VAULT-24736 CE changes for static secret capability behaviour toggle (#26744)

command/agentproxyshared/cache/static_secret_cache_updater.go

@@ -180,7 +180,7 @@ func (updater *StaticSecretCacheUpdater) streamStaticSecretEvents(ctx context.Co
 	return nil
 }
 
-// preEventStreamUpdate is called after successful connection to the event system but before
+// preEventStreamUpdate is called after successful connection to the event system, but before
 // we process any events, to ensure we don't miss any updates.
 // In some cases, this will result in multiple processing of the same updates, but
 // this ensures that we don't lose any updates to secrets that might have been sent

command/agentproxyshared/cache/static_secret_capability_manager.go

@@ -19,6 +19,13 @@ import (
 	"golang.org/x/exp/maps"
 )
 
+type TokenCapabilityRefreshBehaviour int
+
+const (
+	TokenCapabilityRefreshBehaviourOptimistic TokenCapabilityRefreshBehaviour = iota
+	TokenCapabilityRefreshBehaviourPessimistic
+)
+
 const (
 	// DefaultWorkers is the default number of workers for the worker pool.
 	DefaultWorkers = 5
@@ -37,15 +44,17 @@ type StaticSecretCapabilityManager struct {
 	logger                                     hclog.Logger
 	workerPool                                 *workerpool.WorkerPool
 	staticSecretTokenCapabilityRefreshInterval time.Duration
+	tokenCapabilityRefreshBehaviour            TokenCapabilityRefreshBehaviour
 }
 
 // StaticSecretCapabilityManagerConfig is the configuration for initializing a new
 // StaticSecretCapabilityManager.
 type StaticSecretCapabilityManagerConfig struct {
-	LeaseCache                                 *LeaseCache
-	Logger                                     hclog.Logger
-	Client                                     *api.Client
-	StaticSecretTokenCapabilityRefreshInterval time.Duration
+	LeaseCache                                  *LeaseCache
+	Logger                                      hclog.Logger
+	Client                                      *api.Client
+	StaticSecretTokenCapabilityRefreshInterval  time.Duration
+	StaticSecretTokenCapabilityRefreshBehaviour string
 }
 
 // NewStaticSecretCapabilityManager creates a new instance of a StaticSecretCapabilityManager.
@@ -70,6 +79,18 @@ func NewStaticSecretCapabilityManager(conf *StaticSecretCapabilityManagerConfig)
 		conf.StaticSecretTokenCapabilityRefreshInterval = DefaultStaticSecretTokenCapabilityRefreshInterval
 	}
 
+	behaviour := TokenCapabilityRefreshBehaviourOptimistic
+	if conf.StaticSecretTokenCapabilityRefreshBehaviour != "" {
+		switch conf.StaticSecretTokenCapabilityRefreshBehaviour {
+		case "optimistic":
+			behaviour = TokenCapabilityRefreshBehaviourOptimistic
+		case "pessimistic":
+			behaviour = TokenCapabilityRefreshBehaviourPessimistic
+		default:
+			return nil, fmt.Errorf("TokenCapabilityRefreshBehaviour must be either \"optimistic\" or \"pessimistic\"")
+		}
+	}
+
 	workerPool := workerpool.New(DefaultWorkers)
 
 	return &StaticSecretCapabilityManager{
@@ -78,6 +99,7 @@ func NewStaticSecretCapabilityManager(conf *StaticSecretCapabilityManagerConfig)
 		logger:     conf.Logger,
 		workerPool: workerPool,
 		staticSecretTokenCapabilityRefreshInterval: conf.StaticSecretTokenCapabilityRefreshInterval,
+		tokenCapabilityRefreshBehaviour:            behaviour,
 	}, nil
 }
 
@@ -136,9 +158,15 @@ func (sscm *StaticSecretCapabilityManager) StartRenewingCapabilities(indexToRene
 
 		capabilities, err := getCapabilities(indexReadablePaths, client)
 		if err != nil {
-			sscm.logger.Error("error when attempting to retrieve updated token capabilities", "indexToRenew.ID", indexToRenew.ID, "err", err)
-			sscm.submitWorkToPoolAfterInterval(work)
-			return
+			sscm.logger.Warn("error when attempting to retrieve updated token capabilities", "indexToRenew.ID", indexToRenew.ID, "err", err)
+			if sscm.tokenCapabilityRefreshBehaviour == TokenCapabilityRefreshBehaviourPessimistic {
+				// Vault is be sealed or unreachable. If pessimistic, assume we might have
+				// lost access. Set capabilities to an empty set, so they are all removed.
+				capabilities = make(map[string][]string)
+			} else {
+				sscm.submitWorkToPoolAfterInterval(work)
+				return
+			}
 		}
 
 		newReadablePaths := reconcileCapabilities(indexReadablePaths, capabilities)
@@ -188,6 +216,7 @@ func (sscm *StaticSecretCapabilityManager) StartRenewingCapabilities(indexToRene
 				sscm.submitWorkToPoolAfterInterval(work)
 				return
 			}
+			sscm.logger.Debug("successfully evicted capabilities index from cache", "index.ID", indexToRenew.ID)
 			// If we successfully evicted the index, no need to re-submit the work to the pool.
 			return
 		}

command/agentproxyshared/cache/static_secret_capability_manager_test.go

@@ -345,6 +345,88 @@ func TestSubmitWorkUpdatesIndexWithBadToken(t *testing.T) {
 	sscm.workerPool.Stop()
 }
 
+// TestSubmitWorkSealedVaultOptimistic tests that the capability manager
+// behaves as expected when
+// sscm.tokenCapabilityRefreshBehaviour == TokenCapabilityRefreshBehaviourOptimistic
+func TestSubmitWorkSealedVaultOptimistic(t *testing.T) {
+	t.Parallel()
+	cluster := minimal.NewTestSoloCluster(t, nil)
+	client := cluster.Cores[0].Client
+
+	token := "not real token"
+	indexId := hashStaticSecretIndex(token)
+
+	sscm := testNewStaticSecretCapabilityManager(t, client)
+	index := &cachememdb.CapabilitiesIndex{
+		ID:    indexId,
+		Token: token,
+		ReadablePaths: map[string]struct{}{
+			"foo/bar":                {},
+			"auth/token/lookup-self": {},
+		},
+	}
+	err := sscm.leaseCache.db.SetCapabilitiesIndex(index)
+	require.Nil(t, err)
+
+	// Seal the cluster
+	cluster.EnsureCoresSealed(t)
+
+	sscm.StartRenewingCapabilities(index)
+
+	// Wait for the job to complete at least once...
+	time.Sleep(3 * time.Second)
+
+	// This entry should not be evicted.
+	newIndex, err := sscm.leaseCache.db.GetCapabilitiesIndex(cachememdb.IndexNameID, indexId)
+	require.NoError(t, err)
+	require.NotNil(t, newIndex)
+
+	// Forcefully stop any remaining workers
+	sscm.workerPool.Stop()
+}
+
+// TestSubmitWorkSealedVaultPessimistic tests that the capability manager
+// behaves as expected when
+// sscm.tokenCapabilityRefreshBehaviour == TokenCapabilityRefreshBehaviourPessimistic
+func TestSubmitWorkSealedVaultPessimistic(t *testing.T) {
+	t.Parallel()
+	cluster := minimal.NewTestSoloCluster(t, nil)
+	client := cluster.Cores[0].Client
+
+	token := "not real token"
+	indexId := hashStaticSecretIndex(token)
+
+	sscm := testNewStaticSecretCapabilityManager(t, client)
+	sscm.tokenCapabilityRefreshBehaviour = TokenCapabilityRefreshBehaviourPessimistic
+
+	index := &cachememdb.CapabilitiesIndex{
+		ID:    indexId,
+		Token: token,
+		ReadablePaths: map[string]struct{}{
+			"foo/bar":                {},
+			"auth/token/lookup-self": {},
+		},
+	}
+	err := sscm.leaseCache.db.SetCapabilitiesIndex(index)
+	require.Nil(t, err)
+
+	// Seal the cluster
+	cluster.EnsureCoresSealed(t)
+
+	sscm.StartRenewingCapabilities(index)
+
+	// Wait for the job to complete at least once...
+	time.Sleep(3 * time.Second)
+
+	// This entry should be evicted.
+	newIndex, err := sscm.leaseCache.db.GetCapabilitiesIndex(cachememdb.IndexNameID, indexId)
+	require.Error(t, err)
+	require.Nil(t, newIndex)
+
+	// Forcefully stop any remaining workers
+	sscm.workerPool.Stop()
+}
+
 // TestSubmitWorkUpdatesAllIndexes tests that an index will be correctly updated if the capabilities differ, as
 // well as the indexes related to the paths that are being checked for.
 func TestSubmitWorkUpdatesAllIndexes(t *testing.T) {

