Prevent duplicate service registration (#32050)

Enterprise tests do not always set the enterprise build type which
causes test failures due to duplicate service registration. To
prevent every test from needing to update the modules the PluginRegistry
was modified to expose a mechanism to detect if a plugin is registered
or not. The old check that registered a not implemented LoginRuleService
now makes use of this mechanism to verify that the enterprise auth
plugin is not registered.

lib/auth/grpcserver.go

@@ -71,7 +71,6 @@ import (
 	"github.com/gravitational/teleport/lib/events"
 	"github.com/gravitational/teleport/lib/httplib"
 	"github.com/gravitational/teleport/lib/joinserver"
-	"github.com/gravitational/teleport/lib/modules"
 	"github.com/gravitational/teleport/lib/observability/metrics"
 	"github.com/gravitational/teleport/lib/services"
 	"github.com/gravitational/teleport/lib/services/local"
@@ -5378,7 +5377,7 @@ func NewGRPCServer(cfg GRPCServerConfig) (*GRPCServer, error) {
 	// Only register the service if this is an open source build. Enterprise builds
 	// register the actual service via an auth plugin, if we register here then all
 	// Enterprise builds would fail with a duplicate service registered error.
-	if modules.GetModules().BuildType() == modules.BuildOSS {
+	if cfg.PluginRegistry == nil || !cfg.PluginRegistry.IsRegistered("auth.enterprise") {
 		loginrulepb.RegisterLoginRuleServiceServer(server, loginrule.NotImplementedService{})
 	}
 

lib/plugin/registry.go

@@ -32,13 +32,15 @@ type Plugin interface {
 
 // Registry is the plugin registry
 type Registry interface {
+	// IsRegistered returns whether a plugin with the give name exists.
+	IsRegistered(name string) bool
 	// Add adds plugin to the registry
 	Add(plugin Plugin) error
 	// RegisterProxyWebHandlers registers Teleport Proxy web handlers
-	RegisterProxyWebHandlers(hander interface{}) error
+	RegisterProxyWebHandlers(handler interface{}) error
 	// RegisterAuthWebHandlers registers Teleport Auth web handlers
 	RegisterAuthWebHandlers(handler interface{}) error
-	// RegisterAuthServices registerse Teleport AuthServer services
+	// RegisterAuthServices registers Teleport AuthServer services
 	RegisterAuthServices(server interface{}) error
 }
 
@@ -53,6 +55,12 @@ type registry struct {
 	plugins map[string]Plugin
 }
 
+// IsRegistered returns whether a plugin with the give name exists.
+func (r *registry) IsRegistered(name string) bool {
+	_, ok := r.plugins[name]
+	return ok
+}
+
 // Add adds plugin to the plugin registry
 func (r *registry) Add(p Plugin) error {
 	if p == nil {
@@ -64,8 +72,7 @@ func (r *registry) Add(p Plugin) error {
 		return trace.BadParameter("missing plugin name")
 	}
 
-	_, exists := r.plugins[name]
-	if exists {
+	if r.IsRegistered(name) {
 		return trace.AlreadyExists("plugin %v already exists", name)
 	}
 
@@ -96,7 +103,7 @@ func (r *registry) RegisterAuthWebHandlers(handler interface{}) error {
 	return nil
 }
 
-// RegisterAuthServices registerse Teleport AuthServer services
+// RegisterAuthServices registers Teleport AuthServer services
 func (r *registry) RegisterAuthServices(server interface{}) error {
 	for _, p := range r.plugins {
 		if err := p.RegisterAuthServices(server); err != nil {