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.

clientapi/auth/auth.go

@@ -42,6 +42,7 @@ type DeviceDatabase interface {
 type AccountDatabase interface {
 	// Look up the account matching the given localpart.
 	GetAccountByLocalpart(ctx context.Context, localpart string) (*api.Account, error)
+	GetAccountByPassword(ctx context.Context, localpart, password string) (*api.Account, error)
 }
 
 // VerifyUserFromRequest authenticates the HTTP request,

clientapi/auth/password.go

@@ -19,6 +19,8 @@ import (
 	"net/http"
 	"strings"
 
+	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
+	"github.com/matrix-org/dendrite/clientapi/httputil"
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/dendrite/clientapi/userutil"
 	"github.com/matrix-org/dendrite/setup/config"
@@ -40,16 +42,24 @@ type LoginTypePassword struct {
 }
 
 func (t *LoginTypePassword) Name() string {
-	return "m.login.password"
+	return authtypes.LoginTypePassword
 }
 
-func (t *LoginTypePassword) Request() interface{} {
-	return &PasswordRequest{}
+func (t *LoginTypePassword) LoginFromJSON(ctx context.Context, reqBytes []byte) (*Login, LoginCleanupFunc, *util.JSONResponse) {
+	var r PasswordRequest
+	if err := httputil.UnmarshalJSON(reqBytes, &r); err != nil {
+		return nil, nil, err
+	}
+
+	login, err := t.Login(ctx, &r)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return login, func(context.Context, *util.JSONResponse) {}, nil
 }
 
-func (t *LoginTypePassword) Login(ctx context.Context, req interface{}) (*Login, *util.JSONResponse) {
-	r := req.(*PasswordRequest)
-	// Squash username to all lowercase letters
+func (t *LoginTypePassword) Login(ctx context.Context, r *PasswordRequest) (*Login, *util.JSONResponse) {
 	username := strings.ToLower(r.Username())
 	if username == "" {
 		return nil, &util.JSONResponse{

clientapi/auth/user_interactive.go

@@ -32,22 +32,24 @@ import (
 type Type interface {
 	// Name returns the name of the auth type e.g `m.login.password`
 	Name() string
-	// Request returns a pointer to a new request body struct to unmarshal into.
-	Request() interface{}
 	// Login with the auth type, returning an error response on failure.
 	// Not all types support login, only m.login.password and m.login.token
 	// See https://matrix.org/docs/spec/client_server/r0.6.1#post-matrix-client-r0-login
-	// `req` is guaranteed to be the type returned from Request()
 	// This function will be called when doing login and when doing 'sudo' style
 	// actions e.g deleting devices. The response must be a 401 as per:
 	// "If the homeserver decides that an attempt on a stage was unsuccessful, but the
 	// client may make a second attempt, it returns the same HTTP status 401 response as above,
 	// with the addition of the standard errcode and error fields describing the error."
-	Login(ctx context.Context, req interface{}) (login *Login, errRes *util.JSONResponse)
+	//
+	// The returned cleanup function must be non-nil on success, and will be called after
+	// authorization has been completed. Its argument is the final result of authorization.
+	LoginFromJSON(ctx context.Context, reqBytes []byte) (login *Login, cleanup LoginCleanupFunc, errRes *util.JSONResponse)
 	// TODO: Extend to support Register() flow
 	// Register(ctx context.Context, sessionID string, req interface{})
 }
 
+type LoginCleanupFunc func(context.Context, *util.JSONResponse)
+
 // LoginIdentifier represents identifier types
 // https://matrix.org/docs/spec/client_server/r0.6.1#identifier-types
 type LoginIdentifier struct {
@@ -111,12 +113,11 @@ type UserInteractive struct {
 	Sessions map[string][]string
 }
 
-func NewUserInteractive(getAccByPass GetAccountByPassword, cfg *config.ClientAPI) *UserInteractive {
+func NewUserInteractive(accountDB AccountDatabase, cfg *config.ClientAPI) *UserInteractive {
 	typePassword := &LoginTypePassword{
-		GetAccountByPassword: getAccByPass,
+		GetAccountByPassword: accountDB.GetAccountByPassword,
 		Config:               cfg,
 	}
-	// TODO: Add SSO login
 	return &UserInteractive{
 		Completed: []string{},
 		Flows: []userInteractiveFlow{
@@ -236,18 +237,13 @@ func (u *UserInteractive) Verify(ctx context.Context, bodyBytes []byte, device *
 		}
 	}
 
