IPSEC.CONF(5)

NAME
ipsec.conf - IPsec configuration and connections

DESCRIPTION
The optional ipsec.conf file specifies most configuration and control information for the strongSwan IPsec subsystem. (The major exception is secrets for authentication; see ipsec.secrets(5).) Its contents are not security-sensitive.

The file is a text file, consisting of one or more sections. White space followed by # followed by anything to the end of the line is a comment and is ignored, as are empty lines which are not within a section.

A line which contains include and a file name, separated by white space, is replaced by the contents of that file, preceded and followed by empty lines. If the file name is not a full pathname, it is considered to be relative to the directory containing the including file. Such inclusions can be nested. Only a single filename may be supplied, and it may not contain white space, but it may include shell wildcards (see sh(1)); for example:

include ipsec.*.conf

The intention of the include facility is mostly to permit keeping information on connections, or sets of connections, separate from the main configuration file. This permits such connection descriptions to be changed, copied to the other security gateways involved, etc., without having to constantly extract them from the configuration file and then insert them back into it. Note also the also parameter (described below) which permits splitting a single logical section (e.g. a connection description) into several actual sections.

A section begins with a line of the form:

type name

where type indicates what type of section follows, and name is an arbitrary name which distinguishes the section from others of the same type. (Names must start with a letter and may contain only letters, digits, periods, underscores, and hyphens.) All subsequent non-empty lines which begin with white space are part of the section; comments within a section must begin with white space too. There may be only one section of a given type with a given name.

Lines within the section are generally of the form

parameter=value

(note the mandatory preceding white space). There can be white space on either side of the =. Parameter names follow the same syntax as section names, and are specific to a section type. Unless otherwise explicitly specified, no parameter name may appear more than once in a section.

An empty value stands for the system default value (if any) of the parameter, i.e. it is roughly equivalent to omitting the parameter line entirely. A value may contain white space only if the entire value is enclosed in double quotes ("); a value cannot itself contain a double quote, nor may it be continued across more than one line.

Numeric values are specified to be either an ``integer'' (a sequence of digits) or a ``decimal number'' (sequence of digits optionally followed by `.' and another sequence of digits).

There is currently one parameter which is available in any type of section:

also
    the value is a section name; the parameters of that section are appended to this section, as if they had been written as part of it. The specified section must exist, must follow the current one, and must have the same section type. (Nesting is permitted, and there may be more than one also in a single section, although it is forbidden to append the same section more than once.)

A section with name %default specifies defaults for sections of the same type. For each parameter in it, any section of that type which does not have a parameter of the same name gets a copy of the one from the %default section. There may be multiple %default sections of a given type, but only one default may be supplied for any specific parameter name, and all %default sections of a given type must precede all non-%default sections of that type. %default sections may not contain the also parameter.

Currently there are three types of sections: a config section specifies general configuration information for IPsec, a conn section specifies an IPsec connection, while a ca section specifies special properties a certification authority.

CONN SECTIONS
A conn section contains a connection specification, defining a network connection to be made using IPsec. The name given is arbitrary, and is used to identify the connection. Here's a simple example:

conn snt
	left=10.11.11.1
	leftsubnet=10.0.1.0/24
	leftnexthop=172.16.55.66
	right=192.168.22.1
	rightsubnet=10.0.2.0/24
	rightnexthop=172.16.88.99
	keyingtries=%forever

A note on terminology: There are two kinds of communications going on: transmission of user IP packets, and gateway-to-gateway negotiations for keying, rekeying, and general control. The path to control the connection is called 'ISAKMP SA' in IKEv1 and level data path, is called 'IPsec SA'. strongSwan currently uses two separate keying daemons. Pluto handles all IKEv1 connections, Charon is the new daemon supporting the IKEv2 protocol. Charon does not support all keywords yet.

