Microsoft has responded to my report to secure@microsoft.com and I can now disclose what I found.
There is a minor bug on the MS Server 2008 DNS service that responds
with the list of all root servers when queried for non-authoritative
domains, EVEN when recursion is set to OFF. This allows a malicious
party to spoof the source ip on a udp DNS request to any MS Server 2008
DNS and elicit a 533 byte response to a victim, making the server a
contributor to coordinated Distributed Denial of Service attacks. The
response contains the default list of root DNS servers.
Version tested: MS DNS on MS Server 2008 R2 version 6.1.7601.17514
Server is Authoritative to only one .com domain.
Config Parameters:
DNS Recursion set to "disable"
Enable Round Robin
Enable Netmask Ordering
Secure Cache against pollution
And My Mitigation steps:
Remove all root DNS servers listed on the "Root Hints" tab.
This will not negatively affect the DNS functionality of the server
when deployed only as an authoritative server for a specific domain.
Although RFC1034
on page 21 does allow the DNS to reply with the list of root servers (if
configured) as a response option, ultimately it is preferable for it to
mimic the behavior of BIND and not respond at all under these test
conditions, to discourage abuse from malicious entities.
More details with images and packet captures and MS responses, in my web file http://pe.lúka.com/
Pedro
CCNP, CCDA, CCNA-Security, SANS GPEN
...But mostly a curious guy.
There is a minor bug on the MS Server 2008 DNS service that responds
with the list of all root servers when queried for non-authoritative
domains, EVEN when recursion is set to OFF. This allows a malicious
party to spoof the source ip on a udp DNS request to any MS Server 2008
DNS and elicit a 533 byte response to a victim, making the server a
contributor to coordinated Distributed Denial of Service attacks. The
response contains the default list of root DNS servers.
Version tested: MS DNS on MS Server 2008 R2 version 6.1.7601.17514
Server is Authoritative to only one .com domain.
Config Parameters:
DNS Recursion set to "disable"
Enable Round Robin
Enable Netmask Ordering
Secure Cache against pollution
And My Mitigation steps:
Remove all root DNS servers listed on the "Root Hints" tab.
This will not negatively affect the DNS functionality of the server
when deployed only as an authoritative server for a specific domain.
Although RFC1034
on page 21 does allow the DNS to reply with the list of root servers (if
configured) as a response option, ultimately it is preferable for it to
mimic the behavior of BIND and not respond at all under these test
conditions, to discourage abuse from malicious entities.
More details with images and packet captures and MS responses, in my web file http://pe.lúka.com/
Pedro
CCNP, CCDA, CCNA-Security, SANS GPEN
...But mostly a curious guy.