Login.gov SAML 2.0 API

openapi: 3.1.0
info:
  title: Login.gov SAML 2.0 API
  version: '2026-01'
  description: |
    Login.gov also supports SAML 2.0 for relying parties that prefer enterprise federation
    semantics over OIDC. SAML endpoints are versioned by certificate year (the `2026` suffix
    corresponds to certificates valid through April 1, 2027). The persistent NameID format
    issues a per-RP UUID v4.

    The SSO endpoint accepts the HTTP-Redirect binding; SLO uses HTTP-POST. Login.gov's
    SAML certificates are published in the metadata endpoint and should be loaded
    dynamically so that annual rotations do not require code changes.
  contact:
    name: Login.gov Partner Support
    url: https://developers.login.gov
    email: partners@login.gov
  license:
    name: Public Domain (U.S. Government Work)
    url: https://www.usa.gov/government-works
servers:
- url: https://idp.int.identitysandbox.gov
  description: Sandbox (integration) environment
- url: https://secure.login.gov
  description: Production environment
tags:
- name: Metadata
  description: SAML 2.0 IdP metadata.
- name: Authentication
  description: SAML SSO request endpoint.
- name: Logout
  description: SAML Single Logout endpoint.
paths:
  /api/saml/metadata2026:
    get:
      tags:
      - Metadata
      summary: Get SAML 2.0 IdP Metadata
      operationId: getSamlMetadata
      description: Returns the SAML 2.0 IdP metadata XML including entity ID, SSO/SLO endpoints, signing certificate, and supported NameID formats.
      responses:
        '200':
          description: SAML metadata document.
          content:
            application/samlmetadata+xml:
              schema:
                type: string
                format: xml
            application/xml:
              schema:
                type: string
                format: xml
  /api/saml/auth2026:
    get:
      tags:
      - Authentication
      summary: Initiate SAML SSO (HTTP-Redirect)
      operationId: samlSso
      description: |
        Accepts a Base64-encoded, DEFLATE-compressed `SAMLRequest` via HTTP-Redirect.
        The user authenticates with Login.gov and the IdP responds with a signed SAML
        assertion POSTed to the SP's Assertion Consumer Service URL.
      parameters:
      - name: SAMLRequest
        in: query
        required: true
        description: Base64-encoded DEFLATE-compressed AuthnRequest.
        schema:
          type: string
      - name: RelayState
        in: query
        required: false
        description: Opaque value echoed back in the SAML response.
        schema:
          type: string
      - name: SigAlg
        in: query
        required: false
        description: Signature algorithm URI when the request is signed.
        schema:
          type: string
      - name: Signature
        in: query
        required: false
        description: Base64-encoded signature over the request.
        schema:
          type: string
      responses:
        '200':
          description: Login.gov sign-in UI is rendered to the end user.
        '302':
          description: Redirect to authentication challenge or to SP ACS with the signed SAML response.
  /api/saml/logout2026:
    post:
      tags:
      - Logout
      summary: SAML Single Logout (HTTP-POST)
      operationId: samlSlo
      description: Accepts a signed `LogoutRequest` from the SP and terminates the user's Login.gov session.
      requestBody:
        required: true
        content:
          application/x-www-form-urlencoded:
            schema:
              type: object
              required:
              - SAMLRequest
              properties:
                SAMLRequest:
                  type: string
                  description: Base64-encoded SAML LogoutRequest.
                RelayState:
                  type: string
      responses:
        '200':
          description: LogoutResponse posted back to the SP's SLO endpoint.
components:
  schemas:
    SamlAssertionAttributes:
      type: object
      description: Attributes returned in a Login.gov SAML assertion (attribute names follow Login.gov conventions, not OIDC claim names).
      properties:
        uuid:
          type: string
          description: Stable per-RP user identifier.
        email:
          type: string
        all_emails:
          type: string
        locale:
          type: string
        ial:
          type: string
        aal:
          type: string
        first_name:
          type: string
          description: Available at IAL2.
        last_name:
          type: string
          description: Available at IAL2.
        address1:
          type: string
        address2:
          type: string
        city:
          type: string
        state:
          type: string
        zipcode:
          type: string
        phone:
          type: string
        dob:
          type: string
          format: date
        ssn:
          type: string
          description: Social Security Number. Available at IAL2 only.
        verified_at:
          type: string
        x509_subject:
          type: string
        x509_issuer:
          type: string
        x509_presented:
          type: string