Add Allow-/Block-List for Migrate & Mirrors (#13610)

* add black list and white list support for migrating repositories

* fix fmt

* fix lint

* fix vendor

* fix modules.txt

* clean diff

* specify log message

* use blocklist/allowlist

* allways use lowercase to match url

* Apply allow/block

* Settings: use existing "migrations" section

* convert domains lower case

* dont store unused value

* Block private addresses for migration by default

* fix lint

* use proposed-upstream func to detect private IP addr

* a nit

* add own error for blocked migration, add tests, imprufe api

* fix test

* fix-if-localhost-is-ipv4

* rename error & error message

* rename setting options

* Apply suggestions from code review

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

modules/migrations/migrate_test.go

@@ -0,0 +1,34 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMigrateWhiteBlocklist(t *testing.T) {
+	setting.Migrations.AllowedDomains = []string{"github.com"}
+	assert.NoError(t, Init())
+
+	err := isMigrateURLAllowed("https://gitlab.com/gitlab/gitlab.git")
+	assert.Error(t, err)
+
+	err = isMigrateURLAllowed("https://github.com/go-gitea/gitea.git")
+	assert.NoError(t, err)
+
+	setting.Migrations.AllowedDomains = []string{}
+	setting.Migrations.BlockedDomains = []string{"github.com"}
+	assert.NoError(t, Init())
+
+	err = isMigrateURLAllowed("https://gitlab.com/gitlab/gitlab.git")
+	assert.NoError(t, err)
+
+	err = isMigrateURLAllowed("https://github.com/go-gitea/gitea.git")
+	assert.Error(t, err)
+}