用PHP清理用户提供的正则表达式 [英] Sanitization of User-Supplied Regular Expressions in PHP

问题描述

我想创建一个用户可以在其中测试正则表达式的网站(已经有很多这样的网站了……例如:

I want to create a website where users can test regular expressions (there are many out there already...such as this one: http://www.pagecolumn.com/tool/pregtest.htm). Basically, the user provides a regular expression and some sample text, and the results of the regex evaluation will be spit back.

我想使用PHP"preg_ *"函数在服务器端评估正则表达式.有没有办法清理提供的正则表达式?我应该关注哪些安全漏洞?

I want to evaluate the regex on the server side with the PHP "preg_*" functions. Is there a way to sanitize the supplied regex? What are the security vulnerabilities that I should be concerned about?

推荐答案

我认为PHP本身会检查正则表达式. 这是我制作的示例脚本:

I think PHP itself will check the regex. Here's a sample script I made :

// check for input, and set max size of input
if(@!empty($_POST['regex'])
    && @!empty($_POST['text'])
    && strlen($_POST['regex'])<1000
    && strlen($_POST['text'])<2000
    ){
    // set script timeout in case something goes wrong (SAFE MODE must be OFF)
    $old_time=ini_get('max_execution_time');
    if(!set_time_limit(1)) die('SAFE MODE MUST BE OFF'); // 1 sec is more then enough

    // trim input, it's up to you to do more checks
    $regex=trim($_POST['regex']);
    // don't trim the text, it can be needed
    $input=$_POST['text'];
    // escape slashes
    $regex=preg_replace('/([\\/]+)?//', '\/', $regex);

    // go for the regex
    if(false===$matched=@preg_match('/'.$regex.'/', $input, $matches)){
            // regex was tested, show results
            echo 'Matches: '.$matched.'<br />';
            if($matched>0){
                    echo 'matches: <br />';
                    foreach($matches as $i =>  $match){
                            echo $i.' = '.$match.'<br />';
                }
            }
    }
    // set back original execution time
    set_time_limit($old_time);
}

无论如何，永远不要将eval()与用户提交的字符串一起使用.

此外，您可以进行一些简单的简约消毒，但这取决于您. ;)

Additionally, you can do some simple minimalistic sanitizing, but that's up to you. ;)

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