state: apply default node key expiry on registration

Use the node.expiry config to apply a default expiry to non-tagged
nodes when the client does not request a specific expiry. This covers
all registration paths: new node creation, re-authentication, and
pre-auth key re-registration.

Tagged nodes remain exempt and never expire.

Fixes #1711

hscontrol/state/state.go

@@ -1431,6 +1431,17 @@ func (s *State) applyAuthNodeUpdate(params authNodeUpdateParams) (types.NodeView
 			}
 		}
 		// Tagged → Tagged: keep existing expiry (nil) - no action needed
+
+		// Apply default node expiry for non-tagged nodes when the
+		// resolved expiry is still nil or zero (e.g., CLI registration
+		// where the client did not request a specific expiry).
+		needsDefaultExpiry := !node.IsTagged() &&
+			(node.Expiry == nil || node.Expiry.IsZero()) &&
+			s.cfg.Node.Expiry > 0
+		if needsDefaultExpiry {
+			exp := time.Now().Add(s.cfg.Node.Expiry)
+			node.Expiry = &exp
+		}
 	})
 
 	if !ok {
@@ -1553,6 +1564,17 @@ func (s *State) createAndSaveNewNode(params newNodeParams) (types.NodeView, erro
 		}
 	}
 
+	// Apply default node expiry for non-tagged nodes when the client
+	// did not request a specific expiry.
+	// Tagged nodes are exempt — they never expire.
+	needsDefaultExpiry := !nodeToRegister.IsTagged() &&
+		(nodeToRegister.Expiry == nil || nodeToRegister.Expiry.IsZero()) &&
+		s.cfg.Node.Expiry > 0
+	if needsDefaultExpiry {
+		exp := time.Now().Add(s.cfg.Node.Expiry)
+		nodeToRegister.Expiry = &exp
+	}
+
 	// Validate before saving
 	err := validateNodeOwnership(&nodeToRegister)
 	if err != nil {
@@ -2030,9 +2052,18 @@ func (s *State) HandleNodeFromPreAuthKey(
 			node.LastSeen = new(time.Now())
 
 			// Tagged nodes keep their existing expiry (disabled).
-			// User-owned nodes update expiry from the client request.
+			// User-owned nodes update expiry from the client request,
+			// falling back to the configured default if the client
+			// did not request a specific expiry.
 			if !node.IsTagged() {
-				node.Expiry = &regReq.Expiry
+				if !regReq.Expiry.IsZero() {
+					node.Expiry = &regReq.Expiry
+				} else if s.cfg.Node.Expiry > 0 {
+					exp := time.Now().Add(s.cfg.Node.Expiry)
+					node.Expiry = &exp
+				} else {
+					node.Expiry = &regReq.Expiry
+				}
 			}
 		})
 

integration/auth_oidc_test.go

@@ -1354,7 +1354,7 @@ func TestOIDCExpiryAfterRestart(t *testing.T) {
 		"HEADSCALE_OIDC_CLIENT_ID":          scenario.mockOIDC.ClientID(),
 		"CREDENTIALS_DIRECTORY_TEST":        "/tmp",
 		"HEADSCALE_OIDC_CLIENT_SECRET_PATH": "${CREDENTIALS_DIRECTORY_TEST}/hs_client_oidc_secret",
-		"HEADSCALE_OIDC_EXPIRY":             "72h",
+		"HEADSCALE_NODE_EXPIRY":             "72h",
 	}
 
 	err = scenario.CreateHeadscaleEnvWithLoginURL(

integration/cli_test.go

@@ -1394,11 +1394,12 @@ func TestNodeExpireCommand(t *testing.T) {
 
 	assert.Len(t, listAll, 5)
 
-	assert.True(t, listAll[0].GetExpiry().AsTime().IsZero())
-	assert.True(t, listAll[1].GetExpiry().AsTime().IsZero())
-	assert.True(t, listAll[2].GetExpiry().AsTime().IsZero())
-	assert.True(t, listAll[3].GetExpiry().AsTime().IsZero())
-	assert.True(t, listAll[4].GetExpiry().AsTime().IsZero())
+	// With node.expiry defaulting to 0, non-tagged nodes have zero expiry
+	// (never expire unless explicitly expired).
+	for i := range 5 {
+		assert.True(t, listAll[i].GetExpiry().AsTime().IsZero(),
+			"node %d should have zero expiry (no default node.expiry)", i)
+	}
 
 	for idx := range 3 {
 		_, err := headscale.Execute(