Server key component (#1050)

* Server key API (works for monolith but not for polylith yet)

* Re-enable caching on server key API component

* Groundwork for HTTP APIs for server key API

* Hopefully implement HTTP for server key API

* Simplify public key request marshalling from map keys

* Update gomatrixserverlib

* go mod tidy

* Common -> internal

* remove keyring.go

* Update Docker Hub for server key API

* YAML is funny about indentation

* Wire in new server key API into hybrid monolith mode

* Create maps

* Route server key API endpoints on internal API mux

* Fix server key API URLs

* Add fetcher behaviour into server key API implementation

* Return error if we failed to fetch some keys

* Return results anyway

* Move things about a bit

* Remove unused code

* Fix comments, don't use federation sender URL in polylith mode

* Add server_key_api to sample config

* Review comments

* HTTP API to cache keys that have been requested

* Overwrite server_key_api listen in monolith hybrid mode

serverkeyapi/api/api.go

@@ -0,0 +1,113 @@
+package api
+
+import (
+	"context"
+	"errors"
+	"net/http"
+
+	"github.com/matrix-org/dendrite/internal/caching"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+type ServerKeyInternalAPI interface {
+	gomatrixserverlib.KeyDatabase
+
+	KeyRing() *gomatrixserverlib.KeyRing
+
+	InputPublicKeys(
+		ctx context.Context,
+		request *InputPublicKeysRequest,
+		response *InputPublicKeysResponse,
+	) error
+
+	QueryPublicKeys(
+		ctx context.Context,
+		request *QueryPublicKeysRequest,
+		response *QueryPublicKeysResponse,
+	) error
+}
+
+// NewRoomserverInputAPIHTTP creates a RoomserverInputAPI implemented by talking to a HTTP POST API.
+// If httpClient is nil an error is returned
+func NewServerKeyInternalAPIHTTP(
+	serverKeyAPIURL string,
+	httpClient *http.Client,
+	immutableCache caching.ImmutableCache,
+) (ServerKeyInternalAPI, error) {
+	if httpClient == nil {
+		return nil, errors.New("NewRoomserverInternalAPIHTTP: httpClient is <nil>")
+	}
+	return &httpServerKeyInternalAPI{
+		serverKeyAPIURL: serverKeyAPIURL,
+		httpClient:      httpClient,
+		immutableCache:  immutableCache,
+	}, nil
+}
+
+type httpServerKeyInternalAPI struct {
+	ServerKeyInternalAPI
+
+	serverKeyAPIURL string
+	httpClient      *http.Client
+	immutableCache  caching.ImmutableCache
+}
+
+func (s *httpServerKeyInternalAPI) KeyRing() *gomatrixserverlib.KeyRing {
+	// This is a bit of a cheat - we tell gomatrixserverlib that this API is
+	// both the key database and the key fetcher. While this does have the
+	// rather unfortunate effect of preventing gomatrixserverlib from handling
+	// key fetchers directly, we can at least reimplement this behaviour on
+	// the other end of the API.
+	return &gomatrixserverlib.KeyRing{
+		KeyDatabase: s,
+		KeyFetchers: []gomatrixserverlib.KeyFetcher{s},
+	}
+}
+
+func (s *httpServerKeyInternalAPI) FetcherName() string {
+	return "httpServerKeyInternalAPI"
+}
+
+func (s *httpServerKeyInternalAPI) StoreKeys(
+	ctx context.Context,
+	results map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult,
+) error {
+	request := InputPublicKeysRequest{
+		Keys: make(map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult),
+	}
+	response := InputPublicKeysResponse{}
+	for req, res := range results {
+		request.Keys[req] = res
+		s.immutableCache.StoreServerKey(req, res)
+	}
+	return s.InputPublicKeys(ctx, &request, &response)
+}
+
+func (s *httpServerKeyInternalAPI) FetchKeys(
+	ctx context.Context,
+	requests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp,
+) (map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult, error) {
+	result := make(map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult)
+	request := QueryPublicKeysRequest{
+		Requests: make(map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp),
+	}
+	response := QueryPublicKeysResponse{
+		Results: make(map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult),
+	}
+	for req, ts := range requests {
+		if res, ok := s.immutableCache.GetServerKey(req); ok {
+			result[req] = res
+			continue
+		}
+		request.Requests[req] = ts
+	}
+	err := s.QueryPublicKeys(ctx, &request, &response)
+	if err != nil {
+		return nil, err
+	}
+	for req, res := range response.Results {
+		result[req] = res
+		s.immutableCache.StoreServerKey(req, res)
+	}
+	return result, nil
+}