Microsoft IIS 5.0/51./6.0 HTTP 401 Response Internal IP Disclosure

Microsofts IIS 5.0/5.1/6.0 Web servers seem to disclose their internal ip, when giving
a 401 HTTP response take a loook.

[11:05 PM ~]#nc -vv 127.0.0.1 267
localhost [127.0.0.1] 267 (?) open
OPTIONS / HTTP/1.0


HTTP/1.1 401 Unauthorized
Content-Length: 1656
Content-Type: text/html
Server: Microsoft-IIS/6.0
WWW-Authenticate: Basic realm="172.20.0.79"
MicrosoftOfficeWebServer: 5.0_Pub
X-Powered-By: ASP.NET
Date: Sun, 06 Nov 2005 17:39:09 GMT
Connection: close

The basic realm is set to the internal IP

NOTE: Don't fret on the port 267 thing, the whole thing is through sslproxy.

Tried it without authentication on ? Played around with the default error pages any? Isn't the realm configurable? I am pretty sure in Apache it is with AuthRealm...I would assume something similar exists for IIS (sorry I try really really hard to avoid IIS, so I haven't really played around with this part in IIS)...

Further elaboration:

From httpd.conf:

Quote:

---

AuthType Basic
AuthName "Whatever I want it to say"
AuthUserFile /etc/httpd/htpass
Require valid-user

---

Code:

---

/etc/init.d/httpd start
Starting httpd:                                            [  OK  ]
[root@localhost conf]# nc localhost 80
OPTIONS / HTTP/1.0

HTTP/1.1 401 Authorization Required
Date: Fri, 02 Dec 2005 18:09:13 GMT
Server: Apache/2.0.53 (Fedora)
WWW-Authenticate: Basic realm="Whatever I want it to say"
Content-Length: 491
Connection: close
Content-Type: text/html; charset=iso-8859-1

---

So wouldn't this be a configuration issue ? Granted I know I used Apache, but I would assume IIS would have similar functionality using .htaccess?

The realm (if specified) is also revealed in the popup window requesting authentication information.

my IIS 5.0 server replies with

Quote:

---

HTTP/1.1 401 Access Denied
Server: Microsoft-IIS/5.0
Date: Sun, 04 Dec 2005 21:17:01 GMT
WWW-Authenticate: Negotiate
WWW-Authenticate: NTLM
Content-Length: 24
Content-Type: text/html

Error: Access is Denied.

Connection to host lost.

---

I have my system configured to use Kerbose authentiation and if the client is not capable then to fall back on NTLM. The realm has been replaced by the domain and is provided by the client (since this system is connected to several domains)

Review: http://www.owasp.org/columns/jlima/joelima2.html for more information on IIS authentication. It is not a great article, but the MS info is kinda spread... and this is simple and concise.

Lastly view:
http://www.microsoft.com/windows2000...p/apro9ael.htm
for information about modifying the realm settings in the metabase.

cheers,

catch