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MITRE Caldera Plugin: SAML

Overview

saml is a Caldera plugin that provides SAML authentication for Caldera by establishing Caldera as a SAML Service Provider (SP). To use this plugin, users will need to have Caldera configured as an application in their Identity Provider (IdP), and a conf/settings.json file will need to be created in the plugin with the appropriate SAML settings and IdP and SP information.

When enabled and configured, this plugin will provide the following:

• When browsing to the main Caldera site (e.g. http://localhost:8888/) or to the /enter URL for the Caldera site (e.g. http://localhost:8888/enter), unauthenticated users will be redirected to their IdP login page rather than to the default Caldera login page. If the SAML settings are not properly configured or if there is an issue with attempting the redirect, the user will be redirected to the default Caldera login page as a failsafe.
• When users access the Caldera application directly from their IdP, they will immediately authenticate into Caldera without having to provide login credentials, provided that Caldera was configured correctly within the IdP settings. If the SAML login fails for whatever reason (e.g. the application was provisioned using a username that does not exist within Caldera), the user will be taken to the default Caldera login page.

Setup

There are two main setup components required for SAML authentication within this plugin:

1. The IdP administrators need to configure Caldera as an application within the IdP platform
2. Caldera administrators need to configure the conf/settings.json settings file within the saml plugin.

Installing Dependencies

To install dependencies, run the following from within the plugin directory::

pip3 install -r requirements.txt

Note that requirements.txt requires xmlsec, which in turn requires certain native libraries. See the xmlsec page for more details and to see which native libraries are required for the operating system that is hosting Caldera in your particular environment.

Configuring Caldera Within the IdP Platform

To provision Caldera access for users within the Identity Provider, follow the instructions for your particular Identity Provider to create the Caldera application with the appropriate SAML settings.

• When asked for the "Single Sign On URL", "Recipient URL", and "Destination URL", set this to the /saml URL for your Caldera server (e.g. http://localhost:8888/saml). When the plugin is enabled, the server will listen on this endpoint for SAML requests.
• When asked for the "Audience URI" or "SP Entity ID", use the HTTP endpoint for your Caldera server without the trailing slash (e.g. http://localhost:8888).
• You may keep the "Default RelayState" blank
• If asked for a Name ID format, you may keep it as unspecified
• Include a username attribute statement with a value that contains the user's username or login name for the Identity Provider (e.g. email address). This is required by Caldera to track which users are logging into the system under which Caldera accounts.

Once the application is created with the appropriate SAML settings, follow your IdP instructions to provision access to the necessary users. You will also need to follow your IdP's instructions to find the SSO URL for the IdP, the IdP Issuer URL, and the X.509 Certificate for the IdP. This information is needed to configure the SAML settings within this plugin.

Application Usernames

To avoid having to create individual Caldera accounts for each user in the IdP, one method is to create a fixed set of Caldera user accounts (e.g. red and blue users) and assign the Caldera username as the application username for the user assignment. This way, multiple users can log in using the same Caldera username, and the SAML request will also include their username attribute statement, so that Caldera's authentication service can distinguish between different users from the IdP platform.

Configuring SAML settings within Caldera

Once Caldera is configured as an application within your IdP, you can start creating the conf/settings.json file within the plugin according to the python3-saml instructions . The following settings are required unless marked otherwise:

• Set strict to true
• Under sp:
  • For entityId, use the HTTP endpoint for the C2 Server (e.g. "http://localhost:8888")
  • Under assertionConsumerService:
    • The url must be the /saml endpoint for the C2 server (e.g. "http://localhost:8888/saml")
    • For binding, use "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
  • Do not include an entry for singleLogoutService
• Under idp:
  • For entityId, use the Identity Provider's identifier URI. You will need to obtain this from your Caldera application configuration for the Identity Provider.
  • Under singleSignOnService:
    • For url, use the IdP's SSO URL as provided by the IdP for the Caldera application configuration.
    • For binding, use "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
  • For the x509cert, use the base64-encoded string for the IdP's X.509 certificate.
• Under security:
  • Set wantAttributeStatement to true
  • Set the remaining security settings as needed for your environment.
  • Note that the security settings as shown in the python3-saml readme are placed in a separate file called advanced_settings.json. For simplicity, the saml plugin requires you to combine all settings into the same conf/settings.json file, as shown in the example below.

You may adjust settings as needed for your environment.

Below is a sample template for the SAML settings JSON file, which is also located in config/sample.json in the plugin. Refer to the python3-saml page for full documentation and examples.

{
    "strict": true,
    "debug": true,
    "sp": {
        "entityId": "http://localhost:8888",
        "assertionConsumerService": {
            "url": "http://localhost:8888/saml",
            "binding": "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
        }
    },
    "idp": {
        "entityId": "http://myidentityprovider.com/connector_id_url",
        "singleSignOnService": {
            "url": "https://myidentityprovider.com/sso_url",
            "binding": "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
        },
        "x509cert": "base64-encoded certificate data"
    },
    "security": {
        "wantMessagesSigned": true,
        "wantAssertionsSigned": true,
        "wantAttributeStatement": true
    }
}

Setting the SAML Login Handler

Once Caldera's SAML settings are configured and Caldera is set up on the IdP platform, the final step requires setting the SAML login handler as the main login handler in the Caldera config YAML file. Within the config file, set auth.login.handler.module to plugins.saml.app.saml_login_handler as shown below:

auth.login.handler.module: plugins.saml.app.saml_login_handler

Restart the Caldera server, and any future authentication requests will now be handled via SAML according to the previously established settings.