Configuring a request header identity provider - Configuring identity providers | Authentication and authorization

Identity providers in OKD
About request header authentication
- Security Support Provider Interface connection support on Microsoft Windows
Creating a ConfigMap
Sample request header custom resource
Adding an identity provider to your cluster
Example Apache authentication configuration using request header
Custom proxy configuration
Configuring Apache authentication using the request header
Additional resources

Configure the request-header identity provider to identify users from request header values, such as X-Remote-User. Use this provider when an authenticating proxy validates users and sets those headers for OKD.

Identity providers in OKD

You can configure identity providers by creating a custom resource (CR) that describes the provider and adding it to the cluster. Identity providers enable user authentication in OKD beyond the default kubeadmin user.

OKD usernames containing /, :, and % are not supported.

About request header authentication

Request header authentication identifies users from header values such as X-Remote-User. An authenticating proxy with mutual TLS (mTLS) validates users and sets the identity header for OKD.

The request header identity provider is typically used in combination with an authenticating proxy, which sets the request header value. This identity provider cannot be combined with other identity providers that use direct password logins, such as htpasswd, Keystone, LDAP or basic authentication.

You can also use the request header identity provider for advanced configurations such as the community-supported SAML application. This solution is not supported by Red Hat.

For users to authenticate using this identity provider, they must access https://<namespace_route>/oauth/authorize and subpaths of that endpoint through an authenticating proxy. To accomplish this, configure the OAuth server to redirect unauthenticated requests for OAuth tokens to the proxy endpoint that proxies to https://<namespace_route>/oauth/authorize.

To redirect unauthenticated requests from clients expecting browser-based login flows:

Set the provider.loginURL parameter to the authenticating proxy URL that authenticates interactive clients and then proxies the request to https://<namespace_route>/oauth/authorize.

To redirect unauthenticated requests from clients expecting WWW-Authenticate challenges:

Set the provider.challengeURL parameter to the authenticating proxy URL that authenticates clients expecting WWW-Authenticate challenges and then proxy the request to https://<namespace_route>/oauth/authorize.

The provider.challengeURL and provider.loginURL parameters can include the following tokens in the query portion of the URL:

${url} is replaced with the current URL, escaped to be safe in a query parameter.

For example: https://www.example.com/sso-login?then=${url}
${query} is replaced with the current query string, unescaped.

For example: https://www.example.com/auth-proxy/oauth/authorize?${query}

As of OKD 4.1, your proxy must support mTLS.

Security Support Provider Interface connection support on Microsoft Windows

The Security Support Provider Interface (SSPI) enables the OpenShift CLI (oc) to support SSO flows on Microsoft Windows. If you use the request header identity provider with a GSSAPI-enabled proxy to connect an Active Directory server to OKD, users can automatically authenticate to OKD by using the oc command line interface from a domain-joined Microsoft Windows computer.

Creating a ConfigMap

Create a ConfigMap object in the openshift-config namespace that contains the certificate authority bundle for the identity provider. OKD uses this bundle to validate Transport Layer Security (TLS) connections to the identity provider.

Procedure

Define an OKD ConfigMap object containing the CA by running the following command:

$ oc create configmap ca-config-map --from-file=ca.crt=/path/to/ca -n openshift-config

Optional: Apply the following YAML to create the config map:

apiVersion: v1
kind: ConfigMap
metadata:
  name: ca-config-map
  namespace: openshift-config
data:
  ca.crt: |
    <CA_certificate_PEM>

The CA must be stored in the ca.crt key of the ConfigMap object.

Sample request header custom resource

Review the sample request header OAuth custom resource (CR) to understand provider parameters and acceptable values before you configure the identity provider in your cluster.

apiVersion: config.openshift.io/v1
kind: OAuth
metadata:
  name: cluster
spec:
  identityProviders:
  - name: requestheaderidp
    mappingMethod: claim
    type: RequestHeader
    requestHeader:
      challengeURL: "https://www.example.com/challenging-proxy/oauth/authorize?${query}"
      loginURL: "https://www.example.com/login-proxy/oauth/authorize?${query}"
      ca:
        name: ca-config-map
      clientCommonNames:
      - my-auth-proxy
      headers:
      - X-Remote-User
      - SSO-User
      emailHeaders:
      - X-Remote-User-Email
      nameHeaders:
      - X-Remote-User-Display-Name
      preferredUsernameHeaders:
      - X-Remote-User-Login

where:

spec.identityProviders.name

Specifies that the provider name is prefixed to the username in the request header to form an identity name.

spec.identityProviders.mappingMethod

Specifies how mappings are established between the identities of this provider and User objects.

spec.identityProviders.requestHeader.challengeURL

Specifies the URL for redirecting unauthenticated /oauth/authorize requests to an authenticating proxy that authenticates browser-based clients and then proxies the request to https://<namespace_route>/oauth/authorize. The URL that proxies to https://<namespace_route>/oauth/authorize must end with /authorize with no trailing slash and must also proxy subpaths for OAuth approval flows to work properly. ${url} is replaced with the current URL, escaped to be safe in a query parameter. ${query} is replaced with the current query string. If this attribute is not defined, loginURL must be used. This value is optional.

spec.identityProviders.requestHeader.loginURL

Specifies the URL for redirecting unauthenticated /oauth/authorize requests to an authenticating proxy that authenticates clients expecting WWW-Authenticate challenges and then proxies them to https://<namespace_route>/oauth/authorize. ${url} is replaced with the current URL, escaped to be safe in a query parameter. ${query} is replaced with the current query string. If this attribute is not defined, challengeURL must be used. This value is optional.

spec.identityProviders.requestHeader.ca

Specifies a reference to an OKD ConfigMap object containing a Privacy-Enhanced Mail (PEM)-encoded certificate bundle used as a trust anchor to validate the Transport Layer Security (TLS) certificates presented by the remote server.

As of OKD 4.1, the ca field is required for this identity provider. This means that your proxy must support mutual TLS.

spec.identityProviders.requestHeader.clientCommonNames

Specifies a list of common names (cn). If set, a valid client certificate with a Common Name (cn) in the specified list must be presented before the request headers are checked for usernames. If empty, any Common Name is allowed. Can only be used in combination with ca. This value is optional.

spec.identityProviders.requestHeader.headers

Specifies header names to check, in order, for the user identity. The first header containing a value is used as the identity. This field is required, and header matching is case-insensitive.

spec.identityProviders.requestHeader.emailHeaders

Specifies header names to check, in order, for an email address. The first header containing a value is used as the email address. Header matching is case-insensitive. This value is optional.

spec.identityProviders.requestHeader.nameHeaders

Specifies header names to check, in order, for a display name. The first header containing a value is used as the display name. Header matching is case-insensitive. This value is optional.

spec.identityProviders.requestHeader.preferredUsernameHeaders

Specifies header names to check, in order, for a preferred username, if different from the immutable identity determined from the headers specified in headers. The first header containing a value is used as the preferred username when provisioning. Header matching is case-insensitive. This value is optional.

Additional resources

Identity provider parameters

Adding an identity provider to your cluster

Apply the identity provider custom resource (CR) to your cluster after you define it. With this configuration, you can authenticate with the configured identity provider.

Prerequisites

You have access to a OKD cluster.
You have created the CR for your identity providers.
You are logged in as an administrator.

Procedure

Apply the defined CR by running the following command:

$ oc apply -f </path/to/CR>

If a CR does not exist, oc apply creates a new CR and might trigger the following warning: Warning: oc apply should be used on resources created by either oc create --save-config or oc apply. In this case you can safely ignore this warning.

Log in to the cluster as a user from your identity provider, entering the password when prompted.
```
$ oc login -u <username>
```
Confirm that the user logged in successfully and that the username displays by running the following command:
```
$ oc whoami
```

Example Apache authentication configuration using request header

Review this example to configure an Apache authentication proxy with the request header identity provider. Use this example to set up a proxy and connect it to OKD.

The example configures an Apache authentication proxy for OKD by using the request header identity provider.

Custom proxy configuration

Review the requirements for a custom authentication proxy used with the request header identity provider. Meeting these requirements prevents header spoofing and ensures OAuth authorization flows work correctly.

Using the mod_auth_gssapi module is a popular way, but not required, to configure the Apache authentication proxy by using the request header identity provider. Other proxies can easily be used if the following requirements are met:

Blocks the X-Remote-User header from client requests to prevent spoofing.
Enforces client certificate authentication in the RequestHeaderIdentityProvider configuration.
Requires the X-Csrf-Token header be set for all authentication requests by using the challenge flow.
Ensures only the /oauth/authorize endpoint and subpaths of that endpoint are proxied. Redirects must be rewritten to allow the backend server to send the client to the correct location.
Requires the proxy URL for https://<namespace_route>/oauth/authorize to end with /authorize with no trailing slash.
Ensures subpaths of the proxy authorize URL forward to matching subpaths under https://<namespace_route>/oauth/authorize.

The https://<namespace_route> address is the route to the OAuth server and can be obtained by running oc get route -n openshift-authentication.

Configuring Apache authentication using the request header

Configure an Apache authentication proxy with the mod_auth_gssapi module for the request header identity provider. Use this example to set up a proxy that validates users and forwards trusted identity headers to OKD.

This proxy uses a client certificate to connect to the OAuth server, which is configured to trust the X-Remote-User header.

Prerequisites

Obtain the mod_auth_gssapi module from the optional channel. For more information, see "Optional channel".
The following packages are installed on your local machine:
- httpd
- mod_ssl
- mod_session
- apr-util-openssl
- mod_auth_gssapi

Procedure

Generate a CA for validating requests that submit the trusted header.

Create an OKD ConfigMap object containing the CA by running the following command:

$ oc create configmap ca-config-map --from-file=ca.crt=/path/to/ca -n openshift-config

Optional: Apply the following YAML to create the config map. For example:

apiVersion: v1
kind: ConfigMap
metadata:
  name: ca-config-map
  namespace: openshift-config
data:
  ca.crt: |
    <CA_certificate_PEM>

The certificate authority must be stored in the ca.crt key of the ConfigMap object.

Generate a client certificate for the proxy.

You can generate this certificate by using any x509 certificate tooling. The client certificate must be signed by the CA you generated for validating requests that submit the trusted header.
Create the custom resource (CR) for your identity providers.
Create the certificate for the Apache configuration.

The certificate that you specify as the SSLProxyMachineCertificateFile parameter value is the client certificate for the proxy that authenticates the proxy to the server. It must use TLS Web Client Authentication as the extended key type.

Create the Apache configuration. Use the following template to provide your required settings and values:

Carefully review the template and customize the template contents to fit your environment.

LoadModule request_module modules/mod_request.so
LoadModule auth_gssapi_module modules/mod_auth_gssapi.so
# Some Apache configurations might require these modules.
# LoadModule auth_form_module modules/mod_auth_form.so
# LoadModule session_module modules/mod_session.so

# Nothing needs to be served over HTTP.  This virtual host simply redirects to
# HTTPS.
<VirtualHost *:80>
  DocumentRoot /var/www/html
  RewriteEngine              On
  RewriteRule     ^(.*)$     https://%{HTTP_HOST}$1 [R,L]
</VirtualHost>

<VirtualHost *:443>
  # This needs to match the certificates you generated.  See the CN and X509v3
  # Subject Alternative Name in the output of:
  # openssl x509 -text -in /etc/pki/tls/certs/localhost.crt
  ServerName www.example.com

  DocumentRoot /var/www/html
  SSLEngine on
  SSLCertificateFile /etc/pki/tls/certs/localhost.crt
  SSLCertificateKeyFile /etc/pki/tls/private/localhost.key
  SSLCACertificateFile /etc/pki/CA/certs/ca.crt

  SSLProxyEngine on
  SSLProxyCACertificateFile /etc/pki/CA/certs/ca.crt
  # It is critical to enforce client certificates. Otherwise, requests can
  # spoof the X-Remote-User header by accessing the /oauth/authorize endpoint
  # directly.
  SSLProxyMachineCertificateFile /etc/pki/tls/certs/authproxy.pem

  # To use the challenging-proxy, an X-Csrf-Token must be present.
  RewriteCond %{REQUEST_URI} ^/challenging-proxy
  RewriteCond %{HTTP:X-Csrf-Token} ^$ [NC]
  RewriteRule ^.* - [F,L]

  <Location /challenging-proxy/oauth/authorize>
      # Insert your backend server name/ip here.
      ProxyPass https://<namespace_route>/oauth/authorize
      AuthName "SSO Login"
      # For Kerberos
      AuthType GSSAPI
      Require valid-user
      RequestHeader set X-Remote-User %{REMOTE_USER}s

      GssapiCredStore keytab:/etc/httpd/protected/auth-proxy.keytab
      # Enable the following if you want to allow users to fallback
      # to password based authentication when they do not have a client
      # configured to perform kerberos authentication.
      GssapiBasicAuth On

      # For ldap:
      # AuthBasicProvider ldap
      # AuthLDAPURL "ldap://ldap.example.com:389/ou=People,dc=my-domain,dc=com?uid?sub?(objectClass=*)"
    </Location>

    <Location /login-proxy/oauth/authorize>
    # Insert your backend server name/ip here.
    ProxyPass https://<namespace_route>/oauth/authorize

      AuthName "SSO Login"
      AuthType GSSAPI
      Require valid-user
      RequestHeader set X-Remote-User %{REMOTE_USER}s env=REMOTE_USER

      GssapiCredStore keytab:/etc/httpd/protected/auth-proxy.keytab
      # Enable the following if you want to allow users to fallback
      # to password based authentication when they do not have a client
      # configured to perform kerberos authentication.
      GssapiBasicAuth On

      ErrorDocument 401 /login.html
    </Location>

</VirtualHost>

RequestHeader unset X-Remote-User

The https://<namespace_route> address is the route to the OAuth server and can be obtained by running oc get route -n openshift-authentication.

Update the identityProviders section of the custom resource (CR):

identityProviders:
  - name: requestheaderidp
    type: RequestHeader
    requestHeader:
      challengeURL: "https://<namespace_route>/challenging-proxy/oauth/authorize?${query}"
      loginURL: "https://<namespace_route>/login-proxy/oauth/authorize?${query}"
      ca:
        name: ca-config-map
      clientCommonNames:
      - my-auth-proxy
      headers:
      - X-Remote-User

Verification

Confirm that you can bypass the proxy when you supply the correct client certificate and header by running the following command:

$ curl -L -k -H "X-Remote-User: joe" \
   --cert /etc/pki/tls/certs/authproxy.pem \
   https://<namespace_route>/oauth/token/request

Confirm that requests that do not supply the client certificate fail by running the following command:
```
$ curl -L -k -H "X-Remote-User: joe" \
   https://<namespace_route>/oauth/token/request
```

Confirm that the challengeURL redirect is active by running the following command:

$ curl -k -v -H 'X-Csrf-Token: 1' \
   https://<namespace_route>/oauth/authorize?client_id=openshift-challenging-client&response_type=token

Copy the challengeURL redirect to use in the next step.

Show a 401 response with a WWW-Authenticate basic challenge, a negotiate challenge, or both challenges by running the following command:
```
$ curl -k -v -H 'X-Csrf-Token: 1' \
   <challengeURL_redirect + query>
```
If you generated a Kerberos ticket by using kinit, destroy it by running the following command:
```
$ kdestroy -c <cache_name>
```
Replace <cache_name> with the name of your Kerberos cache.
Log in to the OpenShift CLI (oc) with your Kerberos credentials by running the following command:
```
$ oc login -u <username>
```
Enter your Kerberos username and password at the prompt.
Log out of the oc tool by running the following command:
```
$ oc logout
```
Use your Kerberos credentials to get a ticket by running the following command:
```
$ kinit
```
Enter your Kerberos username and password at the prompt.
Confirm that you can log in to the oc tool by running the following command:
```
$ oc login
```
If your configuration is correct, you are logged in without entering separate credentials.

Additional resources

Optional channel