set cache default values as documented (#460)

This commit fixes a two bugs in the cache configuration logic.

  1. KES now applies a default cache configuration as documented here:
     https://github.com/minio/kes/blob/master/server-config.yaml#L147

  2. KES now removes entry from the offline cache if no offline cache
     expiry is specified. Before, KES used to not clear the cache if
     no offline cache configuration has been specified (docs claim that
     KES disables offline caching without explicit configuration).

Signed-off-by: Andreas Auernhammer <github@aead.dev>

cmd/kes/server.go

@@ -181,6 +181,7 @@ func startServer(addrFlag, configFlag string) error {
 	defer conf.Keys.Close()
 
 	srv := &kes.Server{}
+	conf.Cache = configureCache(conf.Cache)
 	if rawConfig.Log != nil {
 		srv.ErrLevel.Set(rawConfig.Log.ErrLevel)
 		srv.AuditLevel.Set(rawConfig.Log.AuditLevel)
@@ -242,6 +243,7 @@ func startServer(addrFlag, configFlag string) error {
 					fmt.Fprintf(os.Stderr, "Failed to reload server config: %v\n", err)
 					continue
 				}
+				config.Cache = configureCache(config.Cache)
 
 				closer, err := srv.Update(config)
 				if err != nil {
@@ -345,8 +347,12 @@ func startDevServer(addr string) error {
 	conf := &kes.Config{
 		Admin: apiKey.Identity(),
 		TLS:   tlsConf,
-		Cache: &kes.CacheConfig{},
-		Keys:  &kes.MemKeyStore{},
+		Cache: &kes.CacheConfig{
+			Expiry:        5 * time.Minute,
+			ExpiryUnused:  30 * time.Second,
+			ExpiryOffline: 0,
+		},
+		Keys: &kes.MemKeyStore{},
 	}
 	srv := &kes.Server{}
 
@@ -382,6 +388,21 @@ func startDevServer(addr string) error {
 	return nil
 }
 
+// configureCache sets default values for each cache config option
+// as documented in: https://github.com/minio/kes/blob/master/server-config.yaml
+func configureCache(c *kes.CacheConfig) *kes.CacheConfig {
+	if c == nil {
+		c = &kes.CacheConfig{}
+	}
+	if c.Expiry == 0 {
+		c.Expiry = 5 * time.Minute
+	}
+	if c.ExpiryUnused == 0 {
+		c.Expiry = 30 * time.Second
+	}
+	return c
+}
+
 // lookupInterfaceIPs returns a list of IP addrs for which a listener
 // listening on listenerIP is reachable. If listenerIP is not
 // unspecified (0.0.0.0) it returns []net.IP{listenerIP}.

keystore.go

@@ -172,13 +172,14 @@ func newCache(store KeyStore, conf *CacheConfig) *keyCache {
 		stop:  stop,
 	}
 
+	expiryOffline := conf.ExpiryOffline
 	go c.gc(ctx, conf.Expiry, func() {
-		if offline := c.offline.Load(); !offline {
+		if offline := c.offline.Load(); !offline || expiryOffline <= 0 {
 			c.cache.DeleteAll()
 		}
 	})
 	go c.gc(ctx, conf.ExpiryUnused/2, func() {
-		if offline := c.offline.Load(); !offline {
+		if offline := c.offline.Load(); !offline || conf.ExpiryOffline <= 0 {
 			c.cache.DeleteFunc(func(_ string, e *cacheEntry) bool {
 				// We remove an entry if it isn't marked as used.
 				// We also change all other entries to unused such
@@ -195,7 +196,7 @@ func newCache(store KeyStore, conf *CacheConfig) *keyCache {
 		}
 	})
 	go c.gc(ctx, conf.ExpiryOffline, func() {
-		if offline := c.offline.Load(); offline {
+		if offline := c.offline.Load(); offline && expiryOffline > 0 {
 			c.cache.DeleteAll()
 		}
 	})