iked.conf(5) - OpenBSD manual pages

iked.conf is the configuration file for iked(8), the Internet Key Exchange version 2 (IKEv2) daemon for IPsec. IPsec itself is a pair of protocols: Encapsulating Security Payload (ESP), which provides integrity and confidentiality; and Authentication Header (AH), which provides integrity. The IPsec protocol itself is described in ipsec(4).

In its most basic form, a flow is established between hosts and/or networks, and then Security Associations (SA) are established, which detail how the desired protection will be achieved. IPsec uses flows to determine whether to apply security services to an IP packet or not. iked(8) is used to set up flows and establish SAs automatically, by specifying ‘ikev2’ policies in iked.conf (see AUTOMATIC KEYING POLICIES, below).

Alternative methods of setting up flows and SAs are also possible using manual keying or automatic keying using the older ISAKMP/Oakley a.k.a. IKEv1 protocol. Manual keying is not recommended, but can be convenient for quick setups and testing. See ipsec.conf(5) and isakmpd(8) for more information about manual keying and ISAKMP support.

IKED.CONF FILE FORMAT

iked.conf is divided into three main sections:

Macros: User-defined variables may be defined and used later, simplifying the configuration file.
Global Configuration: Global settings for iked(8).
Automatic Keying Policies: Policies to set up IPsec flows and SAs automatically.

Lines beginning with ‘#’ and empty lines are regarded as comments, and ignored. Lines may be split using the ‘\’ character.

Argument names not beginning with a letter, digit, or underscore must be quoted.

Addresses can be specified in CIDR notation (matching netblocks), as symbolic host names, interface names, or interface group names.

Additional configuration files can be included with the include keyword, for example:

include "/etc/macros.conf"

MACROS

Macros can be defined that will later be expanded in context. Macro names must start with a letter, digit, or underscore, and may contain any of those characters. Macro names may not be reserved words (for example flow, from, esp). Macros are not expanded inside quotes.

For example:

remote_gw = "192.168.3.12"
ikev2 esp from 192.168.7.0/24 to 192.168.8.0/24 peer $remote_gw

GLOBAL CONFIGURATION

Here are the settings that can be set globally:

set active: Set iked(8) to active mode. This is the default.
set passive: Set iked(8) to passive mode. In passive mode no packets are sent to peers and no connections are initiated by iked(8). This option is used for setups using sasyncd(8) and carp(4) to provide redundancy. iked will run in passive mode until sasyncd has determined that the host is the master and can switch to active mode.
set couple: Load the negotiated security associations (SAs) and flows into the kernel. This is the default.
set decouple: Don't load the negotiated SAs and flows from the kernel. This mode is only useful for testing and debugging.
set ocsp URL: Enable OCSP and set the URL of the OCSP responder. Please note that the matching responder and issuer certificates have to be placed in /etc/iked/ocsp/responder.crt and /etc/iked/ocsp/issuer.crt.
user name password: iked(8) supports user-based authentication by tunneling the Extensible Authentication Protocol (EAP) over IKEv2. In its most basic form, the users will be authenticated against a local, integrated password database that is configured with the user lines in iked.conf and the name and password arguments. Note that the password has to be specified in plain text which is required to support different challenge-based EAP methods like EAP-MD5 or EAP-MSCHAPv2.

AUTOMATIC KEYING POLICIES

This section is used to configure policies that will be used by iked(8) to set up flows and SAs automatically. Some examples of setting up automatic keying:

# Set up a VPN:
# First between the gateway machines 192.168.3.1 and 192.168.3.2
# Second between the networks 10.1.1.0/24 and 10.1.2.0/24
ikev2 esp from 192.168.3.1 to 192.168.3.2
ikev2 esp from 10.1.1.0/24 to 10.1.2.0/24 peer 192.168.3.2

For incoming connections from remote peers, the policies are evaluated in sequential order, from first to last. The last matching policy decides what action is taken; if no policy matches the connection, the default action is to ignore the connection attempt or to use the default policy, if set. Please also see the EXAMPLES section for a detailed example of the policy evaluation.

The first time an IKEv2 connection matches a policy, an IKE SA is created; for subsequent packets the connection is identified by the IKEv2 parameters that are stored in the SA without evaluating any policies. After the connection is closed or times out, the IKE SA is automatically removed.

The commands are as follows:

ikev2 [name]

The mandatory ikev2 keyword will identify an IKEv2 automatic keying policy. name is an optional arbitrary string identifying the policy. The name should only occur once in iked.conf or any included files. If omitted, a name will be generated automatically for the policy.