To avoid trivial editing of the configuration file to suit it to each system involved in a connection, connection specifications are written in terms of left and right participants, rather than in terms of local and remote. Which participant is considered left or right is arbitrary; IPsec figures out which one it is being run on based on internal information. This permits using identical connection specifications on both ends. There are cases where there is no symmetry; a good convention is to use left for the local side and right for the remote side (the first letters are a good mnemonic).

Many of the parameters relate to one participant or the other; only the ones for left are listed here, but every parameter whose name begins with left has a right counterpart, whose description is the same but with left and right reversed.

Parameters are optional unless marked '(required)'.

  CONN PARAMETERS
Unless otherwise noted, for a connection to work, in general it is necessary for the two ends to agree exactly on the values of these parameters.

type
    the type of the connection; currently the accepted values are tunnel (the default) signifying a host-to-host, host-to-subnet, or subnet-to-subnet tunnel; transport, signifying host-to-host transport mode; passthrough, signifying that no IPsec processing should be done at all; drop, signifying that packets should be discarded; and reject, signifying that packets should be discarded and a diagnostic ICMP returned. Charon currently supports only tunnel and transport connection types.

left
    (required) the IP address of the left participant's public-network interface, in any form accepted by ipsec_ttoaddr(3) or one of several magic values. If it is %defaultroute, and the config setup section's, interfaces specification contains %defaultroute, left will be filled in automatically with the local address of the default-route interface (as determined at IPsec startup time); this also overrides any value supplied for leftnexthop. (Either left or right may be %defaultroute, but not both.) The value %any signifies an address to be filled in (by automatic keying) during negotiation.

leftsubnet
    private subnet behind the left participant, expressed as network/netmask (actually, any form acceptable to ipsec_ttosubnet(3)); if omitted, essentially assumed to be left/32, signifying that the left end of the connection goes to the left participant only. When using IKEv2, the configured subnet of the peers may differ, the protocol narrows it to the greates common subnet.

leftnexthop
    next-hop gateway IP address for the left participant's connection to the public network; defaults to %direct (meaning right). If the value is to be overridden by the left=%defaultroute method (see above), an explicit value must not be given. If that method is not being used, but leftnexthop is %defaultroute, and interfaces=%defaultroute is used in the config setup section, the next-hop gateway address of the default-route interface will be used. The magic value %direct signifies a value to be filled in (by automatic keying) with the peer's address. Relevant only locally, other end need not agree on it. Currently not supported in IKEv2.

leftupdown
    what ``updown'' script to run to adjust routing and/or firewalling when the status of the connection changes (default ipsec _updown). May include positional parameters separated by white space (although this requires enclosing the whole string in quotes); including shell metacharacters is unwise. See ipsec_pluto(8) for details. Relevant only locally, other end need not agree on it. IKEv2 uses the updown script to insert firewall rules only. Routing is not support and will be implemented directly into Charon.

leftfirewall
    whether the left participant is doing forwarding-firewalling (including masquerading) for traffic from leftsubnet, which should be turned off (for traffic to the other subnet) once the connection is established; acceptable values are yes and (the default) no. May not be used in the same connection description with leftupdown. Implemented as a parameter to the default updown script. See notes below. Relevant only locally, other end need not agree on it. If one or both security gateways are doing forwarding firewalling (possibly including masquerading), and this is specified using the firewall parameters, tunnels established with IPsec are exempted from it so that packets can flow unchanged through the tunnels. (This means that all subnets connected in this manner must have distinct, non-overlapping subnet address blocks.) This is done by the default updown script (see ipsec_pluto(8)). In situations calling for more control, it may be preferable for the user to supply his own updown script, which makes the appropriate adjustments for his system.

auto
    what operation, if any, should be done automatically at IPsec startup; currently-accepted values are add , route , start and ignore add loads a connection without starting it. route loads a connection and installs kernel traps. If traffic is detected between leftsubnet and rightsubnet , a connection is established. start loads a connection and brings it up immediatly. ignore ignores the connection. This is equal to delete a connection from the config file. Relevant only locally, other end need not agree on it (but in general, for an intended-to-be-permanent connection, both ends should use auto=start to ensure that any reboot causes immediate renegotiation).

