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Code Issues Releases Wiki Activity

[#2113] Added doc from tests and in particular with AD

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This commit is contained in:
Francis Dupont
2021-10-03 23:39:55 +02:00
parent edfc041764
commit 0729096b76
1 changed files with 137 additions and 19 deletions
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156
doc/sphinx/arm/ext-gss-tsig.rst
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@@ -10,7 +10,7 @@ GSS-TSIG
.. note::
The GSS-TSIG feature is considered experimental. It is possible to perform
the key exchanges and sign the DNS updates using GSS-TSIG, but some error
the TKEY exchanges and sign the DNS updates using GSS-TSIG, but some error
handling and fallback scenarios are not covered yet. Use with caution.
GSS-TSIG Overview
@@ -19,7 +19,7 @@ GSS-TSIG Overview
Kea provides a support for DNS updates, which can be protected using
Transaction Signatures (or TSIG). This protection is often adequate.
However some systems, in particular Active Directory (AD) on Microsoft
Windows systems, chose to adopt more complex GSS-TSIG approach that offers
Windows servers, chose to adopt more complex GSS-TSIG approach that offers
additional capabilities as using negotiated dynamic keys.
Kea provides the support of GSS-TSIG to protect DNS updates sent by
@@ -286,21 +286,6 @@ If succesfully created, the following message will be displayed:
Authenticating as principal root/admin@EXAMPLE.ORG with password.
Principal "DNS/server.example.org@EXAMPLE.ORG" created.
The DNS client principal (used by the Kea DDNS server) is created the
following way (please choose your own password here):
.. code-block:: console
kadmin.local -q "addprinc -pw <password> DHCP/admin.example.org"
If succesfully created, the following message will be displayed:
.. code-block:: console
No policy specified for DHCP/admin.example.org@EXAMPLE.ORG; defaulting to no policy
Authenticating as principal root/admin@EXAMPLE.ORG with password.
Principal "DHCP/admin.example.org@EXAMPLE.ORG" created.
The DNS server principal must be exported so that it can be used by the Bind 9
DNS server. Only this principal is required and is is exported to the keytab
file with the name ``dns.keytab``.
@@ -317,6 +302,29 @@ If succesfully exported, the following message will be displayed:
Entry for principal DNS/server.example.org with kvno 2, encryption type aes256-cts-hmac-sha1-96 added to keytab WRFILE:/tmp/dns.keytab.
Entry for principal DNS/server.example.org with kvno 2, encryption type aes128-cts-hmac-sha1-96 added to keytab WRFILE:/tmp/dns.keytab.
The DHCP client principal (used by the Kea DDNS server) is created the
following way:
.. code-block:: console
kadmin.local -q "addprinc -randkey DHCP/admin.example.org"
If succesfully created, the following message will be displayed:
.. code-block:: console
No policy specified for DHCP/admin.example.org@EXAMPLE.ORG; defaulting to no policy
Authenticating as principal root/admin@EXAMPLE.ORG with password.
Principal "DHCP/admin.example.org@EXAMPLE.ORG" created.
The DHCP client principal must be exported so that it can be used by the
DHCP-DDNS server and GSS-TSIG hook library. It is exported to the client
keytab file with the name ```dhcp.keytab```.
.. code-block:: console
kadmin.local -q "ktadd -k /tmp/dhcp.keytab DHCP/admin.example.org"
Finally, the krb5-admin-server must be restarted:
.. code-block:: console
@@ -336,6 +344,7 @@ Updating the ``named.conf`` file is required:
...
directory "/var/cache/bind";
dnssec-validation auto;
listen-on-v6 { any; };
tkey-gssapi-keytab "/etc/bind/dns.keytab";
};
zone "example.org" {
@@ -392,6 +401,54 @@ The ``/var/lib/bind/db.example.org`` file needs to be created or updated:
kdc A ${KDC_IP_ADDR}
server A ${BIND9_IP_ADDR}
As after any configuration change the server must be reloaded or
restarted:
.. code-block:: console
systemctl restart named.service
It is possible to get status or restart logs:
.. code-block:: console
systemctl status named.service
journalctl -u named | tail -n 30
Windows Advanced Directory Configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This sub-section is based on an Amazon AWS provided Microsoft Windows Server
2016 with Active Directory pre-installed so describes only the steps used
for GSS-TSIG deployment (more exactly as other parts of the deployment and
using sections what the QA ISC department uses for internal tests).
Two Active Directory (AD) user accounts are needed:
- the first account is used to download AD information, for instance
the client key table of Kea
- the second account will be mapped to the Kea DHCP client principal
Kea needs to know:
- the server IP address
- the domain/realm name: the domain is in lower case, the realm in upper
case, both without a final dot
- the server name
The second account (named ``kea`` below) is used to create a Service
Principal Name (SPN):
.. code-block:: console
setspn -S DHCP/kea.<domain> kea
After a shared secret key is generated and put in a key table file:
.. code-block:: console
ktpass -princ DHCP/kea.<domain>@<REALM> -mapuser kea +rndpass -mapop set -ptype KRB5_NT_PRINCIPAL -out dhcp.keytab
The ```dhcp.keytab`` takes the same usage as for Unix Kerberos.
.. _gss-tsig-using:
Using GSS-TSIG
@@ -407,7 +464,7 @@ An excerpt from D2 server is provided below. More examples are available in the
.. code-block:: javascript
:linenos:
:emphasize-lines: 57-97
:emphasize-lines: 57-99
{
"DhcpDdns": {
@@ -477,7 +534,7 @@ An excerpt from D2 server is provided below. More examples are available in the
"server-principal": "DNS/server.example.org@EXAMPLE.ORG",
"client-principal": "DHCP/admin.example.org@EXAMPLE.ORG",
"client-keytab": "FILE:/etc/krb5.keytab", // toplevel only
"client-keytab": "FILE:/etc/dhcp.keytab", // toplevel only
"credentials-cache": "FILE:/etc/ccache", // toplevel only
"tkey-lifetime": 3600,
"tkey-protocol": "TCP",
@@ -615,6 +672,67 @@ The server map parameters are:
- ``comment`` is allowed but currently ignored.
GSS-TSIG Configuration for Deployment
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When using the Kerberos 5 and Bind9 setup of :ref:`gss-tsig-deployment`
the local resolver must point to the Bind9 named server address and
local Kerberos be configured by putting in the ``krb5.conf`` file:
.. code-block:: ini
[libdefaults]
default_realm = EXAMPLE.ORG
kdc_timesync = 1
ccache_type = 4
forwardable = true
proxiable = true
[realms]
EXAMPLE.ORG = {
kdc = kdc.example.org
admin_server = kdc.example.org
}
With Windows AD the DNS service is provided by AD. AD also provides
the Kerberos service and the ``krb5.conf`` file becomes:
.. code-block:: ini
[libdefaults]
default_realm = <REALM>
kdc_timesync = 1
ccache_type = 4
forwardable = true
proxiable = true
[realms]
${REALM} = {
kdc = <AD_IP_ADDR>
admin_server = <AD_IP_ADDR>
}
Even when the GSS-API library can use the secret from the client key
table it is far better to get and cache credentials.
This can be done manually by:
.. code-block:: console
kinit -k -t /tmp/dhcp.keytab DHCP/admin.example.org
or when using AD:
.. code-block:: console
kinit -k -t /tmp/dhcp.keytab DHCP/kea.<domain>
The credential cache can be displayed using ``klist``.
In production it is better to rely on a Kerberos Credential Manager as
the System Security Services Daemon (``sssd``).
The server principal will be "DNS/server.example.org@EXAMPLE.ORG¨ or
for AD "DNS/<server>.<domain>@<REALM>".
.. _stats-gss-tsig:
GSS-TSIG Statistics