acmeserver: Support custom CAs from Caddyfile

The HTTP Caddyfile adapter can now configure the PKI app, and the acme_server directive can now be used to specify a custom CA used for issuing certificates. More customization options can follow later as needed.

modules/caddypki/acmeserver/caddyfile.go

@@ -16,23 +16,58 @@ package acmeserver
 
 import (
 	"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
-	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
+	"github.com/caddyserver/caddy/v2/modules/caddypki"
 )
 
 func init() {
-	httpcaddyfile.RegisterHandlerDirective("acme_server", parseACMEServer)
+	httpcaddyfile.RegisterDirective("acme_server", parseACMEServer)
 }
 
 // parseACMEServer sets up an ACME server handler from Caddyfile tokens.
 //
-//     acme_server [<matcher>]
+//     acme_server [<matcher>] {
+//         ca <id>
+//     }
 //
-func parseACMEServer(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error) {
-	var as Handler
+func parseACMEServer(h httpcaddyfile.Helper) ([]httpcaddyfile.ConfigValue, error) {
+	if !h.Next() {
+		return nil, h.ArgErr()
+	}
+
+	matcherSet, err := h.ExtractMatcherSet()
+	if err != nil {
+		return nil, err
+	}
+
+	var acmeServer Handler
+	var ca *caddypki.CA
+
 	for h.Next() {
 		if h.NextArg() {
 			return nil, h.ArgErr()
 		}
+		for h.NextBlock(0) {
+			switch h.Val() {
+			case "ca":
+				if !h.AllArgs(&acmeServer.CA) {
+					return nil, h.ArgErr()
+				}
+				if ca == nil {
+					ca = new(caddypki.CA)
+				}
+				ca.ID = acmeServer.CA
+			}
+		}
 	}
-	return as, nil
+
+	configVals := h.NewRoute(matcherSet, acmeServer)
+
+	if ca == nil {
+		return configVals, nil
+	}
+
+	return append(configVals, httpcaddyfile.ConfigValue{
+		Class: "pki.ca",
+		Value: ca,
+	}), nil
 }

modules/caddypki/ca.go

@@ -63,7 +63,12 @@ type CA struct {
 	// separate location from your leaf certificates.
 	StorageRaw json.RawMessage `json:"storage,omitempty" caddy:"namespace=caddy.storage inline_key=module"`
 
-	id          string
+	// The unique config-facing ID of the certificate authority.
+	// Since the ID is set in JSON config via object key, this
+	// field is exported only for purposes of config generation
+	// and module provisioning.
+	ID string `json:"-"`
+
 	storage     certmagic.Storage
 	root, inter *x509.Certificate
 	interKey    interface{} // TODO: should we just store these as crypto.Signer?
@@ -82,7 +87,7 @@ func (ca *CA) Provision(ctx caddy.Context, id string, log *zap.Logger) error {
 		return fmt.Errorf("CA ID is required (use 'local' for the default CA)")
 	}
 	ca.mu.Lock()
-	ca.id = id
+	ca.ID = id
 	ca.mu.Unlock()
 
 	if ca.StorageRaw != nil {
@@ -142,11 +147,6 @@ func (ca *CA) Provision(ctx caddy.Context, id string, log *zap.Logger) error {
 	return nil
 }
 
-// ID returns the CA's ID, as given by the user in the config.
-func (ca CA) ID() string {
-	return ca.id
-}
-
 // RootCertificate returns the CA's root certificate (public key).
 func (ca CA) RootCertificate() *x509.Certificate {
 	ca.mu.RLock()
@@ -338,7 +338,7 @@ func (ca CA) genIntermediate(rootCert *x509.Certificate, rootKey interface{}) (i
 }
 
 func (ca CA) storageKeyCAPrefix() string {
-	return path.Join("pki", "authorities", certmagic.StorageKeys.Safe(ca.id))
+	return path.Join("pki", "authorities", certmagic.StorageKeys.Safe(ca.ID))
 }
 func (ca CA) storageKeyRootCert() string {
 	return path.Join(ca.storageKeyCAPrefix(), "root.crt")

modules/caddypki/maintain.go

@@ -50,7 +50,7 @@ func (p *PKI) renewCerts() {
 		if err != nil {
 			p.log.Error("renewing intermediate certificates",
 				zap.Error(err),
-				zap.String("ca", ca.id))
+				zap.String("ca", ca.ID))
 		}
 	}
 }
@@ -59,7 +59,7 @@ func (p *PKI) renewCertsForCA(ca *CA) error {
 	ca.mu.Lock()
 	defer ca.mu.Unlock()
 
-	log := p.log.With(zap.String("ca", ca.id))
+	log := p.log.With(zap.String("ca", ca.ID))
 
 	// only maintain the root if it's not manually provided in the config
 	if ca.Root == nil {

modules/caddypki/pki.go

@@ -49,10 +49,14 @@ func (p *PKI) Provision(ctx caddy.Context) error {
 	p.ctx = ctx
 	p.log = ctx.Logger(p)
 
-	// if this app is initialized at all, ensure there's
-	// at least a default CA that can be used
-	if len(p.CAs) == 0 {
-		p.CAs = map[string]*CA{DefaultCAID: new(CA)}
+	// if this app is initialized at all, ensure there's at
+	// least a default CA that can be used: the standard CA
+	// which is used implicitly for signing local-use certs
+	if p.CAs == nil {
+		p.CAs = make(map[string]*CA)
+	}
+	if _, ok := p.CAs[DefaultCAID]; !ok {
+		p.CAs[DefaultCAID] = new(CA)
 	}
 
 	for caID, ca := range p.CAs {