Active Server Pages Security Context

To understand the security of SA-FileUp, it is necessary to have background knowledge in IIS and ASP security.

ASP provides three levels of authentication:

• Anonymous
• Basic
• NT Challenge/Response

When a user hits a web page, the security of the page is verified. If there are no restrictions, such as NTFS permissions, anonymous access is used. When there are NTFS permissions in place, IIS will negotiate with the browser and determine if the user can be authenticated.

IIS uses a special NT account, typically called IUSR_MachineName, as the default anonymous account. An administrator can change this default account. With IIS3, there was only one anonymous account for the entire server. With IIS 4 or later, it is possible to have different anonymous accounts for each virtual server or web application on the server.

With Basic and NT Challenge/Response, an authentication mechanism is in place that identifies the user who is requesting the page. With either Basic or NT Challenge/Response, IIS/ASP will actually perform an NT login for that specific user.

This means that a given page is executing as a specific NT user: either IUSR_MachineName or the actual authenticated NT domain user. This technique is known as impersonation and is a standard feature of NT Services.

Use SA-FileManager's CurrentUser property to view the security context of the current page.

This has strong implications for SA-FileUp. When SA-FileUp attempts to create, read or write files, it will be executing in the security context provided by IIS/ASP.

If a non-authenticated user is uploading a file, SA-FileUp will only be able to write to locations that are accessible by the IUSR_MachineName account.

If an authenticated user is uploading a file, SA-FileUp will only be able to write to locations determined by that specific user's NT domain permissions.