mirror of
https://gitlab.com/libvirt/libvirt.git
synced 2024-11-06 13:20:20 +00:00
5aa78876e0
Most of the links were broken by moving the article into kbase, but in this case we need to also fix the anchor names. Signed-off-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com>
331 lines
11 KiB
ReStructuredText
331 lines
11 KiB
ReStructuredText
==========================
|
|
TLS x509 certificate setup
|
|
==========================
|
|
|
|
.. contents::
|
|
|
|
Public Key Infrastructure set up
|
|
--------------------------------
|
|
|
|
If you are unsure how to create TLS certificates, skip to the next section.
|
|
|
|
.. list-table::
|
|
:header-rows: 1
|
|
|
|
* - Location
|
|
- Machine
|
|
- Description
|
|
- Required fields
|
|
|
|
* - ``/etc/pki/CA/cacert.pem``
|
|
- Installed on the client and server
|
|
- CA's certificate
|
|
- n/a
|
|
|
|
* - ``$HOME/.pki/cacert.pem``
|
|
- Installed on the client
|
|
- CA's certificate
|
|
- n/a
|
|
|
|
* - ``/etc/pki/libvirt/private/serverkey.pem``
|
|
- Installed on the server
|
|
- Server's private key
|
|
- n/a
|
|
|
|
* - ``/etc/pki/libvirt/servercert.pem``
|
|
- Installed on the server
|
|
- Server's certificate signed by the CA
|
|
- CommonName (CN) must be the hostname of the server as it is seen by
|
|
clients. All hostname and IP address variants that might be used to
|
|
reach the server should be listed in Subject Alt Name fields.
|
|
|
|
* - ``/etc/pki/libvirt/private/clientkey.pem``
|
|
- Installed on the client
|
|
- Client's private key
|
|
- n/a
|
|
|
|
* - ``/etc/pki/libvirt/clientcert.pem``
|
|
- Installed on the client
|
|
- Client's certificate signed by the CA
|
|
- Distinguished Name (DN) can be checked against an access control list
|
|
(``tls_allowed_dn_list``).
|
|
|
|
* - ``$HOME/.pki/libvirt/clientkey.pem``
|
|
- Installed on the client
|
|
- Client's private key
|
|
- n/a
|
|
|
|
* - ``$HOME/.pki/libvirt/clientcert.pem``
|
|
- Installed on the client
|
|
- Client's certificate signed by the CA
|
|
(see `Issuing client certificates`_)
|
|
- Distinguished Name (DN) can be checked against an access control list
|
|
(``tls_allowed_dn_list``).
|
|
|
|
If 'pkipath' is specified in URI, then all the client certificates must be found
|
|
in the path specified, otherwise the connection will fail with a fatal error. If
|
|
'pkipath' is not specified:
|
|
|
|
- For a non-root user, libvirt tries to find the certificates in
|
|
$HOME/.pki/libvirt first. If the required CA certificate cannot be found,
|
|
then the global default location (/etc/pki/CA/cacert.pem) will be used.
|
|
Likewise, if either the client certificate or the client key cannot be found,
|
|
then the global default locations (/etc/pki/libvirt/clientcert.pem,
|
|
/etc/pki/libvirt/private/clientkey.pem) will be used.
|
|
|
|
- For the root user, the global default locations will always be used.
|
|
|
|
Background to TLS certificates
|
|
------------------------------
|
|
|
|
Libvirt supports TLS certificates for verifying the identity of the server and
|
|
clients. There are two distinct checks involved:
|
|
|
|
- The client should know that it is connecting to the right server. Checking
|
|
done by client by matching the certificate that the server sends to the
|
|
server's hostname. May be disabled by adding ``?no_verify=1`` to the `remote
|
|
URI <../uri.html#tls-transport>`__.
|
|
|
|
- The server should know that only permitted clients are connecting. This can
|
|
be done based on client's IP address, or on client's IP address and client's
|
|
certificate. Checking done by the server. May be enabled and disabled in the
|
|
`libvirtd.conf file <../remote.html#libvirtd-configuration-file>`__.
|
|
|
|
For full certificate checking you will need to have certificates issued by a
|
|
recognised `Certificate Authority
|
|
(CA) <https://en.wikipedia.org/wiki/Certificate_authority>`__ for your server(s)
|
|
and all clients. To avoid the expense of getting certificates from a commercial
|
|
CA, you can set up your own CA and tell your server(s) and clients to trust
|
|
certificates issues by your own CA. Follow the instructions in the next section.
|
|
|
|
Be aware that the `default configuration for
|
|
libvirtd <../remote.html#libvirtd-configuration-file>`__ allows any client to
|
|
connect provided they have a valid certificate issued by the CA for their own IP
|
|
address. You may want to change this to make it less (or more) permissive,
|
|
depending on your needs.
|
|
|
|
Setting up a Certificate Authority (CA)
|
|
---------------------------------------
|
|
|
|
You will need the `GnuTLS certtool program documented
|
|
here <https://www.gnutls.org/manual/html_node/certtool-Invocation.html>`__. In
|
|
Fedora, it is in the ``gnutls-utils`` package.
|
|
|
|
Create a private key for your CA:
|
|
|
|
::
|
|
|
|
certtool --generate-privkey > cakey.pem
|
|
|
|
and self-sign it by creating a file with the signature details called
|
|
``ca.info`` containing:
|
|
|
|
::
|
|
|
|
cn = Name of your organization
|
|
ca
|
|
cert_signing_key
|
|
|
|
::
|
|
|
|
certtool --generate-self-signed --load-privkey cakey.pem \
|
|
--template ca.info --outfile cacert.pem
|
|
|
|
(You can delete ``ca.info`` file now if you want).
|
|
|
|
Now you have two files which matter:
|
|
|
|
- ``cakey.pem`` - Your CA's private key (keep this very secret!)
|
|
|
|
- ``cacert.pem`` - Your CA's certificate (this is public).
|
|
|
|
``cacert.pem`` has to be installed on clients and server(s) to let them know
|
|
that they can trust certificates issued by your CA.
|
|
|
|
The normal installation directory for ``cacert.pem`` is
|
|
``/etc/pki/CA/cacert.pem`` on all clients and servers.
|
|
|
|
To see the contents of this file, do:
|
|
|
|
::
|
|
|
|
certtool -i --infile cacert.pem
|
|
|
|
X.509 certificate info:
|
|
|
|
Version: 3
|
|
Serial Number (hex): 00
|
|
Subject: CN=Libvirt Project
|
|
Issuer: CN=Libvirt Project
|
|
Signature Algorithm: RSA-SHA
|
|
Validity:
|
|
Not Before: Mon Jun 18 16:22:18 2007
|
|
Not After: Tue Jun 17 16:22:18 2008
|
|
[etc]
|
|
|
|
This is all that is required to set up your CA. Keep the CA's private key
|
|
carefully as you will need it when you come to issue certificates for your
|
|
clients and servers.
|
|
|
|
Issuing server certificates
|
|
---------------------------
|
|
|
|
For each server (libvirtd) you need to issue a certificate containing one or
|
|
more hostnames and/or IP addresses. Historically the CommonName (CN) field would
|
|
contain the hostname of the server and would match the hostname used in the URI
|
|
that clients pass to libvirt. In most TLS implementations the CN field is
|
|
considered legacy data. The preferential mechanism is to use Subject Alt Name
|
|
(SAN) extension fields to validate against. In the future use of the CN field
|
|
for validation may be discontinued entirely, so it is strongly recommended to
|
|
include the SAN fields.
|
|
|
|
In the example below, clients will be connecting to the server using a
|
|
`URI <../uri.html#remote-uris>`__ of ``qemu://compute1.libvirt.org/system``, so the
|
|
CN must be "``compute1.libvirt.org``".
|
|
|
|
Make a private key for the server:
|
|
|
|
::
|
|
|
|
certtool --generate-privkey > serverkey.pem
|
|
|
|
and sign that key with the CA's private key by first creating a template file
|
|
called ``server.info``. The template file will contain a number of fields to
|
|
define the server as follows:
|
|
|
|
::
|
|
|
|
organization = Name of your organization
|
|
cn = compute1.libvirt.org
|
|
dns_name = compute1
|
|
dns_name = compute1.libvirt.org
|
|
ip_address = 10.0.0.74
|
|
ip_address = 192.168.1.24
|
|
ip_address = 2001:cafe::74
|
|
ip_address = fe20::24
|
|
tls_www_server
|
|
encryption_key
|
|
signing_key
|
|
|
|
The 'cn' field should refer to the fully qualified public hostname of the
|
|
server. For the SAN extension data, there must also be one or more 'dns_name'
|
|
fields that contain all possible hostnames that can be reasonably used by
|
|
clients to reach the server, both with and without domain name qualifiers. If
|
|
clients are likely to connect to the server by IP address, then one or more
|
|
'ip_address' fields should also be added.
|
|
|
|
Use the template file as input to a ``certtool`` command to sign the server
|
|
certificate:
|
|
|
|
::
|
|
|
|
certtool --generate-certificate --load-privkey serverkey.pem \
|
|
--load-ca-certificate cacert.pem --load-ca-privkey cakey.pem \
|
|
--template server.info --outfile servercert.pem
|
|
|
|
This gives two files:
|
|
|
|
- ``serverkey.pem`` - The server's private key.
|
|
|
|
- ``servercert.pem`` - The server's public key.
|
|
|
|
We can examine this certificate and its signature:
|
|
|
|
::
|
|
|
|
certtool -i --infile servercert.pem
|
|
X.509 certificate info:
|
|
|
|
Version: 3
|
|
Serial Number (hex): 00
|
|
Subject: O=Libvirt Project,CN=compute1.libvirt.org
|
|
Issuer: CN=Libvirt Project
|
|
Signature Algorithm: RSA-SHA
|
|
Validity:
|
|
Not Before: Wed Oct 04 09:09:44 UTC 2017
|
|
Not After: Thu Oct 04 09:09:44 UTC 2018
|
|
Extensions:
|
|
Basic Constraints (critical):
|
|
Certificate Authority (CA): FALSE
|
|
Subject Alternative Name (not critical):
|
|
DNSname: compute1
|
|
DNSname: compute1.libvirt.org
|
|
IPAddress: 10.0.0.74
|
|
IPAddress: 192.168.1.24
|
|
IPAddress: 2001:cafe::74
|
|
IPAddress: fe20::24
|
|
|
|
Note the "Issuer" CN is "Libvirt Project" (the CA) and the "Subject" CN is
|
|
"compute1.libvirt.org" (the server). Notice that the hostname listed in the CN
|
|
must also be duplicated as a DNSname entry
|
|
|
|
Finally we have two files to install:
|
|
|
|
- ``serverkey.pem`` is the server's private key which should be copied to the
|
|
server *only* as ``/etc/pki/libvirt/private/serverkey.pem``.
|
|
|
|
- ``servercert.pem`` is the server's certificate which can be installed on the
|
|
server as ``/etc/pki/libvirt/servercert.pem``.
|
|
|
|
Issuing client certificates
|
|
---------------------------
|
|
|
|
For each client (ie. any program linked with libvirt, such as
|
|
`virt-manager <https://virt-manager.org/>`__) you need to issue a certificate
|
|
with the X.509 Distinguished Name (DN) set to a suitable name. You can decide
|
|
this on a company / organisation policy. For example:
|
|
|
|
::
|
|
|
|
C=GB,ST=London,L=London,O=Libvirt Project,CN=name_of_client
|
|
|
|
The process is the same as for `Issuing server certificates`_ so here we just
|
|
briefly cover the steps.
|
|
|
|
#. Make a private key:
|
|
|
|
::
|
|
|
|
certtool --generate-privkey > clientkey.pem
|
|
|
|
#. Act as CA and sign the certificate. Create client.info containing:
|
|
|
|
::
|
|
|
|
country = GB
|
|
state = London
|
|
locality = London
|
|
organization = Libvirt Project
|
|
cn = client1
|
|
tls_www_client
|
|
encryption_key
|
|
signing_key
|
|
|
|
and sign by doing:
|
|
|
|
::
|
|
|
|
certtool --generate-certificate --load-privkey clientkey.pem \
|
|
--load-ca-certificate cacert.pem --load-ca-privkey cakey.pem \
|
|
--template client.info --outfile clientcert.pem
|
|
|
|
#. Install the certificates on the client machine:
|
|
|
|
::
|
|
|
|
cp clientkey.pem /etc/pki/libvirt/private/clientkey.pem
|
|
cp clientcert.pem /etc/pki/libvirt/clientcert.pem
|
|
|
|
Troubleshooting TLS certificate problems
|
|
----------------------------------------
|
|
|
|
failed to verify client's certificate
|
|
On the server side, run the libvirtd server with the '--listen' and
|
|
'--verbose' options while the client is connecting. The verbose log messages
|
|
should tell you enough to diagnose the problem.
|
|
|
|
You can use the virt-pki-validate shell script to analyze the setup on the
|
|
client or server machines, preferably as root. It will try to point out the
|
|
possible problems and provide solutions to fix the set up up to a point where
|
|
you have secure remote access.
|