[secdir] SecDir review of draft-ietf-dhc-dhcpv4-bulk-leasequery-05

[Yaron Sheffer <[e-mail]>]

I have reviewed this document as part of the security directorate's 
ongoing effort to review all IETF documents being processed by the IESG. 
These comments were written primarily for the benefit of the security 
area directors.  Document editors and WG chairs should treat these 
comments just like any other last call comments.

The document defines a protocol extension that allows infrastructure 
components in DSL/cable networks to query a master DHCP server for its 
static and/or dynamic bindings, to allow them to quickly recovery after 
reboot.

Summary

In my opinion, a major security issue is not covered sufficiently.

Details

I have not reviewed the protocol itself in depth. However I believe that 
it suffers from the "recursive security considerations" syndrome, where 
the current draft depends on RFC 4388 (6 years old) for its security, 
which in turn refers to RFC 3118 (11 years old) for parts of its 
security. IMHO the relevant threats for a bulk DHCP query are very 
different from those that RFC 3118 considered for generic DHCP.

I worry most about the privacy implications: if I am a subscriber in 
Smalltown, pop. 10,000, I may be sharing a single DHCP server with the 
entire population. If any subscriber can issue a bulk query for the 
whole town once every hour, and thereby map any IP address to a MAC 
address, this has a serious effect on subscribers' privacy.

This is what the current draft says about access control:

Servers MAY restrict Bulk Leasequery connections and DHCPBULKLEASEQUERY 
messages to certain requestors.  Connections not from permitted 
requestors SHOULD be closed immediately, to avoid server connection 
resource exhaustion.  Servers MAY restrict some requestors to certain 
query types.  Servers MAY reply to queries that are not permitted with 
the DHCPLEASEQUERYDONE message with a status-code option status of 
NotAllowed, or MAY simply close the connection.

This IMHO is way too weak, specifically the first MAY. The Security 
Considerations refer to RFC 4388 for "restriction to trusted 
requestors", but I couldn't find any relevant language there either, 
other than a reference to RFC 3118.

Thanks,
     Yaron