[eval]

The eval option modifies the policy evaluation for this policy. It can be one of quick, skip or default. If a new incoming connection matches a policy with the quick option set, that policy is considered the last matching policy, and evaluation of subsequent policies is skipped. The skip option will disable evaluation of this policy for incoming connections. The default option sets the default policy and should only be specified once.

[mode]

mode specifies the IKEv2 mode to use: one of passive or active. When passive is specified, iked(8) will not immediately start negotiation of this tunnel, but wait for an incoming request from the remote peer. When active is specified, negotiation will be started at once. If omitted, passive mode will be used.

[ipcomp]

The keyword ipcomp specifies that ipcomp(4), the IP Payload Compression protocol, is negotiated in addition to encapsulation. The optional compression is applied before packets are encapsulated.

[encap]

encap specifies the encapsulation protocol to be used. Possible protocols are esp and ah; the default is esp.

[af]

This policy only applies to endpoints of the specified address family which can be either inet or inet6. Note that this only matters for IKEv2 endpoints and does not restrict the traffic selectors to negotiate flows with different address families, e.g. IPv6 flows negotiated by IPv4 endpoints.

proto protocol

The optional proto parameter restricts the flow to a specific IP protocol. Common protocols are icmp(4), tcp(4), and udp(4). For a list of all the protocol name to number mappings used by iked(8), see the file /etc/protocols.

from src [port sport] [(srcnat)] to dst [port dport]

Specify one or more traffic selectors for this policy which will be used to negotiate the IPsec flows between the IKEv2 peers. During the negotiation, the peers may decide to narrow a flow to a subset of the configured traffic selector networks to match the policies on each side.

Each traffic selector will apply for packets with source address src and destination address dst. The keyword any will match any address (i.e. 0.0.0.0/0). If the src argument specifies a fictional source ID, the srcnat parameter can be used to specify the actual source address. This can be used in outgoing NAT/BINAT scenarios as described below.

The optional port modifiers restrict the traffic selectors to the specified ports. They are only valid in conjunction with the tcp(4) and udp(4) protocols. Ports can be specified by number or by name. For a list of all port name to number mappings used by ipsecctl(8), see the file /etc/services.

local localip peer remote

The local parameter specifies the address or FQDN of the local endpoint. Unless the gateway is multi-homed or uses address aliases, this option is generally not needed.

The peer parameter specifies the address or FQDN of the remote endpoint. For host-to-host connections where dst is identical to remote, this option is generally not needed as it will be set to dst automatically. If it is not specified or if the keyword any is given, the default peer is used.

ikesa auth algorithm enc algorithm prf algorithm group group

These parameters define the mode and cryptographic transforms to be used for the IKE SA negotiation, also known as phase 1. The IKE SA will be used to authenticate the machines and to set up an encrypted channel for the IKEv2 protocol.

Possible values for auth, enc, prf, group, and the default proposals are described below in CRYPTO TRANSFORMS. If omitted, iked(8) will use the default proposals for the IKEv2 protocol.

childsa auth algorithm enc algorithm group group

These parameters define the cryptographic transforms to be used for the Child SA negotiation, also known as phase 2. Each Child SA will be used to negotiate the actual IPsec SAs. The initial Child SA is always negotiated with the initial IKEv2 key exchange; additional Child SAs may be negotiated with additional Child SA key exchanges for an established IKE SA.

Possible values for auth, enc, group, and the default proposals are described below in CRYPTO TRANSFORMS. If omitted, iked(8) will use the default proposals for the ESP or AH protocol. The group option will only be used to enable Perfect Forward Secrecy (PFS) for additional Child SAs exchanges that are not part of the initial key exchange.

srcid string dstid string

srcid defines an ID of type “FQDN”, “ASN1_DN”, “IPV4”, “IPV6”, or “UFQDN” that will be used by iked(8) as the identity of the local peer. If the argument is an email address (reyk@example.com), iked(8) will use UFQDN as the ID type. The ASN1_DN type will be used if the string starts with a slash ‘/’ (/C=DE/../CN=10.0.0.1/emailAddress=reyk@example.com). If the argument is an IPv4 address or a compressed IPv6 address, the ID types IPV4 or IPV6 will be used. Anything else is considered to be an FQDN.

If srcid is omitted, the default is to use the hostname of the local machine, see hostname(1) to set or print the hostname.

dstid is similar to srcid, but instead specifies the ID to be used by the remote peer.

ikelifetime time

The optional ikelifetime parameter defines the IKE SA expiration timeout by the time SA was created. A zero value disables active IKE SA rekeying. This is the default.

