PHP Secure E-mails
There is a weakness in the PHP e-mail script in the previous chapter.
PHP E-mail Injections
First, look at the PHP code from the previous chapter:
| <html> <body> <?php if (isset($_REQUEST['email'])) //if "email" is filled out, send email { //send email $email = $_REQUEST['email'] ; $subject = $_REQUEST['subject'] ; $message = $_REQUEST['message'] ; mail("someone@example.com", "Subject: $subject", $message, "From: $email" ); echo "Thank you for using our mail form"; } else //if "email" is not filled out, display the form { echo "<form method='post' action='mailform.php'> Email: <input name='email' type='text' /><br /> Subject: <input name='subject' type='text' /><br /> Message:<br /> <textarea name='message' rows='15' cols='40'> </textarea><br /> <input type='submit' /> </form>"; } ?> </body> </html> |
The problem with the code above is that unauthorized users can insert data into the mail headers via the input form.
What happens if the user adds the following text to the email input field in the form?
| someone@example.com%0ACc:person2@example.com %0ABcc:person3@example.com,person3@example.com, anotherperson4@example.com,person5@example.com %0ABTo:person6@example.com |
The mail() function puts the text above into the mail headers as usual, and now the header has an extra Cc:, Bcc:, and To: field. When the user clicks the submit button, the e-mail will be sent to all of the addresses above!
PHP Stopping E-mail Injections
The best way to stop e-mail injections is to validate the input.
The code below is the same as in the previous chapter, but now we have added an input validator that checks the email field in the form:
| <html> <body> <?php function spamcheck($field) { //filter_var() sanitizes the e-mail //address using FILTER_SANITIZE_EMAIL $field=filter_var($field, FILTER_SANITIZE_EMAIL); //filter_var() validates the e-mail //address using FILTER_VALIDATE_EMAIL if(filter_var($field, FILTER_VALIDATE_EMAIL)) { return TRUE; } else { return FALSE; } } if (isset($_REQUEST['email'])) {//if "email" is filled out, proceed //check if the email address is invalid $mailcheck = spamcheck($_REQUEST['email']); if ($mailcheck==FALSE) { echo "Invalid input"; } else {//send email $email = $_REQUEST['email'] ; $subject = $_REQUEST['subject'] ; $message = $_REQUEST['message'] ; mail("someone@example.com", "Subject: $subject", $message, "From: $email" ); echo "Thank you for using our mail form"; } } else {//if "email" is not filled out, display the form echo "<form method='post' action='mailform.php'> Email: <input name='email' type='text' /><br /> Subject: <input name='subject' type='text' /><br /> Message:<br /> <textarea name='message' rows='15' cols='40'> </textarea><br /> <input type='submit' /> </form>"; } ?> </body> </html> |
In the code above we use PHP filters to validate input:
- The FILTER_SANITIZE_EMAIL filter removes all illegal e-mail characters from a string
- The FILTER_VALIDATE_EMAIL filter validates value as an e-mail address
You can read more about filters in our PHP Filter chapter.
[출처] http://www.w3schools.com
'프로그램&DB > PHP' 카테고리의 다른 글
| PHP Exception Handling 예외 처리 (0) | 2011.08.27 |
|---|---|
| PHP Error Handling 에러코드 및 대처 예문 (0) | 2011.08.27 |
| PHP Sending E-mails 이메일 발송(보내기) (0) | 2011.08.27 |
| PHP Sessions 세션 관련 함수 (0) | 2011.08.27 |
| PHP Cookies 쿠키 관련 함수 (0) | 2011.08.27 |