The
ipsec.conf
file
specifies most configuration and control information for the
Openswan IPsec subsystem.
(The major exception is secrets for authentication;
see
ipsec.secrets(5).)
Its contents are not security-sensitive
unless
manual keying is being done for more than just testing,
in which case the encryption/authentication keys in the
descriptions for the manually-keyed connections are very sensitive
(and those connection descriptions
are probably best kept in a separate file,
via the include facility described below).
The file is a text file, consisting of one or more
sections.
White space followed by
#
followed by anything to the end of the line
is a comment and is ignored,
as are empty lines which are not within a section.
A line which contains
include
and a file name, separated by white space,
is replaced by the contents of that file,
preceded and followed by empty lines.
If the file name is not a full pathname,
it is considered to be relative to the directory containing the
including file.
Such inclusions can be nested.
Only a single filename may be supplied, and it may not contain white space,
but it may include shell wildcards (see
sh(1));
for example:
includeipsec.*.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:
typename
where
type
indicates what type of section follows, and
name
is an arbitrary name which distinguishes the section from others
of the same type.
(Names must start with a letter and may contain only
letters, digits, periods, underscores, and hyphens.)
All subsequent non-empty lines
which begin with white space are part of the section;
comments within a section must begin with white space too.
There may be only one section of a given type with a given name.
Lines within the section are generally of the form
parameter=value
(note the mandatory preceding white space).
There can be white space on either side of the
=.
Parameter names follow the same syntax as section names,
and are specific to a section type.
Unless otherwise explicitly specified,
no parameter name may appear more than once in a section.
An empty
value
stands for the system default value (if any) of the parameter,
i.e. it is roughly equivalent to omitting the parameter line entirely.
A
value
may contain white space only if the entire
value
is enclosed in double quotes (");
a
value
cannot itself contain a double quote,
nor may it be continued across more than one line.
Numeric values are specified to be either an ``integer''
(a sequence of digits) or a ``decimal number''
(sequence of digits optionally followed by `.' and another sequence of digits).
There is currently one parameter which is available in any type of
section:
also
the value is a section name;
the parameters of that section are appended to this section,
as if they had been written as part of it.
The specified section must exist, must follow the current one,
and must have the same section type.
(Nesting is permitted,
and there may be more than one
also
in a single section,
although it is forbidden to append the same section more than once.)
This allows, for example, keeping the encryption keys
for a connection in a separate file
from the rest of the description, by using both an
also
parameter and an
include
line.
(Caution, see BUGS below for some restrictions.)
Parameter names beginning with
x-
(or
X-,
or
x_,
or
X_)
are reserved for user extensions and will never be assigned meanings
by IPsec.
Parameters with such names must still observe the syntax rules
(limits on characters used in the name;
no white space in a non-quoted value;
no newlines or double quotes within the value).
All other as-yet-unused parameter names are reserved for future IPsec
improvements.
A section with name
%default
specifies defaults for sections of the same type.
For each parameter in it,
any section of that type which does not have a parameter of the same name
gets a copy of the one from the
%default
section.
There may be multiple
%default
sections of a given type,
but only one default may be supplied for any specific parameter name,
and all
%default
sections of a given type must precede all non-%default
sections of that type.
%default
sections may not contain
also
parameters.
Currently there are two types of section:
a
config
section specifies general configuration information for IPsec,
while a
conn
section specifies an IPsec connection.
CONN SECTIONS
A
conn
section contains a
connection specification,
defining a network connection to be made using IPsec.
The name given is arbitrary, and is used to identify the connection to
ipsec_auto(8)
and
ipsec_manual(8).
Here's a simple example:
conn snt
left=10.11.11.1
leftsubnet=10.0.1.0/24
leftnexthop=172.16.55.66
right=192.168.22.1
rightsubnet=10.0.2.0/24
rightnexthop=172.16.88.99
keyingtries=0 # be very persistent
ike=aes128-sha,aes128-md5 # propose only these algo. in Phase1.
esp=aes128-sha1,aes128-md5 # propose only these algo. in Phase2.
