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 of 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=192.168.0.1
	leftsubnet=10.1.0.0/16
	right=192.168.0.2
	rightsubnet=10.1.0.0/16
	keyingtries=%forever
	auto=add

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.

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

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 or psk 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 outbound authentication method only. IKEv1 additionally supports the values xauthpsk and xauthrsasig that will enable eXtended AUTHentication (XAUTH) in addition to IKEv1 main mode based on shared secrets or digital RSA signatures, respectively. 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).

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).

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, hold, and restart all activate DPD. If no activity is detected, all connections with a dead peer are stopped and unrouted ( clear ), put in the hold state ( hold ) or restarted ( restart ). 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, since 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.

eap defines the EAP type to be used if authby=eap is selected. Acceptable values are aka for EAP-AKA and sim for EAP-SIM.

esp ESP encryption/authentication algorithm to be used for the connection, e.g. 3des-md5 (encryption-integrity-[dh-group]). If dh-group is specified, CHILD_SA setup and rekeying include a separate diffe hellman exchange (IKEv2 only).

ike IKE/ISAKMP SA encryption/authentication algorithm to be used, e.g. aes128-sha1-modp2048 (encryption-integrity-dhgroup). In IKEv2, multiple algorithms and proposals may be included, such as aes128-aes256-sha1-modp1536-modp2048,3des-sha1-md5-modp1024.

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.

left
    (required) the IP address of the left participant's public-network interface, in any form accepted by ttoaddr(3) or one of several magic values. If it is %defaultroute, left will be filled in automatically with the local address of the default-route interface (as determined at IPsec startup time). (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. The prefix % in front of a fully-qualified domain name or an IP address will implicitly set leftallowany=yes. If the domain name cannot be resolved into an IP address at IPsec startup or update time then left=%any and leftallowany=no will be assumed.

leftallowany
    a modifier for left , making it behave as %any although a concrete IP address has been assigned. Recommended for dynamic IP addresses that can be resolved by DynDNS at IPsec startup or update time. Acceptable values are yes and no (the default).

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.

leftfirewall
    whether the left participant is doing forwarding-firewalling (including masquerading) using iptables 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 no (the default). May not be used in the same connection description with leftupdown. Implemented as a parameter to the default ipsec _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 ipsec _updown script (see 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.

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.

lefthostaccess
    inserts a pair of INPUT and OUTPUT iptables rules using the default ipsec _updown script, thus allowing access to the host itself in the case where the host's internal interface is part of the negotiated client subnet. Acceptable values are yes and no (the default).

leftid
    how the left participant should be identified for authentication; defaults to left. Can be an IP address (in any ttoaddr(3) syntax) or a fully-qualified domain name preceded by @ (which is used as a literal string and not resolved).

leftnexthop
    this parameter is not needed any more because the NETKEY IPsec stack does not require explicit routing entries for the traffic to be tunneled.

leftprotoport
    restrict the traffic selector to a single protocol and/or port. Examples: leftprotoport=tcp/http or leftprotoport=6/80 or leftprotoport=udp

leftrsasigkey
    the left participant's public key for RSA signature authentication, in RFC 2537 format using ttodata(3) encoding. The magic value %none means the same as not specifying a value (useful to override a default). The value %cert (the default) means that the key is extracted from a certificate. The identity used for the left participant must be a specific host, not %any or another magic value. Caution: if two connection descriptions specify different public keys for the same leftid, confusion and madness will ensue.

leftsendcert
    Accepted values are never or no, always or yes, and ifasked.

leftsourceip
    The internal source IP to use in a tunnel, also known as virtual IP. If the value is %modeconfig, %modecfg, %config, or %cfg, an address is requested from the peer. In IKEv2, a defined address is requested, but the server may change it. If the server does not support it, the address is enforced.

rightsourceip
    The internal source IP to use in a tunnel for the remote peer. If the value is %config on the responder side, the initiator must propose a address which is then echoed back.

leftsubnet
    private subnet behind the left participant, expressed as network/netmask (actually, any form acceptable to 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.

leftsubnetwithin
    the peer can propose any subnet or single IP address that fits within the range defined by leftsubnetwithin. Not relevant for IKEv2, as subnets are narrowed.

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 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.

modeconfig
    defines which mode is used to assign a virtual IP. Accepted values are push and pull (the default). Currently relevant for IKEv1 only since IKEv2 always uses the configuration payload in pull mode.

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. IKEv2 always uses PFS for IKE_SA rekeying whereas for CHILD_SA rekeying PFS is enforced by defining a Diffie-Hellman modp group in the esp parameter.

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.

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.

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 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.

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.

xauth
    specifies the role in the XAUTH protocol if activated by authby=xauthpsk or authby=xauthrsasig. Accepted values are server and client (the default).

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)

crluri1
    synonym for crluri.

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

ldaphost
    defines an ldap host. Currently used by IKEv1 only.

ocspuri
    defines an OCSP URI.

ocspuri1
    synonym for ocspuri.

ocspuri2
    defines an alternative OCSP URI. Currently used by IKEv2 only.

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 starter(8)). Here's an example:

config setup
	plutodebug=all
	crlcheckinterval=10m
	strictcrlpolicy=yes

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

cachecrls
    certificate revocation lists (CRLs) fetched via http or ldap will be cached in /etc/ipsec.d/crls/ under a unique file name derived from the certification authority's public key. Accepted values are yes and no (the default).

charonstart
    whether to start the IKEv2 Charon daemon or not. Accepted values are yes (the default) or no.

crlcheckinterval
    interval in seconds. CRL fetching is enabled if the value is greater than zero. Asynchronous, periodic checking for fresh CRLs is currently done by the IKEv1 Pluto daemon only.

dumpdir
    in what directory should things started by ipsec starter (notably the Pluto and Charon daemons) be allowed to dump core? The empty value (the default) means they are not allowed to. This feature is currently not yet supported by ipsec starter.

plutostart
    whether to start the IKEv1 Pluto daemon or not. Accepted values are yes (the default) or no.

strictcrlpolicy
    defines if a fresh CRL must be available in order for the peer authentication based on RSA signatures to succeed. Accepted values are yes and no (the default). IKEv2 additionally recognizes ifuri which reverts to yes if at least one CRL URI is defined and to no if no URI is known.

The following config section parameters are used by the IKEv1 Pluto daemon only:

keep_alive
    interval in seconds between NAT keep alive packets, the default being 20 seconds.

nat_traversal
    activates NAT traversal by accepting source ISAKMP ports different from udp/500 and being able of floating to udp/4500 if a NAT situation is detected. Accepted values are yes and no (the default). nocrsend no certificate request payloads will be sent. Accepted values are yes and no (the default). Used by IKEv1 only, NAT traversal always being active in IKEv2.

pkcs11initargs
    non-standard argument string for PKCS#11 C_Initialize() function; required by NSS softoken.

pkcs11module
    defines the path to a dynamically loadable PKCS #11 library.

pkcs11keepstate
    PKCS #11 login sessions will be kept during the whole lifetime of the keying daemon. Useful with pin-pad smart card readers. Accepted values are yes and no (the default).

pkcs11proxy
    Pluto will act as a PKCS #11 proxy accessible via the whack interface. Accepted values are yes and no (the default).

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 pluto(8).

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.

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.

virtual_private
    defines private networks using a wildcard notation.

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.

The following config section parameters are used by the IKEv2 Charon daemon only:

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).

The following config section parameters only make sense if the KLIPS IPsec stack is used instead of the default NETKEY stack of the Linux 2.6 kernel:

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

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.

overridemtu
    value that the MTU of the ipsecn interface(s) should be set to, overriding IPsec's (large) default.

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

SEE ALSO
ipsec(8), pluto(8), starter(8), ttoaddr(3), ttodata(3)

HISTORY
Written for the FreeS/WAN project by Henry Spencer. Extended for the strongSwan project <http://www.strongswan.org> by Andreas Steffen. IKEv2-specific features by Martin Willi.

BUGS

If conns are to be added before DNS is available, left=FQDN will fail.