Scroll to navigation

ISAKMPD(8) System Manager's Manual ISAKMPD(8)

NAME

isakmpd —
ISAKMP/Oakley a.k.a. IKE key management daemon

SYNOPSIS

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]

DESCRIPTION

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 mentioned below.

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:

|
These options control what address family (AF_INET and/or AF_INET6) isakmpd will use. The default is to use both IPv4 and IPv6.
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 establishment.
config-file
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.
The -d option is used to make the daemon run in the foreground, logging to stderr.
class=level
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:

0
Misc
1
Transport
2
Message
3
Crypto
4
Timer
5
Sysdep
6
SA
7
Exchange
8
Negotiation
9
Policy
10
FIFO user interface
A
All

Currently used values for level are 0 to 99.

fifo
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.
pid-file
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.
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.
listen-port
The -p option specifies the listen port the daemon will bind to.
local-port
On the other hand, the port specified to capital -P will be what the daemon binds its local end to when acting as initiator.
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).
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).
packetlog-file
As option -L above, but capture to a specified file.
seed
If given, a deterministic random number sequence will be used internally. This is useful for setting up regression tests.
report-file
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.
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 information).

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 \
	-out /etc/ssl/private/ca.csr

    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 \
	-out /etc/ssl/ca.crt
  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 \
	-out /etc/isakmpd/private/10.0.0.1.csr

    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 certificate identity.

    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 \
	-out 10.0.0.1.crt
# certpatch -i 10.0.0.1 -k /etc/ssl/private/ca.key \
	10.0.0.1.crt 10.0.0.1.crt

    Otherwise do

    # 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 \
	-out 10.0.0.1.crt

    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 \
	-CAcreateserial \
	-extfile /etc/ssl/x509v3.cnf -extensions x509v3_FQDN \
	-out somehost.somedomain.crt

    or with certpatch(8)

    # certpatch -t fqdn -i somehost.somedomain \
	-k /etc/ssl/private/ca.key \
	somehost.somedomain.crt somehost.somedomain.crt

    (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
/etc/isakmpd/pubkeys/ufqdn/user@foo.bar.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.

 
 
 
 
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.

Get the configuration value of the specified section and tag. The result is stored in /var/run/isakmpd.result.

Delete the specified SA from the system. Specify <msgid> as "-" to match a Phase 1 SA.

 
 
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.

 
Enable or disable cleartext IKE packet capture. When enabling, optionally specify which file isakmpd should capture the packets to.

Cleanly shutdown the daemon, as when sent a SIGTERM signal.

Report isakmpd internal state to a file. See -R option. Same as when sent a SIGUSR1 signal.

Reinitialize isakmpd, as when sent a SIGHUP signal.

Report information on all known SAs to the /var/run/isakmpd.result file.

Tear down the named connection, if active.

Tear down all active connections.

FILES

/etc/isakmpd/ca/
The directory where CA certificates can be found.
/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 isakmpd.
/etc/isakmpd/isakmpd.policy
The keynote policy configuration file. The same mode requirements as isakmpd.conf.
/etc/isakmpd/private/local.key
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 received.
/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.

SEE ALSO

openssl(1), getnameinfo(3), pcap(3), ipsec(4), isakmpd.conf(5), isakmpd.policy(5), ssl(8), tcpdump(8), vpn(8)

HISTORY

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.

CAVEATS

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.

BUGS

The -P flag does not do what we document, rather it does nothing.
August 7, 2002 Linux 4.19.0-10-amd64