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.
Many of the parameters relate to one participant or the other;
only the ones for
left
are listed here, but every parameter whose name begins with
left
has a
right
counterpart,
whose description is the same but with
left
and
right
reversed.
Parameters are optional unless marked ``(required)'';
a parameter required for manual keying need not be included for
a connection which will use only automatic keying, and vice versa.
CONN PARAMETERS: GENERAL
The following parameters are relevant to both automatic and manual keying.
Unless otherwise noted,
for a connection to work,
in general it is necessary for the two ends to agree exactly
on the values of these parameters.
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;
and
passthrough
(supported only for manual keying),
signifying that no IPsec processing should be done at all
left
(required)
the IP address of the left participant's public-network interface,
in any form accepted by
ipsec_ttoaddr(3).
If it is the magic value
%defaultroute,
and
interfaces=%defaultroute
is used in the
configsetup
section,
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 magic value
%any
signifies an address to be filled in (by automatic keying) during
negotiation;
the magic value
%opportunistic
signifies that both
left
and
leftnexthop
are to be filled in (by automatic keying) from DNS data for
left's
client.
leftsubnet
private subnet behind the left participant, expressed as
network/netmask
(actually, any form acceptable to
ipsec_ttosubnet(3));
if omitted, essentially assumed to be left/32,
signifying that the left end of the connection goes to the left participant only
leftnexthop
next-hop gateway IP address for the left participant's connection
to the public network;
defaults to
%direct
(meaning
right).
If the value is to be overridden by the
left=%defaultroute
method (see above),
an explicit value must
not
be given.
If that method is not being used,
but
leftnexthop
is
%defaultroute,
and
interfaces=%defaultroute
is used in the
configsetup
section,
the next-hop gateway address of the default-route interface
will be used.
The magic value
%direct
signifies a value to be filled in (by automatic keying)
with the peer's address.
Relevant only locally, other end need not agree on it.
leftupdown
what ``updown'' script to run to adjust routing and/or firewalling
when the status of the connection
changes (default
ipsec _updown).
May include positional parameters separated by white space
(although this requires enclosing the whole string in quotes);
including shell metacharacters is unwise.
See
ipsec_pluto(8)
for details.
Relevant only locally, other end need not agree on it.
leftfirewall
whether the left participant is doing forwarding-firewalling
(including masquerading) 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 (the default)
no.
May not be used in the same connection description with
leftupdown.
Implemented as a parameter to the default
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
updown
script (see
ipsec_pluto(8)).
The implementation of this makes certain assumptions about firewall setup,
notably the use of the old
ipfwadm
interface to the firewall.
In situations calling for more control,
it may be preferable for the user to supply his own
updown
script,
which makes the appropriate adjustments for his system.
CONN PARAMETERS: AUTOMATIC KEYING
The following parameters are relevant only to automatic keying,
and are ignored in manual keying.
Unless otherwise noted,
for a connection to work,
in general it is necessary for the two ends to agree exactly
on the values of these parameters.
keyexchange
method of key exchange;
the default and currently the only accepted value is
ike
auto
what operation, if any, should be done automatically at IPsec startup;
currently-accepted values are
add
(signifying an
ipsec auto--add),
route
(signifying that plus an
ipsec auto--route),
start
(signifying that plus an
ipsec auto--up),
and
ignore
(also the default) (signifying no automatic startup operation).
This parameter is ignored unless the
plutoload
or
plutostart
configuration parameter is set suitably; see the
configsetup
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).
auth
whether authentication should be done as part of
ESP encryption, or separately using the AH protocol;
acceptable values are
esp
(the default) and
ah.
authby
how the two security gateways should authenticate each other;
acceptable values are
secret
for shared secrets (the default) and
rsasig
for RSA digital signatures
leftid
how
the left participant
should be identified for authentication;
defaults to
left.
Can be an IP address (in any
ipsec_ttoaddr(3)
syntax)
or a fully-qualified domain name preceded by
@
(which is used as a literal string and not resolved).
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
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.
Caution:
if two connection descriptions
specify different public keys for the same
leftid,
confusion and madness will ensue.
leftrsasigkey2
if present, a second public key.
Either key can authenticate the signature, allowing for key rollover.
aggrmode
Use aggressive mode ISAKMP negotiation. The default is
main mode. Aggressive mode is less secure than main mode as it reveals
your identity to an eavesdropper, but is needed to support road warriors
using PSK keys or to interoperate with other buggy implementations insisting
on using aggressive mode. acceptable values are
yes
or
no
(the default).
xauth
Use XAUTH / Mode Config for this connection. This uses PAM for authentication
currently, and it not well documented. Use the source :) Acceptable values are
yes
or
no
(the default).
dpddelay
Set the delay (in seconds) between Dead Peer Dectection
(draft-ietf-ipsec-dpd-02) keepalives (R_U_THERE, R_U_THERE_ACK)
that are sent for this connection (default
30
seconds). If dpdtimeout is set, but not dpddelay, dpddelay will be set
to the default.
dpdtimeout
Set the length of time (in seconds) we will idle without hearing either an
R_U_THERE poll from our peer, or an R_U_THERE_ACK reply. After this period
has elapsed with no response and no traffic, we will declare the peer dead,
and remove the SA (default
120
seconds). If dpddelay is set, but not dpdtimeout, dpdtimeout will be set
to the default.
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, whileclear means the eroute and SA with both be cleared. dpdaction=clear is
really only usefull on the server of a Road Warrior config.
pfs
whether Perfect Forward Secrecy of keys is desired on the connection's
keying channel
(with PFS, penetration of the key-exchange protocol
does not compromise keys negotiated earlier);
acceptable values are
yes
(the default)
and
no.
keylife
how long a particular instance of a connection
(a set of encryption/authentication keys for user packets) should last,
from successful negotiation to expiry;
acceptable values are an integer optionally followed by
s
(a time in seconds)
or a decimal number followed by
m,
h,
or
d
(a time
in minutes, hours, or days respectively)
(default
8.0h,
maximum
24h).
Normally, the connection is renegotiated (via the keying channel)
before it expires.
The two ends need not exactly agree on
keylife,
although if they do not,
there will be some clutter of superseded connections on the end
which thinks the lifetime is longer.
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
keylife
(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
keylife.
The value
0%
will suppress time randomization.
Relevant only locally, other end need not agree on it.
keyingtries
how many attempts (an integer) should be made to
negotiate a connection, or a replacement for one, before giving up
(default
3);
the value
0
means ``never give up''
Relevant only locally, other end need not agree on it.
ikelifetime
how long the keying channel of a connection (buzzphrase: ``ISAKMP SA'')
should last before being renegotiated;
acceptable values as for
keylife
(default set by
ipsec_pluto(8),
currently
1h,
maximum
8h).
The two-ends-disagree case is similar to that of
keylife.
compress
whether IPComp compression of content is desired on the connection
(link-level compression does not work on encrypted data,
so to be effective, compression must be done before encryption);
acceptable values are
yes
and
no
(the default).
The two ends need not agree.
A value of
no
is absolute:
IPsec will neither propose nor accept compression.
A value of
yes
causes IPsec to propose both compressed and uncompressed,
and prefer compressed.
disablearrivalcheck
whether KLIPS's normal tunnel-exit check
(that a packet emerging from a tunnel has plausible addresses in its header)
should be disabled;
acceptable values are
yes
(the backward-compatible default)
and
no.
Relevant only locally, other end need not agree on it.
esp
(ALGO patch feature)
ESP encryption/authentication algorithms to be built
into ISAKMP Phase2 proposals for the connection, e.g.
aes128-sha1,aes128-md5
or
aes256-sha1,twofish256-sha1
Default behaviour as responder is to accept first
locally supported algorithm
combo
proposed by peer; you can enforce to only
accept listed algorithms by appending an
``!''
(admiration mark), e.g.
aes256-sha1,twofish256-sha1!
Please note that actual avalable algorithms
depends on your kernel (static and modular) setup.
You can see IPSec algorithms available to
pluto
with
ipsec auto --status | grep alg.*ESP
Default value is
3des-md5,3des-sha1
pfsgroup
(ALGO patch feature)
PFS group to be used if
pfs=yes, e.g.
pfsgroup=modp1536
Because PFS group is not negotiated it is
single valued
and must be previously coordinated with peer.
Possible values are:
modp<value>
with
value
one of 1024, 1536, 2048, 3072 y 4096.
modp. If not specified, it will use
same DH group of phase1.
Default value is
[same as Phase1's DH group]
ike
(ALGO patch feature)
IKE encryption/authentication algorithms to be built
into ISAKMP Phase1 proposals for the connection, e.g.
aes128-sha,aes128-md5
or
aes256-sha,twofish256-sha
Please note
that sha1 algorithm here is named
sha
instead of sha1
In addition, DH group can be appended to each element as
-modp<value>
with
value
one of 1024, 1536, 2048, 3072 y 4096.
Default behaviour as responder is to accept first
locally supported algorithm
combo
proposed by peer; you can enforce to only
accept listed algorithms by appending an
``!''
(admiration mark), e.g.
aes256-sha,twofish256-sha!
Default value is
3des-md5-modp1536,3des-md5-modp1024,\3des-sha-modp1536,3des-sha-modp1024
You can see IKE algorithms supported by
pluto
with
ipsec auto --status | grep alg.*IKE
CONN PARAMETERS: MANUAL KEYING
The following parameters are relevant only to manual keying,
and are ignored in 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.
A manually-keyed
connection must specify at least one of AH or ESP.
spi
(this or
spibase
required for manual keying)
the SPI number to be used for the connection (see
ipsec_manual(8));
must be of the form 0xhex,
where
hex
is one or more hexadecimal digits
(note, it will generally be necessary to make
spi
at least
0x100
to be acceptable to KLIPS,
and use of SPIs in the range
0x100-0xfff
is recommended)
spibase
(this or
spi
required for manual keying)
the base number for the SPIs to be used for the connection (see
ipsec_manual(8));
must be of the form 0xhex0,
where
hex
is one or more hexadecimal digits
(note, it will generally be necessary to make
spibase
at least
0x100
for the resulting SPIs
to be acceptable to KLIPS,
and use of numbers in the range
0x100-0xff0
is recommended)
esp
ESP encryption/authentication algorithm to be used
for the connection, e.g.
3des-md5-96
(must be suitable as a value of
ipsec_spi(8)'s
--esp
option);
default is not to use ESP
espenckey
ESP encryption key
(must be suitable as a value of
ipsec_spi(8)'s
--enckey
option)
(may be specified separately for each direction using
leftespenckey
(leftward SA)
and
rightespenckey
parameters)
espauthkey
ESP authentication key
(must be suitable as a value of
ipsec_spi(8)'s
--authkey
option)
(may be specified separately for each direction using
leftespauthkey
(leftward SA)
and
rightespauthkey
parameters)
espreplay_window
ESP replay-window setting,
an integer from
0
(the
ipsec_manual
default, which turns off replay protection) to
64;
relevant only if ESP authentication is being used
leftespspi
SPI to be used for the leftward ESP SA, overriding
automatic assignment using
spi
or
spibase;
typically a hexadecimal number beginning with
0x
ah
AH authentication algorithm to be used
for the connection, e.g.
hmac-md5-96
(must be suitable as a value of
ipsec_spi(8)'s
--ah
option);
default is not to use AH
ahkey
(required if
ah
is present) AH authentication key
(must be suitable as a value of
ipsec_spi(8)'s
--authkey
option)
(may be specified separately for each direction using
leftahkey
(leftward SA)
and
rightahkey
parameters)
ahreplay_window
AH replay-window setting,
an integer from
0
(the
ipsec_manual
default, which turns off replay protection) to
64
leftahspi
SPI to be used for the leftward AH SA, overriding
automatic assignment using
spi
or
spibase;
typically a hexadecimal number beginning with
0x
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:
Parameters are optional unless marked ``(required)''.
The currently-accepted
parameter
names in a
configsetup
section are:
interfaces
(required)
virtual and physical interfaces for IPsec to use:
a single
virtual=physical pair, a (quoted!) list of pairs separated
by white space,
or
%defaultroute,
which means to find the interface d that the default route points to,
and then act as if the value was ``ipsec0=d''.
(Also, in the
%defaultroute
case,
information about the default route and its interface is noted for
use by
ipsec_manual(8)
and
ipsec_auto(8).)
forwardcontrol
whether
setup
should turn IP forwarding on
(if it's not already on) as IPsec is started,
and turn it off again (if it was off) as IPsec is stopped;
acceptable values are
yes
and (the default)
no.
For this to have full effect, forwarding must be
disabled before the hardware interfaces are brought
up (e.g.,
net.ipv4.ip_forward = 0
in Red Hat 6.x
/etc/sysctl.conf),
because IPsec doesn't get control early enough to do that.
syslog
the
syslog(2)
``facility'' name and priority to use for
startup/shutdown log messages,
default
daemon.err.
klipsdebug
how much KLIPS debugging output should be logged.
An empty value,
or the magic value
none,
means no debugging output (the default).
The magic value
all
means full output.
Otherwise only the specified types of output
(a quoted list, names separated by white space) are enabled;
for details on available debugging types, see
ipsec_klipsdebug(8).
plutodebug
how much Pluto debugging output should be logged.
An empty value,
or the magic value
none,
means no debugging output (the default).
The magic value
all
means full output.
Otherwise only the specified types of output
(a quoted list, names without the
--debug-
prefix,
separated by white space) are enabled;
for details on available debugging types, see
ipsec_pluto(8).
dumpdir
in what directory should things started by
setup
(notably the Pluto daemon) be allowed to
dump core?
The empty value (the default) means they are not
allowed to.
dump
obsolete variant of
dumpdir.
dump=no
is synonymous with
dumpdir=
and
dump=yes
is synonymous with
dump=/var/tmp.
manualstart
which manually-keyed connections to set up at startup
(empty, a name, or a quoted list of names separated by white space);
see
ipsec_manual(8).
Default is none.
pluto
whether to start Pluto or not;
Values are
yes
(the default)
or
no
(useful only in special circumstances).
plutoload
which connections (by name) to load
into Pluto's internal database at startup
(empty, a name, or a quoted list of names separated by white space);
see
ipsec_auto(8)
for details.
Default is none.
If the special value
%search
is used, all connections with
auto=add,
auto=route,
or
auto=start
are loaded.
plutostart
which connections (by name) to attempt to negotiate
at startup (empty, a name, or a quoted
list of names separated by white space);
any such names which do not appear in
plutoload
are implicitly added to it.
Default is none.
If the special value
%search
is used, all connections with
auto=route
or
auto=start
are routed,
and all connections with
auto=start
are started.
plutowait
should Pluto wait for each
plutostart
negotiation attempt to
finish before proceeding with the next?
Values are
yes
(the default)
or
no.
plutobackgroundload
obsolete parameter, ignored, nominally specifying whether
loading and starting of connections should be spun off as a background
process to avoid startup delays.
This is now always done.
Values were
yes
or
no
(the default).
prepluto
shell command to run before starting Pluto
(e.g., to decrypt an encrypted copy of the
ipsec.secrets
file).
It's run in a very simple way;
complexities like I/O redirection are best hidden within a script.
Any output is redirected for logging,
so running interactive commands is difficult unless they use
/dev/tty
or equivalent for their interaction.
Default is none.
postpluto
shell command to run after starting Pluto
(e.g., to remove a decrypted copy of the
ipsec.secrets
file).
It's run in a very simple way;
complexities like I/O redirection are best hidden within a script.
Any output is redirected for logging,
so running interactive commands is difficult unless they use
/dev/tty
or equivalent for their interaction.
Default is none.
fragicmp
whether a tunnel's need to fragment a packet should be reported
back with an ICMP message,
in an attempt to make the sender lower his PMTU estimate;
acceptable values are
yes
(the default)
and
no.
packetdefault
what should be done with
a packet which reaches KLIPS (via a route into a virtual interface)
but does not match any eroute;
acceptable values are
pass
(insecure unless you really know what you're doing!!!),
drop
(the default),
and
reject
(currently same as
drop,
but eventually it will send an ICMP notification back
to the sender).
no_eroute_pass
obsolete parameter similar to
packetdefault
but with more limited functionality;
ignored if
packetdefault
is set;
acceptable values are
yes
(synonymous with
packetdefault=pass)
and
no
(synonymous with
packetdefault=drop)
(the default).
hidetos
whether a tunnel packet's TOS field should be set to
0
rather than copied from the user packet inside;
acceptable values are
yes
(the default)
and
no.
uniqueids
whether a particular participant ID should be kept unique,
with any new (automatically keyed)
connection using an ID from a different IP address
deemed to replace all old ones using that ID;
acceptable values are
yes
and
no
(the default).
overridemtu
value that the MTU of the ipsecn interface(s) should be set to,
overriding IPsec's (large) default.
This parameter is needed only in special situations.
RECOMMENDED CONFIGURATION
Certain parameters are now strongly-recommended defaults,
but cannot (yet) be made system defaults due to backward compatibility.
They are supplied as ``boilerplate'' in the sample
ipsec.conf
file which is put in place as part of a new Openswan install.
Recommended
config setup
parameters are:
plutoload=%search
plutostart=%search
In practice, it is preferable to use the
auto
parameter to control whether a particular
connection is added or started automatically.
uniqueids=yes
Participant IDs normally are unique,
so a new (automatically-keyed) connection using the same ID is
almost invariably intended to replace an old one.
Recommended
conn
parameters (mostly for automatic keying, as manual keying seldom sees
much use) are:
keyingtries=0
Unlimited retries are normally appropriate for VPN connections.
Finite values may be needed for Road Warrior and other more-ephemeral
applications,
but the fixed small default is pretty much useless.
disablearrivalcheck=no
Tunnel-exit checks improve security and do not break any normal configuration.
authby=rsasig
Digital signatures are superior in every way to shared secrets.
leftrsasigkey=%dnsondemand
rightrsasigkey=%dnsondemand
Fetching public keys from DNS is generally more convenient
than having to preconfigure them in configuration files.
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.
In general, the defaults often were chosen for backward compatibility
and are less than ideal.
Notably, the
keyingtries
default should be
0.
Ipsec_manual
is not nearly as generous about the syntax of subnets,
addresses, etc. as the usual FreeS/WAN user interfaces.
Four-component dotted-decimal must be used for all addresses.
It
is
smart enough to translate bit-count netmasks to dotted-decimal form.
It would be good to have a line-continuation syntax,
especially for the very long lines involved in
RSA signature keys.
The ability to specify different identities,
authby,
and public keys for different automatic-keyed connections
between the same participants is misleading;
this doesn't work dependably because the identity of the participants
is not known early enough.
This is especially awkward for the ``Road Warrior'' case,
where the remote IP address is specified as
0.0.0.0,
and that is considered to be the ``participant'' for such connections.
In principle it might be necessary to control MTU on an
interface-by-interface basis,
rather than with the single global override that
overridemtu
provides.
A number of features which could be implemented in
both manual and automatic keying
actually are not yet implemented for manual keying.
This is unlikely to be fixed any time soon.
If conns are to be added before DNS is available,
left=FQDN,
leftnextop=FQDN,
and
leftrsasigkey=%dnsonload
will fail.
ipsec_pluto(8)
does not actually use the public key for our side of a conn but it
isn't generally known at a add-time which side is ours (Road Warrior
and Opportunistic conns are currently exceptions).
