How to rewrite dynamic value in response bod using Charles Proxy

Question

I am new to Charles Proxy and Regular expression. I have been trying to rewrite feed an invalid session id to the mobile app to check the error handling.

We have the response body like this:

{
    “session_id": "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3”
    "expiry_time": 42000,
    "refresh_token": "MiOiJodHRwOi8vdGVzdC5sdGEuYWNjb3Vr”
}

I am trying to rewrite the session_id and pass an invalid id using Charles rewrite

Charles Screen

I have tried here in stackoverflow and couldn't find an answer. I am sure I am doing something wrong as a newbie. Any insight would be really appreciated

Answer 1

The regular expression "session_id":\[(.*)\] would not match the string "session_id": "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3". Basically that regular expression is looking for something like this "session_id":[any text]".

Try using this regex "session_id": "(.*?)". It should match the format you're expecting in the response.

I hope this helps. Let me know if you need further information.