fix(GODT-2606): Improve Vault concurrency scopes

Rewrite the vault to have one RWlock rather then two separate locks for
data and reference counts.

In certain circumstance, it could be possible that that different
requests could end up in undefined states if a user got deleted
successfully while at he same time another goroutine/thread is loading
the given user.

While I have not been able to reproduce this in a test, restricting the
access scope to one lock rather than two, should avoid corner cases
where logic code is executing outside of the lock scope.

internal/vault/certs.go

@@ -30,7 +30,12 @@ import (
 // If CertPEMPath is set, it will attempt to read the certificate from the file.
 // Otherwise, or on read/validation failure, it will return the certificate from the vault.
 func (vault *Vault) GetBridgeTLSCert() ([]byte, []byte) {
-	if certPath, keyPath := vault.get().Certs.CustomCertPath, vault.get().Certs.CustomKeyPath; certPath != "" && keyPath != "" {
+	vault.lock.RLock()
+	defer vault.lock.RUnlock()
+
+	certs := vault.getUnsafe().Certs
+
+	if certPath, keyPath := certs.CustomCertPath, certs.CustomKeyPath; certPath != "" && keyPath != "" {
 		if certPEM, keyPEM, err := readPEMCert(certPath, keyPath); err == nil {
 			return certPEM, keyPEM
 		}
@@ -38,7 +43,7 @@ func (vault *Vault) GetBridgeTLSCert() ([]byte, []byte) {
 		logrus.Error("Failed to read certificate from file, using default")
 	}
 
-	return vault.get().Certs.Bridge.Cert, vault.get().Certs.Bridge.Key
+	return certs.Bridge.Cert, certs.Bridge.Key
 }
 
 // SetBridgeTLSCertPath sets the path to PEM-encoded certificates for the bridge.
@@ -47,7 +52,7 @@ func (vault *Vault) SetBridgeTLSCertPath(certPath, keyPath string) error {
 		return fmt.Errorf("invalid certificate: %w", err)
 	}
 
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Certs.CustomCertPath = certPath
 		data.Certs.CustomKeyPath = keyPath
 	})
@@ -55,18 +60,18 @@ func (vault *Vault) SetBridgeTLSCertPath(certPath, keyPath string) error {
 
 // SetBridgeTLSCertKey sets the path to PEM-encoded certificates for the bridge.
 func (vault *Vault) SetBridgeTLSCertKey(cert, key []byte) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Certs.Bridge.Cert = cert
 		data.Certs.Bridge.Key = key
 	})
 }
 
 func (vault *Vault) GetCertsInstalled() bool {
-	return vault.get().Certs.Installed
+	return vault.getSafe().Certs.Installed
 }
 
 func (vault *Vault) SetCertsInstalled(installed bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Certs.Installed = installed
 	})
 }

internal/vault/cookies.go

@@ -18,11 +18,11 @@
 package vault
 
 func (vault *Vault) GetCookies() ([]byte, error) {
-	return vault.get().Cookies, nil
+	return vault.getSafe().Cookies, nil
 }
 
 func (vault *Vault) SetCookies(cookies []byte) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Cookies = cookies
 	})
 }

internal/vault/settings.go

@@ -33,72 +33,72 @@ const (
 
 // GetIMAPPort sets the port that the IMAP server should listen on.
 func (vault *Vault) GetIMAPPort() int {
-	return vault.get().Settings.IMAPPort
+	return vault.getSafe().Settings.IMAPPort
 }
 
 // SetIMAPPort sets the port that the IMAP server should listen on.
 func (vault *Vault) SetIMAPPort(port int) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.IMAPPort = port
 	})
 }
 
 // GetSMTPPort sets the port that the SMTP server should listen on.
 func (vault *Vault) GetSMTPPort() int {
-	return vault.get().Settings.SMTPPort
+	return vault.getSafe().Settings.SMTPPort
 }
 
 // SetSMTPPort sets the port that the SMTP server should listen on.
 func (vault *Vault) SetSMTPPort(port int) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.SMTPPort = port
 	})
 }
 
 // GetIMAPSSL sets whether the IMAP server should use SSL.
 func (vault *Vault) GetIMAPSSL() bool {
-	return vault.get().Settings.IMAPSSL
+	return vault.getSafe().Settings.IMAPSSL
 }
 
 // SetIMAPSSL sets whether the IMAP server should use SSL.
 func (vault *Vault) SetIMAPSSL(ssl bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.IMAPSSL = ssl
 	})
 }
 
 // GetSMTPSSL sets whether the SMTP server should use SSL.
 func (vault *Vault) GetSMTPSSL() bool {
-	return vault.get().Settings.SMTPSSL
+	return vault.getSafe().Settings.SMTPSSL
 }
 
 // SetSMTPSSL sets whether the SMTP server should use SSL.
 func (vault *Vault) SetSMTPSSL(ssl bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.SMTPSSL = ssl
 	})
 }
 
 // GetGluonCacheDir sets the directory where the gluon should store its data.
 func (vault *Vault) GetGluonCacheDir() string {
-	return vault.get().Settings.GluonDir
+	return vault.getSafe().Settings.GluonDir
 }
 
 // SetGluonDir sets the directory where the gluon should store its data.
 func (vault *Vault) SetGluonDir(dir string) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.GluonDir = dir
 	})
 }
 
 // GetUpdateChannel sets the update channel.
 func (vault *Vault) GetUpdateChannel() updater.Channel {
-	return vault.get().Settings.UpdateChannel
+	return vault.getSafe().Settings.UpdateChannel
 }
 
 // SetUpdateChannel sets the update channel.
 func (vault *Vault) SetUpdateChannel(channel updater.Channel) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.UpdateChannel = channel
 	})
 }
@@ -106,7 +106,7 @@ func (vault *Vault) SetUpdateChannel(channel updater.Channel) error {
 // GetUpdateRollout sets the update rollout.
 func (vault *Vault) GetUpdateRollout() float64 {
 	// The rollout value 0.6046602879796196 is forbidden. The RNG was not seeded when it was picked (GODT-2319).
-	rollout := vault.get().Settings.UpdateRollout
+	rollout := vault.getSafe().Settings.UpdateRollout
 	if math.Abs(rollout-ForbiddenRollout) >= 0.00000001 {
 		return rollout
 	}
@@ -120,110 +120,110 @@ func (vault *Vault) GetUpdateRollout() float64 {
 
 // SetUpdateRollout sets the update rollout.
 func (vault *Vault) SetUpdateRollout(rollout float64) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.UpdateRollout = rollout
 	})
 }
 
 // GetColorScheme sets the color scheme to be used by the bridge GUI.
 func (vault *Vault) GetColorScheme() string {
-	return vault.get().Settings.ColorScheme
+	return vault.getSafe().Settings.ColorScheme
 }
 
 // SetColorScheme sets the color scheme to be used by the bridge GUI.
 func (vault *Vault) SetColorScheme(colorScheme string) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.ColorScheme = colorScheme
 	})
 }
 
 // GetProxyAllowed sets whether the bridge is allowed to use alternative routing.
 func (vault *Vault) GetProxyAllowed() bool {
-	return vault.get().Settings.ProxyAllowed
+	return vault.getSafe().Settings.ProxyAllowed
 }
 
 // SetProxyAllowed sets whether the bridge is allowed to use alternative routing.
 func (vault *Vault) SetProxyAllowed(allowed bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.ProxyAllowed = allowed
 	})
 }
 
 // GetShowAllMail sets whether the bridge should show the All Mail folder.
 func (vault *Vault) GetShowAllMail() bool {
-	return vault.get().Settings.ShowAllMail
+	return vault.getSafe().Settings.ShowAllMail
 }
 
 // SetShowAllMail sets whether the bridge should show the All Mail folder.
 func (vault *Vault) SetShowAllMail(showAllMail bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.ShowAllMail = showAllMail
 	})
 }
 
 // GetAutostart sets whether the bridge should autostart.
 func (vault *Vault) GetAutostart() bool {
-	return vault.get().Settings.Autostart
+	return vault.getSafe().Settings.Autostart
 }
 
