I'm not familiar with ExternalFile, but likely plan to use it in the future. I think a list of expressly permitted directory locations (including all subdirectories) might be more secure. You can't go wrong with a default directory for files (perhaps $INSTANCE_HOME/var/files or something?), but otherwise an implicit deny all - then leave it up to the user to edit some access list file in the product (for example, call it 'diraccess.txt'). Does this seem reasonable?
Sean -----Original Message----- From: Craeg K Strong [mailto:cstrong@;arielpartners.com] Sent: Thursday, November 07, 2002 8:25 AM To: Jonagustine Lim Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: [Zope-dev] Re: Unsecure design of ExternalFile Yikes! Scary stuff. However, here are some things to consider: a) ExternalFile advertises itself as being a developers/ content authors tool, not really for production. Of course, most folks end up using it for production, anyway... ;-) b) Once created, an ExternalFile cannot be retargetted to point to another file in the file system c) The permission to create an ExternalFile instance is different than the permission to edit one. The permission to create an ExternalFile instance should be assigned judiciously... d) the Zope server should be run as a user that has very limited permissions. e) Even if a user *does* have permission to edit an ExternalFile, they only have whatever permission the user running the Zope server has. If the Zope user (usually "webserver" or something like that) does not have permission to write to /etc/passwd, it doesn't matter if you create an ExternalFile pointing to it, you still can't write to it... However, the points you raise are valid, as they are Zope-specific, and the zope user "webserver" *would* probably have permission to do your (1) and (2) examples. What would you recommend? Perhaps there should be a predefined list of "forbidden" directories for ExternalFiles? The problem is that-- in the development scenario-- the very things you mention below might be what you legitimately *want* to do as a developer. Well, thanks for pointing this out. Let's continue the conversation a bit, perhaps a good solution will reveal itself (even if it is only some kind of warning in the documentation...) Regards, --Craeg PS I am CC-ing the zope-dev mailing list, as I think this warrants a wider audience Jonagustine Lim wrote: > Hi! > > I just noticed that it's possible to create or replace > any files in the filesystem using the ZMI with > ExternalFile installed. > > Possible exploits: > > 1. Use ExternalFile web interface to replace Zope > Data.fs > > 2. Create a .py file in /Zope/Extensions and run it by > creating an Extenal Method. > > Anyway, I hope you can fix this or put a warning up. > > Jon > _______________________________________________ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope ) _______________________________________________ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )