presidio-hardened-flask

A hardened drop-in replacement for Flask that automatically applies production-grade security defaults (v0.2.0). Change one import line and your existing Flask app gets security headers, rate limiting, CSRF protection (no weak defaults), secret redaction (sink-enforced), input sanitization, and more.

v0.2.0 Security Updates

• Sink redaction now enforced at the logging sink (RedactingFilter on app.logger).
• CSRF no longer accepts the dangerous built-in "presidio-dev-key" fallback — requires a strong SECRET_KEY (raises clear error otherwise).
• pip-audit integrated in dev dependencies and CI.
• All major audit findings from third-party review remediated; docs (SECURITY, PRESIDIO-REQ, README) updated to match implemented behavior.

Quick Start

Install

pip install presidio-hardened-flask

Usage — Change One Import

Before (plain Flask):

from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route("/")
def index():
    return "Hello, world!"

After (presidio-hardened-flask):

from presidio_flask import Flask, jsonify, request

app = Flask(__name__)

@app.route("/")
def index():
    return "Hello, secure world!"

That's it. Your app now automatically receives:

Side-by-Side Comparison

Security Headers

Plain Flask returns no security headers by default:

HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8

presidio-hardened-flask adds them automatically:

HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
Referrer-Policy: strict-origin-when-cross-origin
Content-Security-Policy: default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'
Strict-Transport-Security: max-age=63072000; includeSubDomains; preload
Permissions-Policy: geolocation=(), camera=(), microphone=()
Cross-Origin-Opener-Policy: same-origin
Cross-Origin-Resource-Policy: same-origin

Rate Limiting

Plain Flask has no built-in rate limiting. A single client can hammer your API.

presidio-hardened-flask enforces per-IP rate limits with informative headers:

X-RateLimit-Limit: 60
X-RateLimit-Remaining: 57

When exceeded, returns 429 Too Many Requests with exponential backoff.

Secret Redaction

Plain Flask will happily log passwords and tokens in plain text:

app.logger.info("Request: %s", request.json)
# {"username": "alice", "password": "hunter2", "api_key": "sk-live-abc123"}

presidio-hardened-flask automatically redacts sensitive fields:

from presidio_flask import redact_dict
print(redact_dict({"password": "hunter2", "api_key": "sk-123"}))
# {"password": "***REDACTED***", "api_key": "***REDACTED***"}

CSRF Protection

Plain Flask has no CSRF protection.

presidio-hardened-flask uses a modern two-layer approach:

1. Sec-Fetch-Site header — blocks cross-origin mutating requests automatically
2. Token-based fallback — for older browsers or custom setups

from presidio_flask import generate_csrf_token

# In your template / API response:
token = generate_csrf_token()
# Include as X-CSRF-Token header or _csrf_token form field

Configuration

All features are enabled by default but fully configurable:

app = Flask(__name__)
app.config.update(
    # Rate limiting
    PRESIDIO_RATE_LIMIT=100,           # requests per window (default: 60)
    PRESIDIO_RATE_WINDOW=120,          # window in seconds (default: 60)
    PRESIDIO_RATE_LIMIT_ENABLED=True,  # disable entirely if False

    # CSRF
    PRESIDIO_CSRF_ENABLED=True,

    # Input sanitization
    PRESIDIO_SANITIZE_ENABLED=True,

    # Secret redaction
    PRESIDIO_REDACTION_ENABLED=True,

    # Security logging
    PRESIDIO_LOGGING_ENABLED=True,

    # CVE check on startup
    PRESIDIO_CVE_CHECK=True,

    # Custom security headers (merge with/override defaults)
    PRESIDIO_SECURITY_HEADERS={
        "X-Frame-Options": "SAMEORIGIN",
        "Content-Security-Policy": "default-src 'self'; img-src *",
    },
)

Development

# Clone and install
git clone https://github.com/presidio-v/presidio-hardened-flask.git
cd presidio-hardened-flask
uv venv .venv && source .venv/bin/activate
uv pip install -e ".[dev]"

# Run tests
pytest --cov=presidio_flask

# Lint and format
ruff format .
ruff check . --fix

License

MIT