Commit 4a8534d9 authored by Tomek Mrugalski's avatar Tomek Mrugalski 🛰

[master] Merge branch 'trac3209' (user_chk described in the User's Guide)

parents df5031e6 45b33768
......@@ -35,7 +35,7 @@
<para>
The next section describes how to configure hooks libraries. If you
are interested in writing your own hooks library, information can be
found in the <ulink url="http://git.kea.isc.org/~tester/kea/doxygen">Kea
found in the <ulink url="https://jenkins.isc.org/job/Fedora20_32_doxygen_doc/doxygen/">Kea
Developer's Guide</ulink>.
</para>
</section> <!-- end Introduction -->
......@@ -78,9 +78,9 @@
<note><para>
This is a change to the syntax used in Kea 0.9.2 and earlier, where
hooks-libraries was a list of strings, each string being the name of
a library. The change has been made in Kea 1.0 to facilitate the
specification of library-specific parameters, a feature that will be
added to a future version of Kea.
a library. The change was made in Kea 1.0 to facilitate the
specification of library-specific parameters, a capability
available in Kea 1.1.0 onwards.
</para></note>
<note>
......@@ -142,24 +142,211 @@
<section>
<title>Available Hooks Libraries</title>
<para>
As described above the hooks functionality provides a way to customize
As described above, the hooks functionality provides a way to customize
a Kea server without modifying the core code. ISC has chosen to take
advantage of this feature to provide functions that may not be useful
to all users. To this end ISC has created some hooks libraries which
are discussed in the following sections.
advantage of this feature to provide functions that may only be useful
to a subset of Kea users. To this end ISC has created some hooks
libraries; these discussed in the following sections.
</para>
<note><para>
Some of these libraries will be available with the base code while others
will be shared with organizations supporting development of Kea
, possibly as a 'benefit' or 'thank you' for helping to sustain
the larger Kea project. If you would like to get access to those
libraries, please consider taking out a support contract: this includes
professional support, advance security notifications, input into our
roadmap planning, and many other benefits, while helping
making Kea sustainable in the long term.
</para></note>
<para>Currently the following libraries are available or planned from ISC:
<table frame="all" id="hook-libs">
<title>List of available hooks libraries</title>
<tgroup cols='3'>
<colspec colname='name' />
<colspec colname='avail' />
<colspec colname='description' />
<thead>
<row>
<entry>Name</entry>
<entry>Availability</entry>
<entry>Since</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>user_chk</entry>
<entry>Kea sources</entry>
<entry>Kea 0.8</entry>
<entry>Reads known users list from a file. Unknown users
will be assigned a
lease from the last subnet defined in the configuration file,
e.g. to redirect them a captive portal. This demonstrates how an
external source of information can be used to influence the Kea
allocation engine. This hook is part of the Kea source code and is
available in the src/hooks/dhcp/user_chk directory.</entry>
</row>
<row>
<entry>Forensic Logging</entry>
<entry>Support customers</entry>
<entry>Kea 1.1.0</entry>
<entry>This library provides hooks that record a detailed log of
lease assignments and renewals into a set of log files. In many
legal jurisdictions companies, especially ISPs, must record
information about the addresses they have leased to DHCP
clients. This library is designed to help with that
requirement. If the information that it records is sufficient it
may be used directly. If your jurisdiction requires that you save
a different set of information, you may use it as a template or
example and create your own custom logging hooks.</entry>
</row>
<row>
<entry>Lightweight 4over6</entry>
<entry>Support customers</entry>
<entry>Autumn 2016</entry>
<entry>Lightweight 4over6
(<ulink url="http://tools.ietf.org/html/rfc7596">RFC 7596</ulink>)
is a new IPv6 transition
technology that provides IPv4 as a service in IPv6-only
network. It assumes that dual-stack clients will get a regular IPv6
address and IPv6 prefix, but only a fraction of an IPv4 address. The
fraction is specified as port-set, which is essentially a range of
TCP and UDP ports a client can use. By doing the transition on the
client side, this technology eliminates the need to deploy
expensive Carrier Grade NATs within the operator's network. The
problem on the DHCP side is the non-trivial logic behind it: each
client needs to receive an unique set of lightweight 4over6 options
(<ulink url="http://tools.ietf.org/html/rfc7598">RFC 7598</ulink>),
that include the IPv4 address (shared among several
clients), port-set (which is unique among clients sharing the same
IPv4 address) and a number of additional parameters. This hooks
library will generate values of those options dynamically, thus
eliminating the need to manually configure values for each client
separately.
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
Some of these libraries will be available with the base code while
others will only be available via a support contract.
ISC hopes to see more hooks libraries become available as time
progresses, both developed internally and externally. Since
this list may evolve dynamically, we decided to keep it on a
wiki page, available at this link: <ulink
url="http://kea.isc.org/wiki/Hooks">http://kea.isc.org/wiki/Hooks</ulink>.
If you are a developer or are aware of any hooks libraries not
listed there, please send a note to the kea-users or kea-dev
mailing lists and someone will update it.
</para>
<section>
<title>user_chk: Checking User Access</title>
<para>
The user_chk library is the first hooks library published by ISC. It
attempts to serve several purposes:
<itemizedlist>
<listitem>
<para>To assign "new" or "unregistered" users to a
restricted subnet, while "known" or "registered" users are assigned
to unrestricted subnets.</para>
</listitem>
<listitem>
<para>To allow DHCP response options or vendor option
values to be customized based upon user identity. </para>
</listitem>
<listitem>
<para>To provide a real time record of the user registration
activity which can be sampled by an external consumer.</para>
</listitem>
<listitem>
<para> To serve as a demonstration of various capabilities
possible using the hooks interface.</para>
</listitem>
</itemizedlist>
</para>
<para>
Once loaded, the library allows segregating incomings requests into
known and unknown clients. For known clients, the packets are
processed mostly as usual, except it is possible to override certain
options being sent. That can be done on a per host basis. Clients
that are not on the known hosts list will be treated as unknown and
will be assigned to the last subnet defined in the configuration file.
</para>
<para>
As an example of use, this behavior may be used to put unknown users into a
separate subnet that leads to a walled garden, where they can only
access a registration portal. Once they fill in necessary data, their
details are added to the known clients file and they get a proper
address after their device is restarted.
</para>
<note><para>This library was developed several years before the host
reservation mechanism has become available. Currently host reservation is
much more
powerful and flexible, but nevertheless the user_chk capability to consult
and external source of information about clients and alter Kea's
behavior is useful and remains of educational value.
</para></note>
<para>
The library reads the /tmp/user_chk_registry.txt file while being
loaded and each time an incoming packet is processed. The file is expected
to have each line contain a self-contained JSON snippet which must
have the following two entries:
<itemizedlist>
<listitem><para><command>type</command>, whose value
is "HW_ADDR" for IPv4 users or "DUID" for IPv6
users</para></listitem>
<listitem><para><command>id</command>, whose value is
either the hardware address or the DUID from the equest
formatted as a string of hex digits, with or without
":" delimiters.</para></listitem>
</itemizedlist>
and may have the zero or more of the following entries:
<itemizedlist>
<listitem><para><command>bootfile</command> whose value
is the pathname of the desired file</para></listitem>
<listitem><para><command>tftp_server</command> whose
value is the hostname or IP address of the desired
server</para></listitem>
</itemizedlist>
A sample user registry file is shown below:
<screen>{ "type" : "HW_ADDR", "id" : "0c:0e:0a:01:ff:04", "bootfile" : "/tmp/v4bootfile" }
{ "type" : "HW_ADDR", "id" : "0c:0e:0a:01:ff:06", "tftp_server" : "tftp.v4.example.com" }
{ "type" : "DUID", "id" : "00:01:00:01:19:ef:e6:3b:00:0c:01:02:03:04", "bootfile" : "/tmp/v6bootfile" }
{ "type" : "DUID", "id" : "00:01:00:01:19:ef:e6:3b:00:0c:01:02:03:06", "tftp_server" : "tftp.v6.example.com" }</screen>
</para>
<para>As with any other hooks libraries provided by ISC, internals of the
user_chk code are well documented. You can take a look at the <ulink
url="https://jenkins.isc.org/job/Fedora20_32_doxygen_doc/doxygen/d8/db2/libdhcp_user_chk.html">Kea Developer's Guide section dedicated to the user_chk library</ulink>
that discusses how the code works internally. That, together with
our general entries in <ulink
url="https://jenkins.isc.org/job/Fedora20_32_doxygen_doc/doxygen/">Hooks
Framework section</ulink> should give you some pointers how to extend
this library and perhaps even write your own from scratch.</para>
</section>
<section>
<title>Forensic Logging Hooks</title>
<para>
This section describes the forensic log hooks library. This library
povides hooks that record a detailed log of lease assignments
and renewals into a set of log files. Currently this library
is only available to customers with a support contract.
is only available to ISC customers with a support contract.
</para>
<para>
In many legal jurisdictions companies, especially ISPs, must record
......
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