auth
    whether authentication should be done as part of ESP encryption, or separately using the AH protocol; acceptable values are esp (the default) and ah. The IKEv2 daemon currently supports only ESP.

authby
    how the two security gateways should authenticate each other; acceptable values are secret for shared secrets, rsasig for RSA digital signatures (the default), secret|rsasig for either, and never if negotiation is never to be attempted or accepted (useful for shunt-only conns). Digital signatures are superior in every way to shared secrets. In IKEv2, the two ends must not agree on this parameter, it is relevant for the own authentication method only. IKEv2 additionally supports the value eap, which indicates an initiator to request EAP authentication. The EAP method to use is selected by the server (see eap).

compress
    whether IPComp compression of content is proposed on the connection (link-level compression does not work on encrypted data, so to be effective, compression must be done before encryption); acceptable values are yes and no (the default). A value of yes causes IPsec to propose both compressed and uncompressed, and prefer compressed. A value of no prevents IPsec from proposing compression; a proposal to compress will still be accepted. IKEv2 does not support IP compression yet.

dpdaction
    controls the use of the Dead Peer Detection protocol (DPD, RFC 3706) where R_U_THERE notification messages (IKEv1) or empty INFORMATIONAL messages (IKEv2) are periodically sent in order to check the liveliness of the IPsec peer. The values clear and hold both activate DPD. If no activity is detected, all connections with a dead peer are stopped and unrouted ( clear ) or put in the hold state ( hold ). For IKEv1 , the default is none which disables the active sending of R_U_THERE notifications. Nevertheless pluto will always send the DPD Vendor ID during connection set up in order to signal the readiness to act passively as a responder if the peer wants to use DPD. For IKEv2, none does't make sense, as all messages are used to detect dead peers. If specified, it has the same meaning as the default ( clear ).

dpddelay
    defines the period time interval with which R_U_THERE messages/INFORMATIONAL exchanges are sent to the peer. These are only sent if no other traffic is received. In IKEv2, a value of 0 sends no additional INFORMATIONAL messages and uses only standard messages (such as those to rekey) to detect dead peers.

dpdtimeout
    defines the timeout interval, after which all connections to a peer are deleted in case of inactivity. This only applies to IKEv1, in IKEv2 the default retransmission timeout applies, as every exchange is used to detect dead peers.

failureshunt
    what to do with packets when negotiation fails. The default is none: no shunt; passthrough, drop, and reject have the obvious meanings. Has no effect in IKEv2 yet.

ikelifetime
    how long the keying channel of a connection ('ISAKMP/IKE SA') should last before being renegotiated.

keyexchange
    method of key exchange; which protocol should be used to initialize the connection. Connections marked with ikev1 are initiated with pluto, those marked with ikev2 with charon. An incoming request from the remote peer is handled by the correct daemon, unaffected from the keyexchange setting. The default value ike currently behaves exactly as ikev1.

keyingtries
    how many attempts (a whole number or %forever) should be made to negotiate a connection, or a replacement for one, before giving up (default %forever). The value %forever means 'never give up'. Relevant only locally, other end need not agree on it.

keylife
    how long a particular instance of a connection (a set of encryption/authentication keys for user packets) should last, from successful negotiation to expiry; acceptable values are an integer optionally followed by s (a time in seconds) or a decimal number followed by m, h, or d (a time in minutes, hours, or days respectively) (default 1h, maximum 24h). Normally, the connection is renegotiated (via the keying channel) before it expires. The two ends need not exactly agree on keylife, although if they do not, there will be some clutter of superseded connections on the end which thinks the lifetime is longer.

leftca
    the distinguished name of a certificate authority which is required to lie in the trust path going from the left participant's certificate up to the root certification authority.

leftcert
    the path to the left participant's X.509 certificate. The file can be coded either in PEM or DER format. OpenPGP certificates are supported as well. Both absolute paths or paths relative to /etc/ipsec.d/certs are accepted. By default leftcert sets leftid to the distinguished name of the certificate's subject and leftca to the distinguished name of the certificate's issuer. The left participant's ID can be overriden by specifying a leftid value which must be certified by the certificate, though.

leftgroups
    a comma separated list of group names. If the leftgroups parameter is present then the peer must be a member of at least one of the groups defined by the parameter. Group membership must be certified by a valid attribute certificate stored in /etc/ipsec.d/acerts thas has been issued to the peer by a trusted Authorization Authority stored in /etc/ipsec.d/aacerts. Attribute certificates are not supported in IKEv2 yet.

leftid
    how the left participant should be identified for authentication; defaults to left. Can be an IP address (in any ipsec_ttoaddr(3) syntax) or a fully-qualified domain name preceded by @ (which is used as a literal string and not resolved). The magic value %myid stands for the current setting of myid. This is set in config setup or by ipsec_whack(8)), or, if not set, it is the IP address in %defaultroute (if that is supported by a TXT record in its reverse domain), or otherwise it is the system's hostname (if that is supported by a TXT record in its forward domain), or otherwise it is undefined.

leftsourceip
    The internal source IP to use in a tunnel, also known as virtual IP. If the value is %modeconfig or %config, an address is requested from the peer.

leftsubnetwithin
    Not relevant for IKEv2, as subnets are narrowed.

pfs whether Perfect Forward Secrecy of keys is desired on the connection's keying channel (with PFS, penetration of the key-exchange protocol does not compromise keys negotiated earlier); acceptable values are yes (the default) and no currently not supported.

rekey
    whether a connection should be renegotiated when it is about to expire; acceptable values are yes (the default) and no. The two ends need not agree, but while a value of no prevents Pluto/Charon from requesting renegotiation, it does not prevent responding to renegotiation requested from the other end, so no will be largely ineffective unless both ends agree on it.

reauth
    whether rekeying of an IKE_SA should also reauthenticate the peer. In IKEv1, reauthentication is always done. In IKEv2, a value of no rekeys without uninstalling the IPsec SAs, a value of yes (the default) creates a new IKE_SA from scratch and tries to recreate all IPsec SAs.

rekeyfuzz
    maximum percentage by which rekeymargin should be randomly increased to randomize rekeying intervals (important for hosts with many connections); acceptable values are an integer, which may exceed 100, followed by a `%' (default set by ipsec_pluto(8), currently 100%). The value of rekeymargin, after this random increase, must not exceed keylife. The value 0% will suppress time randomization. Relevant only locally, other end need not agree on it.

rekeymargin
    how long before connection expiry or keying-channel expiry should attempts to negotiate a replacement begin; acceptable values as for keylife (default 9m). Relevant only locally, other end need not agree on it.

ike IKE/ISAKMP SA encryption/authentication algorithm to be used, e.g. aes128-sha1-modp2048 (encryption-integrity-dhgroup).

esp ESP encryption/authentication algorithm to be used for the connection, e.g. 3des-md5 (encryption-integrity).

ah  AH authentication algorithm to be used for the connection, e.g. hmac-md5.

CA SECTIONS
This are optional sections that can be used to assign special parameters to a Certification Authority (CA). These parameters are not supported in IKEv2 yet.

auto
    currently can have either the value ignore or add

cacert
    defines a path to the CA certificate either relative to /etc/ipsec.d/cacerts or as an absolute path.

crluri
    defines a CRL distribution point (ldap, http, or file URI)

crluri2
    defines an alternative CRL distribution point (ldap, http, or file URI)

ldaphost
    defines an ldap host.

ocspuri
    defines an OCSP URI.

