Merge pull request #2015 from mholt/cert-cache

tls: Restructure and improve certificate management

caddy.go

@@ -77,8 +77,18 @@ var (
 	mu sync.Mutex
 )
 
+func init() {
+	OnProcessExit = append(OnProcessExit, func() {
+		if PidFile != "" {
+			os.Remove(PidFile)
+		}
+	})
+}
+
 // Instance contains the state of servers created as a result of
 // calling Start and can be used to access or control those servers.
+// It is literally an instance of a server type. Instance values
+// should NOT be copied. Use *Instance for safety.
 type Instance struct {
 	// serverType is the name of the instance's server type
 	serverType string
@@ -89,10 +99,11 @@ type Instance struct {
 	// wg is used to wait for all servers to shut down
 	wg *sync.WaitGroup
 
-	// context is the context created for this instance.
+	// context is the context created for this instance,
+	// used to coordinate the setting up of the server type
 	context Context
 
-	// servers is the list of servers with their listeners.
+	// servers is the list of servers with their listeners
 	servers []ServerListener
 
 	// these callbacks execute when certain events occur
@@ -101,6 +112,18 @@ type Instance struct {
 	onRestart       []func() error // before restart commences
 	onShutdown      []func() error // stopping, even as part of a restart
 	onFinalShutdown []func() error // stopping, not as part of a restart
+
+	// storing values on an instance is preferable to
+	// global state because these will get garbage-
+	// collected after in-process reloads when the
+	// old instances are destroyed; use StorageMu
+	// to access this value safely
+	Storage   map[interface{}]interface{}
+	StorageMu sync.RWMutex
+}
+
+func Instances() []*Instance {
+	return instances
 }
 
 // Servers returns the ServerListeners in i.
@@ -196,7 +219,7 @@ func (i *Instance) Restart(newCaddyfile Input) (*Instance, error) {
 	}
 
 	// create new instance; if the restart fails, it is simply discarded
-	newInst := &Instance{serverType: newCaddyfile.ServerType(), wg: i.wg}
+	newInst := &Instance{serverType: newCaddyfile.ServerType(), wg: i.wg, Storage: make(map[interface{}]interface{})}
 
 	// attempt to start new instance
 	err := startWithListenerFds(newCaddyfile, newInst, restartFds)
@@ -455,7 +478,7 @@ func (i *Instance) Caddyfile() Input {
 //
 // This function blocks until all the servers are listening.
 func Start(cdyfile Input) (*Instance, error) {
-	inst := &Instance{serverType: cdyfile.ServerType(), wg: new(sync.WaitGroup)}
+	inst := &Instance{serverType: cdyfile.ServerType(), wg: new(sync.WaitGroup), Storage: make(map[interface{}]interface{})}
 	err := startWithListenerFds(cdyfile, inst, nil)
 	if err != nil {
 		return inst, err
@@ -468,11 +491,34 @@ func Start(cdyfile Input) (*Instance, error) {
 }
 
 func startWithListenerFds(cdyfile Input, inst *Instance, restartFds map[string]restartTriple) error {
+	// save this instance in the list now so that
+	// plugins can access it if need be, for example
+	// the caddytls package, so it can perform cert
+	// renewals while starting up; we just have to
+	// remove the instance from the list later if
+	// it fails
+	instancesMu.Lock()
+	instances = append(instances, inst)
+	instancesMu.Unlock()
+	var err error
+	defer func() {
+		if err != nil {
+			instancesMu.Lock()
+			for i, otherInst := range instances {
+				if otherInst == inst {
+					instances = append(instances[:i], instances[i+1:]...)
+					break
+				}
+			}
+			instancesMu.Unlock()
+		}
+	}()
+
 	if cdyfile == nil {
 		cdyfile = CaddyfileInput{}
 	}
 
-	err := ValidateAndExecuteDirectives(cdyfile, inst, false)
+	err = ValidateAndExecuteDirectives(cdyfile, inst, false)
 	if err != nil {
 		return err
 	}
@@ -504,10 +550,6 @@ func startWithListenerFds(cdyfile Input, inst *Instance, restartFds map[string]r
 		return err
 	}
 
-	instancesMu.Lock()
-	instances = append(instances, inst)
-	instancesMu.Unlock()
-
 	// run any AfterStartup callbacks if this is not
 	// part of a restart; then show file descriptor notice
 	if restartFds == nil {
@@ -546,7 +588,7 @@ func startWithListenerFds(cdyfile Input, inst *Instance, restartFds map[string]r
 func ValidateAndExecuteDirectives(cdyfile Input, inst *Instance, justValidate bool) error {
 	// If parsing only inst will be nil, create an instance for this function call only.
 	if justValidate {
-		inst = &Instance{serverType: cdyfile.ServerType(), wg: new(sync.WaitGroup)}
+		inst = &Instance{serverType: cdyfile.ServerType(), wg: new(sync.WaitGroup), Storage: make(map[interface{}]interface{})}
 	}
 
 	stypeName := cdyfile.ServerType()
@@ -563,14 +605,14 @@ func ValidateAndExecuteDirectives(cdyfile Input, inst *Instance, justValidate bo
 		return err
 	}
 
-	inst.context = stype.NewContext()
+	inst.context = stype.NewContext(inst)
 	if inst.context == nil {
 		return fmt.Errorf("server type %s produced a nil Context", stypeName)
 	}
 
 	sblocks, err = inst.context.InspectServerBlocks(cdyfile.Path(), sblocks)
 	if err != nil {
-		return err
+		return fmt.Errorf("error inspecting server blocks: %v", err)
 	}
 
 	return executeDirectives(inst, cdyfile.Path(), stype.Directives(), sblocks, justValidate)

caddyhttp/httpserver/https.go

@@ -27,7 +27,7 @@ func activateHTTPS(cctx caddy.Context) error {
 	operatorPresent := !caddy.Started()
 
 	if !caddy.Quiet && operatorPresent {
-		fmt.Print("Activating privacy features...")
+		fmt.Print("Activating privacy features... ")
 	}
 
 	ctx := cctx.(*httpContext)
@@ -69,7 +69,7 @@ func activateHTTPS(cctx caddy.Context) error {
 	}
 
 	if !caddy.Quiet && operatorPresent {
-		fmt.Println(" done.")
+		fmt.Println("done.")
 	}
 
 	return nil
@@ -160,23 +160,37 @@ func hostHasOtherPort(allConfigs []*SiteConfig, thisConfigIdx int, otherPort str
 // to listen on HTTPPort. The TLS field of cfg must not be nil.
 func redirPlaintextHost(cfg *SiteConfig) *SiteConfig {
 	redirPort := cfg.Addr.Port
-	if redirPort == DefaultHTTPSPort {
-		redirPort = "" // default port is redundant
+	if redirPort == HTTPSPort {
+		// By default, HTTPSPort should be DefaultHTTPSPort,
+		// which of course doesn't need to be explicitly stated
+		// in the Location header. Even if HTTPSPort is changed
+		// so that it is no longer DefaultHTTPSPort, we shouldn't
+		// append it to the URL in the Location because changing
+		// the HTTPS port is assumed to be an internal-only change
+		// (in other words, we assume port forwarding is going on);
+		// but redirects go back to a presumably-external client.
+		// (If redirect clients are also internal, that is more
+		// advanced, and the user should configure HTTP->HTTPS
+		// redirects themselves.)
+		redirPort = ""
 	}
+
 	redirMiddleware := func(next Handler) Handler {
 		return HandlerFunc(func(w http.ResponseWriter, r *http.Request) (int, error) {
-			// Construct the URL to which to redirect. Note that the Host in a request might
-			// contain a port, but we just need the hostname; we'll set the port if needed.
+			// Construct the URL to which to redirect. Note that the Host in a
+			// request might contain a port, but we just need the hostname from
+			// it; and we'll set the port if needed.
 			toURL := "https://"
 			requestHost, _, err := net.SplitHostPort(r.Host)
 			if err != nil {
-				requestHost = r.Host // Host did not contain a port; great
+				requestHost = r.Host // Host did not contain a port, so use the whole value
 			}
 			if redirPort == "" {
 				toURL += requestHost
 			} else {
 				toURL += net.JoinHostPort(requestHost, redirPort)
 			}
+
 			toURL += r.URL.RequestURI()
 
 			w.Header().Set("Connection", "close")
@@ -184,9 +198,11 @@ func redirPlaintextHost(cfg *SiteConfig) *SiteConfig {
 			return 0, nil
 		})
 	}
+
 	host := cfg.Addr.Host
 	port := HTTPPort
 	addr := net.JoinHostPort(host, port)
+
 	return &SiteConfig{
 		Addr:       Address{Original: addr, Host: host, Port: port},
 		ListenHost: cfg.ListenHost,

caddyhttp/httpserver/https_test.go

@@ -53,7 +53,7 @@ func TestRedirPlaintextHost(t *testing.T) {
 		},
 		{
 			Host: "foohost",
-			Port: "443", // since this is the default HTTPS port, should not be included in Location value
+			Port: HTTPSPort, // since this is the 'default' HTTPS port, should not be included in Location value
 		},
 		{
 			Host:        "*.example.com",

caddyhttp/httpserver/plugin.go

@@ -91,11 +91,13 @@ func hideCaddyfile(cctx caddy.Context) error {
 	return nil
 }
 
-func newContext() caddy.Context {
-	return &httpContext{keysToSiteConfigs: make(map[string]*SiteConfig)}
+func newContext(inst *caddy.Instance) caddy.Context {
+	return &httpContext{instance: inst, keysToSiteConfigs: make(map[string]*SiteConfig)}
 }
 
 type httpContext struct {
+	instance *caddy.Instance
+
 	// keysToSiteConfigs maps an address at the top of a
 	// server block (a "key") to its SiteConfig. Not all
 	// SiteConfigs will be represented here, only ones
@@ -115,12 +117,14 @@ func (h *httpContext) saveConfig(key string, cfg *SiteConfig) {
 // executing directives and otherwise prepares the directives to
 // be parsed and executed.
 func (h *httpContext) InspectServerBlocks(sourceFile string, serverBlocks []caddyfile.ServerBlock) ([]caddyfile.ServerBlock, error) {
+	siteAddrs := make(map[string]string)
+
 	// For each address in each server block, make a new config
 	for _, sb := range serverBlocks {
 		for _, key := range sb.Keys {
 			key = strings.ToLower(key)
 			if _, dup := h.keysToSiteConfigs[key]; dup {
-				return serverBlocks, fmt.Errorf("duplicate site address: %s", key)
+				return serverBlocks, fmt.Errorf("duplicate site key: %s", key)
 			}
 			addr, err := standardizeAddress(key)
 			if err != nil {
@@ -136,6 +140,23 @@ func (h *httpContext) InspectServerBlocks(sourceFile string, serverBlocks []cadd
 				addr.Port = Port
 			}
 
+			// Make sure the adjusted site address is distinct
+			addrCopy := addr // make copy so we don't disturb the original, carefully-parsed address struct
+			if addrCopy.Port == "" && Port == DefaultPort {
+				addrCopy.Port = Port
+			}
+			addrStr := strings.ToLower(addrCopy.String())
+			if otherSiteKey, dup := siteAddrs[addrStr]; dup {
+				err := fmt.Errorf("duplicate site address: %s", addrStr)
+				if (addrCopy.Host == Host && Host != DefaultHost) ||
+					(addrCopy.Port == Port && Port != DefaultPort) {
+					err = fmt.Errorf("site defined as %s is a duplicate of %s because of modified "+
+						"default host and/or port values (usually via -host or -port flags)", key, otherSiteKey)
+				}
+				return serverBlocks, err
+			}
+			siteAddrs[addrStr] = key
+
 			// If default HTTP or HTTPS ports have been customized,
 			// make sure the ACME challenge ports match
 			var altHTTPPort, altTLSSNIPort string
@@ -146,15 +167,19 @@ func (h *httpContext) InspectServerBlocks(sourceFile string, serverBlocks []cadd
 				altTLSSNIPort = HTTPSPort
 			}
 
+			// Make our caddytls.Config, which has a pointer to the
+			// instance's certificate cache and enough information
+			// to use automatic HTTPS when the time comes
+			caddytlsConfig := caddytls.NewConfig(h.instance)
+			caddytlsConfig.Hostname = addr.Host
+			caddytlsConfig.AltHTTPPort = altHTTPPort
+			caddytlsConfig.AltTLSSNIPort = altTLSSNIPort
+
 			// Save the config to our master list, and key it for lookups
 			cfg := &SiteConfig{
-				Addr: addr,
-				Root: Root,
-				TLS: &caddytls.Config{
-					Hostname:      addr.Host,
-					AltHTTPPort:   altHTTPPort,
-					AltTLSSNIPort: altTLSSNIPort,
-				},
+				Addr:            addr,
+				Root:            Root,
+				TLS:             caddytlsConfig,
 				originCaddyfile: sourceFile,
 				IndexPages:      staticfiles.DefaultIndexPages,
 			}

caddyhttp/httpserver/plugin_test.go

@@ -137,7 +137,7 @@ func TestAddressString(t *testing.T) {
 func TestInspectServerBlocksWithCustomDefaultPort(t *testing.T) {
 	Port = "9999"
 	filename := "Testfile"
-	ctx := newContext().(*httpContext)
+	ctx := newContext(&caddy.Instance{Storage: make(map[interface{}]interface{})}).(*httpContext)
 	input := strings.NewReader(`localhost`)
 	sblocks, err := caddyfile.Parse(filename, input, nil)
 	if err != nil {
@@ -153,9 +153,26 @@ func TestInspectServerBlocksWithCustomDefaultPort(t *testing.T) {
 	}
 }
 
+// See discussion on PR #2015
+func TestInspectServerBlocksWithAdjustedAddress(t *testing.T) {
+	Port = DefaultPort
+	Host = "example.com"
+	filename := "Testfile"
+	ctx := newContext(&caddy.Instance{Storage: make(map[interface{}]interface{})}).(*httpContext)
+	input := strings.NewReader("example.com {\n}\n:2015 {\n}")
+	sblocks, err := caddyfile.Parse(filename, input, nil)
+	if err != nil {
+		t.Fatalf("Expected no error setting up test, got: %v", err)
+	}
+	_, err = ctx.InspectServerBlocks(filename, sblocks)
+	if err == nil {
+		t.Fatalf("Expected an error because site definitions should overlap, got: %v", err)
+	}
+}
+
 func TestInspectServerBlocksCaseInsensitiveKey(t *testing.T) {
 	filename := "Testfile"
-	ctx := newContext().(*httpContext)
+	ctx := newContext(&caddy.Instance{Storage: make(map[interface{}]interface{})}).(*httpContext)
 	input := strings.NewReader("localhost {\n}\nLOCALHOST {\n}")
 	sblocks, err := caddyfile.Parse(filename, input, nil)
 	if err != nil {
@@ -207,7 +224,7 @@ func TestDirectivesList(t *testing.T) {
 }
 
 func TestContextSaveConfig(t *testing.T) {
-	ctx := newContext().(*httpContext)
+	ctx := newContext(&caddy.Instance{Storage: make(map[interface{}]interface{})}).(*httpContext)
 	ctx.saveConfig("foo", new(SiteConfig))
 	if _, ok := ctx.keysToSiteConfigs["foo"]; !ok {
 		t.Error("Expected config to be saved, but it wasn't")
@@ -226,7 +243,7 @@ func TestContextSaveConfig(t *testing.T) {
 
 // Test to make sure we are correctly hiding the Caddyfile
 func TestHideCaddyfile(t *testing.T) {
-	ctx := newContext().(*httpContext)
+	ctx := newContext(&caddy.Instance{Storage: make(map[interface{}]interface{})}).(*httpContext)
 	ctx.saveConfig("test", &SiteConfig{
 		Root:            Root,
 		originCaddyfile: "Testfile",

caddyhttp/httpserver/server.go

@@ -389,7 +389,7 @@ func (s *Server) serveHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 	if vhost == nil {
 		// check for ACME challenge even if vhost is nil;
 		// could be a new host coming online soon
-		if caddytls.HTTPChallengeHandler(w, r, "localhost", caddytls.DefaultHTTPAlternatePort) {
+		if caddytls.HTTPChallengeHandler(w, r, "localhost") {
 			return 0, nil
 		}
 		// otherwise, log the error and write a message to the client
@@ -405,7 +405,7 @@ func (s *Server) serveHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 
 	// we still check for ACME challenge if the vhost exists,
 	// because we must apply its HTTP challenge config settings
-	if s.proxyHTTPChallenge(vhost, w, r) {
+	if caddytls.HTTPChallengeHandler(w, r, vhost.ListenHost) {
 		return 0, nil
 	}
 
@@ -422,24 +422,6 @@ func (s *Server) serveHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 	return vhost.middlewareChain.ServeHTTP(w, r)
 }
 
-// proxyHTTPChallenge solves the ACME HTTP challenge if r is the HTTP
-// request for the challenge. If it is, and if the request has been
-// fulfilled (response written), true is returned; false otherwise.
-// If you don't have a vhost, just call the challenge handler directly.
-func (s *Server) proxyHTTPChallenge(vhost *SiteConfig, w http.ResponseWriter, r *http.Request) bool {
-	if vhost.Addr.Port != caddytls.HTTPChallengePort {
-		return false
-	}
-	if vhost.TLS != nil && vhost.TLS.Manual {
-		return false
-	}
-	altPort := caddytls.DefaultHTTPAlternatePort
-	if vhost.TLS != nil && vhost.TLS.AltHTTPPort != "" {
-		altPort = vhost.TLS.AltHTTPPort
-	}
-	return caddytls.HTTPChallengeHandler(w, r, vhost.ListenHost, altPort)
-}
-
 // Address returns the address s was assigned to listen on.
 func (s *Server) Address() string {
 	return s.Server.Addr

caddytls/certificates.go

@@ -15,9 +15,11 @@
 package caddytls
 
 import (
+	"crypto/sha256"
 	"crypto/tls"
 	"crypto/x509"
 	"errors"
+	"fmt"
 	"io/ioutil"
 	"log"
 	"strings"
@@ -27,24 +29,104 @@ import (
 	"golang.org/x/crypto/ocsp"
 )
 
-// certCache stores certificates in memory,
-// keying certificates by name. Certificates
-// should not overlap in the names they serve,
-// because a name only maps to one certificate.
-var certCache = make(map[string]Certificate)
-var certCacheMu sync.RWMutex
+// certificateCache is to be an instance-wide cache of certs
+// that site-specific TLS configs can refer to. Using a
+// central map like this avoids duplication of certs in
+// memory when the cert is used by multiple sites, and makes
+// maintenance easier. Because these are not to be global,
+// the cache will get garbage collected after a config reload
+// (a new instance will take its place).
+type certificateCache struct {
+	sync.RWMutex
+	cache map[string]Certificate // keyed by certificate hash
+}
+
+// replaceCertificate replaces oldCert with newCert in the cache, and
+// updates all configs that are pointing to the old certificate to
+// point to the new one instead. newCert must already be loaded into
+// the cache (this method does NOT load it into the cache).
+//
+// Note that all the names on the old certificate will be deleted
+// from the name lookup maps of each config, then all the names on
+// the new certificate will be added to the lookup maps as long as
+// they do not overwrite any entries.
+//
+// The newCert may be modified and its cache entry updated.
+//
+// This method is safe for concurrent use.
+func (certCache *certificateCache) replaceCertificate(oldCert, newCert Certificate) error {
+	certCache.Lock()
+	defer certCache.Unlock()
+
+	// have all the configs that are pointing to the old
+	// certificate point to the new certificate instead
+	for _, cfg := range oldCert.configs {
+		// first delete all the name lookup entries that
+		// pointed to the old certificate
+		for name, certKey := range cfg.Certificates {
+			if certKey == oldCert.Hash {
+				delete(cfg.Certificates, name)
+			}
+		}
+
+		// then add name lookup entries for the names
+		// on the new certificate, but don't overwrite
+		// entries that may already exist, not only as
+		// a courtesy, but importantly: because if we
+		// overwrote a value here, and this config no
+		// longer pointed to a certain certificate in
+		// the cache, that certificate's list of configs
+		// referring to it would be incorrect; so just
+		// insert entries, don't overwrite any
+		for _, name := range newCert.Names {
+			if _, ok := cfg.Certificates[name]; !ok {
+				cfg.Certificates[name] = newCert.Hash
+			}
+		}
+	}
+
+	// since caching a new certificate attaches only the config
+	// that loaded it, the new certificate needs to be given the
+	// list of all the configs that use it, so copy the list
+	// over from the old certificate to the new certificate
+	// in the cache
+	newCert.configs = oldCert.configs
+	certCache.cache[newCert.Hash] = newCert
+
+	// finally, delete the old certificate from the cache
+	delete(certCache.cache, oldCert.Hash)
+
+	return nil
+}
+
+// reloadManagedCertificate reloads the certificate corresponding to the name(s)
+// on oldCert into the cache, from storage. This also replaces the old certificate
+// with the new one, so that all configurations that used the old cert now point
+// to the new cert.
+func (certCache *certificateCache) reloadManagedCertificate(oldCert Certificate) error {
+	// get the certificate from storage and cache it
+	newCert, err := oldCert.configs[0].CacheManagedCertificate(oldCert.Names[0])
+	if err != nil {
+		return fmt.Errorf("unable to reload certificate for %v into cache: %v", oldCert.Names, err)
+	}
+
+	// and replace the old certificate with the new one
+	err = certCache.replaceCertificate(oldCert, newCert)
+	if err != nil {
+		return fmt.Errorf("replacing certificate %v: %v", oldCert.Names, err)
+	}
+
+	return nil
+}
 
 // Certificate is a tls.Certificate with associated metadata tacked on.
 // Even if the metadata can be obtained by parsing the certificate,
-// we can be more efficient by extracting the metadata once so it's
-// just there, ready to use.
+// we are more efficient by extracting the metadata onto this struct.
 type Certificate struct {
 	tls.Certificate
 
 	// Names is the list of names this certificate is written for.
 	// The first is the CommonName (if any), the rest are SAN.
-	// This should be the exact list of keys by which this cert
-	// is accessed in the cache, careful to avoid overlap.
 	Names []string
 
 	// NotAfter is when the certificate expires.
@@ -53,59 +135,21 @@ type Certificate struct {
 	// OCSP contains the certificate's parsed OCSP response.
 	OCSP *ocsp.Response
 
-	// Config is the configuration with which the certificate was
-	// loaded or obtained and with which it should be maintained.
-	Config *Config
-}
+	// The hex-encoded hash of this cert's chain's bytes.
+	Hash string
 
-// getCertificate gets a certificate that matches name (a server name)
-// from the in-memory cache. If there is no exact match for name, it
-// will be checked against names of the form '*.example.com' (wildcard
-// certificates) according to RFC 6125. If a match is found, matched will
-// be true. If no matches are found, matched will be false and a default
-// certificate will be returned with defaulted set to true. If no default
-// certificate is set, defaulted will be set to false.
-//
-// The logic in this function is adapted from the Go standard library,
-// which is by the Go Authors.
-//
-// This function is safe for concurrent use.
-func getCertificate(name string) (cert Certificate, matched, defaulted bool) {
-	var ok bool
-
-	// Not going to trim trailing dots here since RFC 3546 says,
-	// "The hostname is represented ... without a trailing dot."
-	// Just normalize to lowercase.
-	name = strings.ToLower(name)
-
-	certCacheMu.RLock()
-	defer certCacheMu.RUnlock()
-
-	// exact match? great, let's use it
-	if cert, ok = certCache[name]; ok {
-		matched = true
-		return
-	}
-
-	// try replacing labels in the name with wildcards until we get a match
-	labels := strings.Split(name, ".")
-	for i := range labels {
-		labels[i] = "*"
-		candidate := strings.Join(labels, ".")
-		if cert, ok = certCache[candidate]; ok {
-			matched = true
-			return
-		}
-	}
-
-	// if nothing matches, use the default certificate or bust
-	cert, defaulted = certCache[""]
-	return
+	// configs is the list of configs that use or refer to
+	// The first one is assumed to be the config that is
+	// "in charge" of this certificate (i.e. determines
+	// whether it is managed, how it is managed, etc).
+	// This field will be populated by cacheCertificate.
+	// Only meddle with it if you know what you're doing!
+	configs []*Config
 }
 
 // CacheManagedCertificate loads the certificate for domain into the
-// cache, flagging it as Managed and, if onDemand is true, as "OnDemand"
-// (meaning that it was obtained or loaded during a TLS handshake).
+// cache, from the TLS storage for managed certificates. It returns a
+// copy of the Certificate that was put into the cache.
 //
 // This method is safe for concurrent use.
 func (cfg *Config) CacheManagedCertificate(domain string) (Certificate, error) {
@@ -117,39 +161,24 @@ func (cfg *Config) CacheManagedCertificate(domain string) (Certificate, error) {
 	if err != nil {
 		return Certificate{}, err
 	}
-	cert, err := makeCertificate(siteData.Cert, siteData.Key)
+	cert, err := makeCertificateWithOCSP(siteData.Cert, siteData.Key)
 	if err != nil {
 		return cert, err
 	}
-	cert.Config = cfg
-	cacheCertificate(cert)
-	return cert, nil
+	return cfg.cacheCertificate(cert), nil
 }
 
 // cacheUnmanagedCertificatePEMFile loads a certificate for host using certFile
 // and keyFile, which must be in PEM format. It stores the certificate in
-// memory after evicting any other entries in the cache keyed by the names
-// on this certificate. In other words, it replaces existing certificates keyed
-// by the names on this certificate. The Managed and OnDemand flags of the
-// certificate will be set to false.
+// the in-memory cache.
 //
 // This function is safe for concurrent use.
-func cacheUnmanagedCertificatePEMFile(certFile, keyFile string) error {
-	cert, err := makeCertificateFromDisk(certFile, keyFile)
+func (cfg *Config) cacheUnmanagedCertificatePEMFile(certFile, keyFile string) error {
+	cert, err := makeCertificateFromDiskWithOCSP(certFile, keyFile)
 	if err != nil {
 		return err
 	}
-
-	// since this is manually managed, this call might be part of a reload after
-	// the owner renewed a certificate; so clear cache of any previous cert first,
-	// otherwise the renewed certificate may never be loaded
-	certCacheMu.Lock()
-	for _, name := range cert.Names {
-		delete(certCache, name)
-	}
-	certCacheMu.Unlock()
-
-	cacheCertificate(cert)
+	cfg.cacheCertificate(cert)
 	return nil
 }
 
@@ -157,20 +186,20 @@ func cacheUnmanagedCertificatePEMFile(certFile, keyFile string) error {
 // of the certificate and key, then caches it in memory.
 //
 // This function is safe for concurrent use.
-func cacheUnmanagedCertificatePEMBytes(certBytes, keyBytes []byte) error {
-	cert, err := makeCertificate(certBytes, keyBytes)
+func (cfg *Config) cacheUnmanagedCertificatePEMBytes(certBytes, keyBytes []byte) error {
+	cert, err := makeCertificateWithOCSP(certBytes, keyBytes)
 	if err != nil {
 		return err
 	}
-	cacheCertificate(cert)
+	cfg.cacheCertificate(cert)
 	return nil
 }
 
-// makeCertificateFromDisk makes a Certificate by loading the
+// makeCertificateFromDiskWithOCSP makes a Certificate by loading the
 // certificate and key files. It fills out all the fields in
 // the certificate except for the Managed and OnDemand flags.
-// (It is up to the caller to set those.)
-func makeCertificateFromDisk(certFile, keyFile string) (Certificate, error) {
+// (It is up to the caller to set those.) It staples OCSP.
+func makeCertificateFromDiskWithOCSP(certFile, keyFile string) (Certificate, error) {
 	certPEMBlock, err := ioutil.ReadFile(certFile)
 	if err != nil {
 		return Certificate{}, err
@@ -179,13 +208,14 @@ func makeCertificateFromDisk(certFile, keyFile string) (Certificate, error) {
 	if err != nil {
 		return Certificate{}, err
 	}
-	return makeCertificate(certPEMBlock, keyPEMBlock)
+	return makeCertificateWithOCSP(certPEMBlock, keyPEMBlock)
 }
 
 // makeCertificate turns a certificate PEM bundle and a key PEM block into
-// a Certificate, with OCSP and other relevant metadata tagged with it,
-// except for the OnDemand and Managed flags. It is up to the caller to
-// set those properties.
+// a Certificate with necessary metadata from parsing its bytes filled into
+// its struct fields for convenience (except for the OnDemand and Managed
+// flags; it is up to the caller to set those properties!). This function
+// does NOT staple OCSP.
 func makeCertificate(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
 	var cert Certificate
 
@@ -195,16 +225,26 @@ func makeCertificate(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
 		return cert, err
 	}
 
-	// Extract relevant metadata and staple OCSP
+	// Extract necessary metadata
 	err = fillCertFromLeaf(&cert, tlsCert)
 	if err != nil {
 		return cert, err
 	}
+
+	return cert, nil
+}
+
+// makeCertificateWithOCSP is the same as makeCertificate except that it also
+// staples OCSP to the certificate.
+func makeCertificateWithOCSP(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
+	cert, err := makeCertificate(certPEMBlock, keyPEMBlock)
+	if err != nil {
+		return cert, err
+	}
 	err = stapleOCSP(&cert, certPEMBlock)
 	if err != nil {
 		log.Printf("[WARNING] Stapling OCSP: %v", err)
 	}
-
 	return cert, nil
 }
 
@@ -243,65 +283,104 @@ func fillCertFromLeaf(cert *Certificate, tlsCert tls.Certificate) error {
 		return errors.New("certificate has no names")
 	}
 
+	// save the hash of this certificate (chain) and
+	// expiration date, for necessity and efficiency
+	cert.Hash = hashCertificateChain(cert.Certificate.Certificate)
 	cert.NotAfter = leaf.NotAfter
 
 	return nil
 }
 
-// cacheCertificate adds cert to the in-memory cache. If the cache is
-// empty, cert will be used as the default certificate. If the cache is
-// full, random entries are deleted until there is room to map all the
-// names on the certificate.
+// hashCertificateChain computes the unique hash of certChain,
+// which is the chain of DER-encoded bytes. It returns the
+// hex encoding of the hash.
+func hashCertificateChain(certChain [][]byte) string {
+	h := sha256.New()
+	for _, certInChain := range certChain {
+		h.Write(certInChain)
+	}
+	return fmt.Sprintf("%x", h.Sum(nil))
+}
+
+// managedCertInStorageExpiresSoon returns true if cert (being a
+// managed certificate) is expiring within RenewDurationBefore.
+// It returns false if there was an error checking the expiration
+// of the certificate as found in storage, or if the certificate
+// in storage is NOT expiring soon. A certificate that is expiring
+// soon in our cache but is not expiring soon in storage probably
+// means that another instance renewed the certificate in the
+// meantime, and it would be a good idea to simply load the cert
+// into our cache rather than repeating the renewal process again.
+func managedCertInStorageExpiresSoon(cert Certificate) (bool, error) {
+	if len(cert.configs) == 0 {
+		return false, fmt.Errorf("no configs for certificate")
+	}
+	storage, err := cert.configs[0].StorageFor(cert.configs[0].CAUrl)
+	if err != nil {
+		return false, err
+	}
+	siteData, err := storage.LoadSite(cert.Names[0])
+	if err != nil {
+		return false, err
+	}
+	tlsCert, err := tls.X509KeyPair(siteData.Cert, siteData.Key)
+	if err != nil {
+		return false, err
+	}
+	leaf, err := x509.ParseCertificate(tlsCert.Certificate[0])
+	if err != nil {
+		return false, err
+	}
+	timeLeft := leaf.NotAfter.Sub(time.Now().UTC())
+	return timeLeft < RenewDurationBefore, nil
+}
+
+// cacheCertificate adds cert to the in-memory cache. If a certificate
+// with the same hash is already cached, it is NOT overwritten; instead,
+// cfg is added to the existing certificate's list of configs if not
+// already in the list. Then all the names on cert are used to add
+// entries to cfg.Certificates (the config's name lookup map).
+// Then the certificate is stored/updated in the cache. It returns
+// a copy of the certificate that ends up being stored in the cache.
 //
-// This certificate will be keyed to the names in cert.Names. Any names
-// already used as a cache key will NOT be replaced by this cert; in
-// other words, no overlap is allowed, and this certificate will not
-// service those pre-existing names.
+// It is VERY important, even for some test cases, that the Hash field
+// of the cert be set properly.
 //
 // This function is safe for concurrent use.
-func cacheCertificate(cert Certificate) {
-	if cert.Config == nil {
-		cert.Config = new(Config)
+func (cfg *Config) cacheCertificate(cert Certificate) Certificate {
+	cfg.certCache.Lock()
+	defer cfg.certCache.Unlock()
+
+	// if this certificate already exists in the cache,
+	// use it instead of overwriting it -- very important!
+	if existingCert, ok := cfg.certCache.cache[cert.Hash]; ok {
+		cert = existingCert
 	}
-	certCacheMu.Lock()
-	if _, ok := certCache[""]; !ok {
-		// use as default - must be *appended* to end of list, or bad things happen!
-		cert.Names = append(cert.Names, "")
-	}
-	for len(certCache)+len(cert.Names) > 10000 {
-		// for simplicity, just remove random elements
-		for key := range certCache {
-			if key == "" { // ... but not the default cert
-				continue
-			}
-			delete(certCache, key)
+
+	// attach this config to the certificate so we know which
+	// configs are referencing/using the certificate, but don't
+	// duplicate entries
+	var found bool
+	for _, c := range cert.configs {
+		if c == cfg {
+			found = true
 			break
 		}
 	}
-	for i := 0; i < len(cert.Names); i++ {
-		name := cert.Names[i]
-		if _, ok := certCache[name]; ok {
-			// do not allow certificates to overlap in the names they serve;
-			// this ambiguity causes problems because it is confusing while
-			// maintaining certificates; see OCSP maintenance code and
-			// https://caddy.community/t/random-ocsp-response-errors-for-random-clients/2473?u=matt.
-			log.Printf("[NOTICE] There is already a certificate loaded for %s, "+
-				"so certificate for %v will not service that name",
-				name, cert.Names)
-			cert.Names = append(cert.Names[:i], cert.Names[i+1:]...)
-			i--
-			continue
-		}
-		certCache[name] = cert
+	if !found {
+		cert.configs = append(cert.configs, cfg)
 	}
-	certCacheMu.Unlock()
-}
 
-// uncacheCertificate deletes name's certificate from the
-// cache. If name is not a key in the certificate cache,
-// this function does nothing.
-func uncacheCertificate(name string) {
-	certCacheMu.Lock()
-	delete(certCache, name)
-	certCacheMu.Unlock()
+	// key the certificate by all its names for this config only,
+	// this is how we find the certificate during handshakes
+	// (yes, if certs overlap in the names they serve, one will
+	// overwrite another here, but that's just how it goes)
+	for _, name := range cert.Names {
+		cfg.Certificates[name] = cert.Hash
+	}
+
+	// store the certificate
+	cfg.certCache.cache[cert.Hash] = cert
+
+	return cert
 }

caddytls/certificates_test.go

@@ -17,57 +17,71 @@ package caddytls
 import "testing"
 
 func TestUnexportedGetCertificate(t *testing.T) {
-	defer func() { certCache = make(map[string]Certificate) }()
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 
 	// When cache is empty
-	if _, matched, defaulted := getCertificate("example.com"); matched || defaulted {
+	if _, matched, defaulted := cfg.getCertificate("example.com"); matched || defaulted {
 		t.Errorf("Got a certificate when cache was empty; matched=%v, defaulted=%v", matched, defaulted)
 	}
 
-	// When cache has one certificate in it (also is default)
-	defaultCert := Certificate{Names: []string{"example.com", ""}}
-	certCache[""] = defaultCert
-	certCache["example.com"] = defaultCert
-	if cert, matched, defaulted := getCertificate("Example.com"); !matched || defaulted || cert.Names[0] != "example.com" {
+	// When cache has one certificate in it
+	firstCert := Certificate{Names: []string{"example.com"}}
+	certCache.cache["0xdeadbeef"] = firstCert
+	cfg.Certificates["example.com"] = "0xdeadbeef"
+	if cert, matched, defaulted := cfg.getCertificate("Example.com"); !matched || defaulted || cert.Names[0] != "example.com" {
 		t.Errorf("Didn't get a cert for 'Example.com' or got the wrong one: %v, matched=%v, defaulted=%v", cert, matched, defaulted)
 	}
-	if cert, matched, defaulted := getCertificate(""); !matched || defaulted || cert.Names[0] != "example.com" {
-		t.Errorf("Didn't get a cert for '' or got the wrong one: %v, matched=%v, defaulted=%v", cert, matched, defaulted)
+	if cert, matched, defaulted := cfg.getCertificate("example.com"); !matched || defaulted || cert.Names[0] != "example.com" {
+		t.Errorf("Didn't get a cert for 'example.com' or got the wrong one: %v, matched=%v, defaulted=%v", cert, matched, defaulted)
 	}
 
 	// When retrieving wildcard certificate
-	certCache["*.example.com"] = Certificate{Names: []string{"*.example.com"}}
-	if cert, matched, defaulted := getCertificate("sub.example.com"); !matched || defaulted || cert.Names[0] != "*.example.com" {
+	certCache.cache["0xb01dface"] = Certificate{Names: []string{"*.example.com"}}
+	cfg.Certificates["*.example.com"] = "0xb01dface"
+	if cert, matched, defaulted := cfg.getCertificate("sub.example.com"); !matched || defaulted || cert.Names[0] != "*.example.com" {
 		t.Errorf("Didn't get wildcard cert for 'sub.example.com' or got the wrong one: %v, matched=%v, defaulted=%v", cert, matched, defaulted)
 	}
 
-	// When no certificate matches, the default is returned
-	if cert, matched, defaulted := getCertificate("nomatch"); matched || !defaulted {
+	// When no certificate matches and SNI is provided, return no certificate (should be TLS alert)
+	if cert, matched, defaulted := cfg.getCertificate("nomatch"); matched || defaulted {
+		t.Errorf("Expected matched=false, defaulted=false; but got matched=%v, defaulted=%v (cert: %v)", matched, defaulted, cert)
+	}
+
+	// When no certificate matches and SNI is NOT provided, a random is returned
+	if cert, matched, defaulted := cfg.getCertificate(""); matched || !defaulted {
 		t.Errorf("Expected matched=false, defaulted=true; but got matched=%v, defaulted=%v (cert: %v)", matched, defaulted, cert)
-	} else if cert.Names[0] != "example.com" {
-		t.Errorf("Expected default cert, got: %v", cert)
 	}
 }
 
 func TestCacheCertificate(t *testing.T) {
-	defer func() { certCache = make(map[string]Certificate) }()
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 
-	cacheCertificate(Certificate{Names: []string{"example.com", "sub.example.com"}})
-	if _, ok := certCache["example.com"]; !ok {
-		t.Error("Expected first cert to be cached by key 'example.com', but it wasn't")
+	cfg.cacheCertificate(Certificate{Names: []string{"example.com", "sub.example.com"}, Hash: "foobar"})
+	if len(certCache.cache) != 1 {
+		t.Errorf("Expected length of certificate cache to be 1")
 	}
-	if _, ok := certCache["sub.example.com"]; !ok {
-		t.Error("Expected first cert to be cached by key 'sub.example.com', but it wasn't")
+	if _, ok := certCache.cache["foobar"]; !ok {
+		t.Error("Expected first cert to be cached by key 'foobar', but it wasn't")
 	}
-	if cert, ok := certCache[""]; !ok || cert.Names[2] != "" {
-		t.Error("Expected first cert to be cached additionally as the default certificate with empty name added, but it wasn't")
+	if _, ok := cfg.Certificates["example.com"]; !ok {
+		t.Error("Expected first cert to be keyed by 'example.com', but it wasn't")
+	}
+	if _, ok := cfg.Certificates["sub.example.com"]; !ok {
+		t.Error("Expected first cert to be keyed by 'sub.example.com', but it wasn't")
 	}
 
-	cacheCertificate(Certificate{Names: []string{"example2.com"}})
-	if _, ok := certCache["example2.com"]; !ok {
-		t.Error("Expected second cert to be cached by key 'exmaple2.com', but it wasn't")
+	// different config, but using same cache; and has cert with overlapping name,
+	// but different hash
+	cfg2 := &Config{Certificates: make(map[string]string), certCache: certCache}
+	cfg2.cacheCertificate(Certificate{Names: []string{"example.com"}, Hash: "barbaz"})
+	if _, ok := certCache.cache["barbaz"]; !ok {
+		t.Error("Expected second cert to be cached by key 'barbaz.com', but it wasn't")
 	}
-	if cert, ok := certCache[""]; ok && cert.Names[0] == "example2.com" {
-		t.Error("Expected second cert to NOT be cached as default, but it was")
+	if hash, ok := cfg2.Certificates["example.com"]; !ok {
+		t.Error("Expected second cert to be keyed by 'example.com', but it wasn't")
+	} else if hash != "barbaz" {
+		t.Errorf("Expected second cert to map to 'barbaz' but it was %s instead", hash)
 	}
 }

caddytls/client.go

@@ -39,7 +39,7 @@ type ACMEClient struct {
 	AllowPrompts bool
 	config       *Config
 	acmeClient   *acme.Client
-	locker       Locker
+	storage      Storage
 }
 
 // newACMEClient creates a new ACMEClient given an email and whether
@@ -121,10 +121,7 @@ var newACMEClient = func(config *Config, allowPrompts bool) (*ACMEClient, error)
 		AllowPrompts: allowPrompts,
 		config:       config,
 		acmeClient:   client,
-		locker: &syncLock{
-			nameLocks:   make(map[string]*sync.WaitGroup),
-			nameLocksMu: sync.Mutex{},
-		},
+		storage:      storage,
 	}
 
 	if config.DNSProvider == "" {
@@ -160,7 +157,7 @@ var newACMEClient = func(config *Config, allowPrompts bool) (*ACMEClient, error)
 
 		// See if TLS challenge needs to be handled by our own facilities
 		if caddy.HasListenerWithAddress(net.JoinHostPort(config.ListenHost, useTLSSNIPort)) {
-			c.acmeClient.SetChallengeProvider(acme.TLSSNI01, tlsSniSolver{})
+			c.acmeClient.SetChallengeProvider(acme.TLSSNI01, tlsSNISolver{certCache: config.certCache})
 		}
 
 		// Disable any challenges that should not be used
@@ -209,13 +206,7 @@ var newACMEClient = func(config *Config, allowPrompts bool) (*ACMEClient, error)
 // Callers who have access to a Config value should use the ObtainCert
 // method on that instead of this lower-level method.
 func (c *ACMEClient) Obtain(name string) error {
-	// Get access to ACME storage
-	storage, err := c.config.StorageFor(c.config.CAUrl)
-	if err != nil {
-		return err
-	}
-
-	waiter, err := c.locker.TryLock(name)
+	waiter, err := c.storage.TryLock(name)
 	if err != nil {
 		return err
 	}
@@ -225,7 +216,7 @@ func (c *ACMEClient) Obtain(name string) error {
 		return nil // we assume the process with the lock succeeded, rather than hammering this execution path again
 	}
 	defer func() {
-		if err := c.locker.Unlock(name); err != nil {
+		if err := c.storage.Unlock(name); err != nil {
 			log.Printf("[ERROR] Unable to unlock obtain call for %s: %v", name, err)
 		}
 	}()
@@ -268,7 +259,7 @@ Attempts:
 		}
 
 		// Success - immediately save the certificate resource
-		err = saveCertResource(storage, certificate)
+		err = saveCertResource(c.storage, certificate)
 		if err != nil {
 			return fmt.Errorf("error saving assets for %v: %v", name, err)
 		}
@@ -279,35 +270,30 @@ Attempts:
 	return nil
 }
 
-// Renew renews the managed certificate for name. This function is
-// safe for concurrent use.
+// Renew renews the managed certificate for name. It puts the renewed
+// certificate into storage (not the cache). This function is safe for
+// concurrent use.
 //
 // Callers who have access to a Config value should use the RenewCert
 // method on that instead of this lower-level method.
 func (c *ACMEClient) Renew(name string) error {
-	// Get access to ACME storage
-	storage, err := c.config.StorageFor(c.config.CAUrl)
-	if err != nil {
-		return err
-	}
-
-	waiter, err := c.locker.TryLock(name)
+	waiter, err := c.storage.TryLock(name)
 	if err != nil {
 		return err
 	}
 	if waiter != nil {
 		log.Printf("[INFO] Certificate for %s is already being renewed elsewhere and stored; waiting", name)
 		waiter.Wait()
-		return nil // we assume the process with the lock succeeded, rather than hammering this execution path again
+		return nil // assume that the worker that renewed the cert succeeded; avoid hammering this path over and over
 	}
 	defer func() {
-		if err := c.locker.Unlock(name); err != nil {
+		if err := c.storage.Unlock(name); err != nil {
 			log.Printf("[ERROR] Unable to unlock renew call for %s: %v", name, err)
 		}
 	}()
 
 	// Prepare for renewal (load PEM cert, key, and meta)
-	siteData, err := storage.LoadSite(name)
+	siteData, err := c.storage.LoadSite(name)
 	if err != nil {
 		return err
 	}
@@ -350,21 +336,15 @@ func (c *ACMEClient) Renew(name string) error {
 		return errors.New("too many renewal attempts; last error: " + err.Error())
 	}
 
-	// Executes Cert renew events
 	caddy.EmitEvent(caddy.CertRenewEvent, name)
 
-	return saveCertResource(storage, newCertMeta)
+	return saveCertResource(c.storage, newCertMeta)
 }
 
-// Revoke revokes the certificate for name and deltes
+// Revoke revokes the certificate for name and deletes
 // it from storage.
 func (c *ACMEClient) Revoke(name string) error {
-	storage, err := c.config.StorageFor(c.config.CAUrl)
-	if err != nil {
-		return err
-	}
-
-	siteExists, err := storage.SiteExists(name)
+	siteExists, err := c.storage.SiteExists(name)
 	if err != nil {
 		return err
 	}
@@ -373,7 +353,7 @@ func (c *ACMEClient) Revoke(name string) error {
 		return errors.New("no certificate and key for " + name)
 	}
 
-	siteData, err := storage.LoadSite(name)
+	siteData, err := c.storage.LoadSite(name)
 	if err != nil {
 		return err
 	}
@@ -383,7 +363,7 @@ func (c *ACMEClient) Revoke(name string) error {
 		return err
 	}
 
-	err = storage.DeleteSite(name)
+	err = c.storage.DeleteSite(name)
 	if err != nil {
 		return errors.New("certificate revoked, but unable to delete certificate file: " + err.Error())
 	}

caddytls/config.go

@@ -93,16 +93,17 @@ type Config struct {
 	// an ACME challenge
 	ListenHost string
 
-	// The alternate port (ONLY port, not host)
-	// to use for the ACME HTTP challenge; this
-	// port will be used if we proxy challenges
-	// coming in on port 80 to this alternate port
+	// The alternate port (ONLY port, not host) to
+	// use for the ACME HTTP challenge; if non-empty,
+	// this port will be used instead of
+	// HTTPChallengePort to spin up a listener for
+	// the HTTP challenge
 	AltHTTPPort string
 
 	// The alternate port (ONLY port, not host)
 	// to use for the ACME TLS-SNI challenge.
-	// The system must forward the standard port
-	// for the TLS-SNI challenge to this port.
+	// The system must forward TLSSNIChallengePort
+	// to this port for challenge to succeed
 	AltTLSSNIPort string
 
 	// The string identifier of the DNS provider
@@ -134,7 +135,12 @@ type Config struct {
 	// Protocol Negotiation (ALPN).
 	ALPN []string
 
-	tlsConfig *tls.Config // the final tls.Config created with buildStandardTLSConfig()
+	// The map of hostname to certificate hash. This is used to complete
+	// handshakes and serve the right certificate given the SNI.
+	Certificates map[string]string
+
+	certCache *certificateCache // pointer to the Instance's certificate store
+	tlsConfig *tls.Config       // the final tls.Config created with buildStandardTLSConfig()
 }
 
 // OnDemandState contains some state relevant for providing
@@ -155,6 +161,25 @@ type OnDemandState struct {
 	AskURL *url.URL
 }
 
+// NewConfig returns a new Config with a pointer to the instance's
+// certificate cache. You will usually need to set Other fields on
+// the returned Config for successful practical use.
+func NewConfig(inst *caddy.Instance) *Config {
+	inst.StorageMu.RLock()
+	certCache, ok := inst.Storage[CertCacheInstStorageKey].(*certificateCache)
+	inst.StorageMu.RUnlock()
+	if !ok || certCache == nil {
+		certCache = &certificateCache{cache: make(map[string]Certificate)}
+		inst.StorageMu.Lock()
+		inst.Storage[CertCacheInstStorageKey] = certCache
+		inst.StorageMu.Unlock()
+	}
+	cfg := new(Config)
+	cfg.Certificates = make(map[string]string)
+	cfg.certCache = certCache
+	return cfg
+}
+
 // ObtainCert obtains a certificate for name using c, as long
 // as a certificate does not already exist in storage for that
 // name. The name must qualify and c must be flagged as Managed.
@@ -330,7 +355,9 @@ func (c *Config) buildStandardTLSConfig() error {
 
 // MakeTLSConfig makes a tls.Config from configs. The returned
 // tls.Config is programmed to load the matching caddytls.Config
-// based on the hostname in SNI, but that's all.
+// based on the hostname in SNI, but that's all. This is used
+// to create a single TLS configuration for a listener (a group
+// of sites).
 func MakeTLSConfig(configs []*Config) (*tls.Config, error) {
 	if len(configs) == 0 {
 		return nil, nil
@@ -358,15 +385,28 @@ func MakeTLSConfig(configs []*Config) (*tls.Config, error) {
 				configs[i-1].Hostname, lastConfProto, cfg.Hostname, thisConfProto)
 		}
 
-		// convert each caddytls.Config into a tls.Config
+		// convert this caddytls.Config into a tls.Config
 		if err := cfg.buildStandardTLSConfig(); err != nil {
 			return nil, err
 		}
 
-		// Key this config by its hostname (overwriting
-		// configs with the same hostname pattern); during
-		// TLS handshakes, configs are loaded based on
-		// the hostname pattern, according to client's SNI.
+		// if an existing config with this hostname was already
+		// configured, then they must be identical (or at least
+		// compatible), otherwise that is a configuration error
+		if otherConfig, ok := configMap[cfg.Hostname]; ok {
+			if err := assertConfigsCompatible(cfg, otherConfig); err != nil {
+				return nil, fmt.Errorf("incompabile TLS configurations for the same SNI "+
+					"name (%s) on the same listener: %v",
+					cfg.Hostname, err)
+			}
+		}
+
+		// key this config by its hostname (overwrites
+		// configs with the same hostname pattern; should
+		// be OK since we already asserted they are roughly
+		// the same); during TLS handshakes, configs are
+		// loaded based on the hostname pattern, according
+		// to client's SNI
 		configMap[cfg.Hostname] = cfg
 	}
 
@@ -383,6 +423,63 @@ func MakeTLSConfig(configs []*Config) (*tls.Config, error) {
 	}, nil
 }
 
+// assertConfigsCompatible returns an error if the two Configs
+// do not have the same (or roughly compatible) configurations.
+// If one of the tlsConfig pointers on either Config is nil,
+// an error will be returned. If both are nil, no error.
+func assertConfigsCompatible(cfg1, cfg2 *Config) error {
+	c1, c2 := cfg1.tlsConfig, cfg2.tlsConfig
+
+	if (c1 == nil && c2 != nil) || (c1 != nil && c2 == nil) {
+		return fmt.Errorf("one config is not made")
+	}
+	if c1 == nil && c2 == nil {
+		return nil
+	}
+
+	if len(c1.CipherSuites) != len(c2.CipherSuites) {
+		return fmt.Errorf("different number of allowed cipher suites")
+	}
+	for i, ciph := range c1.CipherSuites {
+		if c2.CipherSuites[i] != ciph {
+			return fmt.Errorf("different cipher suites or different order")
+		}
+	}
+
+	if len(c1.CurvePreferences) != len(c2.CurvePreferences) {
+		return fmt.Errorf("different number of allowed cipher suites")
+	}
+	for i, curve := range c1.CurvePreferences {
+		if c2.CurvePreferences[i] != curve {
+			return fmt.Errorf("different curve preferences or different order")
+		}
+	}
+
+	if len(c1.NextProtos) != len(c2.NextProtos) {
+		return fmt.Errorf("different number of ALPN (NextProtos) values")
+	}
+	for i, proto := range c1.NextProtos {
+		if c2.NextProtos[i] != proto {
+			return fmt.Errorf("different ALPN (NextProtos) values or different order")
+		}
+	}
+
+	if c1.PreferServerCipherSuites != c2.PreferServerCipherSuites {
+		return fmt.Errorf("one prefers server cipher suites, the other does not")
+	}
+	if c1.MinVersion != c2.MinVersion {
+		return fmt.Errorf("minimum TLS version mismatch")
+	}
+	if c1.MaxVersion != c2.MaxVersion {
+		return fmt.Errorf("maximum TLS version mismatch")
+	}
+	if c1.ClientAuth != c2.ClientAuth {
+		return fmt.Errorf("client authentication policy mismatch")
+	}
+
+	return nil
+}
+
 // ConfigGetter gets a Config keyed by key.
 type ConfigGetter func(c *caddy.Controller) *Config
 
@@ -522,7 +619,7 @@ var supportedCurvesMap = map[string]tls.CurveID{
 	"P521":   tls.CurveP521,
 }
 
-// List of all the curves we want to use by default
+// List of all the curves we want to use by default.
 //
 // This list should only include curves which are fast by design (e.g. X25519)
 // and those for which an optimized assembly implementation exists (e.g. P256).
@@ -548,4 +645,8 @@ const (
 	// be capable of proxying or forwarding the request to this
 	// alternate port.
 	DefaultHTTPAlternatePort = "5033"
+
+	// CertCacheInstStorageKey is the name of the key for
+	// accessing the certificate storage on the *caddy.Instance.
+	CertCacheInstStorageKey = "tls_cert_cache"
 )

caddytls/crypto.go

@@ -237,15 +237,17 @@ func makeSelfSignedCert(config *Config) error {
 		return fmt.Errorf("could not create certificate: %v", err)
 	}
 
-	cacheCertificate(Certificate{
+	chain := [][]byte{derBytes}
+
+	config.cacheCertificate(Certificate{
 		Certificate: tls.Certificate{
-			Certificate: [][]byte{derBytes},
+			Certificate: chain,
 			PrivateKey:  privKey,
 			Leaf:        cert,
 		},
 		Names:    cert.DNSNames,
 		NotAfter: cert.NotAfter,
-		Config:   config,
+		Hash:     hashCertificateChain(chain),
 	})
 
 	return nil

caddytls/filestorage.go

@@ -38,9 +38,9 @@ var storageBasePath = filepath.Join(caddy.AssetsPath(), "acme")
 // Storage instance backed by the local disk. The resulting Storage
 // instance is guaranteed to be non-nil if there is no error.
 func NewFileStorage(caURL *url.URL) (Storage, error) {
-	return &FileStorage{
-		Path: filepath.Join(storageBasePath, caURL.Host),
-	}, nil
+	storage := &FileStorage{Path: filepath.Join(storageBasePath, caURL.Host)}
+	storage.Locker = &fileStorageLock{caURL: caURL.Host, storage: storage}
+	return storage, nil
 }
 
 // FileStorage facilitates forming file paths derived from a root
@@ -48,6 +48,7 @@ func NewFileStorage(caURL *url.URL) (Storage, error) {
 // cross-platform way or persisting ACME assets on the file system.
 type FileStorage struct {
 	Path string
+	Locker
 }
 
 // sites gets the directory that stores site certificate and keys.

caddytls/filestoragesync.go

@@ -0,0 +1,127 @@
+// Copyright 2015 Light Code Labs, LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddytls
+
+import (
+	"fmt"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	// be sure to remove lock files when exiting the process!
+	caddy.OnProcessExit = append(caddy.OnProcessExit, func() {
+		fileStorageNameLocksMu.Lock()
+		defer fileStorageNameLocksMu.Unlock()
+		for key, fw := range fileStorageNameLocks {
+			os.Remove(fw.filename)
+			delete(fileStorageNameLocks, key)
+		}
+	})
+}
+
+// fileStorageLock facilitates ACME-related locking by using
+// the associated FileStorage, so multiple processes can coordinate
+// renewals on the certificates on a shared file system.
+type fileStorageLock struct {
+	caURL   string
+	storage *FileStorage
+}
+
+// TryLock attempts to get a lock for name, otherwise it returns
+// a Waiter value to wait until the other process is finished.
+func (s *fileStorageLock) TryLock(name string) (Waiter, error) {
+	fileStorageNameLocksMu.Lock()
+	defer fileStorageNameLocksMu.Unlock()
+
+	// see if lock already exists within this process
+	fw, ok := fileStorageNameLocks[s.caURL+name]
+	if ok {
+		// lock already created within process, let caller wait on it
+		return fw, nil
+	}
+
+	// attempt to persist lock to disk by creating lock file
+	fw = &fileWaiter{
+		filename: s.storage.siteCertFile(name) + ".lock",
+		wg:       new(sync.WaitGroup),
+	}
+	// parent dir must exist
+	if err := os.MkdirAll(s.storage.site(name), 0700); err != nil {
+		return nil, err
+	}
+	lf, err := os.OpenFile(fw.filename, os.O_CREATE|os.O_EXCL, 0644)
+	if err != nil {
+		if os.IsExist(err) {
+			// another process has the lock; use it to wait
+			return fw, nil
+		}
+		// otherwise, this was some unexpected error
+		return nil, err
+	}
+	lf.Close()
+
+	// looks like we get the lock
+	fw.wg.Add(1)
+	fileStorageNameLocks[s.caURL+name] = fw
+
+	return nil, nil
+}
+
+// Unlock unlocks name.
+func (s *fileStorageLock) Unlock(name string) error {
+	fileStorageNameLocksMu.Lock()
+	defer fileStorageNameLocksMu.Unlock()
+	fw, ok := fileStorageNameLocks[s.caURL+name]
+	if !ok {
+		return fmt.Errorf("FileStorage: no lock to release for %s", name)
+	}
+	os.Remove(fw.filename)
+	fw.wg.Done()
+	delete(fileStorageNameLocks, s.caURL+name)
+	return nil
+}
+
+// fileWaiter waits for a file to disappear; it polls
+// the file system to check for the existence of a file.
+// It also has a WaitGroup which will be faster than
+// polling, for when locking need only happen within this
+// process.
+type fileWaiter struct {
+	filename string
+	wg       *sync.WaitGroup
+}
+
+// Wait waits until the lock is released.
+func (fw *fileWaiter) Wait() {
+	start := time.Now()
+	fw.wg.Wait()
+	for time.Since(start) < 1*time.Hour {
+		_, err := os.Stat(fw.filename)
+		if os.IsNotExist(err) {
+			return
+		}
+		time.Sleep(1 * time.Second)
+	}
+}
+
+var fileStorageNameLocks = make(map[string]*fileWaiter) // keyed by CA + name
+var fileStorageNameLocksMu sync.Mutex
+
+var _ Locker = &fileStorageLock{}
+var _ Waiter = &fileWaiter{}

caddytls/handshake.go

@@ -59,15 +59,15 @@ func (cg configGroup) getConfig(name string) *Config {
 		}
 	}
 
-	// as a fallback, try a config that serves all names
+	// try a config that serves all names (this
+	// is basically the same as a config defined
+	// for "*" -- I think -- but the above loop
+	// doesn't try an empty string)
 	if config, ok := cg[""]; ok {
 		return config
 	}
 
-	// as a last resort, use a random config
-	// (even if the config isn't for that hostname,
-	// it should help us serve clients without SNI
-	// or at least defer TLS alerts to the cert)
+	// no matches, so just serve up a random config
 	for _, config := range cg {
 		return config
 	}
@@ -102,6 +102,86 @@ func (cfg *Config) GetCertificate(clientHello *tls.ClientHelloInfo) (*tls.Certif
 	return &cert.Certificate, err
 }
 
+// getCertificate gets a certificate that matches name (a server name)
+// from the in-memory cache, according to the lookup table associated with
+// cfg. The lookup then points to a certificate in the Instance certificate
+// cache.
+//
+// If there is no exact match for name, it will be checked against names of
+// the form '*.example.com' (wildcard certificates) according to RFC 6125.
+// If a match is found, matched will be true. If no matches are found, matched
+// will be false and a "default" certificate will be returned with defaulted
+// set to true. If defaulted is false, then no certificates were available.
+//
+// The logic in this function is adapted from the Go standard library,
+// which is by the Go Authors.
+//
+// This function is safe for concurrent use.
+func (cfg *Config) getCertificate(name string) (cert Certificate, matched, defaulted bool) {
+	var certKey string
+	var ok bool
+
+	// Not going to trim trailing dots here since RFC 3546 says,
+	// "The hostname is represented ... without a trailing dot."
+	// Just normalize to lowercase.
+	name = strings.ToLower(name)
+
+	cfg.certCache.RLock()
+	defer cfg.certCache.RUnlock()
+
+	// exact match? great, let's use it
+	if certKey, ok = cfg.Certificates[name]; ok {
+		cert = cfg.certCache.cache[certKey]
+		matched = true
+		return
+	}
+
+	// try replacing labels in the name with wildcards until we get a match
+	labels := strings.Split(name, ".")
+	for i := range labels {
+		labels[i] = "*"
+		candidate := strings.Join(labels, ".")
+		if certKey, ok = cfg.Certificates[candidate]; ok {
+			cert = cfg.certCache.cache[certKey]
+			matched = true
+			return
+		}
+	}
+
+	// check the certCache directly to see if the SNI name is
+	// already the key of the certificate it wants! this is vital
+	// for supporting the TLS-SNI challenge, since the tlsSNISolver
+	// just puts the temporary certificate in the instance cache,
+	// with no regard for configs; this also means that the SNI
+	// can contain the hash of a specific cert (chain) it wants
+	// and we will still be able to serve it up
+	// (this behavior, by the way, could be controversial as to
+	// whether it complies with RFC 6066 about SNI, but I think
+	// it does soooo...)
+	// NOTE/TODO: TLS-SNI challenge is changing, as of Jan. 2018
+	// but what will be different, if it ever returns, is unclear
+	if directCert, ok := cfg.certCache.cache[name]; ok {
+		cert = directCert
+		matched = true
+		return
+	}
+
+	// if nothing matches and SNI was not provided, use a random
+	// certificate; at least there's a chance this older client
+	// can connect, and in the future we won't need this provision
+	// (if SNI is present, it's probably best to just raise a TLS
+	// alert by not serving a certificate)
+	if name == "" {
+		for _, certKey := range cfg.Certificates {
+			defaulted = true
+			cert = cfg.certCache.cache[certKey]
+			return
+		}
+	}
+
+	return
+}
+
 // getCertDuringHandshake will get a certificate for name. It first tries
 // the in-memory cache. If no certificate for name is in the cache, the
 // config most closely corresponding to name will be loaded. If that config
@@ -115,7 +195,7 @@ func (cfg *Config) GetCertificate(clientHello *tls.ClientHelloInfo) (*tls.Certif
 // This function is safe for concurrent use.
 func (cfg *Config) getCertDuringHandshake(name string, loadIfNecessary, obtainIfNecessary bool) (Certificate, error) {
 	// First check our in-memory cache to see if we've already loaded it
-	cert, matched, defaulted := getCertificate(name)
+	cert, matched, defaulted := cfg.getCertificate(name)
 	if matched {
 		return cert, nil
 	}
@@ -258,7 +338,7 @@ func (cfg *Config) obtainOnDemandCertificate(name string) (Certificate, error) {
 	obtainCertWaitChans[name] = wait
 	obtainCertWaitChansMu.Unlock()
 
-	// do the obtain
+	// obtain the certificate
 	log.Printf("[INFO] Obtaining new certificate for %s", name)
 	err := cfg.ObtainCert(name, false)
 
@@ -317,9 +397,9 @@ func (cfg *Config) handshakeMaintenance(name string, cert Certificate) (Certific
 				// quite common considering not all certs have issuer URLs that support it.
 				log.Printf("[ERROR] Getting OCSP for %s: %v", name, err)
 			}
-			certCacheMu.Lock()
-			certCache[name] = cert
-			certCacheMu.Unlock()
+			cfg.certCache.Lock()
+			cfg.certCache.cache[cert.Hash] = cert
+			cfg.certCache.Unlock()
 		}
 	}
 
@@ -348,29 +428,22 @@ func (cfg *Config) renewDynamicCertificate(name string, currentCert Certificate)
 	obtainCertWaitChans[name] = wait
 	obtainCertWaitChansMu.Unlock()
 
-	// do the renew and reload the certificate
+	// renew and reload the certificate
 	log.Printf("[INFO] Renewing certificate for %s", name)
 	err := cfg.RenewCert(name, false)
 	if err == nil {
-		// immediately flush this certificate from the cache so
-		// the name doesn't overlap when we try to replace it,
-		// which would fail, because overlapping existing cert
-		// names isn't allowed
-		certCacheMu.Lock()
-		for _, certName := range currentCert.Names {
-			delete(certCache, certName)
-		}
-		certCacheMu.Unlock()
-
 		// even though the recursive nature of the dynamic cert loading
 		// would just call this function anyway, we do it here to
-		// make the replacement as atomic as possible. (TODO: similar
-		// to the note in maintain.go, it'd be nice if the clearing of
-		// the cache entries above and this load function were truly
-		// atomic...)
-		_, err := currentCert.Config.CacheManagedCertificate(name)
+		// make the replacement as atomic as possible.
+		newCert, err := currentCert.configs[0].CacheManagedCertificate(name)
 		if err != nil {
-			log.Printf("[ERROR] loading renewed certificate: %v", err)
+			log.Printf("[ERROR] loading renewed certificate for %s: %v", name, err)
+		} else {
+			// replace the old certificate with the new one
+			err = cfg.certCache.replaceCertificate(currentCert, newCert)
+			if err != nil {
+				log.Printf("[ERROR] Replacing certificate for %s: %v", name, err)
+			}
 		}
 	}
 

caddytls/handshake_test.go

@@ -21,9 +21,8 @@ import (
 )
 
 func TestGetCertificate(t *testing.T) {
-	defer func() { certCache = make(map[string]Certificate) }()
-
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 
 	hello := &tls.ClientHelloInfo{ServerName: "example.com"}
 	helloSub := &tls.ClientHelloInfo{ServerName: "sub.example.com"}
@@ -38,33 +37,40 @@ func TestGetCertificate(t *testing.T) {
 		t.Errorf("GetCertificate should return error when cache is empty even if server name is blank, got: %v", cert)
 	}
 
-	// When cache has one certificate in it (also is default)
-	defaultCert := Certificate{Names: []string{"example.com", ""}, Certificate: tls.Certificate{Leaf: &x509.Certificate{DNSNames: []string{"example.com"}}}}
-	certCache[""] = defaultCert
-	certCache["example.com"] = defaultCert
+	// When cache has one certificate in it
+	firstCert := Certificate{Names: []string{"example.com"}, Certificate: tls.Certificate{Leaf: &x509.Certificate{DNSNames: []string{"example.com"}}}}
+	cfg.cacheCertificate(firstCert)
 	if cert, err := cfg.GetCertificate(hello); err != nil {
 		t.Errorf("Got an error but shouldn't have, when cert exists in cache: %v", err)
 	} else if cert.Leaf.DNSNames[0] != "example.com" {
 		t.Errorf("Got wrong certificate with exact match; expected 'example.com', got: %v", cert)
 	}
-	if cert, err := cfg.GetCertificate(helloNoSNI); err != nil {
+	if _, err := cfg.GetCertificate(helloNoSNI); err != nil {
 		t.Errorf("Got an error with no SNI but shouldn't have, when cert exists in cache: %v", err)
-	} else if cert.Leaf.DNSNames[0] != "example.com" {
-		t.Errorf("Got wrong certificate for no SNI; expected 'example.com' as default, got: %v", cert)
 	}
 
 	// When retrieving wildcard certificate
-	certCache["*.example.com"] = Certificate{Names: []string{"*.example.com"}, Certificate: tls.Certificate{Leaf: &x509.Certificate{DNSNames: []string{"*.example.com"}}}}
+	wildcardCert := Certificate{
+		Names:       []string{"*.example.com"},
+		Certificate: tls.Certificate{Leaf: &x509.Certificate{DNSNames: []string{"*.example.com"}}},
+		Hash:        "(don't overwrite the first one)",
+	}
+	cfg.cacheCertificate(wildcardCert)
 	if cert, err := cfg.GetCertificate(helloSub); err != nil {
 		t.Errorf("Didn't get wildcard cert, got: cert=%v, err=%v ", cert, err)
 	} else if cert.Leaf.DNSNames[0] != "*.example.com" {
 		t.Errorf("Got wrong certificate, expected wildcard: %v", cert)
 	}
 
-	// When no certificate matches, the default is returned
-	if cert, err := cfg.GetCertificate(helloNoMatch); err != nil {
-		t.Errorf("Expected default certificate with no error when no matches, got err: %v", err)
-	} else if cert.Leaf.DNSNames[0] != "example.com" {
-		t.Errorf("Expected default cert with no matches, got: %v", cert)
+	// When cache is NOT empty but there's no SNI
+	if cert, err := cfg.GetCertificate(helloNoSNI); err != nil {
+		t.Errorf("Expected random certificate with no error when no SNI, got err: %v", err)
+	} else if cert == nil || len(cert.Leaf.DNSNames) == 0 {
+		t.Errorf("Expected random cert with no matches, got: %v", cert)
+	}
+
+	// When no certificate matches, raise an alert
+	if _, err := cfg.GetCertificate(helloNoMatch); err == nil {
+		t.Errorf("Expected an error when no certificate matched the SNI, got: %v", err)
 	}
 }

caddytls/httphandler.go

@@ -27,10 +27,11 @@ import (
 const challengeBasePath = "/.well-known/acme-challenge"
 
 // HTTPChallengeHandler proxies challenge requests to ACME client if the
-// request path starts with challengeBasePath. It returns true if it
-// handled the request and no more needs to be done; it returns false
-// if this call was a no-op and the request still needs handling.
-func HTTPChallengeHandler(w http.ResponseWriter, r *http.Request, listenHost, altPort string) bool {
+// request path starts with challengeBasePath, if the HTTP challenge is not
+// disabled, and if we are known to be obtaining a certificate for the name.
+// It returns true if it handled the request and no more needs to be done;
+// it returns false if this call was a no-op and the request still needs handling.
+func HTTPChallengeHandler(w http.ResponseWriter, r *http.Request, listenHost string) bool {
 	if !strings.HasPrefix(r.URL.Path, challengeBasePath) {
 		return false
 	}
@@ -50,7 +51,11 @@ func HTTPChallengeHandler(w http.ResponseWriter, r *http.Request, listenHost, al
 		listenHost = "localhost"
 	}
 
-	upstream, err := url.Parse(fmt.Sprintf("%s://%s:%s", scheme, listenHost, altPort))
+	// always proxy to the DefaultHTTPAlternatePort because obviously the
+	// ACME challenge request already got into one of our HTTP handlers, so
+	// it means we must have started a HTTP listener on the alternate
+	// port instead; which is only accessible via listenHost
+	upstream, err := url.Parse(fmt.Sprintf("%s://%s:%s", scheme, listenHost, DefaultHTTPAlternatePort))
 	if err != nil {
 		w.WriteHeader(http.StatusInternalServerError)
 		log.Printf("[ERROR] ACME proxy handler: %v", err)

caddytls/httphandler_test.go

@@ -39,7 +39,7 @@ func TestHTTPChallengeHandlerNoOp(t *testing.T) {
 			t.Fatalf("Could not craft request, got error: %v", err)
 		}
 		rw := httptest.NewRecorder()
-		if HTTPChallengeHandler(rw, req, "", DefaultHTTPAlternatePort) {
+		if HTTPChallengeHandler(rw, req, "") {
 			t.Errorf("Got true with this URL, but shouldn't have: %s", url)
 		}
 	}
@@ -76,7 +76,7 @@ func TestHTTPChallengeHandlerSuccess(t *testing.T) {
 	}
 	rw := httptest.NewRecorder()
 
-	HTTPChallengeHandler(rw, req, "", DefaultHTTPAlternatePort)
+	HTTPChallengeHandler(rw, req, "")
 
 	if !proxySuccess {
 		t.Fatal("Expected request to be proxied, but it wasn't")

caddytls/maintain.go

@@ -87,103 +87,127 @@ func maintainAssets(stopChan chan struct{}) {
 // RenewManagedCertificates renews managed certificates,
 // including ones loaded on-demand.
 func RenewManagedCertificates(allowPrompts bool) (err error) {
-	var renewQueue, deleteQueue []Certificate
-	visitedNames := make(map[string]struct{})
-
-	certCacheMu.RLock()
-	for name, cert := range certCache {
-		if !cert.Config.Managed || cert.Config.SelfSigned {
+	for _, inst := range caddy.Instances() {
+		inst.StorageMu.RLock()
+		certCache, ok := inst.Storage[CertCacheInstStorageKey].(*certificateCache)
+		inst.StorageMu.RUnlock()
+		if !ok || certCache == nil {
 			continue
 		}
 
-		// the list of names on this cert should never be empty...
-		if cert.Names == nil || len(cert.Names) == 0 {
-			log.Printf("[WARNING] Certificate keyed by '%s' has no names: %v - removing from cache", name, cert.Names)
-			deleteQueue = append(deleteQueue, cert)
-			continue
-		}
+		// we use the queues for a very important reason: to do any and all
+		// operations that could require an exclusive write lock outside
+		// of the read lock! otherwise we get a deadlock, yikes. in other
+		// words, our first iteration through the certificate cache does NOT
+		// perform any operations--only queues them--so that more fine-grained
+		// write locks may be obtained during the actual operations.
+		var renewQueue, reloadQueue, deleteQueue []Certificate
 
-		// skip names whose certificate we've already renewed
-		if _, ok := visitedNames[name]; ok {
-			continue
-		}
-		for _, name := range cert.Names {
-			visitedNames[name] = struct{}{}
-		}
-
-		// if its time is up or ending soon, we need to try to renew it
-		timeLeft := cert.NotAfter.Sub(time.Now().UTC())
-		if timeLeft < RenewDurationBefore {
-			log.Printf("[INFO] Certificate for %v expires in %v; attempting renewal", cert.Names, timeLeft)
-
-			if cert.Config == nil {
-				log.Printf("[ERROR] %s: No associated TLS config; unable to renew", name)
+		certCache.RLock()
+		for certKey, cert := range certCache.cache {
+			if len(cert.configs) == 0 {
+				// this is bad if this happens, probably a programmer error (oops)
+				log.Printf("[ERROR] No associated TLS config for certificate with names %v; unable to manage", cert.Names)
+				continue
+			}
+			if !cert.configs[0].Managed || cert.configs[0].SelfSigned {
 				continue
 			}
 
-			// queue for renewal when we aren't in a read lock anymore
-			// (the TLS-SNI challenge will need a write lock in order to
-			// present the certificate, so we renew outside of read lock)
-			renewQueue = append(renewQueue, cert)
-		}
-	}
-	certCacheMu.RUnlock()
-
-	// Perform renewals that are queued
-	for _, cert := range renewQueue {
-		// Get the name which we should use to renew this certificate;
-		// we only support managing certificates with one name per cert,
-		// so this should be easy. We can't rely on cert.Config.Hostname
-		// because it may be a wildcard value from the Caddyfile (e.g.
-		// *.something.com) which, as of Jan. 2017, is not supported by ACME.
-		var renewName string
-		for _, name := range cert.Names {
-			if name != "" {
-				renewName = name
-				break
-			}
-		}
-
-		// perform renewal
-		err := cert.Config.RenewCert(renewName, allowPrompts)
-		if err != nil {
-			if allowPrompts {
-				// Certificate renewal failed and the operator is present. See a discussion
-				// about this in issue 642. For a while, we only stopped if the certificate
-				// was expired, but in reality, there is no difference between reporting
-				// it now versus later, except that there's somebody present to deal with
-				// it right now.
-				timeLeft := cert.NotAfter.Sub(time.Now().UTC())
-				if timeLeft < RenewDurationBeforeAtStartup {
-					// See issue 1680. Only fail at startup if the certificate is dangerously
-					// close to expiration.
-					return err
-				}
-			}
-			log.Printf("[ERROR] %v", err)
-			if cert.Config.OnDemand {
-				// loaded dynamically, removed dynamically
+			// the list of names on this cert should never be empty... programmer error?
+			if cert.Names == nil || len(cert.Names) == 0 {
+				log.Printf("[WARNING] Certificate keyed by '%s' has no names: %v - removing from cache", certKey, cert.Names)
 				deleteQueue = append(deleteQueue, cert)
+				continue
 			}
-		} else {
+
+			// if time is up or expires soon, we need to try to renew it
+			timeLeft := cert.NotAfter.Sub(time.Now().UTC())
+			if timeLeft < RenewDurationBefore {
+				// see if the certificate in storage has already been renewed, possibly by another
+				// instance of Caddy that didn't coordinate with this one; if so, just load it (this
+				// might happen if another instance already renewed it - kinda sloppy but checking disk
+				// first is a simple way to possibly drastically reduce rate limit problems)
+				storedCertExpiring, err := managedCertInStorageExpiresSoon(cert)
+				if err != nil {
+					// hmm, weird, but not a big deal, maybe it was deleted or something
+					log.Printf("[NOTICE] Error while checking if certificate for %v in storage is also expiring soon: %v",
+						cert.Names, err)
+				} else if !storedCertExpiring {
+					// if the certificate is NOT expiring soon and there was no error, then we
+					// are good to just reload the certificate from storage instead of repeating
+					// a likely-unnecessary renewal procedure
+					reloadQueue = append(reloadQueue, cert)
+					continue
+				}
+
+				// the certificate in storage has not been renewed yet, so we will do it
+				// NOTE 1: This is not correct 100% of the time, if multiple Caddy instances
+				// happen to run their maintenance checks at approximately the same times;
+				// both might start renewal at about the same time and do two renewals and one
+				// will overwrite the other. Hence TLS storage plugins. This is sort of a TODO.
+				// NOTE 2: It is super-important to note that the TLS-SNI challenge requires
+				// a write lock on the cache in order to complete its challenge, so it is extra
+				// vital that this renew operation does not happen inside our read lock!
+				renewQueue = append(renewQueue, cert)
+			}
+		}
+		certCache.RUnlock()
+
+		// Reload certificates that merely need to be updated in memory
+		for _, oldCert := range reloadQueue {
+			timeLeft := oldCert.NotAfter.Sub(time.Now().UTC())
+			log.Printf("[INFO] Certificate for %v expires in %v, but is already renewed in storage; reloading stored certificate",
+				oldCert.Names, timeLeft)
+
+			err = certCache.reloadManagedCertificate(oldCert)
+			if err != nil {
+				if allowPrompts {
+					return err // operator is present, so report error immediately
+				}
+				log.Printf("[ERROR] Loading renewed certificate: %v", err)
+			}
+		}
+
+		// Renewal queue
+		for _, oldCert := range renewQueue {
+			timeLeft := oldCert.NotAfter.Sub(time.Now().UTC())
+			log.Printf("[INFO] Certificate for %v expires in %v; attempting renewal", oldCert.Names, timeLeft)
+
+			// Get the name which we should use to renew this certificate;
+			// we only support managing certificates with one name per cert,
+			// so this should be easy. We can't rely on cert.Config.Hostname
+			// because it may be a wildcard value from the Caddyfile (e.g.
+			// *.something.com) which, as of Jan. 2017, is not supported by ACME.
+			// TODO: ^ ^ ^ (wildcards)
+			renewName := oldCert.Names[0]
+
+			// perform renewal
+			err := oldCert.configs[0].RenewCert(renewName, allowPrompts)
+			if err != nil {
+				if allowPrompts {
+					// Certificate renewal failed and the operator is present. See a discussion
+					// about this in issue 642. For a while, we only stopped if the certificate
+					// was expired, but in reality, there is no difference between reporting
+					// it now versus later, except that there's somebody present to deal with
+					// it right now. Follow-up: See issue 1680. Only fail in this case if the
+					// certificate is dangerously close to expiration.
+					timeLeft := oldCert.NotAfter.Sub(time.Now().UTC())
+					if timeLeft < RenewDurationBeforeAtStartup {
+						return err
+					}
+				}
+				log.Printf("[ERROR] %v", err)
+				if oldCert.configs[0].OnDemand {
+					// loaded dynamically, remove dynamically
+					deleteQueue = append(deleteQueue, oldCert)
+				}
+				continue
+			}
+
 			// successful renewal, so update in-memory cache by loading
 			// renewed certificate so it will be used with handshakes
-
-			// we must delete all the names this cert services from the cache
-			// so that we can replace the certificate, because replacing names
-			// already in the cache is not allowed, to avoid later conflicts
-			// with renewals.
-			// TODO: It would be nice if this whole operation were idempotent;
-			// i.e. a thread-safe function to replace a certificate in the cache,
-			// see also handshake.go for on-demand maintenance.
-			certCacheMu.Lock()
-			for _, name := range cert.Names {
-				delete(certCache, name)
-			}
-			certCacheMu.Unlock()
-
-			// put the certificate in the cache
-			_, err := cert.Config.CacheManagedCertificate(cert.Names[0])
+			err = certCache.reloadManagedCertificate(oldCert)
 			if err != nil {
 				if allowPrompts {
 					return err // operator is present, so report error immediately
@@ -191,15 +215,22 @@ func RenewManagedCertificates(allowPrompts bool) (err error) {
 				log.Printf("[ERROR] %v", err)
 			}
 		}
-	}
 
-	// Apply queued deletion changes to the cache
-	for _, cert := range deleteQueue {
-		certCacheMu.Lock()
-		for _, name := range cert.Names {
-			delete(certCache, name)
+		// Deletion queue
+		for _, cert := range deleteQueue {
+			certCache.Lock()
+			// remove any pointers to this certificate from Configs
+			for _, cfg := range cert.configs {
+				for name, certKey := range cfg.Certificates {
+					if certKey == cert.Hash {
+						delete(cfg.Certificates, name)
+					}
+				}
+			}
+			// then delete the certificate from the cache
+			delete(certCache.cache, cert.Hash)
+			certCache.Unlock()
 		}
-		certCacheMu.Unlock()
 	}
 
 	return nil
@@ -212,91 +243,75 @@ func RenewManagedCertificates(allowPrompts bool) (err error) {
 // Ryan Sleevi's recommendations for good OCSP support:
 // https://gist.github.com/sleevi/5efe9ef98961ecfb4da8
 func UpdateOCSPStaples() {
-	// Create a temporary place to store updates
-	// until we release the potentially long-lived
-	// read lock and use a short-lived write lock.
-	type ocspUpdate struct {
-		rawBytes []byte
-		parsed   *ocsp.Response
-	}
-	updated := make(map[string]ocspUpdate)
-
-	// A single SAN certificate maps to multiple names, so we use this
-	// set to make sure we don't waste cycles checking OCSP for the same
-	// certificate multiple times.
-	visited := make(map[string]struct{})
-
-	certCacheMu.RLock()
-	for name, cert := range certCache {
-		// skip this certificate if we've already visited it,
-		// and if not, mark all the names as visited
-		if _, ok := visited[name]; ok {
-			continue
-		}
-		for _, n := range cert.Names {
-			visited[n] = struct{}{}
-		}
-
-		// no point in updating OCSP for expired certificates
-		if time.Now().After(cert.NotAfter) {
+	for _, inst := range caddy.Instances() {
+		inst.StorageMu.RLock()
+		certCache, ok := inst.Storage[CertCacheInstStorageKey].(*certificateCache)
+		inst.StorageMu.RUnlock()
+		if !ok || certCache == nil {
 			continue
 		}
 
-		var lastNextUpdate time.Time
-		if cert.OCSP != nil {
-			lastNextUpdate = cert.OCSP.NextUpdate
-			if freshOCSP(cert.OCSP) {
-				// no need to update staple if ours is still fresh
+		// Create a temporary place to store updates
+		// until we release the potentially long-lived
+		// read lock and use a short-lived write lock
+		// on the certificate cache.
+		type ocspUpdate struct {
+			rawBytes []byte
+			parsed   *ocsp.Response
+		}
+		updated := make(map[string]ocspUpdate)
+
+		certCache.RLock()
+		for certHash, cert := range certCache.cache {
+			// no point in updating OCSP for expired certificates
+			if time.Now().After(cert.NotAfter) {
 				continue
 			}
-		}
 
-		err := stapleOCSP(&cert, nil)
-		if err != nil {
+			var lastNextUpdate time.Time
 			if cert.OCSP != nil {
-				// if there was no staple before, that's fine; otherwise we should log the error
-				log.Printf("[ERROR] Checking OCSP: %v", err)
+				lastNextUpdate = cert.OCSP.NextUpdate
+				if freshOCSP(cert.OCSP) {
+					continue // no need to update staple if ours is still fresh
+				}
 			}
-			continue
-		}
 
-		// By this point, we've obtained the latest OCSP response.
-		// If there was no staple before, or if the response is updated, make
-		// sure we apply the update to all names on the certificate.
-		if cert.OCSP != nil && (lastNextUpdate.IsZero() || lastNextUpdate != cert.OCSP.NextUpdate) {
-			log.Printf("[INFO] Advancing OCSP staple for %v from %s to %s",
-				cert.Names, lastNextUpdate, cert.OCSP.NextUpdate)
-			for _, n := range cert.Names {
-				// BUG: If this certificate has names on it that appear on another
-				// certificate in the cache, AND the other certificate is keyed by
-				// that name in the cache, then this method of 'queueing' the staple
-				// update will cause this certificate's new OCSP to be stapled to
-				// a different certificate! See:
-				// https://caddy.community/t/random-ocsp-response-errors-for-random-clients/2473?u=matt
-				// This problem should be avoided if names on certificates in the
-				// cache don't overlap with regards to the cache keys.
-				// (This is isn't a bug anymore, since we're careful when we add
-				// certificates to the cache by skipping keying when key already exists.)
-				updated[n] = ocspUpdate{rawBytes: cert.Certificate.OCSPStaple, parsed: cert.OCSP}
+			err := stapleOCSP(&cert, nil)
+			if err != nil {
+				if cert.OCSP != nil {
+					// if there was no staple before, that's fine; otherwise we should log the error
+					log.Printf("[ERROR] Checking OCSP: %v", err)
+				}
+				continue
+			}
+
+			// By this point, we've obtained the latest OCSP response.
+			// If there was no staple before, or if the response is updated, make
+			// sure we apply the update to all names on the certificate.
+			if cert.OCSP != nil && (lastNextUpdate.IsZero() || lastNextUpdate != cert.OCSP.NextUpdate) {
+				log.Printf("[INFO] Advancing OCSP staple for %v from %s to %s",
+					cert.Names, lastNextUpdate, cert.OCSP.NextUpdate)
+				updated[certHash] = ocspUpdate{rawBytes: cert.Certificate.OCSPStaple, parsed: cert.OCSP}
 			}
 		}
-	}
-	certCacheMu.RUnlock()
+		certCache.RUnlock()
 
-	// This write lock should be brief since we have all the info we need now.
-	certCacheMu.Lock()
-	for name, update := range updated {
-		cert := certCache[name]
-		cert.OCSP = update.parsed
-		cert.Certificate.OCSPStaple = update.rawBytes
-		certCache[name] = cert
+		// These write locks should be brief since we have all the info we need now.
+		for certKey, update := range updated {
+			certCache.Lock()
+			cert := certCache.cache[certKey]
+			cert.OCSP = update.parsed
+			cert.Certificate.OCSPStaple = update.rawBytes
+			certCache.cache[certKey] = cert
+			certCache.Unlock()
+		}
 	}
-	certCacheMu.Unlock()
 }
 
 // DeleteOldStapleFiles deletes cached OCSP staples that have expired.
 // TODO: Should we do this for certificates too?
 func DeleteOldStapleFiles() {
+	// TODO: Upgrade caddytls.Storage to support OCSP operations too
 	files, err := ioutil.ReadDir(ocspFolder)
 	if err != nil {
 		// maybe just hasn't been created yet; no big deal

caddytls/setup.go

@@ -38,6 +38,7 @@ func init() {
 // are specified by the user in the config file. All the automatic HTTPS
 // stuff comes later outside of this function.
 func setupTLS(c *caddy.Controller) error {
+	// obtain the configGetter, which loads the config we're, uh, configuring
 	configGetter, ok := configGetters[c.ServerType()]
 	if !ok {
 		return fmt.Errorf("no caddytls.ConfigGetter for %s server type; must call RegisterConfigGetter", c.ServerType())
@@ -47,6 +48,14 @@ func setupTLS(c *caddy.Controller) error {
 		return fmt.Errorf("no caddytls.Config to set up for %s", c.Key)
 	}
 
+	// the certificate cache is tied to the current caddy.Instance; get a pointer to it
+	certCache, ok := c.Get(CertCacheInstStorageKey).(*certificateCache)
+	if !ok || certCache == nil {
+		certCache = &certificateCache{cache: make(map[string]Certificate)}
+		c.Set(CertCacheInstStorageKey, certCache)
+	}
+	config.certCache = certCache
+
 	config.Enabled = true
 
 	for c.Next() {
@@ -237,7 +246,7 @@ func setupTLS(c *caddy.Controller) error {
 
 		// load a single certificate and key, if specified
 		if certificateFile != "" && keyFile != "" {
-			err := cacheUnmanagedCertificatePEMFile(certificateFile, keyFile)
+			err := config.cacheUnmanagedCertificatePEMFile(certificateFile, keyFile)
 			if err != nil {
 				return c.Errf("Unable to load certificate and key files for '%s': %v", c.Key, err)
 			}
@@ -246,7 +255,7 @@ func setupTLS(c *caddy.Controller) error {
 
 		// load a directory of certificates, if specified
 		if loadDir != "" {
-			err := loadCertsInDir(c, loadDir)
+			err := loadCertsInDir(config, c, loadDir)
 			if err != nil {
 				return err
 			}
@@ -273,7 +282,7 @@ func setupTLS(c *caddy.Controller) error {
 // https://cbonte.github.io/haproxy-dconv/configuration-1.5.html#5.1-crt
 //
 // This function may write to the log as it walks the directory tree.
-func loadCertsInDir(c *caddy.Controller, dir string) error {
+func loadCertsInDir(cfg *Config, c *caddy.Controller, dir string) error {
 	return filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
 		if err != nil {
 			log.Printf("[WARNING] Unable to traverse into %s; skipping", path)
@@ -336,7 +345,7 @@ func loadCertsInDir(c *caddy.Controller, dir string) error {
 				return c.Errf("%s: no private key block found", path)
 			}
 
-			err = cacheUnmanagedCertificatePEMBytes(certPEMBytes, keyPEMBytes)
+			err = cfg.cacheUnmanagedCertificatePEMBytes(certPEMBytes, keyPEMBytes)
 			if err != nil {
 				return c.Errf("%s: failed to load cert and key for '%s': %v", path, c.Key, err)
 			}

caddytls/setup_test.go

@@ -46,9 +46,12 @@ func TestMain(m *testing.M) {
 }
 
 func TestSetupParseBasic(t *testing.T) {
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
+
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c := caddy.NewTestController("", `tls `+certFile+` `+keyFile+``)
+	c.Set(CertCacheInstStorageKey, certCache)
 
 	err := setupTLS(c)
 	if err != nil {
@@ -124,9 +127,12 @@ func TestSetupParseWithOptionalParams(t *testing.T) {
             must_staple
             alpn http/1.1
         }`
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
+
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c := caddy.NewTestController("", params)
+	c.Set(CertCacheInstStorageKey, certCache)
 
 	err := setupTLS(c)
 	if err != nil {
@@ -158,9 +164,11 @@ func TestSetupDefaultWithOptionalParams(t *testing.T) {
 	params := `tls {
             ciphers RSA-3DES-EDE-CBC-SHA
         }`
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c := caddy.NewTestController("", params)
+	c.Set(CertCacheInstStorageKey, certCache)
 
 	err := setupTLS(c)
 	if err != nil {
@@ -176,9 +184,12 @@ func TestSetupParseWithWrongOptionalParams(t *testing.T) {
 	params := `tls ` + certFile + ` ` + keyFile + ` {
 			protocols ssl tls
 		}`
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c := caddy.NewTestController("", params)
+	c.Set(CertCacheInstStorageKey, certCache)
+
 	err := setupTLS(c)
 	if err == nil {
 		t.Errorf("Expected errors, but no error returned")
@@ -191,6 +202,7 @@ func TestSetupParseWithWrongOptionalParams(t *testing.T) {
 	cfg = new(Config)
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c = caddy.NewTestController("", params)
+	c.Set(CertCacheInstStorageKey, certCache)
 	err = setupTLS(c)
 	if err == nil {
 		t.Error("Expected errors, but no error returned")
@@ -215,6 +227,7 @@ func TestSetupParseWithWrongOptionalParams(t *testing.T) {
 	cfg = new(Config)
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c = caddy.NewTestController("", params)
+	c.Set(CertCacheInstStorageKey, certCache)
 	err = setupTLS(c)
 	if err == nil {
 		t.Error("Expected errors, but no error returned")
@@ -226,7 +239,8 @@ func TestSetupParseWithClientAuth(t *testing.T) {
 	params := `tls ` + certFile + ` ` + keyFile + ` {
 			clients
 		}`
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c := caddy.NewTestController("", params)
 	err := setupTLS(c)
@@ -259,9 +273,11 @@ func TestSetupParseWithClientAuth(t *testing.T) {
 			clients verify_if_given
 		}`, tls.VerifyClientCertIfGiven, true, noCAs},
 	} {
-		cfg := new(Config)
+		certCache := &certificateCache{cache: make(map[string]Certificate)}
+		cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 		RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 		c := caddy.NewTestController("", caseData.params)
+		c.Set(CertCacheInstStorageKey, certCache)
 		err := setupTLS(c)
 		if caseData.expectedErr {
 			if err == nil {
@@ -311,9 +327,11 @@ func TestSetupParseWithCAUrl(t *testing.T) {
 				ca 1 2
 			}`, true, ""},
 	} {
-		cfg := new(Config)
+		certCache := &certificateCache{cache: make(map[string]Certificate)}
+		cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 		RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 		c := caddy.NewTestController("", caseData.params)
+		c.Set(CertCacheInstStorageKey, certCache)
 		err := setupTLS(c)
 		if caseData.expectedErr {
 			if err == nil {
@@ -335,9 +353,11 @@ func TestSetupParseWithKeyType(t *testing.T) {
 	params := `tls {
             key_type p384
         }`
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c := caddy.NewTestController("", params)
+	c.Set(CertCacheInstStorageKey, certCache)
 
 	err := setupTLS(c)
 	if err != nil {
@@ -353,9 +373,11 @@ func TestSetupParseWithCurves(t *testing.T) {
 	params := `tls {
             curves x25519 p256 p384 p521
         }`
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c := caddy.NewTestController("", params)
+	c.Set(CertCacheInstStorageKey, certCache)
 
 	err := setupTLS(c)
 	if err != nil {
@@ -380,9 +402,11 @@ func TestSetupParseWithOneTLSProtocol(t *testing.T) {
 	params := `tls {
             protocols tls1.2
         }`
-	cfg := new(Config)
+	certCache := &certificateCache{cache: make(map[string]Certificate)}
+	cfg := &Config{Certificates: make(map[string]string), certCache: certCache}
 	RegisterConfigGetter("", func(c *caddy.Controller) *Config { return cfg })
 	c := caddy.NewTestController("", params)
+	c.Set(CertCacheInstStorageKey, certCache)
 
 	err := setupTLS(c)
 	if err != nil {

caddytls/storage.go

@@ -107,6 +107,10 @@ type Storage interface {
 	// in StoreUser. The result is an empty string if there are no
 	// persisted users in storage.
 	MostRecentUserEmail() string
+
+	// Locker is necessary because synchronizing certificate maintenance
+	// depends on how storage is implemented.
+	Locker
 }
 
 // ErrNotExist is returned by Storage implementations when

caddytls/sync_locker.go

@@ -1,57 +0,0 @@
-// Copyright 2015 Light Code Labs, LLC
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package caddytls
-
-import (
-	"fmt"
-	"sync"
-)
-
-var _ Locker = &syncLock{}
-
-type syncLock struct {
-	nameLocks   map[string]*sync.WaitGroup
-	nameLocksMu sync.Mutex
-}
-
-// TryLock attempts to get a lock for name, otherwise it returns
-// a Waiter value to wait until the other process is finished.
-func (s *syncLock) TryLock(name string) (Waiter, error) {
-	s.nameLocksMu.Lock()
-	defer s.nameLocksMu.Unlock()
-	wg, ok := s.nameLocks[name]
-	if ok {
-		// lock already obtained, let caller wait on it
-		return wg, nil
-	}
-	// caller gets lock
-	wg = new(sync.WaitGroup)
-	wg.Add(1)
-	s.nameLocks[name] = wg
-	return nil, nil
-}
-
-// Unlock unlocks name.
-func (s *syncLock) Unlock(name string) error {
-	s.nameLocksMu.Lock()
-	defer s.nameLocksMu.Unlock()
-	wg, ok := s.nameLocks[name]
-	if !ok {
-		return fmt.Errorf("FileStorage: no lock to release for %s", name)
-	}
-	wg.Done()
-	delete(s.nameLocks, name)
-	return nil
-}

caddytls/tls.go

@@ -88,30 +88,38 @@ func Revoke(host string) error {
 	return client.Revoke(host)
 }
 
-// tlsSniSolver is a type that can solve tls-sni challenges using
+// tlsSNISolver is a type that can solve TLS-SNI challenges using
 // an existing listener and our custom, in-memory certificate cache.
-type tlsSniSolver struct{}
+type tlsSNISolver struct {
+	certCache *certificateCache
+}
 
 // Present adds the challenge certificate to the cache.
-func (s tlsSniSolver) Present(domain, token, keyAuth string) error {
+func (s tlsSNISolver) Present(domain, token, keyAuth string) error {
 	cert, acmeDomain, err := acme.TLSSNI01ChallengeCert(keyAuth)
 	if err != nil {
 		return err
 	}
-	cacheCertificate(Certificate{
+	certHash := hashCertificateChain(cert.Certificate)
+	s.certCache.Lock()
+	s.certCache.cache[acmeDomain] = Certificate{
 		Certificate: cert,
 		Names:       []string{acmeDomain},
-	})
+		Hash:        certHash, // perhaps not necesssary
+	}
+	s.certCache.Unlock()
 	return nil
 }
 
 // CleanUp removes the challenge certificate from the cache.
-func (s tlsSniSolver) CleanUp(domain, token, keyAuth string) error {
+func (s tlsSNISolver) CleanUp(domain, token, keyAuth string) error {
 	_, acmeDomain, err := acme.TLSSNI01ChallengeCert(keyAuth)
 	if err != nil {
 		return err
 	}
-	uncacheCertificate(acmeDomain)
+	s.certCache.Lock()
+	delete(s.certCache.cache, acmeDomain)
+	s.certCache.Unlock()
 	return nil
 }
 

controller.go

@@ -103,6 +103,20 @@ func (c *Controller) Context() Context {
 	return c.instance.context
 }
 
+// Get safely gets a value from the Instance's storage.
+func (c *Controller) Get(key interface{}) interface{} {
+	c.instance.StorageMu.RLock()
+	defer c.instance.StorageMu.RUnlock()
+	return c.instance.Storage[key]
+}
+
+// Set safely sets a value on the Instance's storage.
+func (c *Controller) Set(key, val interface{}) {
+	c.instance.StorageMu.Lock()
+	c.instance.Storage[key] = val
+	c.instance.StorageMu.Unlock()
+}
+
 // NewTestController creates a new Controller for
 // the server type and input specified. The filename
 // is "Testfile". If the server type is not empty and
@@ -113,12 +127,12 @@ func (c *Controller) Context() Context {
 // Used only for testing, but exported so plugins can
 // use this for convenience.
 func NewTestController(serverType, input string) *Controller {
-	var ctx Context
+	testInst := &Instance{serverType: serverType, Storage: make(map[interface{}]interface{})}
 	if stype, err := getServerType(serverType); err == nil {
-		ctx = stype.NewContext()
+		testInst.context = stype.NewContext(testInst)
 	}
 	return &Controller{
-		instance:           &Instance{serverType: serverType, context: ctx},
+		instance:           testInst,
 		Dispenser:          caddyfile.NewDispenser("Testfile", strings.NewReader(input)),
 		OncePerServerBlock: func(f func() error) error { return f() },
 	}

plugins.go

@@ -195,7 +195,7 @@ type ServerType struct {
 	// startup phases before this one. It's a way to keep
 	// each set of server instances separate and to reduce
 	// the amount of global state you need.
-	NewContext func() Context
+	NewContext func(inst *Instance) Context
 }
 
 // Plugin is a type which holds information about a plugin.
@@ -387,6 +387,14 @@ func loadCaddyfileInput(serverType string) (Input, error) {
 	return caddyfileToUse, nil
 }
 
+// OnProcessExit is a list of functions to run when the process
+// exits -- they are ONLY for cleanup and should not block,
+// return errors, or do anything fancy. They will be run with
+// every signal, even if "shutdown callbacks" are not executed.
+// This variable must only be modified in the main goroutine
+// from init() functions.
+var OnProcessExit []func()
+
 // caddyfileLoader pairs the name of a loader to the loader.
 type caddyfileLoader struct {
 	name   string

sigtrap.go

@@ -44,16 +44,17 @@ func trapSignalsCrossPlatform() {
 
 			if i > 0 {
 				log.Println("[INFO] SIGINT: Force quit")
-				if PidFile != "" {
-					os.Remove(PidFile)
+				for _, f := range OnProcessExit {
+					f() // important cleanup actions only
 				}
 				os.Exit(2)
 			}
 
 			log.Println("[INFO] SIGINT: Shutting down")
 
-			if PidFile != "" {
-				os.Remove(PidFile)
+			// important cleanup actions before shutdown callbacks
+			for _, f := range OnProcessExit {
+				f()
 			}
 
 			go func() {

sigtrap_posix.go

@@ -33,22 +33,22 @@ func trapSignalsPosix() {
 			switch sig {
 			case syscall.SIGQUIT:
 				log.Println("[INFO] SIGQUIT: Quitting process immediately")
-				if PidFile != "" {
-					os.Remove(PidFile)
+				for _, f := range OnProcessExit {
+					f() // only perform important cleanup actions
 				}
 				os.Exit(0)
 
 			case syscall.SIGTERM:
 				log.Println("[INFO] SIGTERM: Shutting down servers then terminating")
 				exitCode := executeShutdownCallbacks("SIGTERM")
+				for _, f := range OnProcessExit {
+					f() // only perform important cleanup actions
+				}
 				err := Stop()
 				if err != nil {
 					log.Printf("[ERROR] SIGTERM stop: %v", err)
 					exitCode = 3
 				}
-				if PidFile != "" {
-					os.Remove(PidFile)
-				}
 				os.Exit(exitCode)
 
 			case syscall.SIGUSR1: