Provided by: libreswan_4.14-1ubuntu2_amd64 
NAME
ipsec.conf - IPsec configuration and connections
DESCRIPTION
The ipsec.conf file specifies most configuration and control information for the Libreswan IPsec
subsystem. (The major exception is secrets for authentication; see ipsec.secrets(5).) Its contents are
not security-sensitive. Configurations can be added using this configuration file or by using ipsec whack
directly. This means that technically, the ipsec.conf file is optional, but a few warnings might show up
when this file is missing.
ipsec.conf 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 that are not within a
section.
A line that 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 that contains 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 /etc/ipsec.d/*.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 distinct sections.
The first significant line of the file may specify a version of this specification for backwards
compatibility with freeswan and openswan. It is ignored and unused. For compatibility with openswan,
specify:
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 that 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 that 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 that 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 that 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. %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) 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)”
CONN PARAMETERS: GENERAL
The following parameters are relevant to IKE automatic 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.
keyexchange
method of key exchange; the default and currently the only accepted value is ike
hostaddrfamily
the address family of the hosts; currently the accepted values are ipv4 and ipv6. The default is to
detect this based on the IP addresses specified or the IP addresses resolved, so this option is not
needed, unless you specify hostnames that resolve to both IPv4 and IPv6. This option used to be named
connaddrfamily but its use was broken so it was obsoleted in favour or using the new hostaddrfamily
and clientaddrfamily.
clientaddrfamily
the address family of the clients (subnets); currently the accepted values are ipv4 and ipv6. The
default is to detect this based on the network IP addresses specified or the network IP addresses
resolved, so this option is not needed, unless you specify names that resolve to both IPv4 and IPv6.
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 or DNS hostname of the left participant's public-network interface,
Currently, IPv4 and IPv6 IP addresses are supported. If a DNS hostname is used, it will be resolved
to an IP address on load time, and whenever a connection is rekeying or restarting (such as when
restarted via a DPD failure detection). This allows one to use a DNS hostname when the endpoint is on
a dynamic IP address.
There are 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); 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 (NATed) IP
address, and if the remote (eg right=) is NATed as well, the remote's public (not NATed) 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)); Currently, 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 roadwarriors 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= are defined, all combinations of
subnet tunnels will be established as IPsec tunnels. You cannot use leftsubnet= and leftsubnets=
together. For examples see testing/pluto/multinet-*. Be aware that when using spaces as separator,
that the entire option value needs to be in double quotes.
leftvti
the address/mask to configure on the VTI interface when vti-interface is set. It takes the form of
network/netmask (actually, any form acceptable to ipsec_ttosubnet(3)); Currently, IPv4 and IPv6
ranges are supported. This option is often used in combination with routed based VPNs.
leftaddresspool
address pool from where the IKEv1 ModeCFG or IKEv2 server can assign IP addresses to clients. When
configured as a server, using leftxauthserver=yes this option specifies the address pool from which
IP addresses are taken to assign the clients. The syntax of the address pool specifies a range (not a
CIDR) for IPv4 and CIDR for IPv6, in the following syntax:
rightaddresspool=192.168.1.100-192.168.1.200 or rightaddresspool=2001:db8:0:3:1::/97 Generally, the
rightaddresspool= option will be accompanied by rightxauthclient=yes, leftxauthserver=yes and
leftsubnet=0.0.0.0/0 option.
When leftaddresspool= is specified, the connection may not specify either leftsubnet= or
leftsubnets=. Address pools are fully allocated when the connection is loaded, so the ranges should
be sane. For example, specifying a range rightaddresspool=10.0.0.0-11.0.0.0 will lead to massive
memory allocation. Address pools specifying the exact same range are shared between different
connections. Different addresspools should not be defined to partially overlap.
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.
To filter on specific icmp type and code, use the higher 8 bits for type and the lower 8 bits for
port. For example, to allow icmp echo packets (type 8, code 0) the 'port' would be 0x0800, or 2048 in
decimal, so you configure leftprotoport=icmp/2048. Similarly, to allow ipv6-icmp Neighbour Discovery
which has type 136 (0x88) and code 0(0x00) this becomes 0x8800 or in decimal 34816 resulting in
leftprotoport=ipv6-icmp/34816 .
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.libreswan.org]: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
variables $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, 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 XFRM stack, one can use:
leftupdown="ipsec _updown --route yes"
To disable calling an updown script, set it to the empty string, eg leftupdown="" or
leftupdown="%disabled".
See ipsec_pluto(8) for details. Relevant only locally, other end need not agree on it.
leftcat
Whether to perform Client Address Translation ("CAT") when using Opportunistic IPsec behind NAT.
Accepted values are no (the default) and yes. This option should only be enabled on the special
Opportunistic IPsec connections, usually called "private" and "private-or-clear". When set, this
option causes the given addresspool IP from the remote peer to be NATed with iptables. It will also
install an additional IPsec SA policy to cover the pre-NAT IP. See the Opportunistic IPsec
information on the libreswan website for more information and examples.
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 to automatic keying via IKE. 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), ondemand (signifying that plus an ipsec auto --ondemand), start
(signifying that plus an ipsec auto --up), and ignore (also the default) (signifying no automatic
startup operation), and keep (signifying an add plus an attempt to keep the connection up once the
remote peer brought it up). 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).
The option ondemand used to be called route
authby
how the two security gateways should authenticate each other; the default value is rsasig,ecdsa which
allows ECDSA with SHA-2 and RSA with SHA2 or SHA1. To limit this further, there are the options of
ecdsa for ECDSA digital signatures using SHA-2, rsa-sha2 for RSASSA-PSS digital signatures based
authentication with SHA2-256, rsa-sha2_384 for RSASSA-PSS digital signatures based authentication
with SHA2-384, rsa-sha2_512 for RSASSA-PSS digital signatures based authentication with SHA2-512,
rsa-sha1 for RSA-PKCSv1.5 digital signatures based authentication with SHA1, secret for shared
secrets (PSK) authentication, secret|rsasig for either, never if negotiation is never to be attempted
or accepted (useful for shunt-only conns), and null for null-authentication.
If asymmetric authentication is requested, IKEv2 must be enabled, and the options leftauth= and
rightauth= should be used instead of authby.
For IKEv1, SHA2 based signatures are not defined and ECDSA is not implemented, so the default authby=
value is rsa-sha1. Using authby=rsasig results in only rsa-sha1 as well. For IKEv2, using
authby=rsasig means using rsa-sha2_512, rsa-sha2_384, rsa-sha2_256 and rsa-sha1, where rsa-sha1 will
used only if RFC 7427 is not supported by the peer.
As per RFC 8221, authby=rsa-sha1 is only supported in the old style, meaning RSA-PKCSv1.5. The SHA2
variants are only supported for the new style of RFC 7427, so authby=rsa-sha2 will use the new style.
The default authby= will remove rsa-sha1 in the near future. It is strongly recommended that if
certificates are used, the certificates and the authby= signature methods used are the same, as it
increases interoperability and keeps the authentication of everything within one digital signature
system.
Digital signatures are superior in every way to shared secrets. Especially IKEv1 in Aggressive Mode
is vulnerable to offline dictionary attacks and is performed routinely by at least the NSA on
monitored internet traffic globally. The never option is only used for connections that do not
actually start an IKE negotiation, such as type=passthrough connections. The auth method null is used
for "anonymous opportunistic IPsec" and should not be used for regular pre-configured IPsec VPNs.
ike
IKE encryption/authentication algorithm to be used for the connection (phase 1 aka ISAKMP SA or IKE
SA). If this option is not set, the builtin defaults will be used. This is the preferred method, and
allows for gradual automatic updates using the same configuration. Some distributions, such as Fedora
and RHEL/CentOS, use a System Wide Crypto Policy that sets the default ike= (and esp=) lines.
Specifying your own ike= line means overriding all these system or software recommended defaults, but
can be necessary at times. Note that libreswan does not support using a PRF algorithm that is
different from the INTEGRITY (hash) algorithm by design.
The format is "cipher-hash;modpgroup, cipher-hash;modpgroup, ..." Any omitited option will be filled
in with all allowed default values. Multiple proposals are separated by a comma. If an ike= line is
specified, no other received proposals will be accepted than those specified on the IKE line. Some
examples are ike=3des-sha1,aes-sha1, ike=aes, ike=aes_ctr, ike=aes_gcm256-sha2,
ike=aes128-md5;modp2048, ike=aes256-sha2;dh19, ike=aes128-sha1;dh22,
ike=3des-md5;modp1024,aes-sha1;modp1536.
IKEv2 allows combining elements into a single proposal. These can be specified by using the + symbol.
An example is: ike=aes_gcm+chacha20_poly1305;dh14+dh19,aes+3des-sha2+sha1;dh14. Note that AEAD
algorithms (aes_gcm, aes_ccm, chacha20_poly1305) and non-AEAD algorithms (aes, 3des) cannot be
combined into a single proposal. To support aes and aes_gcm, two proposals separated by a comma must
be used.
The default IKE proposal depends on the version of libreswan used. It follow the recommendations of
RFC4306, RFC7321 and as of this writing their successor draft documents RFC4306bis and RFC7321bis. As
for libreswan 3.32, SHA1 and MODP1536(dh5) are still allowed per default for backwards compatibility,
but 3DES and MODP1024(dh2) are not allowed per default. As of libreswan 4.x, modp1024(dh2) support is
no longer compiled in at all. For IKEv2, the defaults include AES, AES-GCM, DH14 and stronger, and
SHA2. The default key size is 256 bits. The default AES_GCM ICV is 16 bytes.
Note that AES-GCM is an AEAD algorithm, meaning that it performs encryption+authentication in one
step. This means that AES-GCM must not specify an authentication algorithm. However, for IKE it does
require a PRF function, so the second argument to an AEAD algorithm denotes the PRF. So
ike=aes_gcm-sha2 means propose AES_GCM with SHA2 as the prf. Note that for phase2alg, there is no
prf, so AES-GCM is specified for ESP as esp=aes_gcm-null. The AES-GCM and AES-CCM algorithms support
8,12 and 16 byte ICV's. These can be specified using a postfix, for example aes_gcm_a (for 8),
aes_gcm_b (for 12) and aes_gcm_c (for 16). The default (aes_gcm without postfix) refers to the 16
byte ICV version. It is strongly recommended to NOT use the 8 or 12 byte versions of GCM or CCM.
These versions are NOT included in the default and will be removed in a future version, following the
recommendation of RFC 8247 or it successor.
Weak algorithms are regularly removed from libreswan. Currently, 1DES and modp768(DH1) have been
removed and modp1024(DH2) has been disabled at compile time. Additionally, MD5 and SHA1 will be
removed within the next few years. Null encryption is available, and should only be used for testing
or benchmarking purposes. Please do not request for insecure algorithms to be re-added to libreswan.
IKEv1 has been disabled per default, and will soon no longer be compiled in by default.
For all Diffie-Hellman groups, the "dh" keyword can be used instead of the "modp" keyword. For
example ike=3des-sha1;dh19. Diffie-Hellman groups 19,20 and 21 from RFC-5903 are supported.
Curve25519 from RFC-8031 is supported as "dh31". Curve448 and GOST DH groups are not yet supported in
libreswan because these are not supported yet in the NSS crypto library.
Diffie-Hellman groups 22, 23 and 24 from RFC-5114 are implemented but not compiled in by default.
These DH groups are extremely controversial and MUST NOT be used unless forced (administratively) by
the other party. This is further documented in RFC 8247, but the summary is that it cannot be proven
that these DH groups do not contain a cryptographic trapdoor (a backdoor by the USG who provided
these primes without revealing the seeds and generation process used).
The modp syntax will be removed in favour of the dh syntax in the future
phase2
Sets the type of SA that will be produced. Valid options are: esp for encryption (the default), ah
for authentication only.
The very first IPsec designs called for use of AH plus ESP to offer authentication, integrity and
confidentiality. That dual protocol use was a significant burden, so ESP was extended to offer all
three services, and AH remained as an auth/integ. The old mode of ah+esp is no longer supported in
compliance with RFC 8221 Section 4. Additionally, AH does not play well with NATs, so it is strongly
recommended to use ESP with the null cipher if you require unencrypted authenticated transport.
phase2alg
This option is alias to esp.
sha2-truncbug
The default ESP hash truncation for sha2_256 is 128 bits. Some IPsec implementations (Linux before
2.6.33, some Cisco (2811?) routers) implement the draft version which stated 96 bits. If a draft
implementation communicates with an RFC implementation, both ends will reject encrypted packets from
each other.
This option enables using the draft 96 bits version to interop with those implementations. Currently
the accepted values are no, (the default) signifying default RFC truncation of 128 bits, or yes,
signifying the draft 96 bits truncation.
Another workaround is to switch from sha2_256 to sha2_128 or sha2_512.
ms-dh-downgrade
Whether to allow a downgrade of DiffieHellman group during rekey (using CREATE_CHILD_SA). Microsoft
Windows (at the time of writing, Feb 2018) defaults to using the very weak modp1024 (DH2). This can
be changed using a Windows registry setting to use modp2048 (DH14). However, at rekey times, it will
shamelessly use modp1024 again and the connection might fail. Setting this option to yes (and adding
modp1024 proposals to the ike line) this will allow this downgrade attack to happen. This should only
be used to support Windows that feature this bug. Currently the accepted values are no, (the default)
or yes.
dns-match-id
Whether to perform an additional DNS lookup and confirm the remote ID payload with the DNS name in
the reverse DNS PTR record. Accepted values are no (the default) or yes. This check should be enabled
when Opportunistic IPsec is enabled in a mode that is based on packet triggers (on-demand) using
IPSECKEY records in DNS. Since in that case the IKE daemon pluto does not know the remote ID, it only
knows the remote IP address, this option forces it to confirm the peer's proposed ID (and thus its
public/private key) with its actual IP address as listed in the DNS. This prevents attacks where
mail.example.com's IP address is taken over by a neighbour machine with a valid web.example.com
setup. This check is not needed for certificate based Opportunistic IPsec, as "mail.example.com"s
certificate does not have an entry for "web.example.com". It is also not needed for DNS server
triggered Opportunistic IPsec, as in that case the IKE daemon pluto is informed of both the IP
address, and the hostname/public key.
require-id-on-certificate
When using certificates, check whether the IKE peer ID is present as a subjectAltName (SAN) on the
peer certificate. Accepted values are yes (the default) or no. This check should only be disabled
when intentionally using certificates that do not have their peer ID specified as a SAN on the
certificate. These certificates violate RFC 4945 Section 3.1 and are normally rejected to prevent a
compromised host from assuming the IKE identity of another host. The SAN limits the IDs that the peer
is able to assume.
ppk
EXPERIMENTAL: Post-quantum preshared keys (PPKs) to be used. Currently the accepted values are
propose or yes (the default), signifying we propose to use PPK for this connection; insist,
signifying we allow communication only if PPK is used for key derivation; never or no, signifying
that PPK should not be used for key derivation. PPKs can be used in connections that allow only
IKEv2. In libreswan that would mean that ikev2 option must have value insist. (currently based on
draft-fluhrer-qr-ikev2, not raft-ietf-ipsecme-qr-ikev2-00)
nat-ikev1-method
NAT Traversal in IKEv1 is negotiated via Vendor ID options as specified in RFC 3947. However, many
implementations only support the draft version of the RFC. Libreswan sends both the RFC and the most
common draft versions (02, 02_n and 03) to maximize interoperability. Unfortunately, there are known
broken implementations of RFC 3947, notably Cisco routers that have not been updated to the latest
firmware. As the NAT-T payload is sent in the very first packet of the initiator, there is no method
to auto-detect this problem and initiate a workaround.
This option allows fine tuning which of the NAT-T payloads to consider for sending and processing.
Currently the accepted values are drafts, rfc, both (the default) and none. To interoperate with
known broken devices, use nat-ikev1-method=drafts. To prevent the other end from triggering IKEv1
NAT-T encapsulation, set this to none. This will omit the NAT-T payloads used to determine NAT,
forcing the other end not to use encapsulation.
esp
Specifies the algorithms that will be offered/accepted when negotiating a a Child SA. The general
syntax is:
ESP = PROPOSAL[,PROPOSAL...]
PROPOSAL = ENCRYPT_ALGS[-INTEG_ALGS[-DH_ALGS]]
ENCRYPT_ALGS = ENCRYPT_ALG[+ENCRYPT_ALG...]
INTEG_ALGS = INTEG_ALG[+INTEG_ALG...]
DH_ALGS = DH_ALG[+DH_ALG...]
During startup, ipsec_pluto(8) will log all supported ESP algorithms.
Specifying the DH algorithms explicitly is not recommended. When PFS is enabled, and the DH
algorithms are omitted, each PROPOSAL will automatically include the DH algorithm negotiated during
the IKE exchange.
AEAD algorithms such as AES_GCM and AES_CCM no not require a separate integrity algorithm. For
example esp=aes_gcm256 or esp=aes_ccm.
For instance:
esp=aes_gcm,aes128+aes256-sha2_512+sha2_256-dh14+dh19
esp=aes128-sha2_512-dh14+dh19
If not specified, a secure set of defaults will be used. The program:
ipsec algparse esp=...
can be used to query these defaults.
ah
A comma separated list of AH algorithms that will be offered/accepted when negotiating the Child SA.
The general syntax is:
AH = PROPOSAL[,PROPOSAL...]
PROPOSAL = INTEG_ALGS[-DH_ALGS]
INTEG_ALGS = INTEG_ALG[+INTEG_ALG...]
DH_ALGS = DH_ALG[+DH_ALG...]
During startup, ipsec_pluto(8) will log all supported AH algorithms.
Specifying the DH algorithms explicitly is not recommended. When PFS is enabled, and the DH
algorithms are omitted, each PROPOSAL will automatically include the DH algorithm negotiated during
the IKE exchange.
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.
For instance:
ah=sha2_256+sha2_512
ah=sha2_256+sha2_512-dh14+dh19
If not specified, a secure set of defaults will be used. The program:
ipsec algparse ah=...
can be used to query these defaults.
fragmentation
Whether or not to allow IKE fragmentation. Valid values are yes, (the default), no or force.
IKEv1 fragmentation capabilities are negotiated via a well-known private vendor id. IKEv2
fragmentation support is implemented using RFC 7383. If pluto does not receive the fragmentation
payload, no IKE fragments will be sent, regardless of the fragmentation= setting. When set to yes,
IKE fragmentation will be attempted on the first re-transmit of an IKE packet of a size larger then
576 bytes for IPv4 and 1280 bytes for IPv6. If fragmentation is set to force, IKE fragmentation is
used on initial transmits of such sized packets as well. When we have received IKE fragments for a
connection, pluto behaves as if in force mode.
ikepad
Whether or not to pad IKEv1 messages to a multiple of 4 bytes. Valid values are yes, (the default)
and no.
IKE padding is allowed in IKEv1 but has been known to cause interoperability issues. The ikepad=
option can be used to disable IKEv1 padding. This used to be required for some devices (such as
Checkpoint in Aggressive Mode) that reject padded IKEv1 packets. A bug was fixed in libreswan 3.25
that applied wrong IKE padding in XAUTH, so it is suspected that Checkpoint padding issue bas been
resolved. And this option should not be needed by anyone. In IKEv2, no padding is allowed, and this
option has no effect. If you find a device that seems to require IKE padding, please contact the
libreswan developers. This option should almost never be enabled and might be removed in a future
version.
ikev2
Whether to use IKEv2 (RFC 7296) or IKEv1 (RFC 4301). Currently the accepted values are yes (the
default), signifying only IKEv2 is accepted, or no, signifying only IKEv1 is accepted. Previous
versions allowed the keywords propose or permit that would allow either IKEv1 or IKEv2, but this is
no longer supported. The permit option is interpreted as no and the propose option is interpreted as
yes. Older versions also supported keyword insist which is now interpreted as yes.
mobike
Whether to allow MOBIKE (RFC 4555) to enable a connection to migrate its endpoint without needing to
restart the connection from scratch. This is used on mobile devices that switch between wired,
wireless or mobile data connections. Current values are no (the default) or yes, Only connection
acting as modecfgclient will allow the initiator to migrate using mobike. Only connections acting as
modecfgserver will allow clients to migrate.
VTI and MOBIKE might not work well when used together.
esn
Whether or not to enable Extended Sequence Number (ESN) for the IPsec SA. This option is only
implemented for IKEv2. ESN is typically used for very high-speed links (10Gbps or faster) where the
standard 32 bit sequence number is exhausted too quickly, causing IPsec SA's rekeys to happen too
often. Accepted values are either (the default), yes and no. If either is specified as an initiator,
the responder will make the choice. As a responder, if either is received, yes is picked.
If replay-window is set to 0, ESN is disabled as some (most?) IPsec stacks won't support ESN in such
a configuration.
decap-dscp
Enable decapsulating the Differentiated Services Code Point (DSCP, formerly known as Terms Of Service
(TOS)) bits. If these bits are set on the inner (encrypted) IP packets, these bits are set on the
decrypted IP packets. Acceptable values are no (the default) or yes. Currently this feature is only
implemented for the Linux XFRM stack.
nopmtudisc
Disable Path MTU discovery for the IPsec SA. Acceptable values are no (the default) or yes. Currently
this feature is only implemented for the Linux XFRM stack.
narrowing
IKEv2 (RFC5996) Section 2.9 Traffic Selector narrowing options. Currently the accepted values are no,
(the default) signifying no narrowing will be proposed or accepted, or yes, signifying IKEv2
negotiation may allow establishing an IPsec connection with narrowed down traffic selectors. This
option is ignored for IKEv1.
There are security implications in allowing narrowing down the proposal. For one, what should be done
with packets that we hoped to tunnel, but cannot. Should these be dropped or send in the clear?
Second, this could cause thousands of narrowed down Child SAs to be created if the conn has a broad
policy (eg 0/0 to 0/0). One possible good use case scenario is that a remote end (that you fully
trust) allows you to define a 0/0 to them, while adjusting what traffic you route via them, and what
traffic remains outside the tunnel. However, it is always preferred to setup the exact tunnel policy
you want, as this will be much clearer to the user.
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 statsbin= notification helper.
nic-offload
Set the method of Network Interface Controller (NIC) hardware offload for ESP/AH packet processing.
Acceptable values are auto (the default), yes or no. This option is separate from any CPU hardware
offload available and is currently only available on Linux 4.13+ using the XFRM IPsec stack, when
compiled with the options CONFIG_XFRM_OFFLOAD, CONFIG_INET_ESP_OFFLOAD and CONFIG_INET6_ESP_OFFLOAD.
The auto option will attempt to auto-detect the presence of kernel and hardware support, and then
automatically mark the IPsec SA for hardware offloading. One vendor supporting this offload method is
Mellanox.
leftid
how the left participant should be identified for authentication; defaults to left. Can be an IP
address or a fully-qualified domain name which will be resolved. If preceded by @, the value is used
as a literal string and will not be resolved. To support opaque identifiers (usually of type
ID_KEY_ID, such as used by Cisco to specify Group Name, use square brackets, eg rightid=@[GroupName].
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.
When using certificate based ID's, one need to specify the full RDN, optionally using wildcard
matching (eg CN='*'). If the RDN contains a comma, this can be masked using a comma (eg OU='Foo,, Bar
and associates')
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.
leftcert
If you are using leftrsasigkey=%cert this defines the certificate nickname of your certificate in the
NSS database. This can be on software or hardware security device.
leftckaid
The hex CKAID of the X.509 certificate. Certificates are stored in the NSS database.
leftauth
How the security gateways will authenticate to the other side in the case of asymmetric
authentication; acceptable values are rsasig or rsa for RSA Authentication with SHA-1, rsa-sha2 for
RSA-PSS digital signatures based authentication with SHA2-256, rsa-sha2_384 for RSA-PSS digital
signatures based authentication with SHA2-384, rsa-sha2_512 for RSA-PSS digital signatures based
authentication with SHA2-512, ecdsa for ECDSA digital signatures based authentication, secret for
shared secrets (PSK) authentication and null for null-authentication. There is no default value - if
unset, the symmetrical authby= keyword is used to determine the authentication policy of the
connection.
Asymmetric authentication is only supported with IKEv2. If symmetric authentication is required, use
authby= instead of leftauth and rightauth. If leftauth is set, rightauth must also be set and authby=
must not be set. Asymmetric authentication cannot use secret (psk) on one side and null on the other
side - use psk on both ends instead.
When using EAPONLY authentication, which omits the regular IKEv2 AUTH payload, leftauth= (or
rightauth=) should be set to eaponly.
Be aware that the symmetric keyword is authby= but the asymmetric keyword is leftauth and rightauth
(without the "by").
leftautheap
Whether the security gateways will authenticate uing an EAP method. Acceptable values are none (the
default) and tls for EAPTLS. If EAP is the only authentication method, set leftauth=none in addition
to leftautheap=tls=.
The EAP authentication mechanisms are only available for IKEv2 based connections.
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.
leftikeport
The UDP IKE port to listen on or send data to. This port cannot be 0 or 500. For TCP, see
tcp-remoteport=
leftsendcert
This option configures when Libreswan will send X.509 certificates to the remote host. Acceptable
values are yes|always (signifying that we should always send a certificate), sendifasked (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 sendifasked 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).
leftusername
The username associated with this connection. The username can be the IKEv2 XAUTH username, a GSSAPI
username or IKEv2 CP username. For the XAUTH username, the XAUTH password can be configured in the
ipsec.secrets file. This option was previously called leftxauthusername.
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).
xauthby
When IKEv1 XAUTH support is available, set the method used by XAUTH to authenticate the user with
IKEv1. The currently supported values are file (the default), pam or alwaysok. The password file is
located at /etc/ipsec.d/passwd, and follows a syntax similar to the Apache htpasswd file, except an
additional connection name argument (and optional static IP address) are also present:
username:password:conname:ipaddress
For supported password hashing methods, see crypt(3). If pluto is running in FIPS mode, some hash
methods, such as MD5, might not be available. Threads are used to launch an xauth authentication
helper for file as well as PAM methods.
The alwaysok should only be used if the XAUTH user authentication is not really used, but is required
for interoperability, as it defeats the whole point of XAUTH which is to rely on a secret only known
by a human. See also pam-authorize=yes
xauthfail
When XAUTH support is available, set the failure method desired when authentication has failed. The
currently supported values are hard (the default) and soft. A soft failure means the IPsec SA is
allowed to be established, as if authentication had passed successfully, but the XAUTH_FAILED
environment variable will be set to 1 for the updown script, which can then be used to redirect the
user into a walled garden, for example a payment portal.
pam-authorize
IKEv1 supports PAM authorization via XAUTH using xauthby=pam. IKEv2 does not support receiving a
plaintext username and password. Libreswan does not yet support EAP authentication methods for IKE.
The pam-authorize=yes option performs an authorization call via PAM, but only includes the remote ID
(not username or password). This allows for backends to disallow an ID based on non-password
situations, such as "user disabled" or "user over quota". See also xauthby=pam
modecfgpull
Pull the Mode Config network information from the server. Acceptable values are yes or no (the
default).
modecfgdns, modecfgdomains, modecfgbanner
When configured as IKEv1 ModeCFG or IKEv2 server, specifying any of these options will cause those
options and values to be sent to the connecting client. Libreswan as a client will use these received
options to either update /etc/resolv.conf or the running unbound DNS server. When the connection is
brought down, the previous DNS resolving state is restored.
The modecfgdns option takes a comma or space separated list of IP addresses that can be used for DNS
resolution. The modecfgdomains option takes a comma or space separated list of internal domain names
that are reachable via the supplied modecfgdns DNS servers.
The IKEv1 split tunnel directive will be sent automatically if the xauth server side has configured a
network other than 0.0.0.0/0. For IKEv2, this is automated via narrowing.
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 libreswan to skip reconfiguring resolv.conf when used with
XAUTH and ModeConfig.
encapsulation
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. In other cases, where IKE
is NAT'ed but ESP packets can or should flow without encapsulation, it can be useful to ignore the
NAT-Traversal auto-detection. encapsulation=yes forces the NAT detection code to lie and tell the
remote peer that RFC-3948 encapsulation (ESP in port 4500 packets) is required. encapsulation=no
ignores the NAT detection causing ESP packets to send send without encapsulation. The default value
of encapsulation=auto follows the regular outcome of the NAT auto-detection code performed in IKE.
This option replaced the obsoleted forceencaps option.
enable-tcp
Normally, IKE negotiation and ESP encapsulation happens over UDP. This option enables support for IKE
and ESP over TCP as per RFC 8229. Acceptable values are no(the default), yes meaning only TCP will be
used, or fallback meaning that TCP will be attempted only after negotiation over UDP failed. Since
performance over TCP is much less, and TCP sessions are vulnerable to simply RST resets and MITM
attacks causing the TCP connection to close, this option should really only be used in fallback mode.
If used in fallback mode, it is recommend to reduce the retransmit-timeout from the default 60s to a
much shorter value such as 10s, so that one does not have to wait a minute for the TCP fallback to be
attempted.
tcp-remoteport
Which remote TCP port to use when IKE over TCP is attempted. The default value is to use the NAT-T
IKE port (4500). This value is not negotiated and should be configured properly on all endpoints.
When opening a TCP socket to the remote host in this port, a regular ephemeral source port is
obtained from the OS. For changing the UDP ports, see leftikeport=
nat-keepalive
whether to send any NAT-T keep-alives. These one byte packets 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
(the default) and no.
initial-contact
whether to send an INITIAL_CONTACT payload to the peer we are initiating to, if we currently have no
IPsec SAs up with that peer. Acceptable values are: yes (the default) and no. It is recommended to
leave this option set, unless multiple clients with the same identity are expected to connect using
the same subnets and should operate at the same time. Or if a reconnecting client should not delete
its old instance (eg perhaps it is still running). This is unlikely to be true.
cisco-unity
whether to send a CISCO_UNITY payload to the peer. Acceptable values are: no (the default) and yes.
It is recommended to leave this option unset, unless the remote peer (Cisco client or server)
requires it. This option does not modify local behaviour. It can be needed to connect as a client to
a Cisco server. It can also be needed to act as a server for a Cisco client, which otherwise might
send back an error DEL_REASON_NON_UNITY_PEER.
ignore-peer-dns
whether to ignore received DNS configuration. Acceptable values are: no (the default) and yes.
Normally, when a roadwarrior connects to a remote VPN, the remote VPN server sends a list of DNS
domains and DNS nameserver IP addresses that the roadwarrior can use to reach internal only resources
through the VPN. This option allows the roadwarrior to ignore the server's suggestion. The
roadwarrior will normally use this information to update the DNS resolving process. What is changed
depends on the detected DNS configuration. It can modify /etc/resolv.conf directly, or reconfigure a
locally running DNS server (unbound, knot, stubby or systemd-resolved) or inform NetworkManager.
accept-redirect
Whether requests of the remote peer to redirect IKE/IPsec SA's are accepted. Valid options are no
(the default) and yes. See also accept-redirect-to.
accept-redirect-to
Specify the comma separated list of addresses we accept being redirected to. Both IPv4 and IPv6
addresses are supported as well the FQDNs. The value %any, as well as not specifying any address,
signifes that we will redirect to any address gateway sends us in REDIRECT notify payload.
The value of this option is not considered at all if accept-redirect is set to no.
send-redirect
Whether to send requests for the remote peer to redirect IKE/IPsec SA's during IKE_AUTH. Valid
options are no (the default) and yes. If set, the option redirect-to= must also be set to indicate
where to redirect peers to. For redirection during IKE_SA_INIT exchange, see the global-redirect= and
global-redirect-to= options. Runtime redirects can be triggered via the ipsec whack --redirect
command.
redirect-to
Where to send remote peers to via the send-redirect option. This can be an IP address or hostname
(FQDN).
fake-strongswan
whether to send a STRONGSWAN Vendor ID payload to the peer. Acceptable values are: no (the default)
and yes. This used to be required because strongswan rejects certain proposals with private use
numbers such as esp=twofish or esp=serpent unless it receives a strongswan vendorid by the peer. This
option sends such an (unversioned) vendor id. Note that libreswan and strongswan no longer support
twofish or serpent, so enabling this option likely will no longer do anything.
send-vendorid
whether to send our Vendor ID during IKE. Acceptable values are: no (the default) and yes. The vendor
id sent can be configured using the "config setup" option myvendorid=. It defaults to
OE-Libreswan-VERSION.
Vendor ID's can be useful in tracking interoperability problems. However, specific vendor
identification and software versions can be useful to an attacker when there are known
vulnerabilities to a specific vendor/version.