CONFIG SECTIONS
At present, the only config section known to the IPsec software is the one named setup, which contains information used when the software is being started (see ipsec_setup(8)). Here's an example:

config setup
	interfaces="ipsec0=eth1 ipsec1=ppp0"
	klipsdebug=none
	plutodebug=all
	manualstart=

Parameters are optional unless marked ``(required)''. The currently-accepted parameter names in a config setup section are:

myid
    the identity to be used for %myid. %myid is used in the implicit policy group conns and can be used as an identity in explicit conns. If unspecified, %myid is set to the IP address in %defaultroute (if that is supported by a TXT record in its reverse domain), or otherwise the system's hostname (if that is supported by a TXT record in its forward domain), or otherwise it is undefined. An explicit value generally starts with ``@''.

interfaces
    virtual and physical interfaces for IPsec to use: a single virtual=physical pair, a (quoted!) list of pairs separated by white space, or %none. One of the pairs may be written as %defaultroute, which means: find the interface d that the default route points to, and then act as if the value was ``ipsec0=d''. %defaultroute is the default; %none must be used to denote no interfaces. If %defaultroute is used (implicitly or explicitly) information about the default route and its interface is noted for use by ipsec_manual(8) and ipsec_auto(8).)

forwardcontrol
    whether setup should turn IP forwarding on (if it's not already on) as IPsec is started, and turn it off again (if it was off) as IPsec is stopped; acceptable values are yes and (the default) no. For this to have full effect, forwarding must be disabled before the hardware interfaces are brought up (e.g., net.ipv4.ip_forward = 0 in Red Hat 6.x /etc/sysctl.conf), because IPsec doesn't get control early enough to do that.

rp_filter
    whether and how setup should adjust the reverse path filtering mechanism for the physical devices to be used. Values are %unchanged (to leave it alone) or 0, 1, 2 (values to set it to). /proc/sys/net/ipv4/conf/PHYS/rp_filter is badly documented; it must be 0 in many cases for ipsec to function. The default value for the parameter is 0.

syslog
    the syslog(2) ``facility'' name and priority to use for startup/shutdown log messages, default daemon.error.

plutodebug
    how much Pluto debugging output should be logged. An empty value, or the magic value none, means no debugging output (the default). The magic value all means full output. Otherwise only the specified types of output (a quoted list, names without the --debug- prefix, separated by white space) are enabled; for details on available debugging types, see ipsec_pluto(8).

charondebug
    how much Charon debugging output should be logged. A comma separated list containing type level/pairs may be specified, e.g: dmn 3, ike 1, net -1. Acceptable values for types are dmn, mgr, ike, chd, job, cfg, knl, net, enc, lib and the level is one of -1, 0, 1, 2, 3, 4 (for silent, audit, control, controlmore, raw, private)

plutoopts
    additional options to pass to pluto upon startup. See ipsec_pluto(8).

plutostderrlog
    do not use syslog, but rather log to stderr, and direct stderr to the argument file.

dumpdir
    in what directory should things started by setup (notably the Pluto daemon) be allowed to dump core? The empty value (the default) means they are not allowed to.

pluto
    whether to start Pluto or not; Values are yes (the default) or no (useful only in special circumstances).

plutowait
    should Pluto wait for each negotiation attempt that is part of startup to finish before proceeding with the next? Values are yes or no (the default).

prepluto
    shell command to run before starting Pluto (e.g., to decrypt an encrypted copy of the ipsec.secrets file). It's run in a very simple way; complexities like I/O redirection are best hidden within a script. Any output is redirected for logging, so running interactive commands is difficult unless they use /dev/tty or equivalent for their interaction. Default is none.

postpluto
    shell command to run after starting Pluto (e.g., to remove a decrypted copy of the ipsec.secrets file). It's run in a very simple way; complexities like I/O redirection are best hidden within a script. Any output is redirected for logging, so running interactive commands is difficult unless they use /dev/tty or equivalent for their interaction. Default is none.

