vault: adding barrier AddKey

vault/barrier.go

@@ -31,6 +31,18 @@ const (
 	// keyringPath is the location of the keyring data. This is encrypted
 	// by the master key.
 	keyringPath = "core/keyring"
+
+	// keyringUpgradePrefix is the path used to store keyring update entries.
+	// When running in HA mode, the active instance will install the new key
+	// and re-write the keyring. For standby instances, they need an upgrade
+	// path from key N to N+1. They cannot just use the master key because
+	// in the event of a rekey, that master key can no longer decrypt the keyring.
+	// When key N+1 is installed, we create an entry at "prefix/N" which uses
+	// encryption key N to provide the N+1 key. The standby instances scan
+	// for this periodically and refresh their keyring. The upgrade keys
+	// are deleted after a few minutes, but this provides enough time for the
+	// standby instances to upgrade without causing any disruption.
+	keyringUpgradePrefix = "core/upgrade/"
 )
 
 // SecurityBarrier is a critical component of Vault. It is used to wrap
@@ -73,6 +85,9 @@ type SecurityBarrier interface {
 	// should use the new key, while old values should still be decryptable.
 	Rotate() error
 
+	// AddKey is used to add a new key to the keyring
+	AddKey(k *Key) error
+
 	// ActiveKeyInfo is used to inform details about the active key
 	ActiveKeyInfo() (*KeyInfo, error)
 

vault/barrier_aes_gcm.go

@@ -335,6 +335,20 @@ func (b *AESGCMBarrier) Rotate() error {
 	return nil
 }
 
+// AddKey is used to add a new key to the keyring. This assumes the keyring
+// has already been updated and does not persist a new keyring.
+func (b *AESGCMBarrier) AddKey(k *Key) error {
+	b.l.Lock()
+	defer b.l.Unlock()
+
+	newKeyring, err := b.keyring.AddKey(k)
+	if err != nil {
+		return fmt.Errorf("failed to add new encryption key: %v", err)
+	}
+	b.keyring = newKeyring
+	return nil
+}
+
 // ActiveKeyInfo is used to inform details about the active key
 func (b *AESGCMBarrier) ActiveKeyInfo() (*KeyInfo, error) {
 	b.l.RLock()

vault/barrier_test.go

@@ -335,6 +335,28 @@ func testBarrier_Rotate(t *testing.T, b SecurityBarrier) {
 	if out == nil {
 		t.Fatalf("bad: %v", out)
 	}
+
+	// Attempt to do AddKey
+	randKey, _ := b.GenerateKey()
+	newKey := &Key{
+		Term:        3,
+		Version:     1,
+		Value:       randKey,
+		InstallTime: time.Now(),
+	}
+	err = b.AddKey(newKey)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	// Check the key info
+	info, err = b.ActiveKeyInfo()
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if info.Term != 3 {
+		t.Fatalf("Bad term: %d", info.Term)
+	}
 }
 
 func testBarrier_Rekey(t *testing.T, b SecurityBarrier) {