m: remove references to LUK, GUK

This unifies the unlock key nomenclature throughout the repository:
- Local Unlock Key becomes a Node Unlock Key
- Global Unlock Key becomes a Cluster Unlock Key

Change-Id: I674ad68a50b3845705f3e2c57952fc7fba5be665
Reviewed-on: https://review.monogon.dev/c/monogon/+/816
Reviewed-by: Sergiusz Bazanski <serge@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/handbook/src/ch03-00-cluster-architecture.md b/metropolis/handbook/src/ch03-00-cluster-architecture.md
index 9f5669c..68c9384 100644
--- a/metropolis/handbook/src/ch03-00-cluster-architecture.md
+++ b/metropolis/handbook/src/ch03-00-cluster-architecture.md
@@ -54,7 +54,7 @@
 '-------------------'           | Seals/Unseals
          | Mounts               v
          |           .---------------------.        .------------------------.
-         | .---------| Node Encryption Key |        |    Running Cluster     |
+         | .---------|   Node Unlock Key   |        |    Running Cluster     |
          |/          '---------------------'        |------------------------|
          | .----------------------------------------| Cluster Encryption Key |
          |/                                         |       (per node)       |
diff --git a/metropolis/node/core/cluster/cluster_bootstrap.go b/metropolis/node/core/cluster/cluster_bootstrap.go
index 9de5339..707c26c 100644
--- a/metropolis/node/core/cluster/cluster_bootstrap.go
+++ b/metropolis/node/core/cluster/cluster_bootstrap.go
@@ -37,7 +37,7 @@
 	ownerKey := bootstrap.OwnerPublicKey
 	state.configuration = &ppb.SealedConfiguration{}
 
-	// Mount new storage with generated CUK, and save LUK into sealed config proto.
+	// Mount new storage with generated CUK, and save NUK into sealed config proto.
 	supervisor.Logger(ctx).Infof("Bootstrapping: mounting new storage...")
 	cuk, err := m.storageRoot.Data.MountNew(state.configuration)
 	if err != nil {
diff --git a/metropolis/node/core/localstorage/directory_data.go b/metropolis/node/core/localstorage/directory_data.go
index 5992bf0..d88afb7 100644
--- a/metropolis/node/core/localstorage/directory_data.go
+++ b/metropolis/node/core/localstorage/directory_data.go
@@ -31,8 +31,8 @@
 
 var keySize uint16 = 256 / 8
 
-// MountData mounts the node data partition with the given global unlock key.
-// It automatically unseals the local unlock key from the TPM.
+// MountData mounts the node data partition with the given cluster unlock key.
+// It automatically unseals the node unlock key from the TPM.
 func (d *DataDirectory) MountExisting(config *ppb.SealedConfiguration, clusterUnlockKey []byte) error {
 	d.flagLock.Lock()
 	defer d.flagLock.Unlock()
@@ -82,7 +82,7 @@
 		_, err = rand.Read(nodeUnlockKey)
 	}
 	if err != nil {
-		return nil, fmt.Errorf("generating local unlock key: %w", err)
+		return nil, fmt.Errorf("generating node unlock key: %w", err)
 	}
 	if tpm.IsInitialized() {
 		globalUnlockKey, err = tpm.GenerateSafeKey(keySize)
@@ -91,7 +91,7 @@
 		_, err = rand.Read(globalUnlockKey)
 	}
 	if err != nil {
-		return nil, fmt.Errorf("generating global unlock key: %w", err)
+		return nil, fmt.Errorf("generating cluster unlock key: %w", err)
 	}
 
 	// The actual key is generated by XORing together the nodeUnlockKey and the
diff --git a/metropolis/proto/common/common.proto b/metropolis/proto/common/common.proto
index 15dc9e3..c25736b 100644
--- a/metropolis/proto/common/common.proto
+++ b/metropolis/proto/common/common.proto
@@ -64,7 +64,7 @@
     // NEW: the node has established a first contact with the cluster and
     // intends to register into it. The node's identity has not been verified
     // and no hardware attestation of the new node was performed.
-    // The node has generated a CUK/LUK and set up storage encrypted with the
+    // The node has generated a CUK/NUK and set up storage encrypted with the
     // combination of both keys.
     // The node has generated a private/public keypair, and that keypair has
     // been used to contact the already running Cluster.