feat: Disable auto-enroll via environment variable

lib/devicetrust/enroll/auto_enroll.go

@@ -20,12 +20,21 @@ package enroll
 
 import (
  "context"
+ "errors"
+ "os"
+ "strconv"
 
  "github.com/gravitational/trace"
 
  devicepb "github.com/gravitational/teleport/api/gen/proto/go/teleport/devicetrust/v1"
 )
 
+// ErrAutoEnrollDisabled signifies that auto-enroll is disabled in the current
+// device.
+// Setting the TELEPORT_DEVICE_AUTO_ENROLL_DISABLED=1 environment disables
+// auto-enroll.
+var ErrAutoEnrollDisabled = errors.New("auto-enroll disabled")
+
 // AutoEnrollCeremony is the auto-enrollment version of [Ceremony].
 type AutoEnrollCeremony struct {
  *Ceremony
@@ -49,6 +58,11 @@ func AutoEnroll(ctx context.Context, devicesClient devicepb.DeviceTrustServiceCl
 // [devicepb.DeviceTrustServiceClient.CreateDeviceEnrollToken] and enrolls the
 // device using a regular [Ceremony].
 func (c *AutoEnrollCeremony) Run(ctx context.Context, devicesClient devicepb.DeviceTrustServiceClient) (*devicepb.Device, error) {
+ const autoEnrollDisabledKey = "TELEPORT_DEVICE_AUTO_ENROLL_DISABLED"
+ if disabled, _ := strconv.ParseBool(os.Getenv(autoEnrollDisabledKey)); disabled {
+ return nil, trace.Wrap(ErrAutoEnrollDisabled)
+ }
+
  // Creating the init message straight away aborts the process cleanly if the
  // device cannot create the device key (for example, if it lacks a TPM).
  // This avoids a situation where we ask for escalation, like a sudo prompt or

lib/devicetrust/enroll/auto_enroll_test.go

@@ -20,6 +20,7 @@ package enroll_test
 
 import (
  "context"
+ "os"
  "testing"
 
  "github.com/stretchr/testify/assert"
@@ -67,3 +68,10 @@ func TestAutoEnrollCeremony_Run(t *testing.T) {
  })
  }
 }
+
+func TestAutoEnroll_disabledByEnv(t *testing.T) {
+ os.Setenv("TELEPORT_DEVICE_AUTO_ENROLL_DISABLED", "1")
+
+ _, err := enroll.AutoEnroll(context.Background(), nil /* devicesClient */)
+ assert.ErrorIs(t, err, enroll.ErrAutoEnrollDisabled, "AutoEnroll() error mismatch")
+}