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strongSwan - Installation
1. Overview
2. Required packages
3. Optional packages
3.1 libcurl
3.2 OpenLDAP
3.3 PKCS#11 smartcard library modules
4. Kernel configuration
1. Overview
The strongSwan 4.x branch introduces a new build environment featuring
GNU autotools. This should simplify the build process and package
First check for the availability of required packages on your system
(section 2.). You may want to include support for additional features, which
require other packages to be installed (section 3.).
To compile an extracted tarball, run the ./configure script first:
You may want to specify some arguments listed in section 3., or see the
available options of the script using "./configure --help".
After a successful run of the script, run
followed by
make install
in the usual manner.
To check if your kernel fullfills the requirements, see section 4.
Next add your connections to "/etc/ipsec.conf" and your secrets to
"/etc/ipsec.secrets". Connections that are to be negotiated by the new
IKEv2 charon keying daemon should be designated by "keyexchange=ikev2" and
those by the IKEv1 pluto keying daemon either by "keyexchange=ikev1" or
the default "keyexchange=ike".
At last start strongSwan with
ipsec start
2. Required packages
In order to be able to build strongSwan you'll need the GNU Multiprecision
Arithmetic Library (GMP) available from At least
version 4.1.5 of libgmp is required.
The libgmp library and the corresponding header file gmp.h are usually
included in the form of one or two packages in the major Linux
distributions (SuSE: gmp; Debian unstable: libgmp3, libgmp3-dev).
3. Optional packages
3.1 libcurl
If you intend to dynamically fetch Certificate Revocation Lists (CRLs)
from an HTTP server or as an alternative want to use the Online
Certificate Status Protocol (OCSP) then you will need the libcurl library
available from
In order to keep the library as compact as possible for use with strongSwan
you can build libcurl from the sources with the optimized options
./configure --prefix=<dir> --without-ssl \
--disable-ldap --disable-telnet \
--disable-dict --disable-gopher \
--disable-debug \
--enable-nonblocking --enable-thread
As an alternative you can use the ready-made packages included with your
favorite Linux distribution (SuSE: curl, curl-devel).
In order to activate the use of the libcurl library in strongSwan you must
enable the ./configure switch:
./configure [...] --enable-http
3.2 OpenLDAP
If you intend to dynamically fetch Certificate Revocation Lists (CRLs)
from an LDAP server then you will need the libldap library available
OpenLDAP is usually included with your Linux distribution. You will need
both the run-time and development environments (SuSE: openldap2,
In order to activate the use of the libldap library in strongSwan you must
enable the ./configure switch:
./configure [...] --enable-ldap
LDAP Protocl version 2 is not supported anymore, --enable-ldap uses always
version 3 of the LDAP protocol
3.3 PKCS#11 smartcard library modules
If you want to securely store your X.509 certificates and private RSA keys
on a smart card or a USB crypto token then you will need a PKCS #11 library
for the smart card of your choice. The OpenSC PKCS#11 library (use
versions >= 0.9.4) available from supports quite a
selection of cards and tokens (e.g. Aladdin eToken Pro32k, Schlumberger
Cryptoflex e-gate, Oberthur AuthentIC, etc.) but requires that a PKCS#15
directory structure be present on the smart card. But in principle
any other PKCS#11 library could be used since the PKCS#11 API hides the
internal data representation on the card.
For USB crypto token support you must add the OpenCT driver library
(version >= 0.6.2) from the OpenSC site, whereas for serial smartcard
readers you'll need the pcsc-lite library and the matching driver from the
M.U.S.C.L.E project .
In order to activate the PKCS#11-based smartcard support in strongSwan
you must enable the smartcard ./configure switch:
./configure [...] --enable-smartcard
During compilation no externel smart card libraries must be present.
strongSwan directly references a copy of the standard RSAREF pkcs11.h
header files stored in the pluto/rsaref sub directory. During compile
time a pathname to a default PKCS#11 dynamical library can be specified
with a ./configure flag:
./configure --enable-smartcard --with-default-pkcs11=/path/to/
This default path to the easily-obtainable OpenSC library module can be
simply overridden during run-time by specifying an alternative path in
ipsec.conf pointing to any dynamic PKCS#11 library of your choice.
config setup
4. Kernel configuration
The strongSwan 4.x series currently support only 2.6 kernels and its
native IPsec stack. Please make sure that the following IPsec kernel
modules are available:
o af_key
o ah4
o esp4
o ipcomp
o xfrm_user
o xfrm4_tunnel
These may be built into the kernel or as modules. Modules get loaded
automatically at strongSwan startup.
Also the built-in kernel Cryptoapi modules with selected encryption and
hash algorithms should be available.