Improvements to Yggdrasil demo (#1114)

* Improvements to Yggdrasil demo

* Fix missing copyright

* Fix tie-break

cmd/dendrite-demo-yggdrasil/signing/fetcher.go

@@ -0,0 +1,69 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package signing
+
+import (
+	"context"
+	"encoding/hex"
+	"fmt"
+	"time"
+
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+const KeyID = "ed25519:dendrite-demo-yggdrasil"
+
+type YggdrasilKeys struct {
+}
+
+func (f *YggdrasilKeys) KeyRing() *gomatrixserverlib.KeyRing {
+	return &gomatrixserverlib.KeyRing{
+		KeyDatabase: f,
+	}
+}
+
+func (f *YggdrasilKeys) FetchKeys(
+	ctx context.Context,
+	requests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp,
+) (map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult, error) {
+	res := make(map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult)
+	for req := range requests {
+		if req.KeyID != KeyID {
+			return nil, fmt.Errorf("FetchKeys: cannot fetch key with ID %s, should be %s", req.KeyID, KeyID)
+		}
+
+		hexkey, err := hex.DecodeString(string(req.ServerName))
+		if err != nil {
+			return nil, fmt.Errorf("FetchKeys: can't decode server name %q: %w", req.ServerName, err)
+		}
+
+		res[req] = gomatrixserverlib.PublicKeyLookupResult{
+			VerifyKey: gomatrixserverlib.VerifyKey{
+				Key: hexkey,
+			},
+			ExpiredTS:    gomatrixserverlib.PublicKeyNotExpired,
+			ValidUntilTS: gomatrixserverlib.AsTimestamp(time.Now().Add(24 * time.Hour * 365)),
+		}
+	}
+	return res, nil
+}
+
+func (f *YggdrasilKeys) FetcherName() string {
+	return "YggdrasilKeys"
+}
+
+func (f *YggdrasilKeys) StoreKeys(ctx context.Context, results map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult) error {
+	return nil
+}