isakmpd - ISAKMP/Oakley a.k.a. IKE key management daemon
isakmpd [-4] [-6] [-c config-file] [-a] [-d] [-D class=level] [-f fifo]
[-i pid-file] [-n] [-p listen-port] [-P local-port] [-K] [-L]
[-l packetlog-file] [-r seed] [-R report-file] [-v]
The isakmpd daemon establishes security associations for encrypted and/or
authenticated network traffic. At this moment, and probably forever,
this means ipsec(4) traffic.
The way isakmpd goes about its work is by maintaining an internal
configuration as well as a policy database which describes what kinds of
SAs to negotiate, and by listening for different events that trigger
these negotiations. The events that control isakmpd consist of
negotiation initiations from a remote party, user input via a FIFO or by
signals, upcalls from the kernel via a PF_KEY socket, and lastly by
scheduled events triggered by timers running out.
Most uses of isakmpd will be to implement so called "virtual private
networks" or VPNs for short. The vpn(8) manual page describes how to set
up isakmpd for a simple VPN. For other uses, some more knowledge of IKE
as a protocol is required. One source of information are the RFCs
On startup isakmpd forks into two processes for privilege separation.
The unprivileged child jails itself with chroot(8) to /var/empty. The
privileged process communicates with the child, reads configuration files
and PKI information and binds to privileged ports on its behalf. See
CAVEATS section below.
The options are as follows:
-4 | -6
These options control what address family (AF_INET and/or
AF_INET6) isakmpd will use. The default is to use both IPv4 and
-a If given, isakmpd does not set up flows automatically. This is
useful when flows are configured with ipsecadm(4) or by other
programs like bgpd(8). Thus isakmpd only takes care of the SA
If given, the -c option specifies an alternate configuration file
instead of /etc/isakmpd/isakmpd.conf. As this file may contain
sensitive information, it must be readable only by the user
running the daemon. isakmpd will reread the configuration file
when sent a SIGHUP signal.
-d The -d option is used to make the daemon run in the foreground,
logging to stderr.
Debugging class. It’s possible to specify this argument many
times. It takes a parameter of the form class=level, where both
class and level are numbers. class denotes a debugging class,
and level the level you want that debugging class to limit debug
printouts at (i.e., all debug printouts above the level specified
will not output anything). If class is set to ‘A’, then all
debugging classes are set to the specified level.
Valid values for class are as follows:
10 FIFO user interface
Currently used values for level are 0 to 99.
The -f option specifies the FIFO (a.k.a. named pipe) where the
daemon listens for user requests. If the path given is a dash
(‘-’), isakmpd will listen to stdin instead.
By default the PID of the daemon process will be written to
/var/run/isakmpd.pid. This path can be overridden by specifying
another one as the argument to the -i option.
-n When the -n option is given, the kernel will not take part in the
negotiations. This is a non-destructive mode, so to speak, in
that it won’t alter any SAs in the IPsec stack.
The -p option specifies the listen port the daemon will bind to.
On the other hand, the port specified to capital -P will be what
the daemon binds its local end to when acting as initiator.
-K When this option is given, isakmpd does not read the policy
configuration file and no keynote(4) policy check is
accomplished. This option can be used when policies for flows
and SA establishment are arranged by other programs like
ipsecadm(8) or bgpd(8).
-L Enable IKE packet capture. When this option is given, isakmpd
will capture to file an unencrypted copy of the negotiation
packets it is sending and receiving. This file can later be read
by tcpdump(8) and other utilities using pcap(3).
As option -L above, but capture to a specified file.
If given, a deterministic random number sequence will be used
internally. This is useful for setting up regression tests.
When you signal isakmpd a SIGUSR1, it will report its internal
state to a report file, normally /var/run/isakmpd.report, but
this can be changed by feeding the file name as an argument to
the -R flag.