The accepted format of the time specification is described below.

lifetime time [bytes bytes]

The optional lifetime parameter defines the Child SA expiration timeout by the time SA was in use and by the number of bytes that were processed using the SA. Default values are 3 hours and 512 megabytes which means that SA will be rekeyed before reaching the time limit or 512 megabytes of data will pass through. Zero values disable rekeying.

Several unit specifiers are recognized (ignoring case): ‘m’ and ‘h’ for minutes and hours, and ‘K’, ‘M’ and ‘G’ for kilo-, mega- and gigabytes accordingly.

Please note that rekeying must happen at least several times a day as IPsec security heavily depends on frequent key renewals.

[ikeauth]

Specify a method to be used to authenticate the remote peer. iked(8) will automatically determine a method based on public keys or certificates configured for the peer. ikeauth can be used to override this behaviour. Non-psk modes will require setting up certificates and RSA or ECDSA public keys; see iked(8) for more information.

eap type: Use EAP to authenticate the initiator. The only supported EAP type is currently MSCHAP-V2. The responder will use RSA public key authentication.
ecdsa256: Use ECDSA with a 256-bit elliptic curve key and SHA2-256 for authentication.
ecdsa384: Use ECDSA with a 384-bit elliptic curve key and SHA2-384 for authentication.
ecdsa521: Use ECDSA with a 521-bit elliptic curve key and SHA2-512 for authentication.
psk string: Use a pre-shared key string or hex value (starting with 0x) for authentication.
rfc7427: Only use RFC 7427 signatures for authentication. RFC 7427 signatures currently only support SHA2-256 as the hash.
rsa: Use RSA public key authentication with SHA1 as the hash.

The default is to allow any signature authentication.

config option address

Send one or more optional configuration payloads (CP) to the peer. The configuration option can be one of the following with the expected address format:

address address: Assign a static address on the internal network.
address address/prefix: Assign a dynamic address on the internal network. The address will be assigned from an address pool with the size specified by prefix.
netmask netmask: The IPv4 netmask of the internal network.
name-server address: The DNS server address within the internal network.
netbios-server address: The NetBIOS name server (WINS) within the internal network. This option is provided for compatibility with legacy clients.
dhcp-server address: The address of an internal DHCP server for further configuration.
protected-subnet address/prefix: The address of the protected subnet within the internal network.
access-server address: The address of an internal remote access server.

tag string

Add a pf(4) tag to all packets of IPsec SAs created for this connection. This will allow matching packets for this connection by defining rules in pf.conf(5) using the tagged keyword.

The following variables can be used in tags to include information from the remote peer on runtime:

$id: The dstid that was proposed by the remote peer to identify itself. It will be expanded to id-value, e.g. FQDN/foo.example.com. To limit the size of the derived tag, iked(8) will extract the common name ‘CN=’ from ASN1_DN IDs, for example ASN1_ID//C=DE/../CN=10.1.1.1/.. will be expanded to 10.1.1.1.
$eapid: For a connection using EAP, the identity (username) used by the remote peer.
$domain: Extract the domain from IDs of type FQDN, UFQDN or ASN1_DN.
$name: The name of the IKEv2 policy that was configured in iked.conf or automatically generated by iked(8).

For example, if the ID is FQDN/foo.example.com or UFQDN/user@example.com, “ipsec-$domain” expands to “ipsec-example.com”. The variable expansion for the tag directive occurs only at runtime, not during configuration file parse time.

tap interface

Send the decapsulated IPsec traffic to the specified enc(4) interface instead of enc0 for filtering and monitoring. The traffic will be blocked if the specified interface does not exist.

PACKET FILTERING

IPsec traffic appears unencrypted on the enc(4) interface and can be filtered accordingly using the OpenBSD packet filter, pf(4). The grammar for the packet filter is described in pf.conf(5).

The following components are relevant to filtering IPsec traffic:

external interface: Interface for IKE traffic and encapsulated IPsec traffic.
proto udp port 500: IKE traffic on the external interface.
proto udp port 4500: IKE NAT-Traversal traffic on the external interface.
proto ah | esp: Encapsulated IPsec traffic on the external interface.
enc0: Default interface for outgoing traffic before it's been encapsulated, and incoming traffic after it's been decapsulated. State on this interface should be interface bound; see enc(4) for further information.
proto ipencap: [tunnel mode only] IP-in-IP traffic flowing between gateways on the enc0 interface.
tagged ipsec-example.org: Match traffic of IPsec SAs using the tag keyword.

