如何检查正则表达式在PHP中是否有害

Question

I am working on a project. This project have a user interface that we wrote in PHP. In the management part, there is a form input where the user needs to enter a regular expression. As I know, I can not check if is a regex or not, because every string is a regex. What I want to do is check whether this input is proper or not? Which way I can do it?

Answer 1

It's very hard to do this by analysing the regex (short of actually parsing the regex itself.

I suggest you rather use conservative settings for pcre.backtrack-limit and pcre.recursion_limit.