Provided by: strongswan-starter_5.8.2-1ubuntu3.6_amd64 
NAME
ipsec.conf - IPsec configuration and connections
DESCRIPTION
The optional ipsec.conf file specifies most configuration and control information for the
strongSwan IPsec subsystem. The major exception is secrets for authentication; see
ipsec.secrets(5). Its contents are not security-sensitive.
The file is a text file, consisting of one or more sections. White space followed by #
followed by anything to the end of the line is a comment and is ignored, as are empty
lines which are not within a section.
A line which contains include and a file name, separated by white space, is replaced by
the contents of that file. If the file name is not a full pathname, it is considered to
be relative to the directory containing the including file. Such inclusions can be
nested. Only a single filename may be supplied, and it may not contain white space, but
it may include shell wildcards (see sh(1)); for example:
include ipsec.*.conf
The intention of the include facility is mostly to permit keeping information on
connections, or sets of connections, separate from the main configuration file. This
permits such connection descriptions to be changed, copied to the other security gateways
involved, etc., without having to constantly extract them from the configuration file and
then insert them back into it. Note also the also parameter (described below) which
permits splitting a single logical section (e.g. a connection description) into several
actual sections.
A section begins with a line of the form:
type name
where type indicates what type of section follows, and name is an arbitrary name which
distinguishes the section from others of the same type. All subsequent non-empty lines
which begin with white space are part of the section. Sections of the same type that
share the same name are merged.
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 are specific to a section type.
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. This may be useful to clear a
setting inherited from a %default section or via also parameter (see below). A value may
contain single spaces (additional white space is reduced to one space). To preserve white
space as written enclose the entire value in double quotes ("); in such values double
quotes themselves may be escaped by prefixing them with \ characters. A double-quoted
string may span multiple lines by ending them with \ characters (following lines don't
have to begin with white space, as that will be preserved). Additionally, the following
control characters may be encoded in double-quoted strings: \n, \r, \t, \b, \f.
Numeric values are specified to be either an ``integer'' (a sequence of digits) or a
``decimal number'' (sequence of digits optionally followed by `.' and another sequence of
digits).
There is currently one parameter which is available in any type of section:
also the value is a section name; the parameters of that section are inherited by the
current section. Parameters in the current section always override inherited
parameters, even if an also follows after them. The specified section must exist
and must have the same section type; it doesn't if it is defined before or after
the current section. Nesting is permitted, and there may be more than one also in
a single section (parameters from referenced sections are inherited and overridden
in the order of these also parameters).
A section with name %default specifies defaults for sections of the same type. All
parameters in it, are inherited by all other sections of that type.
Currently there are three types of sections: a config section specifies general
configuration information for IPsec, a conn section specifies an IPsec connection, while a
ca section specifies special properties of a certification authority.
CONN SECTIONS
A conn section contains a connection specification, defining a network connection to be
made using IPsec. The name given is arbitrary, and is used to identify the connection.
Here's a simple example:
conn snt
left=192.168.0.1
leftsubnet=10.1.0.0/16
right=192.168.0.2
rightsubnet=10.1.0.0/16
keyingtries=%forever
auto=add
A note on terminology: There are two kinds of communications going on: transmission of
user IP packets, and gateway-to-gateway negotiations for keying, rekeying, and general
control. The path to control the connection is called 'ISAKMP SA' in IKEv1 and 'IKE SA'
in the IKEv2 protocol. That what is being negotiated, the kernel level data path, is
called 'IPsec SA' or 'Child SA'. strongSwan previously used two separate keying daemons,
pluto and charon. This manual does not discuss pluto options anymore, but only charon that
since strongSwan 5.0 supports both IKEv1 and IKEv2.
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; for every connection description an attempt is made to figure out whether
the local endpoint should act as the left or right endpoint. This is done by matching the
IP addresses defined for both endpoints with the IP addresses assigned to local network
interfaces. If a match is found then the role (left or right) that matches is going to be
considered local. If no match is found during startup, left is considered local. This
permits using identical connection specifications on both ends. There are cases where
there is no symmetry; a good convention is to use left for the local side and right for
the remote side (the first letters are a good mnemonic).
Many of the parameters relate to one participant or the other; only the ones for left are
listed here, but every parameter whose name begins with left has a right counterpart,
whose description is the same but with left and right reversed.
Parameters are optional unless marked '(required)'.
CONN PARAMETERS
Unless otherwise noted, for a connection to work, in general it is necessary for the two
ends to agree exactly on the values of these parameters.
aaa_identity = <id>
defines the identity of the AAA backend used during IKEv2 EAP authentication. This
is required if the EAP client uses a method that verifies the server identity (such
as EAP-TLS), but it does not match the IKEv2 gateway identity.
aggressive = yes | no
whether to use IKEv1 Aggressive or Main Mode (the default).
ah = <cipher suites>
comma-separated list of AH algorithms to be used for the connection, e.g.
sha1-sha256-modp1024. The notation is integrity[-dhgroup]. For IKEv2, multiple
algorithms (separated by -) of the same type can be included in a single proposal.
IKEv1 only includes the first algorithm in a proposal. Only either the ah or esp
keyword may be used, AH+ESP bundles are not supported.
There is no default AH cipher suite since by default ESP is used. The daemon adds
its extensive default proposal to the configured value. To restrict it to the
configured proposal an exclamation mark (!) can be added at the end.
If dh-group is specified, CHILD_SA/Quick Mode setup and rekeying include a separate
Diffie-Hellman exchange (refer to the esp keyword for details).
also = <name>
includes conn section <name>.
auth = <value>
was used by the pluto IKEv1 daemon to use AH integrity protection for ESP encrypted
packets, but is not supported in charon. The ah keyword specifies algorithms to use
for integrity protection with AH, but without encryption. AH+ESP bundles are not
supported.
authby = pubkey | rsasig | ecdsasig | psk | secret | never | xauthpsk | xauthrsasig
how the two security gateways should authenticate each other; acceptable values are
psk or secret for pre-shared secrets, pubkey (the default) for public key
signatures as well as the synonyms rsasig for RSA digital signatures and ecdsasig
for Elliptic Curve DSA signatures. never can be used if negotiation is never to be
attempted or accepted (useful for shunt-only conns). Digital signatures are
superior in every way to shared secrets. IKEv1 additionally supports the values
xauthpsk and xauthrsasig that will enable eXtended AUTHentication (XAUTH) in
addition to IKEv1 main mode based on shared secrets or digital RSA signatures,
respectively. This parameter is deprecated, as two peers do not need to agree on
an authentication method in IKEv2. Use the leftauth parameter instead to define
authentication methods.
auto = ignore | add | route | start
what operation, if any, should be done automatically at IPsec startup; currently-
accepted values are add, route, start and ignore (the default). add loads a
connection without starting it. route loads a connection and installs kernel
traps. If traffic is detected between leftsubnet and rightsubnet, a connection is
established. start loads a connection and brings it up immediately. ignore
ignores the connection. This is equal to deleting a connection from the config
file. Relevant only locally, other end need not agree on it.
closeaction = none | clear | hold | restart
defines the action to take if the remote peer unexpectedly closes a CHILD_SA (see
dpdaction for meaning of values). A closeaction should not be used if the peer
uses reauthentication or uniqueids checking, as these events might trigger the
defined action when not desired.
compress = yes | no
whether IPComp compression of content is proposed on the connection (link-level
compression does not work on encrypted data, so to be effective, compression must
be done before encryption); acceptable values are yes and no (the default). A value
of yes causes the daemon to propose both compressed and uncompressed, and prefer
compressed. A value of no prevents the daemon from proposing or accepting
compression.
dpdaction = none | clear | hold | restart
controls the use of the Dead Peer Detection protocol (DPD, RFC 3706) where
R_U_THERE notification messages (IKEv1) or empty INFORMATIONAL messages (IKEv2) are
periodically sent in order to check the liveliness of the IPsec peer. The values
clear, hold, and restart all activate DPD and determine the action to perform on a
timeout. With clear the connection is closed with no further actions taken. hold
installs a trap policy, which will catch matching traffic and tries to re-negotiate
the connection on demand. restart will immediately trigger an attempt to re-
negotiation the connection. The default is none which disables the active sending
of DPD messages.
dpddelay = 30s | <time>
defines the period time interval with which R_U_THERE messages/INFORMATIONAL
exchanges are sent to the peer. These are only sent if no other traffic is
received. In IKEv2, a value of 0 sends no additional INFORMATIONAL messages and
uses only standard messages (such as those to rekey) to detect dead peers.
dpdtimeout = 150s | <time>
defines the timeout interval, after which all connections to a peer are deleted in
case of inactivity. This only applies to IKEv1, in IKEv2 the default retransmission
timeout applies, as every exchange is used to detect dead peers.
inactivity = <time>
defines the timeout interval, after which a CHILD_SA is closed if it did not send
or receive any traffic. The inactivity counter is reset during CHILD_SA rekeying.
This means that the inactivity timeout must be smaller than the rekeying interval
to have any effect.
eap_identity = <id>
defines the identity the client uses to reply to an EAP Identity request. If
defined on the EAP server, the defined identity will be used as peer identity
during EAP authentication. The special value %identity uses the EAP Identity method
to ask the client for an EAP identity. If not defined, the IKEv2 identity will be
used as EAP identity.
esp = <cipher suites>
comma-separated list of ESP encryption/authentication algorithms to be used for the
connection, e.g. aes128-sha256. The notation is encryption-
integrity[-dhgroup][-esnmode]. For IKEv2, multiple algorithms (separated by -) of
the same type can be included in a single proposal. IKEv1 only includes the first
algorithm in a proposal. Only either the ah or esp keyword may be used, AH+ESP
bundles are not supported.
Defaults to aes128-sha256. The daemon adds its extensive default proposal to this
default or the configured value. To restrict it to the configured proposal an
exclamation mark (!) can be added at the end.
Note: As a responder, the daemon defaults to selecting the first configured
proposal that's also supported by the peer. This may be changed via
strongswan.conf(5) to selecting the first acceptable proposal sent by the peer
instead. In order to restrict a responder to only accept specific cipher suites,
the strict flag (!, exclamation mark) can be used, e.g: aes256-sha512-modp4096!
If dh-group is specified, CHILD_SA/Quick Mode rekeying and initial negotiation use
a separate Diffie-Hellman exchange using the specified group. However, for IKEv2,
the keys of the CHILD_SA created implicitly with the IKE_SA will always be derived
from the IKE_SA's key material. So any DH group specified here will only apply when
the CHILD_SA is later rekeyed or is created with a separate CREATE_CHILD_SA
exchange. Therefore, a proposal mismatch might not immediately be noticed when the
SA is established, but may later cause rekeying to fail.
Valid values for esnmode are esn and noesn. Specifying both negotiates Extended
Sequence Number support with the peer, the default is noesn.
forceencaps = yes | no
force UDP encapsulation for ESP packets even if no NAT situation is detected. This
may help to surmount restrictive firewalls. In order to force the peer to
encapsulate packets, NAT detection payloads are faked.
fragmentation = yes | accept | force | no
whether to use IKE fragmentation (proprietary IKEv1 extension or IKEv2
fragmentation as per RFC 7383). Acceptable values are yes (the default), accept,
force and no. If set to yes, and the peer supports it, oversized IKE messages will
be sent in fragments. If set to accept, support for fragmentation is announced to
the peer but the daemon does not send its own messages in fragments. If set to
force (only supported for IKEv1) the initial IKE message will already be fragmented
if required. Finally, setting the option to no will disable announcing support for
this feature.
Note that fragmented IKE messages sent by a peer are always accepted irrespective
of the value of this option (even when set to no).
ike = <cipher suites>
comma-separated list of IKE/ISAKMP SA encryption/authentication algorithms to be
used, e.g. aes128-sha256-modp3072. The notation is encryption-
integrity[-prf]-dhgroup. If no PRF is given, the algorithms defined for integrity
are used for the PRF. The prf keywords are the same as the integrity algorithms,
but have a prf prefix (such as prfsha1, prfsha256 or prfaesxcbc).
In IKEv2, multiple algorithms and proposals may be included, such as
aes128-aes256-sha1-modp3072-modp2048,3des-sha1-md5-modp1024.
Defaults to aes128-sha256-modp3072. The daemon adds its extensive default proposal
to this default or the configured value. To restrict it to the configured proposal
an exclamation mark (!) can be added at the end.
Note: As a responder the daemon accepts the first supported proposal received from
the peer. In order to restrict a responder to only accept specific cipher suites,
the strict flag (!, exclamation mark) can be used, e.g: aes256-sha512-modp4096!
ikedscp = 000000 | <DSCP field>
Differentiated Services Field Codepoint to set on outgoing IKE packets sent from
this connection. The value is a six digit binary encoded string defining the
Codepoint to set, as defined in RFC 2474.
ikelifetime = 3h | <time>
how long the keying channel of a connection (ISAKMP or IKE SA) should last before
being renegotiated. Also see EXPIRY/REKEY below.
installpolicy = yes | no
decides whether IPsec policies are installed in the kernel by the charon daemon for
a given connection. Allows peaceful cooperation e.g. with the Mobile IPv6 daemon
mip6d who wants to control the kernel policies. Acceptable values are yes (the
default) and no.
keyexchange = ike | ikev1 | ikev2
which key exchange protocol should be used to initiate the connection. Connections
marked with ike use IKEv2 when initiating, but accept any protocol version when
responding.
keyingtries = 3 | <number> | %forever
how many attempts (a whole number or %forever) should be made to negotiate a
connection, or a replacement for one, before giving up (default 3). The value
%forever means 'never give up'. Relevant only locally, other end need not agree on
it.
left = <ip address> | <fqdn> | %any | <range> | <subnet>
The IP address of the left participant's public-network interface or one of several
magic values. The value %any (the default) for the local endpoint signifies an
address to be filled in (by automatic keying) during negotiation. If the local peer
initiates the connection setup the routing table will be queried to determine the
correct local IP address. In case the local peer is responding to a connection
setup then any IP address that is assigned to a local interface will be accepted.
The prefix % in front of a fully-qualified domain name or an IP address will
implicitly set leftallowany=yes.
If %any is used for the remote endpoint it literally means any IP address.
If an FQDN is assigned it is resolved every time a configuration lookup is done. If
DNS resolution times out, the lookup is delayed for that time.
To limit the connection to a specific range of hosts, a range (
10.1.0.0-10.2.255.255 ) or a subnet ( 10.1.0.0/16 ) can be specified, and multiple
addresses, ranges and subnets can be separated by commas. While one can freely
combine these items, to initiate the connection at least one non-range/subnet is
required.