 // SetAutostart sets whether the bridge should autostart.
 func (vault *Vault) SetAutostart(autostart bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.Autostart = autostart
 	})
 }
 
 // GetAutoUpdate sets whether the bridge should automatically update.
 func (vault *Vault) GetAutoUpdate() bool {
-	return vault.get().Settings.AutoUpdate
+	return vault.getSafe().Settings.AutoUpdate
 }
 
 // SetAutoUpdate sets whether the bridge should automatically update.
 func (vault *Vault) SetAutoUpdate(autoUpdate bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.AutoUpdate = autoUpdate
 	})
 }
 
 // GetTelemetryDisabled checks whether telemetry is disabled.
 func (vault *Vault) GetTelemetryDisabled() bool {
-	return vault.get().Settings.TelemetryDisabled
+	return vault.getSafe().Settings.TelemetryDisabled
 }
 
 // SetTelemetryDisabled sets whether telemetry is disabled.
 func (vault *Vault) SetTelemetryDisabled(telemetryDisabled bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.TelemetryDisabled = telemetryDisabled
 	})
 }
 
 // GetLastVersion returns the last version of the bridge that was run.
 func (vault *Vault) GetLastVersion() *semver.Version {
-	return semver.MustParse(vault.get().Settings.LastVersion)
+	return semver.MustParse(vault.getSafe().Settings.LastVersion)
 }
 
 // SetLastVersion sets the last version of the bridge that was run.
 func (vault *Vault) SetLastVersion(version *semver.Version) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.LastVersion = version.String()
 	})
 }
 
 // GetFirstStart returns whether this is the first time the bridge has been started.
 func (vault *Vault) GetFirstStart() bool {
-	return vault.get().Settings.FirstStart
+	return vault.getSafe().Settings.FirstStart
 }
 
 // SetFirstStart sets whether this is the first time the bridge has been started.
 func (vault *Vault) SetFirstStart(firstStart bool) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.FirstStart = firstStart
 	})
 }
 
 // GetMaxSyncMemory returns the maximum amount of memory the sync process should use.
 func (vault *Vault) GetMaxSyncMemory() uint64 {
-	v := vault.get().Settings.MaxSyncMemory
+	v := vault.getSafe().Settings.MaxSyncMemory
 	// can be zero if never written to vault before.
 	if v == 0 {
 		return DefaultMaxSyncMemory
@@ -234,14 +234,14 @@ func (vault *Vault) GetMaxSyncMemory() uint64 {
 
 // SetMaxSyncMemory sets the maximum amount of memory the sync process should use.
 func (vault *Vault) SetMaxSyncMemory(maxMemory uint64) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.MaxSyncMemory = maxMemory
 	})
 }
 
 // GetLastUserAgent returns the last user agent recorded by bridge.
 func (vault *Vault) GetLastUserAgent() string {
-	v := vault.get().Settings.LastUserAgent
+	v := vault.getSafe().Settings.LastUserAgent
 
 	// Handle case where there may be no value.
 	if len(v) == 0 {
@@ -253,19 +253,19 @@ func (vault *Vault) GetLastUserAgent() string {
 
 // SetLastUserAgent store the last user agent recorded by bridge.
 func (vault *Vault) SetLastUserAgent(userAgent string) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.LastUserAgent = userAgent
 	})
 }
 
 // GetLastHeartbeatSent returns the last time heartbeat was sent.
 func (vault *Vault) GetLastHeartbeatSent() time.Time {
-	return vault.get().Settings.LastHeartbeatSent
+	return vault.getSafe().Settings.LastHeartbeatSent
 }
 
 // SetLastHeartbeatSent store the last time heartbeat was sent.
 func (vault *Vault) SetLastHeartbeatSent(timestamp time.Time) error {
-	return vault.mod(func(data *Data) {
+	return vault.modSafe(func(data *Data) {
 		data.Settings.LastHeartbeatSent = timestamp
 	})
 }

internal/vault/user.go

@@ -122,6 +122,14 @@ func (user *User) SetAuth(authUID, authRef string) error {
 	})
 }
 
