Make another unlocker current when the current one is removed (closes #137)

Removing the vault's current unlocker left current-unlocker naming it,
so every command that opened the vault failed although another
unlocker remained, and the error pointed at the mnemonic.
RemoveUnlocker now first makes current the first other unlocker that
`secret unlocker select` accepts, in the order `secret unlocker list`
shows, and returns its ID, which `secret unlocker remove` prints; with
none, current-unlocker is removed too. When current-unlocker names an
unlocker that does not exist and the vault has another that select
accepts, the error wraps ErrUnlockerNotFound and says to run
`secret unlocker select`, without the mnemonic advice.

Unverified: no test covers that advice for a vault other than the
current one, which gets `secret vault select` first.

Model: opus-5-5

internal/cli/unlock_failure_test.go

@@ -4,9 +4,11 @@
 // file the unlocker needs is missing or the passphrase is wrong, the error
 // keeps its cause and ends by saying that the mnemonic still opens that
 // vault, but only for a vault that the mnemonic does open, and not when the
-// passphrase could not be read at all. When a secret's current file is
-// missing, the error says how to make a version current again. Each test
-// that pins such advice also follows it.
+// passphrase could not be read at all. When the current unlocker does not
+// exist and the vault has another that `secret unlocker select` accepts, the
+// error says to select one instead.
+// When a secret's current file is missing, the error says how to make a
+// version current again. Each test that pins such advice also follows it.
 
 package cli_test
 
@@ -222,6 +224,69 @@ func TestMoveUnlockFailureNamesVault(t *testing.T) {
 	assert.Equal(t, "value", getSecret(t, c, "y"))
 }
 
+// TestMissingCurrentUnlockerNamesSelect checks the error of `secret get`
+// when current-unlocker names an unlocker that does not exist and the vault
+// has another: it names the missing unlocker and says to select another
+// one, without the advice to use the mnemonic. The test then follows that
+// advice.
+func TestMissingCurrentUnlockerNamesSelect(t *testing.T) {
+	t.Parallel()
+
+	fs := newTwoVaultFs(t)
+	unlockerDir, c := newUnlockTestCLI(t, fs)
+
+	require.NoError(t, afero.WriteFile(fs,
+		filepath.Join(unlockTestVaultDir, "current-unlocker"),
+		[]byte("missing"), secret.FilePerms))
+
+	err := c.GetSecret(discardCmd(), "x")
+
+	require.ErrorIs(t, err, vault.ErrUnlockerNotFound)
+	require.EqualError(t, err, "failed to unlock vault: "+
+		"failed to get long-term key: failed to get current unlocker: "+
+		"unlocker with ID missing not found; the vault 'default' has other "+
+		"unlockers: run 'secret unlocker select' with the ID of one of them "+
+		"to make it the current unlocker")
+
+	require.NoError(t, c.UnlockerSelect(filepath.Base(unlockerDir)))
+	assert.Equal(t, "value", getSecret(t, c, "x"))
+}
+
+// TestMissingCurrentUnlockerNamesMnemonic checks the error of `secret get`
+// when the unlocker that current-unlocker names does not exist and the
+// vault's only other unlocker is the directory "odd", whose metadata names a
+// type that `secret unlocker select` refuses: the error ends with the advice
+// that the mnemonic still opens the vault, not with advice to select another
+// unlocker. The test then follows that advice.
+func TestMissingCurrentUnlockerNamesMnemonic(t *testing.T) {
+	t.Parallel()
+
+	fs := newTwoVaultFs(t)
+	unlockerDir, c := newUnlockTestCLI(t, fs)
+
+	require.NoError(t, fs.RemoveAll(unlockerDir))
+	require.NoError(t, afero.WriteFile(fs,
+		filepath.Join(unlockTestVaultDir, "unlockers.d", "odd",
+			"unlocker-metadata.json"),
+		[]byte(`{"type": "odd"}`), secret.FilePerms))
+
+	err := c.GetSecret(discardCmd(), "x")
+
+	var cause *os.PathError
+
+	require.ErrorAs(t, err, &cause)
+	require.NotErrorIs(t, err, vault.ErrUnlockerNotFound)
+	require.EqualError(t, err, "failed to unlock vault: "+
+		"failed to get long-term key: failed to get current unlocker: "+
+		"failed to read unlocker metadata: "+cause.Error()+mnemonicAdvice)
+
+	c.Mnemonic = testMnemonicBuffer(t)
+	require.NoError(t, c.UnlockersAdd("passphrase", discardCmd()))
+
+	c.Mnemonic = nil
+	assert.Equal(t, "value", getSecret(t, c, "x"))
+}
+
 // TestPassphraseNotReadNamesNoMnemonic runs `secret get x` on the built
 // binary without SB_UNLOCK_PASSPHRASE and with a stdin that is not a
 // terminal, so the passphrase cannot be read. The unlocker was not tried,