Please note that with the usage of wildcards multiple connection descriptions might
match a given incoming connection attempt. The most specific description is used in
that case.
leftallowany = yes | no
a modifier for left, making it behave as %any although a concrete IP address or
domain name has been assigned.
leftauth = <auth method>
Authentication method to use locally (left) or require from the remote (right)
side. Acceptable values are pubkey for public key authentication (RSA/ECDSA), psk
for pre-shared key authentication, eap to (require the) use of the Extensible
Authentication Protocol in IKEv2, and xauth for IKEv1 eXtended Authentication.
To require a trustchain public key strength for the remote side, specify the key
type followed by the minimum strength in bits (for example ecdsa-384 or
rsa-2048-ecdsa-256). To limit the acceptable set of hashing algorithms for
trustchain validation, append hash algorithms to pubkey or a key strength
definition (for example pubkey-sha256-sha512, rsa-2048-sha256-sha384-sha512, or
rsa-2048-sha256-ecdsa-256-sha256-sha384). Unless disabled in strongswan.conf(5),
or explicit IKEv2 signature constraints are configured (see below), such key types
and hash algorithms are also applied as constraints against IKEv2 signature
authentication schemes used by the remote side.
If both peers support RFC 7427 ("Signature Authentication in IKEv2") specific hash
algorithms to be used during IKEv2 authentication may be configured. The syntax is
the same as above, but with ike: prefix. For example, with ike:pubkey-sha384-sha256
a public key signature scheme with either SHA-384 or SHA-256 would get used for
authentication, in that order and depending on the hash algorithms supported by the
peer. If no specific hash algorithms are configured, the default is to prefer an
algorithm that matches or exceeds the strength of the signature key. If no
constraints with ike: prefix are configured any signature scheme constraint
(without ike: prefix) will also apply to IKEv2 authentication, unless this is
disabled in strongswan.conf(5).
To use or require RSASSA-PSS signatures use rsa/pss instead of rsa as in e.g.
ike:rsa/pss-sha256. If pubkey or rsa constraints are configured RSASSA-PSS
signatures will only be used/accepted if enabled in strongswan.conf(5).
For eap, an optional EAP method can be appended. Currently defined methods are eap-
aka, eap-gtc, eap-md5, eap-mschapv2, eap-peap, eap-sim, eap-tls, eap-ttls, eap-
dynamic, and eap-radius. Alternatively, IANA assigned EAP method numbers are
accepted. Vendor specific EAP methods are defined in the form eap-type-vendor (e.g.
eap-7-12345). To specify signature and trust chain constraints for EAP-(T)TLS,
append a colon to the EAP method, followed by the key type/size and hash algorithm
as discussed above. For xauth, an XAuth authentication backend can be specified,
such as xauth-generic or xauth-eap. If XAuth is used in leftauth, Hybrid
authentication is used. For traditional XAuth authentication, define XAuth in
lefauth2.
leftauth2 = <auth method>
Same as leftauth, but defines an additional authentication exchange. In IKEv1, only
XAuth can be used in the second authentication round. IKEv2 supports multiple
complete authentication rounds using "Multiple Authentication Exchanges" defined in
RFC 4739. This allows, for example, separated authentication of host and user.
leftca = <issuer dn> | %same
the distinguished name of a certificate authority which is required to lie in the
trust path going from the left participant's certificate up to the root
certification authority. %same means that the value configured for the right
participant should be reused.
leftca2 = <issuer dn> | %same
Same as leftca, but for the second authentication round (IKEv2 only).
leftcert = <path>
the path to the left participant's X.509 certificate. The file can be encoded
either in PEM or DER format. OpenPGP certificates are supported as well. Both
absolute paths or paths relative to /etc/ipsec.d/certs are accepted. By default
leftcert sets leftid to the distinguished name of the certificate's subject. The
left participant's ID can be overridden by specifying a leftid value which must be
certified by the certificate, though.
A value in the form %smartcard[<slot nr>[@<module>]]:<keyid> defines a specific
certificate to load from a PKCS#11 backend for this connection. See
ipsec.secrets(5) for details about smartcard definitions. leftcert is required
only if selecting the certificate with leftid is not sufficient, for example if
multiple certificates use the same subject.
Multiple certificate paths or PKCS#11 backends can be specified in a comma
separated list. The daemon chooses the certificate based on the received
certificate requests if possible before enforcing the first.
leftcert2 = <path>
Same as leftcert, but for the second authentication round (IKEv2 only).
leftcertpolicy = <OIDs>
Comma separated list of certificate policy OIDs the peer's certificate must have.
OIDs are specified using the numerical dotted representation.
leftdns = <servers>
Comma separated list of DNS server addresses to exchange as configuration
attributes. On the initiator, a server is a fixed IPv4/IPv6 address, or
%config4/%config6 to request attributes without an address. On the responder, only
fixed IPv4/IPv6 addresses are allowed and define DNS servers assigned to the
client.
leftfirewall = yes | no
whether the left participant is doing forwarding-firewalling (including
masquerading) using iptables for traffic from leftsubnet, which should be turned
off (for traffic to the other subnet) once the connection is established;
acceptable values are yes and no (the default). May not be used in the same
connection description with leftupdown. Implemented as a parameter to the default
ipsec _updown script. See notes below. Relevant only locally, other end need not
agree on it.
If one or both security gateways are doing forwarding firewalling (possibly
including masquerading), and this is specified using the firewall parameters,
tunnels established with IPsec are exempted from it so that packets can flow
unchanged through the tunnels. (This means that all subnets connected in this
manner must have distinct, non-overlapping subnet address blocks.) This is done by
the default ipsec _updown script.
In situations calling for more control, it may be preferable for the user to supply
his own updown script, which makes the appropriate adjustments for his system.
leftgroups = <group list>
a comma separated list of group names. If the leftgroups parameter is present then
the peer must be a member of at least one of the groups defined by the parameter.
leftgroups2 = <group list>
Same as leftgroups, but for the second authentication round defined with leftauth2.
lefthostaccess = yes | no
inserts a pair of INPUT and OUTPUT iptables rules using the default ipsec _updown
script, thus allowing access to the host itself in the case where the host's
internal interface is part of the negotiated client subnet. Acceptable values are
yes and no (the default).
leftid = <id>
how the left participant should be identified for authentication; defaults to left
or the subject of the certificate configured with leftcert. If leftcert is
configured the identity has to be confirmed by the certificate.
Can be an IP address, a fully-qualified domain name, an email address or a
Distinguished Name for which the ID type is determined automatically and the string
is converted to the appropriate encoding. The rules for this conversion are
described in IDENTITY PARSING below.
In certain special situations the identity parsing above might be inadequate or
produce the wrong result. Examples are the need to encode a FQDN as KEY_ID or the
string parser being unable to produce the correct binary ASN.1 encoding of a
certificate's DN. For these situations it is possible to enforce a specific
identity type and to provide the binary encoding of the identity. To do this a
prefix may be used, followed by a colon (:). If the number sign (#) follows the
colon, the remaining data is interpreted as hex encoding, otherwise the string is
used as is as the identification data. Note: The latter implies that no conversion
is performed for non-string identities. For example, ipv4:10.0.0.1 does not create
a valid ID_IPV4_ADDR IKE identity, as it does not get converted to binary
0x0a000001. Instead, one could use ipv4:#0a000001 to get a valid identity, but just
using the implicit type with automatic conversion is usually simpler. The same
applies to the ASN.1 encoded types. The following prefixes are known: ipv4, ipv6,
rfc822, email, userfqdn, fqdn, dns, asn1dn, asn1gn and keyid. Custom type prefixes
may be specified by surrounding the numerical type value by curly brackets.
For IKEv2 and rightid the prefix % in front of the identity prevents the daemon
from sending IDr in its IKE_AUTH request and will allow it to verify the configured
identity against the subject and subjectAltNames contained in the responder's
certificate (otherwise it is only compared with the IDr returned by the responder).
The IDr sent by the initiator might otherwise prevent the responder from finding a
config if it has configured a different value for leftid.
leftid2 = <id>
identity to use for a second authentication for the left participant (IKEv2 only);
defaults to leftid.
leftikeport = <port>
UDP port the left participant uses for IKE communication. If unspecified, port 500
is used with the port floating to 4500 if a NAT is detected or MOBIKE is enabled.
Specifying a local IKE port different from the default additionally requires a
socket implementation that listens on this port.
leftprotoport = <protocol>/<port>
restrict the traffic selector to a single protocol and/or port. This option is now
deprecated, protocol/port information can be defined for each subnet directly in
leftsubnet.
leftsigkey = <raw public key> | <path to public key>
the left participant's public key for public key signature authentication, in
PKCS#1 format using hex (0x prefix) or base64 (0s prefix) encoding. With the
optional dns: or ssh: prefix in front of 0x or 0s, the public key is expected to be
in either the RFC 3110 (not the full RR, only RSA key part) or RFC 4253 public key
format, respectively. Also accepted is the path to a file containing the public
key in PEM, DER or SSH encoding. Both absolute paths or paths relative to
/etc/ipsec.d/certs are accepted.
leftsendcert = never | no | ifasked | always | yes
Accepted values are never or no, always or yes, and ifasked (the default), the
latter meaning that the peer must send a certificate request payload in order to
get a certificate in return.
leftsourceip = %config4 | %config6 | <ip address>
Comma separated list of internal source IPs to use in a tunnel, also known as
virtual IP. If the value is one of the synonyms %config, %cfg, %modeconfig, or
%modecfg, an address (from the tunnel address family) is requested from the peer.
With %config4 and %config6 an address of the given address family will be requested
explicitly. If an IP address is configured, it will be requested from the
responder, which is free to respond with a different address.
rightsourceip = %config | <network>/<netmask> | <from>-<to> | %poolname
Comma separated list of internal source IPs to use in a tunnel for the remote peer.
If the value is %config on the responder side, the initiator must propose an
address which is then echoed back. Also supported are address pools expressed as
network/netmask and from-to or the use of an external IP address pool using
%poolname, where poolname is the name of the IP address pool used for the lookup.
leftsubnet = <ip subnet>[[<proto/port>]][,...]
private subnet behind the left participant, expressed as network/netmask; if
omitted, essentially assumed to be left/32, signifying that the left end of the
connection goes to the left participant only. Configured subnets of the peers may
differ, the protocol narrows it to the greatest common subnet. In IKEv1, this may
lead to problems with other implementations, make sure to configure identical
subnets in such configurations. IKEv2 supports multiple subnets separated by
commas. IKEv1 only interprets the first subnet of such a definition, unless the
Cisco Unity extension plugin is enabled. This is due to a limitation of the IKEv1
protocol, which only allows a single pair of subnets per CHILD_SA. So to tunnel
several subnets a conn entry has to be defined and brought up for each pair of
subnets.
The optional part after each subnet enclosed in square brackets specifies a
protocol/port to restrict the selector for that subnet.
Examples: leftsubnet=10.0.0.1[tcp/http],10.0.0.2[6/80] or
leftsubnet=fec1::1[udp],10.0.0.0/16[/53]. Instead of omitting either value %any
can be used to the same effect, e.g.
leftsubnet=fec1::1[udp/%any],10.0.0.0/16[%any/53].
If the protocol is icmp or ipv6-icmp the port is interpreted as ICMP message type
if it is less than 256 or as type and code if it is greater or equal to 256, with
the type in the most significant 8 bits and the code in the least significant 8
bits.
The port value can alternatively take the value %opaque for RFC 4301 OPAQUE
selectors, or a numerical range in the form 1024-65535. None of the kernel
backends currently supports opaque or port ranges and uses %any for policy
installation instead.
Instead of specifying a subnet, %dynamic can be used to replace it with the IKE
address, having the same effect as omitting leftsubnet completely. Using %dynamic
can be used to define multiple dynamic selectors, each having a potentially
different protocol/port definition.
leftupdown = <path>
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. Relevant only
locally, other end need not agree on it. Charon uses the updown script to insert
firewall rules only, since routing has been implemented directly into the daemon.
lifebytes = <number>
the number of bytes transmitted over an IPsec SA before it expires.
lifepackets = <number>
the number of packets transmitted over an IPsec SA before it expires.
lifetime = 1h | <time>
how long a particular instance of a connection (a set of encryption/authentication
keys for user packets) should last, from successful negotiation to expiry;
acceptable values are an integer optionally followed by s (a time in seconds) or a
decimal number followed by m, h, or d (a time in minutes, hours, or days
respectively) (default 1h, maximum 24h). Normally, the connection is renegotiated
(via the keying channel) before it expires (see margintime). The two ends need not
exactly agree on lifetime, although if they do not, there will be some clutter of
superseded connections on the end which thinks the lifetime is longer. Also see
EXPIRY/REKEY below.
marginbytes = <number>
how many bytes before IPsec SA expiry (see lifebytes) should attempts to negotiate
a replacement begin.
marginpackets = <number>
how many packets before IPsec SA expiry (see lifepackets) should attempts to
negotiate a replacement begin.
margintime = 9m | <time>
how long before connection expiry or keying-channel expiry should attempts to
negotiate a replacement begin; acceptable values as for lifetime (default 9m).
Relevant only locally, other end need not agree on it. Also see EXPIRY/REKEY below.
mark = <value>[/<mask>]
sets an XFRM mark on the inbound policy and outbound IPsec SA and policy. If the
mask is missing then a default mask of 0xffffffff is assumed. The special value
%unique assigns a unique value to each newly created IPsec SA. To additionally make
the mark unique for each IPsec SA direction (in/out) the special value %unique-dir
may be used.
mark_in = <value>[/<mask>]
sets an XFRM mark on the inbound policy (not on the SA). If the mask is missing
then a default mask of 0xffffffff is assumed.
mark_out = <value>[/<mask>]
sets an XFRM mark on the outbound IPsec SA and policy. If the mask is missing then
a default mask of 0xffffffff is assumed.
mobike = yes | no
enables the IKEv2 MOBIKE protocol defined by RFC 4555. Accepted values are yes (the
default) and no. If set to no, the charon daemon will not actively propose MOBIKE
as initiator and ignore the MOBIKE_SUPPORTED notify as responder.
modeconfig = push | pull
defines which mode is used to assign a virtual IP. Accepted values are push and
pull (the default). Push mode is currently not supported with IKEv2. The setting
must be the same on both sides.
reauth = yes | no
whether rekeying of an IKE_SA should also reauthenticate the peer. In IKEv1,
reauthentication is always done. In IKEv2, a value of no rekeys without
uninstalling the IPsec SAs, a value of yes (the default) creates a new IKE_SA from
scratch and tries to recreate all IPsec SAs.