-v Enables verbose logging. Normally, isakmpd is silent and outputs
only messages when a warning or an error occurs. With verbose
logging isakmpd reports successful completion of phase 1 (Main
and Aggressive) and phase 2 (Quick) exchanges (Information and
Transaction exchanges do not generate any additional status
Setting up an IKE public key infrastructure (a.k.a. PKI)
In order to use public key based authentication, there has to be an
infrastructure managing the key signing. Either there is an already
existing PKI isakmpd should take part in, or there will be a need to set
one up. In the former case, what is needed to be done varies depending
on the actual Certificate Authority used, and is therefore not covered
here, other than mentioning that openssl(1) needs to be used to create a
certificate signing request that the CA understands. The latter case,
however, is described here:
1. Create your own CA as root.
# openssl genrsa -out /etc/ssl/private/ca.key 1024
# openssl req -new -key /etc/ssl/private/ca.key \
You are then asked to enter information that will be incorporated
into your certificate request. What you are about to enter is what
is called a Distinguished Name (DN). There are quite a few fields
but you can leave some blank. For some fields there will be a
default value; if you enter ‘.’, the field will be left blank.
# openssl x509 -req -days 365 -in /etc/ssl/private/ca.csr \
-signkey /etc/ssl/private/ca.key \
-extfile /etc/ssl/x509v3.cnf -extensions x509v3_CA \
2. Create keys and certificates for your IKE peers. This step as well
as the next one, needs to be done for every peer. Furthermore the
last step will need to be done once for each ID you want the peer to
have. The 10.0.0.1 below symbolizes that ID, in this case an IPv4
ID, and should be changed for each invocation. You will be asked
for a DN for each run. Encoding the ID in the common name is
recommended, as it should be unique.
# openssl genrsa -out /etc/isakmpd/private/local.key 1024
# openssl req -new -key /etc/isakmpd/private/local.key \
Now take these certificate signing requests to your CA and process
them like below. You have to add a subjectAltName extension field
to the certificate in order to make it usable by isakmpd. There are
two possible ways to add the extensions to the certificate. Either
you have to run certpatch(8) or you have to make use of an OpenSSL
configuration file, for example /etc/ssl/x509v3.cnf. Replace
10.0.0.1 with the IP-address which isakmpd will use as the
To use certpatch(8), do the following
# openssl x509 -req -days 365 -in 10.0.0.1.csr -CA /etc/ssl/ca.crt \
-CAkey /etc/ssl/private/ca.key -CAcreateserial \
# certpatch -i 10.0.0.1 -k /etc/ssl/private/ca.key \
# setenv CERTIP 10.0.0.1
# openssl x509 -req -days 365 -in 10.0.0.1.csr -CA /etc/ssl/ca.crt \
-CAkey /etc/ssl/private/ca.key -CAcreateserial \
-extfile /etc/ssl/x509v3.cnf -extensions x509v3_IPAddr \
For a FQDN certificate, do
# setenv CERTFQDN somehost.somedomain
# openssl x509 -req -days 365 -in somehost.somedomain.csr \
-CA /etc/ssl/ca.crt -CAkey /etc/ssl/private/ca.key \
-extfile /etc/ssl/x509v3.cnf -extensions x509v3_FQDN \
or with certpatch(8)
# certpatch -t fqdn -i somehost.somedomain \
-k /etc/ssl/private/ca.key \
(This assumes the previous steps were used to create a request for
somehost.somedomain instead of 10.0.0.1)
Put the certificate (the file ending in .crt) in /etc/isakmpd/certs/
on your local system. Also carry over the CA cert /etc/ssl/ca.crt
and put it in /etc/isakmpd/ca/.
To revoke certificates, create a Certificate Revocation List (CRL) file
and install it in the /etc/isakmpd/crls/ directory. See openssl(1) and
the ‘crl’ subcommand for more info.
It is also possible to store trusted public keys to make them directly
usable by isakmpd. The keys should be saved in PEM format (see
openssl(1)) and named and stored after this easy formula:
For IPv4 identities /etc/isakmpd/pubkeys/ipv4/A.B.C.D
For IPv6 identities /etc/isakmpd/pubkeys/ipv6/abcd:abcd::ab:bc
For FQDN identities /etc/isakmpd/pubkeys/fqdn/foo.bar.org
For UFQDN identities /firstname.lastname@example.org
The FIFO user interface
When isakmpd starts, it creates a FIFO (named pipe) where it listens for
user requests. All commands start with a single letter, followed by
command-specific options. Available commands are:
Start the named connection, if stopped or inactive.
C set [section]:tag=value
C set [section]:tag=value force
C add [section]:tag=value
C rm [section]:tag
C rms [section]
Update the running isakmpd configuration atomically. ‘set’ sets
a configuration value consisting of a section, tag and value
triplet. ‘set’ will fail if the configuration already contains a
section with the named tag; use the ‘force’ option to change this
behaviour. ‘add’ appends a configuration value to the named
configuration list tag. ‘rm’ removes a tag in a section. ‘rms’
removes an entire section.
NOTE: Sending isakmpd a SIGHUP or an "R" through the FIFO will
void any updates done to the configuration.
C get [section]:tag
Get the configuration value of the specified section and tag.
The result is stored in /var/run/isakmpd.result.
d <cookies> <msgid>
Delete the specified SA from the system. Specify <msgid> as "-"
to match a Phase 1 SA.
D <class> <level>
D A <level>
D T Set debug class <class> to level <level>. If <class> is
specified as "A", the level applies to all debug classes. "D T"
toggles all debug classes to level zero. Another "D T" command
will toggle them back to the earlier levels.
p off Enable or disable cleartext IKE packet capture. When enabling,
optionally specify which file isakmpd should capture the packets
Q Cleanly shutdown the daemon, as when sent a SIGTERM signal.
r Report isakmpd internal state to a file. See -R option. Same as
when sent a SIGUSR1 signal.
R Reinitialize isakmpd, as when sent a SIGHUP signal.
S Report information on all known SAs to the
Tear down the named connection, if active.
T Tear down all active connections.
/etc/isakmpd/ca/ The directory where CA certificates can be
/etc/isakmpd/certs/ The directory where IKE certificates can be
found, both the local certificate(s) and
those of the peers, if a choice to have them
kept permanently has been made.
/etc/isakmpd/crls/ The directory where CRLs can be found.
/etc/isakmpd/isakmpd.conf The configuration file. As this file can
contain sensitive information it must not be
readable by anyone but the user running
/etc/isakmpd/isakmpd.policy The keynote policy configuration file. The
same mode requirements as isakmpd.conf.
A local private key for certificate based
authentication. There has to be a
certificate for this key in the certificate
directory mentioned above. The same mode
requirements as isakmpd.conf.
/etc/isakmpd/pubkeys/ Directory in which trusted public keys can
be kept. The keys must be named in the
fashion described above.
/var/run/isakmpd.pid The PID of the current daemon.
/var/run/isakmpd.fifo The FIFO used to manually control isakmpd.
/var/run/isakmpd.pcap The default IKE packet capture file.
/var/run/isakmpd.report The report file written when SIGUSR1 is
/var/run/isakmpd.result The report file written when the ‘S’ or ‘C
get’ command is issued in the command FIFO.
/usr/share/ipsec/isakmpd/ A directory containing some sample isakmpd
and keynote policy configuration files.
openssl(1), getnameinfo(3), pcap(3), ipsec(4), isakmpd.conf(5),
isakmpd.policy(5), ssl(8), tcpdump(8), vpn(8)
The ISAKMP/Oakley key management protocol is described in the RFCs RFC
2407, RFC 2408 and RFC 2409. This implementation was done 1998 by Niklas
Hallqvist and Niels Provos, sponsored by Ericsson Radio Systems.
When storing a trusted public key for an IPv6 identity, the most
efficient form of address representation, i.e "::" instead of ":0:0:0:",
must be used or the matching will fail. isakmpd uses the output from
getnameinfo(3) for the address-to-name translation. The privileged
process only allows binding to the default port 500 or unprivileged ports
(>1024). It is not possible to change the interfaces isakmpd listens on
without a restart.
The -P flag does not do what we document, rather it does nothing.