saml-auth

Description

The saml-auth Plugin enables SAML 2.0 (Security Assertion Markup Language) authentication for API routes. It acts as a SAML Service Provider (SP) and integrates with external Identity Providers (IdP) such as Keycloak, Okta, and Azure Active Directory to authenticate users before allowing access to upstream resources.

When a request arrives at a protected route, the Plugin checks for a valid SAML session. If no session exists, it redirects the user to the IdP for authentication. After the user authenticates at the IdP, the IdP posts a signed SAML assertion back to the SP's Assertion Consumer Service (ACS) URL. The Plugin validates the assertion and establishes a session for the user.

The Plugin supports:

• HTTP-Redirect binding (default) — SAML messages are transmitted as URL query parameters.
• HTTP-POST binding — SAML messages are transmitted as HTML form values.
• Single Logout (SLO) — logout requests can be initiated by the SP or the IdP.
• Session key rotation via secret_fallbacks.

Authenticated user data is stored in ctx.external_user and can be used by downstream authorization plugins such as acl.

Attributes

Name	Type	Required	Encrypted	Default	Valid Values	Description
sp_issuer	string	True				Service Provider (SP) entity ID/issuer URI. Must match the SP entity ID registered with the IdP.
idp_uri	string	True				Identity Provider SSO endpoint URL. This is the URL to which SAML authentication requests are sent.
idp_cert	string	True				IdP's X.509 certificate in PEM format, used to verify signatures on SAML assertions.
login_callback_uri	string	True				SP's Assertion Consumer Service (ACS) URL. The IdP posts SAML responses to this URL after authentication. Must be registered with the IdP.
logout_uri	string	True				SP's Single Logout (SLO) endpoint. Requests to this URI initiate the logout flow.
logout_callback_uri	string	True				SP's SLO callback URL. The IdP sends logout responses to this URL. Must be registered with the IdP.
logout_redirect_uri	string	True				URL to redirect users to after a successful logout.
sp_cert	string	True				SP's X.509 certificate in PEM format. Used by the IdP to verify requests signed by the SP.
sp_private_key	string	True	Yes			SP's private key in PEM format, used to sign SAML requests. This field is encrypted at rest.
auth_protocol_binding_method	string	False		HTTP-Redirect	HTTP-Redirect, HTTP-POST	SAML binding method for the authentication request. When set to HTTP-POST, the session cookie SameSite attribute is set to None and Secure is set to true.
secret	string	True	Yes		8–32 characters	Secret used for session key derivation. Must be identical on all APISIX nodes to ensure sessions are readable across workers and after reloads. This field is encrypted at rest.
secret_fallbacks	array[string]	False	Yes		Each item: 8–32 characters	List of previous secrets used during key rotation. Allows sessions encrypted with old secrets to remain valid. This field is encrypted at rest.

Prerequisites

Install lua-resty-saml on every APISIX node before enabling this Plugin:

luarocks install lua-resty-saml 0.2.5

lua-resty-saml builds native xmlsec bindings, so the build environment must provide the OpenSSL, libxml2, and libxslt development files required by LuaRocks.

Before configuring the saml-auth Plugin, you need to register APISIX as a Service Provider with your Identity Provider. The exact steps depend on your IdP; the following example uses Keycloak.

Set Up Keycloak

1. Log in to the Keycloak Admin Console.
2. Create or select a realm (for example, myrealm).
3. Navigate to Clients and click Create client.
4. Set Client type to SAML.
5. Set Client ID to match the sp_issuer value you will use in the Plugin configuration (for example, https://sp.example.com).
6. Under Client > Settings:
   • Set Root URL to https://sp.example.com.
   • Set Valid redirect URIs to include the login_callback_uri (for example, https://sp.example.com/login/callback).
   • Set Master SAML Processing URL to https://sp.example.com/login/callback.
7. Under Client > Keys, upload the SP certificate (sp_cert) and enable Sign assertions.
8. Export the IdP metadata to obtain the idp_uri (SSO URL) and idp_cert (signing certificate).
9. Create users in Keycloak that will be allowed to authenticate.

Enable the Plugin

The following example creates a route protected by the saml-auth Plugin using a Keycloak IdP:

note

Replace the placeholder certificate and key values with your actual SP certificate, SP private key, and IdP certificate.

curl "http://127.0.0.1:9180/apisix/admin/routes/1" \
  -H "X-API-KEY: $ADMIN_API_KEY" \
  -X PUT \
  -d '{
    "uri": "/*",
    "plugins": {
      "saml-auth": {
        "sp_issuer": "https://sp.example.com",
        "idp_uri": "https://keycloak.example.com/realms/myrealm/protocol/saml",
        "idp_cert": "-----BEGIN CERTIFICATE-----\nMIIC...\n-----END CERTIFICATE-----",
        "login_callback_uri": "https://sp.example.com/login/callback",
        "logout_uri": "https://sp.example.com/logout",
        "logout_callback_uri": "https://sp.example.com/logout/callback",
        "logout_redirect_uri": "https://sp.example.com/logout/done",
        "sp_cert": "-----BEGIN CERTIFICATE-----\nMIIC...\n-----END CERTIFICATE-----",
        "sp_private_key": "-----BEGIN RSA PRIVATE KEY-----\nMIIE...\n-----END RSA PRIVATE KEY-----",
        "auth_protocol_binding_method": "HTTP-Redirect",
        "secret": "my-session-secret"
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "127.0.0.1:1980": 1
      }
    }
  }'

Disable the Plugin

To disable the saml-auth Plugin, remove it from the route configuration:

curl "http://127.0.0.1:9180/apisix/admin/routes/1" \
  -H "X-API-KEY: $ADMIN_API_KEY" \
  -X PUT \
  -d '{
    "uri": "/*",
    "plugins": {},
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "127.0.0.1:1980": 1
      }
    }
  }'