More key tweaks (#1116)

internal/caching/cache_serverkeys.go

@@ -2,6 +2,7 @@ package caching
 
 import (
 	"fmt"
+	"time"
 
 	"github.com/matrix-org/gomatrixserverlib"
 )
@@ -23,9 +24,17 @@ func (c Caches) GetServerKey(
 	request gomatrixserverlib.PublicKeyLookupRequest,
 ) (gomatrixserverlib.PublicKeyLookupResult, bool) {
 	key := fmt.Sprintf("%s/%s", request.ServerName, request.KeyID)
+	now := gomatrixserverlib.AsTimestamp(time.Now())
 	val, found := c.ServerKeys.Get(key)
 	if found && val != nil {
 		if keyLookupResult, ok := val.(gomatrixserverlib.PublicKeyLookupResult); ok {
+			if !keyLookupResult.WasValidAt(now, true) {
+				// We appear to be past the key validity so don't return this
+				// with the results. This ensures that the cache doesn't return
+				// values that are not useful to us.
+				c.ServerKeys.Unset(key)
+				return gomatrixserverlib.PublicKeyLookupResult{}, false
+			}
 			return keyLookupResult, true
 		}
 	}

internal/caching/caches.go

@@ -12,4 +12,5 @@ type Caches struct {
 type Cache interface {
 	Get(key string) (value interface{}, ok bool)
 	Set(key string, value interface{})
+	Unset(key string)
 }

internal/caching/impl_inmemorylru.go

@@ -68,6 +68,13 @@ func (c *InMemoryLRUCachePartition) Set(key string, value interface{}) {
 	c.lru.Add(key, value)
 }
 
+func (c *InMemoryLRUCachePartition) Unset(key string) {
+	if !c.mutable {
+		panic(fmt.Sprintf("invalid use of immutable cache tries to unset value of %q", key))
+	}
+	c.lru.Remove(key)
+}
+
 func (c *InMemoryLRUCachePartition) Get(key string) (value interface{}, ok bool) {
 	return c.lru.Get(key)
 }