keystone/doc/source/advanced-topics/configure_tokenless_x509.rst

Configuring Keystone for Tokenless Authorization

Note

This feature is experimental and unsupported in Liberty.

Definitions

• `X.509 Tokenless Authorization`: Provides a means to authorize client operations within Keystone by using an X.509 SSL client certificate without having to issue a token. For details, please refer to the specs Tokenless Authorization with X.509 Client SSL Certificate

Prerequisites

Keystone must be running in a web container with https enabled; tests have been done with Apache/2.4.7 running on Ubuntu 14.04 . Please refer to Install and Configure Keystone <../install/index> and apache-certificate-and-key-installation as references for this setup.

Apache Configuration

To enable X.509 tokenless authorization, SSL has to be enabled and configured in the Apache virtual host file. The Client authentication attribute SSLVerifyClient should be set as optional to allow other token authentication methods and attribute SSLOptions needs to set as +StdEnvVars to allow certificate attributes to be passed. The following is the sample virtual host file used for the testing.

<VirtualHost *:443>
    WSGIScriptAlias / /var/www/cgi-bin/keystone/main
    ErrorLog /var/log/apache2/keystone.log
    LogLevel debug
    CustomLog /var/log/apache2/access.log combined
    SSLEngine on
    SSLCertificateFile    /etc/apache2/ssl/apache.cer
    SSLCertificateKeyFile /etc/apache2/ssl/apache.key
    SSLCACertificatePath /etc/apache2/capath
    SSLOptions +StdEnvVars
    SSLVerifyClient optional
</VirtualHost>

Keystone Configuration

The following options can be defined in `keystone.conf`:

• trusted_issuer - The multi-str list of trusted issuers to further filter the certificates that are allowed to participate in the X.509 tokenless authorization. If the option is absent then no certificates will be allowed. The naming format for the attributes of a Distinguished Name(DN) must be separated by a comma and contain no spaces; however spaces are allowed for the value of an attribute, like 'L=San Jose' in the example below. This configuration option may be repeated for multiple values. Please look at the sample below.
• protocol - The protocol name for the X.509 tokenless authorization along with the option issuer_attribute below can look up its corresponding mapping. It defaults to x509.
• issuer_attribute - The issuer attribute that is served as an IdP ID for the X.509 tokenless authorization along with the protocol to look up its corresponding mapping. It is the environment variable in the WSGI environment that references to the Issuer of the client certificate. It defaults to SSL_CLIENT_I_DN.

This is a sample configuration for two trusted_issuer and a protocol set to x509.

[tokenless_auth]
trusted_issuer = emailAddress=mary@abc.com,CN=mary,OU=eng,O=abc,L=San Jose,ST=California,C=US
trusted_issuer = emailAddress=john@openstack.com,CN=john,OU=keystone,O=openstack,L=Sunnyvale,ST=California,C=US
protocol = x509

Setup Mapping

Like federation, X.509 tokenless authorization also utilizes the mapping mechanism to formulate an identity. The identity provider must correspond to the issuer of the X.509 SSL client certificate. The protocol for the given identity is x509 by default, but can be configurable.

Create an Identity Provider (IdP)

In order to create an IdP, the issuer DN in the client certificate needs to be provided. The following sample is what a generic issuer DN looks like in a certificate.

E=john@openstack.com
CN=john
OU=keystone
O=openstack
L=Sunnyvale
S=California
C=US

The issuer DN should be constructed as a string that contains no spaces and have the right order separated by commas like the example below. Please be aware that emailAddress and ST should be used instead of E and S that are shown in the above example. The following is the sample Python code used to create the IdP ID.

import hashlib
issuer_dn = 'emailAddress=john@openstack.com,CN=john,OU=keystone,
    O=openstack,L=Sunnyvale,ST=California,C=US'
hashed_idp = hashlib.sha256(issuer_dn)
idp_id = hashed_idp.hexdigest()
print(idp_id)

The output of the above Python code will be the IdP ID and the following sample curl command should be sent to keystone to create an IdP with the newly generated IdP ID.

curl -k -s -X PUT -H "X-Auth-Token: <TOKEN>" \
     -H "Content-Type: application/json" \
     -d '{"identity_provider": {"description": "Stores keystone IDP identities.","enabled": true}}' \
     https://<HOSTNAME>:<PORT>/v3/OS-FEDERATION/identity_providers/<IdP ID>

Create a Map

A mapping needs to be created to map the Subject DN in the client certificate as a user to yield a valid local user if the user's type defined as local in the mapping. For example, the client certificate has Subject DN as CN=alex,OU=eng,O=nice-network,L=Sunnyvale, ST=California,C=US, in the following examples, user_name will be mapped toalex and domain_name will be mapped to nice-network. And it has user's type set to local. If user's type is not defined, it defaults to ephemeral.

Please refer to mod_ssl for the detailed mapping attributes.

{
     "mapping": {
         "rules": [
             {
                 "local": [
                     {
                        "user": {
                            "name": "{0}",
                            "domain": {
                                "name": "{1}"
                            },
                            "type": "local"
                        }
                     }
                ],
                "remote": [
                    {
                        "type": "SSL_CLIENT_S_DN_CN"
                    },
                    {
                        "type": "SSL_CLIENT_S_DN_O"
                    }
                ]
            }
        ]
    }
}

When user's type is not defined or set to ephemeral, the mapped user does not have to be a valid local user but the mapping must yield at least one valid local group. For example:

{
     "mapping": {
         "rules": [
             {
                 "local": [
                     {
                        "user": {
                            "name": "{0}",
                            "type": "ephemeral"
                        }
                     },
                     {
                        "group": {
                            "id": "12345678"
                        }
                     }
                ],
                "remote": [
                    {
                        "type": "SSL_CLIENT_S_DN_CN"
                    }
                ]
            }
        ]
    }
}

The following sample curl command should be sent to keystone to create a mapping with the provided mapping ID. The mapping ID is user designed and it can be any string as opposed to IdP ID.

curl -k -s -H "X-Auth-Token: <TOKEN>" \
     -H "Content-Type: application/json" \
     -d '{"mapping": {"rules": [{"local": [{"user": {"name": "{0}","type": "ephemeral"}},{"group": {"id": "<GROUPID>"}}],"remote": [{"type": "SSL_CLIENT_S_DN_CN"}]}]}}' \
     -X PUT https://<HOSTNAME>:<PORT>/v3/OS-FEDERATION/mappings/<MAPPING ID>

Create a Protocol

The name of the protocol will be the one defined in keystone.conf as protocol which defaults to x509. The protocol name is user designed and it can be any name as opposed to IdP ID.

A protocol name and an IdP ID will uniquely identify a mapping.

The following sample curl command should be sent to keystone to create a protocol with the provided protocol name that is defined in keystone.conf.

curl -k -s -H "X-Auth-Token: <TOKEN>" \
     -H "Content-Type: application/json" \
     -d '{"protocol": {"mapping_id": "<MAPPING ID>"}}' \
     -X PUT https://<HOSTNAME>:<PORT>/v3/OS-FEDERATION/identity_providers/<IdP ID>/protocols/<PROTOCOL NAME>

Setup auth_token middleware

In order to use auth_token middleware as the service client for X.509 tokenless authorization, both configurable options and scope information will need to be setup.

Configurable Options

The following configurable options in auth_token middleware should set to the correct values:

• auth_protocol - Set to https.
• certfile - Set to the full path of the certificate file.
• keyfile - Set to the full path of the private key file.
• cafile - Set to the full path of the trusted CA certificate file.

Scope Information

The scope information will be passed from the headers with the following header attributes to:

• X-Project-Id - If specified, its the project scope.
• X-Project-Name - If specified, its the project scope.
• X-Project-Domain-Id - If specified, its the domain of project scope.
• X-Project-Domain-Name - If specified, its the domain of project scope.
• X-Domain-Id - If specified, its the domain scope.
• X-Domain-Name - If specified, its the domain scope.

Test It Out with cURL

Once the above configurations have been setup, the following curl command can be used for token validation.

curl -v -k -s -X GET --cert /<PATH>/x509client.crt \
     --key /<PATH>/x509client.key \
     --cacert /<PATH>/ca.crt \
     -H "X-Project-Name: <PROJECT-NAME>" \
     -H "X-Project-Domain-Id: <PROJECT-DOMAIN-ID>" \
     -H "X-Subject-Token: <TOKEN>" \
     https://<HOST>:<PORT>/v3/auth/tokens | python -mjson.tool

Details of the Options

• --cert - The client certificate that will be presented to Keystone. The Issuer in the certificate along with the defined protocol in keystone.conf will uniquely identify the mapping. The Subject in the certificate will be mapped to the valid local user from the identified mapping.
• --key - The corresponding client private key.
• --cacert - It can be the Apache server certificate or its issuer (signer) certificate.
• X-Project-Name - The project scope needs to be passed in the header.
• X-Project-Domain-Id - Its the domain of project scope.
• X-Subject-Token - The token to be validated.