Add bearer token authentication support to DEEPaaS API

[Copilot]

This PR implements bearer token authentication for DEEPaaS API endpoints to address cases where fine-grained authentication is not needed but API access control is required.

Overview

The implementation adds optional bearer token authentication that can be enabled via configuration. When enabled, protected endpoints require a valid Authorization: Bearer <token> header. The feature is backward compatible - authentication is disabled by default and existing deployments continue to work unchanged.

Key Features

🔐 Security Implementation

• Uses FastAPI's built-in HTTPBearer security scheme following RFC 6750 standards
• Protects model endpoints (/v2/models/) and predict endpoints (/v2/models/{model}/predict)
• Public endpoints (root / and version /v2/) remain accessible without authentication
• Proper HTTP 401 responses with WWW-Authenticate: Bearer headers for unauthorized requests

⚙️ Configuration

The bearer token is configured via the new --auth-bearer-token option:

# Command line
deepaas-run --auth-bearer-token my-secret-token

# Environment variable
export DEEPAAS_AUTH_BEARER_TOKEN=my-secret-token
deepaas-run

# Configuration file
[DEFAULT]
auth_bearer_token = my-secret-token

🔌 API Usage

When authentication is enabled, API clients must include the bearer token:

# Models endpoint
curl -H "Authorization: Bearer my-secret-token" \
     http://localhost:5000/v2/models/

# Predict endpoint
curl -H "Authorization: Bearer my-secret-token" \
     -X POST -F "[email protected]" \
     http://localhost:5000/v2/models/my-model/predict

Implementation Details

New Files

• deepaas/auth.py - Authentication module with token validation logic (using Sphinx docstring format)
• deepaas/tests/test_auth.py - Unit tests for authentication functionality
• deepaas/tests/test_e2e_auth.py - End-to-end API integration tests
• doc/source/user/authentication.rst - Documentation with usage examples and security considerations (reStructuredText format)

Modified Files

• deepaas/config.py - Added auth_bearer_token configuration option (marked as secret)
• deepaas/api/v2/models.py - Added authentication dependency to model endpoints
• deepaas/api/v2/predict.py - Added authentication dependency to predict endpoints
• doc/source/user/index.rst - Added authentication documentation to user documentation index

Behavioral Changes

• When auth_bearer_token is not set (default): All endpoints work as before - no authentication required
• When auth_bearer_token is set: Model and predict endpoints require valid bearer token, other endpoints remain public
• Invalid/missing tokens: Return HTTP 401 with appropriate error messages

Testing

Added comprehensive test coverage with 18 new tests:

• Unit tests for authentication logic (token validation, error handling)
• Integration tests with FastAPI test client
• End-to-end API tests covering all authentication scenarios
• All existing tests continue to pass (36 total tests)

Security Considerations

• Token is stored as a secret configuration option
• No performance overhead when authentication is disabled
• Follows security best practices with proper HTTP status codes and headers
• Documentation includes security recommendations for production use

This implementation provides a simple but effective authentication mechanism for deployments that need basic API access control without the complexity of fine-grained authorization systems.

Fixes #151

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add support for bearer authentication</issue_title>
<issue_description>It would be useful to be able to setup a bearer token system/API keys for authentication, for cases where we do not need fine-grained auth.</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #151

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[alvarolopez]

@copilot please address the changes, and take into account that we use rST for docs.

[alvarolopez]

@copilot please use sphinx syntax here

[Copilot]

Updated the docstring to use proper Sphinx syntax with :param:, :type:, :returns:, :rtype:, and :raises: format in commit 288b790.

[Copilot]

@copilot please address the changes, and take into account that we use rST for docs.

Addressed both changes:

1. Fixed Sphinx docstring format in deepaas/auth.py
2. Converted documentation from Markdown to reStructuredText format and moved to doc/source/user/authentication.rst

The documentation is now properly integrated into the Sphinx documentation structure and follows project conventions. Commit 288b790.

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud