caddytls: Reuse certificate cache through reloads (#5623)

* caddytls: Don't purge cert cache on config reload

* Update CertMagic

This actually avoids reloading managed certs from storage
when already in the cache, d'oh.

* Fix bug; re-implement HasCertificateForSubject

* Update go.mod: CertMagic tag

10 files changed, 115 insertions, 38 deletions

diff --git a/admin.go b/admin.go
index 59b3dcd..3ea5051 100644
--- a/admin.go
+++ b/admin.go
@@ -1018,7 +1018,7 @@ func handleConfigID(w http.ResponseWriter, r *http.Request) error {
 	// map the ID to the expanded path
 	currentCtxMu.RLock()
 	expanded, ok := rawCfgIndex[id]
-	defer currentCtxMu.RUnlock()
+	currentCtxMu.RUnlock()
 	if !ok {
 		return APIError{
 			HTTPStatus: http.StatusNotFound,
diff --git a/caddy.go b/caddy.go
index 84cfc11..dcaa86b 100644
--- a/caddy.go
+++ b/caddy.go
@@ -959,8 +959,9 @@ func Version() (simple, full string) {
 // This function is experimental and might be changed
 // or removed in the future.
 func ActiveContext() Context {
-	currentCtxMu.RLock()
-	defer currentCtxMu.RUnlock()
+	// TODO: This locking might still be needed; more investigation is required (deadlock during Cleanup for the caddytls.TLS module).
+	// currentCtxMu.RLock()
+	// defer currentCtxMu.RUnlock()
 	return currentCtx
 }
 
diff --git a/context.go b/context.go
index 615192c..004dee6 100644
--- a/context.go
+++ b/context.go
@@ -410,6 +410,11 @@ func (ctx Context) loadModuleInline(moduleNameKey, moduleScope string, raw json.
 // called during the Provision/Validate phase to reference a
 // module's own host app (since the parent app module is still
 // in the process of being provisioned, it is not yet ready).
+//
+// We return any type instead of the App type because it is NOT
+// intended for the caller of this method to be the one to start
+// or stop App modules. The caller is expected to assert to the
+// concrete type.
 func (ctx Context) App(name string) (any, error) {
 	if app, ok := ctx.cfg.apps[name]; ok {
 		return app, nil
@@ -428,18 +433,15 @@ func (ctx Context) App(name string) (any, error) {
 
 // AppIfConfigured returns an app by its name if it has been
 // configured. Can be called instead of App() to avoid
-// instantiating an empty app when that's not desirable.
-func (ctx Context) AppIfConfigured(name string) (any, error) {
-	app, ok := ctx.cfg.apps[name]
-	if !ok || app == nil {
-		return nil, nil
-	}
-
-	appModule, err := ctx.App(name)
-	if err != nil {
-		return nil, err
-	}
-	return appModule, nil
+// instantiating an empty app when that's not desirable. If
+// the app has not been loaded, nil is returned.
+//
+// We return any type instead of the App type because it is not
+// intended for the caller of this method to be the one to start
+// or stop App modules. The caller is expected to assert to the
+// concrete type.
+func (ctx Context) AppIfConfigured(name string) any {
+	return ctx.cfg.apps[name]
 }
 
 // Storage returns the configured Caddy storage implementation.
diff --git a/go.mod b/go.mod
index 332a65d..53b6c8c 100644
--- a/go.mod
+++ b/go.mod
@@ -7,7 +7,7 @@ require (
 	github.com/Masterminds/sprig/v3 v3.2.3
 	github.com/alecthomas/chroma/v2 v2.7.0
 	github.com/aryann/difflib v0.0.0-20210328193216-ff5ff6dc229b
-	github.com/caddyserver/certmagic v0.18.2
+	github.com/caddyserver/certmagic v0.19.0
 	github.com/dustin/go-humanize v1.0.1
 	github.com/go-chi/chi v4.1.2+incompatible
 	github.com/google/cel-go v0.15.1
@@ -61,6 +61,7 @@ require (
 	github.com/quic-go/qtls-go1-20 v0.2.2 // indirect
 	github.com/smallstep/go-attestation v0.4.4-0.20230509120429-e17291421738 // indirect
 	github.com/x448/float16 v0.8.4 // indirect
+	github.com/zeebo/blake3 v0.2.3 // indirect
 	go.opentelemetry.io/contrib/propagators/aws v1.17.0 // indirect
 	go.opentelemetry.io/contrib/propagators/b3 v1.17.0 // indirect
 	go.opentelemetry.io/contrib/propagators/jaeger v1.17.0 // indirect
diff --git a/go.sum b/go.sum
index 8e92c4a..69a01d8 100644
--- a/go.sum
+++ b/go.sum
@@ -170,8 +170,8 @@ github.com/bketelsen/crypt v0.0.3-0.20200106085610-5cbc8cc4026c/go.mod h1:MKsuJm
 github.com/blakesmith/ar v0.0.0-20190502131153-809d4375e1fb/go.mod h1:PkYb9DJNAwrSvRx5DYA+gUcOIgTGVMNkfSCbZM8cWpI=
 github.com/boltdb/bolt v1.3.1/go.mod h1:clJnj/oiGkjum5o1McbSZDSLxVThjynRyGBgiAx27Ps=
 github.com/caarlos0/ctrlc v1.0.0/go.mod h1:CdXpj4rmq0q/1Eb44M9zi2nKB0QraNKuRGYGrrHhcQw=
-github.com/caddyserver/certmagic v0.18.2 h1:Nj2+M+A2Ho9IF6n1wUSbra4mX1X6ALzWpul9HooprHA=
-github.com/caddyserver/certmagic v0.18.2/go.mod h1:cLsgYXecH1iVUPjDXw15/1SKjZk/TK+aFfQk5FnugGQ=
+github.com/caddyserver/certmagic v0.19.0 h1:HuJ1Yf1H1jAfmBGrSSQN1XRkafnWcpDtyIiyMV6vmpM=
+github.com/caddyserver/certmagic v0.19.0/go.mod h1:fsL01NomQ6N+kE2j37ZCnig2MFosG+MIO4ztnmG/zz8=
 github.com/campoy/unique v0.0.0-20180121183637-88950e537e7e/go.mod h1:9IOqJGCPMSc6E5ydlp5NIonxObaeu/Iub/X03EKPVYo=
 github.com/casbin/casbin/v2 v2.1.2/go.mod h1:YcPU1XXisHhLzuxH9coDNf2FbKpjGlbCg3n9yuLkIJQ=
 github.com/cavaliercoder/go-cpio v0.0.0-20180626203310-925f9528c45e/go.mod h1:oDpT4efm8tSYHXV5tHSdRvBet/b/QzxZ+XyyPehvm3A=
@@ -650,6 +650,7 @@ github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+o
 github.com/klauspost/compress v1.12.3/go.mod h1:8dP1Hq4DHOhN9w426knH3Rhby4rFm6D8eO+e+Dq5Gzg=
 github.com/klauspost/compress v1.16.6 h1:91SKEy4K37vkp255cJ8QesJhjyRO0hn9i9G0GoUwLsk=
 github.com/klauspost/compress v1.16.6/go.mod h1:ntbaceVETuRiXiv4DpjP66DpAtAGkEQskQzEyD//IeE=
+github.com/klauspost/cpuid/v2 v2.0.12/go.mod h1:g2LTdtYhdyuGPqyWyv7qRAmj1WBqxuObKfj5c0PQa7c=
 github.com/klauspost/cpuid/v2 v2.2.5 h1:0E5MSMDEoAulmXNFquVs//DdoomxaoTY1kUhbc/qbZg=
 github.com/klauspost/cpuid/v2 v2.2.5/go.mod h1:Lcz8mBdAVJIBVzewtcLocK12l3Y+JytZYpaMropDUws=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
@@ -1012,6 +1013,12 @@ github.com/yuin/goldmark v1.5.4 h1:2uY/xC0roWy8IBEGLgB1ywIoEJFGmRrX21YQcvGZzjU=
 github.com/yuin/goldmark v1.5.4/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 github.com/yuin/goldmark-highlighting/v2 v2.0.0-20220924101305-151362477c87 h1:Py16JEzkSdKAtEFJjiaYLYBOWGXc1r/xHj/Q/5lA37k=
 github.com/yuin/goldmark-highlighting/v2 v2.0.0-20220924101305-151362477c87/go.mod h1:ovIvrum6DQJA4QsJSovrkC4saKHQVs7TvcaeO8AIl5I=
+github.com/zeebo/assert v1.1.0 h1:hU1L1vLTHsnO8x8c9KAR5GmM5QscxHg5RNU5z5qbUWY=
+github.com/zeebo/assert v1.1.0/go.mod h1:Pq9JiuJQpG8JLJdtkwrJESF0Foym2/D9XMU5ciN/wJ0=
+github.com/zeebo/blake3 v0.2.3 h1:TFoLXsjeXqRNFxSbk35Dk4YtszE/MQQGK10BH4ptoTg=
+github.com/zeebo/blake3 v0.2.3/go.mod h1:mjJjZpnsyIVtVgTOSpJ9vmRE4wgDeyt2HU3qXvvKCaQ=
+github.com/zeebo/pcg v1.0.1 h1:lyqfGeWiv4ahac6ttHs+I5hwtH/+1mrhlCtVNQM2kHo=
+github.com/zeebo/pcg v1.0.1/go.mod h1:09F0S9iiKrwn9rlI5yjLkmrug154/YRW6KnnXVDM/l4=
 github.com/zenazn/goji v0.9.0/go.mod h1:7S9M489iMyHBNxwZnk9/EHS098H4/F6TATF2mIxtB1Q=
 go.etcd.io/bbolt v1.3.2/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
 go.etcd.io/bbolt v1.3.3/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
diff --git a/modules/caddyhttp/autohttps.go b/modules/caddyhttp/autohttps.go
index 4ade3c5..39ec135 100644
--- a/modules/caddyhttp/autohttps.go
+++ b/modules/caddyhttp/autohttps.go
@@ -196,8 +196,7 @@ func (app *App) automaticHTTPSPhase1(ctx caddy.Context, repl *caddy.Replacer) er
 					// if a certificate for this name is already loaded,
 					// don't obtain another one for it, unless we are
 					// supposed to ignore loaded certificates
-					if !srv.AutoHTTPS.IgnoreLoadedCerts &&
-						len(app.tlsApp.AllMatchingCertificates(d)) > 0 {
+					if !srv.AutoHTTPS.IgnoreLoadedCerts && app.tlsApp.HasCertificateForSubject(d) {
 						logger.Info("skipping automatic certificate management because one or more matching certificates are already loaded",
 							zap.String("domain", d),
 							zap.String("server_name", srvName),
diff --git a/modules/caddyhttp/reverseproxy/httptransport.go b/modules/caddyhttp/reverseproxy/httptransport.go
index 1135862..8334f25 100644
--- a/modules/caddyhttp/reverseproxy/httptransport.go
+++ b/modules/caddyhttp/reverseproxy/httptransport.go
@@ -525,7 +525,7 @@ func (t TLSConfig) MakeTLSClientConfig(ctx caddy.Context) (*tls.Config, error) {
 			return nil, fmt.Errorf("managing client certificate: %v", err)
 		}
 		cfg.GetClientCertificate = func(cri *tls.CertificateRequestInfo) (*tls.Certificate, error) {
-			certs := tlsApp.AllMatchingCertificates(t.ClientCertificateAutomate)
+			certs := caddytls.AllMatchingCertificates(t.ClientCertificateAutomate)
 			var err error
 			for _, cert := range certs {
 				err = cri.SupportsCertificate(&cert.Certificate)
diff --git a/modules/caddypki/adminapi.go b/modules/caddypki/adminapi.go
index cab7c70..24371e7 100644
--- a/modules/caddypki/adminapi.go
+++ b/modules/caddypki/adminapi.go
@@ -50,11 +50,7 @@ func (a *adminAPI) Provision(ctx caddy.Context) error {
 	a.log = ctx.Logger(a) // TODO: passing in 'a' is a hack until the admin API is officially extensible (see #5032)
 
 	// Avoid initializing PKI if it wasn't configured
-	pkiApp, err := a.ctx.AppIfConfigured("pki")
-	if err != nil {
-		return err
-	}
-	if pkiApp != nil {
+	if pkiApp := a.ctx.AppIfConfigured("pki"); pkiApp != nil {
 		a.pkiApp = pkiApp.(*PKI)
 	}
 
diff --git a/modules/caddytls/automation.go b/modules/caddytls/automation.go
index de88201..114d7aa 100644
--- a/modules/caddytls/automation.go
+++ b/modules/caddytls/automation.go
@@ -294,7 +294,9 @@ func (ap *AutomationPolicy) Provision(tlsApp *TLS) error {
 		Issuers: issuers,
 		Logger:  tlsApp.logger,
 	}
-	ap.magic = certmagic.New(tlsApp.certCache, template)
+	certCacheMu.RLock()
+	ap.magic = certmagic.New(certCache, template)
+	certCacheMu.RUnlock()
 
 	// sometimes issuers may need the parent certmagic.Config in
 	// order to function properly (for example, ACMEIssuer needs
diff --git a/modules/caddytls/tls.go b/modules/caddytls/tls.go
index 52f1159..1456d29 100644
--- a/modules/caddytls/tls.go
+++ b/modules/caddytls/tls.go
@@ -36,6 +36,11 @@ func init() {
 	caddy.RegisterModule(AutomateLoader{})
 }
 
+var (
+	certCache   *certmagic.Cache
+	certCacheMu sync.RWMutex
+)
+
 // TLS provides TLS facilities including certificate
 // loading and management, client auth, and more.
 type TLS struct {
@@ -77,12 +82,15 @@ type TLS struct {
 
 	certificateLoaders []CertificateLoader
 	automateNames      []string
-	certCache          *certmagic.Cache
 	ctx                caddy.Context
 	storageCleanTicker *time.Ticker
 	storageCleanStop   chan struct{}
 	logger             *zap.Logger
 	events             *caddyevents.App
+
+	// set of subjects with managed certificates,
+	// and hashes of manually-loaded certificates
+	managing, loaded map[string]struct{}
 }
 
 // CaddyModule returns the Caddy module information.
@@ -103,6 +111,7 @@ func (t *TLS) Provision(ctx caddy.Context) error {
 	t.ctx = ctx
 	t.logger = ctx.Logger()
 	repl := caddy.NewReplacer()
+	t.managing, t.loaded = make(map[string]struct{}), make(map[string]struct{})
 
 	// set up a new certificate cache; this (re)loads all certificates
 	cacheOpts := certmagic.CacheOptions{
@@ -121,7 +130,14 @@ func (t *TLS) Provision(ctx caddy.Context) error {
 	if cacheOpts.Capacity <= 0 {
 		cacheOpts.Capacity = 10000
 	}
-	t.certCache = certmagic.NewCache(cacheOpts)
+
+	certCacheMu.Lock()
+	if certCache == nil {
+		certCache = certmagic.NewCache(cacheOpts)
+	} else {
+		certCache.SetOptions(cacheOpts)
+	}
+	certCacheMu.Unlock()
 
 	// certificate loaders
 	val, err := ctx.LoadModule(t, "CertificatesRaw")
@@ -209,7 +225,8 @@ func (t *TLS) Provision(ctx caddy.Context) error {
 	// provision so that other apps (such as http) can know which
 	// certificates have been manually loaded, and also so that
 	// commands like validate can be a better test
-	magic := certmagic.New(t.certCache, certmagic.Config{
+	certCacheMu.RLock()
+	magic := certmagic.New(certCache, certmagic.Config{
 		Storage: ctx.Storage(),
 		Logger:  t.logger,
 		OnEvent: t.onEvent,
@@ -217,16 +234,18 @@ func (t *TLS) Provision(ctx caddy.Context) error {
 			DisableStapling: t.DisableOCSPStapling,
 		},
 	})
+	certCacheMu.RUnlock()
 	for _, loader := range t.certificateLoaders {
 		certs, err := loader.LoadCertificates()
 		if err != nil {
 			return fmt.Errorf("loading certificates: %v", err)
 		}
 		for _, cert := range certs {
-			err := magic.CacheUnmanagedTLSCertificate(ctx, cert.Certificate, cert.Tags)
+			hash, err := magic.CacheUnmanagedTLSCertificate(ctx, cert.Certificate, cert.Tags)
 			if err != nil {
 				return fmt.Errorf("caching unmanaged certificate: %v", err)
 			}
+			t.loaded[hash] = struct{}{}
 		}
 	}
 
@@ -305,16 +324,44 @@ func (t *TLS) Stop() error {
 
 // Cleanup frees up resources allocated during Provision.
 func (t *TLS) Cleanup() error {
-	// stop the certificate cache
-	if t.certCache != nil {
-		t.certCache.Stop()
-	}
-
 	// stop the session ticket rotation goroutine
 	if t.SessionTickets != nil {
 		t.SessionTickets.stop()
 	}
 
+	// if a new TLS app was loaded, remove certificates from the cache that are no longer
+	// being managed or loaded by the new config; if there is no more TLS app running,
+	// then stop cert maintenance and let the cert cache be GC'ed
+	if nextTLS := caddy.ActiveContext().AppIfConfigured("tls"); nextTLS != nil {
+		nextTLSApp := nextTLS.(*TLS)
+
+		// compute which certificates were managed or loaded into the cert cache by this
+		// app instance (which is being stopped) that are not managed or loaded by the
+		// new app instance (which just started), and remove them from the cache
+		var noLongerManaged, noLongerLoaded []string
+		for subj := range t.managing {
+			if _, ok := nextTLSApp.managing[subj]; !ok {
+				noLongerManaged = append(noLongerManaged, subj)
+			}
+		}
+		for hash := range t.loaded {
+			if _, ok := nextTLSApp.loaded[hash]; !ok {
+				noLongerLoaded = append(noLongerLoaded, hash)
+			}
+		}
+
+		certCacheMu.RLock()
+		certCache.RemoveManaged(noLongerManaged)
+		certCache.Remove(noLongerLoaded)
+		certCacheMu.RUnlock()
+	} else {
+		// no more TLS app running, so delete in-memory cert cache
+		certCache.Stop()
+		certCacheMu.Lock()
+		certCache = nil
+		certCacheMu.Unlock()
+	}
+
 	return nil
 }
 
@@ -339,6 +386,9 @@ func (t *TLS) Manage(names []string) error {
 		if err != nil {
 			return fmt.Errorf("automate: manage %v: %v", names, err)
 		}
+		for _, name := range names {
+			t.managing[name] = struct{}{}
+		}
 	}
 
 	return nil
@@ -449,8 +499,27 @@ func (t *TLS) getAutomationPolicyForName(name string) *AutomationPolicy {
 
 // AllMatchingCertificates returns the list of all certificates in
 // the cache which could be used to satisfy the given SAN.
-func (t *TLS) AllMatchingCertificates(san string) []certmagic.Certificate {
-	return t.certCache.AllMatchingCertificates(san)
+func AllMatchingCertificates(san string) []certmagic.Certificate {
+	return certCache.AllMatchingCertificates(san)
+}
+
+func (t *TLS) HasCertificateForSubject(subject string) bool {
+	certCacheMu.RLock()
+	allMatchingCerts := certCache.AllMatchingCertificates(subject)
+	certCacheMu.RUnlock()
+	for _, cert := range allMatchingCerts {
+		// check if the cert is manually loaded by this config
+		if _, ok := t.loaded[cert.Hash()]; ok {
+			return true
+		}
+		// check if the cert is automatically managed by this config
+		for _, name := range cert.Names {
+			if _, ok := t.managing[name]; ok {
+				return true
+			}
+		}
+	}
+	return false
 }
 
 // keepStorageClean starts a goroutine that immediately cleans up all