SAML 2.0 Integration

Security Assertion Markup Language (SAML) is an XML-based standard for exchanging authentication and authorization data between identity providers and service providers. ZITADEL supports SAML 2.0, enabling integration with enterprise applications and legacy systems.

Why use SAML?

SAML remains relevant for specific use cases: Legacy systems compatibility SAML has been in use since 2002 and is deeply integrated into many legacy systems and enterprise environments. Organizations with existing SAML infrastructure may prefer to continue using it to avoid costly and complex migrations. Enterprise use cases SAML is often favored in enterprise settings where detailed user attributes and complex authorization requirements are necessary. Its support for rich metadata and customizable assertions makes it suitable for intricate access control scenarios. Mature ecosystem The SAML ecosystem is mature, with extensive support from a wide range of enterprise applications and identity providers. This broad compatibility ensures that SAML can be used seamlessly across various platforms and services.

SAML Terminology

Understanding SAML requires familiarity with these key terms:

Term	Description
Service Provider (SP)	The application the user is trying to sign into
Identity Provider (IdP)	The centralized authentication service (ZITADEL)
SAML Request	XML message from SP to IdP requesting authentication
SAML Response	XML message from IdP to SP containing authentication assertions
Assertion	Signed statement about the user within the SAML response
Assertion Consumer Service (ACS)	SP endpoint that processes SAML responses
Attributes	User profile information included in the SAML response
Relay State	Parameter to maintain application state across authentication
SAML Trust	Configuration establishing trust between IdP and SP
Metadata	XML file containing configuration for IdP or SP
Entity ID	Unique identifier for the IdP or SP (also called Issuer)

SAML Authentication Flows

ZITADEL supports SP-initiated SAML flows:

SP-Initiated Flow

The user starts at the service provider, which sends a SAML request to ZITADEL. Flow steps:

User attempts to access protected resource at SP
SP generates SAML AuthnRequest
SP redirects user to ZITADEL SSO endpoint with SAML request
User authenticates at ZITADEL (if not already authenticated)
ZITADEL generates SAML Response with assertions
ZITADEL redirects user back to SP’s ACS with SAML response
SP validates SAML response and assertions
SP grants access to user

IdP-Initiated Flow

ZITADEL currently does not support IdP-initiated flows. All SAML authentications must be initiated from the service provider.

ZITADEL as SAML Identity Provider

SAML Metadata

ZITADEL provides SAML metadata at:

https://${CUSTOM_DOMAIN}/saml/v2/metadata

This metadata contains:

Entity ID (Issuer)
SSO endpoint URL
Signing certificate
Supported bindings
Supported NameID formats

Example metadata request:

curl -X GET "https://${CUSTOM_DOMAIN}/saml/v2/metadata"

Certificate Endpoint

Download ZITADEL’s SAML signing certificate:

https://${CUSTOM_DOMAIN}/saml/v2/certificate

This certificate is used to verify the signature on SAML responses.

SSO Endpoint

The Single Sign-On endpoint handles SAML authentication requests:

https://${CUSTOM_DOMAIN}/saml/v2/SSO

Supported bindings:

urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect
urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST

SAML Request Format

A SAML AuthnRequest contains:

<?xml version="1.0" encoding="utf-8"?>
<samlp:AuthnRequest
  xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
  ID="_8LjuzBEUQFYFWjL55"
  Version="2.0"
  IssueInstant="2024-06-11T04:13:52Z"
  Destination="https://${CUSTOM_DOMAIN}/saml/v2/SSO"
  AssertionConsumerServiceURL="https://yourapp.example.com/acs">
  <saml:Issuer
    xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
    https://yourapp.example.com/metadata
  </saml:Issuer>
  <!-- Signature element -->
</samlp:AuthnRequest>

Key elements:

Element	Description
`ID`	Unique identifier for this request
`IssueInstant`	Timestamp when request was created
`Destination`	ZITADEL’s SSO endpoint
`AssertionConsumerServiceURL`	Where ZITADEL should send the response
`Issuer`	Service provider’s entity ID
`Signature`	Digital signature of the request (optional)

HTTP-Redirect Binding

With HTTP-Redirect binding, the SAML request is base64-encoded and sent as a URL parameter:

GET /saml/v2/SSO?
  SAMLRequest=PHNhbWxwOkF1dGhuUmVxdWVzdC4uLg%3D%3D&
  RelayState=af0ifjsldkj&
  SigAlg=http%3A%2F%2Fwww.w3.org%2F2000%2F09%2Fxmldsig%23rsa-sha1&
  Signature=Base64EncodedSignature

HTTP-POST Binding

With HTTP-POST binding, the SAML request is sent in the request body:

<form method="post" action="https://${CUSTOM_DOMAIN}/saml/v2/SSO">
  <input type="hidden" name="SAMLRequest" value="Base64EncodedRequest" />
  <input type="hidden" name="RelayState" value="StateValue" />
  <input type="submit" value="Continue" />
</form>

SAML Response Format

ZITADEL returns a SAML Response containing user assertions:

<?xml version="1.0" encoding="utf-8"?>
<samlp:Response
  xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
  ID="_164ba12b-6711-40e0-8ddb-55aa810f1c92"
  InResponseTo="_8LjuzBEUQFYFWjL55"
  Version="2.0"
  IssueInstant="2024-06-11T04:17:41Z"
  Destination="https://yourapp.example.com/acs">
  <saml:Issuer
    xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
    https://${CUSTOM_DOMAIN}/saml/v2/metadata
  </saml:Issuer>
  <samlp:Status>
    <samlp:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success"/>
  </samlp:Status>
  <saml:Assertion
    xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion"
    Version="2.0"
    ID="_6fbdb616-b77f-46af-9554-989c8b89eeda"
    IssueInstant="2024-06-11T04:17:41Z">
    <saml:Issuer>https://${CUSTOM_DOMAIN}/saml/v2/metadata</saml:Issuer>
    <!-- Signature element -->
    <saml:Subject>
      <saml:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress">
        [email protected]
      </saml:NameID>
      <saml:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
        <saml:SubjectConfirmationData
          NotOnOrAfter="2024-06-11T04:22:41Z"
          Recipient="https://yourapp.example.com/acs"
          InResponseTo="_8LjuzBEUQFYFWjL55"/>
      </saml:SubjectConfirmation>
    </saml:Subject>
    <saml:Conditions
      NotBefore="2024-06-11T04:17:41Z"
      NotOnOrAfter="2024-06-11T04:22:41Z">
      <saml:AudienceRestriction>
        <saml:Audience>https://yourapp.example.com/metadata</saml:Audience>
      </saml:AudienceRestriction>
    </saml:Conditions>
    <saml:AuthnStatement
      AuthnInstant="2024-06-11T04:17:41Z"
      SessionIndex="_6fbdb616-b77f-46af-9554-989c8b89eeda">
      <saml:AuthnContext>
        <saml:AuthnContextClassRef>
          urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport
        </saml:AuthnContextClassRef>
      </saml:AuthnContext>
    </saml:AuthnStatement>
    <saml:AttributeStatement>
      <saml:Attribute Name="Email">
        <saml:AttributeValue>[email protected]</saml:AttributeValue>
      </saml:Attribute>
      <saml:Attribute Name="FirstName">
        <saml:AttributeValue>John</saml:AttributeValue>
      </saml:Attribute>
      <saml:Attribute Name="SurName">
        <saml:AttributeValue>Doe</saml:AttributeValue>
      </saml:Attribute>
      <saml:Attribute Name="UserID">
        <saml:AttributeValue>260242264868201995</saml:AttributeValue>
      </saml:Attribute>
    </saml:AttributeStatement>
  </saml:Assertion>
</samlp:Response>

Key elements:

Element	Description
`InResponseTo`	ID of the SAML request being responded to
`Status`	Success or error status
`Assertion`	Signed statement about the authenticated user
`Subject`	User identifier (NameID)
`Conditions`	Time window and audience restrictions
`AuthnStatement`	Authentication method and time
`AttributeStatement`	User attributes (profile data)

Standard Attributes

ZITADEL includes these standard attributes in SAML responses:

Attribute Name	Description	Example
`UserID`	ZITADEL user ID	`260242264868201995`
`UserName`	Username	`[email protected]`
`Email`	Email address	`[email protected]`
`FirstName`	Given name	`John`
`SurName`	Family name	`Doe`
`FullName`	Complete name	`John Doe`

Custom Attributes

You can add custom attributes to SAML responses using ZITADEL Actions:

// Action to add custom SAML attributes
function addCustomAttributes(ctx, api) {
  api.v1.claims.setClaim('Department', ctx.user.metadata.department);
  api.v1.claims.setClaim('EmployeeID', ctx.user.metadata.employeeId);
  api.v1.claims.setClaim('Roles', ctx.user.grants.map(g => g.roles).flat());
}

See the Actions documentation for more details on customizing SAML responses.

Configuring a SAML Application

SAML Identity Brokering

ZITADEL can act as both an identity provider and integrate with external SAML identity providers for identity brokering: How it works:

User attempts to access a service (SP) protected by ZITADEL
ZITADEL redirects user to external SAML IdP for authentication
User authenticates with external SAML IdP
External IdP returns SAML assertion to ZITADEL
ZITADEL processes the assertion and creates its own SAML assertion
ZITADEL sends final SAML assertion to the service provider
User gains access to the service

This enables organizations to integrate ZITADEL with existing identity providers while providing SAML SSO to applications.

Validating SAML Responses

Service providers must validate SAML responses to ensure security:

Signature Validation

Extract the signature from the SAML response or assertion
Obtain ZITADEL’s public key from the metadata or certificate endpoint
Verify the XML signature using the public key
Ensure the signature covers the entire assertion

Assertion Validation

Validate these elements in the SAML assertion:

Element	Validation
`Issuer`	Must match ZITADEL’s entity ID
`InResponseTo`	Must match the original request ID
`Recipient`	Must match your ACS URL
`Audience`	Must match your entity ID
`NotBefore`	Current time must be after this timestamp
`NotOnOrAfter`	Current time must be before this timestamp
`SubjectConfirmation`	Must be `bearer` method

Status Code Validation

Check the status code in the SAML response:

<samlp:Status>
  <samlp:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success"/>
</samlp:Status>

Only process assertions if the status is Success.

