CAN-2004-0749-advisory.txt   [plain text]

            mod_authz_svn fails to protect metadata 

Summary:
=======

mod_authz_svn, the Apache httpd module which does path-based
authorization on Subversion repositories, is not correctly protecting
all metadata on unreadable paths.  

This metadata leakage affects the mod_authz_svn module in all released
versions of Subversion (through 1.0.7), as well as the 1.1-rc1, -rc2
and -rc3 release candidates.  The leakage is fixed in the 1.0.8 and 
1.1-rc4 release, as well as the upcoming 1.1 final release.


Details:
=======

If a Subversion commit affects paths that an administrator has marked
"unreadable" using mod_authz_svn, then 

   - "svn log -v" will list the existence of the unreadable paths;
   - "svn log -v" will show the commit's log message, which might be
                  considered sensitive metadata in some situations;
   - "svn propget" is also able to fetch the log message of any commit;
   - "svn blame" and other commands that follow renames are able to
                  acknowledge the existence of earlier versions of
                  files that exist at unreadable locations.

Severity:
========

Mild-to-medium severity, depending on your situation.

This security issue is not about revealing the contents of protected
files: it only reveals metadata about protected areas such as paths
and log messages.  This may or may not be important to your
organization, depending on how you're using path-based authorization,
and the sensitivity of the metadata.

(Exception: in the case of "svn blame", and only in svn 1.1-rc2 and
-rc3, it's possible that older unreadable versions of a file are being
transported from server to client; the contents aren't displayed, but
the data is still traveling over the network.)

These issues only affects users of mod_authz_svn, not people using
native httpd.conf directives (such as <Limit> or <LimitExcept>)
directives to limit general readability on whole repositories.


Workarounds:
===========

* Use mod_authz_svn to restrict writes only, not reads.

* Break unreadable areas into separate repositories, and use native
  apache httpd.conf directives to make them unreadable.


References:
==========

  CAN-2004-0749: mod_authz_svn fails to protect metadata

Recommendation:
==============

We recommend an upgrade to 1.0.8 or 1.1.0-rc4.