- unstable 20041012-10+b1
|ISAKMPD(8)||System Manager's Manual||ISAKMPD(8)|
ISAKMP/Oakley a.k.a. IKE key management daemon
isakmpd daemon establishes security
associations for encrypted and/or authenticated network traffic. At this
moment, and probably forever, this means ipsec(4)
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
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.
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 (
isakmpdwill use. The default is to use both IPv4 and IPv6.
- If given,
isakmpddoes not set up flows automatically. This is useful when flows are configured with ipsecadm(4) or by other programs like bgpd(8). Thus
isakmpdonly takes care of the SA establishment.
- If given, the
-coption 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.
isakmpdwill reread the configuration file when sent a
-doption 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
Valid values for class are as follows:
- FIFO user interface
Currently used values for level are 0 to 99.
-foption specifies the FIFO (a.k.a. named pipe) where the daemon listens for user requests. If the path given is a dash (‘-’),
isakmpdwill 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
- When the
-noption 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.
-poption specifies the listen port the daemon will bind to.
- On the other hand, the port specified to capital
-Pwill be what the daemon binds its local end to when acting as initiator.
- When this option is given,
isakmpddoes 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,
isakmpdwill 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
-Labove, 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
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
- Enables verbose logging. Normally,
isakmpdis silent and outputs only messages when a warning or an error occurs. With verbose logging
isakmpdreports 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
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:
- 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
- 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
isakmpdwill 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
# 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
- For IPv6 identities
- For FQDN identities
- For UFQDN identities
The FIFO user interface¶
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
- 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
isakmpdconfiguration 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>
- 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
isakmpdshould capture the packets to.
- Cleanly shutdown the daemon, as when sent a
isakmpdinternal state to a file. See
-Roption. Same as when sent a
isakmpd, as when sent a
- 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.
- The directory where CA certificates can be found.
- 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.
- The directory where CRLs can be found.
- The configuration file. As this file can contain sensitive information it
must not be readable by anyone but the user running
- The keynote policy configuration file. The same mode requirements as
- 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
- Directory in which trusted public keys can be kept. The keys must be named in the fashion described above.
- The PID of the current daemon.
- The FIFO used to manually control
- The default IKE packet capture file.
- The report file written when
- The report file written when the ‘S’ or ‘C get’ command is issued in the command FIFO.
- A directory containing some sample
isakmpdand keynote policy configuration files.
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
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.
-P flag does not do what we document,
rather it does nothing.
|August 7, 2002||Debian|