rekey = yes | no
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 charon from requesting renegotiation, it does not prevent
responding to renegotiation requested from the other end, so no will be largely
ineffective unless both ends agree on it. Also see reauth.
rekeyfuzz = 100% | <percentage>
maximum percentage by which marginbytes, marginpackets and margintime 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
`%' (defaults to 100%). The value of marginTYPE, after this random increase, must
not exceed lifeTYPE (where TYPE is one of bytes, packets or time). The value 0%
will suppress randomization. Relevant only locally, other end need not agree on
it. Also see EXPIRY/REKEY below.
replay_window = -1 | <number>
The IPsec replay window size for this connection. With the default of -1 the value
configured with charon.replay_window in strongswan.conf(5) is used. Larger values
than 32 are supported using the Netlink backend only, a value of 0 disables IPsec
replay protection.
reqid = <number>
sets the reqid for a given connection to a pre-configured fixed value.
sha256_96 = no | yes
HMAC-SHA-256 is used with 128-bit truncation with IPsec. For compatibility with
implementations that incorrectly use 96-bit truncation this option may be enabled
to configure the shorter truncation length in the kernel. This is not negotiated,
so this only works with peers that use the incorrect truncation length (or have
this option enabled).
tfc = <value>
number of bytes to pad ESP payload data to. Traffic Flow Confidentiality is
currently supported in IKEv2 and applies to outgoing packets only. The special
value %mtu fills up ESP packets with padding to have the size of the MTU.
type = tunnel | transport | transport_proxy | passthrough | drop
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; transport_proxy, signifying the special
Mobile IPv6 transport proxy mode; passthrough, signifying that no IPsec processing
should be done at all; drop, signifying that packets should be discarded.
xauth = client | server
specifies the role in the XAuth protocol if activated by authby=xauthpsk or
authby=xauthrsasig. Accepted values are server and client (the default).
xauth_identity = <id>
defines the identity/username the client uses to reply to an XAuth request. If not
defined, the IKEv1 identity will be used as XAuth identity.
CONN PARAMETERS: IKEv2 MEDIATION EXTENSION
The following parameters are relevant to IKEv2 Mediation Extension operation only.
mediation = yes | no
whether this connection is a mediation connection, ie. whether this connection is
used to mediate other connections. Mediation connections create no child SA.
Acceptable values are no (the default) and yes.
mediated_by = <name>
the name of the connection to mediate this connection through. If given, the
connection will be mediated through the named mediation connection. The mediation
connection must set mediation=yes.
me_peerid = <id>
ID as which the peer is known to the mediation server, ie. which the other end of
this connection uses as its leftid on its connection to the mediation server. This
is the ID we request the mediation server to mediate us with. If me_peerid is not
given, the rightid of this connection will be used as peer ID.
CA SECTIONS
These are optional sections that can be used to assign special parameters to a
Certification Authority (CA). Because the daemons automatically import CA certificates
from /etc/ipsec.d/cacerts, there is no need to explicitly add them with a CA section,
unless you want to assign special parameters (like a CRL) to a CA.
also = <name>
includes ca section <name>.
auto = ignore | add
currently can have either the value ignore (the default) or add.
cacert = <path>
defines a path to the CA certificate either relative to /etc/ipsec.d/cacerts or as
an absolute path.
A value in the form %smartcard[<slot nr>[@<module>]]:<keyid> defines a specific CA
certificate to load from a PKCS#11 backend for this CA. See ipsec.secrets(5) for
details about smartcard definitions.
crluri = <uri>
defines a CRL distribution point (ldap, http, or file URI)
crluri1
synonym for crluri.
crluri2 = <uri>
defines an alternative CRL distribution point (ldap, http, or file URI)
ocspuri = <uri>
defines an OCSP URI.
ocspuri1
synonym for ocspuri.
ocspuri2 = <uri>
defines an alternative OCSP URI.
certuribase = <uri>
defines the base URI for the Hash and URL feature supported by IKEv2. Instead of
exchanging complete certificates, IKEv2 allows one to send an URI that resolves to
the DER encoded certificate. The certificate URIs are built by appending the SHA1
hash of the DER encoded certificates to this base URI.
CONFIG SECTIONS
At present, the only config section known to the IPsec software is the one named setup,
which contains information used when the software is being started. The currently-
accepted parameter names in a config setup section are:
cachecrls = yes | no
if enabled, certificate revocation lists (CRLs) fetched via HTTP or LDAP will be
cached in /etc/ipsec.d/crls/ under a unique file name derived from the
certification authority's public key.
charondebug = <debug list>
how much charon debugging output should be logged. A comma separated list
containing type/level-pairs may be specified, e.g: dmn 3, ike 1, net -1.