fragicmp
    whether a tunnel's need to fragment a packet should be reported back with an ICMP message, in an attempt to make the sender lower his PMTU estimate; acceptable values are yes (the default) and no.

hidetos
    whether a tunnel packet's TOS field should be set to 0 rather than copied from the user packet inside; acceptable values are yes (the default) and no.

uniqueids
    whether a particular participant ID should be kept unique, with any new (automatically keyed) connection using an ID from a different IP address deemed to replace all old ones using that ID; acceptable values are yes (the default) and no. Participant IDs normally are unique, so a new (automatically-keyed) connection using the same ID is almost invariably intended to replace an old one.

overridemtu
    value that the MTU of the ipsecn interface(s) should be set to, overriding IPsec's (large) default. This parameter is needed only in special situations.

nat_traversal

crlcheckinterval

strictcrlpolicy

pkcs11module

pkcs11keepstate

CHOOSING A CONNECTION

When choosing a connection to apply to an outbound packet caught with a %trap, the system prefers the one with the most specific eroute that includes the packet's source and destination IP addresses. Source subnets are examined before destination subnets. For initiating, only routed connections are considered. For responding, unrouted but added connections are considered.

When choosing a connection to use to respond to a negotiation which doesn't match an ordinary conn, an opportunistic connection may be instantiated. Eventually, its instance will be /32 -> /32, but for earlier stages of the negotiation, there will not be enough information about the client subnets to complete the instantiation.

FILES
/etc/ipsec.conf
/etc/ipsec.d/cacerts
/etc/ipsec.d/certs
/etc/ipsec.d/crls
/etc/ipsec.d/aacerts
/etc/ipsec.d/acerts

SEE ALSO
ipsec(8), ipsec_ttoaddr(8), ipsec_auto(8), ipsec_manual(8), ipsec_rsasigkey(8)

HISTORY
Written for the FreeS/WAN project <http://www.freeswan.org> by Henry Spencer. Extended for the strongSwan project <http://www.strongswan.org> by Andreas Steffen. Updated to respect IKEv2 specific configuration by Martin Willi.

BUGS

When type or failureshunt is set to drop or reject, strongSwan blocks outbound packets using eroutes, but assumes inbound blocking is handled by the firewall. strongSwan offers firewall hooks via an ``updown'' script. However, the default ipsec _updown provides no help in controlling a modern firewall.

Including attributes of the keying channel (authentication methods, ikelifetime, etc.) as an attribute of a connection, rather than of a participant pair, is dubious and incurs limitations.

Ipsec_manual is not nearly as generous about the syntax of subnets, addresses, etc. as the usual strongSwan user interfaces. Four-component dotted-decimal must be used for all addresses. It is smart enough to translate bit-count netmasks to dotted-decimal form.

It would be good to have a line-continuation syntax, especially for the very long lines involved in RSA signature keys.

The ability to specify different identities, authby, and public keys for different automatic-keyed connections between the same participants is misleading; this doesn't work dependably because the identity of the participants is not known early enough. This is especially awkward for the ``Road Warrior'' case, where the remote IP address is specified as 0.0.0.0, and that is considered to be the ``participant'' for such connections.

In principle it might be necessary to control MTU on an interface-by-interface basis, rather than with the single global override that overridemtu provides.

A number of features which could be implemented in both manual and automatic keying actually are not yet implemented for manual keying. This is unlikely to be fixed any time soon.

If conns are to be added before DNS is available, left=FQDN, leftnextop=FQDN, and leftrsasigkey=%dnsonload will fail. ipsec_pluto(8) does not actually use the public key for our side of a conn but it isn't generally known at a add-time which side is ours (Road Warrior and Opportunistic conns are currently exceptions).

The myid option does not affect explicit ipsec auto --add or ipsec auto --replace commands for implicit conns.