Create InvalidAPIEndpointHandler to be chi-Mount'd on BaseURL

This commit works to close issue #2190 by creating handler that returns
ErrInvalidAPIEndpoint when called. This will be used by chi Mount'ing
the handler to a specified route so that any calls to a route downstream
the Mount'd pattern will respond with the ErrInvalidAPIEndpoint error.

Also add corresponding test, TestInvalidRoute, to test
InvalidAPIEndpointHandler.

Create middleware to catch downstream routes from BaseURL

This commit works to close issue #2190 by creating middleware to ensure
users that call routes downstream of the BaseURL (i.e. /api/v1) are
return an invalid endpoint error and internal error status.

Remove BaseURLHandler

pkg/api/serve.go

@@ -33,6 +33,8 @@ const (
 	extensionValidationExcludeBody = "x-validation-exclude-body"
 )
 
+var ErrInvalidAPIEndpoint = errors.New("invalid API endpoint")
+
 type responseError struct {
 	Message string `json:"message"`
 }
@@ -85,6 +87,7 @@ func Serve(
 	r.Mount("/_pprof/", httputil.ServePPROF("/_pprof/"))
 	r.Mount("/swagger.json", http.HandlerFunc(swaggerSpecHandler))
 	r.Mount("/", uiHandler)
+	r.Mount(BaseURL, http.HandlerFunc(InvalidAPIEndpointHandler))
 	return r
 }
 
@@ -162,3 +165,10 @@ func validateRequest(r *http.Request, router routers.Router, options *openapi3fi
 	}
 	return http.StatusOK, nil
 }
+
+// InvalidAPIEndpointHandler returns ErrInvalidAPIEndpoint, and is currently being used to ensure
+// that routes under the pattern it is used with in chi.Router.Mount (i.e. /api/v1) are
+// not accessible.
+func InvalidAPIEndpointHandler(w http.ResponseWriter, _ *http.Request) {
+	writeError(w, http.StatusInternalServerError, ErrInvalidAPIEndpoint)
+}

pkg/api/serve_test.go

@@ -178,3 +178,34 @@ func setupClientWithAdmin(t testing.TB, blockstoreType string, opts ...testutil.
 	clt = setupClientByEndpoint(t, server.URL, cred.AccessKeyID, cred.SecretAccessKey)
 	return clt, deps
 }
+
+func TestInvalidRoute(t *testing.T) {
+	handler, _ := setupHandler(t, "")
+	server := setupServer(t, handler)
+	clt := setupClientByEndpoint(t, server.URL, "", "")
+	cred := createDefaultAdminUser(t, clt)
+
+	// setup client with invalid endpoint base url
+	basicAuthProvider, err := securityprovider.NewSecurityProviderBasicAuth(cred.AccessKeyID, cred.SecretAccessKey)
+	if err != nil {
+		t.Fatal("basic auth security provider", err)
+	}
+	clt, err = api.NewClientWithResponses(server.URL+api.BaseURL+"//", api.WithRequestEditorFn(basicAuthProvider.Intercept))
+	if err != nil {
+		t.Fatal("failed to create api client:", err)
+	}
+
+	ctx := context.Background()
+	resp, err := clt.ListRepositoriesWithResponse(ctx, &api.ListRepositoriesParams{})
+	if err != nil {
+		t.Fatalf("failed to get lakefs server version")
+	}
+	if resp.JSONDefault == nil {
+		t.Fatalf("client api call expected default error, got nil")
+	}
+	expectedErrMsg := api.ErrInvalidAPIEndpoint.Error()
+	errMsg := resp.JSONDefault.Message
+	if errMsg != expectedErrMsg {
+		t.Fatalf("client response error message: %s, expected: %s", errMsg, expectedErrMsg)
+	}
+}