A secret mv between vaults unlocks both vaults before taking the lock (closes #189)

A move between two vaults unlocked them while holding the state directory
lock, and unlocking can ask for a passphrase, so every other changing
command waited at that prompt. moveSecretCrossVault now checks the move,
refusing an existing destination secret without --force, unlocks both
vaults, and only then takes the lock. Under the lock, it checks that the
destination vault still has the long-term key it unlocked, and
copySecretAndRemoveSource checks the move again before it copies. A move
within a vault takes the lock in moveSecretWithinVault, so MoveSecret
takes none itself. The error for a vault created again with another key,
shared with secret unlocker add, now ends "nothing was changed".

Model: opus-5-5

internal/cli/move_cross_vault_test.go

@@ -232,13 +232,18 @@ func TestCrossVaultMoveUnlocksBeforeLocking(t *testing.T) {
 // TestCrossVaultMoveChecksAgainOnceLocked runs a move between vaults, given
 // the mnemonic, as TestCommandsCheckAgainOnceLocked runs the commands in its
 // table: once the move waits for the state directory lock, the test removes
-// the source secret or the destination vault, and the move must then fail
-// and change nothing.
+// the source secret or the destination vault, or creates the destination
+// vault again from another mnemonic, and the move must then fail and change
+// nothing.
 //
 //nolint:paralleltest // waitingForLock sees any test's command waiting for the lock
 func TestCrossVaultMoveChecksAgainOnceLocked(t *testing.T) {
 	mnemonic := testMnemonicBuffer(t)
 
+	otherMnemonic := memguard.NewBufferFromBytes([]byte("legal winner thank " +
+		"year wave sausage worth useful legal winner thank yellow"))
+	t.Cleanup(otherMnemonic.Destroy)
+
 	move := func(cli *Instance) error {
 		cli.Mnemonic = mnemonic
 
@@ -256,6 +261,33 @@ func TestCrossVaultMoveChecksAgainOnceLocked(t *testing.T) {
 			return fs.RemoveAll(testStateDir + "/vaults.d/other")
 		}, vault.ErrVaultNotFound)
 	})
+
+	t.Run("destination vault created again from another mnemonic", func(t *testing.T) {
+		// Set by the move, which has finished once
+		// requireChecksAgainOnceLocked returns
+		var moveErr error
+
+		requireChecksAgainOnceLocked(t, func(cli *Instance) error {
+			moveErr = move(cli)
+
+			return moveErr
+		}, func(fs afero.Fs) error {
+			err := fs.RemoveAll(testStateDir + "/vaults.d/other")
+			if err != nil {
+				return err
+			}
+
+			_, err = vault.CreateVault(fs, testStateDir, "other", otherMnemonic, nil)
+
+			return err
+		}, errVaultCreatedAgain)
+
+		// secret unlocker add fails with the same error, so its message
+		// must fit a move too
+		require.EqualError(t, moveErr, "vault 'other' was removed and "+
+			"created again with another key while it was being unlocked; "+
+			"nothing was changed")
+	})
 }
 
 // TestCrossVaultMoveRefusesExistingSecretBeforeUnlocking checks that a move

internal/cli/secrets.go

@@ -1084,20 +1084,22 @@ func (cli *Instance) sameDirectory(dir, other string) (bool, error) {
 
 // moveSecretCrossVault handles moving between two different vaults. Its
 // caller, MoveSecret, has already checked both secret names and that both
-// vaults exist. The copy needs the source vault's long-term key; the
-// destination vault is unlocked only to check that it can be. Either can ask
-// for a passphrase, so both happen before it takes the state directory lock,
-// and no other command waits while the user answers.
+// vaults exist. The copy needs the source vault's long-term key and is
+// encrypted to the destination vault's long-term public key. The
+// destination vault is unlocked to check that the copy will open with what
+// the user gave, and, once the state directory lock is held, that it still
+// has the key unlocked. Either unlock can ask for a passphrase, so both
+// happen before the lock is taken, and no other command waits while the
+// user answers.
 func (cli *Instance) moveSecretCrossVault(
 	cmd *cobra.Command,
 	srcVault *vault.Vault, srcSecretName string,
 	destVault *vault.Vault, destSecretName string,
 	force bool,
 ) error {
-	// Before unlocking, check that the source secret and the destination
-	// vault exist, that the destination is not the source under another
-	// name, and, without --force, that the destination secret does not
-	// exist
+	// Before unlocking, check that the source secret exists, that the
+	// destination is not the source under another name, and, without
+	// --force, that the destination secret does not exist
 	_, err := cli.checkCrossVaultMove(
 		srcVault, srcSecretName, destVault, destSecretName, force)
 	if err != nil {
@@ -1108,7 +1110,7 @@ func (cli *Instance) moveSecretCrossVault(
 	destVault.Mnemonic, destVault.UnlockPassphrase = cli.Mnemonic, cli.UnlockPassphrase
 