+func (user *User) setAuthAndKeyPassUnsafe(authUID, authRef string, keyPass []byte) error {
+	return user.vault.modUserUnsafe(user.userID, func(userData *UserData) {
+		userData.AuthRef = authRef
+		userData.AuthUID = authUID
+		userData.KeyPass = keyPass
+	})
+}
+
 // KeyPass returns the user's (salted) key password.
 func (user *User) KeyPass() []byte {
 	return user.vault.getUser(user.userID).KeyPass

internal/vault/vault.go

@@ -40,11 +40,11 @@ type Vault struct {
 	path string
 	gcm  cipher.AEAD
 
-	enc     []byte
-	encLock sync.RWMutex
+	enc []byte
 
-	ref     map[string]int
-	refLock sync.Mutex
+	ref map[string]int
+
+	lock sync.RWMutex
 
 	panicHandler async.PanicHandler
 }
@@ -79,14 +79,46 @@ func New(vaultDir, gluonCacheDir string, key []byte, panicHandler async.PanicHan
 
 // GetUserIDs returns the user IDs and usernames of all users in the vault.
 func (vault *Vault) GetUserIDs() []string {
-	return xslices.Map(vault.get().Users, func(user UserData) string {
+	vault.lock.RLock()
+	defer vault.lock.RUnlock()
+
+	return xslices.Map(vault.getUnsafe().Users, func(user UserData) string {
 		return user.UserID
 	})
 }
 
+func (vault *Vault) getUsers() ([]*User, error) {
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
+
+	users := vault.getUnsafe().Users
+
+	result := make([]*User, 0, len(users))
+
+	for _, user := range users {
+		u, err := vault.newUserUnsafe(user.UserID)
+		if err != nil {
+			for _, v := range result {
+				if err := v.Close(); err != nil {
+					logrus.WithError(err).Error("Fait to close user after failed get")
+				}
+			}
+
+			return nil, err
+		}
+
+		result = append(result, u)
+	}
+
+	return result, nil
+}
+
 // HasUser returns true if the vault contains a user with the given ID.
 func (vault *Vault) HasUser(userID string) bool {
-	return xslices.IndexFunc(vault.get().Users, func(user UserData) bool {
+	vault.lock.RLock()
+	defer vault.lock.RUnlock()
+
+	return xslices.IndexFunc(vault.getUnsafe().Users, func(user UserData) bool {
 		return user.UserID == userID
 	}) >= 0
 }
@@ -106,41 +138,61 @@ func (vault *Vault) GetUser(userID string, fn func(*User)) error {
 
 // NewUser returns a new vault user. It must be closed before it can be deleted.
 func (vault *Vault) NewUser(userID string) (*User, error) {
-	if idx := xslices.IndexFunc(vault.get().Users, func(user UserData) bool {
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
+
+	return vault.newUserUnsafe(userID)
+}
+
+func (vault *Vault) newUserUnsafe(userID string) (*User, error) {
+	if idx := xslices.IndexFunc(vault.getUnsafe().Users, func(user UserData) bool {
 		return user.UserID == userID
 	}); idx < 0 {
 		return nil, errors.New("no such user")
 	}
 
-	return vault.attachUser(userID), nil
+	return vault.attachUserUnsafe(userID), nil
 }
 
 // ForUser executes a callback for each user in the vault.
 func (vault *Vault) ForUser(parallelism int, fn func(*User) error) error {
-	userIDs := vault.GetUserIDs()
+	users, err := vault.getUsers()
+	if err != nil {
+		return err
+	}
 
-	return parallel.DoContext(context.Background(), parallelism, len(userIDs), func(_ context.Context, idx int) error {
+	r := parallel.DoContext(context.Background(), parallelism, len(users), func(_ context.Context, idx int) error {
 		defer async.HandlePanic(vault.panicHandler)
 
