Validate email before inserting/updating (#13475) (#13666)

* Add email validity check (#13475)

* Improve error feedback for duplicate deploy keys

Instead of a generic HTTP 500 error page, a flash message is rendered
with the deploy key page template so inform the user that a key with the
intended title already exists.

* API returns 422 error when key with name exists

* Add email validity checking

Add email validity checking for the following routes:
[Web interface]
1. User registration
2. User creation by admin
3. Adding an email through user settings
[API]
1. POST /admin/users
2. PATCH /admin/users/:username
3. POST /user/emails

* Add further tests

* Add signup email tests

* Add email validity check for linking existing account

* Address PR comments

* Remove unneeded DB session

* Move email check to updateUser

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

* skip email validation on empty string (#13627)

- move validation into its own function
- use a session for UpdateUserSetting

* rm TODO for backport

Co-authored-by: Chris Shyi <chrisshyi13@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

models/user_mail.go

@@ -8,6 +8,7 @@ package models
 import (
 	"errors"
 	"fmt"
+	"net/mail"
 	"strings"
 
 	"code.gitea.io/gitea/modules/log"
@@ -32,6 +33,19 @@ type EmailAddress struct {
 	IsPrimary   bool `xorm:"-"`
 }
 
+// ValidateEmail check if email is a allowed address
+func ValidateEmail(email string) error {
+	if len(email) == 0 {
+		return nil
+	}
+
+	if _, err := mail.ParseAddress(email); err != nil {
+		return ErrEmailInvalid{email}
+	}
+
+	return nil
+}
+
 // GetEmailAddresses returns all email addresses belongs to given user.
 func GetEmailAddresses(uid int64) ([]*EmailAddress, error) {
 	emails := make([]*EmailAddress, 0, 5)
@@ -143,6 +157,10 @@ func addEmailAddress(e Engine, email *EmailAddress) error {
 		return ErrEmailAlreadyUsed{email.Email}
 	}
 
+	if err = ValidateEmail(email.Email); err != nil {
+		return err
+	}
+
 	_, err = e.Insert(email)
 	return err
 }
@@ -167,6 +185,9 @@ func AddEmailAddresses(emails []*EmailAddress) error {
 		} else if used {
 			return ErrEmailAlreadyUsed{emails[i].Email}
 		}
+		if err = ValidateEmail(emails[i].Email); err != nil {
+			return err
+		}
 	}
 
 	if _, err := x.Insert(emails); err != nil {