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IKE keying daemon charon » History » Version 4

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Martin Willi, 31.03.2008 17:06


= 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 | //////
----------- -----------
}}}

||'''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.|| ||'''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.|| ||'''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.|| ||'''IKE_SA'''||The IKE_SA contain the state and the logic of each IKE_SA and handle the messages.|| ||'''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.|| ||'''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. || ||'''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.|| ||'''Controller'''||The controller provides a simple API for plugins to control the daemon (e.g. initiate IKE_SA, close IKE_SA, ...).|| ||'''Backends'''||Backends are pluggable modules which provide configuration. They have to implement an API which the daemon core uses to get configuration.

Plugins

The daemon loads plugins at startup. These implement the 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:
'''stroke''' The stroke plugin loads credentials from ''/etc/ipsec.d'', reads ''ipsec.secrets'' and accepts configurations and control commands from ipsec starter.
'''smp''' The smp plugin implements the [wiki:SMP] protocol to control and query the daemon using an XML interface.
'''sql''' The sql plugin provides credentials and configurations from a relational database, see [wiki:SQL].
'''eap_aka''' Implements the AKA EAP module implemented completely in software.
'''eap_sim''' Implements the SIM EAP module using either a triplet file or a third party card reader library.
'''eap_md5''' Implements the MD5 EAP module (CHAP).
'''eap_identity''' EAP helper module to serve an Identity over EAP before doing EAP authentication.