If the filtering rules specify to block everything by default, the following rule would ensure that IPsec traffic never hits the packet filtering engine, and is therefore passed:

set skip on enc0

In the following example, all traffic is blocked by default. IPsec-related traffic from gateways {192.168.3.1, 192.168.3.2} and networks {10.0.1.0/24, 10.0.2.0/24} is permitted.

block on ix0
block on enc0

pass  in on ix0 proto udp from 192.168.3.2 to 192.168.3.1 \
	port {500, 4500}
pass out on ix0 proto udp from 192.168.3.1 to 192.168.3.2 \
	port {500, 4500}

pass  in on ix0 proto esp from 192.168.3.2 to 192.168.3.1
pass out on ix0 proto esp from 192.168.3.1 to 192.168.3.2

pass  in on enc0 proto ipencap from 192.168.3.2 to 192.168.3.1 \
	keep state (if-bound)
pass out on enc0 proto ipencap from 192.168.3.1 to 192.168.3.2 \
	keep state (if-bound)
pass  in on enc0 from 10.0.2.0/24 to 10.0.1.0/24 \
	keep state (if-bound)
pass out on enc0 from 10.0.1.0/24 to 10.0.2.0/24 \
	keep state (if-bound)

pf(4) has the ability to filter IPsec-related packets based on an arbitrary tag specified within a ruleset. The tag is used as an internal marker which can be used to identify the packets later on. This could be helpful, for example, in scenarios where users are connecting in from differing IP addresses, or to support queue-based bandwidth control, since the enc0 interface does not support it.

The following pf.conf(5) fragment uses queues for all IPsec traffic with special handling for developers and employees:

queue std on ix0 bandwidth 100M
queue   deflt parent std bandwidth 10M default
queue   developers parent std bandwidth 75M
queue   employees parent std bandwidth 5M
queue   ipsec parent std bandwidth 10M

pass out on ix0 proto esp set queue ipsec

pass out on ix0 tagged ipsec-developers.example.com \
	set queue developers
pass out on ix0 tagged ipsec-employees.example.com \
	set queue employees

The following example assigns the tags in the iked.conf configuration and also sets an alternative enc(4) device:

ikev2 esp from 10.1.1.0/24 to 10.1.2.0/24 peer 192.168.3.2 \
	tag ipsec-$domain tap "enc1"

OUTGOING NETWORK ADDRESS TRANSLATION

In some network topologies it is desirable to perform NAT on traffic leaving through the VPN tunnel. In order to achieve that, the src argument is used to negotiate the desired network ID with the peer and the srcnat parameter defines the true local subnet, so that a correct SA can be installed on the local side.

For example, if the local subnet is 192.168.1.0/24 and all the traffic for a specific VPN peer should appear as coming from 10.10.10.1, the following configuration is used:

ikev2 esp from 10.10.10.1 (192.168.1.0/24) to 192.168.2.0/24 \
	peer 10.10.20.1

Naturally, a relevant NAT rule is required in pf.conf(5). For the example above, this would be:

match out on enc0 from 192.168.1.0/24 to 192.168.2.0/24 \
	nat-to 10.10.10.1

From the peer's point of view, the local end of the VPN tunnel is declared to be 10.10.10.1 and all the traffic arrives with that source address.

CRYPTO TRANSFORMS

The following authentication types are permitted with the auth keyword:

Authentication	Key Length	Truncated Length
`hmac-md5`	128 bits	96 bits
`hmac-sha1`	160 bits	96 bits
`hmac-sha2-256`	256 bits	128 bits
`hmac-sha2-384`	384 bits	192 bits
`hmac-sha2-512`	512 bits	256 bits

The following pseudo-random function types are permitted with the prf keyword:

PRF	Key Length
`hmac-md5`	128 bits	[IKE only]
`hmac-sha1`	160 bits	[IKE only]
`hmac-sha2-256`	256 bits	[IKE only]
`hmac-sha2-384`	384 bits	[IKE only]
`hmac-sha2-512`	512 bits	[IKE only]

The following cipher types are permitted with the enc keyword:

Cipher	Key Length
`3des`	168 bits
`aes-128`	128 bits
`aes-192`	192 bits
`aes-256`	256 bits
`aes-128-ctr`	160 bits	[ESP only]
`aes-192-ctr`	224 bits	[ESP only]
`aes-256-ctr`	288 bits	[ESP only]
`aes-128-gcm`	160 bits	[ESP only]
`aes-192-gcm`	224 bits	[ESP only]
`aes-256-gcm`	288 bits	[ESP only]
`blowfish`	160 bits	[ESP only]
`cast`	128 bits	[ESP only]
`chacha20-poly1305`	288 bits	[ESP only]

The following cipher types provide only authentication, not encryption:

`aes-128-gmac`	160 bits	[ESP only]
`aes-192-gmac`	224 bits	[ESP only]
`aes-256-gmac`	288 bits	[ESP only]
`null`		[ESP only]

3DES requires 24 bytes to form its 168-bit key. This is because the most significant bit of each byte is used for parity.

The keysize of AES-CTR is actually 128-bit. However as well as the key, a 32-bit nonce has to be supplied. Thus 160 bits of key material have to be supplied. The same applies to AES-GCM, AES-GMAC and Chacha20-Poly1305, however in the latter case the keysize is 256 bit.

Using AES-GMAC or NULL with ESP will only provide authentication. This is useful in setups where AH cannot be used, e.g. when NAT is involved.

The following group types are permitted with the group keyword:

Name	Group	Size	Type
`modp768`	grp1	768	MODP
`modp1024`	grp2	1024	MODP
`ec2n155`	grp3	155	EC2N [insecure]
`ec2n185`	grp4	185	EC2N [insecure]
`modp1536`	grp5	1536	MODP
`modp2048`	grp14	2048	MODP
`modp3072`	grp15	3072	MODP
`modp4096`	grp16	4096	MODP
`modp6144`	grp17	6144	MODP
`modp8192`	grp18	8192	MODP
`ecp256`	grp19	256	ECP
`ecp384`	grp20	384	ECP
`ecp521`	grp21	521	ECP
`ecp192`	grp25	192	ECP
`ecp224`	grp26	224	ECP
`brainpool224`	grp27	224	ECP, brainpoolP224r1
`brainpool256`	grp28	256	ECP, brainpoolP256r1
`brainpool384`	grp29	384	ECP, brainpoolP384r1
`brainpool512`	grp30	512	ECP, brainpoolP512r1
`curve25519`	-	256	Curve25519

The currently supported group types are either MODP (exponentiation groups modulo a prime), EC2N (elliptic curve groups over GF[2^N]), ECP (elliptic curve groups modulo a prime), or the non-standard Curve25519. Please note that the EC2N groups are considered as insecure and only provided for backwards compatibility.

EXAMPLES

The first example is intended for a server with clients connecting to iked(8) as an IPsec gateway, or IKEv2 responder, using mutual public key authentication and additional challenge-based EAP-MSCHAPv2 password authentication:

user "test" "password123"

ikev2 "win7" esp \
	from 0.0.0.0/0 to 172.16.2.0/24 \
	peer 10.0.0.0/8 local 192.168.56.0/24 \
	eap "mschap-v2" \
	config address 172.16.2.1 \
	tag "$name-$id"

The next example allows peers to authenticate using a pre-shared key ‘foobar’:

ikev2 "big test" \
	esp proto tcp \
	from 10.0.0.0/8 port 23 to 20.0.0.0/8 port 40 \
	from 192.168.1.1 to 192.168.2.2 \
	peer any local any \
	ikesa enc 3des auth hmac-sha1 group modp1024 \
	childsa enc aes-128 auth hmac-sha1 \
	srcid host.example.com \
	dstid 192.168.0.254 \
	psk "foobar"

The following example illustrates the last matching policy evaluation for incoming connections on an IKEv2 gateway. The peer 192.168.1.34 will always match the first policy because of the quick keyword; connections from the peers 192.168.1.3 and 192.168.1.2 will be matched by one of the last two policies; any other connections from 192.168.1.0/24 will be matched by the ‘subnet’ policy; and any other connection will be matched by the ‘catch all’ policy.

ikev2 quick esp from 10.10.10.0/24 to 10.20.20.0/24 \
	peer 192.168.1.34
ikev2 "catch all" esp from 10.0.1.0/24 to 10.0.2.0/24 \
	peer any
ikev2 "subnet" esp from 10.0.3.0/24 to 10.0.4.0/24 \
	peer 192.168.1.0/24
ikev2 esp from 10.0.5.0/30 to 10.0.5.4/30 peer 192.168.1.2
ikev2 esp from 10.0.5.8/30 to 10.0.5.12/30 peer 192.168.1.3

HISTORY

The iked.conf file format first appeared in OpenBSD 4.8.

AUTHORS

The iked(8) program was written by Reyk Floeter <reyk@openbsd.org>.

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