This is a security advisory for TWiki 4.0 installations:
Unauthorized user may gain TWiki admin group privileges
with a custom registration form.
TOC:
* Vulnerable Software Version
* Attack Vectors
* Impact
* Severity Level
* MITRE Name for this Vulnerability
* Details
* Countermeasures
* Authors and Credits
* Hotfix for TWiki 4.0.0, 4.0.1 and TWiki 4.0.2
* Feedback
* External Links
---++ Vulnerable Software Version
* TWikiRelease04x00x02 -- TWiki-4.0.2.zip
* TWikiRelease04x00x01 -- TWiki-4.0.1.zip
* TWikiRelease04x00x00 -- TWiki-4.0.0.zip
---++ Attack Vectors
TWiki's registration process can be invoked with a crafted
version of the original HTML form in which the action
attribute of the form element has been modified to point
to the Sandbox web instead of the user web.
In this case, TWiki's validation fails to correctly check
whether the wikiname of the user has already been registered.
The wikiname's user topic is looked for in the web as given by
the action attribute instead of the user web.
An attacker can use this to register with his own login name,
stealing a wiki name which has already been registered.
---++ Impact
In a TWiki where login names are allowed, an attacker can snatch
the WikiName of a known member of the TWikiAdminGroup and
associate it with his own login name. After login, the attacker
can act with the privileges of TWikiAdminGroup, i.e. unlimited
access with regard to the TWiki topics.
Even if there is no known threat to TWiki 4 installations with
{MapUserToWikiName} flag unchecked in configure, it is
recommended that all TWiki 4 installations have this hotfix
installed so that the registration code is clean and safe from
further exploits.
---++ Severity Level
The TWiki SecurityTeam [3] triaged this issue as documented in
TWiki Security Alert Process [2] and assigned the following
severity level:
* Severity 2 issue: The TWiki installation is compromised
---++ MITRE Name for this Vulnerability
The Common Vulnerabilities and Exposures project has assigned the
name CVE-2006-2942 to this vulnerability [4].
---++ Details
How to reproduce:
Take a copy of the HTML version of TWiki.TWikiRegistration, and
change the action parameter in the form from
...bin/register/Main/WebHome to .../bin/register/Sandbox/WebHome.
Using the modified form, register with the WikiName of a member
of the TWikiAdminGroup, but provide the attacker's login name.
The registration "succeeds" to a sufficient extent: TWiki
creates a new "personal homepage" for the attacker in the
Sandbox web, but this doesn't matter. TWikiUsers is changed,
and is now showing the attacker's login name next to the
administrator's WikiName.
Why this succeeds:
During the registration process, the code "verifies" the form
data, and during this verification process tries to check
whether the user home page exists. However, when doing so, it
does not refer explicitly to the users web. The offending line
is:
if($session->{store}->topicExists( $data->{webName},
$data->{WikiName} )) {
In this line, and again when trying to create the user home page,
TWiki should under no circumstances rely on the data provided by
the query, but always use =$TWiki::cfg{UsersWebName}=.
---++ Countermeasures
* Apply hotfix
* Upgrade to TWiki 4.0.3 (to be released in a few days)
---++ Authors and Credits
* Credit to TWiki:Main.HaraldJoerg for disclosing the issue
to the twiki-security mailing list
* TWiki:Main.HaraldJoerg for providing a fix and for fixing
the code for TWiki 4.0.3
* TWiki:Main.KennethLavrsen for creating a hotfix
* TWiki:Main.PeterThoeny and TWiki:Main.KennethLavrsen for
creating the advisory
---++ Hotfix for TWiki 4.0.0, 4.0.1 and TWiki 4.0.2
A hotfix for all released versions of TWiki 4.0.X has been attached
to the security alert topic,
http://twiki.org/cgi-bin/view/Codev/SecurityAlertTWiki4PrivilegeElevation
The hotfix updates one single file: lib/TWiki/UI/Register.pm.
The hotfix is provided in two formats: Patch file or a new
replacement Register.pm file. The patch file is the best option
if you have altered the TWiki code yourself. The replacement file
is the simpler choice for most. All you need to do is replace the
file provided.
* CVE-2006-2942-hotfix-4.0.0-4.0.2.diff - Patch file
for lib/TWiki/UI/Register.pm. This patch file is compatible
with 4.0.0, 4.0.1 and 4.0.2. Change directory to lib/TWiki/UI,
copy the patch file to this directory and apply the patch with
the command: patch < CVE-2006-2942-hotfix-4.0.0-4.0.2.diff.
You can delete the patch file afterwards.
* CVE-2006-2942-Register.pm-4.0.0-4.0.1.zip - Replacement file
lib/TWiki/UI/Register.pm for TWiki 4.0.0 and TWiki 4.0.1
* CVE-2006-2942-Register.pm-4.0.2.zip - Replacement file
lib/TWiki/UI/Register.pm for TWiki 4.0.2
---++ Feedback
Please provide feedback at
http://twiki.org/cgi-bin/view/Codev/SecurityAlertTWiki4PrivilegeElevation
---++ External Links
[1]:
http://twiki.org/cgi-bin/view/Codev/SecurityAlertTWiki4PrivilegeElevation
[2]: http://twiki.org/cgi-bin/view/Codev/TWikiSecurityAlertProcess
[3]: http://twiki.org/cgi-bin/view/Codev/SecurityTeam
[4]: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2942
-- Contributors: Main.HaraldJoerg, Main.CrawfordCurrie,
Main.PeterThoeny, Main.KennethLavrsen - 16 Jun 2006
--
* Peter Thoeny Peter@private
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