Two factor authentication support (#630)

* Initial commit for 2FA support

Signed-off-by: Andrew <write@imaginarycode.com>

* Add vendored files

* Add missing depends

* A few clean ups

* Added improvements, proper encryption

* Better encryption key

* Simplify "key" generation

* Make 2FA enrollment page more robust

* Fix typo

* Rename twofa/2FA to TwoFactor

* UNIQUE INDEX -> UNIQUE

3 files changed, 161 insertions, 0 deletions

diff --git a/models/error.go b/models/error.go
index edbb6003e9..e0d33df6dc 100644
--- a/models/error.go
+++ b/models/error.go
@@ -787,6 +787,25 @@ func (err ErrTeamAlreadyExist) Error() string {
 	return fmt.Sprintf("team already exists [org_id: %d, name: %s]", err.OrgID, err.Name)
 }
 
+//
+// Two-factor authentication
+//
+
+// ErrTwoFactorNotEnrolled indicates that a user is not enrolled in two-factor authentication.
+type ErrTwoFactorNotEnrolled struct {
+	UID int64
+}
+
+// IsErrTwoFactorNotEnrolled checks if an error is a ErrTwoFactorNotEnrolled.
+func IsErrTwoFactorNotEnrolled(err error) bool {
+	_, ok := err.(ErrTwoFactorNotEnrolled)
+	return ok
+}
+
+func (err ErrTwoFactorNotEnrolled) Error() string {
+	return fmt.Sprintf("user not enrolled in 2FA [uid: %d]", err.UID)
+}
+
 //  ____ ___        .__                    .___
 // |    |   \______ |  |   _________     __| _/
 // |    |   /\____ \|  |  /  _ \__  \   / __ |
diff --git a/models/models.go b/models/models.go
index 131fd4fdb2..d9716e79bd 100644
--- a/models/models.go
+++ b/models/models.go
@@ -105,6 +105,7 @@ func init() {
 		new(Notification),
 		new(IssueUser),
 		new(LFSMetaObject),
+		new(TwoFactor),
 	)
 
 	gonicNames := []string{"SSL", "UID"}
diff --git a/models/twofactor.go b/models/twofactor.go
new file mode 100644
index 0000000000..4c0d3702db
--- /dev/null
+++ b/models/twofactor.go
@@ -0,0 +1,141 @@
+// Copyright 2017 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 models
+
+import (
+	"crypto/md5"
+	"crypto/subtle"
+	"encoding/base64"
+	"time"
+
+	"github.com/Unknwon/com"
+	"github.com/go-xorm/xorm"
+	"github.com/pquerna/otp/totp"
+
+	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+// TwoFactor represents a two-factor authentication token.
+type TwoFactor struct {
+	ID           int64 `xorm:"pk autoincr"`
+	UID          int64 `xorm:"UNIQUE"`
+	Secret       string
+	ScratchToken string
+
+	Created     time.Time `xorm:"-"`
+	CreatedUnix int64     `xorm:"INDEX"`
+	Updated     time.Time `xorm:"-"` // Note: Updated must below Created for AfterSet.
+	UpdatedUnix int64     `xorm:"INDEX"`
+}
+
+// BeforeInsert will be invoked by XORM before inserting a record representing this object.
+func (t *TwoFactor) BeforeInsert() {
+	t.CreatedUnix = time.Now().Unix()
+}
+
+// BeforeUpdate is invoked from XORM before updating this object.
+func (t *TwoFactor) BeforeUpdate() {
+	t.UpdatedUnix = time.Now().Unix()
+}
+
+// AfterSet is invoked from XORM after setting the value of a field of this object.
+func (t *TwoFactor) AfterSet(colName string, _ xorm.Cell) {
+	switch colName {
+	case "created_unix":
+		t.Created = time.Unix(t.CreatedUnix, 0).Local()
+	case "updated_unix":
+		t.Updated = time.Unix(t.UpdatedUnix, 0).Local()
+	}
+}
+
+// GenerateScratchToken recreates the scratch token the user is using.
+func (t *TwoFactor) GenerateScratchToken() error {
+	token, err := base.GetRandomString(8)
+	if err != nil {
+		return err
+	}
+	t.ScratchToken = token
+	return nil
+}
+
+// VerifyScratchToken verifies if the specified scratch token is valid.
+func (t *TwoFactor) VerifyScratchToken(token string) bool {
+	if len(token) == 0 {
+		return false
+	}
+	return subtle.ConstantTimeCompare([]byte(token), []byte(t.ScratchToken)) == 1
+}
+
+func (t *TwoFactor) getEncryptionKey() []byte {
+	k := md5.Sum([]byte(setting.SecretKey))
+	return k[:]
+}
+
+// SetSecret sets the 2FA secret.
+func (t *TwoFactor) SetSecret(secret string) error {
+	secretBytes, err := com.AESEncrypt(t.getEncryptionKey(), []byte(secret))
+	if err != nil {
+		return err
+	}
+	t.Secret = base64.StdEncoding.EncodeToString(secretBytes)
+	return nil
+}
+
+// ValidateTOTP validates the provided passcode.
+func (t *TwoFactor) ValidateTOTP(passcode string) (bool, error) {
+	decodedStoredSecret, err := base64.StdEncoding.DecodeString(t.Secret)
+	if err != nil {
+		return false, err
+	}
+	secret, err := com.AESDecrypt(t.getEncryptionKey(), decodedStoredSecret)
+	if err != nil {
+		return false, err
+	}
+	secretStr := string(secret)
+	return totp.Validate(passcode, secretStr), nil
+}
+
+// NewTwoFactor creates a new two-factor authentication token.
+func NewTwoFactor(t *TwoFactor) error {
+	err := t.GenerateScratchToken()
+	if err != nil {
+		return err
+	}
+	_, err = x.Insert(t)
+	return err
+}
+
+// UpdateTwoFactor updates a two-factor authentication token.
+func UpdateTwoFactor(t *TwoFactor) error {
+	_, err := x.Id(t.ID).AllCols().Update(t)
+	return err
+}
+
+// GetTwoFactorByUID returns the two-factor authentication token associated with
+// the user, if any.
+func GetTwoFactorByUID(uid int64) (*TwoFactor, error) {
+	twofa := &TwoFactor{UID: uid}
+	has, err := x.Get(twofa)
+	if err != nil {
+		return nil, err
+	} else if !has {
+		return nil, ErrTwoFactorNotEnrolled{uid}
+	}
+	return twofa, nil
+}
+
+// DeleteTwoFactorByID deletes two-factor authentication token by given ID.
+func DeleteTwoFactorByID(id, userID int64) error {
+	cnt, err := x.Id(id).Delete(&TwoFactor{
+		UID: userID,
+	})
+	if err != nil {
+		return err
+	} else if cnt != 1 {
+		return ErrTwoFactorNotEnrolled{userID}
+	}
+	return nil
+}