full-disclosure - Re: Google's robots.txt handling

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Message-ID: <96E56E3A0BC122419B183976D487643B199FF239@NA-2008-114.allergruppen.no>
Date: Mon, 10 Dec 2012 21:01:37 +0000
From: "Gildseth, Tommy" <tommy.gildseth@...er.no>
To: "full-disclosure@...ts.grok.org.uk" <full-disclosure@...ts.grok.org.uk>
Subject: Re: Google's robots.txt handling

On 2012-12-10 12:25, Hurgel Bumpf wrote:
> Hi list,
>
>
> i tried to contact google, but as they didn't answer my email,  i do
> forward this to FD.
> This "security" feature is not cleary a google vulnerability, but
> exposes websites informations that are not really intended to be
> public.
>
> (Additionally i have to say that i advocate robots.txt files without
> sensitive content and working security mechanisms.)
>
> Here is an example:
>
> An admin has a public webservice running with folders containing
> sensitive informations. Enter these folders in his robots.txt and
> "protect" them from the indexing process of spiders. As he doesn't
> want the /admin/ gui to appear in the search results he also puts his
> /admin in the robots text and finaly makes a backup to the folder
> /backup.
>
> Nevertheless these folders arent browsable but they might contain
> f(a)iles with easy to guess namestructures, non-encrypted
> authentications (simple AUTH) , you name it...
>
> Without a robots.txt nobody would know about the existance of these
> folders, but as some folders might be linked somewhere, these folders
> might appear in search results when not defined in the robots.txt
> The
> admin finds himself in a catch-22 situation where he seems to prefer
> the robots.txt file.
>
> Long story short.
>
> Although google accepts and respects the directives of the robots.txt
> file, google INDEXES these files.
>
> This my concern.
>
>
> http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+Disallow%3A+%2Fadmin
>
> http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+Disallow%3A+%2Fbackup
>
> http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+Disallow%3A+%2Fpassword
>
> As these searches can be used less for targeted attacks, they more
> can be used to find victims.
>
>
> http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+%2FDisallow%3A+wp-admin
>
> http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+%2FDisallow%3A+typo3
> <Just be creative>
>
> This shouldn't be a discussion about bad practice but the google
> feature itself.
>
> Indexing a file which is used to prevent indexing.. isn't that just
> paradox and hypocrite?

If we ignore the obvious security by obscurity aspect of this discussion, there are alternatives to putting "secret" paths in the robots.txt file. One is f.ex to tell your webserver to serve these "secret" paths with a X-robots-tag HTTP header, thus not exposing anything before it's actually been requested.

-- 
TommyG

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