command/proxy.go

@@ -520,7 +520,8 @@ func (c *ProxyCommand) Run(args []string) int {
 				LeaseCache: leaseCache,
 				Logger:     c.logger.Named("cache.staticsecretcapabilitymanager"),
 				Client:     client,
-				StaticSecretTokenCapabilityRefreshInterval: config.Cache.StaticSecretTokenCapabilityRefreshInterval,
+				StaticSecretTokenCapabilityRefreshInterval:  config.Cache.StaticSecretTokenCapabilityRefreshInterval,
+				StaticSecretTokenCapabilityRefreshBehaviour: config.Cache.StaticSecretTokenCapabilityRefreshBehaviour,
 			})
 			if err != nil {
 				c.UI.Error(fmt.Sprintf("Error creating static secret capability manager: %v", err))

command/proxy/config/config.go

@@ -109,6 +109,7 @@ type Cache struct {
 	DisableCachingDynamicSecrets                  bool                            `hcl:"disable_caching_dynamic_secrets"`
 	StaticSecretTokenCapabilityRefreshIntervalRaw interface{}                     `hcl:"static_secret_token_capability_refresh_interval"`
 	StaticSecretTokenCapabilityRefreshInterval    time.Duration                   `hcl:"-"`
+	StaticSecretTokenCapabilityRefreshBehaviour   string                          `hcl:"static_secret_token_capability_refresh_behavior"`
 }
 
 // AutoAuth is the configured authentication method and sinks
@@ -271,6 +272,15 @@ func (c *Config) ValidateConfig() error {
 		return fmt.Errorf("no auto_auth, cache, or listener block found in config")
 	}
 
+	if c.Cache != nil && c.Cache.StaticSecretTokenCapabilityRefreshBehaviour != "" {
+		switch c.Cache.StaticSecretTokenCapabilityRefreshBehaviour {
+		case "pessimistic":
+		case "optimistic":
+		default:
+			return fmt.Errorf("cache.static_secret_token_capability_refresh_behavior must be either \"optimistic\" or \"pessimistic\"")
+		}
+	}
+
 	return nil
 }
 

website/content/docs/agent-and-proxy/proxy/caching/static-secret-caching.mdx

@@ -104,6 +104,14 @@ token can no longer access the relevant paths from the cache. The refresh interv
 is essentially the maximum period after which permission to read a KV secret is
 fully revoked for the relevant token.
 
+If the capabilities have been removed, or Proxy receives a `403` response, the
+capability is removed from the token, and that token cannot be used to access the
+cache. For other kinds of errors, such as Vault being unreachable or sealed,
+the `static_secret_token_capability_refresh_behavior` config is consulted.
+If set to `optimistic` (the default), the capability will not be removed unless we
+receive a `403` or valid response without the capability. If set to `pessimistic`,
+the capability will be removed for any error, such as would occur if Vault is sealed.
+
 For token refresh to work, any token that will access the cache also needs
 `update` permission for [`sys/capabilies-self`](/vault/api-docs/system/capabilities-self).
 Having `update` permission for the token lets Proxy test capabilities for the
@@ -149,6 +157,16 @@ secrets. The refresh interval is the maximum period after which permission to
 read a cached KV secret is fully revoked. Ignored when `cache_static_secrets`
 is `false`.
 
+- `static_secret_token_capability_refresh_behavior` `(string: "optimistic", optional)` -
+Sets the capability refresh behavior in the case of an error when attempting to
+refresh capabilities. In the case of a `403`, capabilities will be removed for the token
+with either option. In case of other errors, such as Vault being sealed or Vault being
+unavailable, this setting controls the behavior. If set to `optimistic` (the default),
+capabilities will be removed for only `403` errors. If set to `pessimistic`, capabilities
+will be removed for any error. This essentially allows configuring a preference between
+favoring availability (`optimistic`) or access fidelity (`pessimistic`) of cached
+static secrets. Ignored when `cache_static_secrets` is `false`.
+
 ### Example configuration
 
 The following example Vault Proxy configuration: