Simple SAML Proxy

A lightweight and easy-to-use SAML proxy that enables multi-tenant SSO capabilities for applications that only support single-tenant SSO.

What is Simple SAML Proxy?

Simple SAML Proxy is NOT a traditional request/response proxy that just forwards SAML messages. Instead, it's an intelligent intermediary that acts as:

• Identity Provider (IdP) to your Service Providers
• Service Provider (SP) to your Identity Providers

This dual-role pattern enables single-tenant applications to authenticate users from multiple Identity Providers through a single integration point.

Key Features

🚀 Zero Infrastructure Dependencies

• No database required
• No persistent cache or storage
• No configuration files
• Single binary deployment
• All configuration via environment variables

🏢 Multi-Identity Provider Support

• Connect multiple Identity Providers simultaneously
• User-friendly IdP selection interface
• Support for SP-initiated authentication flows

🔐 Enterprise Security

• Full XML digital signature validation
• Configurable Single Logout (SLO) support
• TLS/HTTPS deployment ready
• Certificate-based authentication

⚡ Production Ready

• Comprehensive test coverage
• Docker support with examples
• Integration testing with Keycloak
• Detailed monitoring and logging

Use Cases

Perfect for organizations that need to:

✅ Connect single-tenant applications to multiple Identity Providers
✅ Avoid complex identity federation systems
✅ Deploy quickly without database setup
✅ Provide users with IdP choice during authentication
✅ Maintain security with signature validation

Quick Start

Installation

# Install latest version
go install github.com/sters/simple-saml-proxy@latest

# Or download from releases
wget https://github.com/sters/simple-saml-proxy/releases/latest

Basic Configuration

Create your certificates:

# Generate private key
openssl genpkey -algorithm RSA -out proxy-private.key -pkcs8

# Generate certificate
openssl req -new -x509 -key proxy-private.key -out proxy-cert.crt -days 365

Set environment variables:

# Proxy configuration
export PROXY_ENTITY_ID="https://your-proxy.example.com"
export PROXY_PRIVATE_KEY_PATH="./proxy-private.key"
export PROXY_CERTIFICATE_PATH="./proxy-cert.crt"

# Identity Provider configuration
export IDP_0_ID="your-idp"
export IDP_0_ENTITY_ID="https://your-idp.example.com"
export IDP_0_SSO_URL="https://your-idp.example.com/sso"
export IDP_0_CERTIFICATE_PATH="./idp-cert.crt"

# Service Provider configuration  
export PROXY_ALLOWED_SP_0_ENTITY_ID="https://your-app.example.com"
export PROXY_ALLOWED_SP_0_ACS_URL="https://your-app.example.com/acs"

# Server configuration
export SERVER_LISTEN_ADDRESS=":8080"

Run the Proxy

simple-saml-proxy

Your proxy will be available at:

• Metadata URL: https://your-proxy.example.com/idp/metadata
• SSO URL: https://your-proxy.example.com/idp/sso
• ACS URL: https://your-proxy.example.com/sp/acs

Configuration Reference

Required Environment Variables

Variable	Description	Example
PROXY_ENTITY_ID	Proxy's SAML entity ID	https://proxy.example.com
PROXY_PRIVATE_KEY_PATH	Path to proxy private key	./certs/proxy.key
PROXY_CERTIFICATE_PATH	Path to proxy certificate	./certs/proxy.crt
IDP_0_ID	Identity Provider identifier	keycloak-main

Identity Provider Configuration

Configure multiple IdPs using indexed environment variables:

# First IdP
export IDP_0_ID="keycloak-main"
export IDP_0_ENTITY_ID="https://keycloak.example.com/realms/main"
export IDP_0_SSO_URL="https://keycloak.example.com/realms/main/protocol/saml"
export IDP_0_CERTIFICATE_PATH="./certs/keycloak.crt"
# Or use metadata URL instead
export IDP_0_METADATA_URL="https://keycloak.example.com/realms/main/protocol/saml/descriptor"

# Second IdP
export IDP_1_ID="azure-ad"
export IDP_1_METADATA_URL="https://login.microsoftonline.com/your-tenant/federationmetadata/2007-06/federationmetadata.xml"

Service Provider Configuration

Configure allowed SPs:

# First SP
export PROXY_ALLOWED_SP_0_ENTITY_ID="https://app1.example.com"
export PROXY_ALLOWED_SP_0_ACS_URL="https://app1.example.com/saml/acs"

# Second SP with metadata
export PROXY_ALLOWED_SP_1_ENTITY_ID="https://app2.example.com"  
export PROXY_ALLOWED_SP_1_METADATA_URL="https://app2.example.com/saml/metadata"

Optional Configuration

Variable	Default	Description
SERVER_LISTEN_ADDRESS	:8080	Server listen address
METADATA_MAX_RETRIES	5	Max metadata fetch retries
METADATA_INITIAL_DELAY	1s	Initial retry delay
PROXY_REQUIRE_SIGNED_LOGOUT_REQUESTS	false	Global SLO signature requirement

Endpoint Structure

The proxy organizes endpoints based on their role:

IdP Endpoints (for Service Providers)

• /idp/metadata - SAML metadata
• /idp/sso - Single Sign-On endpoint
• /idp/slo - Single Logout endpoint
• /idp/slo/response - Single Logout response endpoint

SP Endpoints (for Identity Providers)

• /sp/acs - Assertion Consumer Service
• /sp/sls - Single Logout Service
• /sp/idp_select - IdP selection page
• /sp/idp_selected - IdP selection handler

Notes:

• All path values must start with /
• Only paths are allowed, not full URLs
• The metadata endpoint is always available at /metadata for compatibility

Authentication Flows

SP-Initiated Flow

sequenceDiagram
    participant User
    participant SP as Service Provider
    participant Proxy as SAML Proxy
    participant IdP as Identity Provider

    User->>SP: Access protected resource
    SP->>Proxy: SAML AuthnRequest
    Proxy->>User: Show IdP selection page
    User->>Proxy: Select IdP
    Proxy->>IdP: New SAML AuthnRequest
    IdP->>User: Login page
    User->>IdP: Authenticate
    IdP->>Proxy: SAML Response
    Proxy->>SP: New SAML Response
    SP->>User: Access granted

Loading

Development

Build and Test

# Run the application
make run

# Run with arguments
make run ARGS="--help"

# Run tests
make test

# Generate coverage report
make cover

# Run linting
make lint

# Fix linting issues
make lint-fix

# Clean dependencies
make tidy

Docker Development

See the example/ directory for a complete development environment with:

• Keycloak IdP and SP setup
• Docker Compose configuration
• End-to-end testing with Playwright
• Integration test examples

# Start development environment
cd example
make dev-setup

# Run integration tests
make test

Production Deployment

Security Considerations

1. Always use HTTPS in production
2. Secure certificate storage - protect private keys
3. Configure signature validation for enhanced security
4. Regular certificate rotation
5. Monitor logs for authentication failures

Example Docker Deployment

version: '3.8'
services:
  saml-proxy:
    image: simple-saml-proxy:latest
    ports:
      - "8080:8080"
    environment:
      PROXY_ENTITY_ID: "https://proxy.yourcompany.com"
      PROXY_PRIVATE_KEY_PATH: "/certs/proxy.key"
      PROXY_CERTIFICATE_PATH: "/certs/proxy.crt"
      IDP_0_ID: "main-idp"
      IDP_0_METADATA_URL: "https://idp.yourcompany.com/metadata"
      PROXY_ALLOWED_SP_0_ENTITY_ID: "https://app.yourcompany.com"
      PROXY_ALLOWED_SP_0_ACS_URL: "https://app.yourcompany.com/saml/acs"
    volumes:
      - ./certs:/certs:ro
    restart: unless-stopped

Health Checks

The proxy provides health check endpoints:

• GET /ping - Basic health check
• GET /metadata - SAML metadata (validates configuration)

SAML 2.0 Compliance

Simple SAML Proxy implements core SAML 2.0 features:

Feature	Status	Notes
Web Browser SSO Profile	✅	SP-initiated flow support
HTTP-Redirect Binding	✅	For authentication requests
HTTP-POST Binding	✅	For SAML responses
XML Digital Signatures	✅	RSA-SHA256 with validation
Single Logout (SLO)	⚠️	Partial support with signature validation
Metadata Generation	✅	Available at /metadata
Multi-IdP Support	✅	Core feature

Troubleshooting

Common Issues

Certificate Errors

# Verify certificate format
openssl x509 -in proxy-cert.crt -text -noout

# Check private key
openssl rsa -in proxy-private.key -check

Configuration Issues

# Check metadata endpoint
curl https://your-proxy.example.com/metadata

# Verify environment variables
env | grep -E "(PROXY_|IDP_|SERVER_)"

Authentication Failures

• Check logs for detailed error messages
• Verify IdP and SP configurations
• Ensure certificates are valid and trusted
• Confirm URLs are accessible

Logging

Enable detailed logging:

export LOG_LEVEL=debug
simple-saml-proxy

Logs include:

• Authentication request processing
• SAML message validation
• Certificate verification
• Network communication

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests for new functionality
5. Run tests: make test
6. Run linting: make lint
7. Submit a pull request

See CLAUDE.md for development guidelines.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Support

• 📖 Documentation: See CLAUDE.md for development details
• 🐛 Issues: GitHub Issues
• 💬 Discussions: GitHub Discussions
• 📧 Security: Report security issues privately

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Made with ❤️ for the SAML community