Support for m.login.token (#2014)

* Add GOPATH to PATH in find-lint.sh.

The user doesn't necessarily have it in PATH.

* Refactor LoginTypePassword and Type to support m.login.token and m.login.sso.

For login token:

* m.login.token will require deleting the token after completeAuth has
  generated an access token, so a cleanup function is returned by
  Type.Login.
* Allowing different login types will require parsing the /login body
  twice: first to extract the "type" and then the type-specific parsing.
  Thus, we will have to buffer the request JSON in /login, like
  UserInteractive already does.

For SSO:

* NewUserInteractive will have to also use GetAccountByLocalpart. It
  makes more sense to just pass a (narrowed-down) accountDB interface
  to it than adding more function pointers.

Code quality:

* Passing around (and down-casting) interface{} for login request types
  has drawbacks in terms of type-safety, and no inherent benefits. We
  always decode JSON anyway. Hence renaming to Type.LoginFromJSON. Code
  that directly uses LoginTypePassword with parsed data can still use
  Login.
* Removed a TODO for SSO. This is already tracked in #1297.
* httputil.UnmarshalJSON is useful because it returns a JSONResponse.

This change is intended to have no functional changes.

* Support login tokens in User API.

This adds full lifecycle functions for login tokens: create, query, delete.

* Support m.login.token in /login.

* Fixes for PR review.

* Set @matrix-org/dendrite-core as repository code owner

* Return event NID from `StoreEvent`, match PSQL vs SQLite behaviour, tweak backfill persistence (#2071)

Co-authored-by: kegsay <kegan@matrix.org>
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

userapi/internal/api_logintoken.go

@@ -0,0 +1,78 @@
+// Copyright 2021 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 internal
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	"github.com/matrix-org/dendrite/userapi/api"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+)
+
+// PerformLoginTokenCreation creates a new login token and associates it with the provided data.
+func (a *UserInternalAPI) PerformLoginTokenCreation(ctx context.Context, req *api.PerformLoginTokenCreationRequest, res *api.PerformLoginTokenCreationResponse) error {
+	util.GetLogger(ctx).WithField("user_id", req.Data.UserID).Info("PerformLoginTokenCreation")
+	_, domain, err := gomatrixserverlib.SplitID('@', req.Data.UserID)
+	if err != nil {
+		return err
+	}
+	if domain != a.ServerName {
+		return fmt.Errorf("cannot create a login token for a remote user: got %s want %s", domain, a.ServerName)
+	}
+	tokenMeta, err := a.DeviceDB.CreateLoginToken(ctx, &req.Data)
+	if err != nil {
+		return err
+	}
+	res.Metadata = *tokenMeta
+	return nil
+}
+
+// PerformLoginTokenDeletion ensures the token doesn't exist.
+func (a *UserInternalAPI) PerformLoginTokenDeletion(ctx context.Context, req *api.PerformLoginTokenDeletionRequest, res *api.PerformLoginTokenDeletionResponse) error {
+	util.GetLogger(ctx).Info("PerformLoginTokenDeletion")
+	return a.DeviceDB.RemoveLoginToken(ctx, req.Token)
+}
+
+// QueryLoginToken returns the data associated with a login token. If
+// the token is not valid, success is returned, but res.Data == nil.
+func (a *UserInternalAPI) QueryLoginToken(ctx context.Context, req *api.QueryLoginTokenRequest, res *api.QueryLoginTokenResponse) error {
+	tokenData, err := a.DeviceDB.GetLoginTokenDataByToken(ctx, req.Token)
+	if err != nil {
+		res.Data = nil
+		if err == sql.ErrNoRows {
+			return nil
+		}
+		return err
+	}
+	localpart, domain, err := gomatrixserverlib.SplitID('@', tokenData.UserID)
+	if err != nil {
+		return err
+	}
+	if domain != a.ServerName {
+		return fmt.Errorf("cannot return a login token for a remote user: got %s want %s", domain, a.ServerName)
+	}
+	if _, err := a.AccountDB.GetAccountByLocalpart(ctx, localpart); err != nil {
+		res.Data = nil
+		if err == sql.ErrNoRows {
+			return nil
+		}
+		return err
+	}
+	res.Data = tokenData
+	return nil
+}