Don't print nil connection errors

This is enabled with backend /* ... */ { proxy_version 1 }

README.md

@@ -1,6 +1,6 @@
 # [tlstunnel]
 
-[![builds.sr.ht status](https://builds.sr.ht/~emersion/tlstunnel/commits.svg)](https://builds.sr.ht/~emersion/tlstunnel/commits?)
+[![builds.sr.ht status](https://builds.sr.ht/~emersion/tlstunnel/commits/master.svg)](https://builds.sr.ht/~emersion/tlstunnel/commits/master?)
 
 A TLS reverse proxy.
 

cmd/tlstunnel/main.go

@@ -17,6 +17,8 @@ import (
 var (
 	configPath   = "config"
 	certDataPath = ""
+
+	debug = false
 )
 
 func newServer() (*tlstunnel.Server, error) {
@@ -26,6 +28,7 @@ func newServer() (*tlstunnel.Server, error) {
 	}
 
 	srv := tlstunnel.NewServer()
+	srv.Debug = debug
 
 	loggerCfg := zap.Config{
 		Level:             zap.NewAtomicLevelAt(zap.InfoLevel),
@@ -68,6 +71,7 @@ func bumpOpenedFileLimit() error {
 
 func main() {
 	flag.StringVar(&configPath, "config", configPath, "path to configuration file")
+	flag.BoolVar(&debug, "debug", false, "enable debug logging")
 	flag.Parse()
 
 	if err := bumpOpenedFileLimit(); err != nil {

directives.go

@@ -1,12 +1,17 @@
 package tlstunnel
 
 import (
+	"crypto/sha256"
+	"crypto/subtle"
 	"crypto/tls"
+	"crypto/x509"
+	"encoding/hex"
 	"fmt"
 	"net"
 	"net/url"
 	"os"
 	"os/exec"
+	"strconv"
 	"strings"
 
 	"git.sr.ht/~emersion/go-scfg"
@@ -130,6 +135,64 @@ func parseBackend(backend *Backend, d *scfg.Directive) error {
 		return fmt.Errorf("failed to setup backend %q: unsupported URI scheme", backendURI)
 	}
 
+	for _, child := range d.Children {
+		switch child.Name {
+		case "tls_certfp":
+			if backend.TLSConfig == nil {
+				return fmt.Errorf("tls_certfp requires a tls:// backend address")
+			}
+
+			var algo, wantCertFP string
+			if err := child.ParseParams(&algo, &wantCertFP); err != nil {
+				return err
+			}
+			if algo != "sha-256" {
+				return fmt.Errorf("directive tls_certfp: only sha-256 is supported")
+			}
+
+			wantCertFP = strings.ReplaceAll(wantCertFP, ":", "")
+			wantSum, err := hex.DecodeString(wantCertFP)
+			if err != nil {
+				return fmt.Errorf("directive tls_certfp: invalid fingerprint: %v", err)
+			} else if len(wantSum) != sha256.Size {
+				return fmt.Errorf("directive tls_certfp: invalid fingerprint length")
+			}
+
+			backend.TLSConfig.InsecureSkipVerify = true
+			backend.TLSConfig.VerifyPeerCertificate = func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
+				if len(rawCerts) == 0 {
+					return fmt.Errorf("the server didn't present any TLS certificate")
+				}
+
+				for _, rawCert := range rawCerts {
+					sum := sha256.Sum256(rawCert)
+					if subtle.ConstantTimeCompare(sum[:], wantSum) == 1 {
+						return nil // fingerprints match
+					}
+				}
+
+				sum := sha256.Sum256(rawCerts[0])
+				remoteCertFP := hex.EncodeToString(sum[:])
+				return fmt.Errorf("configured TLS certificate fingerprint doesn't match the server's - %s", remoteCertFP)
+			}
+		case "proxy_version":
+			var version string
+			if err := child.ParseParams(&version); err != nil {
+				return err
+			}
+			v, err := strconv.Atoi(version)
+			if err != nil {
+				return fmt.Errorf("directive proxy_version: invalid version: %v", err)
+			}
+			switch v {
+			case 1, 2:
+				backend.ProxyVersion = v
+			default:
+				return fmt.Errorf("directive proxy_version: unknown version: %v", v)
+			}
+		}
+	}
+
 	return nil
 }
 
@@ -175,6 +238,19 @@ func parseTLS(srv *Server, d *scfg.Directive) error {
 			if err := parseTLSOnDemand(srv, child); err != nil {
 				return err
 			}
+		case "acme_dns_command":
+			var cmdName string
+			if err := child.ParseParams(&cmdName); err != nil {
+				return err
+			}
+			cmdParams := child.Params[1:]
+
+			srv.ACMEIssuer.DNS01Solver = &certmagic.DNS01Solver{
+				DNSProvider: &commandDNSProvider{
+					Name:   cmdName,
+					Params: cmdParams,
+				},
+			}
 		default:
 			return fmt.Errorf("unknown %q directive", child.Name)
 		}

dns.go

@@ -0,0 +1,81 @@
+package tlstunnel
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+
+	"github.com/caddyserver/certmagic"
+	"github.com/libdns/libdns"
+)
+
+type commandDNSProvider struct {
+	Name   string
+	Params []string
+}
+
+var _ certmagic.ACMEDNSProvider = (*commandDNSProvider)(nil)
+
+func (provider *commandDNSProvider) exec(ctx context.Context, subcmd string, subargs ...string) error {
+	var params []string
+	params = append(params, provider.Params...)
+	params = append(params, subcmd)
+	params = append(params, subargs...)
+	cmd := exec.CommandContext(ctx, provider.Name, params...)
+
+	if out, err := cmd.CombinedOutput(); err != nil {
+		details := ""
+		if len(out) > 0 {
+			details = ": " + string(out)
+		}
+		return fmt.Errorf("failed to run DNS hook %v (%w)%v", subcmd, err, details)
+	}
+
+	return nil
+}
+
+func (provider *commandDNSProvider) processRecords(ctx context.Context, zone string, recs []libdns.Record, subcmd string) ([]libdns.Record, error) {
+	var (
+		done []libdns.Record
+		err  error
+	)
+	for _, rec := range recs {
+		var domain string
+		if domain, err = domainFromACMEChallengeRecord(zone, &rec); err != nil {
+			break
+		}
+		if err = provider.exec(ctx, subcmd, domain, "-", rec.Value); err != nil {
+			break
+		}
+		done = append(done, rec)
+	}
+	return done, err
+}
+
+func (provider *commandDNSProvider) AppendRecords(ctx context.Context, zone string, recs []libdns.Record) ([]libdns.Record, error) {
+	return provider.processRecords(ctx, zone, recs, "deploy_challenge")
+}
+
+func (provider *commandDNSProvider) DeleteRecords(ctx context.Context, zone string, recs []libdns.Record) ([]libdns.Record, error) {
+	return provider.processRecords(ctx, zone, recs, "clean_challenge")
+}
+
+func domainFromACMEChallengeRecord(zone string, rec *libdns.Record) (string, error) {
+	relZone := strings.TrimSuffix(zone, ".")
+
+	var domain string
+	if rec.Name == "_acme-challenge" {
+		// Root domain
+		domain = relZone
+	} else if strings.HasPrefix(rec.Name, "_acme-challenge.") {
+		// Subdomain
+		relName := strings.TrimPrefix(rec.Name, "_acme-challenge.")
+		domain = relName + "." + relZone
+	}
+	if rec.Type != "TXT" || domain == "" {
+		return "", fmt.Errorf("DNS record doesn't look like an ACME challenge: %v %v", rec.Type, rec.Name)
+	}
+
+	return domain, nil
+}

go.mod

@@ -6,6 +6,7 @@ require (
 	git.sr.ht/~emersion/go-scfg v0.0.0-20211215104734-c2c7a15d6c99
 	github.com/caddyserver/certmagic v0.17.2
 	github.com/klauspost/cpuid/v2 v2.2.1 // indirect
+	github.com/libdns/libdns v0.2.1
 	github.com/pires/go-proxyproto v0.6.2
 	github.com/pkg/errors v0.9.1 // indirect
 	go.uber.org/atomic v1.10.0 // indirect

server.go

@@ -38,6 +38,7 @@ func newACMECache() *acmeCache {
 type Server struct {
 	Listeners map[string]*Listener // indexed by listening address
 	Frontends []*Frontend
+	Debug     bool
 
 	ManagedNames   []string
 	UnmanagedCerts []tls.Certificate
@@ -186,6 +187,10 @@ func (srv *Server) Replace(old *Server) error {
 	return nil
 }
 
