refactor: prepare to decouple the "model migration" package and "models" package (#38533)

Migrations should never use model structs directly, because the model
structs can be different in different releases. e.g. if one migration uses
"User" model, it works in the early releases, then one day, when the
User model changes, the migration breaks because it will use the
new (incorrect) User model, it should only use the old User model.

The same to "modules/structs".

---------

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: delvh <dev.lh@web.de>

modelmigration/v1_6/v71.go

@@ -0,0 +1,74 @@
+// Copyright 2018 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_6
+
+import (
+	"fmt"
+
+	"gitea.dev/modelmigration/base"
+	"gitea.dev/modules/timeutil"
+	"gitea.dev/modules/util"
+)
+
+func AddScratchHash(x base.EngineMigration) error {
+	// TwoFactor see models/twofactor.go
+	type TwoFactor struct {
+		ID               int64 `xorm:"pk autoincr"`
+		UID              int64 `xorm:"UNIQUE"`
+		Secret           string
+		ScratchToken     string
+		ScratchSalt      string
+		ScratchHash      string
+		LastUsedPasscode string             `xorm:"VARCHAR(10)"`
+		CreatedUnix      timeutil.TimeStamp `xorm:"INDEX created"`
+		UpdatedUnix      timeutil.TimeStamp `xorm:"INDEX updated"`
+	}
+
+	if err := x.Sync(new(TwoFactor)); err != nil {
+		return fmt.Errorf("Sync: %w", err)
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	// transform all tokens to hashes
+	const batchSize = 100
+	for start := 0; ; start += batchSize {
+		tfas := make([]*TwoFactor, 0, batchSize)
+		if err := sess.Limit(batchSize, start).Find(&tfas); err != nil {
+			return err
+		}
+		if len(tfas) == 0 {
+			break
+		}
+
+		for _, tfa := range tfas {
+			// generate salt
+			salt := util.CryptoRandomString(10)
+			tfa.ScratchSalt = salt
+			tfa.ScratchHash = base.HashToken(tfa.ScratchToken, salt)
+
+			if _, err := sess.ID(tfa.ID).Cols("scratch_salt, scratch_hash").Update(tfa); err != nil {
+				return fmt.Errorf("couldn't add in scratch_hash and scratch_salt: %w", err)
+			}
+		}
+	}
+
+	// Commit and begin new transaction for dropping columns
+	if err := sess.Commit(); err != nil {
+		return err
+	}
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	if err := base.DropTableColumns(sess, "two_factor", "scratch_token"); err != nil {
+		return err
+	}
+	return sess.Commit()
+}