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cd deploy
docker-compose -p web_chadgpt up --build -dSetup http reverse proxy to port 5000.
Provide zip file: public/web-chadgpt.zip.
Exploit the SQL-injection protected by WAF by providing JSON that will be parsed by GoJay library and
standard encoding/json library differently.
We can find an SQL-injection inside the target application: the payload 'q' parameter is not properly escaped. But there is a WAF that escapes all strings inside the JSON body.
Hovewer, the are two facts that can lead to the solution:
- Quotes are not properly escaped.
- WAF will proxy the request if it failed to decode the JSON body.
This allow two solutions:
We can provide the \', as ' will be replaced with '' we will get the \'' as a result. Which will allow us to use the SQL-injection.
Use this as an input: \' union select flag from flags --
We can notice that the target application uses gojay library to parse the JSON body, but the WAF uses standard encoding/json library.
Having this in mind, we can find a JSON that will be parsed by the gojay library, but won't be parsed by the standard library.
One of the key differences is that GoJay library allows anything (including comment) after it parses all JSON fields needed. So we can provide a JSON like this as a body:
{
"maxTokens": 123,
"q": "asd'OR 1=2 UNION SELECT flag FROM flags -- ",
asd
}chadgpt-647150b7b2303d42.task.brics-ctf.ru
brics+{p14y1Ng_bM7H_C4N_y0u_F33l_mY_H34r7}
Yes