The prefix OE stands for "Opportunistic Encryption". This prefix was historically used by The
FreeS/WAN Project and The Openswan Project (openswan up to version 2.6.38) and in one Xeleranized
openswan versions (2.6.39). Further Xeleranized openswan's use the prefix OSW.
overlapip
a boolean (yes/no) that determines, when (left|right)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.
reqid
a unique identifier used to match IPsec SAs using iptables with XFRM. This identifier is normally
automatically allocated in groups of 4. It is exported to the _updown script as REQID. On Linux,
reqids are supported with IP Connection Tracking and NAT (iptables). Automatically generated values
use the range 16380 and higher. Manually specified reqid values therefore must be between 1 and
16379.
Automatically generated reqids use a range of 0-3 (eg 16380-16383 for the first reqid). These are
used depending on the exact policy (AH, AH+ESP, IPCOMP, etc).
WARNING: Manually assigned reqids are all identical. Instantiations of connections (those using %any
wildcards) will all use the same reqid. If you use manual assigning you should make sure your
connections only match single road warrior only or you break multiple road warriors behind same NAT
router because this feature requires unique reqids to work.
dpddelay
Set the delay (in time units, defaults to seconds) between Dead Peer Detection (IKEv1 RFC 3706) or
IKEv2 Liveness keepalives that are sent for this connection (default 0 seconds). Set to enable
checking. If dpddelay is set, dpdtimeout also needs to be set.
dpdtimeout
Set the length of time (in time units, defaults to seconds) that we will idle without hearing back
from our peer. After this period has elapsed with no response and no traffic, we will declare the
peer dead, and remove the SA (default 0 seconds). Set value bigger than dpddelay to enable. If
dpdtimeout is set, dpddelay 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 that ALL SAs to the dead peer will renegotiated.
dpdaction=clear is really only useful on the server of a Road Warrior config.
The value restart_by_peer has been obsoleted and its functionality moved into the regular restart
action.
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.
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
aggressive
Use IKEv1 Aggressive Mode instead of IKEv1 Main Mode. This option has no effect when IKEv2 is used.
Acceptable values are no (the default) or yes. When this option is enabled, IKEv1 Main Mode will no
longer be allowed for this connection. The old name of this option was aggrmode.
Aggressive Mode is less secure, and more 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. Therefore it is mandatory for Aggressive Mode connections that both ike= and
phase2alg= options are specified with only one fully specified proposal using one DH group.
The KE payload is created in the first exchange packet when using aggressive mode. The KE payload
depends on the DH group used. This is why there cannot be multiple DH groups in IKEv1 aggressive
mode. In IKEv2, which uses a similar method to IKEv1 Aggressive Mode, there is an INVALID_KE response
payload that can inform the initiator of the responder's desired DH group 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 obsoleted aliases for "salifetime." Change your configs to
use "salifetime" instead.
ipsec-max-bytes
how many bytes can be sent, or how many bytes can be received on an IPsec SA instance for a
connection; acceptable values are an integer optionally followed by KiB, MiB, GiB, TiB, PiB or EiB to
signify kilobytes, megabytes, gigabytes, terabytes, petabytes or exabytes.
An IPsec SA contains two keys, one for inbound and one for outbound traffic. The ipsec-max-bytes sets
two limits on each of these keys: the hard limit which is the total number of bytes that a given key
can encrypt, and the soft limit which is the number of bytes that can be encrypted before a
renegotiation of the IPsec SA is initiated. Normally the renegotiation (via the IKE SA) is completed
before the ipsec-max-bytes value is reached.
Pluto sets the the original initiator's soft limit to 25% of ipsec-max-bytes (with 12% fuzz) and on
the original responder's soft limit to 50% of ipsec-max-bytes (with 12% fuzz). This way the original
initiator hopefully is the one initiating the renegotiation of the IPsec SA.
This option is not negotiated between IKE peers. Each end of the IPsec SA sets their own limits
independently.
The default (hard limit) is 2^63 bytes. The original initiator's soft limit is 2^61 bytes (approx.)
and the original responder's soft limit is 2^62 bytes (approx.).
ipsec-max-packets
how many packets can be sent/received on a particular instance of a connection (a set of
encryption/authentication keys for user packets) , from successful negotiation to expiry.
Default values and caveats are the same as for ipsec-max-bytes. This option uses a prefix without "B"
for bytes.
replay-window
The size of the IPsec SA replay window protection in packets. Kernels (Linux, and most BSDs) support
a window size of at least 2040 packets. The default replay window size is 128 packets.
A value of 0 disables replay protection. Disabling of replay protection is sometimes used on a pair
of IPsec servers in a High Availability setup, or on servers with very unpredictable latency, such as
mobile networks, which can cause an excessive amount of out of order packets.
Disabling replay protection will also disable Extended Sequence Numbers (esn=no), as advise from RFC
4303 caused some stacks to not support ESN without a replay-window.
Note: on Linux, sequence errors can be seen in /proc/net/xfrm_stat.
Note: the BSD setkey utility displays the replay window size in bytes (8 packets per byte) and not
packets.
Technically, at least the Linux kernel can install IPsec SA's with an IPsec SA Sequence Number, but
this is currently not supported by libreswan.
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 or 0 means to keep
trying forever. For Opportunistic Encryption connections, a keyingtries value of %forever or 0 is set
to 1 and a warning message will be logged. This is because an expired failureshunt triggers new
keyingtries on-demand later, when there is traffic. This prevents accumulating an infinite amount of
attempts to peers that do not support Opportunistic Encryption. For Opportunistic, a keyingtries
value of > 1 is allowed but currently not recommended. The meaning of failureshunt= is unclear when
there is continued (failed) keying happening with a negotiationshunt installed. Relevant only
locally, other end need not agree on it.
ikelifetime
how long the keying channel of a connection (buzzphrase: “IKE SA” or “Parent SA”) should last before
being renegotiated; acceptable values as for salifetime. The default as of version 4.2 is 8h, before
that it was 1h. The maximum is 24h. The two-ends-disagree case is similar to that of salifetime.
retransmit-timeout
how long a single packet, including retransmits of that packet, may take before the IKE attempt is
aborted. If rekeying is enabled, a new IKE attempt is started. The default set by ipsec_pluto(8),
currently is 60s. See also: retransmit-interval, rekey and keyingtries.
retransmit-interval
the initial interval time period, specified in msecs, that pluto waits before retransmitting an IKE
packet. This interval is doubled for each attempt (exponential back-off). The default set by
ipsec_pluto(8), currently is 500. See also: retransmit-timeout, rekey and keyingtries.
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).
For IKEv1, compress settings on both peers must match. For IKEv2, compression can only be suggested
and a mismatched compress setting results in connection without compression.
When set to yes, compression is negotiated for the DEFLATE compression algorithm.
metric
Set the metric for added routes. This value is passed to the _updown scripts as PLUTO_METRIC.
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 encapsulation 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.
tfc
Enable Traffic Flow Confidentiality ("TFC") (RFC-4303) for outgoing ESP packets in Tunnel Mode. When
enabled, ESP packets are padded to the specified size (up to the PMTU size) to prevent leaking
information based on ESP packet size. This option is ignored for AH and for ESP in Transport Mode as
those always leak traffic characteristics and applying TFC will not do anything. Acceptable values
are positive numbers. The value 0 means TFC padding is not performed. Currently this feature is only
implemented for the Linux XFRM stack. In IKEv2, when the notify payload ESP_TFC_PADDING_NOT_SUPPORTED
is received, TFC padding is disabled. The default is not to do any TFC padding, but this might change
in the near future.
send-no-esp-tfc
Whether or not to tell the remote peer that we do not support Traffic Flow Confidentiality ("TFC")
(RFC-4303). Possible values are no (the default) which allows the peer to use TFC or yes which
prevents to peer from using TFC. This does not affect whether this endpoint uses TFC, which only
depends on the local tfc setting. This option is only valid for IKEv2.
nflog
If set, the NFLOG group number to log this connection's pre-crypt and post-decrypt traffic to. The
default value of 0 means no logging at all. This option is only available on linux kernel 2.6.14 and
later. It allows common network utilities such as tcpdump, wireshark and dumpcap, to use nflog:XXX
pseudo interfaces where XXX is the nflog group number. During the updown phase of a connection,
iptables will be used to add and remove the source/destination pair to the nflog group specified. The
rules are setup with the nflog-prefix matching the connection name. See also the global nflog-all
option.
mark
If set, the MARK to set for the IPsec SA of this connection. The format of a CONNMARK is mark/mask.
If the mask is left out, a default mask of 0xffffffff is used. A mark value of -1 means to assign a
new global unique mark number for each instance of the connection. Global marks start at 1001. This
option is only available on linux XFRM kernels. It can be used with iptables to create custom
iptables rules using CONNMARK. It can also be used with Virtual Tunnel Interfaces ("VTI") to direct
marked traffic to specific vtiXX devices.
mark-in
The same as mark, but mark-in only applies to the inbound half of the IPsec SA. It overrides any
mark= setting.
mark-out
The same as mark, but mark-out only applies to the outbound half of the IPsec SA. It overrides any
mark= setting.
vti-interface
This option is used to create "Routing based VPNs" (as opposed to "Policy based VPNs"). It will
create a new interface that can be used to route traffic in for encryption/decryption. The Virtual
Tunnel Interface ("VTI") interface name is used to for all IPsec SA's created by this connection.
This requires that the connection also enables either the mark= or mark-in= / mark-out- option(s).
All traffic marked with the proper MARKs will be automatically encrypted if there is an IPsec SA
policy covering the source/destination traffic. Tools such as tcpdump and iptables can be used on all
cleartext pre-encrypt and post-decrypt traffic on the device. See the libreswan wiki for example
configurations that use VTI.
VTI interfaces are currently only supported on Linux with XFRM. The _updown script handles certain
Linux specific interfaces settings required for proper functioning (disable_policy, rp_filter,
forwarding, etc). Interface names are limited to 16 characters and may not allow all characters to be
used. If marking and vti-routing=yes is used, no manual iptables should be required. However,
administrators can use the iptables mangle table to mark traffic manually if desired.
vti-routing
Whether or not to add network rules or routes for IPsec SA's to the respective VTI devices. Valid
values are yes (the default) or no. When using "routing based VPNs" with a subnets policy of
0.0.0.0/0, this setting needs to set to no to prevent imploding the tunnel, and the administrator is
expected to manually add ip rules and ip routes to configure what traffic must be encrypted. When set
to yes, the _updown script will automatically route the leftsubnet/rightsubnet traffic into the VTI
device specified with vti-interface
vti-shared
Whether or not the VTI device is shared amongst connections. Valid values are no (the default) or
yes. When set to no, the VTI device is automatically deleted if the connection is a single
non-instantiated connection. If a connection instantiates (eg right=%any) then this option has no
effect, as the VTI device is not removed as it is shared with multiple roadwarriors.
ipsec-interface
Create or use an existing virtual interface ipsecXXX for "Routing based VPNs" (as opposed to "Policy
based VPNs"). Valid options are yes, no or a number. When using a number, the IPsec interface created
and/or used will use that number as part of the interface name. For example setting ipsec-interface=5
will create and/or use the ipsec5 interface. The value 0 cannot be used and is interpreted as no. The
value yes is interpreted as the number 1, and thus will use the interface named ipsec1. An IP address
can be configured for this interface via the interface-ip= option.
The ipsec-interface is used to route outbound traffic that needs to be encrypted, and will decrypt
inbound traffic that arrives on this interface. All traffic that is routed to this interface will be
automatically encrypted providing the IPsec SA policy covers this traffic. Traffic not matching the
IPsec SA will be dropped. Tools such as tcpdump, iptables, ifconfig and tools that need traffic
counters can be used on all cleartext pre-encrypt and post-decrypt traffic on the device. When
leftsubnet= is equal to rightsubnet=, the routing needs to be manged by an external routing daemon or
manually by the administrator.
This option is currently only supported on Linux kernels 4.19 or later when compiled with XFRMi
support (CONFIG_XFRM_INTERFACE). The number of the ipsecX device corresponds with the XFRM IF_ID
policy option of the IPsec SA in the Linux kernel. On Linux, XFRMi interfaces can be managed by
libreswan automatically or can be preconfigured on the system using the existing init system or via
networking tools such as systemd-networkd and NetworkManager. The _updown script handles certain
Linux specific interfaces settings required for proper functioning, such as forwarding and routing
rules for IPsec traffic.
The ipsec-interface=0 will create an interface with the same name as the old KLIPS interface, ipsec0.
This interface name should only be used when required for migration from KLIPS to XFRM interfaces.
Since XFRM IF_ID and marking cannot use 0, this is mapped to 16384. This means that the devices
ipsec0 and ipsec16384 cannot both be in use.
interface-ip=
NOTE: This option is currently not implemented pending pluto IP address reference counting. The IP
address and netmask to configure on a virtual device (eg ipsecXXX). This is often used when building
Routing based IPsec tunnels using transport mode and GRE, but can also be useful in other scenarios.
Currently requires ipsec-interface=. See also leftvti= for cnofiguring IP addresses when using VTI.
priority
The priority in the kernel SPD/SAD database, when matching up packets. Each kernel (XFRM, OSX, etc)
has its own mechanism for setting the priority. Setting this option to non-zero passes the priority
to the kernel stack unmodified. The maximum value depends on the stack. It is recommended not to
exceed 65536
XFRM use a priority system based on "most specific match first". It uses an internal algorithm to
calculate these based on network prefix length, protocol and port selectors. A lower value means a
higher priority.
Typical values are about the 2000 range. These can be seen on the XFRM stack using ip xfrm policy
when the connection is up. For "anonymous IPsec" or Opportunistic Encryption based connections, a
much lower priority (65535) is used to ensure administrator configured IPsec always takes precedence
over opportunistic IPsec.
sendca
How much of our available X.509 trust chain to send with the End certificate, excluding any root
CA's. Specifying issuer sends just the issuing intermediate CA, while
all will send the entire chain of intermediate CA's.none (the default) will not send any CA certs.
labeled-ipsec
This option is obsolete. To enable labeled IPsec, setting the policy-label= is enough. See also
policy-label= and secctx-attr-type=
policy-label
The string representation of an access control security label that is interpreted by the LSM (e.g.
SELinux) for use with Labeled IPsec. See also labeled-ipsec= and secctx-attr-type=. For example,
policy-label=system_u:object_r:ipsec_spd_t:s0-s15:c0.c1023
failureshunt
what to do with packets when negotiation fails. The default is none: no shunt; passthrough, drop, and
reject have the obvious meanings.
negotiationshunt
What to do with packets during the IKE negotiation. Valid options are hold (the default) or
passthrough. This should almost always be left to the default hold value to avoid cleartext packet
leaking. The only reason to set this to passthrough is if plaintext service availability is more
important than service security or privacy, a scenario that also implies failureshunt=passthrough and
most likely authby=%null using Opportunistic Encryption.
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
logfile=/var/log/pluto.log
plutodebug=all
Parameters are optional unless marked “(required)”.
The currently-accepted parameter names in a config setup section are:
protostack
decide which protocol stack is going to be used. Valid values are "xfrm" and "bsd". This option
should no longer be set, as the stack is currently auto-detected. The values "klips, "mast",
"netkey", "native", "kame" and "auto" are obsolete. The option is kept only because it is suspected
that Linux and BSD will get userspace stacks with IPsec support soon (such as dpdk).
listen
IP address to listen on, defaults to ANY. Currently only accepts one IP address.
ike-socket-bufsize
Set the IKE socket buffer size. Default size is determined by the OS (as of writing, this seems to be
set to 212992. On Linux this is visible via /proc/sys/net/core/rmem_default and
/proc/sys/net/core/wmem_default. On Linux, this option uses SO_RCVBUFFORCE and SO_SNDBUFFORCE so that
it can override rmem_max/wmem_max values of the OS. This requires CAP_NET_ADMIN (which is also
required for other tasks). This option can also be toggled on a running system using ipsec whack
--ike-socket-bufsize bufsize.
ike-socket-errqueue
Whether to enable or disable receiving socket errors via IP_RECVERR. The default is enabled. This
will cause the socket to receive, process and log socket errors, such as ICMP unreachable messages or
Connection Refused messages. Disabling this only makes sense on very busy servers, and even then it
might not make much of a difference. This option can also be toggled on a running system using ipsec
whack --ike-socket-errqueue-toggle.
listen-udp
Whether the pluto IKE daemon should listen on the standard UDP ports of 500 and 4500. The value "yes"
means to listen on these ports, and is the default. This should almost never be disabled. In the rare
case where it is known that only ever TCP or non-standard UDP ports will be used, this option can
disable the standard UDP ports. Connections can specify their own non-standard port using
leftikeport=.
listen-tcp
Whether the pluto IKE daemon should listen on the (pseudo) standard TCP port 4500. The value "no" is
the current default, but this will be changed in the future to "yes". The TCP usage complies to RFC
8229 for IKE and ESP over TCP support. Connections can specify their own non-standard port using
leftikeport=.
nflog-all
If set, the NFLOG group number to log all pre-crypt and post-decrypt traffic to. The default value of
0 means no logging at all. This option is only available on linux kernel 2.6.14 and later. It allows
common network utilities such as tcpdump, wireshark and dumpcap, to use nflog:XXX pseudo interfaces
where XXX is the nflog group number. During startup and shutdown of the IPsec service, iptables
commands will be used to add or remove the global NFLOG table rules. The rules are setup with the
nflog-prefix all-ipsec. See also the per-connection nflog option.
keep-alive
The delay (in seconds) for NAT-T keep-alive packets, if these are enabled using nat-keepalive This
parameter may eventually become per-connection.
virtual-private
contains the networks that are allowed as (left|right)subnet= for the remote clients when using the
vhost: or vnet: keywords in the (left|right)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 belongs 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 organisations "borrowed"
this range. To support roadwarriors on these 3G networks, you might have to add it to the
virtual-private= line.
myvendorid
The string to use as our vendor id (VID) when send-vendorid=yes. The default is OE-Libreswan-VERSION.
nhelpers
how many pluto helpers are started to help with cryptographic operations. Pluto will start as many
helpers as the number of CPU's, minus 1 to dedicate to the main thread. For machines with less than 4
CPU's, an equal number of helpers to CPU's are started. A value of 0 forces pluto to do all
operations inline using the main process. A value of -1 tells pluto to perform the above calculation.
Any other value forces the number to that amount.
seedbits
Pluto uses the NSS crypto library as its random source. Some government Three Letter Agencies require
that pluto reads additional bits from /dev/random and feed these into the NSS RNG before drawing
random from the NSS library, despite the NSS library itself already seeding its internal state. This
process can block pluto for an extended time during startup, depending on the entropy of the system.
Therefore, the default is to not perform this redundant seeding. If specifying a value, it is
recommended to specify at least 460 bits (for FIPS) or 440 bits (for BSI).
ikev1-secctx-attr-type
The value for the IKEv1 IPsec SA security context attribute identifier that is used for Labeled
IPsec. Defaults to the private use IANA value 32001 from the IPsec SA attributes registry. Old
openswan versions might still be using the (stolen) value 10, which has since been assigned by IANA
for something else. Other values are not recommended unless IANA assigns an actual value for this
option. Labeled IPsec using IKEv2 does not use this option, it only uses an IANA allocated Notify
number. See also policy-label.
ikev1-policy
What to do with received IKEv1 packets. Valid options are drop (default) which will silently drop any
received IKEv1 packet, accept, and reject which will reply with an error. If this option is set to
drop or reject, an attempt to load an IKEv1 connection will fail, as these connections would never be
able to receive a packet for processing.
crlcheckinterval
interval expressed in second units, for example crlcheckinterval=8h for 8 hours, after which pluto
will fetch new Certificate Revocation List (CRL) from crl distribution points. List of used CRL
distribution points are collected from CA certificates and end certificates. Loaded X.509 CRL's are
verified to be valid and updates are imported to NSS database. If set to 0, which is also the default
value if this option is not specified, CRL updating is disabled.
crl-strict
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 vulnerable to downtime if the CRL expires.
Acceptable values are yes or no (the default). This option used to be called strictcrlpolicy.
curl-iface
The name of the interface that is used for CURL lookups. This is needed on rare situations where the
interface needs to be forced to be different from the default interface used based on the routing
table.
curl-timeout
The timeout for the curl library calls used to fetch CRL and OCSP requests. The default is 5s.
ocsp-enable
Whether to perform Online Certificate Store Protocol ("OCSP") checks on those certificates that have
an OCSP URI defined. Acceptable values are yes or no (the default).
ocsp-strict
if set to no, pluto is tolerant about failing to obtain an OCSP responses and a certificate is not
rejected when the OCSP request fails, only when the OCSP request succeeds and lists the certificate
as revoked. If set to yes, any failure on obtaining an OCSP status for a certificate will be fatal
and the certificate will be rejected. Acceptable values are yes or no (the default).
The strict mode refers to the NSS ocspMode_FailureIsVerificationFailure mode, while non-strict mode
refers to the NSS ocspMode_FailureIsNotAVerificationFailure mode.
ocsp-method
The HTTP methods used for fetching OCSP data. Valid options are get (the default) and post. Note that
this behaviour depends on the NSS crypto library that is actually performing the fetching. When set
to the get method, post is attempted only as fallback in case of failure. When set to post, only the
post method is ever used.
ocsp-timeout
The time until an OCSP request is aborted and considered failed. The default value is 2 seconds.
ocsp-uri
The URI to use for OCSP requests instead of the default OCSP URI listed in the CA certificate. This
requires the ocsp-trustname option to be set to the nick (friendly name) of the OCSP server
certificate, which needs to be present in the NSS database. These option combined with the next
option sets the OCSP default responder.
ocsp-trustname
The nickname of the certificate that has been imported into the NSS database of the server handling
the OCSP requests. This requires the ocsp-uri option to be set as well. This option and the previous
options sets the OCSP default responder.
ocsp-cache-size
The maximum size (in number of certificates) of OCSP responses that will be kept in the cache. The
default is 1000. Setting this value to 0 means the cache is disabled.
ocsp-cache-min-age
The minimum age (in seconds) before a new fetch will be attempted. The default is 1 hour.
ocsp-cache-max-age
The maximum age (in seconds) before a new fetch will be attempted. The default is 1 day.
syslog
the syslog(2) “facility” name and priority to use for startup/shutdown log messages, default
daemon.error.
plutodebug
how much Pluto debugging output should be logged. An empty value, or the magic value none, means no
debug output (the default). Otherwise only the specified types of output (a quoted list, names
without the --debug- prefix, separated by white space) are enabled;
The current option values are base that represents moderate amounts of information, cpu-usage for
getting timing/load based information (best used without any other debugging options), crypt for all
crypto related operations and tmi (Too Much Information) for excessive logging. To log any sensitive
private key or password material, use the special private value.
The old plutodebug options (control, controlmore, x509, kernel, etc) are mapped to either base or
tmi. Note that all maps to base and not tmi.
uniqueids
Whether IDs should be considered identifying remote parties uniquely. Acceptable values are yes (the
default) and no. Participant IDs normally are unique, so a new connection instance using the same
remote ID is almost invariably intended to replace an old existing connection.
When the connection is defined to be a server (using xauthserver=) and the connection policy is
authby=secret, this option is ignored (as of 3.20) and old connections will never be replaced. This
situation is commonly known as clients using a "Group ID".
This option may disappear in the near future. People using identical X.509 certificates on multiple
devices are urged to upgrade to use separate certificates per client and device.
logfile
do not use syslog, but rather log to stderr, and direct stderr to the argument file. This option used
to be called plutostderrlog=
logappend
If pluto is instructed to log to a file using logfile=, this option determines whether the log file
should be appended to or overwritten. Valid options are yes (the default) to append and no to
overwrite. Since on modern systems, pluto is restarted by other daemons, such as systemd, this option
should be left at its default yes value to preserve the log entries of previous runs of pluto. The
option is mainly of use for running the test suite, which needs to create new log files from scratch.
logip
If pluto is instructed to log the IP address of incoming connections. Valid options are yes (the
default) and no. Note that this only affects regular logging. Any enabled debugging via plutodebug=
will still contain IP addresses of peers. This option is mostly meant for servers that want to avoid
logging IP addresses of incoming clients. Other identifiable information might still be logged, such
as ID payloads and X.509 certificate details. When using ID of type IP address, this option will not
hide the actual IP address as part of the ID. Most deployments will not want to change this from the
default. If logging of IP addresses is unwanted, audit-log=no should also be set.
audit-log
Whether pluto should produce Linux Auditing System log messages. If enabled, pluto will log start,
stop and fail for the negotiation of IKE and IPsec SA's. The kernel will also log success and
failures for actually adding and removing IPsec SA's from the kernel's SADB. Valid options are
yes(the default) and no. On non-Linux systems, this option is ignored. If enabled but the kernel is
lacking audit support, audit messages are not sent. If the kernel has audit support and using it
fails, pluto will abort. Note that for compliance reasons, audit log messages contain the relevant IP
addresses, even if logip=no.
