編輯“十天學(xué)會(huì)PHP/第八天：Sessions、發(fā)送電子郵件”（章節(jié)）

==PHPE-mail注入==
*首先，請(qǐng)看上一節(jié)中的[[PHP]]代碼：
<pre>
<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>
</pre>
*以上代碼存在的問題是，未經(jīng)授權(quán)的用戶可通過輸入表單在郵件頭部插入數(shù)據(jù)。
*假如用戶在表單中的輸入框內(nèi)加入這些文本，會(huì)出現(xiàn)什么情況呢？
<pre>
someone@example.com%0ACc:person2@example.com
%0ABcc:person3@example.com,person3@example.com,
anotherperson4@example.com,person5@example.com
%0ABTo:person6@example.com
</pre>
*與往常一樣，mail() 函數(shù)把上面的文本放入郵件頭部，那么現(xiàn)在頭部有了額外的 Cc:, Bcc: 以及 To: 字段。當(dāng)用戶點(diǎn)擊提交按鈕時(shí)，這封 e-mail 會(huì)被發(fā)送到上面所有的地址！
===PHP 防止E-mail注入===
*防止e-mail注入的最好方法是對(duì)輸入進(jìn)行驗(yàn)證。
*下面的[[代碼]]與上一節(jié)類似，不過我們已經(jīng)增加了檢測(cè)表單中email字段的輸入驗(yàn)證程序：
<pre>
<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>
</pre>
*在上面的代碼中，我們使用了PHP過濾器來對(duì)輸入進(jìn)行驗(yàn)證：
*FILTER_SANITIZE_EMAIL 從字符串中刪除電子郵件的非法字符 
*FILTER_VALIDATE_EMAIL 驗(yàn)證電子郵件地址 
*您可以在我們的 PHP 過濾器這一節(jié)中閱讀更多有關(guān)過濾器的內(nèi)容。