-		user, err := vault.NewUser(userIDs[idx])
-		if err != nil {
-			return err
-		}
-		defer func() { _ = user.Close() }()
-
+		user := users[idx]
 		return fn(user)
 	})
+
+	for _, u := range users {
+		if err := u.Close(); err != nil {
+			logrus.WithError(err).Error("Failed to close user after ForUser")
+		}
+	}
+
+	return r
 }
 
 // AddUser creates a new user in the vault with the given ID, username and password.
 // A gluon key is generated using the package's token generator. If a password is found in the password archive for this user,
 // it is restored, otherwise a new bridge password is generated using the package's token generator.
 func (vault *Vault) AddUser(userID, username, primaryEmail, authUID, authRef string, keyPass []byte) (*User, error) {
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
+
+	return vault.addUserUnsafe(userID, username, primaryEmail, authUID, authRef, keyPass)
+}
+
+func (vault *Vault) addUserUnsafe(userID, username, primaryEmail, authUID, authRef string, keyPass []byte) (*User, error) {
 	logrus.WithField("userID", userID).Info("Adding vault user")
 
 	var exists bool
 
-	if err := vault.mod(func(data *Data) {
+	if err := vault.modUnsafe(func(data *Data) {
 		if idx := xslices.IndexFunc(data.Users, func(user UserData) bool {
 			return user.UserID == userID
 		}); idx >= 0 {
@@ -161,13 +213,42 @@ func (vault *Vault) AddUser(userID, username, primaryEmail, authUID, authRef str
 		return nil, errors.New("user already exists")
 	}
 
-	return vault.NewUser(userID)
+	return vault.attachUserUnsafe(userID), nil
+}
+
+// GetOrAddUser retrieves an existing user and updates the authRef and keyPass or creates a new user. Returns
+// the user and whether the user did not exist before.
+func (vault *Vault) GetOrAddUser(userID, username, primaryEmail, authUID, authRef string, keyPass []byte) (*User, bool, error) {
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
+
+	{
+		users := vault.getUnsafe().Users
+
+		idx := xslices.IndexFunc(users, func(user UserData) bool {
+			return user.UserID == userID
+		})
+
+		if idx >= 0 {
+			user := vault.attachUserUnsafe(userID)
+
+			if err := user.setAuthAndKeyPassUnsafe(authUID, authRef, keyPass); err != nil {
+				return nil, false, err
+			}
+
+			return user, false, nil
+		}
+	}
+
+	u, err := vault.addUserUnsafe(userID, username, primaryEmail, authUID, authRef, keyPass)
+
+	return u, true, err
 }
 
 // DeleteUser removes the given user from the vault.
 func (vault *Vault) DeleteUser(userID string) error {
-	vault.refLock.Lock()
-	defer vault.refLock.Unlock()
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
 
 	logrus.WithField("userID", userID).Info("Deleting vault user")
 
@@ -175,7 +256,7 @@ func (vault *Vault) DeleteUser(userID string) error {
 		return fmt.Errorf("user %s is currently in use", userID)
 	}
 
-	return vault.mod(func(data *Data) {
+	return vault.modUnsafe(func(data *Data) {
 		idx := xslices.IndexFunc(data.Users, func(user UserData) bool {
 			return user.UserID == userID
 		})
@@ -189,17 +270,26 @@ func (vault *Vault) DeleteUser(userID string) error {
 }
 
 func (vault *Vault) Migrated() bool {
-	return vault.get().Migrated
+	vault.lock.RLock()
+	defer vault.lock.RUnlock()
+
+	return vault.getUnsafe().Migrated
 }
 
 func (vault *Vault) SetMigrated() error {
-	return vault.mod(func(data *Data) {
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
+
+	return vault.modUnsafe(func(data *Data) {
 		data.Migrated = true
 	})
 }
 
 func (vault *Vault) Reset(gluonDir string) error {
-	return vault.mod(func(data *Data) {
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
+
+	return vault.modUnsafe(func(data *Data) {
 		*data = newDefaultData(gluonDir)
 	})
 }
@@ -209,8 +299,8 @@ func (vault *Vault) Path() string {
 }
 
 func (vault *Vault) Close() error {
-	vault.refLock.Lock()
-	defer vault.refLock.Unlock()
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
 
 	if len(vault.ref) > 0 {
 		return errors.New("vault is still in use")
@@ -221,10 +311,7 @@ func (vault *Vault) Close() error {
 	return nil
 }
 
