API: Add authorization hook (v2)

internal/state/hooks.go

@@ -2,6 +2,8 @@ package state
 
 import (
 	"context"
+	"crypto/x509"
+	"net/http"
 
 	"github.com/canonical/microcluster/v2/rest/types"
 )
@@ -45,4 +47,12 @@ type Hooks struct {
 
 	// OnDaemonConfigUpdate is a post-action hook that is run on all cluster members when any cluster member receives a local configuration update.
 	OnDaemonConfigUpdate func(ctx context.Context, s State, config types.DaemonConfig) error
+
+	// OnAuthenticate is run when an incoming HTTP request needs to be authenticated.
+	// If defined it is used as a replacement for the regular mTLS check.
+	// trustedCerts contains the certs from the truststore.
+	// Returning true indicates that the request is trusted.
+	// Returning false indicates that the request is not trusted.
+	// Returning an error is optional but will always result in a forbidden request.
+	OnAuthenticate func(ctx context.Context, s State, r *http.Request, trustedCerts map[string]x509.Certificate) (bool, error)
 }

microcluster/app.go

@@ -112,7 +112,7 @@ func (m *MicroCluster) Status(ctx context.Context) (*internalTypes.Server, error
 // Ready waits for the daemon to report it has finished initial setup and is ready to be bootstrapped or join an
 // existing cluster.
 func (m *MicroCluster) Ready(ctx context.Context) error {
-	finger := make(chan error, 1)
+	finger := make(chan struct{}, 1)
 	var errLast error
 	go func() {
 		for i := 0; ; i++ {
@@ -156,7 +156,7 @@ func (m *MicroCluster) Ready(ctx context.Context) error {
 				continue
 			}
 
-			finger <- nil
+			finger <- struct{}{}
 			return
 		}
 	}()

rest/access/handlers.go

@@ -79,6 +79,10 @@ func Authenticate(state state.State, r *http.Request, hostAddress string, truste
 
 	switch r.Host {
 	case hostAddrPort.WithZone("").String():
+		if intState.Hooks != nil && intState.Hooks.OnAuthenticate != nil {
+			return intState.Hooks.OnAuthenticate(r.Context(), intState, r, trustedCerts)
+		}
+
 		if r.TLS != nil {
 			for _, cert := range r.TLS.PeerCertificates {
 				trusted, fingerprint := util.CheckMutualTLS(*cert, trustedCerts)