feature/featuretags, all: add build features, use existing ones in more places

Saves 270 KB.

Updates #12614

Change-Id: I4c3fe06d32c49edb3a4bb0758a8617d83f291cf5
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

net/netns/socks.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build !ios && !js && !android
+//go:build !ios && !js && !android && !ts_omit_useproxy
 
 package netns
 

net/tlsdial/blockblame/blockblame.go

@@ -9,13 +9,19 @@ package blockblame
 import (
 	"crypto/x509"
 	"strings"
+	"sync"
+
+	"tailscale.com/feature/buildfeatures"
 )
 
 // VerifyCertificate checks if the given certificate c is issued by a firewall manufacturer
 // that is known to block Tailscale connections. It returns true and the Manufacturer of
 // the equipment if it is, or false and nil if it is not.
 func VerifyCertificate(c *x509.Certificate) (m *Manufacturer, ok bool) {
-	for _, m := range Manufacturers {
+	if !buildfeatures.HasDebug {
+		return nil, false
+	}
+	for _, m := range manufacturers() {
 		if m.match != nil && m.match(c) {
 			return m, true
 		}
@@ -33,46 +39,56 @@ type Manufacturer struct {
 	match matchFunc
 }
 
-var Manufacturers = []*Manufacturer{
-	{
-		Name:  "Aruba Networks",
-		match: issuerContains("Aruba"),
-	},
-	{
-		Name:  "Cisco",
-		match: issuerContains("Cisco"),
-	},
-	{
-		Name: "Fortinet",
-		match: matchAny(
-			issuerContains("Fortinet"),
-			certEmail("support@fortinet.com"),
-		),
-	},
-	{
-		Name:  "Huawei",
-		match: certEmail("mobile@huawei.com"),
-	},
-	{
-		Name: "Palo Alto Networks",
-		match: matchAny(
-			issuerContains("Palo Alto Networks"),
-			issuerContains("PAN-FW"),
-		),
-	},
-	{
-		Name:  "Sophos",
-		match: issuerContains("Sophos"),
-	},
-	{
-		Name: "Ubiquiti",
-		match: matchAny(
-			issuerContains("UniFi"),
-			issuerContains("Ubiquiti"),
-		),
-	},
+func manufacturers() []*Manufacturer {
+	manufacturersOnce.Do(func() {
+		manufacturersList = []*Manufacturer{
+			{
+				Name:  "Aruba Networks",
+				match: issuerContains("Aruba"),
+			},
+			{
+				Name:  "Cisco",
+				match: issuerContains("Cisco"),
+			},
+			{
+				Name: "Fortinet",
+				match: matchAny(
+					issuerContains("Fortinet"),
+					certEmail("support@fortinet.com"),
+				),
+			},
+			{
+				Name:  "Huawei",
+				match: certEmail("mobile@huawei.com"),
+			},
+			{
+				Name: "Palo Alto Networks",
+				match: matchAny(
+					issuerContains("Palo Alto Networks"),
+					issuerContains("PAN-FW"),
+				),
+			},
+			{
+				Name:  "Sophos",
+				match: issuerContains("Sophos"),
+			},
+			{
+				Name: "Ubiquiti",
+				match: matchAny(
+					issuerContains("UniFi"),
+					issuerContains("Ubiquiti"),
+				),
+			},
+		}
+	})
+	return manufacturersList
 }
 
+var (
+	manufacturersOnce sync.Once
+	manufacturersList []*Manufacturer
+)
+
 type matchFunc func(*x509.Certificate) bool
 
 func issuerContains(s string) matchFunc {

net/tlsdial/tlsdial.go

@@ -28,6 +28,7 @@ import (
 
 	"tailscale.com/derp/derpconst"
 	"tailscale.com/envknob"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/health"
 	"tailscale.com/hostinfo"
 	"tailscale.com/net/bakedroots"
@@ -36,12 +37,6 @@ import (
 
 var counterFallbackOK int32 // atomic
 
-// If SSLKEYLOGFILE is set, it's a file to which we write our TLS private keys
-// in a way that WireShark can read.
-//
-// See https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format
-var sslKeyLogFile = os.Getenv("SSLKEYLOGFILE")
-
 var debug = envknob.RegisterBool("TS_DEBUG_TLS_DIAL")
 
 // tlsdialWarningPrinted tracks whether we've printed a warning about a given
@@ -80,13 +75,19 @@ func Config(ht *health.Tracker, base *tls.Config) *tls.Config {
 	// the real TCP connection) because host is the ultimate hostname, but this
 	// tls.Config is used for both the proxy and the ultimate target.
 
-	if n := sslKeyLogFile; n != "" {
-		f, err := os.OpenFile(n, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
-		if err != nil {
-			log.Fatal(err)
+	if buildfeatures.HasDebug {
+		// If SSLKEYLOGFILE is set, it's a file to which we write our TLS private keys
+		// in a way that WireShark can read.
+		//
+		// See https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format
+		if n := os.Getenv("SSLKEYLOGFILE"); n != "" {
+			f, err := os.OpenFile(n, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
+			if err != nil {
+				log.Fatal(err)
+			}
+			log.Printf("WARNING: writing to SSLKEYLOGFILE %v", n)
+			conf.KeyLogWriter = f
 		}
-		log.Printf("WARNING: writing to SSLKEYLOGFILE %v", n)
-		conf.KeyLogWriter = f
 	}
 
 	if conf.InsecureSkipVerify {
@@ -164,10 +165,12 @@ func Config(ht *health.Tracker, base *tls.Config) *tls.Config {
 		if debug() {
 			log.Printf("tlsdial(sys %q): %v", dialedHost, errSys)
 		}
+		if !buildfeatures.HasBakedRoots || (errSys == nil && !debug()) {
+			return errSys
+		}
 
-		// Always verify with our baked-in Let's Encrypt certificate,
-		// so we can log an informational message. This is useful for
-		// detecting SSL MiTM.
+		// If we have baked-in LetsEncrypt roots and we either failed above, or
+		// debug logging is enabled, also verify with LetsEncrypt.
 		opts.Roots = bakedroots.Get()
 		_, bakedErr := cs.PeerCertificates[0].Verify(opts)
 		if debug() {
@@ -239,8 +242,8 @@ func SetConfigExpectedCert(c *tls.Config, certDNSName string) {
 		if debug() {
 			log.Printf("tlsdial(sys %q/%q): %v", c.ServerName, certDNSName, errSys)
 		}
-		if errSys == nil {
-			return nil
+		if !buildfeatures.HasBakedRoots || errSys == nil {
+			return errSys
 		}
 		opts.Roots = bakedroots.Get()
 		_, err := certs[0].Verify(opts)