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Re: Guile security vulnerability w/ listening on localhost + port (with
Christopher Allan Webber
Re: Guile security vulnerability w/ listening on localhost + port (with fix)
Sun, 16 Oct 2016 10:05:07 -0500
mu4e 0.9.16; emacs 25.1.1
Lizzie Dixon writes:
> On 10/11, Christopher Allan Webber wrote:
>> The default in Guile has been to expose a port over localhost to which
>> code may be passed. The assumption for this is that only a local user
>> may write to localhost, so it should be safe. Unfortunately, users
>> simultaneously developing Guile and operating modern browsers are
>> vulnerable to a combination of an html form protocol attack  and a
>> DNS rebinding attack . How to combine these attacks is published in
>> the article "How to steal any developer's local database" .
>> In Guile's case, the general idea is that you visit some site which
>> pressing a button which performs a POST), and the site operator switches
>> the DNS from their own IP to 127.0.0.1. Then a POST is done from the
>> website to 127.0.0.1 with the body containing scheme code. This code is
>> then executed by the Guile interpreter on the listening port.
> You don't need to rebind DNS to exploit this bug, or other bugs like
> it. I wrote some details here:
Hi Lizzie! Thanks for the post. Interesting to see you figured out how
to do it with a GET request, not just a POST. So, I guess this will
work from a public site as well? I'm always a bit fuzzy about what
browsers do and don't allow, but I'm stunned that a browser will let a
request from some http://foo.example/ to http://localhost:37146/, even
for just a GET. It seems like there are all sorts of daemons you can
exploit that way.
Anyway, thanks for the interesting blogpost, and kudos for using Guile
to write your example!