strongswan/src/starter/ipsec.conf.5

.TH IPSEC.CONF 5 "27 Jun 2007"
.\" RCSID $Id: ipsec.conf.5,v 1.2 2006/01/22 15:33:46 as Exp $
.SH NAME
ipsec.conf \- IPsec configuration and connections
.SH DESCRIPTION
The optional
.I ipsec.conf
file
specifies most configuration and control information for the
strongSwan IPsec subsystem.
(The major exception is secrets for authentication;
see
.IR ipsec.secrets (5).)
Its contents are not security-sensitive.
.PP
The file is a text file, consisting of one or more
.IR sections .
White space followed by
.B #
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.
.PP
A line which contains
.B 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
.IR sh (1));
for example:
.PP
.B include
.B "ipsec.*.conf"
.PP
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
.B also
parameter (described below) which permits splitting a single logical
section (e.g. a connection description) into several actual sections.
.PP
A section
begins with a line of the form:
.PP
.I type
.I name
.PP
where
.I type
indicates what type of section follows, and
.I 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.
.PP
Lines within the section are generally of the form
.PP
\ \ \ \ \ \fIparameter\fB=\fIvalue\fR
.PP
(note the mandatory preceding white space).
There can be white space on either side of the
.BR = .
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.
.PP
An empty
.I 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
.I value
may contain white space only if the entire
.I value
is enclosed in double quotes (\fB"\fR);
a
.I value
cannot itself contain a double quote,
nor may it be continued across more than one line.
.PP
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).
.PP
There is currently one parameter which is available in any type of
section:
.TP
.B 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
.B also
in a single section,
although it is forbidden to append the same section more than once.)
.PP
A section with name
.B %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
.B %default
section.
There may be multiple
.B %default
sections of a given type,
but only one default may be supplied for any specific parameter name,
and all
.B %default
sections of a given type must precede all non-\c
.B %default
sections of that type.
.B %default
sections may not contain the
.B also
parameter.
.PP
Currently there are three types of sections:
a
.B config
section specifies general configuration information for IPsec, a
.B conn
section specifies an IPsec connection, while a
.B ca
section specifies special properties of a certification authority.
.SH "CONN SECTIONS"
A
.B conn
section contains a
.IR "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:
.PP
.ne 10
.nf
.ft B
.ta 1c
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
.ft
.fi
.PP
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
'IKE SA' in the IKEv2 protocol. That what is being negotiated, the kernel
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.
.PP
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
.I left
and
.I right
participants,
rather than in terms of local and remote.
Which participant is considered
.I left
or
.I 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
.I left
for the local side and
.I right
for the remote side (the first letters are a good mnemonic).
.PP
Many of the parameters relate to one participant or the other;
only the ones for
.I left
are listed here, but every parameter whose name begins with
.B left
has a
.B right
counterpart,
whose description is the same but with
.B left
and
.B right
reversed.
.PP
Parameters are optional unless marked '(required)'.
.SS "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.
.TP 14
.B type
the type of the connection; currently the accepted values
are
.B tunnel
(the default)
signifying a host-to-host, host-to-subnet, or subnet-to-subnet tunnel;
.BR transport ,
signifying host-to-host transport mode;
.BR passthrough ,
signifying that no IPsec processing should be done at all;
.BR drop ,
signifying that packets should be discarded; and
.BR reject ,
signifying that packets should be discarded and a diagnostic ICMP returned.
Charon currently supports only 
.BR tunnel
and
.BR transport
connection types.
.TP
.B left
(required)
the IP address of the left participant's public-network interface,
in any form accepted by
.IR ttoaddr (3)
or one of several magic values.
If it is
.BR %defaultroute ,
.B left
will be filled in automatically with the local address
of the default-route interface (as determined at IPsec startup time).
(Either
.B left
or
.B right
may be
.BR %defaultroute ,
but not both.)
The value
.B %any
signifies an address to be filled in (by automatic keying) during
negotiation. The prefix
.B  %
in front of a fully-qualified domain name or an IP address will implicitly set
.B leftallowany=yes.
If the domain name cannot be resolved into an IP address at IPsec startup or update time
then
.B left=%any
and
.B leftallowany=no
will be assumed.
.TP
.B leftallowany
a modifier for
.B left
, making it behave as
.B %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
.B yes
and
.B no
(the default).
.TP
.B leftsubnet
private subnet behind the left participant, expressed as
\fInetwork\fB/\fInetmask\fR
(actually, any form acceptable to
.IR ttosubnet (3));
if omitted, essentially assumed to be \fIleft\fB/32\fR,
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.
.TP
.B leftsubnetwithin
the peer can propose any subnet or single IP address that fits within the
range defined by
.BR leftsubnetwithin.
Not relevant for IKEv2, as subnets are narrowed.
.TP
.B leftprotoport
restrict the traffic selector to a single protocol and/or port.
Examples:
.B leftprotoport=tcp/http
or
.B leftprotoport=6/80
or
.B leftprotoport=udp
.TP
.B 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.
.TP
.B leftfirewall
whether the left participant is doing forwarding-firewalling
(including masquerading) using iptables for traffic from \fIleftsubnet\fR,
which should be turned off (for traffic to the other subnet)
once the connection is established;
acceptable values are
.B yes
and
.B no
(the default).
May not be used in the same connection description with
.BR leftupdown .
Implemented as a parameter to the default \fBipsec _updown\fR 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 \fBipsec _updown\fR script (see
.IR pluto (8)).

In situations calling for more control,
it may be preferable for the user to supply his own
.I updown
script,
which makes the appropriate adjustments for his system.
.TP
.B lefthostaccess
inserts a pair of INPUT and OUTPUT iptables rules using the default
\fBipsec _updown\fR 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
.B yes
and
.B no
(the default).
.TP
.B leftupdown
what ``updown'' script to run to adjust routing and/or firewalling
when the status of the connection
changes (default
.BR "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
.IR 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.
.TP
.B auto
what operation, if any, should be done automatically at IPsec startup;
currently-accepted values are
.B add
,
.B route
,
.B start
and
.B ignore
.
.B add
loads a connection without starting it.
.B route
loads a connection and installs kernel traps. If traffic is detected between
.B leftsubnet
and
.B rightsubnet
, a connection is established.
.B start
loads a connection and brings it up immediatly.
.B 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
.B auto=start
to ensure that any reboot causes immediate renegotiation).
.TP
.B auth
whether authentication should be done as part of
ESP encryption, or separately using the AH protocol;
acceptable values are
.B esp
(the default) and
.BR ah .
The IKEv2 daemon currently supports only ESP.
.TP
.B authby
how the two security gateways should authenticate each other;
acceptable values are
.B secret
or
.B psk
for shared secrets,
.B rsasig
for RSA digital signatures (the default),
.B secret|rsasig
for either, and
.B 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
.B xauthpsk
and
.B 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
.B eap,
which indicates an initiator to request EAP authentication. The EAP method to 
use is selected by the server (see
.B eap).
.TP
.B xauth
specifies the role in the XAUTH protocol if activated by
.B authby=xauthpsk
or
.B authby=xauthrsasig.
Accepted values are
.B server
and
.B client
(the default).
.TP
.B 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 \fIbefore\fR encryption);
acceptable values are
.B yes
and
.B no
(the default). A value of
.B yes
causes IPsec to propose both compressed and uncompressed,
and prefer compressed.
A value of
.B no
prevents IPsec from proposing compression;
a proposal to compress will still be accepted.
IKEv2 does not support IP compression yet.
.TP
.B 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
.BR clear ,
.BR hold ,
and 
.B restart
all activate DPD. If no activity is detected, all connections with a dead peer
are stopped and unrouted (
.B clear
), put in the hold state (
.B hold
) or restarted (
.B restart
).
For IKEv1, the default is
.B 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,
.B none
does't make sense, since all messages are used to detect dead peers. If specified,
it has the same meaning as the default (
.B clear
).
.TP
.B 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.
.TP
.B 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.
.TP
.B ikelifetime
how long the keying channel of a connection ('ISAKMP/IKE SA')
should last before being renegotiated.
.TP
.B keyexchange
method of key exchange;
which protocol should be used to initialize the connection. Connections marked with
.B ikev1
are initiated with pluto, those marked with
.B ikev2
with charon. An incoming request from the remote peer is handled by the correct 
daemon, unaffected from the 
.B keyexchange
setting. The default value
.B ike
currently behaves exactly as
.B ikev1.
.TP
.B keyingtries
how many attempts (a whole number or \fB%forever\fP) should be made to
negotiate a connection, or a replacement for one, before giving up
(default
.BR %forever ).
The value \fB%forever\fP
means 'never give up'.
Relevant only locally, other end need not agree on it.
.TP
.B 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
.BR s
(a time in seconds)
or a decimal number followed by
.BR m ,
.BR h ,
or
.B d
(a time
in minutes, hours, or days respectively)
(default
.BR 1h ,
maximum
.BR 24h ).
Normally, the connection is renegotiated (via the keying channel)
before it expires.
The two ends need not exactly agree on
.BR keylife ,
although if they do not,
there will be some clutter of superseded connections on the end
which thinks the lifetime is longer.
.TP
.B 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. 
.TP
.B 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 \fI/etc/ipsec.d/certs\fP
are accepted. By default
.B leftcert
sets 
.B leftid
to the distinguished name of the certificate's subject and
.B leftca
to the distinguished name of the certificate's issuer.
The left participant's ID can be overriden by specifying a
.B leftid
value which must be certified by the certificate, though.
.TP
.B leftsendcert
Accepted values are
.B never
or
.BR no ,
.B always
or
.BR yes ,
and
.BR ifasked .
.TP
.B leftrsasigkey
the left participant's
public key for RSA signature authentication,
in RFC 2537 format using
.IR ttodata (3)
encoding.
The magic value
.B %none
means the same as not specifying a value (useful to override a default).
The value
.B %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
.B %any
or another magic value.
.B Caution:
if two connection descriptions
specify different public keys for the same
.BR leftid ,
confusion and madness will ensue.
.TP
.B leftgroups
a comma separated list of group names. If the
.B 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 \fI/etc/ipsec.d/acerts\fP thas has been
issued to the peer by a trusted Authorization Authority stored in
\fI/etc/ipsec.d/aacerts\fP. Attribute certificates are not supported in IKEv2 yet.
.TP
.B leftid
how
the left participant
should be identified for authentication;
defaults to
.BR left .
Can be an IP address (in any
.IR ttoaddr (3)
syntax)
or a fully-qualified domain name preceded by
.B @
(which is used as a literal string and not resolved).
.TP
.B leftsourceip
The internal source IP to use in a tunnel, also known as virtual IP. If the
value is
.BR %modeconfig ,
.BR %modecfg ,
.BR %config ,
or
.B %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. 
.TP
.B rightsourceip
The internal source IP to use in a tunnel for the remote peer. If the
value is
.B %config
on the responder side, the initiator must propose a address which is then echoed
back.
.TP
.B modeconfig
defines which mode is used to assign a virtual IP.
Accepted values are
.B push
and
.B pull
(the default).
Currently relevant for IKEv1 only since IKEv2 always uses the configuration
payload in pull mode.
.TP
.B 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
.B yes
(the default)
and
.BR 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
.B esp
parameter.
.TP
.B rekey
whether a connection should be renegotiated when it is about to expire;
acceptable values are
.B yes
(the default)
and
.BR no .
The two ends need not agree, but while a value of
.B no
prevents Pluto/Charon from requesting renegotiation,
it does not prevent responding to renegotiation requested from the other end,
so
.B no
will be largely ineffective unless both ends agree on it.
.TP
.B reauth
whether rekeying of an IKE_SA should also reauthenticate the peer. In IKEv1,
reauthentication is always done. In IKEv2, a value of
.B no
rekeys without uninstalling the IPsec SAs, a value of
.B yes
(the default) creates a new IKE_SA from scratch and tries to recreate
all IPsec SAs.
.TP
.B rekeyfuzz
maximum percentage by which
.B 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
.IR pluto (8),
currently
.BR 100% ).
The value of
.BR rekeymargin ,
after this random increase,
must not exceed
.BR keylife .
The value
.B 0%
will suppress time randomization.
Relevant only locally, other end need not agree on it.
.TP
.B rekeymargin
how long before connection expiry or keying-channel expiry
should attempts to
negotiate a replacement
begin; acceptable values as for
.B keylife
(default
.BR 9m ).
Relevant only locally, other end need not agree on it.
.TP
.B ike
IKE/ISAKMP SA encryption/authentication algorithm to be used, e.g.
.B aes128-sha1-modp2048
(encryption-integrity-dhgroup). In IKEv2, multiple algorithms and proposals
may be included, such as
.B aes128-aes256-sha1-modp1536-modp2048,3des-sha1-md5-modp1024.
.TP
.B esp
ESP encryption/authentication algorithm to be used
for the connection, e.g.
.B 3des-md5
(encryption-integrity-[dh-group]). If dh-group is specified, CHILD_SA setup
and rekeying include a separate diffe hellman exchange (IKEv2 only).
.TP
.B ah
AH authentication algorithm to be used
for the connection, e.g.
.B hmac-md5.
.SH "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.
.TP 10
.B auto
currently can have either the value
.B ignore
or
.B add
. 
.TP
.B cacert
defines a path to the CA certificate either relative to 
\fI/etc/ipsec.d/cacerts\fP or as an absolute path.
.TP
.B crluri
defines a CRL distribution point (ldap, http, or file URI)
.TP
.B crluri1
synonym for
.B crluri.
.TP
.B crluri2
defines an alternative CRL distribution point (ldap, http, or file URI)
.TP
.B ldaphost
defines an ldap host. Currently used by IKEv1 only.
.TP
.B ocspuri
defines an OCSP URI.
.TP
.B ocspuri1
synonym for
.B ocspuri.
.TP
.B ocspuri2
defines an alternative OCSP URI. Currently used by IKEv2 only.
.SH "CONFIG SECTIONS"
At present, the only
.B config
section known to the IPsec software is the one named
.BR setup ,
which contains information used when the software is being started
(see
.IR starter (8)).
Here's an example:
.PP
.ne 8
.nf
.ft B
.ta 1c
config setup
	plutodebug=all
	crlcheckinterval=10m
	strictcrlpolicy=yes
.ft
.fi
.PP
Parameters are optional unless marked ``(required)''.
The currently-accepted
.I parameter
names in a
.B config
.B setup
section are:
.TP 14
.B interfaces
virtual and physical interfaces for IPsec to use:
a single
\fIvirtual\fB=\fIphysical\fR pair, a (quoted!) list of pairs separated
by white space, or
.BR %none .
One of the pairs may be written as
.BR %defaultroute ,
which means: find the interface \fId\fR that the default route points to,
and then act as if the value was ``\fBipsec0=\fId\fR''.
.B %defaultroute
is the default;
.B %none
must be used to denote no interfaces.
(This parameter is used with the KLIPS IPsec stack only.)
.TP
.B dumpdir
in what directory should things started by
.I setup
(notably the Pluto daemon) be allowed to
dump core?
The empty value (the default) means they are not
allowed to.
This feature is currently not supported by the ipsec starter.
.TP
.B charonstart
whether to start the IKEv2 daemon Charon or not.
Accepted values are
.B yes
(the default)
or
.BR no .
.TP
.B charondebug
how much Charon debugging output should be logged.
A comma separated list containing type level/pairs may
be specified, e.g:
.B dmn 3, ike 1, net -1.
Acceptable values for types are
.B dmn, mgr, ike, chd, job, cfg, knl, net, enc, lib
and the level is one of
.B -1, 0, 1, 2, 3, 4
(for silent, audit, control, controlmore, raw, private).
.TP
.B plutostart
whether to start the IKEv1 daemon Pluto or not.
Accepted values are
.B yes
(the default)
or
.BR no .
.TP
.B plutodebug
how much Pluto debugging output should be logged.
An empty value,
or the magic value
.BR none ,
means no debugging output (the default).
The magic value
.B all
means full output.
Otherwise only the specified types of output
(a quoted list, names without the
.B \-\-debug\-
prefix,
separated by white space) are enabled;
for details on available debugging types, see
.IR pluto (8).
.TP
.B prepluto
shell command to run before starting Pluto
(e.g., to decrypt an encrypted copy of the
.I 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
.I /dev/tty
or equivalent for their interaction.
Default is none.
.TP
.B postpluto
shell command to run after starting Pluto
(e.g., to remove a decrypted copy of the
.I 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
.I /dev/tty
or equivalent for their interaction.
Default is none.
.TP
.B 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
.B yes
(the default)
and
.BR no .
(This parameter is used with the KLIPS IPsec stack only.)
.TP
.B hidetos
whether a tunnel packet's TOS field should be set to
.B 0
rather than copied from the user packet inside;
acceptable values are
.B yes
(the default)
and
.BR no .
(This parameter is used with the KLIPS IPsec stack only.)
.TP
.B 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
.B yes
(the default)
and
.BR no .
Participant IDs normally \fIare\fR unique,
so a new (automatically-keyed) connection using the same ID is
almost invariably intended to replace an old one.
.TP
.B overridemtu
value that the MTU of the ipsec\fIn\fR interface(s) should be set to,
overriding IPsec's (large) default.
(This parameter is used in special situations with the KLIPS IPsec stack only.)
.TP
.B nat_traversal
activates NAT traversal by accepting source ISAKMP different from udp/500 and
floating to udp/4500 if a NAT situation is detected. Used by IKEv1 only since
NAT traversal is always activated with IKEv2.
Accepted values are
.B yes
and
.B no
(the default).
.TP
.B keep_alive
interval in seconds between NAT keep alive packets.
.TP
.B virtual_private
.TP
.B crlcheckinterval
interval in seconds. CRL fetching is enabled if the value is greater than zero.
Asynchronous periodic checking for fresh CRLs is done by IKEv1 only.
.TP
.B 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
.B yes
and
.B no
(the default).
.TP
.B strictcrlpolicy
defines if a fresh CRL must be available in order for the peer authentication based
on RSA signatures to succeed.
Accepted values are
.B yes
and
.B no
(the default).
IKEv2 additionally recognizes
.B ifuri
which reverts to
.B yes
if at least one CRL URI is defined and to
.B no
if no URI is known.
.TP
.B nocrsend
no certificate request payloads will be sent.
Accepted values are
.B yes
and
.B no
(the default).
Used by IKEv1 only.
.TP
.B pkcs11module
defines the path to a dynamically loadable PKCS #11 library.
.TP
.B 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
.B yes
and
.B no
(the default).
.TP
.B pkcs11proxy
Pluto will act as a PKCS #11 proxy accessible via the whack interface.
Accepted values are
.B yes
and
.B no
(the default).
.SH CHOOSING A CONNECTION
.PP
When choosing a connection to apply to an outbound packet caught with a 
.BR %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.
.PP
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.
.SH FILES
.nf
/etc/ipsec.conf
/etc/ipsec.d/aacerts
/etc/ipsec.d/acerts
/etc/ipsec.d/cacerts
/etc/ipsec.d/certs
/etc/ipsec.d/crls

.SH SEE ALSO
ipsec(8), pluto(8), starter(8), ttoaddr(3), ttodata(3)
.SH 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. IKEv2-specific features by Martin Willi.
.SH BUGS
.PP
If conns are to be added before DNS is available, \fBleft=\fP\fIFQDN\fP
will fail.