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Message-ID: <51644E07.7090500@redhat.com>
Date: Tue, 09 Apr 2013 11:21:11 -0600
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: Michael Scherer <misc@...b.org>, security@...are.com, security@...bra.com
Subject: Re: Zimbra XSS in aspell.php, CVE request
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On 04/05/2013 06:14 PM, Michael Scherer wrote:
> Le vendredi 05 avril 2013 à 18:05 -0600, Kurt Seifried a écrit :
>> On 04/05/2013 04:21 AM, Michael Scherer wrote:
>>> Hi,
>>>
>>> While trying to see how hard a bug would be to fix in Zimbra
>>> during a discussion with a coworker, I stumbled across a XSS
>>> flaw in Zimbra, in a spell checking external webservice.
>>>
>>> Since I didn't found the public web interface for the source
>>> code of Zimbra and since perforce is not as straightforward to
>>> run on linux than git and slow to download the 2G of source
>>> code, I recommend to people to look at the github mirror, even
>>> if this mean losing some information and changelog.
>>>
>>> The issue is on this file :
>>> https://github.com/Zimbra-Community/zimbra-sources/blob/master/main/ZimbraServer/src/php/aspell.php
>>>
>>>
>>>
>>>
The problem is that $dictionary is coming from user input ( from
>>> GET parameters ), since it is a copy of $_REQUEST. Then if no
>>> text is given ( and so $text is empty ), it is printed back in
>>> the html form displayed without any kind of sanitization at all
>>> ( line133 :
>>> https://github.com/Zimbra-Community/zimbra-sources/blob/master/main/ZimbraServer/src/php/aspell.php#L133
>>>
>>>
)
>>>
>>> So a attacker could inject javascript/html there just by
>>> giving crafted link to a user, running as the domain of zimbra
>>> ( albeit on a different port ). Something like
>>> http://example.org/aspell.php?disctionnary=><script>
>>> alert('foo');</script>
>>>
>>> ( with proper url encoding of course ).
>>>
>>> Due to typecasting, "" is considered as equal to NULL for
>>> '==', while it may not be the case in other circumstances.
>>>
>>> If I am not wrong, the default location for the spell checking
>>> service is http://$config{HOSTNAME}:7780/aspell.php, so a
>>> improperly secured server ( ie, without a firewall ) could be
>>> vulnerable to javascript injection, which could be used to
>>> steal various informations ( like the session cookie ).
>>>
>>> However, depending on the browser and the security setting,
>>> the issue could be mitigated, even if it seems we can still
>>> steal the cookie with a spear phising attempt (
>>> http://seckb.yehg.net/2012/06/xss-gaining-access-to-httponly-cookie.html
>>>
>>>
)
>>>
>>> The issue can be tested quite easily, just take any php
>>> hosting, download the aspell.php file there and run :
>>>
>>> $ curl
>>> 'http://www.example.org/aspell.php?dictionary=insert_html_here_with<blink>'
>>>
>>>
>>>
You should see that the html code is inserted back in the form. I
>>> didn't spent time on writing a trivial exploit for that.
>>>
>>> Upstream have been notified on 2013-01-12 on a private bug (
>>> https://bugzilla.zimbra.com/show_bug.cgi?id=79640 ), with
>>> first answer on 2013-02-22, along with a fix following on the
>>> next hours. However, the fix is incorrect, and my attempt to
>>> make the coder change his mind failed.
>>>
>>> The fix that was written can be found on a aggregate commit on
>>>
>>> https://github.com/Zimbra-Community/zimbra-sources/commit/e7682c00be82a0c3ab51ee92f518bdcc1e07536c#L3L148
>>>
>>>
>>>
While that could fix a XSS issue if the code was correctly used,
>>> there was no security issue since the call of the function is
>>> wrong on line 67, we see 1 parameter is missing and the value
>>> of $dictionnary is overwrote by the return code and is always
>>> 0, so we cannot inject anything with it.
>>>
>>> As I couldn't convince upstream to correct this, and given that
>>> I have let enough time to react to them after following the
>>> procedure, I consider that full disclosure is the next step to
>>> have it corrected.
>>>
>>> Can someone assign a CVE for it ?
>>>
>>
>> Is this also in the open source version?
>>
>> http://wiki.zimbra.com/wiki/Building_Zimbra_using_Perforce
>
> I only used the open source version ( since I doubt the other
> version is cloned on github, that would kinda be a license
> violation ) and I do not have access to the closed source one ( or
> rather, i didn't tried very hard to have access to it to check, as
> I would not be able to link to source code for verification )
>
> However, I suspect that's the same for non open source one ( ie, I
> see no reason to have less features in the commercial version )
>
Ah sorry misread, thought you were testing against a live commercial
zimbra install the first time. Also added vmware/zimbbra security
(hopefully those email addresses exist) to the CC.
Please use CVE-2013-1938 for this issue.
- --
Kurt Seifried Red Hat Security Response Team (SRT)
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