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** WHITE information - Unlimited distribution allowed ** ** see https://wiki.egi.eu/wiki/EGI_CSIRT:TLP for distribution restrictions ** 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.