Fix an issue where we would send an invalid /user/keys/query request

fclient/federationclient.go

@@ -633,7 +633,13 @@ func (ac *federationClient) ClaimKeys(ctx context.Context, origin, s spec.Server
 func (ac *federationClient) QueryKeys(ctx context.Context, origin, s spec.ServerName, keys map[string][]string) (res RespQueryKeys, err error) {
 	path := federationPathPrefixV1 + "/user/keys/query"
 	req := NewFederationRequest("POST", origin, s, path)
-	if err = req.SetContent(map[string]interface{}{
+	// Ensure that the keys map has empty slices for any nil values.
+	for k, v := range keys {
+		if v == nil {
+			keys[k] = []string{}
+		}
+	}
+	if err = req.SetContent(map[string]map[string][]string{
 		"device_keys": keys,
 	}); err != nil {
 		return

fclient/federationclient_test.go

@@ -282,3 +282,125 @@ func jsonify(x interface{}) string {
 	b, _ := json.Marshal(x)
 	return string(b)
 }
+
+func TestQueryKeysReturnsDeviceKeys(t *testing.T) {
+	serverName := spec.ServerName("local.server.name")
+	targetServerName := spec.ServerName("target.server.name")
+	keyID := gomatrixserverlib.KeyID("ed25519:auto")
+	_, privateKey, _ := ed25519.GenerateKey(nil)
+
+	respQueryKeysJSON := []byte(`{
+		"device_keys": {
+			"@user:target.server.name": {
+				"device1": {
+					"algorithms": ["m.olm.curve25519-aes-sha2"],
+					"keys": {
+						"curve25519:device1": "key1",
+						"ed25519:device1": "key2"
+					}
+				}
+			}
+		}
+	}`)
+
+	fc := fclient.NewFederationClient(
+		[]*fclient.SigningIdentity{
+			{
+				ServerName: serverName,
+				KeyID:      keyID,
+				PrivateKey: privateKey,
+			},
+		},
+		fclient.WithSkipVerify(true),
+		fclient.WithTransport(
+			&roundTripper{
+				fn: func(req *http.Request) (*http.Response, error) {
+					if strings.HasPrefix(req.URL.Path, "/_matrix/federation/v1/user/keys/query") {
+						body, err := io.ReadAll(req.Body)
+						if err != nil {
+							return nil, fmt.Errorf("failed to read request body: %w", err)
+						}
+						if bytes.Contains(body, []byte("null")) {
+							t.Fatalf("QueryKeys request body should not contain 'null': %s", string(body))
+						}
+						return &http.Response{
+							StatusCode: 200,
+							Body:       io.NopCloser(bytes.NewReader(respQueryKeysJSON)),
+						}, nil
+					}
+					return &http.Response{
+						StatusCode: 404,
+						Body:       io.NopCloser(strings.NewReader("404 not found")),
+					}, nil
+				},
+			},
+		),
+	)
+
+	keys := map[string][]string{
+		"@user:target.server.name": {"device1"},
+	}
+	res, err := fc.QueryKeys(context.Background(), serverName, targetServerName, keys)
+	if err != nil {
+		t.Fatalf("QueryKeys returned an error: %s", err)
+	}
+	if len(res.DeviceKeys["@user:target.server.name"]["device1"].Keys) == 0 {
+		t.Fatalf("QueryKeys response missing device keys")
+	}
+}
+
+func TestQueryKeysHandlesNilDeviceKeys(t *testing.T) {
+	serverName := spec.ServerName("local.server.name")
+	targetServerName := spec.ServerName("target.server.name")
+	keyID := gomatrixserverlib.KeyID("ed25519:auto")
+	_, privateKey, _ := ed25519.GenerateKey(nil)
+
+	respQueryKeysJSON := []byte(`{
+		"device_keys": {}
+	}`)
+
+	fc := fclient.NewFederationClient(
+		[]*fclient.SigningIdentity{
+			{
+				ServerName: serverName,
+				KeyID:      keyID,
+				PrivateKey: privateKey,
+			},
+		},
+		fclient.WithSkipVerify(true),
+		fclient.WithTransport(
+			&roundTripper{
+				fn: func(req *http.Request) (*http.Response, error) {
+					if strings.HasPrefix(req.URL.Path, "/_matrix/federation/v1/user/keys/query") {
+						body, err := io.ReadAll(req.Body)
+						if err != nil {
+							return nil, fmt.Errorf("failed to read request body: %w", err)
+						}
+						if bytes.Contains(body, []byte("null")) {
+							t.Fatalf("QueryKeys request body should not contain 'null': %s", string(body))
+						}
+						return &http.Response{
+							StatusCode: 200,
+							Body:       io.NopCloser(bytes.NewReader(respQueryKeysJSON)),
+						}, nil
+					}
+					return &http.Response{
+						StatusCode: 404,
+						Body:       io.NopCloser(strings.NewReader("404 not found")),
+					}, nil
+				},
+			},
+		),
+	)
+
+	keys := map[string][]string{
+		"@user:target.server.name": nil,
+	}
+	res, err := fc.QueryKeys(context.Background(), serverName, targetServerName, keys)
+	if err != nil {
+		t.Fatalf("QueryKeys returned an error: %s", err)
+	}
+	if len(res.DeviceKeys) != 0 {
+		t.Fatalf("QueryKeys response should be empty for nil device keys")
+	}
+}