internal/cli/unlockers.go

@@ -222,8 +222,11 @@ func newUnlockerRemoveCmd() *cobra.Command {
 		Long: `Remove an unlocker from the current vault. Asks for ` +
 			`confirmation first, saying whether it is the vault's last ` +
 			`unlocker; when stdin is not a terminal, fails unless --force ` +
-			`is given. Warning: Without unlockers and without your ` +
-			`mnemonic, vault data will be permanently inaccessible.`,
+			`is given. Removing the current unlocker makes another of the ` +
+			`vault's unlockers current, if it has one that ` +
+			`'secret unlocker select' accepts. Warning: Without ` +
+			`unlockers and without your mnemonic, vault data will be ` +
+			`permanently inaccessible.`,
 		Args:              cobra.ExactArgs(1),
 		ValidArgsFunction: getUnlockerIDsCompletionFunc(cli.fs, cli.stateDir),
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -612,13 +615,17 @@ func (cli *Instance) removeUnlocker(
 			"have your mnemonic phrase to access this vault again!")
 	}
 
-	err := found.vlt.RemoveUnlocker(unlockerID)
+	newCurrentID, err := found.vlt.RemoveUnlocker(unlockerID)
 	if err != nil {
 		return err
 	}
 
 	cmd.Printf("Removed unlocker '%s'\n", unlockerID)
 
+	if newCurrentID != "" {
+		cmd.Printf("Switched current unlocker to '%s'\n", newCurrentID)
+	}
+
 	return nil
 }
 

internal/cli/unlockers_remove_test.go

@@ -0,0 +1,94 @@
+//nolint:testpackage // white-box test of unexported internals
+package cli
+
+import (
+	"bytes"
+	"path/filepath"
+	"testing"
+
+	"github.com/awnumar/memguard"
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/secret/internal/secret"
+	"sneak.berlin/go/secret/internal/vault"
+)
+
+// TestUnlockerRemoveCurrent is a regression test for
+// https://git.eeqj.de/sneak/secret/issues/137. A vault has a passphrase
+// unlocker and a PGP unlocker, the current one. Removing the PGP unlocker
+// makes the passphrase unlocker current and says so, and the vault then
+// opens through it. Removing the passphrase unlocker too removes
+// current-unlocker.
+//
+// The second case also gives the vault the unlocker directory "odd", whose
+// metadata names a type that `secret unlocker select` refuses, and which
+// sorts before the passphrase unlocker: neither removal makes it current.
+//
+//nolint:paralleltest // t.Setenv (GNUPGHOME) forbids parallel tests
+func TestUnlockerRemoveCurrent(t *testing.T) {
+	tests := []struct {
+		name    string
+		withOdd bool
+	}{
+		{name: "two unlockers", withOdd: false},
+		{name: "and the directory odd", withOdd: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			newTestGPGKey(t)
+
+			passphrase := memguard.NewBufferFromBytes([]byte(testPassphrase))
+			t.Cleanup(passphrase.Destroy)
+
+			fs := afero.NewMemMapFs()
+			vlt, err := vault.CreateVault(fs, listTestStateDir,
+				listTestVaultName, testMnemonicBuffer(t), nil)
+			require.NoError(t, err)
+
+			passphraseUnlocker, err := vlt.CreatePassphraseUnlocker(passphrase)
+			require.NoError(t, err)
+
+			if tt.withOdd {
+				require.NoError(t, afero.WriteFile(fs,
+					filepath.Join(testVaultDir(listTestVaultName), "unlockers.d",
+						"odd", "unlocker-metadata.json"),
+					[]byte(`{"type": "odd"}`), secret.FilePerms))
+			}
+
+			instance, cmd := newTestInstance(fs)
+			instance.UnlockPassphrase = passphrase
+
+			cmd.Flags().String("keyid", unreadableTestGPGUserID, "")
+			require.NoError(t, instance.UnlockersAdd(unlockerTypePGP, cmd))
+
+			pgpUnlocker, err := vlt.GetCurrentUnlocker()
+			require.NoError(t, err)
+			require.Equal(t, unlockerTypePGP, pgpUnlocker.GetType())
+
+			var output bytes.Buffer
+
+			cmd.SetOut(&output)
+			require.NoError(t,
+				instance.UnlockersRemove(pgpUnlocker.GetID(), true, cmd))
+			assert.Contains(t, output.String(),
+				"Switched current unlocker to '"+passphraseUnlocker.GetID()+"'")
+
+			reopened := vault.NewVault(fs, listTestStateDir, listTestVaultName)
+			reopened.UnlockPassphrase = passphrase
+
+			_, err = reopened.GetOrDeriveLongTermKey()
+			require.NoError(t, err)
+
+			require.NoError(t,
+				instance.UnlockersRemove(passphraseUnlocker.GetID(), true, cmd))
+
+			exists, err := afero.Exists(fs, filepath.Join(
+				testVaultDir(listTestVaultName), "current-unlocker"))
+			require.NoError(t, err)
+			assert.False(t, exists,
+				"current-unlocker is left after the passphrase unlocker")
+		})
+	}
+}