-	r := loginType.Request()
-	if err := json.Unmarshal([]byte(gjson.GetBytes(bodyBytes, "auth").Raw), r); err != nil {
-		return nil, &util.JSONResponse{
-			Code: http.StatusBadRequest,
-			JSON: jsonerror.BadJSON("The request body could not be decoded into valid JSON. " + err.Error()),
-		}
+	login, cleanup, resErr := loginType.LoginFromJSON(ctx, []byte(gjson.GetBytes(bodyBytes, "auth").Raw))
+	if resErr != nil {
+		return nil, u.ResponseWithChallenge(sessionID, resErr.JSON)
 	}
-	login, resErr := loginType.Login(ctx, r)
-	if resErr == nil {
-		u.AddCompletedStage(sessionID, authType)
-		// TODO: Check if there's more stages to go and return an error
-		return login, nil
-	}
-	return nil, u.ResponseWithChallenge(sessionID, resErr.JSON)
+
+	u.AddCompletedStage(sessionID, authType)
+	cleanup(ctx, nil)
+	// TODO: Check if there's more stages to go and return an error
+	return login, nil
 }

clientapi/auth/user_interactive_test.go

@@ -24,7 +24,11 @@ var (
 	}
 )
 
-func getAccountByPassword(ctx context.Context, localpart, plaintextPassword string) (*api.Account, error) {
+type fakeAccountDatabase struct {
+	AccountDatabase
+}
+
+func (*fakeAccountDatabase) GetAccountByPassword(ctx context.Context, localpart, plaintextPassword string) (*api.Account, error) {
 	acc, ok := lookup[localpart+" "+plaintextPassword]
 	if !ok {
 		return nil, fmt.Errorf("unknown user/password")
@@ -38,7 +42,7 @@ func setup() *UserInteractive {
 			ServerName: serverName,
 		},
 	}
-	return NewUserInteractive(getAccountByPassword, cfg)
+	return NewUserInteractive(&fakeAccountDatabase{}, cfg)
 }
 
 func TestUserInteractiveChallenge(t *testing.T) {

clientapi/httputil/httputil.go

@@ -36,6 +36,10 @@ func UnmarshalJSONRequest(req *http.Request, iface interface{}) *util.JSONRespon
 		return &resp
 	}
 
+	return UnmarshalJSON(body, iface)
+}
+
+func UnmarshalJSON(body []byte, iface interface{}) *util.JSONResponse {
 	if !utf8.Valid(body) {
 		return &util.JSONResponse{
 			Code: http.StatusBadRequest,

clientapi/routing/login.go

@@ -16,10 +16,10 @@ package routing
 
 import (
 	"context"
+	"io/ioutil"
 	"net/http"
 
 	"github.com/matrix-org/dendrite/clientapi/auth"
-	"github.com/matrix-org/dendrite/clientapi/httputil"
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/dendrite/clientapi/userutil"
 	"github.com/matrix-org/dendrite/setup/config"
@@ -69,17 +69,21 @@ func Login(
 			GetAccountByPassword: accountDB.GetAccountByPassword,
 			Config:               cfg,
 		}
-		r := typePassword.Request()
-		resErr := httputil.UnmarshalJSONRequest(req, r)
-		if resErr != nil {
-			return *resErr
+		body, err := ioutil.ReadAll(req.Body)
+		if err != nil {
+			return util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.BadJSON("Reading request body failed: " + err.Error()),
+			}
 		}
-		login, authErr := typePassword.Login(req.Context(), r)
+		login, cleanup, authErr := typePassword.LoginFromJSON(req.Context(), body)
 		if authErr != nil {
 			return *authErr
 		}
 		// make a device/access token
-		return completeAuth(req.Context(), cfg.Matrix.ServerName, userAPI, login, req.RemoteAddr, req.UserAgent())
+		authzErr := completeAuth(req.Context(), cfg.Matrix.ServerName, userAPI, login, req.RemoteAddr, req.UserAgent())
+		cleanup(req.Context(), &authzErr)
+		return authzErr
 	}
 	return util.JSONResponse{
 		Code: http.StatusMethodNotAllowed,

clientapi/routing/routing.go

@@ -62,7 +62,7 @@ func Setup(
 	mscCfg *config.MSCs,
 ) {
 	rateLimits := httputil.NewRateLimits(&cfg.RateLimiting)
-	userInteractiveAuth := auth.NewUserInteractive(accountDB.GetAccountByPassword, cfg)
+	userInteractiveAuth := auth.NewUserInteractive(accountDB, cfg)
 
 	unstableFeatures := map[string]bool{
 		"org.matrix.e2e_cross_signing": true,