logtime
When pluto is directed to log to a file using logfile=, this option determines whether or not to log
the current timestamp as prefix. Values are yes (the default) or no. The no value can be used to
create logs without ephemeral timestamps, such as those created when running the test suite. This
option used to be called plutostderrlogtime=
ddos-mode
The startup mode of the DDoS defense mechanism. Acceptable values are busy, unlimited or auto (the
default). This option can also be given to the IKE daemon while running, for example by issuing ipsec
whack --ddos--busy. When in busy mode, pluto activates anti-DDoS counter measures. Currently, counter
measures consist of requiring IKEv2 anti-DDoS cookies on new incoming IKE requests, and a more
aggressive cleanup of partially established or AUTH_NULL connections.
ddos-ike-threshold
The number of half-open IKE SAs before the pluto IKE daemon will be placed in busy mode. When in busy
mode, pluto activates anti-DDoS counter measures. The default is 25000. See also ddos-mode and ipsec
whack --ddos-XXX.
global-redirect
Whether to send requests for the remote peer to redirect IKE/IPsec SA's during IKE_SA_INIT. Valid
options are no (the default), yes and auto, where auto means that the requests will be sent if DDoS
mode is active (see ddos-mode). If set, the option global-redirect-to= must also be set to indicate
where to redirect peers to. For specific connection redirection after IKE SA authentication, see the
send-redirect= and redirect-to= options. This configuration can be changed at runtime via the ipsec
whack --global-redirect command.
global-redirect-to
Where to send remote peers to via the global-redirect option. This can be a list, or a single entry,
of IP addresses or hostnames (FQDNs). If there is a list of entries, they must be separated with
comma's. One specified entry means all peers will be redirected to it, while multiple specified
entries means peers will be evenly distributed across the specified servers. This configuration can
be changed at runtime via the ipsec whack --global-redirect-to command.
max-halfopen-ike
The number of half-open IKE SAs before the IKE daemon starts refusing all new IKE attempts.
Established IKE peers are not affected. The default value is 50000.
shuntlifetime
The time until bare shunts (kernel policies not associated with connections) are deleted from the
kernel. The default value is 15m. When using Opportunistic Encryption to a specific host fails, the
system will either install a %pass or %hold shunt to let the traffic out clear text or block it.
During the the shuntlifetime, no new Opportunistic Encryption attempt will be started, although the
system will still respond to incoming OE requests from the remote IP. See also failureshunt and
negotiationshunt
xfrmlifetime
The time in seconds until the XFRM acquire state times out. The default value is 30 seconds. For
auto=ondemand connections and Opportunistic connections an IPsec policy is installed in the kernel.
If an incoming or outgoing packet matches this policy, a state is created in the kernel and the
kernel sends an ACQUIRE message to the IKE daemon pluto. While this state is in place, no new
acquires will come in for this connection. The default should be fine for most people. One use case
of shortening these is if opportunistc encryption is used towards cloud instances that can quickly
re-use IP addresses. This value is only used during the libreswan startup process by the ipsec
_stackmanager helper. See also failureshunt and negotiationshunt
dumpdir
in what directory should things started by setup (notably the Pluto daemon) be allowed to dump core?
The default value is /var/run/pluto. When SELinux runs in enforced mode, changing this requires a
similar change in the SELinux policy for the pluto daemon.
statsbin
This option specifies an optional external program to report tunnel state changes too. The default is
not to report tunnel state changes. This program can be used to notify the user's desktop (dbus,
NetworkManager) or to report tunnel changes to a central logging server.
ipsecdir
Specifies a directory for administrator-controlled configuration files and directories. The default
value is /etc/ipsec.d. It may contain the following files and directories:
passwd
(optional) for XAUTH support if not using PAM (this file should not be world-readable). See
README.XAUTH for more information.
nsspassword
(optional) passwords needed to unlock the NSS database in /var/lib/ipsec/nss (this file should
not be world-readable). See README.nss for more information.
policies/
a directory containing policy group configuration information. See POLICY GROUP FILES in this
document for more information.
cacerts/
DEPRECATED: a directory to store trust anchors (root certificate authority certificates). The
preferred (and default) approach is to store CA certs in the NSS database instead. See README.nss
for more information.
crls/
DEPRECATED: a directory to store certificate revocation lists. The preferred (and default)
approach is to store CRLs in the NSS database instead. See README.nss for more information.
When SELinux runs in enforced mode, changing this requires a similar change in the SELinux policy for
the pluto daemon.
nssdir
Specifies a directory for NSS database files. The default value is /var/lib/ipsec/nss. It may contain
the following files:
pkcs11.txt
Detailed info about NSS database creation parameteres.
cert9.db
NSS Certificate database.
key4.db
NSS Key database.
When SELinux runs in enforced mode, changing this requires a similar change in the SELinux policy for
the pluto daemon.
secretsfile
pathname of the file that stores the secret credentials such as preshared keys (PSKs). See man
ipsec.secrets for the syntax. The default value is /etc/ipsec.secrets.
seccomp
Set the seccomp kernel syscall whitelisting feature. When set to enabled, if pluto calls a syscall
that is not on the compiled-in whitelist, the kernel will assume an exploit is attempting to use
pluto for malicious access to the system and terminate the pluto daemon. When set to tolerant, the
kernel will only block the rogue syscall and pluto will attempt to continue. If set to disabled,
pluto is allowed to call any syscall offered by the kernel, although it might be restricted via other
security mechanisms, such as capabilities, SElinux, AppArmor or other OS security features.
The current default is disabled, but it is expected that in the future this feature will be enabled
on all supported operating systems. Similarly, it is expected that further privilege separation will
reduce the allowed syscalls - for example for the crypto helpers or DNS helpers.
Warning: The restrictions of pluto are inherited by the updown scripts, so these scripts are also not
allowed to use syscalls that are forbidden for pluto.
This feature can be tested using ipsec whack --seccomp-crashtest. Warning: With seccomp=enabled,
pluto will be terminated by the kernel. With seccomp=tolerant or seccomp=disabled, pluto will report
the results of the seccomp test. SECCOMP will log the forbidden syscall numbers to the audit log, but
only with seccomp=enabled. The tool scmp_sys_resolver from the libseccomp development package can be
used to translate the syscall number into a name. See programs/pluto/pluto_seccomp.c for the list of
allowed syscalls.
dnssec-enable
Whether pluto should perform dnssec validation using libunbound, provided libreswan was compiled with
USE_DNSSEC. A value of yes (the default) means pluto should perform DNSSEC validation. Note that
pluto reads the file /etc/resolv.conf to determine which nameservers to use.
dnssec-rootkey-file
The location of the DNSSEC root zone public key file. The default is /var/lib/unbound/root.key but
this can be changed at compile time.
dnssec-anchors
The location of a file containing additional DNSSEC Trust Anchors. This can be used when a network is
using split-DNS and the internal hierarchy is using DNSSEC trust anchors. There is no default value.
OPPORTUNISTIC CONNS
For Opportunistic connections, the system requires creating special named conns that are used to
implement the default policy groups. Currently, these names cannot be changed.
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
These conns will only work if %defaultroute works. The leftid will be the interfaces IP address by
default, but it can also be set to %fromcert or use a DNS name.
POLICY GROUP FILES
The optional files under /etc/ipsec.d/policies, 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 that has right=%group or right=%opportunisticgroup is a policy group
connection. When a policy group file of the same name is loaded 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/policies/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 Libreswan 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.
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 that 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_auto(8), ipsec_rsasigkey(8)
HISTORY
Designed for the FreeS/WAN project <https://www.freeswan.org> by Henry Spencer.
BUGS
Before reporting new bugs, please ensure you are using the latest version of Libreswan.
When type or failureshunt is set to drop or reject, Libreswan blocks outbound packets using eroutes, but
assumes inbound blocking is handled by the firewall. Libreswan 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.
It would be good to have a line-continuation syntax, especially for the very long lines involved in RSA
signature keys.
The ability to specify different identities, authby, and public keys for different automatic-keyed
connections between the same participants is misleading; this doesn't work dependably because the
identity of the participants is not known early enough. This is especially awkward for the “Road Warrior”
case, where the remote IP address is specified as 0.0.0.0, and that is considered to be the “participant”
for such connections.
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.
AUTHOR
Paul Wouters
documenter
libreswan 03/31/2024 IPSEC.CONF(5)