# SSO to legacy applications

OpenIAM **Access Gateway** (`rProxy`) is a secure reverse proxy that sits between users and protected applications. It intercepts incoming requests, enforces authentication and authorization policies, and ensures that only authenticated and entitled users can access platform resources. It improves security, reduces application-specific security work, and provides a single control point for auditing and monitoring.

Access Gateway is especially useful when applications do not support modern identity standards such as **SAML**, **OAuth 2.0**, or **OpenID Connect (OIDC)**. It also helps when you expose internal systems to external users or enforce consistent access policies across hybrid environments. Teams often deploy it during cloud migrations and identity modernization projects.

To enable SSO for these applications, Access Gateway provides these core capabilities:

* [Form Fill](/sso-to-legacy-applications/form-fill.md) — send a form post to a specified URL to automate sign-in.
* [Adding headers in request and/or response](/sso-to-legacy-applications/adding-headers-in-request-and-or-response.md) — set headers, cookies, and URL parameters.
* [URL Rewriting](/sso-to-legacy-applications/url-rewriting.md) — rewrite URLs so proxied applications work correctly.
* [Real example configuring rProxy to access legacy web-application](/sso-to-legacy-applications/real-example-configuring-rproxy-to-access-legacy-web-application.md) — review end-to-end configuration examples.


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