The administrator must ensure the perimeter router is configured to drop all inbound and outbound IPv6 packets containing a Hop-by-Hop or Destination Option extension header with an undefined option type.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-30657	NET-IPV6-064	SV-40449r1_rule		Medium

Description
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 can’t recognize and hence could cause a DoS on the target device. In addition, the type, length, value (TLV) formatting provides the ability for headers to be very large. According to the DoD IPv6 IA Guidance for MO3, extension headers with an unknown option type value should not be allowed into or out of any network (S0-C2-opt-3).

Description

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 can’t recognize and hence could cause a DoS on the target device. In addition, the type, length, value (TLV) formatting provides the ability for headers to be very large. According to the DoD IPv6 IA Guidance for MO3, extension headers with an unknown option type value should not be allowed into or out of any network (S0-C2-opt-3).

STIG	Date
Perimeter Router Security Technical Implementation Guide Juniper	2017-06-29

Details

Check Text ( C-39282r1_chk )
Review the perimeter router or multi-layer switch configuration and determine if filters are bound to the applicable interfaces to drop all inbound and outbound IPv6 packets containing an undefined option type value regardless of whether they appear in a Hop-by-Hop or Destination Option header. Undefined values are 0x02, 0x03, 0x06 through 0x89 inclusive, 0x8B through 0xC1 inclusive, 0xC4 through 0xC8 inclusive, and anything greater than 0xC9. The following example will block any inbound IPv6 packet containing a Hop-by-Hop or Destination Option header: interfaces fe-0/0/1 { unit 0 { family inet6 { filter { input IPV6-INGRESS-FILTER; } address 2001:1:0:146::4/64; } } } firewall { filter IPV6-INGRESS-FILTER { term DROP- HOP-BY-HOP { from { next-header { hop-by-hop; } } then { syslog; discard; } } term DROP-DEST-OPT { from { next-header { dstops; } } then { syslog; discard; } } … … term default-action { then { syslog; discard; } } } } Note: Currently JUNOS has no method to filter option type within either Hop-by-Hop or Destionation Option header. Hence, all packets with a Hop-by-Hop or Destionation Option headers must be dropped.

Check Text ( C-39282r1_chk )

Review the perimeter router or multi-layer switch configuration and determine if filters are bound to the applicable interfaces to drop all inbound and outbound IPv6 packets containing an undefined option type value regardless of whether they appear in a Hop-by-Hop or Destination Option header. Undefined values are 0x02, 0x03, 0x06 through 0x89 inclusive, 0x8B through 0xC1 inclusive, 0xC4 through 0xC8 inclusive, and anything greater than 0xC9.

The following example will block any inbound IPv6 packet containing a Hop-by-Hop or Destination Option header:

interfaces fe-0/0/1 {
unit 0 {
family inet6 {
filter {
input IPV6-INGRESS-FILTER;
}
address 2001:1:0:146::4/64;
}
}
}

firewall {
filter IPV6-INGRESS-FILTER {
term DROP- HOP-BY-HOP {
from {
next-header {
hop-by-hop;
}
}
then {
syslog;
discard;
}
}
term DROP-DEST-OPT {
from {
next-header {
dstops;
}
}
then {
syslog;
discard;
}
}
…
…
term default-action {
then {
syslog;
discard;
}
}
}
}

Note: Currently JUNOS has no method to filter option type within either Hop-by-Hop or Destionation Option header. Hence, all packets with a Hop-by-Hop or Destionation Option headers must be dropped.

Fix Text (F-34387r1_fix)
Configure the perimeter router or multi-layer switch to drop all inbound and outbound IPv6 packets containing an undefined option type value regardless of whether they appear in a Hop-by-Hop or Destination Option header. Undefined values are 0x02, 0x03, 0x06 through 0x89 inclusive, 0x8B through 0xC1 inclusive, 0xC4 through 0xC8 inclusive, and anything greater than 0xC9.