Cloud Servers Authentication

OpenNebula ships with two servers: Sunstone and EC2. When a user interacts with one of them, the server authenticates the request and then forwards the requested operation to the OpenNebula daemon.

The forwarded requests between the servers and the core daemon include the original user name, and are signed with the credentials of an special server user.

In this guide this request forwarding mechanism is explained, and how it is secured with a symmetric-key algorithm or x509 certificates.

Server Users

The Sunstone and EC2 services communicate with the core using a server user. OpenNebula creates the serveradmin account at bootstrap, with the authentication driver server_cipher (symmetric key).

This server user uses a special authentication mechanism that allows the servers to perform an operation on behalf of other user.

You can strengthen the security of the requests from the servers to the core daemon changing the serveruser’s driver to server_x509. This is specially relevant if you are running your server in a machine other than the frontend.

Please note that you can have as many users with a server_* driver as you need. For example, you may want to have Sunstone configured with a user with server_x509 driver, and EC2 with server_cipher.

Symmetric Key


This mechanism is enabled by default, you will have a user named serveradmin with driver server_cipher.

To use it, you need a user with the driver server_cipher. Enable it in the relevant configuration file in /etc/one:

  • Sunstone: /etc/one/sunstone-server.conf
  • EC2: /etc/one/econe.conf
:core_auth: cipher


You must update the configuration files in /var/lib/one/.one if you change the serveradmin’s password, or create a different user with the server_cipher driver.

ls -1 /var/lib/one/.one
cat /var/lib/one/.one/sunstone_auth


serveradmin password is hashed in the database. You can use the --sha1 flag when issuing oneuser passwd command for this user.


When Sunstone is running in a different machine than oned you should use an SSL connection. This can be archived with an SSL proxy like stunnel or apache/nginx acting as proxy. After securing OpenNebula XMLRPC connection configure Sunstone to use https with the proxy port:

:one_xmlrpc: https://frontend:2634/RPC2

x509 Encryption


To enable it, change the authentication driver of the serveradmin user, or create a new user with the driver server_x509:

oneuser chauth serveradmin server_x509
oneuser passwd serveradmin --x509 --cert usercert.pem

The serveradmin account should look like:

oneuser list

  ID GROUP    NAME            AUTH                                               PASSWORD
   0 oneadmin oneadmin        core               c24783ba96a35464632a624d9f829136edc0175e
   1 oneadmin serveradmin     server_x                       /C=ES/O=ONE/OU=DEV/CN=server

You need to edit /etc/one/auth/server_x509_auth.conf and uncomment all the fields. The defaults should work:

# User to be used for x509 server authentication
:srv_user: serveradmin

# Path to the certificate used by the OpenNebula Services
# Certificates must be in PEM format
:one_cert: "/etc/one/auth/cert.pem"
:one_key: "/etc/one/auth/pk.pem"

Copy the certificate and the private key to the paths set in :one_cert: and :one_key:, or simply update the paths.

Then edit the relevant configuration file in /etc/one:

  • Sunstone: /etc/one/sunstone-server.conf
  • EC2: /etc/one/econe.conf
:core_auth: x509


To trust the serveradmin certificate, /etc/one/auth/cert.pem if you used the default path, the CA’s certificate must be added to the ca_dir defined in /etc/one/auth/x509_auth.conf. See the x509 Authentication guide for more information.

openssl x509 -noout -hash -in cacert.pem
sudo cp cacert.pem /etc/one/auth/certificates/78d0bbd8.0

Tuning & Extending


You can find the drivers in these paths:

  • /var/lib/one/remotes/auth/server_cipher/authenticate
  • /var/lib/one/remotes/auth/server_server/authenticate

Authentication Session String

OpenNebula users with the driver server_cipher or server_x509 use a special authentication session string (the first parameter of the XML-RPC calls). A regular authentication token is in the form:


Whereas a user with a server_* driver must use this token format:


The core daemon understands a request with this authentication session token as “perform this operation on behalf of target_user”. The secret part of the token is signed with one of the two mechanisms explained before.