Op 04-10-2023 om 07:29 schreef Vivien Kraus:
Le mercredi 04 octobre 2023 à 00:30 +0200, Maxime Devos a écrit :The best prevention is not allowing redirects at all or only allowing redirections that keep the hostname intact -- while an option for much software, it isn't an option for web browsers.Partially scratch that -- restricting to ‘keeping hostname intact’ is insufficient, because there could be a DNS record that points 'website via http' to 127.0.0.1, and hence a redirect from https://website --> http://website can change IP addresses from global Internet to local computer.But then, it is not a problem with resolve-relative-reference, and not even a risk with redirections; if the DNS changes before you query the page, then the secret page leaks anyway, no redirection needed. > We could add a warning in the "http-request" method documentation, like: Be warned that if you are hosting a private HTTP(s) server on your system, a DNS change for a public target URI to your internal IP address, or following a redirection from a public target URI to your private server, may lead you to consider the response originating from your private server as public. Would that be a good summary?
Hum I was thinking from the perspective of the client, whereas this considers things form the perspective of the server, but that works too I suppose.
However, I am confused by the phrasing of the last sentence > [...], may lead you to consider the response originating from > your private server as public.After reading it again, I think I understand it, but I would instead propose:
> may allow you to accidentally contact your private server as if it were public. Depending on the application, an attacker could exploit this.
because:
* while the responses can be a problem, another problem is that
a request is sent in the first place -- as a problematic example,
the private server could have a buffer overflow somewhere that
is remotely triggered by the attacker via a redirection to a long
URL triggering the buffer overflow (with an attacking payload!).
For another example, consider PUT/POST/DELETE/... instead of GET.
* to make it clear this is a potential security problem.
‘Be warned’ doesn't cut it IMO.
* another reason I can't word properly, something about the
'as public'.
Best regards,
Maxime Devos.
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