Date: Tue, 01 Apr 2014 21:16:09 +0200
From: Sven 'Darkman' Michels <sven@...kman.de>
To: fulldisclosure@...lists.org
Subject: Re: [FD] Access anyone's Facebook "profile picture" in full
 resolution regardless of the ACL restriction

Hi,

just a side note: a "non" public profile can be found on some public files.
For example, someone who has restricted its profile for friends only comments
on a fan page of a public product or something like that. In that case you
can't go to the profile itself, thus you won't see a "large" profile pic,
but you get the right url to use Bipins "trick" (remove the resize part).

This is, of course, still no big deal. The "problem" is the way the cdn works.
It stores fullsize pictures and allows your to hand out resized versions by
giving the right arguments to it. This, btw, seems also to work the other
way around: instead of removing the p160... stuff, you can also use bigger
numbers to "enlarge" the pic, at least it seems to work some times. So maybe
you can abuse this... like most of the other services like this.

Regards,
Darkman

Am 01.04.2014 16:49, schrieb Philip Whitehouse:
> Again they need the URL.
>
> If you have a way to determine the URL of a specific user's profile image from public info that would be a vulnerability.
>
> Simply the ability for a user or allowed visitor to copy the URL is not.
>
> You can determine who can see the URL in your Facebook privacy settings.
>
> Philip Whitehouse
>
> ----- Reply message -----
> From: "Bipin Gautam" <bipin.gautam@...il.com>
> To: "Philip Whitehouse" <philip@...uk.com>
> Cc: "fulldisclosure" <fulldisclosure@...lists.org>
> Subject: Access anyone's Facebook "profile picture" in full resolution regardless of the ACL restriction
> Date: Tue, Apr 1, 2014 15:19
>
> Hi,
>
> the POC is about "anyone being able to access anyone's facebook
> profile picture in full resolution" + regardless of the ACL set to
> their facebook profile picture (say; even when your profile picture
> permission of your facebook is set as... viewable to "only me" or
> "friends" ) ...anyone can see your full resolution profile picture
> even without logging on to facebook with the following method!
>
> (Assumption: maybe if you (your ISP?) are using CDN and someone in
> your ISP / region have already viewed the profile picture and as it is
> already fetched locally / cached in local CDN so, other party can
> access it? Does CND have IP restriction for a region / ISP ? )
>
> Try... it works for me, Make sense ?
>
>
> On 4/1/14, Philip Whitehouse <philip@...uk.com> wrote:
>> This is not a vulnerability.
>>
>> The image path is not predictable. Sharing the URL is by itself giving
>> permission for the other party to see it.
>>
>> Even if it were possible to restrict access it could be circumvented by
>> downloading it and emailing the file instead of the URL
>>
>>
>> Philip Whitehouse
>>
>> ----- Reply message -----
>> From: "Bipin Gautam" <bipin.gautam@...il.com>
>> To: "fulldisclosure" <fulldisclosure@...lists.org>
>> Subject: Access anyone's Facebook "profile picture" in full resolution
>> regardless of the ACL restriction
>> Date: Tue, Apr 1, 2014 10:59
>>
>> Hi List,
>>
>> I felt like writing / pointing this minor issue, as it as its "Facebook" ...
>>
>> This issue is due to the way facebook pictures are stored in CDN
>> without authentication mechanism, during accessing it. (which would be
>> way technically complicated to implement it)
>>
>> Also, it is a Facebook feature that... if you have full path of an
>> image, you can pass it to anyone over the internet which they can
>> access it directly (and the facebook user should not have unrealistic
>> expectation to privacy. Hence, if someone can access an image they can
>> save/email it to others, anyway.)
>>
>>
>> POC:
>>
>> ( Please TEST it in a real profile, real world example and it should
>> work. I obviously changed the URL, POC below, to gibberish
>> "6549_16544614736_444444875_n.jpg" )
>>
>> STEPS:
>>
>> You could try this by :
>>
>> - changing your own facebook profile picture viewable to "only me",
>> then bookmark your own Facebook profile and logout and clear cache.
>>
>> - or then try different browser with your own profile from bookmark,
>> without logging in to facebook!
>>
>> - or pass your FB profile to a friend, with the following instruction.
>>
>> ___
>>
>> - then, in your browser, "Right click the Facebook profile image" that
>> you want to access in full resolution (that have ACL as access to
>> "only me" or "friends" ) > click "Copy image location" > paste it in
>> notepad
>>
>> sample url you will get (this link below is broken)
>>
>> :[1]
>> https://fbcdn-profile-a.akamaihd.net/hprofile-ak-frc3/t1.0-1/c0.18.160.160/p160x160/6549_16544614736_444444875_n.jpg
>>
>>
>> to remove from [1]: "/c0.18.160.160/p160x160"   (part; in other cases,
>> the url structure may be different, you just have to find and remove
>> this middle part...)
>>
>> final modified url from above, which you can access the profile
>> picture in full resolution via your browser :
>>
>> https://fbcdn-profile-a.akamaihd.net/hprofile-ak-frc3/t1.0-1/6549_16544614736_444444875_n.jpg
>>
>>
>> Respectfully,
>> -bipin
>
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