http.Request, tunnel Tunnel, httpClient *http.Client, port int) {
+
+	if tunnel.AuthUsername != "" || tunnel.AuthPassword != "" {
+		username, password, ok := r.BasicAuth()
+		if !ok {
+			w.Header()["WWW-Authenticate"] = []string{"Basic"}
+			w.WriteHeader(401)
+			return
+		}
+
+		if username != tunnel.AuthUsername || password != tunnel.AuthPassword {
+			w.Header()["WWW-Authenticate"] = []string{"Basic"}
+			w.WriteHeader(401)
+			// TODO: should probably use a better form of rate limiting
+			time.Sleep(2 * time.Second)
+			return
+		}
+	}
+
+	downstreamReqHeaders := r.Header.Clone()
+
+	upstreamAddr := fmt.Sprintf("localhost:%d", port)
+	upstreamUrl := fmt.Sprintf("http://%s%s", upstreamAddr, r.URL.RequestURI())
+
+	body, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		errMessage := fmt.Sprintf("%s", err)
+		w.WriteHeader(500)
+		io.WriteString(w, errMessage)
+		return
+	}
+
+	upstreamReq, err := http.NewRequest(r.Method, upstreamUrl, bytes.NewReader(body))
+	if err != nil {
+		errMessage := fmt.Sprintf("%s", err)
+		w.WriteHeader(500)
+		io.WriteString(w, errMessage)
+		return
+	}
+
+	upstreamReq.Header = downstreamReqHeaders
+
+	upstreamReq.Header["X-Forwarded-Host"] = []string{r.Host}
+	upstreamReq.Host = fmt.Sprintf("%s:%d", tunnel.ClientAddress, tunnel.ClientPort)
+
+	upstreamRes, err := httpClient.Do(upstreamReq)
+	if err != nil {
+		errMessage := fmt.Sprintf("%s", err)
+		w.WriteHeader(502)
+		io.WriteString(w, errMessage)
+		return
+	}
+	defer upstreamRes.Body.Close()
+
+	downstreamResHeaders := w.Header()
+
+	for k, v := range upstreamRes.Header {
+		downstreamResHeaders[k] = v
+	}
+
+	w.WriteHeader(upstreamRes.StatusCode)
+	io.Copy(w, upstreamRes.Body)
+}

sni.go

@@ -1,5 +1,4 @@
-// NOTE: The code in this file was mostly copied from this very helpful
-// article:
+// NOTE: A lot of this code was copied from this very helpful article:
 // https://www.agwa.name/blog/post/writing_an_sni_proxy_in_go
 
 package main
@@ -92,7 +91,8 @@ func (c ProxyConn) CloseWrite() error           { return c.conn.(*net.TCPConn).C
 func (c ProxyConn) Read(p []byte) (int, error)  { return c.reader.Read(p) }
 func (c ProxyConn) Write(p []byte) (int, error) { return c.conn.Write(p) }
 
-// TODO: is this safe? Will it actually close properly?
+// TODO: is this safe? Will it actually close properly, or does it need to be
+// connected to the reader somehow?
 func (c ProxyConn) Close() error                       { return c.conn.Close() }
 func (c ProxyConn) LocalAddr() net.Addr                { return c.conn.LocalAddr() }
 func (c ProxyConn) RemoteAddr() net.Addr               { return c.conn.RemoteAddr() }