Access Denied (Temporarely) to Virtual Directory for FTP User Account
Posted on 2009-04-22
I am having a problem with a Windows 2003 Server Standard Edition SP2 running IIS6.
On that machine is FTP configured using the IIS6 User Isolation feature. FTP Users are all local users. Because of the isolation mode, the home folder structure for the FTP server looks like this:
User1 has access to the Web server root folder on the same drive. To do this, a virtual directory was created for user1, which maps to the web root folder (e.g. c:\WWW) That user1 is able to see the virtual directory, an empty folder was created under the FTP home directory of that user also. Like this c:\FTPRoot\LocalUser\user1\WWW
The user has full permission to all files and folders, including all levels of the FTP tree and WWW, in IIS and Windows permissions. The FTP user is not a server administrator. It's just a regular user.
One additional setting that I should mention is that for the FTP home directory and subsequent sub folders the access was restricted to only allow a few specified IP addresses from where user1 is allowed to connect to the server.
During regular file transfers does it occur frequently that user1 suddenly looses access to the WWW virtual directory, returning the error that user1 has insufficient permissions to access the folder/virtual directory. After 10-15 minutes being disconnected from the FTP, user1 has full access to the virtual directory again. User1 can always connect to the FTP and access his FTP home directory and only looses access to the VD. The FTP sipply returns an "Access Denied" error message.
I have no idea what causes this temporary lock-out. It seems to be related to the amount or frequency of connections made. The easiest way to cause the lock is to start a batch upload of many small files to the server with a FTP client that creates new connections for each file to transfer (like CuteFTP). Also the access with a source code editor with FTP support and frequent "saving" of a script on the server has the same effect.
I would be glad for any tips and ideas regarding the cause of this odd behavior and how to get around it. Thanks.