feature: letsencrypt http.Handler

config/config.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"time"
 
+	"golang.org/x/crypto/acme/autocert"
 	"gopkg.in/yaml.v2"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -252,6 +253,14 @@ type Config struct {
 	// TLS Config
 	KubernetesEnableTLS bool `yaml:"kubernetes-enable-tls"`
 
+	// Letsencrypt
+	EnableLetsencrypt       bool      `yaml:"enable-letsencrypt"`
+	LetsencryptCache        string    `yaml:"letsencrypt-cache"`
+	LetsencryptEmail        string    `yaml:"letsencrypt-email"`
+	LetsencryptDomains      *listFlag `yaml:"letsencrypt-domains"`
+	LetsencryptDirectoryURL string    `yaml:"letsencrypt-directory-url"`
+	LetsencryptUserAgent    string    `yaml:"letsencrypt-user-agent"`
+
 	// API Monitoring
 	ApiUsageMonitoringEnable                       bool   `yaml:"enable-api-usage-monitoring"`
 	ApiUsageMonitoringRealmKeys                    string `yaml:"api-usage-monitoring-realm-keys"`
@@ -359,6 +368,7 @@ func NewConfig() *Config {
 	cfg.LuaModules = commaListFlag()
 	cfg.LuaSources = commaListFlag()
 	cfg.Oauth2GrantTokeninfoKeys = commaListFlag()
+	cfg.LetsencryptDomains = commaListFlag()
 
 	flag := flag.NewFlagSet("", flag.ExitOnError)
 	flag.StringVar(&cfg.ConfigFile, "config-file", "", "if provided the flags will be loaded/overwritten by the values on the file (yaml)")
@@ -585,6 +595,14 @@ func NewConfig() *Config {
 	// Exclude insecure cipher suites
 	flag.BoolVar(&cfg.ExcludeInsecureCipherSuites, "exclude-insecure-cipher-suites", false, "excludes insecure cipher suites")
 
+	// Letsencrypt
+	flag.BoolVar(&cfg.EnableLetsencrypt, "enable-letsencrypt", false, "enables letsencrypt autocert handling on the proxy")
+	flag.StringVar(&cfg.LetsencryptCache, "letsencrypt-cache", "", "Configure the autocert cert cache <inmemory|remote|directory>")
+	flag.StringVar(&cfg.LetsencryptEmail, "letsencrypt-email", "", "Sets letsencrypt email address such that you can be reached by letsencrypt if something goes wrong")
+	flag.Var(cfg.LetsencryptDomains, "letsencrypt-domains", "An allow list of domains for autocert handling")
+	flag.StringVar(&cfg.LetsencryptDirectoryURL, "letsencrypt-directory-url", "", "Sets directory URL for testing")
+	flag.StringVar(&cfg.LetsencryptUserAgent, "letsencrypt-user-agent", "", "Sets httpclient useragent that calls letsencrypt that enables letsencrypt to limit you if something goes wrong")
+
 	// API Monitoring:
 	flag.BoolVar(&cfg.ApiUsageMonitoringEnable, "enable-api-usage-monitoring", false, "enables the apiUsageMonitoring filter")
 	flag.StringVar(&cfg.ApiUsageMonitoringRealmKeys, "api-usage-monitoring-realm-keys", "", "name of the property in the JWT payload that contains the authority realm")
@@ -1138,9 +1156,35 @@ func (c *Config) ToOptions() skipper.Options {
 		})
 	}
 
+	if c.EnableLetsencrypt {
+		wrappers = append(wrappers, func(handler http.Handler) http.Handler {
+			return net.NewLetsencrypt(
+				c.getLetsencryptCache(),
+				c.LetsencryptEmail,
+				c.LetsencryptDirectoryURL,
+				c.LetsencryptUserAgent,
+				c.LetsencryptDomains.values,
+			).Handler(handler)
+		})
+
+	}
+
 	return options
 }
 
+func (c *Config) getLetsencryptCache() autocert.Cache {
+	switch c.LetsencryptCache {
+	case "directory":
+		return autocert.DirCache(os.TempDir())
+	case "remote":
+		return &net.RemoteCache{
+			Client: &net.RedisRingClient{},
+		}
+	default:
+		return &net.InmemoryCache{}
+	}
+}
+
 func (c *Config) getMinTLSVersion() uint16 {
 	tlsVersionTable := map[string]uint16{
 		"1.3": tls.VersionTLS13,

config/config_test.go

@@ -166,6 +166,7 @@ func defaultConfig(with func(*Config)) *Config {
 		ClusterRatelimitMaxGroupShards:          1,
 		ValidateQuery:                           true,
 		ValidateQueryLog:                        true,
+		LetsencryptDomains:                      commaListFlag(),
 		LuaModules:                              commaListFlag(),
 		LuaSources:                              commaListFlag(),
 		OpenPolicyAgentCleanerInterval:          openpolicyagent.DefaultCleanIdlePeriod,

net/letsencrypt.go

@@ -0,0 +1,137 @@
+package net
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"net"
+	"net/http"
+	"regexp"
+	"strings"
+	"sync"
+
+	"golang.org/x/crypto/acme"
+	"golang.org/x/crypto/acme/autocert"
+)
+
+type InmemoryCache struct {
+	m sync.Map
+}
+
+func (ic *InmemoryCache) Get(ctx context.Context, key string) ([]byte, error) {
+	if dat, ok := ic.m.Load(key); !ok {
+		return nil, fmt.Errorf("missing key %q", key)
+	} else {
+		if data, ok := dat.([]byte); !ok {
+			return nil, fmt.Errorf("failed to convert %q to []byte", dat)
+		} else {
+			return data, nil
+		}
+	}
+}
+
+func (ic *InmemoryCache) Put(ctx context.Context, key string, data []byte) error {
+	ic.m.Store(key, data)
+	return nil
+}
+
+func (ic *InmemoryCache) Delete(ctx context.Context, key string) error {
+	ic.m.Delete(key)
+	return nil
+}
+
+type RemoteCache struct {
+	Client *RedisRingClient
+}
+
+func (rc *RemoteCache) Get(ctx context.Context, key string) ([]byte, error) {
+	res, err := rc.Client.Get(ctx, key)
+	if err != nil {
+		return nil, err
+	}
+	return []byte(res), nil
+}
+
+func (rc *RemoteCache) Delete(ctx context.Context, key string) error {
+	return rc.Client.Del(ctx, key)
+}
+
+func (rc *RemoteCache) Put(ctx context.Context, key string, val []byte) error {
+	_, err := rc.Client.Set(ctx, key, val, 0)
+	return err
+}
+
+func (rc *RemoteCache) Close() {
+	rc.Client.Close()
+}
+
+type Letsencrypt struct {
+	manager *autocert.Manager
+}
+
+// NewLetsencrypt creates a letsencrypt handler to automatically handle CSR challenges.
+//
+// The cache argument can be either
+//
+//   - autocert.DirCache for a filesystem cache
+//   - inmemoryCache for in memory cache
+//   - remoteCache for redis based production cache to be shared between multiple skipper processes
+func NewLetsencrypt(cache autocert.Cache, email, directoryURL, userAgent string, proposedDomains []string) *Letsencrypt {
+	domains := make([]string, 0, len(proposedDomains))
+	for _, s := range proposedDomains {
+		if validateDomain(s) {
+			domains = append(domains, s)
+		}
+	}
+
+	manager := &autocert.Manager{
+		Cache:      cache,
+		Email:      email,
+		HostPolicy: autocert.HostWhitelist(domains...),
+		Prompt:     autocert.AcceptTOS,
+		Client: &acme.Client{
+			DirectoryURL: directoryURL,
+			UserAgent:    userAgent,
+			HTTPClient:   http.DefaultClient,
+		},
+	}
+
+	return &Letsencrypt{
+		manager: manager,
+	}
+}
+
+func (le *Letsencrypt) Handler(fallback http.Handler) http.Handler {
+	return le.manager.HTTPHandler(fallback)
+}
+
+func (le *Letsencrypt) TLSConfig() *tls.Config {
+	return le.manager.TLSConfig()
+}
+
+// Listener returns a net.Listener that need to be closed on exit or
+// you leak a goroutine
+func (le *Letsencrypt) Listener() net.Listener {
+	return le.manager.Listener()
+}
+
+func (le *Letsencrypt) Client() *acme.Client {
+	return le.manager.Client
+}
+
+func (le *Letsencrypt) Close() {
+	le.Listener().Close()
+}
+
+var domainRegex = regexp.MustCompile("^[a-z0-9]+$")
+
+func validateDomain(s string) bool {
+	i := 0
+	for w := range strings.SplitSeq(s, ".") {
+		if !domainRegex.MatchString(w) {
+			return false
+		}
+		i++
+	}
+	return i > 1
+}

net/letsencrypt_test.go

@@ -0,0 +1,116 @@
+package net
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"github.com/zalando/skipper/net/redistest"
+)
+
+func TestRemoteCache(t *testing.T) {
+	t.Logf("create redis..")
+	redisAddr, done := redistest.NewTestRedis(t)
+	defer done()
+	if redisAddr == "" {
+		t.Fatal("Failed to create redis 1")
+	}
+
+	redisAddr2, done2 := redistest.NewTestRedis(t)
+	defer done2()
+	if redisAddr2 == "" {
+		t.Fatal("Failed to create redis 2")
+	}
+
+	rc := RemoteCache{
+		Client: NewRedisRingClient(&RedisOptions{
+			Addrs: []string{redisAddr, redisAddr2},
+		}),
+	}
+	defer rc.Close()
+
+	if err := rc.Put(context.Background(), "foo", []byte("bar")); err != nil {
+		t.Fatalf("Failed to put: %v", err)
+	}
+
+	if v, err := rc.Get(context.Background(), "foo"); err != nil {
+		t.Fatalf("Failed to get: %v", err)
+	} else {
+		t.Logf("%T %v %s", v, v, v)
+		if string(v) != "bar" {
+			t.Fatalf("Failed to get result, got: %q", string(v))
+		}
+	}
+
+	if err := rc.Delete(context.Background(), "foo"); err != nil {
+		t.Fatalf("Failed to delete: %v", err)
+	}
+}
+
+func TestInmemoryCache(t *testing.T) {
+	rc := &InmemoryCache{}
+
+	if _, err := rc.Get(context.Background(), "foo"); err == nil {
+		t.Fatal(`Failed can not get "foo" on empty cache`)
+	}
+
+	if err := rc.Put(context.Background(), "foo", []byte("bar")); err != nil {
+		t.Fatalf("Failed to put: %v", err)
+	}
+
+	if v, err := rc.Get(context.Background(), "foo"); err != nil {
+		t.Fatalf("Failed to get: %v", err)
+	} else {
+		t.Logf("%T %v %s", v, v, v)
+	}
+
+	if err := rc.Delete(context.Background(), "foo"); err != nil {
+		t.Fatalf("Failed to delete: %v", err)
+	}
+
+	if err := rc.Put(context.Background(), "foo2", []byte("ü")); err != nil {
+		t.Fatalf("Failed to put: %v", err)
+	}
+
+	if v, err := rc.Get(context.Background(), "foo2"); err != nil {
+		t.Fatalf("Failed to get: %v", err)
+	} else {
+		t.Logf("%T %v %s", v, v, v)
+	}
+
+}
+
+func TestLetsencrypt(t *testing.T) {
+	invalidDomain := "s_.example.org"
+	if validateDomain(invalidDomain) {
+		t.Fatalf("Failed to validate invalid domain %q", invalidDomain)
+	}
+	validDomain := "example.org"
+	if !validateDomain(validDomain) {
+		t.Fatalf("Failed to validate valid domain %q", validDomain)
+	}
+
+	le := NewLetsencrypt(&InmemoryCache{}, "skipper@example.org", "https://acme-staging-v02.api.letsencrypt.org/directory", "skipper-test TestLetsencrypt", []string{validDomain})
+	defer le.Close()
+	if le.manager.Client != nil {
+		dir, err := le.manager.Client.Discover(context.TODO())
+		if err != nil {
+			t.Fatalf("Failed to discover: %v", err)
+		}
+		t.Logf("order: %s", dir.OrderURL)
+
+		defer func() {
+			if le.manager.Client.HTTPClient != nil {
+				le.manager.Client.HTTPClient.CloseIdleConnections()
+			}
+		}()
+	}
+
+	require.NotNil(t, le.Client(), "client should not be nil")
+	require.NotNil(t, le.TLSConfig(), "TLSConfig should not be nil")
+	require.NotNil(t, le.Handler(nil), "http.Handler should not be nil")
+
+	li := le.Listener()
+	defer li.Close()
+	t.Logf("listener %v", li.Addr())
+}

net/redisclient.go

@@ -391,6 +391,11 @@ func (r *RedisRingClient) SetAddrs(ctx context.Context, addrs []string) {
 	r.ring.SetAddrs(createAddressMap(addrs))
 }
 
+func (r *RedisRingClient) Del(ctx context.Context, key string) error {
+	res := r.ring.Del(ctx, key)
+	return res.Err()
+}
+
 func (r *RedisRingClient) Get(ctx context.Context, key string) (string, error) {
 	res := r.ring.Get(ctx, key)
 	return res.Val(), res.Err()