V-254058

Discussion

The optional and extensible natures of the IPv6 extension headers require higher scrutiny since many implementations do not always drop packets with headers that it cannot recognize, and hence could cause a denial-of-service on the target device. In addition, the type, length, value (TLV) formatting provides the ability for headers to be very large. This option type from RFC 1888 (OSI NSAPs and IPv6) has been deprecated by RFC 4048.

Check Content

This requirement is not applicable for the DODIN Backbone. 

Review the router configuration and determine if filters are bound to the applicable interfaces to drop IPv6 packets containing a Destination Option header with option type value of 0xC3 (NSAP address). 

Verify the router drops all destination-options extension headers.
[edit firewall family inet6]
filter <name> {
    term 1 {
        from {
            next-header dstopts;
        }
        then {
            log;
            syslog;
            discard;
        }
    }
    <additional terms>
    term default {
        then {
            log;
            syslog;
            discard;
        }
    }
}

Note: Juniper routers do not support configuring option types for Destination Options extension headers. Therefore, all packets with the Destination Options extension header are dropped.

Verify the filter is applied to applicable interfaces.
[edit interfaces]
<interface name> {
    unit <number> {
        family inet6 {
            filter {
                input <filter name>;
            }
            address <IPv6 address>.<prefix>;
        }
    }
}
Note: Some Juniper devices support both monolithic filters and filter lists. Filter lists separate each term, or set of terms, into a separate filter that is applied sequentially to an interface. If using filter lists, the keywords "input" or "output" change to "input-list" or "output-list". Verify the final list item is a deny-all filter. The deny-all filter is created once per family and can be reused across multiple lists. For example:

input-list [ permit_mgt permit_routing_protocols default-deny ];

If the router is not configured to drop IPv6 packets containing the NSAP address option within Destination Option header, this is a finding.