Description: Although IIS5 is very old, finding one is not impossible! Therefore, I want to introduce a technique to bypass the IIS authentication methods on a directory. This vulnerability is because of using Alternate Data Stream to open a protected folder. All of IIS authentication methods can be circumvented. In this technique, we can add a ?:$i30:$INDEX_ALLOCATION? to a directory name to bypass the authentication. In a protected folder such as ?AuthNeeded? which includes ?secretfile.asp?: It is possible to run ?secretfile.asp? by using: ?/AuthNeeded:$i30:$INDEX_ALLOCATION/secretfile.asp? Instead of: ?/AuthNeeded/secretfile.asp? More description: Why IIS6 and 7 are not vulnerable: - In these versions, IIS does not accept colon (?:?) character from the URL before the querystring. Why we cannot use ?::$Data? in IIS 5.1 anymore: - IIS rejects the request if its URL contains ?::$? (before querystring). Why IIS5 is vulnerable to ?Directory Authentication Bypass? by using ?:$I30:$Index_Allocation?: - IIS only verifies the directory name to check for authentication. Therefore, we can use ?http://victim.com/SecretFolder:$I30:$Index_Allocation/? instead of ?http://victim.com/SecretFolder? to bypass the authentication. Is it possible to bypass something else by using ?:$I30:$Index_Allocation? on a NTFS partition: - If a checking is only based on the directory name, it can be bypassed by using this method. Download this advisory from: http://soroush.secproject.com/downloadable/IIS5.1_Authentication_Bypass.pdf or: http://0me.me/demo/IIS/IIS5.1_Authentication_Bypass.pdf More here: http://soroush.secproject.com/blog/2010/07/iis5-1-directory-authentication-bypass-by-using-i30index_allocation/
