Provided by: openswan_2.6.38-1_amd64 
NAME
ipsec.conf - IPsec configuration and connections
DESCRIPTION
The optional ipsec.conf file specifies most configuration and control information for the Openswan IPsec
subsystem. (The major exception is secrets for authentication; see ipsec.secrets(5).) Its contents are
not security-sensitive unless manual keying is being done for more than just testing, in which case the
encryption/authentication keys in the descriptions for the manually-keyed connections are very sensitive
(and those connection descriptions are probably best kept in a separate file, via the include facility
described below).
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 and alsoflip parameters
(described below) which permit splitting a single logical section (e.g. a connection description) into
several actual sections.
The first significant line of the file must specify the version of this specification that it conforms
to:
version 2
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.) This allows, for
example, keeping the encryption keys for a connection in a separate file from the rest of the
description, by using both an also parameter and an include line. (Caution, see BUGS below for some
restrictions.)
alsoflip
can be used in a conn section. It acts like an also that flips the referenced section's entries
left-for-right.
Parameter names beginning with x- (or X-, or x_, or X_) are reserved for user extensions and will never
be assigned meanings by IPsec. Parameters with such names must still observe the syntax rules (limits on
characters used in the name; no white space in a non-quoted value; no newlines or double quotes within
the value). All other as-yet-unused parameter names are reserved for future IPsec improvements.
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 also or alsoflip parameters.
Currently there are two types of section: a config section specifies general configuration information
for IPsec, while a conn section specifies an IPsec connection.
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 to ipsec_auto(8) and ipsec_manual(8).
Here's a simple example:
conn snt
left=10.11.11.1
leftsubnet=10.0.1.0/24
leftnexthop=172.16.55.66
leftsourceip=10.0.1.1
right=192.168.22.1
rightsubnet=10.0.2.0/24
rightnexthop=172.16.88.99
rightsourceip=10.0.2.1
keyingtries=%forever
A note on terminology... In automatic keying, 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 data path (a set of “IPsec SAs”) used for user packets is herein referred to as the
“connection”; the path used for negotiations (built with “ISAKMP SAs”) is referred to as the “keying
channel”.
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)”; a parameter required for manual keying need not be
included for a connection which will use only automatic keying, and vice versa.
CONN PARAMETERS: GENERAL
The following parameters are relevant to both automatic and manual keying. 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.
connaddrfamily
the connection addrress family of the connection; currently the accepted values are ipv4 (the
default); or ipv6. This option is confusing, especially when doing IPv4-in-IPv6 or IPv6-in-IPv4
tunnels. The developers hope to remove this option in the near future for proper auto-detection. For
now, set connaddrfamily= to the family of the *subnet= options, and if those are not defined, to the
family of the left=/right= options.
IPv6 is supported with NETKEY since openswan 2.4 and with KLIPS since Openswan 2.6.33
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.
left
(required) the IP address of the left participant's public-network interface, in any form accepted by
ipsec_ttoaddr(3). Currently, IPv4 and IPv6 IP addresses are supported. There are 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. The value %opportunistic signifies
that both left and leftnexthop are to be filled in (by automatic keying) from DNS data for left's
client. The value can also contain the interface name, which will then later be used to obtain the IP
address from to fill in. For example %ppp0 The values %group and %opportunisticgroup makes this a
policy group conn: one that will be instantiated into a regular or opportunistic conn for each CIDR
block listed in the policy group file with the same name as the conn.
If using IP addresses in combination with NAT, always use the actual local machine's (NAT'ed) IP
address, and if the remote (eg right=) is NAT'ed as well, the remote's public (not NAT'ed) IP
address. Note that this makes the configuration no longer symmetrical on both sides, so you cannot
use an identical configuration file on both hosts.
leftsubnet
private subnet behind the left participant, expressed as network/netmask (actually, any form
acceptable to ipsec_ttosubnet(3)); Currentlly, IPv4 and IPv6 ranges are supported. if omitted,
essentially assumed to be left/32, signifying that the left end of the connection goes to the left
participant only
It supports two magic shorthands vhost: and vnet:, which can list subnets in the same syntax as
virtual_private. The value %priv expands to the networks specified in virtual_private. The value %no
means no subnet. A common use for allowing roadwarrios to come in on public IPs or via accepted NATed
networks from RFC1918 is to use leftsubnet=vhost:%no,%priv. The vnet: option can be used to allow
RFC1918 subnets without hardcoding them. When using vnet the connection will instantiate, allowing
for multiple tunnels with different subnets.