+type clientError struct {
+	error
+}
+
 type listenerHandles struct {
 	Server    *Server
 	Frontends map[string]*Frontend // indexed by server name
@@ -256,8 +261,14 @@ func (ln *Listener) serve() error {
 		}
 
 		go func() {
-			if err := ln.handle(conn); err != nil {
-				log.Printf("listener %q: %v", ln.Address, err)
+			err := ln.handle(conn)
+			if err == nil {
+				return
+			}
+			srv := ln.atomic.Load().(*listenerHandles).Server
+			var clientErr clientError
+			if !errors.As(err, &clientErr) || srv.Debug {
+				log.Printf("listener %q: connection %q: %v", ln.Address, conn.RemoteAddr(), err)
 			}
 		}()
 	}
@@ -298,7 +309,7 @@ func (ln *Listener) handle(conn net.Conn) error {
 	if err := tlsConn.Handshake(); err == io.EOF {
 		return nil
 	} else if err != nil {
-		return fmt.Errorf("TLS handshake failed: %v", err)
+		return clientError{fmt.Errorf("TLS handshake failed: %v", err)}
 	}
 	if err := tlsConn.SetDeadline(time.Time{}); err != nil {
 		return fmt.Errorf("failed to reset TLS handshake timeout: %v", err)
@@ -358,7 +369,7 @@ func (fe *Frontend) handle(downstream net.Conn, tlsState *tls.ConnectionState) e
 	defer upstream.Close()
 
 	if be.Proxy {
-		h := proxyproto.HeaderProxyFromAddrs(2, downstream.RemoteAddr(), downstream.LocalAddr())
+		h := proxyproto.HeaderProxyFromAddrs(byte(be.ProxyVersion), downstream.RemoteAddr(), downstream.LocalAddr())
 
 		var tlvs []proxyproto.TLV
 		if tlsState.ServerName != "" {
@@ -382,16 +393,17 @@ func (fe *Frontend) handle(downstream net.Conn, tlsState *tls.ConnectionState) e
 	}
 
 	if err := duplexCopy(upstream, downstream); err != nil {
-		return fmt.Errorf("failed to copy bytes: %v", err)
+		return clientError{fmt.Errorf("failed to copy bytes: %v", err)}
 	}
 	return nil
 }
 
 type Backend struct {
-	Network   string
-	Address   string
-	Proxy     bool
-	TLSConfig *tls.Config // nil if no TLS
+	Network      string
+	Address      string
+	Proxy        bool
+	ProxyVersion int
+	TLSConfig    *tls.Config // nil if no TLS
 }
 
 func duplexCopy(a, b io.ReadWriter) error {

tlstunnel.1.scd

@@ -52,7 +52,7 @@ The following directives are supported:
 	*listen* <address>...
 		Additional addresses to listen on.
 
-	*backend* <uri>...
+	*backend* <uri> { ... }
 		Backend to forward incoming connections to.
 
 		The following URIs are supported:
@@ -64,6 +64,25 @@ The following directives are supported:
 		The _+proxy_ suffix can be added to the URI scheme to forward
 		connection metadata via the PROXY protocol.
 
+		The backend directive supports the following sub-directives:
+
+		*tls_certfp* sha-256 <fingerprint>
+			Instead of using CAs to check the TLS certificate provided by the
+			backend, check that the certificate matches the provided
+			fingerprint. This can be used to connect to servers with a
+			self-signed certificate, for instance.
+
+			The fingerprint of a certificate can be obtained via *openssl*(1):
+
+			```
+			openssl x509 -fingerprint -sha256 -noout <certificate>
+			```
+
+		*proxy_version* <version>
+			PROXY protocol version to use, if _+proxy_ is specified.
+			The supported versions are 1 and 2.
+			If not specified, the PROXY version used defaults to version 2.
+
 	*tls* { ... }
 		Customise frontend-specific TLS configuration.
 
@@ -123,6 +142,13 @@ The following directives are supported:
 			The environment will contain a *TLSTUNNEL_NAME* variable with the
 			domain name to be validated.
 
+	*acme_dns_command* command [arguments...]
+		Configure the ACME DNS challenge using the specified command.
+
+		The command must implement _deploy_challenge_ and _clean_challenge_
+		as specified by dehydrated's hooks:
+		https://github.com/dehydrated-io/dehydrated
+
 # FILES
 
 _/etc/tlstunnel/config_