Add tailscale_enable_funnel_to_localhost_plaintext_http1 to tailscale.h

tailscale.c

@@ -23,6 +23,7 @@ extern int TsnetGetIps(int sd, char *buf, size_t buflen);
 extern int TsnetGetRemoteAddr(int listener, int conn, char *buf, size_t buflen);
 extern int TsnetListen(int sd, char* net, char* addr, int* listenerOut);
 extern int TsnetLoopback(int sd, char* addrOut, size_t addrLen, char* proxyOut, char* localOut);
+extern int TsnetEnableFunnelToLocalhostPlaintextHttp1(int sd, int localhostPort);
 
 tailscale tailscale_new() {
 	return TsnetNewServer();
@@ -106,3 +107,7 @@ int tailscale_loopback(tailscale sd, char* addr_out, size_t addrlen, char* proxy
 int tailscale_errmsg(tailscale sd, char* buf, size_t buflen) {
 	return TsnetErrmsg(sd, buf, buflen);
 }
+
+int tailscale_enable_funnel_to_localhost_plaintext_http1(tailscale sd, int localhostPort) {
+	return TsnetEnableFunnelToLocalhostPlaintextHttp1(sd, localhostPort);
+}

tailscale.go

@@ -14,12 +14,14 @@ import (
 	"net"
 	"os"
 	"regexp"
+	"strconv"
 	"strings"
 	"sync"
 	"syscall"
 	"unsafe"
 
 	"tailscale.com/hostinfo"
+	"tailscale.com/ipn"
 	"tailscale.com/tsnet"
 	"tailscale.com/types/logger"
 )
@@ -531,3 +533,44 @@ func TsnetLoopback(sd C.int, addrOut *C.char, addrLen C.size_t, proxyOut *C.char
 
 	return 0
 }
+
+//export TsnetEnableFunnelToLocalhostPlaintextHttp1
+func TsnetEnableFunnelToLocalhostPlaintextHttp1(sd C.int, localhostPort C.int) C.int {
+	s, err := getServer(sd)
+	if err != nil {
+		return s.recErr(err)
+	}
+
+	ctx := context.Background()
+	lc, err := s.s.LocalClient()
+	if err != nil {
+		return s.recErr(err)
+	}
+
+	st, err := lc.StatusWithoutPeers(ctx)
+	if err != nil {
+		return s.recErr(err)
+	}
+	domain := st.CertDomains[0]
+
+	hp := ipn.HostPort(net.JoinHostPort(domain, strconv.Itoa(443)))
+	tcpForward := fmt.Sprintf("127.0.0.1:%d", localhostPort)
+	sc := &ipn.ServeConfig{
+		TCP: map[uint16]*ipn.TCPPortHandler{
+			443: {
+				TCPForward:   tcpForward,
+				TerminateTLS: domain,
+			},
+		},
+		AllowFunnel: map[ipn.HostPort]bool{
+			hp: true,
+		},
+	}
+
+	lc.SetServeConfig(ctx, sc)
+	if !sc.AllowFunnel[hp] {
+		return s.recErr(fmt.Errorf("libtailscale: failed to enable funnel"))
+	}
+
+	return 0
+}

tailscale.h

@@ -175,6 +175,22 @@ extern int tailscale_accept(tailscale_listener listener, tailscale_conn* conn_ou
 // Returns zero on success or -1 on error, call tailscale_errmsg for details.
 extern int tailscale_loopback(tailscale sd, char* addr_out, size_t addrlen, char* proxy_cred_out, char* local_api_cred_out);
 
+// tailscale_enable_funnel_to_localhost_plaintext_http1 configures sd to have
+// Tailscale Funnel enabled, routing requests from the public web
+// (without any authentication) down to this Tailscale node, requesting new 
+// LetsEncrypt TLS certs as needed, terminating TLS, and proxying all incoming
+// HTTPS requests to http://127.0.0.1:localhostPort without TLS. 
+//
+// There should be a plaintext HTTP/1 server listening on 127.0.0.1:localhostPort
+// or tsnet will serve HTTP 502 errors.
+//
+// Expect junk traffic from the internet from bots watching the public CT logs.
+//
+// Returns:
+// 	0     - success
+// 	-1    - other error, details printed to the tsnet logger
+extern int tailscale_enable_funnel_to_localhost_plaintext_http1(tailscale sd, int localhostPort);
+
 // tailscale_errmsg writes the details of the last error to buf.
 // 
 // After returning, buf is always NUL-terminated.