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IKE keying daemon charon » History » Version 8

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Martin Willi, 23.06.2008 09:33


= IKEv2 keying daemon charon =

The ''charon'' keying daemon was built from scratch to implement the IKEv2 protocol for strongSwan.
It has a fully multi-threaded design to meet todays requirements.

Architecture {{{
------------------------------- -------------------------- | Credentials | | Backends |
------------------------------- -------------------------- ---------- --------- ---- -------- | receiver | | | | | ---- | CHILD_SA |
---------+ | Scheduler | | IKE- | | IKE- |--+----------+ | | | | SA |--| SA | | CHILD_SA |
-------+ --------- | | ---- --------
<->| socket | | | Man- |
-------+ --------- | ager | ---- -------- | | | | | | IKE- |--| CHILD_SA |
---------+ | Processor |--------| |--| SA | -------- | sender | | | | | ----
---------- --------- ---- ------------------------------- -------------------------- | Bus | | Kernel Interface |
------------------------------- -------------------------- | | |
----------- ----------- V | File-Logger | | Sys-Logger | //////
----------- -----------
}}}

||[browser:trunk/src/charon/processing/processor.h Processor]||The threading is realized with the help of a thread pool (called processor), which contains a fixed amount of precreated threads. All threads in the daemon originate from the processor. To delegate work to a thread, jobs are queued to the processor for asynchronous execution.|| ||[browser:trunk/src/charon/processing/scheduler.h Scheduler]||The scheduler is responsible to execute timed events. Jobs may be queued to the scheduler to get executed at a defined time (e.g. rekeying). The scheduler does not execute the jobs itself, it queues them to the processor.|| ||[browser:trunk/src/charon/sa/ike_sa_manager.h IKE_SA Manager]||The IKE_SA manager managers all IKE_SA. It further handles the synchronization: Each IKE_SA must be checked out strictly and checked in again after use. The manager guarantees that only one thread may check out a single IKE_SA. This allows us to write the (complex) IKE_SAs routines non-threadsave.|| ||[browser:trunk/src/charon/sa/ike_sa.h IKE_SA]||The IKE_SA contain the state and the logic of each IKE_SA and handle the messages.|| ||[browser:trunk/src/charon/sa/child_sa.h CHILD_SA]||The CHILD_SA contains state about a IPsec security association and manages them. An IKE_SA may have multiple CHILD_SAs. Communication to the kernel takes place here through the kernel interface.|| ||[browser:trunk/src/charon/kernel/kernel_interface.h Kernel Interface]||The kernel interface installs IPsec security associations, policies routes and virtual addresses. It further provides methods to numerate interfaces and may notify the daemon about state changes at lower layers. || ||[browser:trunk/src/charon/bus/bus.h Bus]||The bus receives signals from the different threads and relais them to interested listeners. Debugging signals, but also important state changes or error messages are sent over the bus.|| ||[browser:trunk/src/charon/control/controller.h Controller]||The controller provides a simple API for plugins to control the daemon (e.g. initiate IKE_SA, close IKE_SA, ...).|| ||[browser:trunk/src/charon/config/backend_manager.h Backends]||Backends are pluggable modules which provide configuration. They have to implement an API which the daemon core uses to get configuration. ||[browser:trunk/src/charon/credentials/credential_manager.h Credentials]||Provides trustchain verification and credential serving using registered plugins.

Plugins

The daemon loads plugins at startup. These implement the [browser:trunk/src/libstrongswan/plugins/plugin.h plugin_t] interface. Each plugin registers itself at the daemon to hook in functionality.

{{{
----------------------------------- | charon -- ----------+ | | | | stroke | | | | ---------+ | ----------- | | ---------+ | | bus | ----> | p | | smp | | ----------- | l | ---------+ | ----------- <---- | u | ---------+ | | controller | | g | | sql | | ----------- ----> | i | ---------+ | ----------- | n | ---------+ | | credentials | <---- | | | eap_aka | | ----------- | l | ---------+ | ----------- ----> | o | ---------+ | | backends | | a | | eap_sim | | ----------- <---- | d | ---------+ | ----------- | e | ---------+ | | eap | ----> | r | | eap_md5 | | ----------- | | ---------+ | | | ---------+ | | | |eap_identity| | -- ----------+
-----------------------------------
}}}

There is a growing list of available plugins:
[browser:trunk/src/charon/plugins/stroke stroke] The stroke plugin loads credentials from ''/etc/ipsec.d'', reads ''ipsec.secrets'' and accepts configurations and control commands from ipsec starter.
[browser:trunk/src/charon/plugins/smp smp] The smp plugin implements the [wiki:SMP] protocol to control and query the daemon using an XML interface.
[browser:trunk/src/charon/plugins/sql sql] The sql plugin provides credentials and configurations from a relational database, see [wiki:SQL].
[browser:trunk/src/charon/plugins/eap_aka eap_aka] Implements the AKA EAP module implemented completely in software.
[browser:trunk/src/charon/plugins/eap_sim eap_sim] Implements the SIM EAP module using either a triplet file or a third party card reader library.
[browser:trunk/src/charon/plugins/eap_md5 eap_md5] Implements the MD5 EAP module (CHAP).
[browser:trunk/src/charon/plugins/eap_identity eap_identity] EAP helper module to serve an Identity over EAP before doing EAP authentication.
[browser:trunk/src/charon/plugins/medcli medcli] Reads mediation/mediated connections for a client from a simple database.
[browser:trunk/src/charon/plugins/medsrv medsrv] Reads mediation connections for a mediation server from a simple database.
[browser:trunk/src/charon/plugins/uci uci] OpenWRT UCI configuration backend.
[browser:trunk/src/charon/plugins/unit_tester unit_tester] Simple unit testing framework for charon and libstrongswan.