leftsubnets
specify multiple private subnets behind the left participant, expressed as { networkA/netmaskA
networkB/netmaskB [...] } If both a leftsubnets= and rightsubnets= is defined, all combinations of
subnet tunnels will be instantiated. You cannot use leftsubnet and leftsubnets together. For examples
see testing/pluto/multinet-*.
leftprotoport
allowed protocols and ports over connection, also called Port Selectors. The argument is in the form
protocol, which can be a number or a name that will be looked up in /etc/protocols, such as
leftprotoport=icmp, or in the form of protocol/port, such as tcp/smtp. Ports can be defined as a
number (eg. 25) or as a name (eg smtp) which will be looked up in /etc/services. A special keyword
%any can be used to allow all ports of a certain protocol. The most common use of this option is for
L2TP connections to only allow l2tp packets (UDP port 1701), eg: leftprotoport=17/1701. Some clients,
notably older Windows XP and some Mac OSX clients, use a random high port as source port. In those
cases rightprotoport=17/%any can be used to allow all UDP traffic on the connection. Note that this
option is part of the proposal, so it cannot be arbitrarily left out if one end does not care about
the traffic selection over this connection - both peers have to agree. The Port Selectors show up in
the output of ipsec eroute and ipsec auto --status eg:"l2tp":
193.110.157.131[@aivd.xelernace.com]:7/1701...%any:17/1701 This option only filters outbound traffic.
Inbound traffic selection must still be based on firewall rules activated by an updown script. The
variablees $PLUTO_MY_PROTOCOL, $PLUTO_PEER_PROTOCOL, $PLUTO_MY_PORT, and $PLUTO_PEER_PORT are
available for use in updown scripts. Older workarounds for bugs involved a setting of 17/0 to denote
any single UDP port (not UDP port 0). Some clients, most notably OSX, uses a random high port,
instead of port 1701 for L2TP.
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.
leftsourceip
the IP address for this host to use when transmitting a packet to the other side of this link.
Relevant only locally, the other end need not agree. This option is used to make the gateway itself
use its internal IP, which is part of the leftsubnet, to communicate to the rightsubnet or right.
Otherwise, it will use its nearest IP address, which is its public IP address. This option is mostly
used when defining subnet-subnet connections, so that the gateways can talk to each other and the
subnet at the other end, without the need to build additional host-subnet, subnet-host and host-host
tunnels. Both IPv4 and IPv6 addresses are supported.
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. An
example to enable routing when using the NETKEY stack, one can use:
leftupdown="ipsec _updown --route yes"
See ipsec_pluto(8) for details. Relevant only locally, other end need not agree on it.
leftfirewall
This option is obsolete and should not used anymore.
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)).
The implementation of this makes certain assumptions about firewall setup, and the availability of the
Linux Advanced Routing tools. 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.
CONN PARAMETERS: AUTOMATIC KEYING
The following parameters are relevant only to automatic keying, and are ignored in manual keying. 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.
auto
what operation, if any, should be done automatically at IPsec startup; currently-accepted values are
add (signifying an ipsec auto --add), route (signifying that plus an ipsec auto --route), start
(signifying that plus an ipsec auto --up), manual (signifying an ipsec manual --up), and ignore (also
the default) (signifying no automatic startup operation). See the config setup discussion below.
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).
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.
ike
IKE encryption/authentication algorithm to be used for the connection (phase 1 aka ISAKMP SA). The
format is "cipher-hash;modpgroup, cipher-hash;modpgroup, ..." Any left out option will be filled in
with all allowed default options. Multiple proposals are separated by a comma. If an ike= line is
specified, no other received proposals will be accepted. Formerly there was a distinction (by using a
"!" symbol) between "strict mode" or not. That mode has been obsoleted. If an ike= option is
specified, the mode is always strict, meaning no other received proposals will be accepted. Some
examples are ike=3des-sha1,aes-sha1, ike=aes, ike=aes128-md5;modp2048, ike=aes128-sha1;dh22,
ike=3des-md5;modp1024,aes-sha1;modp1536 or ike=modp1536. The options must be suitable as a value of
ipsec_spi(8)'s --ike option. The default is to use IKE, and to allow all combinations of:
cipher: 3des or aes
hash: sha1 or md5
pfsgroup (DHgroup): modp1024 or modp1536
If Openswan was compiled with extra INSECURE and BROKEN options, then the des (1des) and null cipher,
as well as modp768 are available. This turns your VPN into a joke. Do not enable these options.