Acceptable values for types are dmn, mgr, ike, chd, job, cfg, knl, net, asn, enc,
lib, esp, tls, tnc, imc, imv, pts and the level is one of -1, 0, 1, 2, 3, 4 (for
silent, audit, control, controlmore, raw, private). By default, the level is set
to 1 for all types. For more flexibility see LOGGER CONFIGURATION in
strongswan.conf(5).
strictcrlpolicy = yes | ifuri | no
defines if a fresh CRL must be available in order for the peer authentication based
on RSA signatures to succeed. IKEv2 additionally recognizes ifuri which reverts to
yes if at least one CRL URI is defined and to no if no URI is known.
uniqueids = yes | no | never | replace | keep
whether a particular participant ID should be kept unique, with any new IKE_SA
using an ID deemed to replace all old ones using that ID; acceptable values are yes
(the default), no and never. Participant IDs normally are unique, so a new IKE_SA
using the same ID is almost invariably intended to replace an old one. The
difference between no and never is that the daemon will replace old IKE_SAs when
receiving an INITIAL_CONTACT notify if the option is no but will ignore these
notifies if never is configured. The daemon also accepts the value replace which
is identical to yes and the value keep to reject new IKE_SA setups and keep the
duplicate established earlier.
IDENTITY PARSING
The type and binary encoding of identity strings specified in leftid are detected as
follows:
• If the string value contains an equal sign (=) it is assumed to be a Distinguished
Name, with RDNs separated by commas (,) or slashes (/ - the string must start with
a slash to use this syntax). An attempt is made to create a binary ASN.1 encoding
from this string. If that fails the type is set to KEY_ID with the literal string
value adopted as encoding.
• If the string value contains an @ the type depends on the position of that
character:
• If the string begins with @# the type is set to KEY_ID and the string
following that prefix is assumed to be the hex-encoded binary value of the
identity.
• If the string begins with @@ the type is set to USER_FQDN and the encoding
is the literal string after that prefix.
• If the string begins with @ the type is set to FQDN and the encoding is the
literal string after that prefix.
• All remaining strings containing an @ are assumed to be of type
USER_FQDN/RFC822 with the literal string value as encoding.
• If the value does not contain any @ or = characters it is parsed as follows:
• If the value is an empty string, or equals %any[6], 0.0.0.0, ::, or * the
type is set to ID_ANY, which matches any other identity.
• If the value contains a colon (:) it is assumed to be an IPv6 address. But
if parsing the address and converting it to its binary encoding fails the
type is set to KEY_ID and the encoding is the literal value.
• For all other strings an attempt at parsing them as IPv4 addresses is made.
If that fails the type is set to FQDN and the literal value is adopted as
encoding (this is where domain names and simple names end up).
SA EXPIRY/REKEY
The IKE SAs and IPsec SAs negotiated by the daemon can be configured to expire after a
specific amount of time. For IPsec SAs this can also happen after a specified number of
transmitted packets or transmitted bytes. The following settings can be used to configure
this:
Setting Default Setting Default
──────────────────────────────────────────────────
IKE SA IPsec SA
ikelifetime 3h lifebytes -
lifepackets -
lifetime 1h
Rekeying
IKE SAs as well as IPsec SAs can be rekeyed before they expire. This can be configured
using the following settings:
Setting Default Setting Default
───────────────────────────────────────────────────
IKE and IPsec SA IPsec SA
margintime 9m marginbytes -
marginpackets -
Randomization
To avoid collisions the specified margins are increased randomly before subtracting them
from the expiration limits (see formula below). This is controlled by the rekeyfuzz
setting:
Setting Default
──────────────────────
IKE and IPsec SA
rekeyfuzz 100%
Randomization can be disabled by setting rekeyfuzz to 0%.
Formula
The following formula is used to calculate the rekey time of IPsec SAs:
rekeytime = lifetime - (margintime + random(0, margintime * rekeyfuzz))
It applies equally to IKE SAs and byte and packet limits for IPsec SAs.
Example
Let's consider the default configuration:
lifetime = 1h
margintime = 9m
rekeyfuzz = 100%
From the formula above follows that the rekey time lies between:
rekeytime_min = 1h - (9m + 9m) = 42m
rekeytime_max = 1h - (9m + 0m) = 51m
Thus, the daemon will attempt to rekey the IPsec SA at a random time between 42 and 51
minutes after establishing the SA. Or, in other words, between 9 and 18 minutes before the
SA expires.
Notes
• Since the rekeying of an SA needs some time, the margin values must not be too low.
• The value margin... + margin... * rekeyfuzz must not exceed the original limit. For
example, specifying margintime = 30m in the default configuration is a bad idea as
there is a chance that the rekey time equals zero and, thus, rekeying gets
disabled.
FILES
/etc/ipsec.conf
/etc/ipsec.d/aacerts
/etc/ipsec.d/acerts
/etc/ipsec.d/cacerts
/etc/ipsec.d/certs
/etc/ipsec.d/crls
SEE ALSO
strongswan.conf(5), ipsec.secrets(5), ipsec(8)
HISTORY
Originally written for the FreeS/WAN project by Henry Spencer. Updated and extended for
the strongSwan project <http://www.strongswan.org> by Tobias Brunner, Andreas Steffen and
Martin Willi.