SVG:Advisory-SVG-2015-8183

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Advisory-SVG-2015-8183




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EGI SVG   ADVISORY [EGI-SVG-2015-8183] 

Title:       EGI SVG Advisory - dCache vulnerability for some access methods [SVG EGI-SVG-2015-8183]

Date:        2014-02-20  
Updated:     


URL:         https://wiki.egi.eu/wiki/SVG:Advisory-SVG-2015-8183

Introduction
============

A vulnerability has been found in dCache where username and password authenticating 
FTP doors have been accidentally set to allow 'write' access by default, whereas 
they should be 'read' access only.

Most deployments in EGI should not be vulnerable to this, as access is X.509 based 
with authorization methods in place and this vulnerability is not exploitable.

If a site has set up an FTP door which allows read access to public data, not via 
the EGI recommended access methods, then a user may be able to delete and modify 
files. 

Note also that the version in the EGI UMD is not vulnerable as the version in the 
EGI UMD is version 2.6, and this vulnerability was introduced in dCache 2.7 and 
higher. 


Details
=======

dCache supports the FTP protocol with three authentication schemes:
GSI ("GridFTP"), Kerberos and Plain. The last option supports username and password 
authentication and sends data unencrypted over the network; therefore, it is also 
known as the "weak" FTP door.

In general, dCache doors (FTP, HTTP, dcap, ...) may be configured read-write 
(ftp.authz.readonly=false for the FTP door) or read-only (ftp.authz.readonly=true). 
A read-write door allows clients to both read and modify dCache contents, whereas a 
read-only door only allows clients to read contents. All attempts to modify dCache 
through a read-only door will be rejected.

Irrespective of whether the door is read-write or read-only, the other authorisation 
schemes still apply. For example, a user will still only be able to read files that 
the namespace (file and directories) allows. Similarly, a user can only write into 
those directories that she is authorised to do so.

Each of the three FTP authentication schemes have independent default 
ftp.authz.readonly values. For GSI-FTP and Kerberos-FTP the default is read-write. 
In dCache v2.6, the default for Plain-FTP is read-only. A mistake was recently 
discovered where, in dCache v2.7, the default for Plain-FTP changed to read-write. 
This is unintended.

With the release of dCache v2.11.9, 2.10.18, 2.9.21, 2.8.25 and 2.7.29, the default 
behaviour for Plain-FTP doors is read-only, in keeping with dCache v2.6.


Risk category
=============

Since the standard EGI deployment is not vulnerable, we have not carried out a risk 
assessment for EGI, but send this advisory in case some sites have a vulnerable 
configuration.  


Affected software
=================

dCache release 2.7 and higher prior to the fixed releases.  

Fixed in releases v2.11.9, 2.10.18, 2.9.21, 2.8.25 and 2.7.29 and higher. 


Mitigation
==========

Vulnerable sites should explicitly configured to be read-only.

Alternatively, update to a non-vulnerable version. 

Component installation information
==================================

Note that the version in the EGI UMD is not vulnerable.

Sites which have a vulnerable version should see [R 1]



Recommendations
===============

Sites should check whether they allow access to data via plain username and 
password. 

If sites are allowing username and password access to data then they should either 
update to a non-vulnerable version directly from the dCache site [R 1] or take 
mitigating action. 

Credit
======

This vulnerability was reported by Patrick Fuhrmann and Paul Millar from the dCache 
team. 


References
==========

[R 1] http://www.dcache.org/downloads/IAgree.shtml


Timeline  
========
Yyyy-mm-dd

2015-02-05 Vulnerability reported by Patrick Fuhrmann and Paul Millar 
2015-02-05 Acknowledgement from the EGI SVG to the reporter
2015-02-06 Updated packages available at the dCache site
2015-02-20 Alert sent to sites
2015-02-20 Public disclosure.