If openswan was compiled with USE_MODP_RFC5114 support, then Diffie-Hellman groups 22, 23 and 24 are
also implemented as per RFC-5114. Instead of the modp key syntax, use the "dh" keyword, for example
ike=3des-sha1;dh23
phase2
Sets the type of SA that will be produced. Valid options are: esp for encryption (the default), and
ah for authentication only.
phase2alg
Specifies the algorithms that will be offered/accepted for a phase2 negotiation. If not specified, a
secure set of defaults will be used. Sets are separated using comma's.
The default values are the same as for ike= Note also that not all ciphers available to the kernel
(eg through CryptoAPI) are necessarilly supported here.
The format for ESP is ENC-AUTH followed by an optional PFSgroup. For instance, "3des-md5" or
"aes256-sha1;modp2048" or "aes-sha1,aes-md5".
For RFC-5114 DH groups, use the "dh" keyword, eg "aes256-sha1;dh23"
The format for AH is AUTH followed by an optional PFSgroup. For instance, "md5" or "sha1;modp1536".
A special case is AES CCM, which uses the syntax of "phase2alg=aes_ccm_a-152-null"
esp
This option is obsolete. Please use phase2alg instead.
ah
AH authentication algorithm to be used for the connection, e.g here. hmac-md5 The options must be
suitable as a value of ipsec_spi(8)'s --ah option. The default is not to use AH. If for some
(invalid) reason you still think you need AH, please use esp with the null encryption cipher instead.
Note also that not all ciphers available to the kernel (eg through CryptoAPI) are necessarilly
supported here.
ikev2
IKEv2 (RFC4309) settings to be used. Currently the accepted values are permit, (the default)
signifying no IKEv2 should be transmitted, but will be accepted if the other ends initiates to us
with IKEv2; never or no signifying no IKEv2 negotiation should be transmitted or accepted; propose or
yes signifying that we permit IKEv2, and also use it as the default to initiate; insist, signifying
we only accept and receive IKEv2 - IKEv1 negotiations will be rejected.
If the ikev2= setting is set to permit or propose, Openswan will try and detect a "bid down" attack
from IKEv2 to IKEv1. Since there is no standard for transmitting the IKEv2 capability with IKEv1,
Openswan uses a special Vendor ID "CAN-IKEv2". If a fall back from IKEv2 to IKEv1 was detected, and
the IKEv1 negotiation contains Vendor ID "CAN-IKEv2", Openswan will immediately attempt and IKEv2
rekey and refuse to use the IKEv1 connection. With an ikev2= setting of insist, no IKEv1 negotiation
is allowed, and no bid down attack is possible.
sareftrack
Set the method of tracking reply packets with SArefs when using an SAref compatible stack. Currently
only the mast stack supports this. Acceptable values are yes (the default), no or conntrack. This
option is ignored when SArefs are not supported. This option is passed as PLUTO_SAREF_TRACKING to the
updown script which makes the actual decisions whether to perform any iptables/ip_conntrack
manipulation. A value of yes means that an IPSEC mangle table will be created. This table will be
used to match reply packets. A value of conntrack means that additionally, subsequent packets using
this connection will be marked as well, reducing the lookups needed to find the proper SAref by using
the ip_conntrack state. A value of no means no IPSEC mangle table is created, and SAref tracking is
left to a third-party (kernel) module. In case of a third party module, the SArefs can be relayed
using the HAVE_STATSD deamon.
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 %fromcert causes the ID to be set to a DN
taken from a certificate that is loaded. Prior to 2.5.16, this was the default if a certificate was
specified. The magic value %none sets the ID to no ID. This is included for completeness, as the ID
may have been set in the default conn, and one wishes for it to default instead of being explicitly
set. 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.
leftrsasigkey
the left participant's public key for RSA signature authentication, in RFC 2537 format using
ipsec_ttodata(3) encoding. The magic value %none means the same as not specifying a value (useful to
override a default). The value %dnsondemand (the default) means the key is to be fetched from DNS at
the time it is needed. The value %dnsonload means the key is to be fetched from DNS at the time the
connection description is read from ipsec.conf; currently this will be treated as %none if right=%any
or right=%opportunistic. The value %dns is currently treated as %dnsonload but will change to
%dnsondemand in the future. The identity used for the left participant must be a specific host, not
%any or another magic value. The value %cert will load the information required from a certificate
defined in %leftcert and automatically define leftid for you. Caution: if two connection
descriptions specify different public keys for the same leftid, confusion and madness will ensue.
leftrsasigkey2
if present, a second public key. Either key can authenticate the signature, allowing for key
rollover.
leftcert
If you are using leftrsasigkey=%cert this defines the certificate you would like to use. It should
point to a X.509 encoded certificate file. If you do not specify a full pathname, by default it will
look in /etc/ipsec.d/certs. If openswan has been compiled with USE_LIBNSS=true, then openswan will
also check the NSS database for RSA keys. These can be software or hardware.
leftca
specifies the authorized Certificate Authority (CA) that signed the certificate of the peer. If
undefined, it defaults to the CA that signed the certificate specified in leftcert. The special
rightca=%same is implied when not specifying a rightca and means that only peers with certificates
signed by the same CA as the leftca will be allowed. This option is only useful in complex multi CA
certificate situations. When using a single CA, it can be safely omitted for both left and right.
leftsendcert
This option configures when Openswan will send X.509 certificates to the remote host. Acceptable
values are yes|always (signifying that we should always send a certificate), ifasked (signifying that
we should send a certificate if the remote end asks for it), and no|never (signifying that we will
never send a X.509 certificate). The default for this option is ifasked which may break compatibility
with other vendor's IPSec implementations, such as Cisco and SafeNet. If you find that you are
getting errors about no ID/Key found, you likely need to set this to always. This per-conn option
replaces the obsolete global nocrsend option.
leftxauthserver
Left is an XAUTH server. This can use PAM for authentication or md5 passwords in /etc/ipsec.d/passwd.
These are additional credentials to verify the user identity, and should not be confused with the
XAUTH group secret, which is just a regular PSK defined in ipsec.secrets. The other side of the
connection should be configured as rightxauthclient. XAUTH connections cannot rekey, so rekey=no
should be specified in this conn. For further details on how to compile and use XAUTH, see
README.XAUTH. Acceptable values are yes or no (the default).
leftxauthclient
Left is an XAUTH client. The xauth connection will have to be started interactively and cannot be
configured using auto=start. Instead, it has to be started from the commandline using ipsec auto --up
connname. You will then be prompted for the username and password. To setup an XAUTH connection
non-interactively, which defeats the whole purpose of XAUTH, but is regularly requested by users, it
is possible to use a whack command - ipsec whack --name baduser --ipsecgroup-xauth --xauthname
badusername --xauthpass password --initiate The other side of the connection should be configured as
rightxauthserver. Acceptable values are yes or no (the default).
leftxauthusername
The XAUTH username associated with this XAUTH connection. The XAUTH password can be configured in the
ipsec.secrets file.
leftmodecfgserver
Left is a Mode Config server. It can push network configuration to the client. Acceptable values are
yes or no (the default).
leftmodecfgclient
Left is a Mode Config client. It can receive network configuration from the server. Acceptable values
are yes or no (the default).
modecfgpull
Pull the Mode Config network information from the server. Acceptable values are yes or no (the
default).
modecfgdns1, modecfgdns2, modecfgwins1, modecfgwins2
Specify the IP address for DNS or WINS servers for the client to use.
remote_peer_type
Set the remote peer type. This can enable additional processing during the IKE negotiation.
Acceptable values are cisco or ietf (the default). When set to cisco, support for Cisco IPsec gateway
redirection and Cisco obtained DNS and domainname are enabled. This includes automatically updating
(and restoring) /etc/resolv.conf. These options require that XAUTH is also enabled on this
connection.
nm_configured
Mark this connection as controlled by Network Manager. Acceptable values are yes or no (the default).
Currently, setting this to yes will cause openswan to skip reconfiguring resolv.conf when used with
XAUTH and ModeConfig.
forceencaps
In some cases, for example when ESP packets are filtered or when a broken IPsec peer does not
properly recognise NAT, it can be useful to force RFC-3948 encapsulation. forceencaps=yes forces the
NAT detection code to lie and tell the remote peer that RFC-3948 encapsulation (ESP in UDP port 4500
packets) is required. For this option to have any effect, the setup section option nat_traversal=yes
needs to be set. Acceptable values are yes or no (the default).
overlapip
a boolean (yes/no) that determines, when *subnet=vhost: is used, if the virtual IP claimed by this
states created from this connection can with states created from other connections.
Note that connection instances created by the Opportunistic Encryption or PKIX (x.509) instantiation
system are distinct internally. They will inherit this policy bit.
The default is no.
This feature is only available with kernel drivers that support SAs to overlapping conns. At present
only the (klips)mast protocol stack supports this feature.
dpddelay
Set the delay (in seconds) between Dead Peer Dectection (RFC 3706) keepalives (R_U_THERE,
R_U_THERE_ACK) that are sent for this connection (default 30 seconds). If dpddelay is set, dpdtimeout
also needs to be set.
dpdtimeout
Set the length of time (in seconds) we will idle without hearing either an R_U_THERE poll from our
peer, or an R_U_THERE_ACK reply. After this period has elapsed with no response and no traffic, we
will declare the peer dead, and remove the SA (default 120 seconds). If dpdtimeout is set, dpdaction
also needs to be set.
dpdaction
When a DPD enabled peer is declared dead, what action should be taken. hold (default) means the
eroute will be put into %hold status, while clear means the eroute and SA with both be cleared.
restart means the the SA will immediately be renegotiated, and restart_by_peer means that ALL SA's to
the dead peer will renegotiated.
dpdaction=clear is really only useful on the server of a Road Warrior config.
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); Since there is
no reason to ever refuse PFS, Openswan will allow a connection defined with pfs=no to use PFS anyway.
Acceptable values are yes (the default) and no.
pfsgroup
This option is obsoleted, please use phase2alg if you need the pfs to be different from phase1 (the
default) using: phase2alg=aes128-md5;modp1024
aggrmode
Use Aggressive Mode instead of Main Mode. Aggressive Mode is less secure, and vulnerable to Denial Of
Service attacks. It is also vulnerable to brute force attacks with software such as ikecrack. It
should not be used, and it should especially not be used with XAUTH and group secrets (PSK). If the
remote system administrator insists on staying irresponsible, enable this option.
Aggressive Mode is further limited to only proposals with one DH group as there is no room to
negotiate the DH group. Therefor it is mandatory for Aggressive Mode connections that both ike= and
phase2alg= options are specified with only fully specified proposal using one DH group. Acceptable
values are yes or no (the default).
The ISAKMP SA is created in exchange 1 in aggressive mode. Openswan has to send the exponent during
that exchange, so it has to know what DH group to use before starting. This is why you can not have
multiple DH groups in aggressive mode. In IKEv2, which uses a similar method to IKEv1 Aggressive
Mode, there is a message to convey the DH group is wrong, and so an IKEv2 connection can actually
recover from picking the wrong DH group by restarting its negotiation.
salifetime
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 8h, maximum 24h). Normally, the connection is
renegotiated (via the keying channel) before it expires. The two ends need not exactly agree on
salifetime, although if they do not, there will be some clutter of superseded connections on the end
which thinks the lifetime is longer.
The keywords "keylife" and "lifetime" are aliases for "salifetime."
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 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.
rekeymargin
how long before connection expiry or keying-channel expiry should attempts to negotiate a replacement
begin; acceptable values as for salifetime (default 9m). Relevant only locally, other end need not
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 ipsec_pluto(8), currently 100%). The value of rekeymargin, after
this random increase, must not exceed salifetime. The value 0% will suppress time randomization.
Relevant only locally, other end need not agree on it.
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”
(obsolete: this can be written 0). Relevant only locally, other end need not agree on it.
ikelifetime
how long the keying channel of a connection (buzzphrase: “ISAKMP SA”) should last before being
renegotiated; acceptable values as for keylife (default set by ipsec_pluto(8), currently 1h, maximum
24h). The two-ends-disagree case is similar to that of keylife.
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). The two ends need not agree. 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.
metric
Set the metric for the routes to the ipsecX or mastX interface. This makes it possible to do host
failover from another interface to ipsec using route management. This value is passed to the _updown
scripts as PLUTO_METRIC. This option is only available with KLIPS or MAST on Linux. Acceptable values
are positive numbers, with the default being 1.
mtu
Set the mtu for the route(s) to the remote endpoint and/or subnets. This is sometimes required when
the overhead of the IPsec encapsultion would cause the packet the become too big for a router on the
path. Since IPsec cannot trust any unauthenticated ICMP messages, PATH MTU discovery does not work.
This can also be needed when using "6to4" IPV6 deployments, which adds another header on the packet
size. Acceptable values are positive numbers. There is no default.
disablearrivalcheck
whether KLIPS's normal tunnel-exit check (that a packet emerging from a tunnel has plausible
addresses in its header) should be disabled; acceptable values are yes and no (the default).
Tunnel-exit checks improve security and do not break any normal configuration. Relevant only locally,
other end need not agree on it.
failureshunt
what to do with packets when negotiation fails. The default is none: no shunt; passthrough, drop, and
reject have the obvious meanings.
CONN PARAMETERS: MANUAL KEYING
This command was obsoleted around the same time that Al Gore invented the internet. ipsec manual was used
in the jurassic period to load static keys into the kernel. There are no rational reasons to use this,
and it is not supported anymore. If you need to create static SAs, then you can use ipsec spi and ipsec
eroute when using KLIPS or ip xfrm or setkey when using NETKEY.
No rational person uses static keys. They are not easier to use. REPEAT: they are not easier to use.
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=control
protostack=auto
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 ``@''.
protostack
decide which protocol stack is going to be used. Valid values are "auto", "klips", "netkey" and
"mast". The "mast" stack is a variation for the klips stack.
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, or when
using the NETKEY stack. 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).)
listen
IP address to listen on (default depends on interfaces= setting). Currently only accepts one IP
address.
nat_traversal
whether to accept/offer to support NAT (NAPT, also known as "IP Masqurade") workaround for IPsec.
Acceptable values are: yes and no (the default). This parameter may eventually become per-connection.
disable_port_floating
whether to enable the newer NAT-T standards for port floating. Acceptable values are no (the default)
and yes .
force_keepalive
whether to force sending NAT-T keep-alives to support NAT which are send to prevent the NAT router
from closing its port when there is not enough traffic on the IPsec connection. Acceptable values
are: yes and no (the default). This parameter may eventually become per-connection.
keep_alive
The delay (in seconds) for NAT-T keep-alive packets, if these are enabled using force_keepalive This
parameter may eventually become per-connection.
virtual_private
contains the networks that are allowed as subnet= for the remote clients when using the vhost: or
vnet: keywords in the subnet= parameters. In other words, the address ranges that may live behind a
NAT router through which a client connects. This value is usually set to all the RFC-1918 address
space, excluding the space used in the local subnet behind the NAT (An IP address cannot live at two
places at once). IPv4 address ranges are denoted as %v4:a.b.c.d/mm and IPv6 is denoted as
%v6:aaaa::bbbb:cccc:dddd:eeee/mm. One can exclude subnets by using the !. For example, if the VPN
server is giving access to 192.168.1.0/24, this option should be set to: virtual_private=
%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12,%v4:!192.168.1.0/24. This parameter is only
needed on the server side and not on the client side that resides behind the NAT router, as the
client will just use its IP address for the inner IP setting. This parameter may eventually become
per-connection. See also leftsubnet=
Note: It seems that T-Mobile in the US and Rogers/Fido in Canada have started using 25.0.0.0/8 as
their pre-NAT range. This range technically belows to the Defence Interoperable Network Services
Authority (DINSA), an agency of the Ministry of Defence of the United Kingdom. The network range
seems to not have been announced for decades, which is probably why these organisasions "borrowed"
this range. To support roadwarriors on these 3G networks, you might have to add it to the
virtual_private= line.
oe
a boolean (yes/no) that determines if Opportunistic Encryption will be enabled. Opportunistic
Encryption is the term to describe using IPsec tunnels without prearrangement. It uses IPSECKEY or
TXT records to announce public RSA keys for certain IP's or identities.
For a complete description see /doc/draft-richardson-ipsec-opportunistic.txt,
doc/opportunism-spec.txt and doc/opportunism.howto. See also the IETF BTNS working group and RFC4025.
The default is no.
This feature is only available with kernel drivers that support the caching of packets (%hold eroutes
or equivalent) that allows us to respond to a packet from an unknown IP address. At present only the
(klips)mast protocol stack supports this feature.
nhelpers
how many pluto helpers are started to help with cryptographic operations. Pluto will start (n-1) of
them, where n is the number of CPU's you have (including hypherthreaded CPU's). A value of 0 forces
pluto to do all operations in the main process. A value of -1 tells pluto to perform the above
calculation. Any other value forces the number to that amount.
crlcheckinterval
interval, specified in seconds, after which pluto will verify loaded X.509 CRL's for expiration. If
any of the CRL's is expired, or if they previously failed to get updated, a new attempt at updating
the CRL is made. The first attempt to update a CRL is started at two times the crlcheckinterval. If
set to 0, which is also the default value if this option is not specified, CRL updating is disabled.
strictcrlpolicy
if not set, pluto is tolerant about missing or expired X.509 Certificate Revocation Lists (CRL's),
and will allow peer certificates as long as they do not appear on an expired CRL. When this option is
enabled, all connections with an expired or missing CRL will be denied. Active connections will be
terminated at rekey time. This setup is more secure, but also dangerous. If the CRL is fetched
through an IPsec tunnel with a CRL that expired, the entire VPN server will be dead in the water
until a new CRL is manually transferred to the machine (if it allows non-IPsec connections).
Acceptable values are yes or no (the default).
forwardcontrol
This option is obsolete and ignored. Please use net.ipv4.ip_forward = 0 in /etc/sysctl.conf instead
to control the ip forwarding behaviour.
rp_filter
This option is obsolete and ignored. Please use the net.ipv4.conf/[iface]/rp_filter = 0 options in
/etc/sysctl.conf instead. This option is badly documented; it must be 0 in many cases for ipsec to
function.
syslog
the syslog(2) “facility” name and priority to use for startup/shutdown log messages, default
daemon.error.
klipsdebug
how much KLIPS 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 separated by white space) are enabled; for details on available
debugging types, see ipsec_klipsdebug(8). This KLIPS option has no effect on NETKEY, Windows or BSD
stacks.
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).
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.
plutorestartoncrash
prevent pluto from restarting after it crashed. This option should only be used when debugging a
crasher. It will prevent overwriting a core file on a new start, or a cascade of core files. This
option is also required if used with plutostderrlog= to avoid clearing the logs of the crasher.
Values can be yes (the default) or no.
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.
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.
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.
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.
This KLIPS option has no effect on NETKEY, Windows or BSD stacks.
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. This KLIPS option has no effect on NETKEY,
Windows or BSD stacks.
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. This KLIPS option has no effect on NETKEY,
Windows or BSD stacks.
IMPLICIT CONNS
The system automatically defines several conns to implement default policy groups. Each can be overridden
by explicitly defining a new conn with the same name. If the new conn has auto=ignore, the definition is
suppressed.
Here are the automatically supplied definitions.
conn clear
type=passthrough
authby=never
left=%defaultroute
right=%group
auto=route
conn clear-or-private
type=passthrough
left=%defaultroute
leftid=%myid
right=%opportunisticgroup
failureshunt=passthrough
keyingtries=3
ikelifetime=1h
salifetime=1h
rekey=no
auto=route
conn private-or-clear
type=tunnel
left=%defaultroute
leftid=%myid
right=%opportunisticgroup
failureshunt=passthrough
keyingtries=3
ikelifetime=1h
salifetime=1h
rekey=no
auto=route
conn private
type=tunnel
left=%defaultroute
leftid=%myid
right=%opportunisticgroup
failureshunt=drop
keyingtries=3
ikelifetime=1h
salifetime=1h
rekey=no
auto=route
conn block
type=reject
authby=never
left=%defaultroute
right=%group
auto=route
# default policy
conn packetdefault
type=tunnel
left=%defaultroute
leftid=%myid
left=0.0.0.0/0
right=%opportunistic
failureshunt=passthrough
keyingtries=3
ikelifetime=1h
salifetime=1h
rekey=no
auto=route
These conns are not affected by anything in conn %default. They will only work if %defaultroute works.
The leftid will be the interfaces IP address; this requires that reverse DNS records be set up properly.
The implicit conns are defined after all others. It is appropriate and reasonable to use
also=private-or-clear (for example) in any other opportunistic conn.
POLICY GROUP FILES
The optional files under /etc/ipsec.d/policy, including
/etc/ipsec.d/policies/clear
/etc/ipsec.d/policies/clear-or-private
/etc/ipsec.d/policies/private-or-clear
/etc/ipsec.d/policies/private
/etc/ipsec.d/policies/block
may contain policy group configuration information to supplement ipsec.conf. Their contents are not
security-sensitive.
These files are text files. Each consists of a list of CIDR blocks, one per line. White space followed by
# followed by anything to the end of the line is a comment and is ignored, as are empty lines.
A connection in ipsec.conf which has right=%group or right=%opportunisticgroup is a policy group
connection. When a policy group file of the same name is loaded, with
ipsec auto --rereadgroups
or at system start, the connection is instantiated such that each CIDR block serves as an instance's
right value. The system treats the resulting instances as normal connections.
For example, given a suitable connection definition private, and the file /etc/ipsec.d/policy/private
with an entry 192.0.2.3, the system creates a connection instance private#192.0.2.3. This connection
inherits all details from private, except that its right client is 192.0.2.3.
DEFAULT POLICY GROUPS
The standard Openswan install includes several policy groups which provide a way of classifying possible
peers into IPsec security classes: private (talk encrypted only), private-or-clear (prefer encryption),
clear-or-private (respond to requests for encryption), clear and block. Implicit policy groups apply to
the local host only, and are implemented by the IMPLICIT CONNECTIONS described above.
CHOOSING A CONNECTION [THIS SECTION IS EXTREMELY OUT OF DATE
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/policies/clear
/etc/ipsec.d/policies/clear-or-private
/etc/ipsec.d/policies/private-or-clear
/etc/ipsec.d/policies/private
/etc/ipsec.d/policies/block
SEE ALSO
ipsec(8), ipsec_ttoaddr(8), ipsec_auto(8), ipsec_manual(8), ipsec_rsasigkey(8)
HISTORY
Designed for the FreeS/WAN project <http://www.freeswan.org> by Henry Spencer.
BUGS
Before reporting new bugs, please ensure you are using the latest version of Openswan, and if not using
KLIPS, please ensure you are using the latest kernel code for your IPsec stack.
When type or failureshunt is set to drop or reject, Openswan blocks outbound packets using eroutes, but
assumes inbound blocking is handled by the firewall. Openswan 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.
The use of %any with the protoport= option is ambiguous. Should the SA permits any port through or should
the SA negotiate any single port through? The first is a basic conn with a wildcard. The second is a
template. The second is the current behaviour, and it's wrong for quite a number of uses involving TCP.
The keyword %one may be introduced in the future to separate these two cases.
ipsec_manual is not nearly as generous about the syntax of subnets, addresses, etc. as the usual Openswan
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.
First packet caching is only implemented for the KLIPS(NG) and MAST stacks. NETKEY returns POSIX-breaking
responses, visiable as connect: Resource temporarily unavailable errors. This affects Opportunistic
Encryption and DPD. Functionality on the BSD and Windows stacks is unknown.
Some state information is only available when using KLIPS, and will return errors on other IPsec stacks.
These include ipsec eroute, ipsec spi and ipsec look.
Multiple L2TP clients behind the same NAT router, and multiple L2TP clients behind different NAT routers
using the same Virtual IP is currently only working for the KLIPSNG stack.
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. This feature is planned for a future release.
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.
[FIXME: source] 04/21/2011 IPSEC.CONF(5)