はじめに

taint は、XSS コード (汚染された文字列) を検出するための拡張モジュールです。 SQL インジェクションやシェルコマンドインジェクションなどの脆弱性を検出するためにも使えます。

taint を有効にすると、汚染された文字列 ($_GET や $_POST、$_COOKIE に由来するもの) を何かの関数に渡そうとしたときに警告を出すようになります。

例1 taint() の例

<?php
$a = trim($_GET['a']);

$file_name = '/tmp' .  $a;
$output    = "Welcome, {$a} !!!";
$var       = "output";
$sql       = "Select *  from " . $a;
$sql      .= "ooxx";

echo $output;

print $$var;

include $file_name;

mysql_query($sql);
?>

上の例の出力は、たとえば以下のようになります。

Warning: main() [function.echo]: Attempt to echo a string that might be tainted

Warning: main() [function.echo]: Attempt to print a string that might be tainted

Warning: include() [function.include]: File path contains data that might be tainted

Warning: mysql_query() [function.mysql-query]: SQL statement contains data that might be tainted

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User Contributed Notes 1 note

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wolfen at gmail dot com ¶

9 years ago


I'm wondering about the quality of this PHP extension, specifically:

1. Are there any known bugs or limitations?
2. How does enabling it affect the performance of a typical system?
3. Would I be foolish to use it in PROD? Yes, yes, I know *not* using Taint in PROD is risky, that is why I want to use it! But I need to know the risks associated with using it in order to be able to make a rational decision.

Also, is this the same as the PECL package developed by Weitse Venema following PHP RFC for Taint (https://wiki.php.net/rfc/taint) or does it differ significantly in any way?

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