-func (vault *Vault) attachUser(userID string) *User {
-	vault.refLock.Lock()
-	defer vault.refLock.Unlock()
-
+func (vault *Vault) attachUserUnsafe(userID string) *User {
 	logrus.WithField("userID", userID).Trace("Attaching vault user")
 
 	vault.ref[userID]++
@@ -236,8 +323,8 @@ func (vault *Vault) attachUser(userID string) *User {
 }
 
 func (vault *Vault) detachUser(userID string) error {
-	vault.refLock.Lock()
-	defer vault.refLock.Unlock()
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
 
 	logrus.WithField("userID", userID).Trace("Detaching vault user")
 
@@ -289,10 +376,14 @@ func newVault(path, gluonDir string, gcm cipher.AEAD) (*Vault, bool, error) {
 	}, corrupt, nil
 }
 
-func (vault *Vault) get() Data {
-	vault.encLock.RLock()
-	defer vault.encLock.RUnlock()
+func (vault *Vault) getSafe() Data {
+	vault.lock.RLock()
+	defer vault.lock.RUnlock()
 
+	return vault.getUnsafe()
+}
+
+func (vault *Vault) getUnsafe() Data {
 	var data Data
 
 	if err := unmarshalFile(vault.gcm, vault.enc, &data); err != nil {
@@ -302,10 +393,14 @@ func (vault *Vault) get() Data {
 	return data
 }
 
-func (vault *Vault) mod(fn func(data *Data)) error {
-	vault.encLock.Lock()
-	defer vault.encLock.Unlock()
+func (vault *Vault) modSafe(fn func(data *Data)) error {
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
 
+	return vault.modUnsafe(fn)
+}
+
+func (vault *Vault) modUnsafe(fn func(data *Data)) error {
 	var data Data
 
 	if err := unmarshalFile(vault.gcm, vault.enc, &data); err != nil {
@@ -325,13 +420,31 @@ func (vault *Vault) mod(fn func(data *Data)) error {
 }
 
 func (vault *Vault) getUser(userID string) UserData {
-	return vault.get().Users[xslices.IndexFunc(vault.get().Users, func(user UserData) bool {
+	vault.lock.RLock()
+	defer vault.lock.RUnlock()
+
+	users := vault.getUnsafe().Users
+
+	idx := xslices.IndexFunc(users, func(user UserData) bool {
 		return user.UserID == userID
-	})]
+	})
+
+	if idx < 0 {
+		panic("Unknown user")
+	}
+
+	return users[idx]
 }
 
 func (vault *Vault) modUser(userID string, fn func(userData *UserData)) error {
-	return vault.mod(func(data *Data) {
+	vault.lock.Lock()
+	defer vault.lock.Unlock()
+
+	return vault.modUserUnsafe(userID, fn)
+}
+
+func (vault *Vault) modUserUnsafe(userID string, fn func(userData *UserData)) error {
+	return vault.modUnsafe(func(data *Data) {
 		idx := xslices.IndexFunc(data.Users, func(user UserData) bool {
 			return user.UserID == userID
 		})

internal/vault/vault_debug.go

@@ -24,7 +24,7 @@ import (
 )
 
 func (vault *Vault) ImportJSON(dec []byte) {
-	vault.mod(func(data *Data) {
+	vault.modSafe(func(data *Data) {
 		if err := json.Unmarshal(dec, data); err != nil {
 			panic(err)
 		}
@@ -32,7 +32,7 @@ func (vault *Vault) ImportJSON(dec []byte) {
 }
 
 func (vault *Vault) ExportJSON() []byte {
-	enc, err := json.MarshalIndent(vault.get(), "", "  ")
+	enc, err := json.MarshalIndent(vault.getSafe(), "", "  ")
 	if err != nil {
 		panic(err)
 	}