Re: Restrict access to Velocity's capabilities

[Mike Kienenberger]

Ben [EMAIL PROTECTED] wrote:
 Hi
 
 I have been using Velocity throughout my site and I am in awe with its
 capabilities. However there are situations where I need to restrict
 its capabilities to a certain extend.
 
 For example, my site allows users to upload templates and be able to
 use a number of predefined variables. What I don't want them to do is
 to use Velocity to abuse the system, such as using directives and
 writing macros.
 
 Is there a way to create a Velocity instance with directives and other
 features disabled? The only thing I need is reference to variables.

The best thing to do is simply escape all # symbols when it's uploaded.   
Ie, replace them with $esc.hash or something equivalent.

Personally, I'd go a step further and escape all $ symbols as well, then 
manually unescape any instance of ${esc.dollar}allowed_variable_name back to 
${allowed_variable_name} where allowed variable name is in a preset list.

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Re: Restrict access to Velocity's capabilities

[Will Glass-Husain]

Hi Ben,
Restricting access is a tricky issue.  We have a publically available system 
in which hundreds of users upload templates.  I've written a few thoughts on 
how to have a secure server environment here:

http://wiki.apache.org/jakarta-velocity/BuildingSecureWebApplications
Abusing the system is a matter of definition.  If what you mean is not to 
allow them to mess with other users, you'll want to install a custom 
introspector to prevent calls to system classes and you'll need to modify 
#include and #parse to prevent users from viewing the contents of other 
users templates.  You can write your own classloader now.
There's a patch in the works that will let you make the second of those 
modifications.
http://issues.apache.org/bugzilla/show_bug.cgi?id=28388

Otherwise, macros and directives seem pretty harmless to me.
Best,
WILL
- Original Message - 
From: Ben [EMAIL PROTECTED]
To: Velocity velocity-user@jakarta.apache.org
Sent: Sunday, January 23, 2005 10:04 PM
Subject: Restrict access to Velocity's capabilities


Hi
I have been using Velocity throughout my site and I am in awe with its
capabilities. However there are situations where I need to restrict
its capabilities to a certain extend.
For example, my site allows users to upload templates and be able to
use a number of predefined variables. What I don't want them to do is
to use Velocity to abuse the system, such as using directives and
writing macros.
Is there a way to create a Velocity instance with directives and other
features disabled? The only thing I need is reference to variables.
Thanks,
Ben
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