Add clientapi tests (#2916)

This PR
- adds several tests for the clientapi, mostly around `/register` and
auth fallback.
- removes the now deprecated `homeserver` field from responses to
`/register` and `/login`
- slightly refactors auth fallback handling

clientapi/routing/auth_fallback.go

@@ -15,11 +15,11 @@
 package routing
 
 import (
+	"fmt"
 	"html/template"
 	"net/http"
 
 	"github.com/matrix-org/dendrite/clientapi/auth/authtypes"
-	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/util"
 )
@@ -101,14 +101,28 @@ func serveTemplate(w http.ResponseWriter, templateHTML string, data map[string]s
 func AuthFallback(
 	w http.ResponseWriter, req *http.Request, authType string,
 	cfg *config.ClientAPI,
-) *util.JSONResponse {
-	sessionID := req.URL.Query().Get("session")
+) {
+	// We currently only support "m.login.recaptcha", so fail early if that's not requested
+	if authType == authtypes.LoginTypeRecaptcha {
+		if !cfg.RecaptchaEnabled {
+			writeHTTPMessage(w, req,
+				"Recaptcha login is disabled on this Homeserver",
+				http.StatusBadRequest,
+			)
+			return
+		}
+	} else {
+		writeHTTPMessage(w, req, fmt.Sprintf("Unknown authtype %q", authType), http.StatusNotImplemented)
+		return
+	}
 
+	sessionID := req.URL.Query().Get("session")
 	if sessionID == "" {
-		return writeHTTPMessage(w, req,
+		writeHTTPMessage(w, req,
 			"Session ID not provided",
 			http.StatusBadRequest,
 		)
+		return
 	}
 
 	serveRecaptcha := func() {
@@ -130,70 +144,44 @@ func AuthFallback(
 
 	if req.Method == http.MethodGet {
 		// Handle Recaptcha
-		if authType == authtypes.LoginTypeRecaptcha {
-			if err := checkRecaptchaEnabled(cfg, w, req); err != nil {
-				return err
-			}
-
-			serveRecaptcha()
-			return nil
-		}
-		return &util.JSONResponse{
-			Code: http.StatusNotFound,
-			JSON: jsonerror.NotFound("Unknown auth stage type"),
-		}
+		serveRecaptcha()
+		return
 	} else if req.Method == http.MethodPost {
 		// Handle Recaptcha
-		if authType == authtypes.LoginTypeRecaptcha {
-			if err := checkRecaptchaEnabled(cfg, w, req); err != nil {
-				return err
-			}
-
-			clientIP := req.RemoteAddr
-			err := req.ParseForm()
-			if err != nil {
-				util.GetLogger(req.Context()).WithError(err).Error("req.ParseForm failed")
-				res := jsonerror.InternalServerError()
-				return &res
-			}
-
-			response := req.Form.Get(cfg.RecaptchaFormField)
-			if err := validateRecaptcha(cfg, response, clientIP); err != nil {
-				util.GetLogger(req.Context()).Error(err)
-				return err
-			}
-
-			// Success. Add recaptcha as a completed login flow
-			sessions.addCompletedSessionStage(sessionID, authtypes.LoginTypeRecaptcha)
-
-			serveSuccess()
-			return nil
+		clientIP := req.RemoteAddr
+		err := req.ParseForm()
+		if err != nil {
+			util.GetLogger(req.Context()).WithError(err).Error("req.ParseForm failed")
+			w.WriteHeader(http.StatusBadRequest)
+			serveRecaptcha()
+			return
 		}
 
-		return &util.JSONResponse{
-			Code: http.StatusNotFound,
-			JSON: jsonerror.NotFound("Unknown auth stage type"),
+		response := req.Form.Get(cfg.RecaptchaFormField)
+		err = validateRecaptcha(cfg, response, clientIP)
+		switch err {
+		case ErrMissingResponse:
+			w.WriteHeader(http.StatusBadRequest)
+			serveRecaptcha() // serve the initial page again, instead of nothing
+			return
+		case ErrInvalidCaptcha:
+			w.WriteHeader(http.StatusUnauthorized)
+			serveRecaptcha()
+			return
+		case nil:
+		default: // something else failed
+			util.GetLogger(req.Context()).WithError(err).Error("failed to validate recaptcha")
+			serveRecaptcha()
+			return
 		}
-	}
-	return &util.JSONResponse{
-		Code: http.StatusMethodNotAllowed,
-		JSON: jsonerror.NotFound("Bad method"),
-	}
-}
 
-// checkRecaptchaEnabled creates an error response if recaptcha is not usable on homeserver.
-func checkRecaptchaEnabled(
-	cfg *config.ClientAPI,
-	w http.ResponseWriter,
-	req *http.Request,
-) *util.JSONResponse {
-	if !cfg.RecaptchaEnabled {
-		return writeHTTPMessage(w, req,
-			"Recaptcha login is disabled on this Homeserver",
-			http.StatusBadRequest,
-		)
+		// Success. Add recaptcha as a completed login flow
+		sessions.addCompletedSessionStage(sessionID, authtypes.LoginTypeRecaptcha)
+
+		serveSuccess()
+		return
 	}
-	return nil
+	writeHTTPMessage(w, req, "Bad method", http.StatusMethodNotAllowed)
 }
 
 // writeHTTPMessage writes the given header and message to the HTTP response writer.
@@ -201,13 +189,10 @@ func checkRecaptchaEnabled(
 func writeHTTPMessage(
 	w http.ResponseWriter, req *http.Request,
 	message string, header int,
-) *util.JSONResponse {
+) {
 	w.WriteHeader(header)
 	_, err := w.Write([]byte(message))
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("w.Write failed")
-		res := jsonerror.InternalServerError()
-		return &res
 	}
-	return nil
 }