attr Plugin

Purpose

The attr plugin for libcharon provides IKE attributes configured in strongswan.conf to peers. It is enabled by default but may be disabled with the ./configure option

--disable-attr

Behavior

Configured attributes are assigned to peers via CP configuration payloads (IKEv2) or via Mode Config (IKEv1). Attributes are only assigned to peers if they request a virtual IP address.

Configuration

The plugin is configured using the following strongswan.conf options.

Key Default Description

charon.plugins.attr.<attribute>

Attribute assigned to a peer via CP configuration payload or Mode Config

Attribute Types

Possible values for <attribute are listed in the following table. Depending on the address family of the IP address specified as value the proper IP4 or IP6 attribute type is used. A complete list of IKEv2 configuration payload (CP) attributes can be found on the IANA website. Multiple values can be specified as a comma-separated list.

IPv4 Attributes

Key Attribute Type Code Description

address

INTERNAL_IP4_ADDRESS

1

Internal IPv4 address

netmask

INTERNAL_IP4_NETMASK

2

Netmask of the internal network (in dotted decimal notation), similar to subnet but bound to the internal address

dns

INTERNAL_IP4_DNS

3

DNS server

nbns

INTERNAL_IP4_NBNS

4

WINS server

dhcp

INTERNAL_IP4_DHCP

6

DHCP server

subnet

INTERNAL_IP4_SUBNET

13

The protected sub-networks that this edge-device protects (in CIDR notation). Usually ignored in deference to local_ts, though Mac OS X clients will use this for routes

IPv6 Attributes

Key Attribute Type Code Description

address

INTERNAL_IP6_ADDRESS

8

Internal IPv6 address

netmask

INTERNAL_IP6_NETMASK

9

Netmask of the internal network (IKEv1 only)

dns

INTERNAL_IP6_DNS

10

DNS server

nbns

INTERNAL_IP6_NBNS

11

WINS server (IKEv1 only)

dhcp

INTERNAL_IP6_DHCP

12

DHCP server

subnet

INTERNAL_IP6_SUBNET

15

The protected sub-networks that this edge-device protects (in CIDR notation)

Miscellaneous IANA Attributes

The configured attribute type <integer code> as assigned by IANA. The value as defined by the referenced RFCs (see following examples), IP addresses and subnets are recognized, otherwise the literal string is used as the attribute value.

Key Attribute Type Code Description

7

APPLICATION_VERSION

7

String of printable ASCII characters that signifies the version or application of the IPsec host

18

INTERNAL_IP6_PREFIX

18

Subnet passed to the clients as prefix

Cisco Unity extensions for IKEv1 (IPv4 and IPv6)

Key Attribute Type Code Description

28672

UNITY_BANNER

28672

Message displayed on certain clients after login

28673

UNITY_SAVE_PASSWD

28673

Allow client to save Xauth password in local storage

28674

UNITY_DEF_DOMAIN

28674

Default search domain used when resolving host names via the assigned DNS servers

28675

UNITY_SPLITDNS_NAME

28675

If split tunneling is used clients might not install the assigned DNS servers globally. This space-separated list of domain names allows clients, such as Mac OS X, to selectively query the assigned DNS servers. Seems Mac OS X uses only the first item in the list

split-include

UNITY_SPLIT_INCLUDE

28676

Comma-separated list of subnets to tunnel. The unity plugin provides a connection specific approach to assign this attribute

28677

UNITY_NATT_PORT

28677

split-exclude

UNITY_LOCAL_LAN

28678

Comma-separated list of subnets not to tunnel

28679

UNITY_PFS

28679

28680

UNITY_FW_TYPE

28680

28681

UNITY_BACKUP_SERVERS

28681

28682

UNITY_DDNS_HOSTNAME

28682

Legacy Options

Key Default Description

charon.dns1

DNS server 1 assigned to peer via CP configuration payload

charon.dns2

DNS server 2 assigned to peer via CP configuration payload

charon.nbns1

WINS server 1 assigned to peer via CP configuration payload

charon.nbns2

WINS server 2 assigned to peer via CP configuration payload

Example

# the following assigns two DNS servers to peers
charon {
    plugins {
        attr {
            dns = 10.0.10.10, 10.0.20.10
        }
    }
}

# this is the same using the legacy options
charon {
    dns1 = 10.0.10.10
    dns2 = 10.0.20.10
}