 	// Unlock destination vault (will fail if neither mnemonic nor unlocker available)
-	_, err = destVault.GetOrDeriveLongTermKey()
+	destIdentity, err := destVault.GetOrDeriveLongTermKey()
 	if err != nil {
 		return fmt.Errorf("failed to unlock destination vault '%s': %w", destVault.Name, err)
 	}
@@ -1125,6 +1127,11 @@ func (cli *Instance) moveSecretCrossVault(
 	}
 	defer release()
 
+	err = cli.checkLongTermKey(destVault, destIdentity)
+	if err != nil {
+		return err
+	}
+
 	return cli.copySecretAndRemoveSource(
 		cmd, srcVault, srcSecretName, destVault, destSecretName, force)
 }
@@ -1172,10 +1179,9 @@ func (cli *Instance) copySecretAndRemoveSource(
 }
 
 // checkCrossVaultMove checks that the secret srcSecretName exists in
-// srcVault, that destVault exists, that destSecretName in destVault is not
-// the source under another name, and, unless force is set, that
-// destSecretName does not exist in destVault. It returns the source's
-// directory.
+// srcVault, that destSecretName in destVault is not the source under
+// another name, and, unless force is set, that destSecretName does not
+// exist in destVault. It returns the source's directory.
 func (cli *Instance) checkCrossVaultMove(
 	srcVault *vault.Vault, srcSecretName string,
 	destVault *vault.Vault, destSecretName string,
@@ -1196,11 +1202,6 @@ func (cli *Instance) checkCrossVaultMove(
 			srcSecretName, vault.ErrSecretNotFound, srcVault.Name)
 	}
 
-	_, err = cli.existingVault(destVault.Name)
-	if err != nil {
-		return "", err
-	}
-
 	// The source is removed after the copy, so a destination that is the
 	// source under another name would be lost with it.
 	destVaultDir, err := destVault.GetDirectory()

internal/cli/unlockers.go

@@ -15,6 +15,7 @@ import (
 	"strings"
 	"time"
 
+	"filippo.io/age"
 	"github.com/spf13/afero"
 	"github.com/spf13/cobra"
 	"sneak.berlin/go/secret/internal/secret"
@@ -42,7 +43,7 @@ var (
 	// errVaultCreatedAgain carries only the message tail; the caller
 	// composes "vault '<name>' was removed and created again ...".
 	errVaultCreatedAgain = errors.New("was removed and created again " +
-		"with another key while it was being unlocked; nothing was added")
+		"with another key while it was being unlocked; nothing was changed")
 )
 
 // UnlockerInfo represents unlocker information for display
@@ -442,29 +443,41 @@ func (cli *Instance) unlockThenLock(vlt *vault.Vault) (func(), error) {
 		return nil, err
 	}
 
-	_, err = cli.existingVault(vlt.GetName())
+	err = cli.checkLongTermKey(vlt, ltIdentity)
 	if err != nil {
 		release()
 
 		return nil, err
 	}
 
+	return release, nil
+}
+
+// checkLongTermKey checks, for the vault vlt unlocked as ltIdentity before
+// the state directory lock was taken, that vlt still exists and that its
+// long-term public key is still that of ltIdentity. Another command may have
+// removed the vault in the meantime, or removed it and created it again with
+// another long-term key. The caller holds the lock.
+func (cli *Instance) checkLongTermKey(
+	vlt *vault.Vault, ltIdentity *age.X25519Identity,
+) error {
+	_, err := cli.existingVault(vlt.GetName())
+	if err != nil {
+		return err
+	}
+
 	vaultDir, _ := vlt.GetDirectory()
 
 	ltPubKey, err := afero.ReadFile(cli.fs, filepath.Join(vaultDir, "pub.age"))
 	if err != nil {
-		release()
-
-		return nil, fmt.Errorf("failed to read long-term public key: %w", err)
+		return fmt.Errorf("failed to read long-term public key: %w", err)
 	}
 
 	if string(ltPubKey) != ltIdentity.Recipient().String() {
-		release()
-
-		return nil, fmt.Errorf("vault '%s' %w", vlt.GetName(), errVaultCreatedAgain)
+		return fmt.Errorf("vault '%s' %w", vlt.GetName(), errVaultCreatedAgain)
 	}
 
-	return release, nil
+	return nil
 }
 
 // autoSelectUnlocker selects the newly created unlocker as current,