慢正则表达式解释 [英] Slow Regular Expression Explanation

问题描述

有人可以提供下面正则表达式的详细解释吗？



我正在检查.NET Framework 4.5中引入的一些功能和一个提到的好处是 Regex Timeout 。



在示例中使用以下正则表达式：

 ^（\d +）+ $ 

在以下文字：

 123453109839109283090492309480329489812093809x 

并且需要很长时间才能得出结果。



根据我的理解，要求正则表达式从开始到结束匹配一个或多个数字的存在 - 一次或多次。这是最后一个+标志让我感到困惑。



问题：



1.最后 + 标志的目的是什么？

2.为什么正则表达式会立即返回 $ 标志丢失了吗？

3.您能否提供逐步表达Regex如何开始执行的事情？



谢谢：）

解决方案

关于以下文字：

 123453109839109283090492309480329489812093809x 

并且需要很长时间才能得出结果。



根据我的理解，要求Regex匹配来自从一端开始到一个或多个数字的存在 - 一次或多次。这是最后一个+标志让我感到困惑。



问题：



1.最后 + 标志的目的是什么？

2.为什么正则表达式会立即返回

标志丢失了吗？

3.你能提供一步一步的东西吗？表达正则表达式将如何开始执行？



谢谢：）

你只有一个'邪恶'表达式.. 。



https://www.owasp.org /index.php/Regular_expression_Denial_of_Service_-_ReDoS [ ^ ]



它将正则表达式引擎（不仅仅是.NET，还有其他人）发送到一个看起来无法找到的无限循环中。

Can someone please provide a thorough explanation of what's going on with the Regex below?

I was checking some of the features introduced in .NET Framework 4.5 and one of the mentioned benefits was Regex Timeout.

In the example the following Regex is used:

^(\d+)+$

on the following text:

123453109839109283090492309480329489812093809x

and it takes ages to come up with a result.

From what I understand the Regex is asked to match from the start to the end the existence of one or more digits - one or more times. And it is this last + sign that is confusing me.

Questions:

1. What is the purpose of the last + sign?
2. Why does the Regex return instantly if the $ sign is missing?
3. Can you provide a 'step-by-step' sort of thing expressing how the Regex will begin execution?

Thanks :)

解决方案

on the following text:

123453109839109283090492309480329489812093809x

and it takes ages to come up with a result.

From what I understand the Regex is asked to match from the start to the end the existence of one or more digits - one or more times. And it is this last + sign that is confusing me.

Questions:

1. What is the purpose of the last + sign?
2. Why does the Regex return instantly if the

sign is missing?
3. Can you provide a 'step-by-step' sort of thing expressing how the Regex will begin execution?

Thanks :)

You just have one of those 'evil' expressions...

https://www.owasp.org/index.php/Regular_expression_Denial_of_Service_-_ReDoS[^]

It sends the regex engine (not just the .NET but others too) into an infinite loop of looking something that can't be found...

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