Security Best Practices

Always validate signatures: Verify XML signatures on SAML responses and assertions
Use canonicalized XML: Normalize XML before signature verification to prevent manipulation
Validate XML schema: Ensure only expected XML formats are accepted
Enforce time windows: Respect NotBefore and NotOnOrAfter conditions
Validate all parties: Check Issuer, Recipient, and Audience values
Prevent replay attacks: Track processed assertion IDs and reject duplicates
Use HTTPS exclusively: Never exchange SAML messages over unencrypted connections
Limit XML parser features: Disable external entity resolution to prevent XXE attacks
Validate metadata: Verify metadata sources before importing
Monitor for anomalies: Track authentication patterns and alert on suspicious activity

Troubleshooting

Common Issues

Signature validation fails

Ensure you’re using ZITADEL’s current signing certificate
Verify the certificate hasn’t expired
Check that XML canonicalization is correct

Audience restriction error

Verify your SP’s entity ID matches the Audience value
Check for case sensitivity and trailing slashes

Assertion expired

Check server time synchronization (NTP)
Verify time zone settings
Consider clock skew tolerance in your SP configuration

Invalid destination

Ensure the ACS URL in the request matches your registered ACS URL
Check for HTTP vs HTTPS mismatches

Metadata import fails

Validate XML syntax
Ensure metadata conforms to SAML 2.0 specification
Check that required elements are present

Testing SAML Integration

Using ZITADEL as IdP

Create a SAML application in ZITADEL
Configure your service provider with ZITADEL’s metadata
Create test users in ZITADEL
Initiate authentication from the service provider
Verify successful authentication and attribute mapping

Example Service Provider Setup

See the ZITADEL Python SAML SP example for a reference implementation.

Browser Tools

Use browser extensions to inspect SAML messages:

SAML-tracer (Firefox/Chrome)
SAML Chrome Panel

These tools decode and display SAML requests and responses for debugging.

When to Use SAML vs OIDC

Use SAML when:

Integrating with enterprise applications that require SAML
Working with legacy systems built before OIDC adoption
Organization policy mandates SAML
Need for complex attribute statements and authorization decisions

Use OIDC when:

Building new applications
Developing mobile or single-page applications
Prefer JSON over XML
Want simpler implementation and debugging
Need modern features like PKCE and dynamic client registration

OIDC is generally recommended for new implementations. Use SAML when required by existing infrastructure or application requirements.

Overview

Core Concepts

Deployment

User Management

Authentication

Integration

SAML 2.0 Integration

Why use SAML?

SAML Terminology

SAML Authentication Flows

SP-Initiated Flow

IdP-Initiated Flow

ZITADEL as SAML Identity Provider

SAML Metadata

Certificate Endpoint

SSO Endpoint

SAML Request Format

HTTP-Redirect Binding

HTTP-POST Binding

SAML Response Format

Standard Attributes

Custom Attributes

Configuring a SAML Application

SAML Identity Brokering

Validating SAML Responses

Signature Validation

Assertion Validation

Status Code Validation

Security Best Practices

Troubleshooting

Common Issues

Testing SAML Integration

Using ZITADEL as IdP

Example Service Provider Setup

Browser Tools

When to Use SAML vs OIDC

Resources

Build docs developers (and LLMs) love

Overview

Core Concepts

Deployment

User Management

Authentication

Integration

​Why use SAML?

​SAML Terminology

​SAML Authentication Flows

​SP-Initiated Flow

​IdP-Initiated Flow

​ZITADEL as SAML Identity Provider

​SAML Metadata

​Certificate Endpoint

​SSO Endpoint

​SAML Request Format

​HTTP-Redirect Binding

​HTTP-POST Binding

​SAML Response Format

​Standard Attributes

​Custom Attributes

​Configuring a SAML Application

​SAML Identity Brokering

​Validating SAML Responses

​Signature Validation

​Assertion Validation

​Status Code Validation

​Security Best Practices

​Troubleshooting

​Common Issues

​Testing SAML Integration

​Using ZITADEL as IdP

​Example Service Provider Setup

​Browser Tools

​When to Use SAML vs OIDC

​Resources

Build docs developers (and LLMs) love

Why use SAML?

SAML Terminology

SAML Authentication Flows

SP-Initiated Flow

IdP-Initiated Flow

ZITADEL as SAML Identity Provider

SAML Metadata

Certificate Endpoint

SSO Endpoint

SAML Request Format

HTTP-Redirect Binding

HTTP-POST Binding

SAML Response Format

Standard Attributes

Custom Attributes

Configuring a SAML Application

SAML Identity Brokering

Validating SAML Responses

Signature Validation

Assertion Validation

Status Code Validation

Security Best Practices

Troubleshooting

Common Issues

Testing SAML Integration

Using ZITADEL as IdP

Example Service Provider Setup

Browser Tools

When to Use SAML vs OIDC

Resources